# FINAL

Report on Carcinogens Background Document for



# Lead and Lead Compounds

May 8, 2003

Prepared for the: U.S. Department of Health and Human Services
Public Health Service National Toxicology Program Research Triangle Park, NC 27709

Prepared by: Technology Planning and Management Corporation Canterbury Hall, Suite 310 4815 Emperor Blvd Durham, NC 27703 Contract Number N01-ES-8542105/08/03 RoC Background Document for Lead and Lead Compounds

i 

### FOREWORD

The Report on Carcinogens (RoC) is prepared in response to Section 301 of the Public
Health Service Act as amended. The RoC contains a list of all substa nces (i) that either are known to be human carcinogens or may reasonably be anticipated to be human carcinogens and (ii) to which a significant number of persons residing in the United States are exposed. The Secretary, Departme nt of Health and Human Services, has delegated responsibility for preparation of the RoC to the National Toxicology Program, which prepares the Report with assistance from other Federal health and regulatory agencies and nongovernmental institutions.

Nominations for listing in or delisting from the RoC are reviewed by a formal process that includes a multi-phased scientific peer review and several opportunities for public comment. The review groups evaluate each nom ination according to specific RoC listing criteria. This Background Document was prep ared to assist in the review of the nomination of lead and lead compounds. The scientific information in this document comes from publicly available peer-reviewe d sources. Any interpretive conclusions, comments, or statistical calculations made by the authors of this document that are not contained in the original source are identifie d in brackets [ ]. If any members of the scientific peer review groups feel that this Background Document does not adequately capture and present the relevant informati on, they will be asked to write a commentary for this Background Document that will be included as an addendum to the document. In addition, a meeting summary th at contains a brief discus sion of each review group’s review and recommendation for the nomination will be added to the Background Document, also as an addendum.

A detailed description of the RoC nomination re view process and a list of all nominations under consideration for listing in or delisti ng from the RoC can be obtained by accessing the NTP Home Page at http://ntp-server.niehs.nih.gov

. The most recent RoC, the Ninth Edition, was published in May 2000 and may be obtained by contacting the National
Institute for Environmental Health Sciences Environmental Health Information Service at http://ehis.niehs.nih.gov (800-315-3010).05/08/03 RoC Background Document for Lead and Lead Compounds

ii05/08/03 RoC Background Document for Lead and Lead Compounds

iii 

## Executive Summary

Introduction Lead can be used in its pure form as a me tal, alloyed with other metals, or used in chemical compounds. Inorganic lead compounds us ually consist of lead in the divalent state. Organic lead compounds were used in automotive gasoline additives in the United
States until 1996. Lead and l ead compounds were nominated by the National Institute of
Environmental Health Sciences based on th e 1987 finding by the International Agency for Research on Cancer (IARC) of sufficient evidence of carcinogenicity in experimental animals to identify lead and inorganic l ead compounds as possibly carcinogenic to humans (Group 2B) and the subsequent publication of additional human and animal studies of lead and lead compounds.

Human Exposure

Use . In worldwide metal use, lead ranks be hind only iron, copper, aluminum, and zinc. Its greatest use is in lead- acid storage batteries found in motor vehicles and general industry. Other common uses of lead meta l include ammunition, cable covering, piping, brass and bronze, bearing metals for machiner y, and sheet lead. Lead oxides are found in paint, glass, and ceramics. Organic lead was used in motor vehicle fuels as an anti-knock additive in the United States until 1996, wh en it was banned by the U.S. Environmental Protection Agency, following a phase-out initia ted in the 1970s. Orga nic lead still is permitted for use in gasoline for aircraft and in fuels for racing vehicles and for non-road vehicles such as farm machinery, mari ne vessels, construction equipment, and recreational vehicles. Despite re ductions in some lead applicat ions and the legislated end to use of lead as a gasoline additive, the ove rall consumption of lead is growing, mainly due to increased production of lead-acid batteries.

Production. Lead is refined from mined ore. Lead or e occurs most frequently in the form of lead sulfide, also known as galena. As of 2000, 19 mines, employing approximately 1,000 workers, produced the vast majority of le ad in the United States. Mined lead ore first is crushed and ground; th en the various minerals are se parated, resulting in a lead concentrate, which is shipped to a primary sme lter for refining. At a primary smelter, lead concentrates are sintered, then roasted and subj ected to a series of refining steps, resulting in lead metal that is 99.99% pure. In 2001, two primary lead smelter-refineries were operating, employing a total of approximately 400 people. Secondary smelters (recycling smelters) use scrap lead, mainly from used lead-acid batteries, as their supply. As of 2001, 26 secondary lead smelters were opera ting within the United States, employing approximately 1,600 workers. In 2001, the United States produced 1,375,000 tons of lead, used 1,687,000 tons of lead, an d recycled 1,099,000 tons of lead.

Environmental exposure . Environmental exposure to lead results in absorption of lead into the body via inhalation (approximately 30% to 50% absorbed into the bloodstream), via ingestion (approximately 8% to 15% abso rbed into the bloodstream) and, to a limited extent, through the skin. Air lead concentrations may be > 10 μ g/m 3 near industrial sources such as smelters. A 1991 survey of l ead levels in U.S. urban air revealed a maximum quarterly mean concentration of approximately 0.08 μ g/m 3 . Rural05/08/03 RoC Background Document for Lead and Lead Compounds

iv concentrations typically are lower, bri nging the estimated U.S. mean air lead

concentration to 0.04 μ g/m 3 in 1995. The average intake of lead by inhalation is estimated

at 2 μ g/day for an adult living in a U.S. urba n setting. Lead concentrations in U.S. drinking water generally are below 5 μ g/L. Lead also is found in food, cigarette smoke, and alcoholic beverages. In 1990, the estimated daily intake of lead from consumption of food, water, and beverages was approximately 4 μ g/day for children 2 years of age and younger, 6 to 9 μ g/day for children aged 14 to 16, 6 to 9 μ g/day for adults aged 25 to 30,

and 2 to 8 μ g/day for adults aged 60 to 65. The mo st common source of environmental lead exposure for young children is direct inge stion of paint chips and leaded dusts and soils released from aging painted surfaces, wh ich can contribute an ad ditional intake of 5

μ g/day for a toddler engaging in normal hand-to-mouth activity.

Occupational exposure. The most common route of occupa tional exposure to lead is
inhalation of lead fumes or leaded dusts in air and absorption of lead through the respiratory system. Lead also may be ingested and absorbed in the gastrointestinal tract. The National Institute for Occupational Safety and Health has estimated that more than three million Americans potentially are occupa tionally exposed to some form of lead.

Many occupations have the potential for high exposure to lead. Occupations having frequent high exposure to lead include ba ttery-production workers, battery-recycling workers, foundry workers, lead chemical work ers, lead smelter and refinery workers, leaded-glass workers, pigment workers, and radiator-repair workers. Occupations with moderate frequency of high exposures includ e firing-range instructors, house renovators, lead miners, newspaper printers, plastics work ers, rubber workers, and steel welders and cutters. Occupations with low frequency of high exposure include automobile-repairworkers, cable-production workers, construction workers, demolition workers, firingrange participants, flame-solder workers, plumbers and pipe fitters, pottery-glaze producers, ship-repair workers, and stained-glass producers. M ean lead air concentrations in U.S. industries, as monitored by the O ccupational Safety and Health Administration, ranged from 165 μ g/m 3 (secondary smelters) to 200 μ g/m 3 (storage-battery plants and brass, bronze, and copper foundries).

Human Cancer Studies IARC reviewed lead and lead compounds in 1987 and concluded that the evidence available at that time, which was very lim ited, was inadequate to demonstrate human carcinogenicity. The number of epidemiologi c studies on the potential role of lead exposure in cancer has expanded since th e last IARC update; 17 case-control and 17 cohort studies have been published, as well as updates on previously studied populations and meta-analyses. Steenland and Boffetta (200 0) calculated a fixed-e ffects rate ratio of 1.04 (95% confidence interval [CI] = 1.00 to 1.09) for all cancers combined (N = 1,911) based on eight cohort studies of highly exposed workers.

Lung cancer. Meta-analyses performed since th e IARC review have reported significantly elevated relativ e risks (RRs) for lung cancer and lead exposure. Fu and Boffetta calculated RRs of 1.24 (95% CI = 1.16 to 1.33) based on 15 studies and 1.42 (95% CI = 1.05 to 1.92) based only on studies of battery and smelter workers, who were05/08/03 RoC Background Document for Lead and Lead Compounds

v considered to have the highest exposure. St eenland and Boffetta ( 2000) calculated an RR of 1.30 (95% CI = 1.15 to 1.46; 675 lung-cancer deaths) based on eight cohort studies in which lead was the predominant exposure. In Section 3.3.1 of this background document, 21 lead-exposed populations are evaluated; 15 of the 18 populations included in at least one cohort study had elevated risks of lung can cer, eight of which were statistically significant. Two of the three case-control st udies of populations not included in cohort studies also reported weak associations between lead expsoure and lung cancer. Population-based cohort studies of environmen tal exposure to lead also have reported positive associations between lung cancer and blood lead levels. The addition of one environmental cohort study to the Steenland a nd Boffetta (2000) meta-analysis yielded an RR of 1.32 (95% CI = 1.16 to 1.50). Confoundi ng by smoking or other occupational exposures, particularly to arseni c, may be partially responsible for the elevated risks seen in these studies. However, el evated risks also were obser ved in population studies that adjusted for cigarette smoking.

Stomach and general digestive cancer. Meta-analyses conducted since the 1987 IARC review have reported elevated risks for st omach cancer with lead exposure; Fu and Boffetta (1995) reported an RR of 1.33 (95% CI = 1.18 to 1.49) for lead exposure based on ten studies and an RR of 1.50 (95% CI = 1.23 to 1.83) for battery or smelter workers only, and Steenland and Boffetta (2000) repor ted an RR of 1.34 (95% CI = 1.14 to 1.57). In Section 3.2, 21 studies are evaluated, appr oximately half of which reported a positive association between lead exposure and stomach cancer.

Kidney cancer. Meta-analyses for kidney cancer we re based on fewer studies and fewer cases or deaths among exposed individuals. Fu and Boffetta (1995) calculated an RR of 1.19 (95% CI = 0.96 to 1.48) based on five studies, and Steenland and Boffetta (2002) calculated an RR of 1.01 (95% CI = 0.72 to 1.42) based on seven studies. For the review in Section 3.3.3 of this document, Steen land and Simonsen calculated an RR of 1.22 (95% CI = 0.93 to 1.59) based on the same se ven studies plus a recently published casecontrol study; because the recent study was la rge, it had a substantial effect on the RR. The low incidence of kidney cancer, resul ting in a small number of cases, limits the evaluation of carcinogenicity. Of the four studi es reviewed in Section 3.3.3 that had more than five cases in lead-exposed subjects, three reported a positive association between lead exposure and kidney cancer.

Bladder cancer. Fu and Boffetta (1995) reported an RR of bladder cancer from lead exposure of 1.41 (95% CI = 1.16 to 1.71) ba sed on five studies. Of seven studies reviewed in Section 3.3.4, six reported a positive associati on between lead exposure and
bladder cancer.

Other cancers. Other cancers with evidence linking them to lead exposure include
cancers of the brain and centr al nervous system, liver, co lon, and rectum, among which the evidence is strongest fo r brain and central nervous sy stem cancers. The results of studies on paternal lead exposure and ch ildhood cancer are conflic ting and difficult to
evaluate because of the limited number of studies and small sample sizes.05/08/03 RoC Background Document for Lead and Lead Compounds

vi Summary . Overall, the evidence is consistent with the hypothesis that lead is carcinogenic to humans. This evidence is strongest for lung cancer, for which a largely consistent
association has been demons trated with occupations a nd industries entailing lead exposure, as well as with indices of indivi dual lead exposure, incl uding job history and biological monitoring of occupationally exposed and general populations. Evidence also suggests an association between lead and stomach cancer.

Where exposure-response assessment was attemp ted, the strongest a ssociation with lung cancer usually was seen in the highest exposure group, but a monotonic increase with duration, intensity, or overall amount of exposure was not always observed. Here, interpretation again is complicated by the ge neral lack of adequate statistical power to evaluate multiple exposure levels while controlling for smoking, age, gender, and other potential confounders or effect modifiers. Also, workers who experience acute lead toxicity tend to drop out of the exposed worker population, which could lead to
underestimation of the associa tion between lead and cancer.

The observed associations, while consistent , generally are weak. The crude exposure measures used by most studies, such as tr eating whole plants or jobs as uniformly exposed, may have contributed to the modest size of most risk estimates. Confounding by lifestyle exposures, such as smoking for l ung cancer or diet for stomach cancer, or by concomitant occupational exposures, such as arsenic, may partially explain these small associations. However, associations were al so observed in studies that adjusted for potential lifestyle confounders or that were conducted in populations without systematic occupational exposures other than lead. T hus, confounding may not entirely account for
the increase in cancer risk associ ated with lead exposure.

Studies in Experimental Animals Lead acetate (soluble), lead subacetate (solub le), and lead phosphate (insoluble) were found to be carcinogenic in rats and/or mi ce, inducing tumors of the kidney (adenoma and adenocarcinoma) and, in some studies, increased incidences of cerebral glioma and lung adenoma. Renal tumors were observed in male and female rats and mice and were not always accompanied by chronic lead-induc ed nephropathy. The studies used a variety of exposure routes, includi ng oral, subcutaneous, intramuscular, transdermal, transplacental, and translactational; however , no inhalation studies were reported. Many of the studies focused on kidney toxicity a nd carcinogenicity, and thus did not include complete histopathological exams. However, the few studies that did examine other
tissues found little evidence that lead induced tumors. Lead subacetate co-administered with 2-acetylaminofluorene was reported to enhance liver and kidne y tumorigenicity in one study but not in two others and was shown to promote renal tumors in Wistar rats
administered N -ethyl- N -hydroxyethylnitrosamine. In other studies, lead ac etate increased the incidence of viral-induced lymphocytic leukemia in mice and was co-carcinogenic
when administered with N -(4'-fluoro-4-biphenyl)acetamide to F344 rats, but lead acetate did not increase tumor incidences in Spra gue-Dawley rats when co-administered with ethyl urea and sodium nitrite.05/08/03 RoC Background Document for Lead and Lead Compounds

vii Genotoxicity
Lead induced chromosomal aberrations in most studies in plants and in mammals (in

vitro and in vivo ) and DNA damage and fragmentation in mammals ( in vivo ; conflicting
results were observed in in vitro studies) and cell-free systems (in the presence of hydrogen peroxide) and inhibi ted DNA and RNA polymerase in cell-free systems and mammalian cells ( in vitro ). Conflicting results were observed for sister chromatid exchange and micronucleus i nduction in mammalian studies ( in vitro and in vivo ). Lead was not mutagenic in bacteria, and conflic ting results were observed in mammalian in

vitro systems. Conflicting results may reflect di fferences in the model systems employed, the end points used to determine genotoxi city, and the lead compounds employed. In studies of humans occupationally exposed to le ad, there is evidence to suggest that lead damages chromosomes or DNA; most studies were positive for induction of micronuclei, chromosomal aberrations, and DNA damage. St udies on sister chromatid exchange and studies in humans exposed environmentally to lead gave conflicti ng results. Studies in humans are sometimes difficult to evaluate, b ecause little informati on is given on how the populations were selected for study and b ecause of potential exposure to compounds from occupational or environmental sources that may act in conjunction with lead to increase its genotoxic potentia l. Likewise, personal habits such as smoking and alcohol consumption affect the genotoxic propertie s of various compounds, including lead. However, many of the more recent studies e ither controlled for smoking or reported an exposure-response relationship, suggesting that the genotoxic effects were due to lead exposure. Although lead(II) forms stable complexes with the nitrogenous bases and phosphate groups of purified DNA, it is unlik ely that lead compounds are directly genotoxic. However, several mechanisms exist by which lead compounds could indirectly alter DNA replication, fidelity, and repair, resulti ng in genotoxicity.

Other Relevant Data Absorption, distribution, and excretion. Lead absorption in humans and laboratory animals is affected by age, the chemical form of lead, and minerals in the diet (e.g., iron, calcium, and zinc). Gastrointestinal absorption declines with age, with children absorbing lead to a greater extent th an adults. Dietary deficienci es in iron, calcium, and zinc increase lead absorption and retention, wh ereas a high-protein diet appears to reduce absorption. After absorption, lead is distributed to blood plas ma, nervous system, and soft tissues. It subsequently is redistributed a nd accumulates in bone; approximately 75% to 90% of the lead body burden is found in bones and teeth.

Toxicity . The toxic effects of lead include neurotoxicity and developmental, reproductive, and cardiovascular effects. Lead is a poten t neurotoxin affecting the central nervous system (CNS) and the peripheral nervous sy stem (PNS), and high levels of exposure result in profound cognitive impairments. Exposur e of children to lower levels of lead has been associated with impairment of ne urocognitive and behavioral development, including impairment of attention and hearing.

Potential mechanisms of carcinogenicity . The mechanisms leading to the carcinogenic
effects of lead are not understood. Lead compounds do not appear to be directly genotoxic but may cause genetic damage through several indirect mechanisms. These include inhibition of DNA synthe sis and repair, oxidative da mage, and interaction with05/08/03 RoC Background Document for Lead and Lead Compounds

viii DNA-binding proteins and tumor-suppressor pr oteins. Interference with DNA synthesis and repair has been suggested as one possi ble explanation for the genotoxic and comutagenic properties of lead. It has been sugge sted that increased ce ll proliferation may play a role in lead’s induction of renal cance r in rodents; however, the mechanisms have not been established. Although exposure to lead also induces cell pr oliferation in the liver, the data suggest that the liver is not as susceptible as the kidneys to the carcinogenicity of this effect. No studies have associated live r tumors with lead exposure,
and several studies have shown that lead -induced proliferative mitogenesis does not promote the formation of liver foci or nodul es from initiated hepatocytes, as observed during regenerative mitogenesi s. An association of renal adenocarcinoma with cystic nephropathy has been suggested but is uncertain.05/08/03 RoC Background Document for Lead and Lead Compounds

ix 

### CONTRIBUTORS

NIEHS/NTP Staff

C. W. Jameson, Ph.D. Head, Report on Carcinogens, Environmental Toxicology Program, NIEHS

Ruth M. Lunn, Dr. P.H. Report on Carcinogens Group, Environmental Toxicology Program, NIEHS

Shawn Jeter, B.S. Report on Carcinogens Group, Environmental Toxicology Program, NIEHS

AnnaLee Sabella Report on Carcinogens Group, Environmental Toxicology Program, NIEHS

Support to the National Toxicology Program for the preparation of this background

document was provided by Technology Planni ng and Management Corporation through NIEHS Contract Number NO1-ES-85421

Ronald Thomas, Ph.D., Pr incipal Investigator

Sanford Garner, Ph.D., Co-P rincipal Investigator

Stanley Atwood, M.S.

Ashlee Duncan, M.S.

Susan Goldhaber, M.S.

Ibrahim Raphiou, Ph.D.

Support staff

Angie Fralick, B.S.

Tracy Saunders, B.S.

Consultants

Susan Dakin, Ph.D., Independent Consultant, Durham, NC

David Fleming, Ph.D., Department of P hysics, Mount Allison University, New Brunswick, Canada05/08/03 RoC Background Document for Lead and Lead Compounds

x Brian Gulson, Ph.D., Graduate School of the Environment, Macquarie University, Sydney, Australia

Ellen Silbergeld, Ph.D., Division of Environm ental Health Engineering, Department of Environmental Health Sciences, John s Hopkins University, Baltimore, MD

Neal Simonsen, Ph.D., Department of Public Health and Preventive Medicine, Louisiana State University Health Scien ces Center, New Orleans, LA

Kyle Steenland, Ph.D., National Institute for Oc cupational Safety and Health, Cincinnati,

OH

Marshall Williams, Ph.D., Department of Molecular Virology, Immunology and Medical Genetics, Ohio State University, Columbus, OH05/08/03 RoC Background Document for Lead and Lead Compounds

xi Criteria for Listing Agents, Substances or Mixtures in the Report on Carcinogens

U.S. Department of Health and Human Services National Toxicology Program

Known to be Human Carcinogens:

There is sufficient evidence of carcinogeni city from studies in humans, which indicates a causal relationship between exposure to the agent, substance or
mixture and human cancer.

Reasonably Anticipated to be Human Carcinogens:

There is limited evidence of carcinogenic ity from studies in humans, which indicates that causal interpretation is cr edible but that alternative explanations such as chance, bias or confounding factor s could not adequately be excluded; or

There is sufficient evidence of carcinogenicity from studies in experimental
animals which indicates there is an incr eased incidence of malignant and/or a combination of malignant and benign tumors: (1) in multiple species, or at multiple tissue sites, or (2) by multiple routes of exposure, or (3) to an unusual degree with regard to incidence, site or type of tumor or age at onset; or

There is less than sufficient evidence of carcinogenicity in humans or laboratory animals, however; the agent, substance or mixture belongs to a well defined, structurally-related class of substances whose members are listed in a previous Report on Carcinogens as either a known to be human carcinogen, or reasonably anticipated to be human carcinogen or there is convincin g relevant information that the agent acts through mechanisms i ndicating it would likely cause cancer in
humans.

Conclusions regarding carcinog enicity in humans or experimental animals are based on scientific judgment, with consideration given to all relevant information. Relevant information includes, but is not limited to dose response, route of exposure, chemical structure, metabolism, pharmacokinetics, sens itive sub populations, genetic effects, or other data relating to mechanism of action or factors that may be unique to a given substance. For example, there may be subs tances for which there is evidence of carcinogenicity in laboratory animals but ther e are compelling data indicating that the agent acts through mechanisms which do not operate in humans and would therefore not reasonably be anticipated to cause cancer in humans.05/08/03 RoC Background Document for Lead and Lead Compounds

xii05/08/03 RoC Background Document for Lead and Lead Compounds

xiii Table of Contents

Executive Summary.............................................................................................................. .........iii

1 Introduction................................................................................................................. .............. 1

1.1 Chemical identification of lead.................................................................................. 1 1.2 Physical-chemical properties of lead ......................................................................... 1

1.3 Chemical forms of lead.............................................................................................. 2 1.3.1 Inorganic lead compounds.......................................................................... 3 1.3.2 Organic lead compounds ............................................................................ 3 1.4 Physical-chemical properties of lead compounds...................................................... 4 1.5 Lead ionization and bioavailabilty............................................................................. 4

1.6 Identification of metabolites ...................................................................................... 5 2 Human Exposure............................................................................................................... ...... 17

2.1 Use ........................................................................................................................ ... 17

2.2 Production................................................................................................................ 1 8 2.3 Analysis................................................................................................................... . 22

2.3.1 Air............................................................................................................. 22

2.3.2 Water......................................................................................................... 24

2.3.3 Soil............................................................................................................ 24

2.3.4 Food .......................................................................................................... 24

2.3.5 Blood ........................................................................................................ 24 2.3.6 Serum or plasma ....................................................................................... 24

2.3.7 Urine ......................................................................................................... 25

2.3.8 Biomarkers................................................................................................ 26

2.3.9 Soft tissue ................................................................................................. 27

2.3.10 Bone and teeth .......................................................................................... 27

2.4 Environmental occurrence ....................................................................................... 28

2.4.1 Air............................................................................................................. 28

2.4.2 Water......................................................................................................... 29

2.4.3 Soil............................................................................................................ 29

2.4.4 Paint .......................................................................................................... 30

2.5 Environmental fate................................................................................................... 30 2.6 Environmental exposure .......................................................................................... 31 2.7 Occupational exposure............................................................................................. 33 2.8 Biological indices of exposure................................................................................. 38 2.9 Regulations .............................................................................................................. 40

2.10 Guidance .................................................................................................................. 40

3 Human Cancer Studies......................................................................................................... ... 41

3.1 IARC assessments.................................................................................................... 41 3.2 Studies published since 1987 or not included in the IARC update.......................... 4305/08/03 RoC Background Document for Lead and Lead Compounds

xiv 3.2.1 Studies of adult cancer focused on specific occupational groups............. 44 3.2.2 Studies of mixed occupational groups...................................................... 54 3.2.3 Studies of occupations exposed to organic lead: case-control study
of TEL workers......................................................................................... 58 3.2.4 Cohort studies based on genera l population (environmental) exposures .................................................................................................. 59 3.2.5 Case-control studies based on ge neral population (environmental) exposures .................................................................................................. 60 3.2.6 Studies of paternal lead exposure and childhood cancer.......................... 61 3.3 Summary.................................................................................................................. 62 3.3.1 Lung and other respiratory cancers and occupational lead exposure ....... 64 3.3.2 Stomach and general digestive cancer...................................................... 69 3.3.3 Kidney cancer ........................................................................................... 71

3.3.4 Bladder cancer .......................................................................................... 72

3.3.5 Childhood cancers .................................................................................... 73

3.3.6 Other adult cancers ................................................................................... 73 3.3.7 General population exposures and cancer ................................................ 74

3.4 Conclusion ............................................................................................................... 75

4 Studies of Cancer in Experimental Animals......................................................................... 103

4.1 Mice ....................................................................................................................... 103

4.1.1 Lead acetate or subacetate ...................................................................... 103 4.1.2 Lead naphthenate.................................................................................... 108

4.1.3 Lead chromate ........................................................................................ 108 4.1.4 Tetraethyl lead ........................................................................................ 109

4.2 Rats ....................................................................................................................... . 109

4.2.1 Lead acetate and lead subacetate ............................................................ 109 4.2.2 Lead phosphate ....................................................................................... 113

4.2.3 Lead chromate ........................................................................................ 113 4.2.4 Other inorganic lead compounds............................................................ 113 4.2.5 Co-administration with other compounds .............................................. 114

4.3 Hamsters ................................................................................................................ 119 4.4 Monkeys................................................................................................................. 120 4.5 Summary................................................................................................................ 120 5 Genotoxicity................................................................................................................. ......... 123
5.1 Prokaryotic systems: Induction of mutations in Salmonella typhimurium

, Escherichia coli , and Serratia marcescens ............................................................ 124

5.2 Plants: in vivo assays.............................................................................................. 124

5.3 In vitro studies using cell-free systems.................................................................. 128 5.4 Mammalian systems............................................................................................... 129 5.4.1 In vitro assays ......................................................................................... 129 5.4.2 In vivo assays.......................................................................................... 13805/08/03 RoC Background Document for Lead and Lead Compounds

xv 5.5 Summary................................................................................................................ 151

6 Other Relevant Data.......................................................................................................... .... 153
6.1 Absorption, distribution, and excr etion of lead in humans.................................... 153 6.1.1 Inorganic lead ......................................................................................... 153 6.1.2 Organic lead compounds ........................................................................ 157 6.2 Other toxic effects of lead compounds .................................................................. 158 6.2.1 Neurotoxicity .......................................................................................... 159 6.2.2 Nephrotoxicity ........................................................................................ 159 6.2.3 Hematoxicity and anemia ....................................................................... 159 6.2.4 Reproductive toxicity ............................................................................. 160 6.2.5 Developmental toxicity........................................................................... 160 6.2.6 Cardiovascular toxicity........................................................................... 160

6.2.7 Other effects in rodents........................................................................... 160 6.3 Mechanisms of lead carcinogenesis....................................................................... 160 6.3.1 Possible mechanisms of genotoxi city and carcinogenicity .................... 161

6.3.2 Indirect mechanisms ............................................................................... 165 6.4 Summary................................................................................................................ 166

7 References................................................................................................................... .......... 169
Appendix A: Lead Regulations................................................................................................... 199

List of Tables

Table 1-1. Physical and chemical properties of lead ...................................................................... 2

Table 1-2. Uses and structures of insoluble lead compounds......................................................... 6
Table 1-3. Uses and structures of soluble lead compounds.......................................................... 12
Table 1-4. Physical-chemical prope rties of insol uble lead compounds a ...................................... 14
Table 1-5. Physical-chemical properties of soluble lead compounds a .......................................... 16
Table 2-1. Mine and smelter production of lead in the United States from 1990 to 1996

(thousands of metric tons)..................................................................................................... ..... 19

Table 2-2. Number of U.S. s uppliers of lead compounds............................................................. 20
Table 2-3. Key world lead producti on and consumption statistics a .............................................. 21
Table 2-4. Common methods for the analysis of lead in environmental samples ........................ 23
Table 2-5. Common methods for the analysis of lead in biological samples ............................... 25
Table 2-6. Biomarkers for lead exposure...................................................................................... 27

Table 2-7. Air lead concentrations in occ upational settings, based on OSHA inspection

data (1979–1985) ............................................................................................................... ........ 37

Table 2-8. Air lead concentrations from NI OSH Health Hazard Ev aluation and Technical

Assistance Program (1994–1999).............................................................................................. 3705/08/03 RoC Background Document for Lead and Lead Compounds

xvi Table 2-9. Blood lead concentrations from various occupations and the general population ..................................................................................................................... ............. 38

Table 2-10. Bone lead concentrations from va rious occupations and referent populations ......... 39
Table 2-11. Key regulations on lead and lead compounds in the United States........................... 40
Table 3-1. Human epidemiologic studies of lead exposure and cancer : published studies

on specific populations, by study design ................................................................................... 45
Table 3-2. Studies of lead exposure and cancer: cohort ............................................................... 76
Table 3-3. Studies of lead expos ure and cancer: case-control...................................................... 91
Table 3-4. Lead exposure and childhood cancer ........................................................................ 100
Table 4-1. Summary of carcinogenicity st udies of lead subacetate in mice............................... 105
Table 4-2. Effects of lead acetate on body- weight gain and urethan-induced lung

adenoma in female Swiss mice................................................................................................ 107

Table 4-3. Effects of lead acet ate on mortality and spontaneous lymphocytic leukemia in

female Swiss mice.............................................................................................................. ...... 107
Table 4-4. Renal tubular cell pr oliferative lesions in B6C3F 1 mice following gestational

and lactational exposure to lead acetate................................................................................... 108
Table 4-5. Summary of carcinogenicity studies of lead subacetate and lead acetate in rats
conducted before 1980.......................................................................................................... ... 110
Table 4-6. Tumor incidence in male Sprague-Dawley rats fed lead subacetate (PbSA) and

calcium acetate (CA)........................................................................................................... ..... 112
Table 4-7. Summary of carcinogenicit y studies of lead phosphate in rats a ................................ 115
Table 4-8. Summary of carcinogenicity studies of lead subacetate co-administered with 2-
AAF in rats a

............................................................................................................................... . 116
Table 4-9. The promoting or co-carcinogenic eff ects of lead acetate or lead subacetate in

rats........................................................................................................................... ................. 117
Table 4-10. Co-carcinogenic eff ects of lead acetate administ ered with FBPA to male
Fisher-344 rats ................................................................................................................ ......... 119
Table 5-1. Genotoxicity of lead co mpounds in prokaryotic systems.......................................... 125
Table 5-2. Genotoxicity of lead compounds in plants in vivo .................................................... 127
Table 5-3. Genotoxicity of lead compounds in vitro in cell-free systems (without

metabolic activation).......................................................................................................... ...... 130
Table 5-4. Genotoxicity of lead compounds in mammalian systems in vitro ............................ 135
Table 5-5. Genotoxicity of lead compounds to mammals in vivo .............................................. 141
Table 5-6. Genotoxicity of lead compounds in vivo in humans ................................................. 149
Table 6-1. Effects of nutritional elements on gast rointestinal lead absorption in animals......... 154

Table 6-2. Mobilization of lead during gestation in Sprague-Dawley rats................................. 157
Table A-1. CPSC regulations.................................................................................................... .. A-1
Table A-2. EPA regulations..................................................................................................... ... A-1
Table A-3. FDA regulations ..................................................................................................... .. A-605/08/03 RoC Background Document for Lead and Lead Compounds

xvii Table A-4. OSHA regulations.................................................................................................... . A-7

List of Figures

Figure 1-1. Physical structure of lead ......................................................................................... .... 2
Figure 2-1. Worldwide lead use by end consumption (2000)....................................................... 18
Figure 2-2. Global lead mine pr oduction and consumption (1964–2001).................................... 22
Figure 2-3. Lead used in gaso line and average blood lead levels measured in NHANES II ....... 32
Figure 6-1. Curvilinear relationship of human serum lead to blood lead ................................... 15505/08/03 RoC Background Document for Lead and Lead Compounds

xviii05/08/03 RoC Background Document for Lead and Lead Compounds

1 

## 1 Introduction

Two lead compounds, lead acetate and lead phos phate, have been listed in the Report on Carcinogens (RoC) since 1981 as reasonably anticipated to be human carcinogens (NTP 2000). Lead and lead compounds were nom inated by the National Institute of Environmental Health Sciences for possibl e listing in the RoC, based on the 1987 listing by the International Agency for Research on Ca ncer (IARC) of lead and inorganic lead compounds as possibly carcinogenic to humans (Group 2B) and the subsequent publication of additional human and animal studies of lead and lead compounds.

1.1 Chemical identification of lead
Elemental lead (Pb, atomic wt 207.2, CASRN 7439-92-1) is an odorless silver-bluish
white soft metal that is insoluble in water. It also is known as C.I. 77575, C.I. pigment metal 4, KS-4, and lead (inorgani c). Its melting point is 327.43 ° C, its boiling point is
1,740 ° C, and its appearance varies depending on the physical structure of the specific compound. Lead exists in the valence states of +2 and +4 and has four naturally occurring isotopes: 204, 206, 207, and 208. Inorga nic lead compounds usually consist of lead in the divalent state (+2). The chemistry of divalent lead is sim ilar to that of other Group 2 metals, which include beryllium, magnesium, calcium , strontium, and barium.

The major chemical forms of lead found in th e environment, as well as in occupational exposures, are reviewed in this report. The U.S. Environmental Protection Agency (EPA) codes for lead and lead compounds are K005, K006, K007, K046, K061, K062, K069, U144, U145, U146, P110, and D008. The R TECS number for l ead is OF7525000, and the shipping code is NA 1794 ORM-C.

1.2 Physical-chemical properties of lead
The physical structure of crystalline lead is cubic and close-packe d, as illustrated in Figure 1-1. Lead is very soft, highly malleable , ductile, and a relativ ely poor conductor of electricity. It is very resistan t to corrosion but tarnishes upon exposure to air. Lead alloys include pewter and solder. The physical and ch emical properties of lead are listed in
Table 1-1.05/08/03 RoC Background Document for Lead and Lead Compounds

2 Source: WebElements 2000.

Figure 1-1. Physical structure of lead

Table 1-1. Physical and chem ical properties of lead

Property Information Reference

Atomic weight 207.2 Budavari et al. 1996, ChemFinder 2000

Color silver-bluish white Budavari et al. 1996, CRC 1998,
ChemFinder 2000

Odor odorless CRC 1998, HSDB 2002

Physical state soft metal Budavari et al. 1996, CRC 1998,
ChemFinder 2000

Melting point ( ° C) 327.43 Budavari et al. 1996, CRC 1998, HSDB
2002

Boiling point ( ° C) 1,740 Budavari et al. 1996, CRC 1998, HSDB
2002

Density (g/cc at 20 ° C) 11.4 HSDB 2002

Vapor pressure (mm Hg at 1,000 ° C) 1.77 HSDB 2002

Crystal system cubic close-packed WebElements 2000

Young’s modulus (GPa) 16 WebElements 2000

Solubility:

water at 20°C

nitric acid

hydrochloric acid insoluble

insoluble as lead nitrate

soluble as lead chloride Budavari et al. 1996, CRC 1998, HSDB 2002, ChemFinder 2000

1.3 Chemical forms of lead

Lead is released into the environment in many different chemical forms. The chemical form of lead determines its water solubility, the types of chemical reactions that occur in the atmosphere, water, and soil, and the exte nt to which lead binds in soils (NSF 1977). The primary source of lead in the environment historically ha s been lead emissions from gasoline-containing lead additive s. The use of leaded gasoline was banned in the United States after December 31, 1995, except for use in gasoline for aircraft and in fuels for racing vehicles and for non-road vehicles (ATSDR 1999) (see Section 2.1). Lead exposure from all chemical forms most commonly is measured in the body by05/08/03 RoC Background Document for Lead and Lead Compounds

3 determining blood lead levels. The results are reported as micrograms of lead per deciliter of blood, and childhood blood lead levels of 10 μ g/dL or higher are considered to present risks to children’s health (see Sections 2.6 and 2.10). Exposure to various chemical forms of lead also may be measured in urine, pl asma, bones, teeth, and hair (see Sections 2.3.6 to 2.3.10).

1.3.1 Inorganic lead compounds

Of the lead emitted from automobiles using leaded gasoline, 90% is in particulate form, and the remaining 10% exists as organic lead vapors (see Section 1.3.2 ). The particle size
distribution varies with the engine operating conditions; how ever, generally, 20% to 30% of the lead particle s are larger than 5 μ m in diameter, 50% to 70% are in the 1- to 5- μ m range, and 5% or fewer are smaller than 1 μ m in diameter. Any particle less than 30 μ m in diameter can be deposited in the nasopha ryngeal region of the re spiratory tract, and particles smaller than 5 μ m can reach the bronchi olar region (Casarett et al. 1996). The majority of compounds detected consist of the lead halides: lead bromide (PbBr 2 ), lead chloride (PbCl 2 ), lead bromochloride (PbBrCl), a nd the alpha and beta forms of the double salt lead bromochloride ammonium chloride (2PbBrCl

⋅ NH 4 Cl) (NSF 1977).

Studies have shown that 95% of the part icles emitted from secondary lead-smelting operations are less than 5 μ m in diameter. The chemical forms most often detected are lead sulfide (PbS), lead sulfate (PbSO 4 ), and elemental lead (NSF 1977). Another form emitted from mining operations and smelters is lead oxide

⋅ lead sulfate (PbO

⋅ PbSO 4 ) (ATSDR 1999).

Once these lead compounds are present in th e atmosphere, they are converted through chemical reactions into a large number of a dditional lead compounds. Some of the lead compounds identified in the atmosphere are 2PbBrCl

⋅ NH 4 Cl, PbSO 4 , lead carbonate (PbCO 3 ), PbBr 2 , PbCl 2 , lead oxide (PbO

x ), lead hydroxychloride (Pb(OH)Cl), lead hydroxybromide (Pb(OH)Br), lead phosphate (Pb 3 (PO 4 ) 2 ), lead oxide

⋅ lead sulfate (3PbO

⋅ PbSO 4 ), lead oxide

⋅ lead chloride (2PbO

⋅ PbCl 2 ), and lead oxide

⋅ lead bromochloride (2PbO

⋅ PbBrCl) (NSF 1977).

Inorganic lead compounds also are found in wa ter and soil. The amount of lead in surface water depends on the pH and the dissolved salt content. In the environment, the divalent form (Pb 2+ ) is the stable ionic form of lead. The fo rms of lead most often found in soil are
PbSO 4 and PbCO 3 , the same compounds identified as primary forms found in the atmosphere (NSF 1977).

1.3.2 Organic lead compounds

The tetraalkyl lead compounds, specifically te traethyl lead (TEL) a nd tetramethyl lead (TML), are the primary organic lead compounds used as automotive gasoline additives in
the United States until 1996 and still used t oday in racing-car and aviation gasoline. The phaseout of tetraethyl and tetramethyl lead fr om automotive gasoline was initiated in the 1970s. These two compounds no longer are presen t in large amounts in the atmosphere; however, their degradation products still exist in the atmosphere. These compounds05/08/03 RoC Background Document for Lead and Lead Compounds

4 decompose rapidly to trialkyl and dialkyl l ead compounds when expos ed to sunlight and eventually degrade to inorga nic lead oxides (ATSDR 1999).

In water, the tetraalkyl lead compounds ar e subject to photolysi s and volatilization. The more volatile compounds are lost to the at mosphere by evaporation. As in air, the degradation process consists of trialkyl lead compounds degrading to dialkyl lead and finally to inorganic lead. Triethyl and trim ethyl lead are more water soluble than are tetraethyl or tetramethyl lead and theref ore are more often detected in aquatic environments (ATSDR 1999).

Another source of organic lead in water is th e conversion of inorgani c lead to tetramethyl lead by microorganisms living in anaerobic lake sediments (Craig et al. 1980, ATSDR 1999). However, if the water over the sediments is aerobic, the tetram ethyl lead will be oxidized, resulting in release of lesser amounts of tetramethyl lead to the water (ATSDR 1999).

In soil, organic lead compounds such as tetramethyl and tetraethyl lead may be converted to highly water-soluble compounds, such as the trialkyl lead oxides. These compounds could be subject to leaching from the soil (ATSDR 1999).

1.4 Physical-chemical propert ies of lead compounds
Tables 1-2 and 1-3 present the chemical form ulas, synonyms, uses, and structures of the major lead compounds, and Tables 1-4 and 1-5 present the physical-chemical properties of these same compounds. The tables are organized according to whether compounds are relatively insoluble in water (T ables 1-2 and 1-4) or relative ly soluble in water (Tables 1- 3 and 1-5). Compounds are considered sol uble or insoluble based on the following criteria: (1) If a solubility constant (K sp ) is available, a compound with a value greater than or equal to the K sp for lead chloride (1 x 10 -4 ) is considered soluble. (2) If a K sp is not available, a compound is considered soluble if more than 2 g of the compound
dissolves in 100 mL of water. (3) If no numeric solubility data are available, the compounds are considered soluble or insoluble based on a general rule of solubility of chemical species, as outlined in McQuarrie and Rock (1984).

1.5 Lead ionization and bioavailabilty
The physical-chemical properties of lead and lead compounds determin e their availability
to be absorbed into the b ody, as well as their other pharm acokinetic properties. Studies have shown that soluble lead compounds are mo re likely to be absorbed into the body than are insoluble compounds and that smaller in organic lead particulat es are absorbed to a greater degree than are larg er particulates (Fleming 1998). The degree of absorption in the body also depends on the particular physical-chemical properties of the lead compound (see Section 6 for a discussion of th e toxicokinetics of lead). In a study in which rats were fed lead in the diet, the pe rcent absorption of metallic lead and several lead compounds was compared with that of lead acetate. The percent absorption was lowest for metallic lead (14%), followed by lead chromate (44%), lead naphthenate (64%), and basic lead carbonate (164%), fo r a 12-fold difference in absorption between metallic lead and basic lead carbonate (Barlt rop 1975). In addition, studies of metals,05/08/03 RoC Background Document for Lead and Lead Compounds

5 including lead, have emphasized the significan ce of chemical speci ation, particularly ionization, in toxicity (Degawa et al. 1994, Ritchie et al. 2001).

1.6 Identification of metabolites

Metallic lead is not metabolized; howeve r, metallic lead and lead compounds are transformed after entry into the body. These tr ansformations are disc ussed in Section 6.05/08/03 RoC Background Document for Lead and Lead Compounds6Table 1-2. Uses and structuresof insoluble lead compoundsCompound, formula,mol wtCASRNSynonymsUsesStructureLead arsenatePbAsHO4347.12717784–40–9acid lead orthoarsenate, acid leadarsenate, arsenic acid lead (2+)salt, arsinetteformerly used as aninsecticide andherbicideOAsHOOO-Pb+2Lead azidePbN6291.240213424–46–9 initiating explosive as an explosiveN-+N-NPb+2 -NN+N-Lead bromidePbBr2367.00810031–22–8 lead(II) bromide (not available)Pb BrBrLead carbonatePbCO3267.2092598–63–0carbonic acid, lead (2+) salt (1:1),lead(II) carbonate, and leadcarbonate, 99.999%as a catalyst, in highpressure lubricatinggreases, and as aphotoconductor forelectrolithography,and in coatings forthermographiccopying, formerlyused in paintOC-O OPb+205/08/03 RoC Background Document for Lead and Lead Compounds7Compound, formula,mol wtCASRNSynonymsUsesStructureLead chromatePbCrO4323.19367758–97–6lead(II) chromate; lead(IV)chromate; chrome yellow;plumbous chromate; crocoite;lead chromate (VI); chromic acid,lead(2+) salt (1:1); canary chromeyellow 40-2250; chrome greenuc61; chrome green uc74; chromegreen uc76; chrome lemon;chrome yellow g; chrome yellowgf; chrome yellow lf; chromeyellow light 1066; chrome yellowlight 1075; chrome yellowmedium 1074; chrome yellowmedium 1085; chrome yellowmedium 1298; chrome yellowprimrose 1010; chrome yellowprimrose 1015; chrome yellow5g; chromium yellow; CI 77600;C.I. pigment yellow 34; cologneyellow; C.P. chrome yellow light;C.P. chrome yellow medium; C.P.chrome yellow primrose;crociote; dianichi chrome yellowg; leipzig yellow; lemon yellow;paris yellow; pigment green 15;pure lemon chrome l3gsas a pigment inpaints, rubber, andplasticsOCrOOO-Pb+2Lead fluoridePbF2245.19697783–46–2lead difluoride, lead(2+) fluoride,and plumbous fluorideas a catalyst, in lowpower fuses, in lowmelting glasses, andin other electronicand opticalapplicationsPbFF05/08/03 RoC Background Document for Lead and Lead Compounds8Compound, formula,mol wtCASRNSynonymsUsesStructureLead fluoroboratePbB2F8380.807213814–96–5lead fluoborate, borate(1-),tetrafluoro-lead(2+), leadborofluoride, lead boron fluoride,and lead tetrafluoroboratein electroplating, as acuring agent forepoxy resins, and as acatalystFBFFFPb+2FBFFFLead iodidePbI2461.00910101–63–0lead diiodide, lead(II) iodide,plumbous iodidein photographicemulsions, aerosolsfor cloud seeding,asbestos brakelinings, andthermoelectricmaterialsPbIILead naphthenatePb(C7H11O2)2461.525450825–29–1cyclohexanecarboxylic acid andlead saltas a varnish drier,catalyst, woodpreservative, andinsecticidePb+2C O-OCO-O05/08/03 RoC Background Document for Lead and Lead Compounds9Compound, formula,mol wtCASRNSynonymsUsesStructureLead oxidePbO223.19941317–36–8lead(II) oxide, lead monoxide,lead oxide yellow, litharge, C.I.77577, lead ocher, leadoxide(mono), lead protoxide,litharge yellow l-28, massicot,massicotite, pigment yellow 46,yellow lead ocher, plumbousoxide, lead(II) oxide yellow, andlead oxide, 99.99%in paint, glass, andceramic products, asa vulcanizing agentin rubber andplastics, and as anintermediate in themanufacture ofpigmentsPb OLead phosphatePb3O8P2811.542727446–27–7lead orthophosphate, plumbousphosphate, trilead phosphate,perlex paste, trileadbis(orthophosphate), phosphoricacid lead(2+) salt (2:3), andlead(II) phosphate (3:2)as a stabilizer forstyrene and caseinplastics and in specialglassesOP-OOOPb+2OP-OOOPb+2Pb+2Lead stearatePb(C18H35O2)2774.14661072–35–1lead distearate, lead(II)noctadecanoate, and lead(II)stearateas a stabilizer forplastics and rubberprocessingO OPb+2O-O05/08/03 RoC Background Document for Lead and Lead Compounds10Compound, formula,mol wtCASRNSynonymsUsesStructureLead styphnatePbC6HO2(NO2)3450.200063918–97–8initiating explosive leadstyphnate, lead trinitroresorcinate,and styphnate of leadin munitionsmanufactureONO2NO2O2NOPb+2Lead sulfatePbSO4303.25767446–14–2lead(II) sulfate, anglistlite, whitelead, fast white, milk white,sulfuric acid lead (2+) salt (1:1),lead sulfate basic, lead sulfate99.999%, and lead sulphate(lead(II) sulfate)in photography, inlithography, in earthfill dams, and roads,and with zinc ingalvanic batteriesOSOO OPbLead sulfidePbS239.261314–87–0galena, plumbous sulfide, lead(II)sulfide, lead monosulfide, leadsulfide 99.999%, and lead sulfide(1:1)in ceramics, as asemiconductor, as acatalyst, as a mirrorcoating, and as ahumidity sensor inrocketsPb SLead tetraoxidePb3O4685.59761314–41–6mineral red, lead oxide, red leadoxide, orange lead, andlead(II,III) oxidein plasters, ointments,glazes, and varnishes,for coloring ofrubber, incement forglass, in storagebatteries, and inpaintsPbOPbOPbOOLead thiocyanatePb(SCN)2323.3554592–87–0isothiocyanic acid lead(2+) salt,lead dithiocyanate, lead(II)thiocyanate, lead isothiocyanate,and lead sulfocyanatein manufacture ofsafety matches andcartridgesPb+2-SNSN05/08/03 RoC Background Document for Lead and Lead Compounds11Compound, formula,mol wtCASRNSynonymsUsesStructureTetraethyl leadPb(C2H5)4323.44678–00–2motor fuel anti-knock compound,lead tetraethyl,tetraethylplumbane, TEL, andtetraethyl lead (liquid)as an antiknockadditive in gasoline,banned since 1996 inmotor vehicles in theU.S.PbH2CCH2CH2CH2H3C CH3H3CH3CTetramethyl leadPb(CH3)4267.338875–74–1lead tetramethyl, TLM,tetramethylplumbane, TML, andtoluene blend no.2as an antiknockadditive in gasoline,banned since 1996 inmotor vehicles in theU.S.CH3PbH3CCH3CH3Sources: ChemFinder 2000, HSDB 2002.05/08/03 RoC Background Document for Lead and Lead Compounds12Table 1-3. Uses and structuresof soluble lead compoundsCompound, formula,mol wtCASRNSynonymsUsesStructureLead acetatePbC4H6O4325.289301–04–2acetic acid, lead(2+) salt, sugar oflead, lead diacetate, lead(II) saltacetic acid, normal lead acetate,neutral lead acetate, lead dibasicacetate, and dibasic lead acetateas a water repellant, formildew prevention, as acoloring agent, and as amordant in cotton dyes.PbOCH3COOCCH3OLead acetate trihydratePbC4H12O7379.33466080–56–4salt of Saturn, lead acetate (II),trihydrate, acetic acid-lead(+2)salt trihydrate,bis(acetato)trihydroxy-trilead,lead diacetate trihydrate, andacetic acid-lead salt trihydratein varnishes, chromepigments, andantifouling paints, inhistorical paintmanufacture, and as ananalytical reagentOOCH3C-OCOCH3H HOHOH HOHPb+2Lead chloridePbCl2278.1067758–95–4lead(II) chloride and leaddichloridein manufacture oforganolead compounds,in asbestos clutch orbrake linings, as acatalyst, and as a flameretardantPbClCl05/08/03 RoC Background Document for Lead and Lead Compounds13Compound, formula,mol wtCASRNSynonymsUsesStructureLead nitratePbN2O6331.209810099–74–8lead dinitrate, nitric acid-lead(2+)salt, lead(II) nitrate, and leadnitrate, 99.5%in manufacture ofmatches and explosives,as a heat stabilizer innylon, and as a coatingon paper forphotothermographyON+-O OPb+2ON+-O OLead subacetatePb2C4H8O6566.50361335–32–6bis(acetato-O)tetrahydroxytrilead,basic lead acetate,bis(acetato)tetrahydroxytrilead,bis(aceto)tetrahydroxytrilead,bis(aceto)dihydroxytrilead, BLA,monobasic lead acetate, andsubacetate leadin sugar analysis andfor clarifying solutionsof organic substancesH3CCOOPb+2-OCCH3OPb+2OH-OH-Sources: ChemFinder 2000, HSDB 2002.05/08/03 RoC Background Document for Lead and Lead Compounds14Table 1-4. Physical-chemical properties of insoluble lead compoundsaCompound,formulaColor andphysical stateMelting point(oC)Boiling point(oC)Density orspecific gravitySolubility, reactivityLead arsenatePbAsHO4white powder or crystals 280 NA 5.94insoluble in water; soluble in nitricacid and alkaliLead azidePbN6white needles or powder NA explodes at 350 NA 230 mg/L at 18oC in waterLead bromidePbBr2white crystalline powder 373 916 6.668,441 mg/L at 20oC in water;insoluble in alcoholLead carbonatePbCO3colorless rhombic crystals 315 NA 6.6Ksp= 1.1 x 10-15; insoluble in water,ammonia, or ethanol; soluble in acidand alkaliLead chromatePbCrO4yellow or orange yellowpowder844 decomposes NAKsp= 1.7 x 10-14; insoluble in water,< 0.1 g/100 mL at 19°CLead fluoridePbF2colorless to white crystals 824 1,293 8.44 (orthorhombic)7.75 (cubic)insoluble in water, acetone, orammonia; soluble in nitric acidLead fluoroboratePbB2F8colorless crystallinepowderNA NA 1.75 decomposes in alcoholLead iodidePbI2bright yellow crystals orpowder402 954 6.16630 mg/L at 20oC; insoluble inalcoholLead naphthenatePb(C7H11O2)2yellow semi-transparentpaste100 NA 1.15insoluble in water; soluble inethanolLead oxidePbOyellow or reddish-yellowcrystals888 1,470 9.53insoluble in water or alcohol;soluble in alkali,ammonia chloride,acetic acid, and nitric acidLead phosphatePb3O8P2white solid powder 1,014 NA 6.9insoluble in water or ethanol;soluble in alkali and nitric acid05/08/03 RoC Background Document for Lead and Lead Compounds15Compound,formulaColor andphysical stateMelting point(oC)Boiling point(oC)Density orspecific gravitySolubility, reactivityLead stearatePb(C18H35O2)2white powder NA NA NA NALead styphnatePbC6HO2(NO2)3orange-yellow crystals NA NA NA NALead sulfatePbSO4white heavy crystalpowder1,170 NA 6.2Ksp= 1.5 x 10-8; soluble in sodiumhydroxide; insoluble in alcoholLead sulfidePbSmetallic black cubiccrystals1,114 1,281 7.57–7.59Ksp= 1 x 10-28; soluble in nitricacid; insoluble in alcohol, potassiumhydroxide, or waterLead tetraoxidePb3O4bright-red heavy powder 500 NA 9.1soluble in hydrochloric and aceticacid; insoluble in water or ethanoloxidizing materialLead thiocyanatePb(SCN)2white crystals 190 NA 3.82insoluble in water; soluble in alkalihydroxide, thiocyanate solutions,and lead sulfocyanateTetraethyl leadPb(C2H5)4colorless liquid or dyedred, orange, or blue, witha slight musty odor-136.8 200 1.659Ksp> 4 x 10-15; insoluble (0.000021g/100 mL) in water; soluble inbenzene, ethanol, and diethyl etherflash point is 93°CTetramethyl leadPb(CH3)4colorless liquid or dyedred, orange, or blue, witha slight musty odor-27.5 110 1.995insoluble in water; soluble inbenzene, ethanol, and diethyl etherflash point is 37.7°CSources: ChemFinder 2000, HSDB 2002.NA = not available.05/08/03 RoC Background Document for Lead and Lead Compounds16Table 1-5. Physical-chemical properties of soluble lead compoundsaCompound, formula,mol wtColor andphysical stateMelting point(oC)Boiling point(oC)Density orspecific gravitySolubility, reactivityLead acetatePbC4H6O4colorless or whitecrystals, granules,or powder280 NA 3.25 at 20oCKsp= 2 x 10-2; 1–5 g/100 mL water at 20°C;slightly soluble (< 0.1 g/100 mL) inethanol; slightly soluble (1–5 g/100 mL) inDMSO; slightly soluble (< 0.1 g/100 mL)in acetone; soluble in glycerolLead acetate trihydratePbC4H12O7white crystals 75 280 2.55miscible in water; slightly soluble inethanol and acetone; soluble in glycerolsensitive to air; reagent for neutralization ofamino acids and hydrochloridesLead chloridePbCl2white crystallinepowder501 950 5.85Ksp= 1 x 10-4; soluble in water, dilutehydrochloric acid, and ammonia; insolublein ethanolLead nitratePbN2O6colorless or whitecrystals470 NA 4.53Ksp= 2 x 10-2; soluble in water, 43%ethanol, alkali, and ammonia; insoluble innitric acidoxidizing materialLead subacetatePb2C4H8O6white heavy powder 75 decomposes NA soluble in water and ethanolsensitive to airSources: ChemFinder 2000, HSDB 2002.NA = not available.05/08/03 RoC Background Document for Lead and Lead Compounds

17 

## 2 Human Exposure

2.1 Use

In worldwide metal use, lead ranks behind only iron, copper, aluminum, and zinc (Howe 1981). Lead may be used in its pure form as a metal, alloyed with other metals, or used in chemical compounds. The utility of lead ma y be derived from its low melting point (327 ° C), high density (11.4 g/cm 3 ), malleability, chemical stab ility, and resistance to acid corrosion (Howe 1981). The vast majority of le ad used, both in the United States and internationally, is in lead- acid storage batteries found in motor vehicles and general industry. Other common uses of lead meta l include ammunition, cable covering, piping, brass and bronze, bearing metals for m achinery, and sheet lead (ATSDR 1999). In addition, lead-based metals are used in sold ers, shipping containers , radiation shielding, building construction, and metal cans. Lead oxi des are found in paint, glass, and ceramics (Smith 2002a). However, in the United States, le ad is no longer used as a solder in piping for drinking water, as a solder in food cans, or in house paints, because of environmental and health concerns (ATSDR 1999).

In the early 1970s, the U.S. EPA began to regu late the lead content in gasoline. Before that, approximately 250,000 tons of organic lead (tetraethyl and tetramethyl lead) were added to gasoline annually in the United Stat es as an anti-knock additive. By 1988, a lead phase-down program had reduced the total lead us age in gasoline to le ss than 1% of that in 1970. In 1996, lead was totally banned as an additive to fuel in motor vehicles in the United States (ATSDR 1999). However, organic lead still is permitted for use in gasoline for aircraft and in fuels for racing vehicles and for non-road vehicles, such as farm machinery, marine vessels, construction equi pment, and recreational vehicles (Smith 2000).

Lead also is used in folk remedies and cosm etics, particularly in developing countries (UNEP-UNICEF 1997). There is evidence that traditional cosmetics containing lead, such as the eye cosmetic kohl, have been purch ased and used in the United States (Parry and Eaton 1991).

Despite reductions in some lead applications and the legislated end to use of lead as a gasoline additive, the overall consumption of lead is growing. From 1990 to 1996, the use of lead in the United States grew at an av erage annual rate of 3.3% . This trend was due primarily to increased production of lead-acid batteries. The proportion of lead used for this purpose increased from ju st below 80% to nearly 88% in this time span (ATSDR 1999). The vast majority of lead-acid batteries find application as starting, lighting, and ignition batteries in motor vehicles. The re mainder are designed for various industrial motive power and stationary power battery applications (Smith 2000). Figure 2-1 shows
the end uses of lead worldwid e in 2000 (neither the data no r the percentages of the uses are provided in the reference).05/08/03 RoC Background Document for Lead and Lead Compounds

18 Source: LDA 2002.

Figure 2-1. Worldwide lead use by end consumption (2000)

2.2 Production

Lead is refined from mined ore. Lead ore o ccurs most frequently in the form of lead sulfide, also known as galena. Anglesite (PbSO 4 ) and cerussite (PbCO 3 ) are two other common ores (Howe 1981). In the United St ates, virtually all lead mines are underground, rather than open pits (ATSDR 1999). As of 2000, 19 mines produced the vast majority of lead in the United St ates (Smith 2000), employing approximately 1,000 workers (Smith 2002b). Mines were located in Alaska, Idaho, Missouri, Montana, Nevada, New York, and Tennessee, with ove r 90% of the total mining occurring in Missouri and Alaska (Smith 2000). Mined l ead ore first is crushed and ground. The various minerals are then separated by di fferential flotation, resulting in a lead concentrate which is shipped to a primary sm elter for refining. In 2001, two primary lead smelter-refineries were operating in Missouri and one primary lead smelter was operating in Montana, employing a total of a pproximately 400 people (Smith 2002b).

At a primary smelter, lead concentrates are sintered to remove sulfur dioxide and other volatile oxides, and the product is roasted w ith by-products and coke. Molten lead is
formed in the blast furnace dur ing the smelting process; impurities are collected in a slag. Drossing is performed to remove copper, le ad oxide, and other compounds. Additional refining is performed to separate out minor qua ntities of silver, antimony, arsenic, copper, and bismuth. The resulting lead metal is 99.99% pure.

Secondary smelters (recycling smelters) use scrap lead, mainly from used lead-acid batteries, as their supply. Us ed batteries are passed through a separation unit that removes leaded materials and processes the battery acid. The remaining leaded materials are05/08/03 RoC Background Document for Lead and Lead Compounds

19 passed through rotary, reverberatory, or blas t furnaces, with an impure lead (or lead alloy) resulting (Howe 1981). The impure meta l may then be refined, with its drosses submitted back for reprocessing. Lead recove ry efficiencies of 98% may be achieved through secondary smelters. As of 2001, 26 s econdary lead smelters were operating within the United States (Smith 2002b); approx imately 98% of total lead recycling was carried out by seven companies operating a to tal of 15 plants in Alabama, California, Florida, Indiana, Louisiana, Minnesota, Mi ssouri, New York, Penns ylvania, Tennessee, and Texas (Smith 2000). In total, secondary lead smelting employs approximately 1,600 workers nationwide (Smith 2002a). From 1990 to 1996, the share of total lead metal production coming from secondary smelters ro se from just under 70% to 77% (ATSDR 1999). This trend toward secondary production is reflected in Table 2-1, which provides data on recent U.S. lead mining and smelting production (ATSDR 1999).

Table 2-1. Mine and smelter production of lead in the United States from 1990 to 1996 (thousands of metric tons)

1990 1996 Percentage change

Mining 484 436 -10

Primary smelting 404 326 -19

Secondary smelting 922 1,100 +19

Source: ATSDR 1999.

Statistical data are available on lead mi ning in the United States going back over 100 years; in fact, there is information to indica te that lead was mined and smelted in North America as early as 1621. In the 1830s, annual U.S. production was reported at 2.7 million kg. In 1976, U.S. production of lead was reported at 550 million kg, with imports at 208 million kg in 1976 and 318 million kg in 1978. Exports were reported at 5.3 million kg in 1976, 9.0 million kg in 1977, and 8.0 million kg in 1978.

Lead acetate was first produced in the United States in 1944, with imports in 1978 reported at 112.7 kg (IARC 1980). U.S. producti on of lead acetate was approximately 300,000 kg in 1977 and 200,000 kg in 1980, with imports reported at approximately 52,000 kg in 1984 and 50,000 kg in 1985 (NTP 2000). Lead carbonate has been produced commercially in the United States since the 1600s; in 1976, U.S. production was 1.48 million kg, with imports in 197 8 of 178,000 kg (IARC 1980). Commercial production of lead naphthenate in the Unite d States was first reported in 1944. In 1969, production of lead naphthenate was 8.2 million kg, with production dropping to 2.2 million kg in 1977 (IARC 1980). Lead nitrate was first commercially produced in the United States in 1943, and imports of 480,000 kg were reported in 1978 (IARC 1980). U.S. production of lead oxide in 1976 was 120 million kg, with imports at 20 million kg (IARC 1980). Commercial production of lead sub acetate was first reported in the United States in 1947 (IARC 1980); no pr oduction data are available. U.S. production of lead tetraoxide in 1976 was reported at 18 m illion kg, with imports at 800,000 kg in 1976 and 1 million kg in 1979. In 1977, approximately 1 to 15 million kg were exported (IARC 1980).05/08/03 RoC Background Document for Lead and Lead Compounds

20 Tetraethyl lead was first produced commerc ially in the United States in 1923, with 266 million kg produced in 1964; production dropped in 1977 to 148 million kg. Imports of tetraethyl lead in 1978 were 17,000 kg (IARC 1980). Commercial production of tetramethyl lead in the United States began in 1960, with 54 million kg produced in 1977 and 13,800 kg imported in 1974 (IARC 1980).

Table 2-2 shows the number of U.S. suppliers of the lead compounds listed in Tables 2-2
and 2-3.

Table 2-2. Number of U.S. suppliers of lead compounds

Lead compound Number of U.S. suppliers

Lead acetate 26

Lead acetate trihydrate 19

Lead arsenate 3

Lead azide (not reported)

Lead bromide 13

Lead carbonate 20

Lead chloride 16

Lead chromate 13

Lead fluoride 17

Lead fluoroborate 15

Lead iodide 21

Lead naphthenate (not reported)

Lead nitrate 44

Lead oxide 30

Lead phosphate 4

Lead stearate 10

Lead styphnate (not reported)

Lead subacetate 15

Lead sulfate 8

Lead sulfide 17

Lead tetraoxide 9

Lead thiocyanate 10

Tetraethyl lead 3

Tetramethyl lead 2

Source: Chem Sources 2002.

Worldwide production data from 2001 show that the United States is the major producer, user, and recycler of lead, and that Australia mines more lead than any other country (see Table 2-3). Global statistics s how that lead production and consumption increased fairly05/08/03 RoC Background Document for Lead and Lead Compounds

21 steadily from 1964 to 2000, while worldwid e mine production decreased slowly, remaining steady over the last few years (see Figu re 2-2) [It is not st ated in the reference
whether these statis tics are for metallic lead or lead compounds.].

Table 2-3. Key world lead produc tion and consumption statistics a

Lead (tons)

Top mining countries

Australia 714,000

China 599,000

United States 459,000

Peru 289,000

Canada 154,000

Largest lead producers

United States 1,375,000

China 1,172,000

United Kingdom 382,000

Germany 375,000

Japan 302,000

Major users of lead

United States 1,687,000

China 650,000

Germany 403,000

United Kingdom 323,000

South Korea 314,000

Main recyclers of lead

United States 1,099,000

Germany 218,000

United Kingdom 183,000

Japan 175,000

Italy 164,000

Source: LDA 2002.

*The statistics in this table do not include the amount of lead imported and exported; therefore the amount of lead produced is not equal to the amount of lead used by the countries cited in this table.05/08/03 RoC Background Document for Lead and Lead Compounds

22 Source: LDA 2002.

Figure 2-2. Global lead mine prod uction and consumption (1964–2001)

2.3 Analysis
The most common techniques for the analysis of lead in environmental or biological samples include atomic absorption spectro metry (AAS), graphite furnace atomic absorption spectrometry (GFAAS), particle-i nduced X-ray emission (PIXE), inductively coupled plasma mass spectrometry (ICP-MS) , inductively coupled plasma atomic emission spectrometry (ICP-AES), and a node-stripping voltametry (ASV). Isotopedilution mass spectrometry (IDMS) is the best technique for applications involving very low lead concentrations (NRC 1993) but is not commonly used because of its equipment requirements and reliance on technical expert ise (ATSDR 1999). A brief overview of the methods for lead analysis in various medi a is presented below, along with summary tables for the methods most commonly used fo r environmental lead an alysis (Table 2-4) and biological lead an alysis (Table 2-5).

2.3.1 Air

Lead in air may be given as a concentrati on of lead in particulate or gaseous form, usually expressed as micrograms of lead pe r cubic meter. The most common methods for the analysis of particulate lead in air are AAS, GFAAS, PIXE, and ICP-AES. A filtering approach is used to isolate particulate l ead. GFAAS has a lower limit of detection than AAS (approximately 0.25 ng/m 3 and 100 ng/m 3 , respectively) but is more sensitive to spectral interference arising from the matr ix (NRC 1993). Lead in gaseous form is organic lead and often is detected by GFAAS. Gas chromatography with AAS (GCAAS), with a detection limit of approximately 0.2 ng/m 3 , also may be used to distinguish among species of organic lead (De Jonghe et al. 1981).05/08/03 RoC Background Document for Lead and Lead Compounds

23 Table 2-4. Common methods for the analysis of lead in environmental samples

Matrix Preparation Procedure Detection
limit Reference

Air Collect particulates onto membrane filter, digest with nitric acid and hydrogen peroxide, heat, dilute with distilled water. GFAAS 2 μ g/m 3

(particulate) ATSDR 1999

Collect particulates onto stretched-Teflon filter, mount into 3- mm slide frame. PIXE 0.6 ng/m 3

(particulate) Eldred and Cahill
1994

Collect particulates onto cellulose nitrate filter, add 206 Pb spike to filter, dissolve in sodium hydroxide, acidify with nitric acid, separate lead by electrodeposition. IDMS 0.008 ng/m 3

(particulate) Völkening et al.
1988

Filter gas, pass through iodine monochloride bubbler, convert lead compounds, extract with carbon tetrachloride solution, follow with acid
extraction. GFAAS 0.25 ng/m 3

(gaseous) Birch et al. 1980

Filter gas, trap gas cryog enically. GC/GFAAS 0.2 ng/m 3

(gaseous) De Jonghe et al.
1981

Water Filter water through membrane filter, dissolve particulates by wet ashing. AAS 100 μ g/L (particulate) ATSDR 1999

Filter water through membrane filter, dissolve particulates by wet ashing. ICP-AES 42 μ g/L (particulate) ATSDR 1999

Filter water through membrane filter, dissolve particulates by wet ashing. GFAAS 1 μ g/L (particulate) ATSDR 1999

Filter water, complex with sodium diethyldithiocarbamate, extract with pentane, run off water, butylate, extract sample with nonane. GC/AAS 2.5 ng/L (dissolved) Chakraborti et al.
1984

Soil Dry ash, digest with hydrochloric and nitric acids (3:1), dilute with water. AAS 2 μ g/g Beyer and
Cromartie 1987

Dry sample and sieve, digest with nitric acid, agitate, centrifuge. ICP-AES 0.09 μ g/g Schmitt et al.
1988

Food Digest with sulfuric acid and dry ash, dissolve in hydrochloric acid, dilute with

water. GFAAS 5 ng/g (bread) Ellen and Van
Loon 1990

Dry ash sample; dissolve with nitric acid
and water. ASV 1 ng/g (evaporated milk) Capar and Rigsby
1989

Dry ash sample with sulfuric acid; dilute
with nitric acid and water. DPASV 0.4 ng/g (crops) Satzger et al. 1982

Source: ATSDR 1999 (with additional references).05/08/03 RoC Background Document for Lead and Lead Compounds

24 2.3.2 Water

Lead in water may be analyzed for concentrat ion in particulate form or dissolved form, usually expressed as micrograms per liter or parts per billion. Techniques frequently used in the analysis of lead in water include AAS, GFAAS, and ICP-AES. ICP-MS is a more sensitive method, with a detection limit of about 1/1,000th that of ICP-AES (which is approximately 42 μ g/L). For this reason, use of ICP- MS is becoming more widespread, not only for water lead analysis, but also for measurement of lead in other environmental and biological media. For dissolved lead an alyses, GC-AAS can be used to separate organic lead into its va rious species (Chakraborti et al. 1984).

2.3.3 Soil

AAS, GFAAS, or ICP-AES may be used to dete rmine lead concentrations in soil. Total lead or organic lead may be assessed. ICP-AES is the most sensitive technique in common application, with a det ection limit of approximately 0.09 μ g/g. As in analysis of other environmental media, GC-AAS may be used to distinguish among organic species of lead (Chau et al. 1979).

2.3.4 Food

Analyses of lead concentrations in food genera lly are similar to analyses of lead in soil. AAS, GFAAS, and ICP-AES are most comm on, although ASV and differential pulse anode-stripping voltametry (DPASV) have been introduced with good results (Satzger et al. 1982, Capar and Rigsby 1989). GFAAS has a de tection limit of approximately 5 ng/g for measurement of lead in bread (Ellen and Van Loon 1990), and ASV has a detection limit of approximately 1 ng/g for measurement of lead in evaporated milk (Capar and Rigsby 1989).

2.3.5 Blood

Measurement of lead in whole blood is th e most common biological means of monitoring exposure and is a routine occ upational health procedure fo r many lead-exposed workers. Measurements of blood lead reflect expos ure to all lead compounds (inorganic and organic) and all routes of exposure (inha lation, oral, and dermal). Blood lead gives information only about fairly recent absorpti on, since the half-life of lead in blood has been measured at 36 days (Rabinowitz et al. 1976) and 28 days (Griffin et al . 1975, as cited in ATSDR 1999). The most common a pproaches are AAS, ASV, GFAAS, and ICPMS. The sensitivities of these methods, whose detection limits range from approximately

4 to 10 μ g/L, are generally sufficient for either occupational or environmental lead
exposure assessment.

2.3.6 Serum or plasma

Although lead more frequently is assessed in whole blood, it also is technically possible to analyze its concentration in serum or plas ma, but with severe difficulties owing to the low lead concentrations. This analysis is desi rable, since it is believe d that the quantity of lead in blood plasma governs the amount avai lable for distribution to tissue (Leggett 1993, O'Flaherty 1993). Analysis of lead in plasma or serum is becoming more common with improved techniques, primarily involvi ng ICP-MS. Recent studies have shown that05/08/03 RoC Background Document for Lead and Lead Compounds

25 lead in serum is 0.08% to 0.29% of that in whole blood, as measured by ICP-MS (Manton et al. 2001, Cake et al. 1996, Smith et al. 2002). As noted above for blood, lead concentrations in serum or plasma will reflect all routes of exposure to all lead compounds.

Table 2-5. Common methods for the analys is of lead in biological samples

Matrix Preparation Procedure Detection
limit Reference

Blood Digest with nitric, perchloric, and sulfuric acids (3:1:1), heat. ICP-AES 10 μ g/L ATSDR 1999

Wet ash, combine with dithizone, extract. AAS 10 μ g/L Gerhardsson et al.
1995a

Wet ash. GFAAS 4 μ g/L Zhang et al. 1997

Dilute with Triton X-100, nitric acid, and thallium internal standard; agitate. ICP-MS 0.06 μ g/L Roberts et al.

2000

Concentrate on mercury thin-film electrode, strip from electrode. ASV 1 pg NRC 1993

Serum

or plasma Dilute, add bismuth nitrate as internal
standard. ICP-MS 0.015 μ g/L Schütz et al. 1996

Spike with lead isotope, heat in distilled
nitric acid . ICP-MS 0.015 μ g/L Manton et al.

2001

Urine Wet ash with acid mixture and dissolve in perchloric acid. ASV 4 μ g/L NIOSH 1977

Extract with polydithiocarbamate resin and sodium hydroxide, agitate, filter, neutralize with sodium hydroxide, ash, heat, dilute
with water. ICP-AES 0.5 μ g/L ATSDR 1999

Soft
tissues Digest with sulfuric acid and dry ash, dissolve in hydrochloric acid, dilute with

water. GFAAS 5 ng/g (bovine) Ellen and Van
Loon 1990

Ash, add nitric acid, stir solution. GFAAS 2 ng/g (human) Gerhardsson et al.
1995b

Bone Excitation of lead with partially planepolarized X-rays, characteristic lead L-shell X-rays detected. LXRF 5 μ g/g

( in vivo ) Markowitz and
Shen 2001

Excitation of lead with 109 Cd γ -ray source, characteristic lead K-shell X-rays detected. KXRF 6 μ g/g

( in vivo ) Todd et al. 2000,

Hu et al. 1995

Source: ATSDR 1999 (with additional references).

2.3.7 Urine

Lead concentration in urine may be measured with good sensitivity by methods such as AAS, ASV, or ICP-AES. Detection limits fo r these methods range from approximately

0.5 to 4 μ g/L. Usually, measurement of blood lead concentration is considered a more05/08/03 RoC Background Document for Lead and Lead Compounds

26 direct biological appr oach to assessing current exposure. However, given the sampling limitations and the analytical difficulties of measuring lead in plasma, some researchers have used lead in urine as a proxy for lead in plasma that will provide an estimate of lead exposure from all routes and to all lead compounds (Tsaih et al. 1999, Gulson et al. 2000). Exposure to lead has on occasion been assessed by administration of a chelating agent, such as edetate calcium disodium ( calcium disodium ethylenediaminetetraacetate dihydrate), followed by measurement of lead excreted in the urine.

2.3.8 Biomarkers

Biomarkers used to identify exposure to lead usually measure the level of total lead in
tissues and fluids. Total lead measurements in the body reflect exposure to all lead compounds (inorganic and organic) from all sources of exposure (inhalation, oral, and dermal). Tetraalkyl lead co mpounds are the only lead compounds that may be measured in the breath, in addition to being measured in body tissues and fluids (ATSDR 1999).

A variety of biomarkers ar e available for monitoring l ead exposure, effects, and susceptibility (NRC 1993). Some of the most commonly used biomarkers are those based on disturbance of heme synthesis by lead (see Table 2-6). One of these assays measures erythrocyte protoporphyrin (EP) or zinc protoporphyrin (ZPP) concentration in blood, and another measures the activity of δ -aminolevulinate dehydratase (ALAD; also known as porphobilinogen synthetase). EP and ZPP increase following lead exposure, while ALAD activity decreases (NRC 1993). However, EP measurements many not accurately reflect lead levels in populati ons that may be iron deficient, such as low-income children, because iron influences EP levels (Mahaffe y and Annest 1986). EP has a sensitivity of

0.351 at blood lead levels of 15 μ g/dL or higher, with sensitiv ity defined as the ability to detect a condition when it is present. This mean s that on average, the EP test will identify

about 35% of children with blood lead levels of 15 μ g/dL or higher and will fail to detect
about 65% of these children. As the blood l ead concentration increases, the EP test becomes more sensitive. For example, at blood lead concentrations of 30 μ g/dL or higher, the sensitivity is approximately 0.87 (NRC 1993). Other biomarkers based on disturbance of heme synthesis are measurement of increased urinary δ -aminolevulinic acid (ALA) and the accumulation of coproporphyrin in urine.

In addition, a number of biomarkers of lead exposure are not based on heme-synthesis effects (see Table 2-6). One biomarker meas ures lead’s inhibition of the enzyme pyrimidine-5'-nucleotidase (Py- 5'-N), another measures decr eased plasma concentrations of the hormonal metabolite 1,25-dihydroxyvitamin D, and a third measures inhibition of erythrocyte membrane Na + ,K + -ATPase (NRC 1993).

Other biomarkers include measurement of l ead in bones, teeth, and hair (see Section 2.3.10 for a discussion of lead in bone and teeth) . Hair has been used in the past and is currently being used as a biomar ker of lead exposure. However, use of hair analysis in a clinical setting poses many problems, incl uding inaccuracy of measurements due to exogenous contaminants (such as sweat, dust, an d beauty treatments), variable analytic procedures, and low interlaboratory relia bility (Frisch and Schwartz 2002).05/08/03 RoC Background Document for Lead and Lead Compounds

27 2.3.9 Soft tissue

The analysis of lead in soft tissue norma lly is limited to autopsy studies (Barry 1975,
Gerhardsson et al. 1995b) and has included measuremen ts in kidney, liver, brain, lung, testis, and spleen. Analysis methods incl ude AAS, GFAAS, ASV, and ICP-AES, with detection limits of 2 to 5 ng/g (ATSDR 1999).

2.3.10 Bone and teeth

Because the half-life of lead in bone is on the order of years to decades (Gerhardsson et al. 1993), analysis of bone lead is more reflec tive of long-term than short-term exposure. The two main approaches to in vivo bone lead measurement are L-shell X-ray fluorescence (LXRF) and K-shell XRF (KXRF) . The lower energies involved in the LXRF technique mean that this measuremen t samples a more superficial component of bone than does the KXRF approach (Todd a nd Chettle 1994). Common bone sites for measurements include the tibia, calcaneus, and patella. Lead content in teeth also may be assessed, either in vivo by XRF methods or, more co mmonly, by techniques such as IDMS (Gulson 1996) or ASV (Kim et al. 1996) with shed deciduous teeth.

Table 2-6. Biomarkers for lead exposure

Lead effect Result Marker threshold,
lead concentration ( μ g/dL) Comments

Heme synthesis disturbances biomarkers

Inhibition of ALAD activity accumulation of ALA in
tissues and urine 5 sensitive for current population blood lead concentrations; problematic relation to
tissue effects

Feedback stimulation of ALA synthetase activity minor contribution to
total ALA in urine 40 not a feasible marker

Accumulation of urinary

ALA -- 20–40 useful for population screening; limited in individual predictability;
not useful for childhood screening

Inhibition of heme
formation from protoporphyrin IX accumulation of erythrocyte protoporphyrin in blood 15–20 (children)

25–30 (adults) most common screening
marker for children and
workers

Impaired use of coproporphyrin accumulation of coproporphyrin in urine 40 supplanted in popularity by EP measurement

Non-heme synthesis biomarkers

Inhibition of Py-5'-N activity in erythrocytes accumulation of ribosomal fragments in reticulocytes 5–10 quite sensitive05/08/03 RoC Background Document for Lead and Lead Compounds

28 Lead effect Result Marker threshold,
lead concentration ( μ g/dL) Comments

Inbition of Na + , K +

- ATPase in erythrocyte
membrane potassium loss and net sodium gain in cells;
altered cell survival not established studies in lead workers;
direct measure of lead’s presence; subject to
contamination

Inhibited hydroxylation
of 25-OH-vitamin D reduction in hormonal metabolite 1,25-(OH) 2 - vitamin D 10–15 important health effect, not appropriate for use
as biomarker

Source: NRC 1993.

2.4 Environmental occurrence
Lead is a naturally occurring element found in the earth’s crust in trace quantities of approximately 8 to 13 ppm (Rudnick and Fountain 1995, Taylor and McLennan 1995). Lead exists in the crust in a number of ores, predominantly as lead sulfide (galena). In the absence of human activity, small amounts of lead would reach the surface environment by natural weathering processes to create a baseline exposure, which in localized areas such as mineral provinces can be very hi gh. The abundant and widespread presence of
lead in our current environmen t is largely a result of anthropogenic activity. In this respect, lead has a long history; evidence exists that lead ha s been used for approximately 6,000 years (Hunter 1978). The ubiquity of l ead in the environm ent has resulted in modern body burdens that are, by one estima te, 300 times those found in pre-industrial humans (Patterson et al. 1991).

2.4.1 Air

Lead is released to air by natural processes such as volcanic activity, forest fires, crustal weathering, and radioactive decay from ra don. These natural contributions are of relatively minor consequence. The vast majority of lead in the atmosphere results from human activity. A major change in lead emi ssion patterns in the United States resulted from the phasing out of tetraethyl lead as an anti-knock fuel additive. The overall emissions of lead to air dropped significan tly beginning in the 1970s and continuing until a complete ban on lead in fuel went into e ffect in 1996. Nonetheless, as recently as the late 1980s, motor vehicle exhaust was the singl e largest source of lead emissions in the United States, resulting in the release of inorganic particulates (approximately 90% by mass) such as lead bromochloride and or ganic lead fumes (< 10% by mass) (ATSDR 1999).

Although numeric values are not available, it app ears that the percentage of total lead in the atmosphere contributed by organic lead has dropped significantly as a result of the phase-out and the eventual ban of lead in fuel in 1996. Wh en organic lead compounds are exposed to sunlight, they decompose rapidl y to trialkyl and di alkyl lead compounds. These compounds eventually decompose to inor ganic lead oxides, through a combination of photolysis and reactions with hydroxyl radi cals and ozone. The half-lives of tetraethyl and tetramethyl lead in the summer are 2 a nd 9 hours, respectively, while in the winter, both compounds have half-lives up to several days (ATSDR 1999).05/08/03 RoC Background Document for Lead and Lead Compounds

29 Investigators have measured long-range transpor t of lead from motor vehicle exhausts in populated regions to pristine areas by comparing ratios of stable lead isotopes in remote areas with the isotope ratios characteristic of l ead from industrial sources in various regions. Rosman et al . (1994a) measured lead isotopes in preserved layers of snow deposited in Greenland between 1960 and 1988 and found ratios of 206 Pb/ 207 Pb of 1.16 in the early 1960s, 1.18 in 1976, and 1.16 in th e mid 1980s. They concluded that the
elevated ratio of 206 Pb to 207 Pb indicated transport of lead from U.S. sources, particularly lead in gasoline, and they speculated that th e decrease in the 1980s was due to the switch to unleaded gasoline for motor vehicles. In another study, the ratios of lead isotopes in samples from Antarctica in the 1980s indica ted that the lead pr obably was from South America (Rosman et al. 1994b)

.

Releases of airborne lead also occur during smelting, th e manufacture of goods, and the incineration of municipal and medical wa stes (ATSDR 1999). The largest of these sources is waste incineration; however, the contribution from this source is significantly
less than the environmental release of lead to landfill (see Section 2.4.3). This is because
the amount of lead in incinerated waste is le ss than that released to landfills and because
not all of the lead in incinera ted waste is released to air.

EPA’s Toxics Release Inventory (TRI) estima ted a release of 354,065 lb of lead from 832 facilities and 1,224,315 lb of lead compounds fr om 1,045 facilities to air in 1999 in the United States (TRI99 2001). However, the TR I data are not exhaustive and should be used with caution, as only certain types of facilities are required to report releases. The
June 2000 edition of EPA’s National Toxics Inventory (NTI) estimated that 5,253,736 lb of lead compounds were released into ai r in 1996 (EPA 2000). The NTI draws on data from the TRI, state and local agencies, and EPA databases.

2.4.2 Water

Lead enters groundwater from natural weathering of rocks and soil, indirectly from atmospheric fallout, and dire ctly from industrial sources . In water, organic lead compounds undergo photolysis and volatilization. Degradation processes convert trialkyl lead to dialkyl lead and then to inorga nic lead compounds (ATSDR 1999). EPA’s TRI estimated that in 1999, 8,368 lb of lead from 832 facilities and 65,600 lb of lead compounds from 1,045 facilities were released to surface water in the United States (TRI99 2001). The TRI data should be used with caution, since onl y certain types of facilities are required to report releases. An additional and distinct hazard to the water supply is lead piping or lead solder in older plumbing systems. Areas with a supply of soft (acidic) water are more susceptible to release of lead fr om plumbing, which can
result in levels of lead in drinking water high enough to have significant effects on human health (Lee et al. 1989).

2.4.3 Soil

The largest amount of lead released into the environment is released to land, predominantly to landfill sites. Lead-cont aining wastes result from ore production, household renovation and remediation of lead pa int, use of lead in ammunition, solder, weights, and bearing metals, and producti on of iron and steel. Although lead is now05/08/03 RoC Background Document for Lead and Lead Compounds

30 banned in motor fuels in the United States and several other count ries, organic lead compounds continue to be present or activel y deposited in the soil. Data suggest that tetraethyl and tetramethyl lead are converted to water-solu ble lead compounds in soil (ATSDR 1999). EPA’s TRI estimated a dir ect release of 10,411,207 lb of lead from 832 facilities and 311,467,762 lb of l ead compounds from 1,045 facilities to land in 1999 in the United States. An additional 13,250 lb of lead and 8,142,009 lb of lead compounds were released in 1999 by underground injec tion (TRI99 2001). The TRI data should be used with caution, as not all types of facilities are required to report releases.

2.4.4 Paint

The release of lead from pain t to the local environment dese rves mention as an important source of environmental exposure. Leaded paints were most commonly used in the United States from approximately 1870 to 1940, although they persisted as recently as the
late 1970s. Lead carbonate was the most frequently used le ad pigment, and lead oxide
and lead chromate also were common. Flaking or peeling of aging paint can be a major point source of environmental lead exposure, as well as sanding of painted surfaces during home renovation. By these processes, lead can become mobilized in dust to the air and soil. In a pooled analysis of 12 epidemiological studies, Lanphear et al . (1998)
confirmed that lead-contaminated house dust was the major source of lead exposure in children. Additionally, young children may directly ingest chips of paint containing lead (ATSDR 1999).

2.5 Environmental fate
As an element, lead is not destroyed in the environment. When emitted into the atmosphere, tetraethyl and tetramethyl lead decompose via photolysi s into trialkyl and dialkyl lead compounds and then to inorga nic lead oxides and car bonates (ATSDR 1999).
With restrictions on the use of lead in gasoline, industrial so urces now produce the majority of lead emissions in the United States , and lead in the atmos phere is primarily in
the form of lead sulfate a nd lead carbonate. Particulate lead is removed from the atmosphere by wet or dry deposition, resulti ng in its uptake by soil and water. Particle
size is a determinant of atmos pheric transport, with particle s of diameter greater than

2 μ m remaining close to the point of emission and smaller particles demonstrating greater mobility (ATSDR 1999).

The proportion of lead remaining in soluti on in surface water and groundwater generally is small, because of formation of the lo w-solubility compounds lead sulfate, lead carbonate, lead phosphate, and lead hydroxide. Le ad is held strongly in soil and does not readily transport into groundwater, except in highly acid soil. Lead is bound within soil by ion exchange and specific adsorption (A TSDR 1999). However, in one study, metallic lead in soil from shotgun pellets deposited in a lime-deficient, acidic, sandy soil was detected 20 years later in small mammals. Th is study showed that metallic lead in the environment could be transformed to a biolog ically available form and transferred up the food chain (Ma 1989).05/08/03 RoC Background Document for Lead and Lead Compounds

31 2.6 Environmental exposure
Environmental exposure to lead results in absorption of lead into the body via inhalation, via ingestion, and, to a limited extent, through the skin. The most efficient exposure route generally is inhalation; the proportion of i nhaled lead absorbed in to the bloodstream is believed to range from 30% to 50%, whereas ap proximately 8% to 15% of ingested lead is absorbed (O'Flaherty 1993, Staudinger and Roth 1998). Conditions favoring high solubility result in the absorpti on of greater proportions of in haled or ingested lead into the bloodstream. Among the factors affecting the solubility of i nhaled or ingested lead are the type of lead compound involved, particle size, site of contact within the body, acidity of the body fluid contacted, and physiol ogic status of the individual (Spear et al. 1998). Compared with typical pre- industrial populations, the co ntemporary U.S. population is exposed to high levels of lead (Patterson et al. 1991), but the levels are substantially lower now than they were 30 years ago.

The most common way to measure environmen tal lead in the body is by measuring blood lead levels. Venous blood is usually anal yzed by AAS or ASV (see Section 2.3.5), and the results commonly are re ported as micrograms per deciliter (NRC 1993). The relationship between environmental lead exposur e, lead uptake, and blood lead levels is complex. Several models have been used to predict blood lead concentrations in individuals exposed to lead in the environment. One of th ese models, EPA’s Integrated Exposure Uptake Biokinetic Model for Lead in Children (IEUBK), allows the user to input relevant absorption parameters, such as th e fraction of lead absorbed from water, as well as intake from exposure to soil, dust, wa ter, and air, and expos ure rates. The IEUBK model calculates a complex set of equations to estimate the potential concentration of lead in the blood for a hypothetical child or population of children aged 6 months to 7 years. Because the Centers for Disease Control and Prevention (CDC) has determined

that childhood blood lead levels at or above 10 μ g/dL present risks to children’s health (see Section 2.3.10), the IEUBK model calculat es the probability that children’s blood

lead concentrations will exceed 10 μ g/dL (EPA 2002). Figure 2-3 shows the decrease in lead used in gasoline and the substantial re duction in blood lead levels from 1976 to 1980 in the U.S. population, as measured in the Second National Health and Nutrition Examination Survey (NHANES II) (NRC 1993).05/08/03 RoC Background Document for Lead and Lead Compounds

32 Figure 2-3. Lead used in gasoline and av erage blood lead levels measured in
NHANES II

Source: NRC 1993.

Air lead concentrations may be high ( > 10 μ g/m 3 ) near industrial sources such as smelters (ATSDR 1999). A 1991 survey of lead levels in U.S. urban air revealed a maximum quarterly mean concentration of approximately 0.08 μ g/m 3 (EPA 1996). Rural concentrations typically are lower, bri nging the estimated U.S. mean air lead

concentration to 0.04 μ g/m 3 in 1995 (EPA 1996). Remote sites report air lead

concentrations as low as 0.001 μ g/m 3 (Eldred and Cahill 1994).

Lead concentrations in U.S. dr inking water generally are below 5 μ g/L (ATSDR 1999). Lead pipes or soldering in the presence of corrosive water can result in water lead

concentrations above 500 μ g/L under extreme circumstances (EPA 1989). For example, in a town in Scotland, drinking water samp les showed lead levels greater than 1,000 μ g/L due to leaching of lead from the plumbing system by acidified dr inking water (Nordberg

et al . 1985). The concentration of lead in foods can range from 0.002 to 0.6 μ g/g (ATSDR 1999). The phaseout of lead-soldered cans (from 1979 to 1991) has virtually eliminated a previously signi ficant source of dietary lead.05/08/03 RoC Background Document for Lead and Lead Compounds

33 Cigarette tobacco contains lead at the level of 2 to 12 μ g per cigarette, up to 6% of which may be inhaled (WHO 1977). Smoking a pack of cigarettes (20) per day, with 12 μ g of lead per cigarette, and inhaling 6% of the smoke would result in daily exposure to 14 μ g of lead. Relatively less comm on but potentially serious e xposures are from alcoholic beverages held or served in leaded crystal, “moonshine” whiskey from leaded stills, food served or cooked in lead-glaze d containers, and lead-contain ing folk medicine remedies
and cosmetics.

The average intake of lead by inhalation is estimated at 2 μ g/day for an adult living in a U.S. urban setting (ATSDR 1999). A smoker ha s an additional intake of approximately

6 μ g/day, based on an estimated exposure of 14 μ g/day and absorption of 30% to 50% of
the inhaled lead into the bloodstream (O’Flaherty 1993). In 1990, the estimated daily intake of lead from consumption of f ood, water, and beverages was approximately

4 μ g/day for children 2 years of age and younger, 6 to 9 μ g/day for children aged 14 to
16, 6 to 9 μ g/day for adults aged 25 to 30, and 2 to 8 μ g/day for adults aged 60 to 65 (ATSDR 1999). The most common source of environmental lead exposure for young children is direct ingestion of paint chips a nd leaded dusts and soils released from aging painted surfaces (CDC 1997, Lanphear et al. 1998). This source can contribute an

additional intake of 5 μ g/day for a toddler engaging in normal hand-to-mouth activity, and significantly more for a child dem onstrating pica behavi or (ATSDR 1999).

2.7 Occupational exposure
The most common route of occupational exposure to lead is inhalation of lead fumes or leaded dusts in air and absorp tion of lead through the respiratory system. Lead also may be ingested and absorbed in the gastrointest inal tract. Absorption through the skin occurs with organic lead (Bress and Bidanset 1991) and possibly al so with the more soluble species of inorganic lead (Stauber et al. 1994). The National Institute for Occupational Safety and Health (NIOSH) has estimated that more than 3 million Americans potentially are occupationally exposed to some form of lead (Staudinger and Roth 1998). The National Occupational Exposure Survey, conducted by NIOSH between 1980 and 1983, indicated that approximatel y 25,000 workers were exposed to tetraethyl lead, 57,000 to lead oxides, 4,000 to lead chloride, and 577,000 to other species of lead (ATSDR 1999).

Many occupations and job activities have the potential for relativel y high exposures to lead (Fu and Boffetta 1995, ATSDR 1999). Thes e occupations have been broadly divided into three lead exposure categories: (1) those having ongoing high exposure, (2) those having high exposure with moderate freque ncy or ongoing intermediate exposure, and (3) those having high exposure with low fr equency or ongoing moderate exposure. Within these three categories, listed below, occupations are liste d alphabetically, and
asterisks indicate those that have been incl uded in at least one epidemiologic study of lead exposure and cancer, as summarized in Section 3 of this document. The various occupations and job activities are described briefly below.05/08/03 RoC Background Document for Lead and Lead Compounds

34 Occupational exposure to lead may occur durin g the production of lead -acid batteries, in which grids are formed either by melting lead blocks and pouring molten lead into molds or by feeding rolled sheets of lead through punch presses. A lead oxide paste also is applied into grid spaces. Batte ry-recycling workers in secondary smelters are exposed as they convert used batteries and other leaded materials to lead of varying purity. Foundry workers may be exposed to lead through h eating and casting operations or through the grinding and machining of compone nts. This type of exposure may result from work with brass and bronze alloys, which contain some lead, mostly for ease of machining. Lead chemical production involves a wide range of end products, including the lead oxide used by the lead-acid battery industr y. Production of tetraethyl and tetramethyl lead previously resulted in major occupational exposure, but tetraethyl lead has not been made in the United States since 1991 (ATSDR 1999). Lead smelter and refinery workers participate in operations such as sintering, roasting, sme lting, and drossing, resulting in exposure to lead sulfide, sulf ates, and oxides.

Leaded glassware is made by combining lead oxide compounds with molten quartz. This process results in lead fumes and dusts, a nd glassblowing is an additional avenue for potential contact with lead. Production of pigments can involve lead oxide, lead carbonate, and lead chloride. Chromate work ers are also exposed to lead chromate, acetate, and nitrate, and lead acetate and naphthenate may be involved in leaded paint Category 1: High ongoing exposure

Battery-production workers* Battery-recycling workers*

Foundry workers Lead chemical workers*

Lead smelter and refinery workers* Leaded-glass workers*

Pigment workers* Radiator-repair workers

Category 2: High exposur e, moderate frequency

Firing-range instructors House renovators

Lead miners* Newspaper printers*

Plastics workers* Rubber workers

Steel welders and cutters

Category 3: High expos ure, low frequency

Automobile-repair workers Cable-production workers

Construction workers Demolition workers

Firing-range participants Flame-solder workers

Plumbers and pipefitters Pottery-glaze producers

Ship-repair workers Stained-glass producers05/08/03 RoC Background Document for Lead and Lead Compounds

35 production. Although the use of lead pigments has been reduced in recent years, workers
continue to be involved in th eir production for specialty ap plications. Radiator repair workers are exposed to leaded dusts during radiator cleaning and to lead fumes during flame soldering. Exhaust ventilation control systems have been introduced into such repair operations with successf ul results (Tharr and Ed 1993).

Firing-range instructors, particul arly in indoor ranges, are expos ed to high levels of lead from both the lead projectile and lead styphna te used in the primer. Exposure is higher with non-jacketed pure lead bullets than w ith jacketed copper-coated bullets (Tripathi et al. 1990). The presence of leaded paints in homes built before 1978 continues to present a hazard to home renovators. Scraping, abrasive blasting, and heat-gun removal of paint in
older homes can create leaded dusts. Lead mi ners and mine workers are involved in the extraction, crushing, grinding, a nd concentration of lead. The most commonly mined lead ore is galena (87% lead by weight), follo wed by anglesite (68%) and cerussite (78%). Miners of copper and zinc also are exposed to lead. In the past, newspaper printing has been associated with lead exposure, and this exposure is reflected in the epidemiologic studies summarized in Section 3. However, w ith the emergence of computerized printing techniques, lead exposure is no longer a significant concern in this profession. Workers in the plastics and vinyl industries may be exposed to lead when it is used as a stabilizing or coloring agent. Powdered pigments, such as lead chromate, are blended with plastic pellets and heated to form some plastic produc ts. Similarly, lead has frequently been used in compounding rubber. Greater health awarenes s has led to reduction in applications of lead in plastics and rubber manufacture. Weld ers may be exposed to lead fumes resulting from gas-metal arc welding of structural steel (ATSDR 1999). Similar exposures occur
for steel cutters.

Automobile-repair workers may be exposed to lead through work around batteries and other parts, engine reconditioning, solder, a nd, until recently in the United States and several other countries, leaded gasoline. Lead continues to find application in the production of cable sheathing because of its workability, durability, and resistance to
corrosion. Construction and demolition workers are exposed to some lead through their interactions with pipes and traps, sheet lea d, solder, and (in older buildings) paint. Firingrange participants are exposed to lead in th e air, although generally in smaller quantities than firing-range instructors. Typical solder s contain 60% lead, and the high temperatures
involved in flame solder work volatilize some of this lead. Plumbers and pipefitters work with older lead pipes and copper pipes solder ed with lead. Lead oxide and other lead compounds have been used in the making of pottery glaze, and l ead chromate may be used in decorative coatings. Ship-repair wo rkers involved with cutting and welding steel carry a risk of lead exposure . Additionally, leaded coatings and paints have been applied to ships to prevent corrosion and inhibit th e growth of marine life. Stained-glass producers use lead strips (no l onger pure lead, but alloys) to form joints, and soldering is a common procedure.

Air lead concentration may be monitored as a means of measuring occupational exposure in work areas. However, occupational expos ure more frequently is inferred from
measurement of blood lead concentration in individual workers. Less common methods include analysis of urinary lead concentra tion, ALA level, or coproporphyrin level. Other05/08/03 RoC Background Document for Lead and Lead Compounds

36 biological indices that will like ly become more prevalent in the future are measurement of serum or plasma lead concentration and in vivo bone lead concentration.

Various chemical forms of lead, or lead speci es, are present in occ upational settings. In addition to the sheer quantity of exposure, th e species of lead invol ved and the particle
sizes encountered will influence how much l ead ultimately is absorbed. In a primary smelter, for example, lead sulfide generall y is dominant, with increasing quantities of lead sulfates and oxides near furnace areas (Spear et al. 1998). Lead sulfates and lead
oxides are more soluble than lead sulfide and therefore more likely to be absorbed in the body. Likewise, smaller particles of leaded compounds in airborne dusts are absorbed more efficiently than larger particles. Particles less than 3 μ m in diameter have a higher probability of reaching the deep lung (alveo li) and being absorbed into the bloodstream (Spear et al. 1998). Because speciation and particle size distribution usually are not available from conventional analyses of e nvironmental media, these factors should be kept in mind when workplace lead expos ure data are considered (Fleming 1998).

Table 2-7 summarizes levels of occupational lead exposure from a variety of industries, expressed as air lead concentrations, as de termined from monitoring by the Occupational Safety and Health Administration (OSHA) (Froines et al. 1990). In a study of airborne lead exposures among janitorial and custodi al workers, 23 (44%) of 52 personal air samples collected had no detectable lea d. The highest exposures were during power sanding of a wooden door (36 μ g/m 3 ), melting of lead in an open ladle for plumbing repairs (26 μ g/m 3 ), removal of lead and oakum (a t ype of caulk) from a plumbing joint (13 μ g/m 3 ), and removal and folding of the plas tic sheeting used to contain dust during carpentry work (8 μ g/m 3 ) (NIOSH 1997). More extreme examples reported in the literature include mean occupational air lead concentrations as high as 1,200 μ g/m 3 for structural steel welding (Fu and Boffetta 1995), 4,470 μ g/m 3 for smelting (Fu and Boffetta 1995), and 5,400 μ g/m 3 within a storage battery plant (WHO 1977). Table 2-7 shows representative U.S. lead industry exposur e conditions in recent years. Based on the mean air lead levels presented in Table 2-7 and assuming a human occupational default
minute volume of 10 m 3 /8 h (EPA 1994), estimated lead exposure levels ranged from 1,650 to 2,000 μ g/day. These values are approxim ately 1,000 times greater than the average environmental lead exposure levels reported for adults living in U.S. urban settings (2 μ g/day) (ATSDR 1999).05/08/03 RoC Background Document for Lead and Lead Compounds

37 Table 2-7. Air lead concentrations in occupational settings, based on OSHA inspection data (1979–1985)

Industry Inspections (samples) % of Inspections w/
median air lead conc. > 50 ( μ g/m 3 ) Mean

conc. ( μ g/m 3 ) Median

conc. ( μ g/m 3 ) Maximum

conc. ( μ g/m 3 )

Storage battery plants 87 (969) 57 200 120 35,000

Brass, bronze, and copper
foundries 118 (822) 42 200 65 54,500

Primary lead
smelters 5 (72) 40 195 80 5,650

Inorganic pigment plants 25 (143) 52 175 100 4,800

Secondary
smelters 86 (718) 43 165 140 5,200

Source: Froines et al. 1990.

NIOSH (2001) summarized the results of its Health Hazard Evaluation and Technical Assistance program for occupa tional exposure to lead for the period 1994 to 1999. In this program, requests are received from employers, employees, or others, and site visits are
conducted to determine whether a health hazar d exists from exposure to a chemical or biological agent. Table 2-8 summarizes the lead concentrations measured in the personal breathing zone or in the general work ar ea of workers evaluated in a number of
industries.

Table 2-8. Air lead concentrations from NIOSH Health Hazard Evaluation and Technical Assistance Program (1994–1999)

Industry Airborne lead concentration ( μ g/m 3 ) a

Law enforcement ND to 5,910

Manufacturing and repairing ND to 495

Lead abatement and lead-bas ed paint ND to 27,000

Abrasive blasting ND to 1,800

Electric services ND to 2,300

Other 7.4 to 280

Source: NIOSH (2001).

a ND = not detected.05/08/03 RoC Background Document for Lead and Lead Compounds

38 2.8 Biological indices of exposure
Lead exposure may be assessed from a numbe r of biological indices (see Sections 2.3.5 to 2.3.10). As discussed above (see Section 2.6 ), the most common means of monitoring recent exposure to lead is measurement of bl ood lead levels. The OSHA standard requires medical surveillance if a worker is exposed to lead in air at conc entrations above the

action level of 30 μ g/m 3 for more than 30 days a year. Medical surveillance consists of testing of blood lead levels at least every six months after the initia l blood lead test. If a

worker’s blood lead concentration exceeds 40 μ g/dL, the monitoring frequency must be increased to at least every two months and may not be reduced until two consecutive tests

indicate a blood lead level below 40 μ g/dL. If a worker’s blood lead level exceeds 60

μ g/dL, the worker must be removed from the work environment until the blood lead level

falls to 40 μ g/dL (OSHA 2002). Table 2-9 shows bl ood lead concentrations measured during the 1990s in occupations with the potential for lead exposure (both high and low to moderate), as well as the average for the U.S. population, as estimated from NHANES
III. If sufficient data are avai lable for a given individual, cumulative exposure to lead may be estimated by integrating blo od lead readings over time (Fleming et al. 1997).

Table 2-9. Blood lead concentrations fr om various occupations and the general population

Population N Average blood lead concentration ( μ g/dL) Range ( μ g/dL) a Reference

General lead industry workers, Korea (1997– 1999) 798 32 (mean) 4–86 Schwartz et al. 2000

Primary smelter workers,
Sweden 100 32 (median) 5.0–47.4 Gerhardsson et al.
1993

Battery factory workers,
Finland 91 30 (mean) NR Erkkila et al. 1992

Radiator-repair workers, Colorado (1992) 63 29 (median) 6.6–94 Dalton et al. 1997

Primary smelter workers, Canada (1994) 381 23 (mean) NR Fleming et al . 1998

Carpenters, New Jersey (1991) 122 8.0 (mean) NR Smith 1995

Laborers, Iowa and Illinois (1994–1996) 80 7.6 (mean) 1.2–50 Reynolds et al. 1999

Painters, Iowa and Illinois (1994–1996) 83 5.9 (mean) 1.5–26.3 Reynolds et al. 1999

General population, U.S. (1991–1994) 13,642 2.3 (mean, ages 1 to ≥ 70)

2.1 (mean, ages 20 to 49)

3.1 (mean, ages 50 to 69) NR CDC 1997

a NR = not reported.05/08/03 RoC Background Document for Lead and Lead Compounds

39 Since 1987, CDC has sponsored the Adult Blood Lead Epidemiology and Surveillance program, which tracks cases of elevated blood lead levels in the U.S. population. Based on data from 25 states reporting during 1998 to 2001, the overall annual mean state prevalence rate for adults with blood lead levels of 25 μ g/dL or higher was 13.4 per 100,000 employed adults. In comparison, the overall rate for 1994 to 1997 was 15.2 per 100,000. Yearly rates were 13.8, 12.9, 14.3, and 12.5 for 1998, 1999, 2000, and 2001, respectively. For adults w ith blood lead levels of 40 μ g/dL or higher, the overall prevalence rate for 1998 to 2001 was 2.9 per 100,000 adults, compared with 3.9 for 1994 to 1997. Yearly rates were 3.3, 2.5, 2.9, and 2.8, for 1998, 1999, 2000, and 2001, respectively (CDC 2002).

Bone lead concentration is another biological index of exposure, one that directly reflects long-term accumulation of absorbed lead. Upwa rds of 90% of an individual’s lead body
burden is contained in bone (Barry 1975). Noninvasive meas urement of bone lead in occupationally exposed populations has some ap peal, particularly wh ere blood lead levels historically have not been well documente d. Table 2-10 summarizes recent bone lead levels in various lead-industry and refe rent non-occupationally exposed populations, measured by K α -XRF.

Table 2-10. Bone lead concentrations from various occupations and referent populations

Population Bone site N Average bone lead conc. ( μ g/g) Reference

Primary smelter workers, Canada, early hires (1994) tibia 222 58 (mean) Fleming et al . 1998

General lead industry workers, Korea (1997–1999) tibia 798 37 (mean) Schwartz et al. 2000

Battery factory workers, Finland tibia 91 21 (mean) Erkkila et al. 1992

Primary smelter workers, Canada, recent hires (1994) tibia 159 19 (mean) Fleming et al . 1998

Primary smelter workers, Sweden tibia 100 13 (median) Gerhardsson et al. 1993

Carpenters, New Jersey (1991) tibia 122 9.4 (mean) Smith 1995

Referents, Korea (1997–1999) tibia 135 5.8 (mean) Schwartz et al. 2000

Referents, Finland tibia 26 3.5 (mean) Erkkila et al. 1992

Referents, Sweden tibia 41 3.4 (median) Gerhardsson et al. 1993

Primary smelter workers, Canada, early hires (1994) calcaneus 222 103 (mean) Fleming et al . 1998

Primary smelter workers, Sweden cal caneus 100 49 (median) Gerhardsson et al. 1993

Primary smelter workers, Canada, recent hires (1994) calcaneus 159 28 (mean) Fleming et al . 1998

Referents, Sweden calcaneus 41 12 (median) Gerhardsson et al. 1993

Carpenters, New Jersey (1991) patella 22 14 (mean) Smith 199505/08/03 RoC Background Document for Lead and Lead Compounds

40 2.9 Regulations
A few of the key regulations on lead set by U.S. government agencies are summarized in Table 2-11, and a complete listing of lead regulations is provided in Appendix A.

Table 2-11. Key regulations on lead and lead compounds in the United States

Regulatory agency Lead compound Limit

OSHA inorganic lead compounds 50 μ g/m 3 in air, action level of 30 μ g/m 3

in air

Health protection goals: 40 μ g/dL blood,

30 μ g/dL blood (if intend to have children)

Consumer Product Safety
Commission all lead compounds 0.06% by weight in paints

Food and Drug
Administration all lead compounds none used in can solders

all lead compounds 0.5–3 μ g/mL (leaching standard for ceramicware), 0.5–7 μ g/mL (leaching standard for silver-plated hollowware)

EPA tetraethyl lead none added to gasoline (motor vehicles)

inorganic lead compounds none used in plumbing

all lead compounds 1.5 μ g/L in drinking water (action level)

2.10 Guidance
In 1991, CDC issued new guidelines for chil dhood blood lead levels associated with toxicity. They lowered the action level from 25 to 10 μ g/dL and implemented a multitiered, graded response that depends on measur ed lead concentrati ons. Responses range from community-level actions to reduce lead exposure to emergency medical responses (NRC 1993).

The American Conference of Governmental In dustrial Hygienists recommends threshold limit values for worker exposure to lead of 0.05 mg/m 3 for inorganic lead compounds and 0.15 mg/m 3 for lead arsenate, averaged over an 8-hour day and 40-hour workweek (ACGIH 1999). NIOSH has set a re commended exposure limit of 0.05 mg/m 3 for inorganic lead compounds and an immediatel y dangerous to life and health (IDLH) level of 100 mg/m 3 (NIOSH 1977).05/08/03 RoC Background Document for Lead and Lead Compounds

41 

## 3 Human Cancer Studies

Lead and lead compounds, in the form of i norganic lead, were cla ssified as carcinogenic to animals by IARC (1987), but the evidence at that time was deemed inadequate to demonstrate human carcinogenicity. The epid emiologic literature on lead and cancer available to IARC was limited, but this literatu re has burgeoned in the interim. A metaanalysis of the literature was conducted in 1995 (Fu and Boffetta 1995), an overview ofthe evidence accompanied two new studies in 1997 (Vainio 1997), and a further metaanalytic review was conducted in 2000 (St eenland and Boffetta 2000). Continuing themes include accuracy of classification of lead exposure, simultaneous exposure to other substances that also may be carcinogens, and control for persona l factors such as smoking. The cohort studies on workers provide a great deal of useful information; however, the ability to draw conclusions from these studies is limited by the fact that these workers almost always are exposed to multiple chemicals in the workplace. This section summarizes the findings and conclu sions of the successive IARC Working Group evaluations of lead, reviews the wide body of relevant epidemiologic studies that have appeared since the 1987 IARC review, and su mmarizes their implications for the potential relationship betw een lead and human cancer.

3.1 IARC assessments

IARC has evaluated the evidence that lead exposure may cause cancer in a series of monographs published in 1972, 1973, 1976, 1980, and 1987.

Epidemiologic evidence on lead salts was scarce at the time of the first monograph (IARC 1972). One cohort and one case-contro l study were available for review. Dingwall-Fordyce and Lane ( 1963) compared the causes of death occurring among 425 male pensioners and employees from U.K. battery plants with cause-specific rates expected for the general population. Cancer deaths showed a nonsignificant elevation overall. When urinary lead measurements were used to divide the men into three exposure categories, however, no excess of d eaths was observed in the highest exposure group (27 observed vs. 31 expected). Cerebr ovascular events were more common among these workers, indicating that the absence of an association was probably not linked to a healthy worker effect. Jecklin (1956) found no significant differences in lead concentrations of postmortem lung tissue be tween five lung cancer patients and five control subjects dying of other causes.

Tetraethyl and tetramethyl lead were c onsidered in a separate monograph (IARC 1973), but no epidemiologic evidence was cited. Similarly, no epidemiologic studies were reviewed in the monograph on lead carbamate (IARC 1976).

By the time of the 1980 IARC monograph, th ree additional studies of cancer in industrially exposed adults and three studi es of childhood cancer in offspring of industrially exposed workers were available.

Cooper and Gaffey (1975) studied battery a nd lead production workers in the United States. The mortality of a group of 7,032 lead production facility and battery plant05/08/03 RoC Background Document for Lead and Lead Compounds

42 workmen who had been employed for one or more years between 1946 and 1970, was followed through 1970. Although the lead abso rption in many of these men greatly exceeded the accepted standards (as based on ur inary and blood lead concentrations), their observed mortality by cause was comparab le to that of the general population of United States males. Updated results for th e same study population were summarized in a later IARC publication (Cooper et al . 1985), which is summarized in Section 3.2.1.1.

Robinson (1976) followed up 153 tetraethyl l ead workers matched by age and years of employment to 139 workers with no known occ upational lead exposure. The only cancers occurring in the study population were skin cancers. Seven cases of cancer occurred in the lead-exposed group, compared with four cases in the nonexposed group. The small number of cases among exposed workers, comb ined with the fact that workers who had terminated employment for any reason (pot entially including deve lopment of cancer) were not included in the cohort, ma kes the results of limited utility.

Rencher et al. (1977) compared copper mine, smelter, and concentrator workers with the general population of the state of Utah or with workers in other operations. Workers in lead-exposed operations had triple the lung can cer risk of other workers; among workers in lead-exposed operations, t hose who developed lung cancer had higher estimated lead exposure than those who did not. Because workers with lung cancer had significantly higher estimated exposure to arsenic and sulf ur dioxide, as well as lead, the observed lung cancer excess could not be di rectly attributed to lead.

The other three studie s addressed paternal occupations and chil dhood cancer. Fabia and Thuy (1974) compared the occupational categor ies of parents of children dying of cancer with those of children dying of other cause s. Hydrocarbon-related occupations, such as motor-vehicle mechanic, machinist, miner, and painter, and potential exposure to lead in the course of tetraethyl lead production were significantly as sociated with cancer in the workers’ children.. A similar study by Hakulinen et al. (1976) found no association between hydrocarbon-related occupations a nd childhood cancer. Neither study measured lead exposure specifically and, thus, are not included in the summary table. Kantor et al

. (1979) compared 149 Wilms’ tumor cases with age, gender, and race-matched controls. More fathers of Wilms’ tumor patients th an of control subjec ts had lead-related occupations (22 vs. 6) or hydrocarbon-re lated occupations (22 vs. 10). Exposure
assessment was derived from death certifi cate occupation listings ; the IARC review
concluded that the criteria used to iden tify lead-related jobs were questionable, potentially compromising the vali dity of all three studies.

IARC’s 1987 update included a follow-up of one previous study and four new cohort studies of smelter, battery, or tetraethyl lead workers. Cooper et al . (1985) followed up 6,819 U.S. battery and lead production workers from 1947 to 1980, updating the earlier Cooper and Gaffey (1975) study. Compared with national rates, standardized mortality ratios (SMRs) were significantly elevated for all cancers (SMR = 1.13, 95% confidence interval [CI] = 1.02 to 1.26) and all respir atory cancers (SMR = 1.24, 95% CI = 1.03 to 1.49) in battery production workers. Among mo re site-specific cancers, significant excesses were found of stomach cancer (SMR = 1.68, 95% CI = 1.16 to 2.35) and lung, tracheal, or broncheal can cer (SMR = 1.24, 95% CI = 1.02 to 1.50). Nonsignificant05/08/03 RoC Background Document for Lead and Lead Compounds

43 excesses of liver and laryngeal cancers we re observed, whereas the SMR for kidney cancer was nonsignificantly depressed. Nephr itis and “ill-defined conditions” also showed significant ex cesses. Among lead production wo rkers, nonsignificant excesses occurred for digestive and respiratory can cer, and no excesses were noted for kidney, brain, or lymphopoeitic system cancer. Cancer mo rtality did not increase with duration of employment. Lack of detailed exposure info rmation precluded quantitative evaluation except by years of exposure. Concomitant e xposures to other compounds could not be controlled for, and these exposures are likely to be most intense among lead production workers. As lead production workers showed lower SMRs than battery workers, any bias resulting from lack of control for other exposures probably made it more difficult to observe an effect. No data on smoking, di et, or other potential non-occupational risk factors were available. Nevertheless, the la rge sample size made this study one of the most important studies of lead-exposed workers to date.

Malcolm and Barnett (1982) studied a cohor t of 1,898 United Kingdom lead-acid battery workers. A non-significant excess of mortality from all cancers was mainly restricted to the most highly lead-exposed workers. The onl y significant excess in cancer at a specific site was for digestive cancers (21 observe d, 13 expected) in non-e xposed workers. The authors noted that blood lead monitoring indi cated that by the end of follow-up, most of
the difference between the moderate- a nd high-exposure groups had disappeared. However, the most critical exposure period w ould have been earlier in the period from 1925 to 1976, so the decline in exposure am ong the high-exposure group probably did not have much effect on the results. Sweeney et al . (1986) compared TEL-exposed workers at a U.S. chemical plant with th e national population, obs erving an excess of respiratory cancer (15 observed vs. 11 e xpected) and brain can cer (3 observed vs. 1.6 expected) for white males. No excesses we re observed for other cancers. The study was limited by its small size and the possiblity of a healthy-worker bias (total mortality = 131, vs. 167 expected).

Smelter workers were studied by Selevan et al . (1985) in the United States and
Gerhardsson et al . (1986) in Sweden. As both studies have been updated in the interim,
their results are addressed below.

Summarizing the evidence through its 1987 upda te, IARC cited the small excesses of respiratory cancer and potential confounding by smoking or exposure to other substances, such as arsenic, and again concluded that the epidemiologic eviden ce for carcinogenicity in humans was inadequate.

3.2 Studies published since 1987 or no t included in the IARC update
Since the IARC update, an additional 17 case- control and 17 cohort studies of lead exposure and cancer have been identified (i ncluding analyses on ne w populations as well as extensions of follow-up or case-contro l investigations on previously studied populations), in addition to several subanaly ses based on elements of these new studies. Seven new studies of parent al lead exposure and childhood cancer also have been published. These additional works are discus sed below, organized by study design and type of population investigated.05/08/03 RoC Background Document for Lead and Lead Compounds

44 Most studies focus on exposure through occ upational sources, where the most intense exposure to lead can be expected. This expos ure predominantly involves inorganic lead species. Studies focused on occupations with the greatest potential for inorganic lead exposure are considered first. Among these are smelter and battery-plant workers, along with leaded-pigment workers. Glass worker s also may experience considerable exposure in production of leaded glass or, to a lesser degree, in th e manufacture of stained glass with leaded joints or lead-containing coa tings. Lead miners have the potential for substantial lead exposure, but generally to a lesser degree th an smelter, battery, pigment, or leaded-glass workers. Newsprint workers, particularly compos itors and typesetters, have had substantial exposure potential in the past, alt hough current printing technologies have largely eliminated lead exposure in th ese occupations. Many other occupations have not been the object of a specific study, despit e the fact that they may entail some degree of inorganic lead exposure; foremost am ong these occupations are radiator-repair workers, followed by steel welders and cutte rs. Examples of other potentially exposed occupations include some plas tic and rubber industry worker s, firing-range instructors, and building renovation and construction workers. Finally, in contrast to most job-related exposures, the manufacture of tetraethyl lead provides a potentially major source of exposure to organic lead. Detailed inform ation regarding sources and magnitudes of occupational lead exposure can be found in Sections 2.7 and 2.8.

Many occupations with potential for exposure to lead involve exposure to lead oxides but also are likely to involve exposure to multiple lead species (see Sections 1, 2, and 3.2). For the most part, good data on the relative cont ributions of different species or different particle sizes are not availabl e for occupationally exposed individuals, and even when job exposure histories are availabl e, classification into a few ordinal categories of exposure often is not entirely reliable. This limitati on precludes assignment of risk estimates to specific inorganic lead species in the curre nt review. Section 3.2.1 discusses studies not yet reviewed by IARC; these studies address ca ncers in adults in specific occupational groups exposed to inorganic lead. Groups ar e discussed in approximately descending order of potential exposure. Within these groups, cohort studies are described first, followed by case-control studies.

Section 3.2.2 discusses studies of mixed occupational groups, again progressing from cohort to case-control designs . Section 3.2.3 discusses studie s of TEL workers. Section 3.2.4 discusses studies based on the general population, rather than on occupationally exposed persons. Finally, Section 3.2.5 discu sses studies of childhood cancer in relation to parental lead exposure.

3.2.1 Studies of adult cancer focused on specific occupational groups

Although the ensuing discussion addresses st udies not already reviewed by IARC, a comprehensive listing of studies addressing th e association between lead and cancer is presented in Table 3-1 to pr ovide an overview of the curr ently available literature. Studies are organized according to the occupational group of focus (e.g., smelter workers) in approximately descending order of exposure. For each grouping, all available studies conducted on a specific population are listed, subdivided by study design. Many populations have been the subj ect of more than one study. Thus, for example, workers at the same British battery factory have been the focus of two cohort studies (Dingwall-05/08/03 RoC Background Document for Lead and Lead Compounds

45 Fordyce and Lane 1963, Malcolm and Barnett 1982) and one case-control study (Fanning 1988). Summaries of each of the studies identif ied in Table 3-1 are presented in three
additional tables. Cohort studies addressing the association between lead and cancer are summarized in Table 3-4, case-control studies in Table 3-5, and studies of parental lead exposure and childhood cancer in Table 3-6.

Table 3-1. Human epidemiologic studies of lead exposure and cancer: published studies on specific populations, by study design

Study design

Study population Cohort Nested casecontrol Case-control

Battery factory and/or smelter workers

Lead-acid battery workers (U.K.) Dingwall-Fordyce and Lane 1963, Malcolm and
Barnett 1982 Fanning 1988

Battery and lead production workers (U.S.) Cooper and Gaffey 1975, Cooper et al. 1985, Wong and Harris 2000 Cooper et al. 1989, Wong and Harris 2000 (same publication as cohort study)

Copper workers (Utah, U.S.) Rencher et al. 1977

Zinc, cadmium, and lead smelter workers (U.K.) Ades and Kazantzis
1988 Ades and Kazantzis 1988 (same publication as cohort study)

Lead smelter workers (Idaho, U.S.) Selevan et al. 1985,
Steenland et al. 1992

Copper and lead smelter workers (Sweden) Gerhardsson et al. 1995a

Copper and lead smelter workers (Sweden) (Lundström: full cohort; Englyst: sub-cohort) Gerhardsson et al. 1986,
Lundström et al. 1997, Englyst et al. 2001

Lead and zinc smelter workers (Sardinia) Cocco et al. 1996

Lead and zinc smelter workers (Sardinia, but different from
Cocco et al . 1996) Cocco et al. 1997

Pigment-plant workers

Lead and zinc pigment plant workers (U.S.) Sheffet et al. 1982

Chromate (including leadchromate) workers (U.K.) Davies 1984a, 1984b

Glass workers

Glass workers (Italy) Cordioli et al. 1987

Glass workers (Finland) Sankila et al. 199005/08/03 RoC Background Document for Lead and Lead Compounds

46 Study design

Study population Cohort Nested casecontrol Case-control

Glass workers (Sweden) Wingren and Englander
1990 Wingren and Axelson 1985, 1987, 1993

Miscellaneous workers potentially exposed to inorganic lead

Lead and zinc miners: females only (Sardinia) Cocco et al. 1994b

Lead and zinc miners: male only (Sardinia) Cocco et al. 1994a, Carta
et al. 1994

Newspaper plant workers (Italy) Bertazzi and Zocchetti
1980

Tetraethyl lead (TEL) workers

TEL workers (U.S.) Robinson 1976

TEL workers (U.S.) Fayerweather et al.
1997

TEL workers (U.S.) Sweeney et al. 1986

Mixed worker populations

Finnish workers via Cancer Registry Anttila et al. 1995 Anttila et al. 1996

Sample of deaths due to cancer vs. noncancer deaths (Illinois, U.S.) Mallin et al. 1989

Population-based cases (Canada) Risch et al. 1988

Specific cancers vs. all cancers (Canada) Siemiatycki et al.
1991

Registry-derived liver cancer
cases vs. stomach cancer or myocardial infarctions (Finland) Kauppinen et al. 1992

Brain cancer (U.S.) Cocco et al. 1998a

Central nervous system cancer (U.S.) Cocco et al. 1998b

Stomach cancer (U.S.) Cocco et al. 1999

Gliomas vs. noncancer patients (China) Hu et al. 1998

Meningiomas vs. noncancer patients (China) Hu et al. 1999

Renal-cell cancer vs. population controls (Germany) Pesch et al. 2000

NHANES II cohort mortality follow-up, general U.S. population Jemal et al. 2002, Lustberg and Silbergeld

200205/08/03 RoC Background Document for Lead and Lead Compounds

47 Study design

Study population Cohort Nested casecontrol Case-control

Laryngeal cancer among persons with no history of lead exposure (Greece) Kandiloris et al.
1997

Gall bladder cancer vs. gallstone patients (India) Shukla et al. 1998

Parental exposure and childhood cancer

Childhood acute nonlymphoblastic leukemia cases vs. population controls (U.S. and Canada) Buckley et al. 1989

Wilms’ tumor cases vs. population controls (U.S.) Kantor et al. 1979,
Wilkins and Sinks 1984a, 1984b,
Olshan et al. 1990

Children of union printers (Norway) Kristensen and Andersen
1992

3.2.1.1 Smelter and battery workers

Smelter workers have a high potential for expos ure to lead, much of it in the form of sulfides, in addition to highl y absorbable sulfates and oxides. These workers also are typically exposed to other chemical species , such as arsenic and nickel, with wellestablished carcinogenic potential. Further, qu antitative data adequate to differentiate between the magnitude of exposure to lead a nd these other potential carcinogens usually are not available. Battery plant workers sh are a high potential for lead exposure, and these plants often incl ude smelter components.

Smelter workers: cohort studies Ades and Kazantzis (1988) conducted a cohort study of lung cancer mortality among 4,393 U.K. zinc, lead, and cadmium smelter wo rkers. The SMR for the smelter workers, compared with national rates, was 1.25 (95% CI = 1.07 to 1.44), based on 182 lung cancer deaths. Most of the study, however, was devoted to a nested case-control analysis in which workers who died of lung cancer were matched to worker controls by birth date, employment start date, and death date. Cadm ium exposure levels we re quantified based on job history to determine whether cadmiu m accounted for the increased mortality; significant exposure to lead and several ot her compounds also was identified from job histories. Cadmium exposure s howed little association with lung cancer. Significant lead and arsenic exposures were associated with lung cancer mortality, whereas associations
with zinc or other substances were much w eaker. Potential effects of lead could not be separated from those of arseni c, nor could other exposures be simultaneously adjusted for, because of inadequate numbers. The resu lts are thus consistent with lead and/or arsenic potentially contributing more than cad mium or other compounds to the elevated lung cancer mortality associated with lead smelting; however, the excess mortality could be due to exposure to lead only, arseni c only, or the combination of the two.05/08/03 RoC Background Document for Lead and Lead Compounds

48 Steenland et al . (1992) monitored mortality among 1,990 U.S. male lead smelter workers employed from 1940 to 1965, with follow-up through 1988. A high-lead-exposure subgroup of 1,436 workers was identified base d on air-monitoring re cords. The total cohort showed nonsignificantly elevated standa rdized mortality ratios (SMRs) for kidney, bladder, stomach, and lung cancer mortality. The excess for kidney cancer became statistically significant when the analysis was limited to the most highly exposed members of the cohort (SMR = 2.39, 95% CI = 1.03 to 4.71), but estimates for other cancers remained similar or fell (SMR = 1.33, 95% CI = 0.48 to 2.90 for bladder cancer; SMR = 1.28, 95% CI = 0.61 to 2.34 for stom ach cancer; and SMR = 1.11, 95% CI = 0.82 to 1.47 for lung cancer). Although the excess mortality from kidney cancer was greater among workers with the highest intensity of ex posure, it did not incr ease with duration of exposure. Where elevated risks were obser ved in the general cohort, they did not consistently increase among those most exposed. Neither smoking nor coexposure to
cadmium or arsenic could be controlled for, but mon itoring data from a 1975 NIOSH survey indicated that average exposures to thes e metals in air were much less intense than exposure to lead, which averaged 3.1 mg/m 3 , compared with the current OSHA standard of 0.05 mg/m 3 . For arsenic specifically, which has b een linked to lung cancer in other studies, the cohort’s average e xposure was estimated at 14 μg/m 3 in 1975, compared with the current OSHA standard of 10 μg/m 3 . A 1996 review of studies on arsenic-exposed
worker cohorts concluded that no excess of lung cancer was found for arsenic exposures around the OSHA standard, and that where lung cancer excesses we re observed, they appeared to occur in cohorts with much higher exposures (e.g., in the hundreds of micrograms per cubic meter) (Steenland et al. 1996).

Gerhardsson et al . (1995a) extended the follow-up of male Swedish lead smelter workers begun by Gerhardsson et al. (1986), tracing cancer morb idity among 664 lead-exposed workers from 1969 to 1989. Exposed workers we re identified from records of routine blood lead monitoring, and cancer incidence was compared with that of the population of the surrounding county. The standardized inci dence ratio (SIR) for all cancers was 1.27 (95% CI = 0.91 to 1.74), based on 40 tumors. SIRs for cancers at all sp ecific sites except the brain were elevated, notab ly those for the respiratory system (SIR = 1.32, 95% CI = 0.49 to 2.88), stomach (SIR = 1.88, 95% CI = 0.39 to 5.50), and colon (SIR = 1.46, 95% CI = 0.30 to 4.28). Because of the small numbers of tumors (only 6, 3, and 3, respectively, even for the aforementioned sites) , the reliability of es timates for most sites is limited. Workers in the highest quartile of lead exposure showed further elevation in SIR for total gastrointestinal cancer (SIR = 2.34, 95% CI = 1.07 to 4.45, 9 tumors), but not respiratory cancer. Availability of blood lead measurements to confirm exposure is a key advantage of this study, along with a wo rker population likely to have much more intense exposure to lead than to other metals. However, the cases were too few for detailed exposure-response analyses. Lack of data on smoking further restricts interpretation of the results.

Cancer-specific SMRs were calculated for 1,388 production and maintenance workers
from an Italian lead and zinc sm elter followed from 1950 to 1992 by Cocco et al . (1997). Deaths from lung cancer (31), stomach cance r (14), and all canc ers (132) during 1965- 1992 were not elevated over regional rates, but those from cancer of the kidney (4), bladder (12), and brain (4) were, yielding SMRs of 1.75 (95% CI = 0.48 to 4.49), 1.4505/08/03 RoC Background Document for Lead and Lead Compounds

49 (95% CI = 0.75 to 2.53), and 2.17 (95% CI = 0.57 to 5.57), respectively. Risk of kidney cancer increased with years of exposure, wh ereas the relationship of lung cancer with years of exposure was inconsistent. Age, duration, and latency of exposure were
addressed. The numbers of deaths were sma ll for most cancers other than respiratory (33), and there was no control for smoki ng status. Although cadmium exposure was present, the levels of exposure to this metal were low. Direct lead exposure measurements were lacking, and job classificat ions were imprecise, but risk of reported lead toxicity did increase consistently with duration of employmen t. Lack of a strong association of lead exposure with mort ality from lung cancer, despite the strong association of lead smelter work with pne umoconiosis and other respiratory disease (SMR = 4.47, 95% CI = 3.37 to 5.80 for national mortality rates), may reflect certificatebased misclassification of lung cancer deaths or other problems, since the excess of pneumoconiosis presumably reflected an ex cess of silicosis, which is thought to predispose individuals to lung cancer.

In a further analysis, Cocco et al. (1996) studied Ita lian lead and zinc smelter workers whose glucose-6-phosphate dehydrogenase (G6PD) phenotype had been measured. Among all the workers, lung-cancer mortalit y was lower than expected and stomachcancer mortality higher, but these differences were based on few deaths (e.g., 2 observed vs. 0.6 expected for stomach cancer). Despite the thought that G6PD -deficient workers might be more vulnerable to the depletion of red blood cell glutathione associated with lead toxicity, mortality from cancer and from all causes wa s slightly lower among G6PDdeficient workers than among G6PD-normal workers.

Lundström et al . (1997) followed 3,979 Swedish smelter workers from 1928 to 1987.
Workers were further subdivided into thos e with high cumulative blood lead scores (mean times years exposed > 10 μ mol/L), and those exposed to “lead only” (excluding those from departments thought to have significant exposures to other potential carcinogens, such as arsenic, or little e xposure to lead). The lung cancer SMR was 2.8 (95% CI = 2.0 to 3.8) for the total cohort, 2.8 (95% CI = 1.8 to 4.5) for the high-exposure subgroup, and reportedly similar for the subgrou p exposed to lead only. With adjustment for a 15-year latency period, lung cancer SIRs likewise differed little between the total cohort and high-exposure subgroup; however, among workers with exposure to lead only, the SIR rose from 3.1 (95% CI = 1.7 to 5.2, 14 cases) for all workers to 5.1 (95% CI = 2.0 to 10.5, 7 cases) for those with the highest exposure. With a 15-year latency period,
elevated SIRs also were observed for cancer of the brain and nervous system (SIR = 1.6, 95% CI = 0.4 to 4.2) and renal pelvis, ureter , or bladder (SIR = 1.8, 95% CI = 0.8 to 3.4) among the high-exposure subgroup. Non-respiratory cancers were too infrequent (5 total) in the high-exposure lead-only subgroup for meaningful analysis. This study’s size, extensive follow-up, and ability to integrate blood-based and job-ba sed exposure indices give it unusual power. The apparent increase in cancer risk with higher cumulative lead exposure that appeared when workers thought to be potentially exposed to other metals, such as arsenic and nickel, were excluded al so appeared to strengthen the evidence for a specific link between lead and respirator y cancer. A subsequent study by Englyst et al

. (2001), however, cast doubt on the ef ficacy of the “lead only” grouping.05/08/03 RoC Background Document for Lead and Lead Compounds

50 Englyst et al . (2001) conducted additional analyses on one element of the Lundström et al . (1997) cohort. A total of 1,093 workers fr om the smelter’s lead department was followed up through 1997. Significantly elevated lung cancer SIRs were observed in all subcohorts, including the subcohort who had ne ver worked in arsenic-exposed areas (SIR = 3.6, 95% CI = 1.2 to 8.3, [5 cases]). This subcohort is the same as the “lead-only” subgroup evaluated by Lundström et al . A review of detailed job histories obtained for all workers with lung cancer, however, indicated that 13 of the 15 had “considerable” exposure to arsenic as well as lead, includi ng all but 1 in the “l ead only” subcohort.

Combined smelter and battery workers: cohort study Wong and Harris (2000) presented a further updat e of the U.S. lead battery and smelter worker cohort last reported on by Cooper et al . (1985) and described in Section 3.1. [Lead production workers sometimes are referred to as smelter workers (Cooper et al. 1985)]. The updated study extended follow-up for an additional 15 years, through 1995, although employment history was not updated. The SMR for cancer of the lung, trachea, or bronchus among battery workers fell from 1.2 4 in the earlier analysis to 1.14 (95% CI = 0.99 to 1.30) in the update, narrowly missing st atistical signific ance; among smelter workers, this finding was para lleled by change from a nearly identical SMR of 1.25 in the earlier analysis to 1.22 (95% CI = 1.00 to 1.47) in the update. The stomach cancer SMR remained significantly elevated at 1.53 ( 95% CI = 1.12 to 2.05) among battery workers and less elevated (SMR = 1.33, 95% CI = 0.75 to 2.20) among smelter workers. The only other cancer with a significantly elevated SMR was that of the thyroid for battery and smelter workers combined (SMR of 3.08; 95% CI = 1.33 to 6.07). Cancer mortality did not increase with earlier year of hire for lung, stomach, or thyroid cancer. Lung and stomach cancer mortality peaked among workers with 10 to 19 years of factory employment and declined with longer empl oyment duration. Thyr oid cancer mortality occurred exclusively among workers with 20 or more years of exposure. As noted regarding the earlier st udy of this cohort, concomitant exposures to other compounds could not be controlled for, but as these were likely to be most intense among lead production workers, whose SMRs were similar to or lower than those for battery workers, any bias resulting from such exposure proba bly was toward the null. No data were available to assess the possible role of sm oking, diet, or other pot ential non-oc cupational
risk factors in the results.

A nested case-control analysis of this cohort also was car ried out for stomach cancer mortality at the largest ba ttery plant (as discussed below). It found no evidence of increased lead exposure among workers who died of cancer and no consistent increase in ORs with increasing exposure. This finding argue s against a truly causal role for lead in the SMR results, although the study did not adju st for potential conf ounders. Overall, the additional follow-up maintained evidence for a modest increase in lung cancer and stomach cancer risk among the lead workers, but found no association with duration of employment and, for stomach cancer, no indica tion that workers who died of cancer had higher estimated lead exposur e than those who did not.

To explore the relationship with stomach can cer in more detail, a small nested casecontrol analysis also was conducted within the Wong and Harris (2000) cohort. Among workers employed at a Philadel phia lead battery plant, 120 c ontrols were age-matched to05/08/03 RoC Background Document for Lead and Lead Compounds

51 30 workers who died of stomach cancer. Job titl e histories were collected for each subject and used to estimate total duration of employ ment at the plant and cumulative exposure based on job-specific intensities of exposure. Neither duration of employment nor degree of estimated lead exposure was elevated am ong the workers who died of stomach cancer; in fact, these measures were higher am ong controls, although the differences did not approach statistical significance. No expos ure-dependent associations were observed across quartiles of lead exposure, regardle ss of whether exposure was computed over a 10- or 20-year period before death. Apparent ly, few data were av ailable on potential confounders. Italian and Irish immigrants we re more common among case than control subjects. The authors speculated that in view of higher stomach cancer mortality rates among native Italians and Irish than the general U.S. population, confounding by immigrant status may have been at least partly responsible for the elevated SMR observed in the lead smelter and battery wo rker cohort. However, the proportions of immigrants in the lead battery plant were not compared with those expected in the corresponding general populati on. (A previous nested anal ysis, apparently including many of the same cases, with similarly negative findings, was published by Cooper et al

. [1989]).

Battery and other workers: case-control study Fanning (1988) studied deaths due to sp ecific cancer types among battery and other factory workers in the Un ited Kingdom from 1926 to 1985. High to moderate lead exposure resulted in ORs for lung and digest ive cancer of 0.93 and 1.13, respectively, with the latter elevation due mainly to stomach cancer (OR = 1.34). No ORs reached nominal statistical significance, and no associ ations were noted for other cancer types. The excess of digestive cancer deaths was restricted to the 19 26 to 1965 period, during which lead exposures would have been most intense. ORs for other cancers did not vary by period. Because each cancer case group was compared with a control group consisting of subjects who died from all other causes, in cluding other cancers, ORs would have been
biased downward if some of these other deat hs also were lead-related. However, most
deaths were due to nonmali gnant respiratory or circulatory diseases other than hypertension, which mitigated the po tential impact of such a bias.

3.2.1.2 Leaded pigment workers

Leaded pigment manufacture also carries gr eat potential for exposure to lead compounds, which may include carbonates, nitrates, a nd acetates, among others. The key cohorts
studied were involved in the manufacture of lead chromate, and thus were potentially coexposed to chromate, an established carcinogen.

Pigment workers: cohort studies Sheffet et al . (1982) computed age- and calenda r-year-specific SMRs for 1,946 workers at a U.S. lead and zinc chromate pigment plant vs. the national population. Lung, stomach, and pancreatic cancer SMRs for chro mate workers were significantly elevated when persons of unknown vital status were a ssumed to be alive at the end of follow-up. When persons of unknown vital status were excluded, only the elevation for lung cancer remained significant (SMR = 1.6 in both whites and blacks, P < 0.05 in whites only). Nonsignificant elevations were found for stom ach, rectal, pancreatic, and prostate cancer and Hodgkin’s disease, and defi cits in intestinal and la ryngeal cancer were observed05/08/03 RoC Background Document for Lead and Lead Compounds

52 among whites. Similar results for stomach, lar yngeal, and pancreatic cancer were found
in nonwhites. All but one of the lung cancers among workers of known smoking status occurred among smokers, indicating that if expos ure to lead affects lung cancer risk, it does not do so independently of cigarette smoki ng. The relative degrees of lead and zinc chromate exposure were not determined, nor could coexposure to nickel and other compounds be controlled for. On the other hand, the presence of multiple coexposures
would tend to make a true association w ith lead chromate harder to detect.

Davies (1984a) studied 1,152 U.K. chromate pigment factory workers. A significant excess of lung cancer deaths were observed among these workers, but only for the two
factories with combined zinc and lead ch romate exposure. Excess lung cancer deaths were noted among workers exposed to both lead and zinc chromate, but not among workers exposed to lead chromate only. In a follow-up of 57 pigment factory workers who had been diagnosed with non-fatal lead poisoning (Davies 1984b), a small excess of lung cancer deaths was found (RR 1.45), but the number of deaths (4) was too small for statistical significance.

3.2.1.3 Glass workers

Leaded-glass workers, particularly those involved in glassblowing, constitute another potentially heavily exposed group, with l ead oxides and dust prominent among the species involved. As with smelter workers, however, arsenic is a common coexposure, and antimony, silica, or even asbestos exposure may occur as well.

Glass workers: cohort studies Three European studies followed up c ohorts of glass workers. Cordioli et al . (1987) studied 468 Italian glass workers. Workers pr oducing low-quality glas s containers were classified as being exposed to lead. A sm all elevation in mortality from all cancer (SMR = 1.3, 95% CI = 0.8 to 1.8) among glass workers was driven by significant excesses in lung cancer (SMR = 2.1, 95% CI = 1.1 to 3.6) and laryngeal cancer (SMR = 4.5, 95% CI = 1.2 to 11.4). The small number of deaths among exposed workers (28 total, 13 lung, and 4 laryngeal cancer) limite d the study’s statisti cal power. Sankila et al . (1990) compared the incidence of cancer in 1,803 male and 1,946 female Finnish glass workers with that of the national populati on. Glassblowers were considered to be a lead-exposed subgroup. Modest el evations in lung cancer ri sk were observed among glass workers for both men (SIR = 1.3, 95% CI = 1.0 to 1.7) and women (SIR = 1.1, 95% CI = 0.5 to 2.3); no increase was observed for other cancers, and the increased risk of lung cancer was not specific to glassblowers. In the final study, Wingren and Englander (1990) compared mortality in Swedish glass wo rkers from work areas with airborne lead levels ranging from < 0.001 up to 0.110 mg of Pb/m 3 , noting a significant elevation for pharyngeal cancer (SMR = 9.9, 95% CI = 1.2 to 36.1) and nonsi gnificant elevations for lung and colon cancer compar ed to national rates.

Glassworkers: case-control studies Wingren and Axelson (1985, 1987, 1993) conducted a case-control analysis comparing stomach, colon, and lung cancer mortality among Swedish glass workers with that of the surrounding regional populations. A small early study of three parishes (Wingren and Axelson 1985) was expanded to include 11 parishes, thus encompassing most of the05/08/03 RoC Background Document for Lead and Lead Compounds

53 Swedish glass-work industry (Wingren and Axelson 1987). For the final analyses (Wingren and Axelson 1993), total lead exposur e was estimated, based on work histories, and characterized as “none,” “low,” or “h igh.” Because of the complex pattern of exposure of glass workers to metals and othe r agents over time, data on the consumption
of metals linked with any particular type of producti on were obtained by means of a questionnaire submitted to 13 glass works in op eration at that time, 7 of which provided answers. These metals were antimony, arse nic, cadmium, chromium, copper, lead, manganese, nickel, selenium, and zinc.

ORs for mortality from cancer of the lung (OR = 1.7, 90% CI = 1.1 to 2.5), stomach (OR = 1.5, 90% CI = 1.1 to 2.0), and colon (OR = 1.6, 90% CI = 1.0 to 2.5) all were elevated among glass workers as a whole (Wingren and Axelson 1987). Among specific classes of glass workers, glassblowers had the highest ORs (2.3, 2.6, and 3.1 for lung, stomach, and colon cancer, respectively). When the data were analyzed according to estimated level of metal exposure, no cons istent dose-response trend was found for lung cancer, and the association with stomach cancer was weaker for lead than for arsenic, copper, and other metals. Increasing exposure to either lead or antimony was associated with increased risk of colon cancer mortality; however, exposure to the two elements was strongly correlated. Elevated ca rdiovascular disease mortality in the population indicated a generally poor health experi ence. For all three cancers, th e highest ORs were seen for glassblowers, who had potentially much higher inhalation exposure to manganese, chromium, and nickel than to lead. In additi on to the presence of multiple exposures (e.g., chromium, nickel, and arsenic), the study di d not control for other factors such as smoking and diet.

3.2.1.4 Miners: cohort studies

Lead miners obviously are subject to lead expos ure, but copper and zi nc miners also may experience secondary exposure to lead. The probability of e xposure to other dusts and to radon greatly complicates the evaluation of pot ential associations be tween lead exposure and lung or other cancers in miners.

Three papers described studies on Sardinian l ead-, zinc-, and silica- exposed miners. Carta

et al . (1994) and Cocco et al . (1994a) followed 1,741 male workers from two mines. SMRs based on age- and calendar-year-specifi c regional rates were not increased for mortality from all cancers (SMR = 0.94, 95% CI = 0.83 to 1.05). A significant excess (SMR = 3.67, 95% CI = 1.35 to 7.98) was seen fo r cancer of peritoneal tissues, based on6 deaths. Mortality from prostate, bladder, kidney, and nervous-system cancer and nonHodgkin’s lymphoma showed small excesses. A ll workers were subject to zinc exposure and either high silica or high radon-daughter exposure, and smoking was not controlled for. Among 526 female workers from the same mines, Cocco et al . (1994b) found a significant increase in liver cancer mortalit y (SMR = 5.02, 95% CI = 1.62 to 11.70) and a nonsignificant increase in lung cancer mo rtality (SMR = 2.32, 95% CI = 0.85 to 5.05). SMRs for other cancers were below unity. The excess lung cancer mortality was not
restricted to workers with high radon-daughter or silica e xposure, but was based on small
numbers.05/08/03 RoC Background Document for Lead and Lead Compounds

54 3.2.1.5 Newspaper plant workers: cohort study

Bertazzi and Zoccheti (1980) st udied Italian newspaper pl ant workers, singling out compositors and stereotypers as having l ead-exposed jobs. Mortality among workers from 1956 to 1975 was compared with national rates. Newspaper workers as a whole had
elevated risk estimates for all cancer (SMR = 1.23, 95% CI = 0.92 to 1.62), digestivesystem cancer (SMR = 1.20, 95% CI = 0.72 to 1.88), and respiratory-system cancer (SMR = 1.56, 95% CI = 0.91 to 2.50) and for lung cancer specifically (SMR = 1.48, 95% CI = 0.79 to 2.53). No elevated risks were obs erved for compositors and stereotypers, but these estimates were based on a total of only 4 deaths from cancer of any types.

3.2.2 Studies of mixed occupational groups

Summaries of the cohort and case-control studies described below are provided in Tables 3-4 and 3-5, respectively.

3.2.2.1 Mixed workers: cohort and nested case-control studies

Anttila et al . (1995) linked 20,700 Finnish workers whose blood lead was monitored during 1973 to 1983 by the Finnish Institute of Occupational Health to the Finnish Cancer Registry. Exposure was subdivided according to highest peak blood level measured: low (0 to 0.9 μ mol/L [0 to 18.6 μ g/dL]), moderate (1.0 to 1.9 μ mol/L [20.7 to

39.4 μ g/dL]), and high (2.0 to 7.8 μ mol/L [41.4 to 161.6 μ g/dL]). The total cohort showed no elevation in total or site-specific cancer mortality, based on an SMR analysis. Among male workers with moderate exposure, incidence of total re spiratory cancer and lung cancer both were elevated (SIR = 1.4, 95% CI = 1.0 to 1.9 for both). Risks of total digestive, stomach, bladder, and nervous-sys tem cancer also were modestly elevated. However, risks did not increase in the high- exposure group. Risks of mortality for all cancer for both men and women (RR = 1.4, 95% CI = 1.1 to 1.8) and lung or tracheal cancer (RR = 2.0, 95% CI = 1.2 to 3.2) were ev en stronger when a person-year analysis was applied to compare workers with moderate lead exposure to those with low exposure. Again, risks did not increase in the hi ghest exposure group. This exposure group was smaller than the others, however, which limite d the power of analys es specific for high exposure workers. Thus, for example, the numbers of lung or tracheal cancer deaths among men in the low-, moderate-, and high-exposure groups were 25, 34, and 11, respectively, for the person-year-based analyses.

It should be noted that for cancer, cumulativ e exposure, particular ly during the earlier part of the follow-up period, might be more relevant than peak exposure, although the two were reportedly highly correlated ( r = 0.8) in the Finnish workers (Anttila et al. 1995). Case-referent substudies of lung cancer used different exposur e criteria (Anttila et al. 1995). ORs increased most c onsistently with increasing cumulative exposure to lead. Among histologic subtypes, significantly elevat ed risk for squamous-cell cancer of the lung (OR = 4.1, 95% CI = 1.1 to 15) for the highest blood lead gr oup persisted after adjustment for smoking, although with additi onal adjustment for engine exhaust and solvent exposure, the risk d eclined (OR = 3.4, 95% CI = 0.9 to 13). Results for female workers are not considered, as too few cancers (3 total) occurred to permit meaningful conclusions. Although the follow-up period wa s relatively short, the lung cancer association was analyzed in much greater detail than in most studies, and smoking was05/08/03 RoC Background Document for Lead and Lead Compounds

55 adjusted for. Although the a ssociation between lead expos ure and lung cancer weakened with control for engine exhaust and solvent exposure, the OR remained well above 1. The highest OR of all was observed for estimat ed risk of lung cancer among workers with peak blood lead levels of at least 0.8 μ mol/L [ ≥ 16.6 μ g/dL] who were exposed to engine exhaust (OR = 14.9, 95% CI = 1.3 to 178, 11 cases). If engine exhaust was acting as an effect modifier, directly controlling for it mi ght not have been appropriate. The exhaust
could have served as a sour ce of organic lead, as well.

Anttila et al . (1996) presented a nested case-control analysis of 26 Finnish male workers with central nervous system (CNS) cancer and 200 controls, using the same Finnish occupational cohort as in Anttila et al . (1995). Detailed occupationa l histories and data on other potential risk factors were obtained fr om cancer patients or next of kin. For CNS cancer incidence, ORs rose with increasing peak lifetime blood lead level; however, the trend was not statistically significant. An a ssociation with mortality was confined to glioma. ORs for glioma mortality rose consiste ntly and significantly with increasing peak and mean blood lead level, as well as durati on of and estimated cumulative lead exposure (e.g., for low, medium, and high cumulative lead exposure vs. no exposure, ORs = 2.0, 6.2, and 12, respectively, with a trend significant at P = 0.02). Adjustment for exposure to gasoline, cadmium, and other potential risk f actors did not alter the results. Strengths of this study are the availability of blood lead measurements and control for reported cadmium and gasoline exposure. Limitations include the small number of cases (10 gliomas among workers with complete exposure information), short follow-up time (maximum of 15 years), potential selection bi as due to low response rates (60% for cases, 56% for controls), and possible coexposures such as solvents or other metals.

3.2.2.2 Mixed workers: case-control studies

Mallin et al . (1989) used death certificates for Il linois males to compare deaths from seven specific cancers with a control group of 3,198 randomly selected deaths from other causes. Based on occupations from death certif icates, the OR for cance r of the brain (3.0,

P < 0.05) was significantly elevated in white male glass workers (as well as physicians and communications workers). No significant association was observed for other cancer sites, including lung and stomac h. This isolated association is not consistent with the results for Swedish glass workers summarized above. No specific information on lead exposure other than the decedent’s occupation was available, and the analyses were not
controlled for other established or potential risk factors.

Risch et al . (1988) compared 826 Canadian men with histologically confirmed bladder cancer with 792 Canadian population controls. Reported occupational exposure to lead yielded a significantly elevated smoking-ad justed OR (2.0, 95% CI = 1.2 to 3.5) and a significant trend with duration of exposure . Of 17 other exposures examined, only one (tar and asphalt) was significantly associ ated with bladder cancer. Although these analyses relied on self -reported exposure, with the potential for inaccurate recall, this study design would be more like ly to bias results toward th e null than toward a positive association. The ability to control for smoki ng, education, ethnicity, and other factors are strength of the study; howeve r, although no multivariate an alyses adjusting for other occupational exposures were conducted.05/08/03 RoC Background Document for Lead and Lead Compounds

56 Siemiatycki et al . (1991) conducted a case-control study in Canada using 3,730 cases of various histologically confirmed cancers. Occupational exposure to 293 substances, including lead, was estimated from interview data. Elevated ORs were noted for cancer of the lung (OR = 1.1, 90% CI = 0.9 to 1.4), stomach (OR = 1.2, 90% CI = 1.0 to 1.6), bladder (OR = 1.3, 90% CI = 1.0 to 1.6), a nd kidney (OR = 1.2, 90% CI = 1.0 to 1.6). Factors controlled for included age, smoking, income, ethnicity, and blue vs. white-collar occupation. No evidence for exposure-response relationships was pr esented. Significant strengths of this study are adjustment for smoking and other potential risk factors and reliance on interview-obtained exposure data, rather than estimation of exposure from
death certificates. Limitations incl ude potential confounding by the other 292 occupational exposures and low quantita tive detail regarding lead exposure.

Kauppinen et al . (1992) conducted a nested case-contro l study in Finla nd, matching 344 primary liver cancer deaths by age and ge nder to 476 stomach cancer deaths and 385 myocardial infarct deaths. E xposures were assigned based on work histories. Workers estimated to have potential lead exposure showed no elev ation in OR (0.91, 95% CI = 0.65 to 1.29). Few workers (4 in all) were deemed to have probable high cumulative exposure, limiting the power of the study, par ticularly in view of the potential-for exposure to metals, solvents, and weldi ng fumes among the worker population. Although confounding due to alcohol intake was addres sed, use of a control group with stomach cancer, which some other studies have linked to lead exposure, may have biased results toward a negative association.

The National Cancer Institute, NIOSH, and the National Center for Hea lth Statistics have assembled a database that integrates industr y, occupation, and cause of death information
from death certificates in 24 states. This re source provides a very large sample size for case-control analyses of occupational expos ures. Three studies using these data are summarized below. All analyses based on th is database share the following primary limitations: (1) no information is available on occupations or industries other than the primary one listed on the death certificate; th erefore, some truly exposed subjects will be classified as unexposed; (2) no information is available on the duration of employment in the listed occupation or industry; and (3) cause of death may be misclassified on the death certificate; in combination these limita tions will hamper accurate quantification of exposure and linkage of that exposure to out come status. The net effect of the exposure and outcome misclassifications arising from these limitations most likely would be underestimation of the strengt h of any true association.

Cocco et al . (1998a) matched all 27,060 brain cancer deaths occurring among persons aged 35 or older during 1984 to 1992 with four gender-, race-, age-, and region-matched deaths from non-malignant cause s. A job-exposure matrix was used to assign subjects to low, medium, or high probability and intens ity of exposure. Subjects were subdivided into four groups based on gender and race (w hite or African-American). Risk of brain cancer mortality increased cons istently with rising inte nsity of lead exposure among African-American men but not among the ot her three race-ge nder groups. When probability of exposure alone was examined, no consistent association was observed for any group. However, among subjects with a high probability of exposure, risk increased with increasing intensity of exposure for all groups except African-American women,05/08/03 RoC Background Document for Lead and Lead Compounds

57 who had only a single lung cancer death in the high exposure probability group. Analyses were adjusted for age, marital status, urban residence, and socioeconomic status. Work in industries associated with lead exposure, such as chemical manufacturing and metal fabrication, may involve exposure to many pot ential carcinogens in ad dition to lead, so confounding is a possibility.

Broadening the study to CNS cancer deaths, th e same research team computed ORs for specific industries and occupations rath er than particular substances (Cocco et al. 1998b).
Notable elevations of CNS mo rtality risk were seen for the newspaper printing and publishing industry (OR = 1.4, 95% CI = 1.1 to 1.8, for white males; OR = 3.1, 95% CI = 0.9 to 10.9, for African-American males); for typesetting and compositing among white males (OR = 2.0, 95% CI = 1.1 to 3.8), wh ite women (1.3, 0.4 to 3.8), and AfricanAmerican women (OR = 4.2, 95% CI = 0.6 to 30.7); and for white male plumbers and pipefitters (OR = 2.4, 95% CI = 1.1 to 5.4). Among whites of both genders, positive
associations also were found between CN S cancer and the petroleum refining and petroleum products industries. Results for groups lacking at least one significantly elevated OR ( P < 0.05) were not presented; these groups included smelter, battery and paint manufacturing, parking-garage , and service-station workers.

In the third 24-state death-certificate study, 41,957 stomach cancer deaths were matched with 83,914 deaths due to non-malignant causes (Cocco et al. 1999). A job-exposure matrix was used to assign subjects to low, medium, or high probability and intensity of exposure to lead and 11 other chemicals. ORs were adjusted for age, ethnicity, marital status, urban residence, and socioeconomic status. Elevated ratio s occurred among white women (OR = 1.53, 95% CI = 1.10 to 2.12), African-American men (OR = 1.15, 95% CI = 1.01 to 1.32), and African-American wome n (OR = 1.76, 95% CI = 0.74 to 4.16) with high probability of lead exposure. Risks in th e moderate-probability group were elevated only for African-American women (OR = 1.37, 95% CI = 0.58 to 3.21), and risk was not elevated for any exposure group among white ma les. Risk showed no consistent increase with intensity of exposure in any group. Th e absence of any association with lead exposure among the largest race-gender group, white males, is notable, as is the general
absence of association with in tensity of exposure. More cons istent elevations of ORs for stomach-cancer mortality were observed for inorganic dust and nitrosamines than for
lead.

In a Chinese hospital-based case-control study, Hu et al . (1998) compared 218 patients with histologically confirmed primary glio mas with 436 patients w ith non-neurological, nonmalignant disease, matched by age, gender, and residence. Patients were interviewed to elicit details on occupational and chemical exposures for factory and farm occupations. An OR could not be calculated for occupa tional exposure to lead because no glioma patients reported such exposure.

In a parallel study, Hu et al . (1999) compared 183 patients wi th histologically confirmed primary meningiomas with patients with non-neurological, non malignant disease, matched by age, gender, and residence. Patie nts were interviewed to elicit details on occupational and chemical exposures for factory and farm occupations. Reported occupational exposure to lead was associat ed with risk of meningioma in both men05/08/03 RoC Background Document for Lead and Lead Compounds

58 (OR = 7.20, 95% CI = 1.00 to 51.72) and wo men (OR = 5.69, 95% CI = 1.39 to 23.39). Results were adjusted for income, education, and consumption of fruits and vegetables, indicating that the increase d cancer risk was not a cons equence of lifestyle, but no attempt was made to control for other occ upational exposures. Some elevation of ORs occurred in most of the 14 occupational exposures examined, including exposure to cadmium. Exposure to two or more agents, re gardless of type, was a stronger predictor than exposure to any specific agent, suggesti ng that lead exposure may have been simply a surrogate for occupational ch emical exposure in general.

Finally, Pesch et al . (2000) investigated occupational exposure to pote ntial carcinogens among 935 Germans newly diagnosed with rena l-cell cancer and 4,298 controls selected from regional population registries and matche d by age, gender, and area of residence. Lifetime job histories and information on smoking habits and other potential risk factors were collected by interview. Cumulative expos ure to lead, as well as cadmium, solder fumes, welding fumes, and metals in general, was estimated based on previously published job exposure matrices and grouped in to four ascending categories; separate estimates of lead exposure were calculated based on British- and German-developed matrices. After adjustment for age and smoki ng, ORs for renal cancer were elevated in men (OR = 1.5, 95% CI = 1.0 to 2.3) and wome n (OR = 2.6, 95% CI = 1.2 to 5.5) with the highest lead exposure, compared with the low-exposure groups based on the British matrix. When exposure was based on the Ge rman matrix, the OR was less elevated among men (OR = 1.3, 95% CI = 0.9 to 2.0) ; no results for women were reported.
Limited indications of increased risk with increasing exposur e were reported for men but not for women. Strengths of the study are its size and population base. The primary limitation is uncertainty regarding the specifi city of the results for lead. Significant associations also were noted for exposure to cadmium, solder fumes, and organic solvents among men, for example, but no analyses atte mpting to account for other exposures were reported. It is thus unclear how much of the observed risk associated with lead exposure may be secondary to exposure to cadmium or other agents (or, more generally, to what extent the true association may be obscu red by confounding due to these exposures).

3.2.3 Studies of occupations exposed to organic lead: case-control study of TEL
workers

Fayerweather et al . (1997) studied mortality in a U.S. TEL production plant. Cases included 735 cancer deaths during 1956 to 1987 among men identified by the company’s cancer and mortality registries , excluding cases of bladder ca ncer deemed likely to have been due to benzidine or beta-naphthalami ne exposure. Controls were time-, age-, gender-, and payscale-matched plant workers who died of causes other than cancer. Cumulative exposure to TEL was derived by summi ng yearly exposure over time to yield ranks of none, low, medium, high, and very high TEL exposure. TEL exposure was associated with digestive cancers in general; most of the association was limited to very high cumulative TEL exposure (OR = 2.2, 90% CI = 1.2 to 4.0), with a weaker association for high exposure (1.3, 90% CI = 0.7 to 2.7) and no association with lower

exposures.

Among specific digestive cancers , rectal cancer showed a st rong association with everexposure to TEL (3.7, 90% CI = 1.3 to 10.2). Th e risk of rectal cancer increased with05/08/03 RoC Background Document for Lead and Lead Compounds

59 cumulative exposure; compared with no exposur e, the OR was 1.7 (90% CI = 0.4 to 8.3) for low or medium exposure and 5.1 (90% CI = 1.6 to 16.5) for high or very high exposure. The authors reported that control for smoking habits and addition of a 10-year lag increased the strength of the associati on between lead exposure and rectal-cancer mortality. Colon cancer also showed a m ild association with ever-exposure to TEL (OR = 1.3, 90% CI = 0.7 to 2.5), apparently li mited to high or very high cumulative TEL exposure (OR = 1.7, 90% CI = 0.8 to 4.0). Adjustment for smoking and exposure to nitriles did not affect the results, but restri ction to cancer of the sigmoid colon reportedly produced an exposure-response gradient (OR = 3.6, 90% CI = 0.5 to 28.0 for high exposure; no OR reported for low-to-m edium exposure). TEL exposure also was associated with mortality from Hodgkin’ s disease (OR = 2.7, 90% CI = 0.6 to 12.0), although the small number of cases (8) precl uded in-depth analysis. Results for other cancers were not presented, as they were judged to show no association with TEL exposure. Results were not sensitive to lag time and were unaffected by adjustment for smoking or exposure to aromatic amines, radioa ctive materials, or asbestos, eliminating confounding by these factors as a source of the observed association. Overall, the study found a significant relationship between TEL exposure and risk of digestive and particularly rectal cancer, not reported in previous studies of TEL-exposed workers, but did not find relationships with any of the cance rs associated with TEL or lead exposure in previous studies. The absence of associati ons with other cancers could be a consequence
of failure to include cancer deaths am ong pensioned workers or those who left employment early because of illness.

3.2.4 Cohort studies based on general population (environmental) exposures

Jemal et al . (2002) conducted the first biomarke r-based general population cohort study of lead exposure and cancer. The study employed the subsample of 3,592 white U.S. participants in NHANES II (1976 to 1980) who had undergone blood lead level determinations at time of entry. Deaths among this population were enumerated through 1992 by linkage to the National Death Index ( NDI) and Social Security Administration Death Master File, as part of the NHANES II Mortality Study.

Adjusted for age, smoking, drinking, region, year , and gender, risk of mortality from any cancer rose across quartiles of blood lead level, but this trend was not statistically significant. The trend across qua rtiles was not consistent in gender-specific analyses, although relative risks were elevated for the hi ghest quartile of blood lead level in both men and women (RR = 2.0 for men and 1.6 for women). The RR for lung cancer based on comparison of subjects with blood lead le vels above or below the median was 1.5 in the combined population, with higher risk observed among women (RR = 2.5, 95% CI = 0.7 to 8.4) than men. The highest risks were observed for cancer of the esophagus (RR = 3.7, 95% CI = 0.2 to 89), pancreas (RR = 3.6, 95% CI = 0.6 to 19.8), and stomach (RR = 2.4, 95% CI = 0.3 to 19.1); no elevations we re noted for cancers of other sites.

The lack of statistically significant results reflects the small number of deaths during follow-up, which limited the study’s power; of the nine major sites examined, the number of deaths ranged between 5 and 16 for al l sites except the lu ng. Detailed exposureresponse analyses were restricted to a ll cancers combined, although potential effects could have been strongly target-organ specifi c. In addition, the use of quartile cutpoints05/08/03 RoC Background Document for Lead and Lead Compounds

60 based on the distribution of lead concentra tions estimated for the total U.S. population resulted in relatively small numbers in th e referent group (lowest exposure quartile) for males and in the high-exposure quartile for females. Use of a biomarker provided an objective measure of lead exposure. Neve rtheless, reliance on a single blood lead measurement produces less reliable estimates than would be obtained through multiple measurements and precludes addressing tem poral changes in lead exposure over the follow-up period. Lack of control for exposure to occupational carcinogens other than lead and potential residual confounding by duration and intensity of tobacco smoking also could have biased the results, especially for men.

Lustberg and Silbergeld (2002) carried out another biomarker-based general population study based on the same NHANES II mortality cohort used by Jemal et al. (2002). This study did not exclude non-wh ites, however (thus gaini ng 524 subjects) and employed more extensive adjustment for potenti al confounding factors than the Jemal et al. (2002) analyses (i.e., education, body mass index, and exercise were include d in the regression models, although alcohol intake was not). In addition, persons with blood lead levels of

30 μ g/dL or higher were excluded in order to restrict comparisons to levels below the OSHA standard for lead exposure. Persons with levels below 10 μ g/dL served as the referent group. Survival analyses adjusted for potential confounders found a relative risk for cancer mortality of 1.5 (95% CI = 0.9 to 2.5) for those with blood lead levels of 10 to

19 μ g/dL, compared with those with levels below 10 μ g/dL, rising to 1.7 (1.0 to 2.8) for

those with levels of 20 to 29 μ g/dL. Separate analyses of lung-cancer and non-lungcancer deaths yielded estimates of increased risk for moderate- or high-exposure groups, compared with the referent populatio n, both for lung cancer and non-lung cancer. However, none of the estimates reached the P < 0.05 level of statistical significance, and the results for non-lung cancers showed no evidence of an exposure-response relationship.

As with Jemal et al. (2002), the use of a biomarker for exposure and the prospective design of the study are strengths. Its attempts to control fo r potential confounders were more extensive, and its choice of cutpoints for the referent category yielded more males in the referent group, although that group st ill included less than 20% of the study population. However, it is notable that blood lead levels rose significantly with smoking
level. The models included terms for form er smoking, current light smoking, and current heavy smoking (> 1 pack per day). Nevert heless, some degree of residual confounding due to smoking might have remained, which c ould have contributed to the estimated risk of lung cancer for the highest exposure cate gory (RR = 2.2, 95% CI = 0.8 to 6.1). Such residual confounding would have had less effect on the results for non-lung cancer. As noted regarding the other NHANES-based study, however, mortality due to cancers of
other sites was too uncommon to allow for reliable site-specific comparisons.

3.2.5 Case-control studies based on general population (environmental) exposures

Kandiloris et al . (1997) compared blood lead levels and aminolevulinic acid dehydratase activity in 26 laryngeal carci noma patients with no history of lead exposure or toxicity and 53 patients with no history of cancer fr om the same hospital. Cases and controls reportedly had comparable demographic character istics. Blood lead levels were similar,05/08/03 RoC Background Document for Lead and Lead Compounds

61 but ALAD activity was significantly lower in cancer patients. As an indicator of subclinical lead toxicity, the lower ALAD ac tivity in laryngeal can cer patients supports the authors’ hypothesis that lead exposure at subclinical levels may contribute to laryngeal cancer risk. However, the small sample and the potent ial influence of the disease process on ALAD activity make this conclusion highly speculative.

Shukla et al . (1998) examined heavy metal content in bile drawn from 38 patients with newly diagnosed, histologically confirmed gall bladder cancer and 58 patients with gallstones diagnosed at the same surgical un it, matched by geographic area within India. Bile lead concentrations were markedly highe r in patients with cancer of the gall bladder (mean ± standard error [SE] = 58.38 ± 1.76 mg/L ) than in those with gallstones (mean ± SE = 3.99 ± 0.43mg/L). Cadmium and chromium le vels also were elevated in bile from cancer patients, but not as much as lead leve ls. Exposure to metals was assumed to occur through the heavily contaminated waters comm on to the area. No attempt was made to control for the higher cadmium and chromium levels that accompanied elevated lead level. However, the fact that lead levels di ffered more dramatically than levels of other metals argues against cancer-induced perturbation of bile concen trations as the source of these results. No data on personal risk factor s or potential occupatio nal exposures to other carcinogens were collected; therefore, the possi ble contribution of such factors relative to
lead could not be established.

3.2.6 Studies of paternal lead exposure and childhood cancer

Buckley et al . (1989) compared 204 children with acute nonlymphoblastic leukemia (ANLL) with randomly selected age- and ge nder-matched local population controls in the United States and Canada. During telephone inte rviews with the parents, a questionnaire on occupational exposures, including lead, was completed. Duration of paternal exposure to lead was categorized as 0, 1 to 1,000, or > 1,000 days. Paternal lead exposure was rare, with 1 to 1,000 days’ exposure reported fo r 5 cases and 5 controls. However, all six paternal exposures of > 1,000 days occurred am ong cases. Also of interest is the strong association noted for paternal exposure to petroleum products (53 cases vs. 31 controls exposed > 1,000 days, OR = 2.4, 95% CI = 1.3 to 4.1); however, TEL exposure was not directly assessed. The small number of pa ternal lead exposures limited the study’s statistical power.

Olshan et al . (1990) matched 200 Wilms’ tumor cases in children acro ss the U.S. with population controls of the same age and area. Detailed job history data were collected
from the fathers of these children via a se lf-administered questionnaire. A NIOSH jobexposure matrix was used to estimate occ upational lead exposure. The results showed
little evidence for association of occupational lead exposure with Wilms’ tumor, although the OR for paternal lead exposure in the pos tnatal period was slight ly elevated (OR = 1.3, 95% CI = 0.6 to 2.8). These re sults contradict th e significant association with lead exposure reported by Kantor et al . (1979). It should be noted that IARC (1990) questioned the exposure assessment me thodology used in the Kantor study.

Kristensen and Andersen (1992) traced the cancer incidence in 12,440 offspring of Oslo printers’ union members through linkage w ith the Norwegian Cancer Registry. No
elevation in cancer incidence was observed for children of printers as a whole or for those05/08/03 RoC Background Document for Lead and Lead Compounds

62 with parental lead exposure. Because only 33 cancers of all types occurred, the analyses had little power and could not focus on specifi c rare cancers linked w ith lead exposure in some earlier studies, such as ANLL or Wilms’ tumor (see Table 3-6 for a summary of the
studies on childhood cancer and parental lead exposure).

3.3 Summary
The evidence for carcinogenicity is summari zed below by cancer type. Where successive
studies have been conducted on the same ba sic population, all studies of a particular cancer in those populations are considered as a whole. Th is summary also discusses results of meta-analyses by Fu and Boffetta (1995) and Steenland and Boffetta (2000). The studies included in the meta-analyses of Fu and Boffetta (1995) and Steenland and Boffetta (2000) and the cancer sites examin ed are summarized in Tables 3-2 and 3-3, respectively. It should be noted that Steen land and Boffetta (2000) calculated a fixedeffects rate ratio of 1.04 (95% CI = 1.00 to 1.09) for all cancers combined (N = 1,911) based on eight cohort studies of highly expos ed workers. Given the potential sitespecificity of lead, as well as other risk factors, however, this summary focuses on evaluating the evidence for the specific cancers that have been most strongly associated with lead exposure in published studies. Po tential differences be tween the carcinogenic potentials of organic and inorganic lead are unclear, as is the possibility of different sitespecificity for organic lead compounds. Si nce it is reasonable to consider the carcinogenicity of exposure to both inorgani c and organic lead, st udies of TEL workers are considered in this summary.

In addition to studies addressing the asso ciation between lead exposure and cancer directly, a number of investigators have asse ssed the relationship between occupational lead exposure and markers of genotoxicity. Sections 5.4 and 5.5 review the results of
these studies in detail. About half of th ese studies found indications of increased chromosomal aberrations, sister chromatid ex changes, or other genotoxicity end points among lead-exposed workers.05/08/03 RoC Background Document for Lead and Lead Compounds

63 Table 3-2. Studies included in the meta -analysis of Fu and Boffetta (1995).

Cancer site

Study Study type Lung Stomach Kidney Bladder

Ades and Kazantzis (1988) Case-control 4

Bertazzi and Zocchetti (1980) Cohort 4 4

Cooper (1989) a Case-control 4

Cooper and Gaffey (1975) a Cohort 4 4

Cooper et al. (1985) a Cohort 4 4 4

Cordioli et al. (1987) Cohort 4

Davies (1984b) Cohort 4

Fanning (1988) Case-control 4 4

Gerhardsson et al. (1986) Cohort 4 4

Goldstein et al. (1970) Cohort 4

Michaels et al. (1991) Cohort 4 4 4

Risch et al. (1988) Case-control 4

Sankila et al. (1990) Cohort 4 4 4 4

Selevan et al. (1985) b Cohort 4 4 4 4

Sheffet et al. (1982) Cohort 4 4

Siemiatycki (1991) Case-control 4 4 4 4

Steenland et al. (1992) b Cohort 4 4 4 4

Wingren and Axelson (1987) c Case-control 4 4

Wingren and Axelson (1993) c Case-control 4

Wingren and Englander (1990) Cohort 4

a Three papers by Cooper and co-workers were based on the same study population.

b Papers by Selevan et al. and Steenland et al. were based on the same study population.

c Two papers by Wingren and Axelson were based on the same study population.05/08/03 RoC Background Document for Lead and Lead Compounds

64 Table 3-3. Studies included in the meta-a nalysis of Steenland and Boffetta (2000).

Cancer site

Study All cancers Lung Stomach Kidney

Anttila et al. (1995) 4 4 4 4

Cocco et al. (1997) 4 4 4 4

Fanning (1988) 4 4 4

Gerhardsson et al. (1995a) 4 4 4 4

Lundström et al. (1997) 4 4 4 4

Steenland et al. (1992) 4 4 4 4

Wong and Harris (2000 a ) 4 4 4 4

Wong and Harris (2000 b ) 4 4 4 4

a Battery workers

b Smelter workers

3.3.1 Lung and other respiratory cancers and occupational lead exposure

Lung cancer is both the most common type of cancer and the type that has been most studied with respect to lead exposure. Fu and Boffetta ( 1995) conducted a meta-analysis
of 13 cohort and 4 case-control studies of l ead exposure and lung cancer. For studies with compatible quantitative risk estimates, a we ighted summary risk estimate across all studies was derived. Combining 15 studies (multiple papers based on the same study population were counted as one study), Fu a nd Boffetta derived a fixed-effects RR for lung cancer of 1.24 (95% CI = 1.16 to 1.33) for lead exposure. Fixed-effects models are based on the assumption of no significant hetero geneity of effect, however, and when this assumption is violated, they may produce inva lid estimates of the statistical significance of a summary estimate of effect. To account for heterogeneity, random-effects models add an extra component of variance to the usual variance calculat ed for the summary relative risk in a fixed-effects analysis. Because of significant heterogeneity across studies of lung cancer, a random-effects RR also was calculated for th e 12 studies with the requisite information for this appro ach, yielding a RR of 1.29 (95% CI = 1.10 to 1.50). A statistically significan t association between lung canc er and lead exposure thus appeared when results from the available l iterature were pooled, and it was similar in magnitude regardless of whether all 15 avai lable studies were included using a fixed effects approach or only the subset of 12 st udies meeting the requirements for the more robust summary estimate provided by a ra ndom effects approach were included. A separate random-effects estimate also was gene rated from studies of just the subset of battery and smelter workers, who were consid ered to have the highest exposure to lead. This analysis yielded a RR for lung cancer of 1.42 (95% CI = 1.05 to 1.92), consistent
with the idea that risk sh ould be greatest among the worker populations with the most

exposure.

A meta-analysis of eight occupational cohor t studies on lung cancer was published in 2000 by Steenland and Boffetta, who argued th at the occupational cohort studies05/08/03 RoC Background Document for Lead and Lead Compounds

65 provided the clearest information, because high exposure generally was documented.
Studies were limited to those in which lead was established as the predominant exposure, except for one smelter study (Lundström et al. 1997) in which arsenic exposure was appreciable and could have confounded the lead effect estimates (see the discussion of Englyst et al. 2001). The meta-analysis showed si gnificant heterogeneity due to the relatively high risk esti mate from Lundström et al. (RR = 2.9, compared with 1.14, 1.22, 1.19, 0.93, 0.82, 1.8, and 1.32 in the other seven studi es). Use of a ra ndom-effects model to account for this heterogeneity yielded a combined RR across the eight studies of 1.30 (95% CI = 1.15 to 1.46, 675 lung-can cer deaths). Excluding Lundström et al. (1997) eliminated the heterogeneity while still yieldi ng a significantly elevat ed combined RR of 1.14 (95% CI = 1.04 to 1.25) based on a fixed effects model. This parallels the findings of the earlier meta-analysis by Fu and Boffetta (1995) insofar as both random and fixed effects approaches yielded a st atistically significant associ ation between lung cancer and lead exposure. It may be argued in this inst ance that the random eff ects estimate is more meaningful since it is based on one additional study (Lundström et al. 1997) that could not validly be included in deriving the fixed effects estimate. Also of note is that the random effects RR of 1.30 is very similar in magnitude to the RR of 1.29 obtained in the earlier random effects analysis by Fu and Boffetta (1995), which had included a larger
number of studies since it di d not bar case-control designs. As a counter argument to this,
the RR of 2.9 observed in the Lundström et al. (1997) study could be viewed as an outlier, in which case the fixed effects estima te based on the subset of 7 studies might
better reflect the actual relative risk for c ohorts of lead-exposed workers as a whole. For the overview in this background document, Steenland and Simonsen re-examined the Steenland and Boffetta (2000) meta-analysis; however, no occupational studies on lead exposure and lung cancer had been p ublished since that analysis.

This review considers 36 publications of studies addressing occ upational lead exposure and lung cancer risk in 21 different populati ons. Of the 18 populations included in at least one cohort study, elevated risk estimates for le ad exposure were repo rted in 15, with the elevation reaching statistical significance in 8. Only one st udy reported a reduced risk (Cocco et al. 1997), which was not statistically si gnificant. Of the three case-control studies of populations for which no cohort an alysis was available, two (Fayerweather et al. 1997, Mallin et al. 1989) found no association between lead exposure and lung cancer, and one (Siemiatycki et al. 1991) found a weak association. The studies reviewed here include two based on TEL workers; one study found evidence of an association with respiratory cancer (Sweeney et al. 1986) and the other did not (Fayerweather et al. 1997); however, the findings did little to alter the ba sic thrust of the evidence. Overall, the picture is one of an association between lead exposure and lung cancer.

Characterization of lead expos ure for assessment of a potential link between occupational exposure and cancer should be based on the most accurate assessment possible of each individual’s exposure. The measures employed in one or more of these studies include biomarkers, ambient air measurements, job hi stories with or wit hout the use of job exposure matrices, history of employment in a given factory, and simply last known or predominant occupation. In considering the relative strengths and weaknesses of these methods, their influence on the re sults of particular studies and whether the results vary05/08/03 RoC Background Document for Lead and Lead Compounds

66 systematically with the measure used, this di scussion focuses on studies of inorganic lead exposure and on the most recent analysis of each population.

Biomarkers such as blood and urinary lead leve ls reflect lead that has been absorbed and circulated to tissues, thus eliminating vari ability in the exposure received from a given
ambient lead level due to the effects of individual physiolo gy, protective gear, workstation ventilation, and ot her factors. However, although biomarkers offer the key advantage of demonstrating whether an indivi dual has absorbed lead and to what degree, blood or urinary lead measurements may fl uctuate over time even when actual lead absorption has not changed. Integration of mu ltiple measurements over an individual’s employment history redu ces this problem.

Three occupational cohort studies (Gerhardsson et al. 1995a, Anttila et al . 1995,
Lundström et al . 1997) used extensive blood lead c oncentration data. Geometric mean blood lead levels among the Swedish smelter workers in Gerhardsson et al. and

Lundström et al . were roughly similar, declining from around 3.0 μ mol/L (62.2 μ g/dL) at

the start to 1.6 μ mol/L (33.2 μ g/dL) at the end of both st udies. Lead levels among the general Finnish worker p opulation studied by Anttila et al . were lower, declining from 1.7 (35.2 μ g/dL) to 0.7 μ mol/L (14.5 μ g/dL) over the study peri od. All three studies noted positive associations with lung cancer; th is association was statistically weakest in
the Gerhardsson et al . study, whose smaller size precluded reliable risk estimates when exposure was categorized beyond whether or not lead ever was detected in a worker’s
blood.

Dingwall-Fordyce and Lane (1963) and Wong an d Harris (2000) asse ssed urinary lead levels, although only the former based exposur e classification on this measure. Nearly half of the U.K. battery workers in the former study had levels exceeding 100 μ g/L,

consistent with the means of 130 and 170 μ g/L observed among U.S. battery and smelter workers, respectively, in the latter study. The SMR for all cancers showed no consistent increase across ascending exposure cate gories in the U.K. study, which, among the biomarker-based studies, in cluded the smallest number of monitored workers.

In the studies reviewed here, lead exposu re most commonly was estimated from job histories. Detailed job histories allow estim ation of exposure through application of a jobexposure matrix and/or rating of exposure probability by an industrial hygiene expert. In some studies, job histories were bolstered by ambient air monitoring data (Wingren and Englander 1990, Steenland et al. 1992). Other studies simply followed up workers employed in a factory or operation known to have high potential fo r lead exposure (e.g., the follow-up of lead and zinc pigment plant workers by Sheffet et al. [1982]). This approach was modified in one study that fo llowed up pigment-factory workers diagnosed with lead poisoning (Davies 1984b). Use of onl y a general occupational history, without details regarding specific types of work pe rformed, precludes categ orization of workers by risk of exposure within a given occupation. Exposure estim ates based on occupation as reported on death certificates can be expected to be the le ast reliable of the job-historybased methods, being subject to the use of nonstandardized classifi cation criteria by the person entering the occupational data and to the potential for missing previous leadexposed occupations (Mallin et al. 1989; Cocco et al. 1998a, 1998b, 1999). Further, one05/08/03 RoC Background Document for Lead and Lead Compounds

67 of these studies (Mallin et al . 1989) computed estimates for each of 30 industry and 29 occupation groupings that were not designed specifically to capture lead exposure, and presented no quantitative estimates of risk fo r groups that did not show a statistically significant associati on with lung cancer.

The studies reviewed here ge nerally found positive associati ons, of varying strengths, between lead exposure and risk of cancer ; the exception was the one study based on occupation as reported on d eath certificates (Mallin et al. 1989). Studies using blood lead levels consistently observed pos itive associations between lead and lung cancer, with risk estimates ranging from 1.32 (Gerhardsson et al. 1995a) to 2.9 (Lundstrom et al. 1997). The study using urinary lead levels yielded no consistent dose-response pattern despite an overall cancer SMR of 1.2 for battery fact ory workers (Dingwall-Fordyce and Lane 1963). Relative risk estimates from studies us ing job history in combination with ambient air or other monitoring ranged from 1.1 (Steenland et al. 1992) to 1.40 (Wingren and Englander 1990). Use of job histories alone yielded estimates of 0.82 (Cocco et al. 1997) to 2.32 (Cocco et al. 1994a) from studies that provided quantitative risk estimates. The study relying on death certificate-derived oc cupation reported no association with lung cancer for metal or glass workers, although no specific risk estimate was provided for those groups (Mallin et al . 1989). The most consistent evid ence of association thus was
seen in studies based on blood lead levels , the most objective measure of exposure, whereas no significant association was s een in the study based on the exposure assessment method with the greatest potential for misclassificati on, a death-certificatederived occupational characteriza tion that was not specifically designed to separate lead workers from metal workers in general.

Despite the relatively consistent direction of results across studies, a number of factors complicate drawing of potential causal infe rences from the available epidemiologic literature. Foremost among these complicat ions are potential confounding of lead exposure with smoking status, concomitant exposure to other carcinogens and other potential risk factors, an d insufficient data for assessment of exposure-response relationships.

The risk of lung cancer due to cigarette sm oking dwarfs that which could be expected from lead exposure based on any available ev idence. Most studies of lead exposure and lung cancer to date have lacked data on smoki ng status, and thus their results could be confounded by smoking if lead-exposed groups smoked more than unexposed groups. The potential effect of confounding by sm oking depends upon the comparison being
made. It has been estimated that the effect of confounding due to smoking in a comparison of lung cancer risk between occ upational groups and the general population is likely to be on the order of a 20% increase, that is, enough to genera te a relative risk of 1.2 or less (Siemiatycki et al. 1988, Axelson and Steenland 1988). However, when the number of persons classified as lead-exposed is small, as in many studies of lead and cancer, most or all of the exposed group c ould be smokers, resulting in a much greater effect on the relative risk. On the other hand, in studies that cont rolled for cigarette smoking, the association between lead expos ure and lung cancer remained, suggesting
that the observed associations between lead exposure and lung cancer across the studies as a whole were not due to confounding by smoking. No other known non-occupational05/08/03 RoC Background Document for Lead and Lead Compounds

68 risk factors for lung cancer are potentially as important as smoking. In studies that have controlled for such factors, they have had little impact on observe d association between lead exposure and cancer.

Concomitant exposure to othe r potential carcino gens is ubiquitous in lead-exposed populations. Improved study designs with better monitoring (e.g., use of biomarker data or detailed personal job histor y data to facilitate estimation of arsenic exposure) can address this issue to some degree, but ruli ng out the potential roles of other metals nonetheless remains a difficult problem. This problem was illustrated when part of the Swedish smelter cohort studied by Lundström et al . (1997) was reexamined; detailed examination of the job histories of lung cancer patients in one department revealed that 13 of 15 also had been significan tly exposed to arsenic (Englyst et al. 2001). Estimation of the potential effect of confounding due to other occupational carcinogens thus presents a different situation than that for smoking. Although exposure to arsenic, for example, could not be expected to incr ease a worker’s risk to the degree that heavy smoking does, it is possible that a large pr oportion of the workers in lead -exposed operations also are significantly exposed to arsenic, whereas su ch exposure might be much less common in most other operations in the same plant a nd, unlike smoking, would be relatively rare in the general population of most regions. This could result in lead -exposed workers having an estimated lung cancer risk approaching that of arsenic-exposed workers simply because of confounding by arsenic exposure. In addition, joint confounding by arsenic and other exposures could produce additive or even synergistic effects; such synergy has been proposed, for example, with smoking (Hertz-Picciotto et al. 1992).

In a review by Steenland et al. (1996), the relative risk of lung cancer was 3.7 for heavily arsenic-exposed workers from six cohorts compared with unexposed workers. Assuming
that this risk reflects the eff ect of substantial exposure to arsenic in combination with smoking and possibly contributi ons by substances such as cadmium, it appears that confounding by arsenic and/or smoking could theo retically produce risk estimates of the magnitude commonly seen for occupational lead exposure. Countering this is the observation that lead exposure shows an asso ciation with lung cancer in many different exposure contexts, including ones with mini mal potential for coexposure to arsenic, suggesting that the observed risk is to some degree due to lead exposure itself. A further consideration is the possibility that lead ma y act synergistically with other occupational carcinogens. Some evidence to support this hypot hesis is available from animal studies (e.g., Shakerin et al. 1965, Tanner and Lipsky 1984, Hiasa et al. 1983; see Section 4.2.5 for details) and in vitro experiments with direct-acting ge notoxic agents such as radiation (see Section 6.1.3.4). If so, one might expect mu ch or all of any cancer excess resulting from lead exposure to be concentrated among persons co-exposed to other carcinogens, much as Englyst et al . (2001) observed with arsenic exposure.

Most studies of lead and cancer to date ar e limited by small sample size and the lack of good quantitative exposure data, which hi nder assessment of exposure-response relationships and the ability to control for other expos ures. Where exposure-response assessment was attempted, the strongest association with lung cancer usually was seen in the highest exposure group, but a monotonic in crease with duration, intensity, or overall amount of exposure was not always observed. Th is could reflect the absence of a true05/08/03 RoC Background Document for Lead and Lead Compounds

69 monotonic response, the use of quantitative e xposure measures that may not accurately
reflect the individual’s true e xposure, or inadequate adjustme nt for other risk factors. Here, interpretation again is complicated by the general lack of adequa te statistical power to evaluate multiple exposure levels while controlling for smoking, age, gender, and other potential confounders or effect modifiers. Another factor po tentially affecting exposureresponse analyses is the possibi lity that workers who experi ence acute lead toxicity tend to drop out of the exposed worker population. This factor could lead to underestimation
of the association between lead and cancer if such an asso ciation actually exists but is most pronounced at lead exposures near or above those that cause acute toxic effects. A related concept is that subgr oups of the population that are more susceptible to leadinduced carcinogenesis because of metabolic or other differences may likewise be more susceptible to acute toxicity; thus, the higher the exposure leve l they encounter, the more likely they are to leave employment be fore the induced cancer occurs. Such a progressively greater loss of the most hi ghly susceptible subpopul ations at increasing exposure levels could blunt or distort the exposure-response curve for occupational lead exposure and cancer. The study that followed up a group of workers diagnosed with lead poisoning found an RR of 1.45 for lung cancer among that group, compared with the general population (Davies et al. 1984b), which exceeds the summary RRs of 1.14 to 1.30 obtained from meta-analyses of occupa tion cohorts (Steenland and Boffetta 2000). Nevertheless, the small numbers of lead- poisoned workers (57) and of lung cancers among those workers (4) prevent the difference between their estimated risk and that for exposed cohorts as a whole from ap proaching statistical significance.

Evidence from the totality of epidemiologic stud ies is consistent with a mild elevation in risk of lung cancer with lead exposure. In me ta-analyses, either br oadly inclusive of casecontrol and cohort studies (Fu and Boffetta 1995) or narrowly focused on studies of populations with the strongest documentation of significant lead e xposure (Steenland and Boffetta 2000), the estimated in crease in lung-cancer risk associated with lead exposure has reached statistical significance. However, the average magnitude of the increased risk observed across studies is small enough that the hypothesis of no effect cannot be definitively eliminated. It can be argued that given the modest estimated increase in risk, residual confounding due to smoking, exposure to additional occupational carcinogens, or
other factors cannot be conclusive ly ruled out as the source of the elevated risk estimate. However, in the absence of an effect threshol d, even a small real elev ation of risk due to lead exposure would have a significant impact at the population level, given the ubiquity of low-level lead exposure.

3.3.2 Stomach and general digestive cancer

In their meta-analysis, Fu and Boffetta ( 1995) combined 10 studies with a quantitative
estimate of risk to derive a fixed-effects RR of 1.33 (95% CI = 1.18 to 1.49) for lead exposure and stomach cancer. Because no signi ficant heterogeneity was apparent across studies of stomach cancer, no random-effect s RR was calculated. For battery or smelter populations, which were presumed to have the heaviest occupational ex posure to lead, an RR of 1.50 (95% CI = 1.23 to 1.83) was obtained.

In their meta-analysis of eight cohort studi es of highly exposed workers, Steenland and Boffetta (2000) found that a fixed-effects an alysis was justified by the homogeneity of05/08/03 RoC Background Document for Lead and Lead Compounds

70 risk estimates for lead exposure and st omach cancer across the studies (1.13, 1.43, 1.53, 1.33, 1.36, 0.97, 1.07, 1.88). They calculated a fixe d-effects combined RR of 1.34 (95% CI = 1.14 to 1.57, N = 181).

This overview considers 21 studi es that examined the relati onship between lead exposure and stomach cancer or digestive cancer in general.

Seven case-control studies included stomach cancer. One large study focused entirely on stomach cancer (Cocco et al. 1999), using the U.S. 24-state d eath certificate registry and finding positive associations between lead-r elated occupations and stomach cancer for black men and women and white women, but not white men. A small case-control study
of stomach cancer nested in a larger cohort found no associ ation with exposure among battery production workers (Wong and Harri s 2000). Five studies included stomach cancer as part of a series of case-control comparisons. Studies of U.K. battery workers (Fanning 1988) and Swedish glass workers (Wingren and Axelson 1993) and a large study of the Montreal population (Siemiatycki et al. 1991) found statistically significant elevations in stomach cancer with occupationa l lead exposure. Studies of Illinois males (Mallin et al. 1989) and U.S. TEL workers (Fayerweather et al. 1997) did not.

Discounting two small studies of glass workers (Cordioli et al. 1987, Wingren and Englander 1990) for inadequate case numb ers, twelve cohort studies involving ten distinct populations addressed stomach or digestive cancer and lead exposure. Of the studies of smelter workers, three found positive associ ations (Steenland et al. 1992,
Cocco et al. 1996, Wong and Harris 2000) and two found negative associations (Cocco et al. 1997, Lundström et al. 1997). A positive association was noted for U.S. (Sheffet et al. 1982) but not for U.K. (Davies 1984a, 1984b) pi gment workers. A significantly elevated
risk also was observed for a cohort of U.S. battery plant workers, compared with the general U.S. population (Wong and Harris 2000) , although the nested study including cases and controls from the largest pl ant (discussed above ) found no evidence of association with lead exposure (Wong a nd Harris 2000). A nonsignificant increase in
stomach cancer risk was observed am ong Finnish glassblowers (Sankila et al. 1990) and
Finnish workers with elevated blood lead levels (Anttila et al. 1995). No association was noted in Sardinian lead and zinc miners (Cocco et al. 1994a, 1994b). Results for stomach
cancer thus are not as consistent as those for lung cancer. Interpretation of these results is subject to the same caveats discussed above wi th respect to lung cance r, and the issue of inadequate statistical power is exacerbate d by the relative rarity of stomach cancer.

The strongest potential eviden ce for a link between lead a nd cancer would be provided by studies with clearly defined lead-specific exposures, relati vely large sample sizes, and ability to evaluate exposure- response relationships. Cocco et al. ’s (1999) case-control study is by far the largest av ailable, with nearly 42,000 st omach cancer deaths and 84,000
noncancer deaths. It also is one of the few studies to include diffe ring levels of lead exposure (based on death-certific ate-listed occupation). Furthe r, it is one of the only studies to adjust for socioeconomic status, which is inversely associated with stomach cancer. Although risks appeared elevated with high exposure among most age-race groups in this study, no elevation was observed for the largest group, white males. Anttila
et al . (1995) employed blood-based exposure indi ces, which were used to construct a05/08/03 RoC Background Document for Lead and Lead Compounds

71 large (20,700 worker) populati on-based cohort. In this st udy, lead exposure showed a positive, but not statistically significant, association with stomach cancer, with no consistent exposure-response pattern.

Surveying the epidemiologic evidence overall, a pproximately half of the relevant studies of lead and stomach cancer note a positive asso ciation of modest size. The small number of stomach cancers and infrequency of high l ead exposure in most studies limited their statistical power; the positive associations observed within particular studies thus usually were not statistically signif icant. When studies were combined through meta-analysis, however, a statistically significant estimate of increased risk across the pooled study populations was obtained (Fu and Boffetta 1995, Steenland and Boffetta 2000). Evidence of consistent exposure-response patterns is lacking, as most studies have been unable to
address this issue because of insufficient num bers and/or lack of detailed exposure data.
Most studies did not include the information needed to adjust for socioeconomic status and dietary factors such as nitrosamine exposure, which are potentially significant confounders (nitrosamine exposure, for exam ple, may reflect greater consumption of cured meats by blue-collar workers, who more likely to be lead-exposed, than by whitecollar workers, who are less likely to be lead -exposed). Common to all studies of lead exposure is the problem of concomitant exposur es to other potential carcinogens such as nickel and chromium, which few studies of stomach cancer have addressed and none has fully resolved.

3.3.3 Kidney cancer

In their meta-analysis of five studies of ki dney cancer and lead exposure, Fu and Boffetta (1995) estimated a combined RR of 1.19 ( 95% CI = 0.96 to 1.48). The RR for heavy exposure rose only slightly, to 1.26 (95% CI = 0.70 to 2.26). They concluded that an effect of lead on kidney cancer risk could not be confirme d or ruled out based on the
available evidence.

A meta-analysis of seven occupational cohor t studies of lead e xposure and kidney cancer was published in 2000 by Steenland and Boffetta. The results of the seven studies were not heterogeneous, and a fixed-effects meta-a nalysis yielded an RR of 1.01 (95% CI = 0.72 to 1.42) based on only 40 cancer deaths or cases. The RRs in the seven studies were 0.52, 0.93, 1.93, 1.75, 0.90, 0.72, and 0.80. Steenland and Simonsen recomputed this meta-analysis with the addition of the population-based case-control study by Pesch et al

. (2000). For consistency with the rest of the studies, only workers from the highest category of estimated lead exposure (“substa ntial exposure” estimated from job exposure matrices) were included. Addition of these workers did not result in sufficient heterogeneity across the eight studies to preclude a fixed- effects analysis. The fixedeffects RR with the addition of 40 kidney cancers from Pesch et al. was 1.22 (95% CI = 0.93 to 1.59). It should be cautioned that th e Pesch study, a large population-based casecontrol study, carried enormous weight in th e meta-analysis, because it included as many highly exposed cases as the remaining seven st udies, all occupationa l cohorts, combined. Despite the weight carried by this study, th e confidence interval for the combined estimated RR again included 1.0.05/08/03 RoC Background Document for Lead and Lead Compounds

72 The incidence of kidney cancer was too low to provide sufficient numbers of cases in most studies of lead exposure. Eight studi es reported results for renal cancer. Among three cohort studies of smelter workers, Steenland et al. (1992) found a significantly elevated risk based on 8 cancers among the subcohort most heavily exposed to lead.

Cocco et al . (1997) reported a positive association, but Lundström et al . (1997) did not; however, both studies’ results were based on to o few cases to be reliable. A mixed cohort of battery and smelter workers (Wong and Harris 2000) showed no increase in kidney cancer, but lead and zi nc miners did (Cocco et al. 1994a), although lead exposure was not directly quantified in the latt er group. Exposure to lead was associated with death due to kidney cancer in a case-control study base d on the population of Montreal, Canada (Siemiatycki et al. 1991) and with incident kidney cancer in a German case-control study (Pesch et al. 2000); however, peak blood lead among a cohort of Finnish workers was not
associated with increased ri sk of kidney cancer (Anttila et al. 1995). The Canadian results approached statistical significance (OR 1.2, 95 % CI = 1.0 to 1.6), and the use of other cancer deaths as a control group may have biased this estimate downward. The German study was based on the highest number of cancers by far, 935, followed by 88 for the Canadian, 10 for the Finnish, and 8 for th e lead-exposed smelter-worker study. Thus, of
the four studies with more than 5 cases in the exposed group, three observed positive associations. Nevertheless, the German study also found elevated kidney-cancer risks for other exposures, including those to cadmiu m and solder fume, none of which were
controlled for in the risk es timates for lead exposure.

The small number of kidney cancers availabl e in most studies precluded statistically definitive results, clear demonstration of exposure-response relationships, or adjustment for potentially covarying metal or other occupational exposures.

3.3.4 Bladder cancer

In their meta-analysis of five studies on bladder cancer and lead exposure, Fu and Boffetta (1995) estimated a combined RR of 1.41 (95% CI = 1.16 to 1.71). No relative risk for heavy exposure was calculated, becau se not enough battery or smelter studies included results for bladder cancer. They conc luded that while the combined risk estimate for the studies was statistically significant, th e small number of studies reporting findings for bladder cancer may have indicated that negative findings were not being published, thus biasing the results to ward a positive association.

Seven studies of bladder cancer are included in this overview. All three studies of U.S. smelter workers (Steenland et al. 1992), Sardinia (Cocco et al. 1997), and Sweden (Lundström et al. 1997) reported positive associations with lead exposure. Risk estimates ranged from 1.3 to 1.8, and deaths among the e xposed from 6 to 12; no elevated risks were statistically significan t, and no consistent exposur e-response pattern was noted.
Elevated risk of bladder can cer (SMR = 1.15) also was seen among lead and zinc miners (Cocco et al. 1994a). A borderline significant eleva tion (OR = 1.3, 95% CI = 1.0 to 1.6) was observed among French Canadians in a population-based Montreal case-control study, though the OR did not increase among thos e thought to have the most substantial exposure (Siemiatycki et al. 1991). A stronger association (OR = 2.0, 95% CI = 1.2 to 3.5) was noted in a second Cana dian case-control study (Risch et al. 1988), including a significant trend with duration of exposure, a nd this study was able to adjust for smoking,05/08/03 RoC Background Document for Lead and Lead Compounds

73 socieconomic status, and other personal risk factors. The lone exception to the pattern was provided by the lack of association of bladder cancer with peak blood lead measurements in a general cohort of Finnish workers (Anttila et al. 1995).

A positive association of lead exposure with bl adder cancer thus was very consistent in studies published to date. It persisted when smoking was controlled for, and limited direct evidence was found for an exposure-response rela tionship, as well as i ndirect evidence of consistently elevated risks among smelter work ers, with their potenti al for intense lead exposure. On the other hand, as suggested by Fu and Boffetta (1995), publication bias
cannot be eliminated as a contributor to the preponderance of positive results. Further limiting the conclusiveness of the evidence is th e limited size and low statistical power of
most studies.

3.3.5 Childhood cancers

Five studies have examined the relations hip of paternal lead exposure to childhood
cancer. Three case-control studies focused on Wi lms’ tumor. The earliest of these studies (Kantor et al. 1979) reported a markedly elevated OR among children with fathers in lead-related industries. Two subsequent stud ies failed to replicate this finding (Wilkins and Sinks 1984a, 1984b, Olshan et al. 1990). IARC (1990) questioned the criteria used by Kantor et al. (1979) to assign lead exposure status to the paternal occupation listed on
the childrens’ death certificates. Olshan et al. (1990) obtained detail ed job histories via questionnaire and assigned lead exposure st atus from a standard exposure matrix. Faulty exposure classification or a chance findi ng stemming from examination of multiple exposures in a small study may account for the discrepancy.

Buckley et al . (1989) linked fathers’ occupational lead exposure of long duration to childhood nonlymphoblastic leukemia in a st udy of 204 cases and matched population
controls. The association was striking, with 6 leukemia patients and no control subjects having exposed fathers. However, the statistical strength of these results is limited by the small number of paternal exposures.

A large cohort study of children of printers yielded an inconsistent association between estimated paternal lead exposure and devel opment of cancer (Krist ensen and Andersen 1992). The study was limited by the small number of casees, which made it necessary to combine all types of cancer, and by the absence of control for other potential risk factors.

Overall, the literature to date is characterized by a scarcity of studies and by small sample sizes, hampering the ability to draw firm conc lusions from the available data (see Table 3-6).

3.3.6 Other adult cancers

Other cancers with some evidence linking th em to lead exposure in the reviewed
literature include cancers of the brain a nd central nervous system, liver, colon, and

rectum.

Positive results were most common for brai n and central nervous system cancers, with eight studies reporting evidence of an associ ation with lead expos ure. Based on seven05/08/03 RoC Background Document for Lead and Lead Compounds

74 cohort studies of highly exposed workers, Steenland and Boffetta (2000) calculated a fixed-effects combined RR of 1.06 (95% CI = 0.81 to 1.40) for brain cancer (N = 69). A fixed-effects analysis was justified by the relative homogeneity of risk estimates across the seven studies (0.75, 0.75, 2.17, 1.10, 0.72, 1.14, 1.48, 1.23), taking into account their small sample sizes and wide confidence interv als. No additional relevant studies have become available since that meta-analysi s was conducted. The positive associations observed in most studies is suggestive, a lthough it is notable that a meta-analysis
restricted to the cohorts with the most de finitive lead exposure pr oduced a nonsignificant risk estimate barely above 1.0. The fundamental problem is that th e rarity of these cancers generally limits the st atistical power of studies.

3.3.7 General population exposures and cancer

The population-based cohor t studies of Jemal et al . (2002) and Lustberg et al . (2002) are a unique resource. The first study’s findings are provocative in that they connect increased blood lead levels in the general U.S. population with mild el evations in risk of the same types of cancer, lung and stomach, mo st consistently associated with leadexposed occupations. As discussed in Sec tion 3.3.1, Steenland and Simonsen concluded that no relevant occupational studies of lead and lung cancer had been published since the Steenland and Boffetta (2000) meta-analy sis. The only subse quent study involving populations with clearly estab lished lead exposure was Jemal et al. (2002). With that study added to the meta-analysis, the data no longer exhibited sufficient heterogeneity to preclude a fixed-effects anal ysis even with Lundström et al. (1997) included. The expanded meta-analysis yielded a fixed- effects RR for lung cancer of 1.32 (95% CI = 1.16 to 1.50) over the nine cohorts, very similar to the random-effects RR obtained
without Jemal et al . (2002). Inclusion of Jemal et al. (2002) must be accompanied by the caveat that the magnitude of lead expos ure in the population- based cohort (whose exposure was defined as blood lead levels above the medi an observed in the general population) was not truly comparable to that expected in workers w ith substantial lead exposure. This cohort was not added to th e revised meta-analysis for kidney cancer described in Section 3.3.3 because of inadequa te numbers (only 5 cases in males) and the low exposure cutoff. Interpretation of the results of Jemal et al. (2002) is limited primarily by low statistical power, particular ly for sites other than the lung, lack of adjustment for other risk factors (such as sm oking) in the site-specific analyses, and the absence of data on exposure to other occupational carcinogens.

Lustberg et al. (2002) analyzed predominantly the same data as Jemal et al . (2002), using different techniques and analytical assump tions, yet reaching conclusions also linking cancer to lead exposure. Further, unlike Jemal et al. , Lustberg et al. limited the cohort to persons with blood lead levels below the OS HA standard for lead exposure. However, exclusion of persons with blood lead levels in the range typical of workers considered to be lead-exposed precluded in clusion of this study in the revised meta-analysis by
Steenland and Simonsen. In consideri ng the evidence provided by Lustberg et al. that
lead could exert effects even at levels co mmonly found in the general population, it must be kept in mind that this study shares the limitations cited above for Jemal et al. (2002).

The case-control studies of Kandiloris et al . (1997) and Shukla et al . (1998) reported evidence mildly linking lead exposure with can cers of the larynx a nd gall bladder. These05/08/03 RoC Background Document for Lead and Lead Compounds

75 studies’ small sample sizes and lack of control for other potential risk factors limit the
conclusions that can be drawn from them.

3.4 Conclusion
Many epidemiologic studies on the potential role of lead exposure in cancer have been published since the IARC (1987) update. The ev idence is consistent with the hypothesis that lead is modestly carci nogenic to humans. This evidence is strongest for lung cancer, for which a largely consistent association has been demons trated with occupations and industries entailing lead exposur e, as well as with indices of individual lead exposure, including job history and bi ological monitoring. Evidence al so suggests an association between lead and stomach cancer. However, the observed associations generally are sufficiently weak that they could be due at least partially to confounding by nonoccupational risk factors, such as smoking in the case of lung cancer, or to effects of other occupational exposures that accompa ny lead exposure, particularly arsenic exposure. Such exposures are ubiquitous in smelting operations, batt ery manufacture, and
other intense sources of lead e xposure. Most studies to date ha ve done little to control for non-occupational risk factors and occupatio nal co-exposures, but more studies are beginning to do so, in most cases without weakening the observed association between lead exposure and cancer. Further, the crude exposure measures used by most studies, such as considering whole plants or occ upations to be uniformly exposed, may have resulted in underestimation of risk, because individuals who truly had high lead exposure may have been combined with those who did not. Evidence from studies of human populations thus are compatible with mild increases in risk for lung cancer and, to a lesser degree, stomach cancer, although this evidence must be weighed against the potential for confounding by co-exposures.05/08/03 RoC Background Document for Lead and Lead Compounds76Table 3-4. Studies of lead exposure and cancer: cohortReferenceStudy populationExposureEffectsCommentsDingwall-Fordyceand Lane 1963425 male employees drawingpensions from U.K. battery plantsEmployees werecompared with nationalpopulation counterparts.Urinary lead excretionwas also used tocategorize workers byestimated exposure(none, light, or heavy):80 lightly and 187heavily (at least 100μg/L) exposed.SMR (95% CI); no. observed deathsAll cancer:1.2 (0.8–1.7); 267no consistent increase in SMRs acrosscategories of increasing lead exposurePotentialconfounders:smoking, exposure toarsenic, other metalsOther limitations:not cancer sitespecificCooper and Gaffey1975: see Cooperetal. 198505/08/03 RoC Background Document for Lead and Lead Compounds77ReferenceStudy populationExposureEffectsCommentsRencheret al.1977Utah copper workers (numbers notreported) employed in smelting,mining, or concentrator operations,followed from 1959–1969Mortality was compared with the statepopulation and with workers in otheroperations.Cause of death was identified fromdeath certificate.Exposure to lead, arsenic,amd other substances wasestimated by operationtype.Within smelter workers,cumulative exposure tolead (units not specified)was calculated fordeceased workers.Age-adjusted respiratory cancer rates(per 10,000):smelter workers 10.1mine workers 2.1state population 3.3Age-adjusted non-respiratory cancer rates(per 10,000):smelter workers 16.6mine workers 10.0Percentage of deaths from lung cancer:smelter workers 7mine workers 2.2Cumulative lead and arsenic exposure:17 smelter workers dying of respiratorycancer 154.5 (Pb) 110 (As)smelter workers dying of other respiratorycauses 78.6 (Pb) 38.5 (As)smelter workers dying of non-respiratorycauses 93.4 (Pb) 47.0 (As)Potentialconfounders:arsenic, sulfur dioxide,sulfuric acid, otherexposures, smoking05/08/03 RoC Background Document for Lead and Lead Compounds78ReferenceStudy populationExposureEffectsCommentsBertazzi andZocchetti 1980700 Italian newspaper plant workersemployed for at least 5 years between1940 and 1955Mortality was compared with nationalrates.Compositors andstereotypers wereconsidered to be exposedto lead.SMR (no. of deaths)Lead-exposed workers:all cancers 0.44 (4)digestive 0.59 (2)respiratory 0.42 (1)lymphatic 2.00 (1)noP-values < 0.05All newspaper workers:all cancers 1.23 (51)digestive 1.20 (19)respiratory 1.56 (17)lymphatic 1.17 (3)noP-values < 0.05Potentialconfounders:smoking, otheroccupationalexposuresOther limitations:scarcity of truly leadexposed workers,small number ofdeathsSheffetet al.19821,946 U.S. lead and zinc chromatepigment plant workers employed atany time from 1940–1969Mortality was compared with age andcalendar-year-specific national rates.All workers wereconsidered to be exposedto lead.Lung, stomach, and pancreatic cancer riskssignificantly elevated(persons of unknownvital status assumed to be alive at end offollow-up)Lung cancer SMR:1.6 (whites, blacks;P< 0.05 in whites only)Whites:nonsignificantly elevated risks for stomach,rectal, pancreatic, and prostate cancer,Hodgkin’s disease; decreased risks ofintestinal and laryngeal cancerNonwhites:mildly elevated risks of stomach andpancreatic cancer; decreased risk of laryngealcancerPotentialconfounders:smoking, zinc, nickel,other occupationalexposures05/08/03 RoC Background Document for Lead and Lead Compounds79ReferenceStudy populationExposureEffectsCommentsMalcolm and Barnett1982(follow-up ofDingwall-Fordyceand Lane 1963)1,898 U.K. lead-acid battery workersHigh, medium, and nolead exposure were basedon job history.Proportionate mortality ratio (PMR)All cancers:1.15 (136 deaths),P> 0.05By exposure:no 1.02medium 1.06high 1.30no significant excessesfor individual cancersites except for digestive cancer PMR of 1.67,P< 0.01, among non-exposed workersPotentialconfounders:smoking, otheroccupationalexposuresOther limitations:difference in exposurefor high vs. mediumnegligible by end offollow-upDavies 1984a1,152 U.K. chromate pigment factoryworkers employed for at least oneyear by 1975Three factories: one lead chromateonly, two lead and zinc chromateMortality was compared with nationalrates.High to moderateexposure to chromatedust was based on jobhistory.RR (no. of deaths)significant excess of lung cancer deaths amongchromate-exposed workers with mixed zincand lead chromate exposure:Factory A:entrants from 1932–1954 2.2 (21)no excess for entrants after 1955Factory B:entrants from 1948–1960 4.4 (11 )no excess among workers exposed only to leadchromate; no consistent increase with durationof servicePotentialconfounders:smoking, coexposures (solvents,etc.)Other limitations:small numbers05/08/03 RoC Background Document for Lead and Lead Compounds80ReferenceStudy populationExposureEffectsCommentsDavies 1984b(follow-up of Davies1984a)57 U.K. chromate pigment factoryworkers who had been diagnosed withlead poisoning between 1930 and1945Mortality was compared with nationalrates.Workers ever clinicallydiagnosed with leadpoisoning wereconsidered to be exposedto lead.RR (95% CI); no. of deathsLung cancer:1.45 (0.39–2.71) (4)All other cancers combined:0.8 (3)Potentialconfounders:zinc, chromate, otheroccupationalcoexposures, smokingOther limitations:inadequate numbersCooperet al.1985(follow-up of Cooperand Gaffey 1975)(followed up byWong and Harris2000)(see also nested casecontrols by Cooperetal.1989 and Wongand Harris 2000)U.S. battery (4,519) and leadproduction (2,300) workers employedfor at least one year between 1946 and1970Mortality was compared with nationalage- and gender-specific rates (SMR)and age-, gender-, and race-specificrates (PMR)Cause of death was identified fromdeath certificate.(1) battery plant workers(2) lead productionworkersWorkers also werestratified by cumulativeyears of employment (1–9, 10–19, 20+)SMR (95% CI)Battery plant workers:all cancer 1.13 (1.02–1.26)all respiratory 1.24 (1.03–1.49)stomach 1.68 (1.16–2.35)lung, trachea, bronchus1.24 (1.02–1.50)liver and laryngeal: nonsignificant excesskidney: nonsignificant deficitProduction workers:digestive and respiratory: nonsignificantincreasekidney, brain, or lymphopoietic system: noexcessPMR analyses controlled for race yieldedsimilar results.Potentialconfounders:smoking, diet,coexposuresSelevanet al.1985:see Steenlandet al.199205/08/03 RoC Background Document for Lead and Lead Compounds81ReferenceStudy populationExposureEffectsCommentsGerhardssonet al.1986: seeGerhardssonet al.1995Sweeneyet al.19862,510 male east Texas chemical plantworkers employed 1952–1959Mortality compared with nationalrates.TEL was the majorproduct from 1952–1959;thereafter, ethylenedibromide, inorganiclead, and vinyl chloridealso were major products.RR (observed vs. expected)Respiratory:1.4 (15 vs. 11)Brain:1.8 (3 vs. 1.6)Mortality from all causes:0.8no excesses for other cancersPotentialconfounders:other occupationalexposuresOther limitations:small numbers, nodetailed exposuredata, healthy-workereffectCordioliet al.1987468 Italian glass workers employedfor at least one year between 1953 and1967Workers producing lowquality glass containerswere classified as leadexposed.SMR (95% CI); no. of deathsAll cancer 1.3 (0.8–1.8); 28Lung 2.1 (1.1–3.6); 13Laryngeal 4.5 (1.2–11.4); 4Potentialconfounders:smoking, exposure toarsenic and othermetals, heat, andfumes05/08/03 RoC Background Document for Lead and Lead Compounds82ReferenceStudy populationExposureEffectsCommentsAdes and Kazantzis19884,393 male U.K. zinc, lead, andcadmium smelter workers followed upfor lung cancer mortalityMortality was compared with nationalrates.Nested case-control analysis also wasconducted that quantitatively assessedcadmium and, secondarily, arsenic,lead, and other metal exposuresamong 174 cases.Job histories were used toquantify cadmiumexposure and assignordinal ranks forexposure to lead andother metals.SMR (95% CI); no. of deathsCohort:Lung 1.25 (1.07–1.44) (174)increased significantly with duration ofemploymentnested case-control analyses did not implicateany department or process, nor did cadmium,zinc, sulfur dioxide, or dust exposure accountfor the observed increasecumulative exposure to lead and to arsenicboth showed positive associations with lungcancer, but the relative importance of thesetwo exposures could not be determinedPotentialconfounders:smoking, arsenic,other unquantifiedcontaminantsSankilaet al. 19901,803 male and 1,946 female glassworkers employed for at least 3months at one of 2 Finnish glassfactories in 1953–1971 or 1941–1977Cancer incidence was compared withage-, gender-, and calendar-yearspecific national rates.Stomach, lung, and skincancer rates also werecompared separately for201 male and 34 femaleglassblowers and nonglassblowers.SIR (95% CI); no. of casesLung cancer, all glass workers:male 1.3 (1.0–1.7); 62female 1.1 (0.5–2.3); 7lung cancer risk showed no specificity forglassblowersSkin cancer, M & F combined:all workers 1.5 (0.8–2.7); 11little difference between gendersglassblowers 6.2 (1.3–18.3); 3Stomach cancer, M & F combined:glassblowers 2.3 (0.9–5.0); 6no increase in other glass workersno increase in cancers of other sitesPotentialconfounders:smoking, arsenic,cadmium, chromium,copper, nickel, zinc,silica, asbestos05/08/03 RoC Background Document for Lead and Lead Compounds83ReferenceStudy populationExposureEffectsCommentsWingren andEnglander 1990(same population asin case-controlanalyses of Wingrenand Axelson 1985,1987, 1993)625 Swedish glass workers employedfor at least 1 month between 1964 and1985Mortality was compared with nationalrates.Workers from areas withairborne lead levels up to0.110 mg Pb/m3wereclassified as exposed.SMR (95% CI)Pharyngeal:9.9 (1.2–36.1)Lung:1.4 (0.5–3.1)Colon: nonsignificantPotentialconfounders:coexposures, smoking,dietOther limitations:small numbersSteenlandet al. 1992(follow-up of Selevanet al. 1985)1,990 male workers employed for atleast 1 year in a lead-exposeddepartment at a U.S. lead smelter inIdaho during 1940–1965High-lead-exposuresubgroup consisted of1,436 workers fromdepartments with anaverage of least 0.2mg/m3airborne lead or≥50% of jobs showing0.40 mg/m3or greater ina 1975 survey.SMR (95% CI); no. of deathsTotal cohort:nonsignificantly elevated RRs: kidney,bladder, stomach, and lung cancerHigh-lead-exposure subgroup:kidney 2.39 (1.03–4.71); 8bladder 1.33 (0.48–2.90); 6stomach 1.28 (0.61–2.34); 10lung 1.11 (0.82–1.47); 49Potentialconfounders:smoking, coexposures, dietCoccoet al. 1994a(expansion of Cartaetal.1994)1,741 male Sardinian lead and zincminers from two mines employed atleast one year between 1931 and 1971Mortality was compared with age- andcalendar-year-specific regional ratesAll miners wereconsidered to be exposedto lead.SMR (95% CI); no. of deathsall cancer 0.94 (0.83–1.05); 293prostate 1.21; 16bladder 1.15; 17kidney 1.28; 7nervous system 1.17; 8oral 0.61; 8lymphohemopoietic 0.91; 21digestive 0.83; 86peritoneum 3.67 (1.35–7.98); 6no otherP-values < 0.05Potentialconfounders:silica, radon, other coexposures, smoking,diet05/08/03 RoC Background Document for Lead and Lead Compounds84ReferenceStudy populationExposureEffectsCommentsCoccoet al. 1994b526 female Sardinian lead and zincminers from the same mines as inCoccoet al.1994aMortality was compared with age- andcalendar-year-specific regional ratesAll miners wereconsidered to be exposedto lead.SMR (95% CI)liver 5.02 (1.62–11.70)lung 2.32 (0.85–5.05)other cancers showed nonsignificantly reducedratesPotentialconfounders:coexposuresOther limitations:small numbersGerhardssonet al.1995a(follow-up ofGerhardssonet al.1986)684 male Swedish lead smelterworkers with lead exposure, followedfrom 1969–1989Incidence was compared with countyrates.Lead exposure wasdefined as a detectableblood lead level.SIR (95% CI); no. of casesAll malignancies:1.27 (0.91–1.74); 40Respiratory:1.32 (0.49–2.88); 6All gastrointestinal:cohort 1.84 (0.92–3.29; 11highest quartile 2.34 (1.07–4.45); 9Stomach:1.88 (0.39–5.50); 3Colon:1.46 (0.30–4.28); 3SIRs for all other sites except brain werenonsignificantly elevated; too few casesPotentialconfounders:smoking, dietOther limitations:small numbers,meaningful doseresponse analyses notpossible because ofinadequate numbersfor most cancer sites05/08/03 RoC Background Document for Lead and Lead Compounds85ReferenceStudy populationExposureEffectsCommentsAnttilaet al.199520,700 Finnish workers with at leastone blood lead measurement between1973 and 1983 by the Finnish Instituteof Occupational Health, linked to theFinnish Cancer Registry through1988. No loss to follow-up.Cause of death was identified fromdeath certificate.Mortality and incidence comparedwith gender-, 5-year age, and 4-yearcalendar-year matched national rates.Exposure was categorizedaccording to the highestpeak blood levelmeasured:low: 0–0.9μmol/L[0 to 18.6μg/dL]moderate: 1–1.9μmol/L[20.7 to 39.4μg/dL]high: 2–7.8μmol/L[41.4 to 161.6μg/dL]Total cohort:no elevation in total or site-specific cancermortalityModerately exposed:total respiratory and lung cancer:SIR = 1.4 (95% CI = 1.0–1.9) for bothtotal digestive, stomach, bladder, andnervous system: nonsignificant elevationsHighly exposed:no increase in risksAll cancer:RR = 1.4 (95% CI = 1.1–1.8)Lung or tracheal:RR = 2.0 (95% CI = 1.2–3.2)no increase in high-exposure groupno RRs reported for other cancersCase-referent substudies:lung cancer ORs increased with increasingcumulative exposure to leadhighly exposed: squamous-cell lung cancerOR = 4.1 (95% CI = 1.1–15) afteradjustment for smokingPotentialconfounders:coexposuresOther limitations:short follow-up05/08/03 RoC Background Document for Lead and Lead Compounds86ReferenceStudy populationExposureEffectsCommentsCoccoet al.19961,222 male Sardinian lead and zincsmelter workers whose G6PDphenotypes had been determined,employed any time from 1973–1990Mortality was compared with regionalrates.Workers were subdividedinto G6PD-normal and-deficient groups.SMR (no. of deaths)all cancer and lung cancer: lower thanexpectedstomach cancer: higher (2 observed vs. 0.6expected)G6PD-normal 0.26 (10)G6PD-deficient 0.18 (2)G6PD deficiency had little apparent effect onmortality: cancer and all-cause mortality wasslightly lower among G6PD-deficient workersthan among G6PD-normal workersPotentialconfounders:co-exposures,smokingOther limitations:healthy worker bias(all-cause mortality 31observed vs. 44expected), brieffollow-up, lowproportion of olderages (mean age atentry 30, averagefollow-up less than 11years), no cumulativeexposure dataCoccoet al.19971,388 male production andmaintainance workers employed for atleast 1 year at a Sardinian lead andzinc smelter between June of 1932and July of 1971.Mortality was compared with age- andcalendar-year-specific regional rates.National rates could not be used forcomparison, because the regionalpopulation showed large departuresfrom them, limiting the analysis to theperiod from 1965–1992 for whichregional rates were available, insteadof the entire 1950–1992 follow-upperiod.All workers wereconsidered to be exposedto lead.SMRs vs. regional rates (95% CI); no. ofdeathslung 0.82 (95% CI 0.56–1.16); 31stomach 0.97 (0.53–1.62); 14all cancers 0.93 (0.78–1.10); 132kidney 1.75 (0.48–4.49); 4bladder 1.45 (0.75–2.53); 12brain 2.17 (0.57–5.57); 4kidney cancer showeda significant trendtoward increasing risk with increasing durationof exposureno significant trends were noted for lung orother cancersbrain cancer excess was limited to workersemployed for 10 years or lessPotentialconfounders:exposure in other jobs(e.g., silica fromneighboring lead andzinc mine), smoking,co-exposure to zinc,arsenic, copper, othermetals, silicaOther limitations:no intensity ofexposure, possiblemisclassification ofcause on deathcertificates05/08/03 RoC Background Document for Lead and Lead Compounds87ReferenceStudy populationExposureEffectsCommentsLundströmet al.1997(follow-up ofGerhardssonet al.1986)(see also subcohortanalyses of Englystetal.2001)3,979 Swedish copper and leadsmelter workers, subdivided into1,992 belonging to departmentsexposed to lead only and 1,026 withhigh cumulative exposureMortality and incidence comparedwith age-, year-, gender-, and countyspecific ratesThe lead-only groupconsisted of workers inlead-only departments;the high cumulativeexposure group consistedof workers with bloodlead levels≥10μmol/L[≥207μg/dL], based onsumming mean bloodlead monitoring resultsfor each year exposed.SMR (95% CI); no. of deathsLung:total cohort 2.8 (2.0–3.8); 39highly exposed 2.8 (1.8–4.5); 19SIR (95% CI); no. of casesLung with 15-year lag:total cohort 2.9 (2.1–4.0); 42highly exposed 3.4 (2.2.–5.2); 23lead-only 3.1 (1.7–5.2); 14lead-only highly exposed 5.1 (2.0–10.5); 7Other highly exposed (total cohort),with 15-year lag:brain 1.6 (0.4–4.2); 4renal pelvis, ureter, bladder 1.8 (0.8–3.4); 9kidney 0.9 (0.2–2.5); 3all cancer 1.1 (0.9–1.4); 83Potentialconfounders:smoking, diet05/08/03 RoC Background Document for Lead and Lead Compounds88ReferenceStudy populationExposureEffectsCommentsWong and Harris2000(follow-up of Cooperet al. 1985)U.S. lead battery plant (4,518) andsmelter (2,300) workers followedfrom 1947 through 1995follow-up of Cooperet al. 1985 withmore detailed exposure data andnested case-control component forstomach cancerMortality was compared with U.S.national age-, calendar-year-, andgender-specific rates.Cause of death was identified fromdeath certificates(See entry under case-control studiesfor nested study of stomach cancer.)(1) battery plant workers(2) lead smelter workersWorkers also werestratified by cumulativeyears of employment (1–9, 10–19, 20+), date ofhire (pre-1946 vs. 1946on), and lag betweenexposure and cancer (<20, 20–34, > 34 years).SMR (95% CI)Battery plant workers:all cancer 1.05 (0.97–1.13)all respiratory 1.13 (0.98–1.29)stomach 1.53 (1.12–2.05), significantlung, trachea, bronchus1.14 ( 0.99–1.30)thyroid, Hodgkin’s: nonsignficantbladder 0.49 (0.23–0.90),significant depressionSmelter workers:digestive, respiratory, thyroid:nonsignificantlung 1.22 (1.00–1.47)Battery plant and smelter workers combined:all cancer 1.04 (0.97–1.11)all respiratory 1.15 (1.03–1.28)stomach 1.47 (1.13–1.90)lung, trachea, bronchus1.16 ( 1.04–1.30)thyroid/endocrine 3.08 (1.33–6.07),lung and stomach risks lower for pre-1946hires; higher for workers employed 10–19years than < 10, but lower for > 19 years;SMRs peaked with 20- to 34-year latency forlung, but < 20 years for stomachPotentialconfounders:smoking, diet,coexposuresOther limitations:no assessment ofemployment historyafter 198105/08/03 RoC Background Document for Lead and Lead Compounds89ReferenceStudy populationExposureEffectsCommentsEnglystet al.2001(follow-up and subanalysis of Lundströmet al. 1997)Limited to 1,093 workers in thesmelter’s lead department, followedthrough 1997Incidence was compared with countyrates; age-specific SIRs with 15-yearlag.Workers were dividedinto Subcohorts I and IIfor ever and neverworked in areas generallyassociated with exposureto arsenic or other knowncarcinogens (701 and 383workers, respectively).Detailed individualassessment of arsenicexposure was made forall lung-cancer cases.SIR (95% CI); no. of casesSubcohort I (co-exposed):lung 2.4 (1.2–4.5); 10Subcohort II (not co-exposed):lung 3.6 (1.2–8.3); 5subjects with lung cancer found to havehistory of “considerable” exposure to arsenic:9/10 among Subcohort I, 4/5 among SubcohortIIPotentialconfounders:smoking, dietJemalet al.2002(same cohort as inLustberg andSilbergeld 2002except for inclusioncriteria)3,592 U.S. white participants from the1976–1980 NHANES II health andnutrition survey who had blood leadmeasured at entry, followed through1992 via NDI and SSADMFRRs were adjusted for age andsmoking.Blood lead (μg/dL) wasmeasured by atomicabsorption and used toclassify subjects intoexposure quartiles orgroups above vs. belowmedian exposure.RR (95% CI); no. of deathsLung (above vs. below median):Total cohort 1.5 (0.7–2.9); 71M 1.2 (0.6–2.5); 52F 2.5 (0.7–8.4); 19Stomach (above vs. below median):Total cohort 2.4 (0.3–19.1); 5M 3.1 (0.3–37.4); 4F no deaths in referent groupAll cancer:total cohort by quartile (ageadjusted) 1.0, 1.2, 1.3, 1.5 (Pfor trend 0.16)Potentialconfounders:occupationalexposure,socioeconomic status,potential residualconfounding bydegree and duration ofsmoking (onlycontrolled for never,former, current < 1,current 1+ pack/day)05/08/03 RoC Background Document for Lead and Lead Compounds90ReferenceStudy populationExposureEffectsCommentsLustberg andSilbergeld 2002(same cohort as Jemalet al. 2002 except forinclusion criteria)4,190 U.S. participants from the1976–1980 NHANES II health andnutrition survey who had blood leadmeasured at entry and whose levelsfell below 30μg/dL. Followed upthrough 1992 via NDI and SSADMF.Age- and multivariate-adjustedrelative risk.Blood lead (μg/dL)measured by atomicabsorption and used toclassify subjects intoexposure groups:low: < 10medium: 10-19high: 20–19RR (95% CI)All cancer, vs. low exposure:medium 1.5 (0.9–2.5)high 1.7 (1.0–2.8)Lung, vs. low exposure:medium 1.7 (0.6–4.8)high 2.2 (0.8–6.1)Non-lung, vs. low exposure:medium 1.5 (0.8–2.8)high 1.5 (0.8–2.8)Potentialconfounders:potential residualconfounding bydegree and duration ofsmoking (onlycontrolled for never,former, current < 1,current 1+ pack/day)Other limitations:small numbers fornon-lung cancers.05/08/03 RoC Background Document for Lead and Lead Compounds91Table 3-5. Studies of lead exposure and cancer: case-controlReferenceStudy populationExposureEffectsCommentsRobinson 1976Cases:139 U.S. TEL workers with 20or more years in exposed jobsControls:139 workers with no knownoccupational lead exposure, matchedby age, gender, race, and years ofemploymentWorkers were classifiedas TEL-exposed if theyworked in exposed jobsfor at least 20 years.Skin cancer:7 in lead-exposed, 4 in nonexposed groupno cancers of other sites in either groupLimitations:inadequate sizeFanning 1988(Cases overlap thoseoccurring in theDingwall-Fordyce1963 and Malcolm1982 cohorts)Cases:2,073 deceased malesidentified through pension records ofbattery and other factory workers inthe U.K.Controls:workers dying from aspecific cancer were compared with acontrol group consisting of workersdying from all other causesHigh or moderate leadexposure vs. little or noexposure was based onjob titles.OR (95% CI)76 lung cancer deaths 0.93 (0.8–1.1)31 stomach cancer deaths 1.34 (1.10–1.17)no associations for other cancer types;elevations in stomach and total digestivecancers limited to the period before 1966Potential confounders:metals and otheroccupational exposures,smokingOther limitations:potentially exposurerelated deaths amongcontrolsRischet al.1988Cases:826 Canadian men withhistologically confirmed bladdercancer during 1979–1982Controls:792 controls from Canadianpopulation, matched on age, gender,and areaSubjects wereinterviewed regardinglength of occupationalexposure to leadcompounds, as well as 17other substances.OR (95% CI)61 men ever exposed to lead (smokingadjusted):2.0 (1.2–3.5)Trend per 10 years’ duration of exposure:1.45 (1.09–2.02)no other substances showed significantassociations with bladder canceradjustment for marital status, socioeconomicstatus, education, ethnicity, urban vs. ruralorigin had no effect on resultsPotential confounders:other occupationalexposureOther limitations:low control interviewrate (53%), potentiallyinaccurate recall05/08/03 RoC Background Document for Lead and Lead Compounds92ReferenceStudy populationExposureEffectsCommentsCooperet al.1989(based on cohort inCooperet al.1985)(succeeded by Wongand Harris 2000)Cases:39 male gastric cancer deathsfrom a Scandanavian battery and leadproduction worker cohortControls:120 controls from the samecohortExposure was categorizedby duration ofemployment, in quartiles.ORSecond quartile vs. first: 0.3Third quartile vs. first: 1.7Fourth quartile vs. first: 0.4increasing lead exposure showed noassociation with gastric cancerPotential confounders:co-exposures, diet,socioeconomic statusOther limitations:inadequate sizeMallinet al.1989Cases:random sample of 10,013deaths from 7 specific cancers,identified from death certificates forIllinois males between 1979 and 1984Controls:3,198 randomly selecteddeaths from other causesExposure was based onccupations abstractedfrom death certificates.Brain cancer, white male glass workers:OR = 3.0,P< 0.05no significant associations for other cancersitesPotential confounders:no control for otherfactorsOther limitations:poor specificity for leadexposureSiemiatyckiet al.1991Cases:3,730 various histologicallyconfirmed cancersControls:specific cancer types werecompared with other cancers as acontrol group, excluding lung cancerSeparate subgroup analysis wasrestricted to French CanadiansOccupational exposure to293 substances, includinglead, was estimated frominterviews.Exposure was classifiedas “any”; a subgroup with“substantial” exposurealso was identified.OR (90% CI); no. of casesAny exposure to lead:lung 1.1 (0.9–1.4); 326(French Canadians only)stomach 1.2 (1.0–1.6); 126bladder 1.3 (1.0–1.6); 155(French Canadians only)kidney 1.2 (1.0–1.6); 88ORs rose in the “substantial” exposuresubgroup for stomach and lung, but not forbladder or kidney cancerPotential confounders:co-exposuresStrengths:control for smokingmultiple testing fordifferent risk factorsKauppinenet al.1992Cases:344 primary liver cancerdeaths reported to the Finnish CancerRegistry in 1976–1978 or 1981Controls:registry-reported stomachcancer (476) or myocardial infarctionQuestionnaires regardingjob history and personalhabits were sent to theclosest available relative.U.K. based job-exposureOR (95% CI)52 workers with potential lead exposure:0.91 (0.65–1.29)11 womenwith potential lead exposure:Limitations:most controls hadstomach cancer, smallnumbers of subjectsrated probably exposed05/08/03 RoC Background Document for Lead and Lead Compounds93ReferenceStudy populationExposureEffectsComments(385) deaths in the same hospitals,frequency matched by age and gendermatrix was used to ratepotential exposure to 50substances, includinglead compoundsIndustrial hygienists alsoinspected histories toidentify those with highlyprobable exposure andrate it as high, low, ormoderate (< 10 yearshigh or 10+ years lowexposure)1.84 (0.83–4.06)5 men with probable moderate exposure:2.28 (0.68–7.67)none had high exposure and only 1 had lowexposure, whereas 4 controls had highexposurefemale controls appeared to underreport theirjob historyWingren and Axelson1987, 1993(update of Wingrenand Axelson 1985,same basic cohort asin Wingren andEnglander 1990)Source population:5,498 men aged45 or older in 11 Swedish parishes,including 887 glass workersCancer-specific nested case-controlanalysis:Cases:deaths due to stomach, colon,and lung cancer from 1950–1982Controls:deaths due to causes otherthan cancer or cardiovascular diseaseGlass workers wereconsidered exposed.Occupations also werecategorized as low,moderate, or high leadexposure based on jobmatrix.OR (90% CI); no. of deathsAll glass workers:lung 1.7 (1.1–2.5); 86stomach 1.5 (1.1–2.0); 206colon 1.6 (1.0–2.5); 79Glassblowers:lung 2.3stomach 2.6colon 3.1ORs for high or moderate vs. low exposureshowed no consistent increase for lung orstomach cancer, mild upward trend for coloncancerPotential confounders:smoking, co-exposures,diet05/08/03 RoC Background Document for Lead and Lead Compounds94ReferenceStudy populationExposureEffectsCommentsAnttilaet al.1996(See Anttilaet al. 1995 for basicinformation on the source population.)Nested case-control analysis:Cases:26 Finnish men with CNScancerControls:200 Finnish men withoutCNS cancerOccupational history andother risk-factor datawere obtained frompatients or next of kin.Exposure based on peakblood lead levels wascategorized as 0.1–0.7,0.8–1.3, and 1.4–4.3μg/L.Cumulative leadexposure as the sum ofmean annual blood leadlevel was categorized as0, 1–6, 7–14, or 15–49μg/L.OR (no. of cases or deaths)CNS cancer incidence (26 cases):rose with increasing peak lifetime bloodlead measurements; not significantGlioma mortality (16 deaths):rose consistently and significantly with peakand mean blood lead level, duration ofexposure, and cumulative exposureMortality by cumulative exposure, controlledfor cadmium, gasoline, and year monitoringbegan:low (13 subjects) 2.0 (2)medium (14 subjects) 6.2 (2)high (16 subjects) 12.0 (5)1 death among 26 subjects with no exposure:test for trend significant atP= 0.02Strengths:complete follow-up andminimal diseasemisclassification,controlled for smokingand exposure togasoline and cadmiumKandiloriset al.1997Cases:26 patients with histologicallyconfirmed laryngealcarcinoma and nohistory of lead exposure or toxicityControls:53 patients with similardemographic profiles and no historyof cancer from the same hospitalBlood lead levels andALAD activity weremeasured.blood lead levels were similar, but ALADactivity was significantly lower in cases thancontrolsPotential confounders:other risk factors or thedisease process itself05/08/03 RoC Background Document for Lead and Lead Compounds95ReferenceStudy populationExposureEffectsCommentsFayerweatheret al.1997Cases:735 cancer deaths during1956–1987 among male workers at aU.S. TEL production plant, identifiedby the company’s cancer andmortality registries, excluding bladdercancers deemedlikely due tobenzidene or beta-napthalamineexposureControls:time-, age-, gender-, andpayscale-matched plant workersExposure to lead wasranked as none, low,medium, high, and veryhigh, with cumulativeexposure derived bysumming yearly exposureover time.OR (95% CI)Digestive in workers ever TEL-exposedvery high 2.2 (1.2–4.0)high 1.3 (0.7–2.7)no association for lower exposuresRectal:ever 3.7 (1.3–10.2)low or medium 1.7 (0.4–8.3)high or very high 5.1 (1.6–16.5)Colon:ever 1.3 (0.7–2.5)high or very high 1.7 (0.8–4.0)low or medium 0.8 (0.4–1.8)Hodgkin’s disease:ever 2.7 (0.6–12.0)other cancers showed no association withexposureLimitations:loss of cancer deathsamong pensioners andthose leaving work dueto illnessCoccoet al.1998aCases:all 27,060 brain cancer deathsoccurring among persons aged 35 orolder during 1984–1992, from U.S.24-state death certificate registryControls:4 gender-, race-, age-, andregion-matched controls per caseselected from deaths due to nonmalignant causesSubjects were subdivided into 4groups by genderand race (white orAfrican-American) for all analyses.A job-exposure matrixwas applied to deathcertificate-listedoccupations to categorizepersons as having low,medium, or highprobability and intensityof exposure.risk of brain cancer mortality increasedconsistently with intensity of exposureamong African-American males, but notother race-gender groupsprobability of exposure alone was notconsistently associated with riskin the high-probability group, risk increasedwith exposure intensity for all groups exceptAfrican-American women (only 1 death inthe high-probability group)Limitations:death-certificateoccupation only,incomplete job history,potentialmisclassification ofcause of death05/08/03 RoC Background Document for Lead and Lead Compounds96ReferenceStudy populationExposureEffectsCommentsCoccoet al.1998bCases:all 28,416 CNS cancer deathsoccurring among persons aged 35 orolder during 1984–1992, from U.S.24-state death certificate registryControls:4 gender-, race-, age-, andregion-matched controls per caseselected from deaths due to nonmalignant causesSubjects were subdivided into 4groups by genderand race (white orAfrican-American) for all analyses.Industry and occupationwere identified fromdeath certificates.OR (95% CI)all occupations or industries with ORs above1.0 andP-value < 0.05 in at least one racegender group were reportedNewspaper printing and publishing industry:white M 1.4 (1.1–1.8)black M 3.1 (0.9–10.9)Typesetting and compositing:white M 2.0 (1.1–3.8)white F 1.3 (0.4–3.8)black F 4.2 (0.6–30.7)no deaths among black malesLimitations:death-certificateoccupation only, nodirect measure of leadexposure, potentialmisclassification ofcause of death05/08/03 RoC Background Document for Lead and Lead Compounds97ReferenceStudy populationExposureEffectsCommentsCoccoet al.1999Cases:all 41,957 stomach cancerdeaths occurring among persons aged35 or older during 1984–1996, fromU.S. 24-state death certificate registryControls:2 gender-, race-, age-, andregion-matched controls per caseselected from deaths due to nonmalignant causesSubjects were subdivided into 4groups by genderand race (white orAfrican-American) for all analyses.A job-exposure matrixwas applied to deathcertificate-listedoccupations to categorizepersons as having low,medium, or highprobability and intensityof exposure.OR (95% CI)adjusted for age, ethnicity, marital status,urban residence, and socioeconomic statusElevated ORs:white F, high prob. 1.53 (1.10–2.12)black M, high prob. 1.15 (1.01–1.32)black F, high prob. 1.76 (0.74–4.16)highly exposed group included 1,503 whiteand 453 black men and 65 white and 10 blackwomen; no pattern of increase acrossexposure levelsintensity of exposure showed no associationwith stomach cancer except for blackwomen:low 1.82 (1.04–3.18)moderate 1.39high 1.25Potential confounders:carcinogencoexposure(s)Other limitations:death-certificateoccupation only,incomplete job history,potentialmisclassification ofcause of deathShuklaet al.1998Cases:38 patients with newlydiagnosed, histologically confirmedgall bladder cancer cases assembledfrom an Indian surgical unitControls:58 patients with gall stonesdiagnosed at the same surgical unit,matched on by geographic area,served as controlsHeavy metal content wasmeasured in bile drawnfrom the gall bladder attime of surgery.Bile lead content: mean (SE) (mg/L):gall bladder cancer: 58.38 (1.76)gallstones: 3.99 (0.43)cadmium and chromium levels also wereelevated in cancer patients, but less than leadPotential confounders:coexposures to othermetals and potentialcarcinogens, smoking05/08/03 RoC Background Document for Lead and Lead Compounds98ReferenceStudy populationExposureEffectsCommentsHuet al.1998Cases:218 patients withhistologically-confirmed primarygliomas occurring during 1989–1996at 6 Chinese hospitalsControls:436 patients with nonneurological, nonmalignant disease.,matched by age, gender, and residencefrom the same hospitals except acancer-only centerPatients wereinterviewed, and thosewith factory or farmoccupations were furtherinterviewed to identifyexposure to lead (or otherpotentially toxicsubstances).no occupational exposure to lead wasreported for any glioma patients, but wasreported for 4 controlsPotential confounders:coexposures to otherpotential toxic agentsOther limitations:inaccurate recallHuet al.1999Cases:all 383 patients withhistologically confirmed primarymeningiomas occurring during 1989–1996 at 6 Chinese hospitalsControls:366 patients with nonneurological, nonmalignant diseasematched bu age, gender, and residencefrom the same hospitals except acancer-only centerPatients wereinterviewed, and thosewith factory or farmoccupations were furtherinterviewed to identifyexposure to lead (or otherpotentially toxicsubstances).OR (95% CI); no. of casesOccupational exposure to lead:M 7.20 (1.00–51.72); 6F 5.69 (1.39–23.39); 10ORs adjusted for income, education, and fruitand vegetable intake, plus cigarette packyears for the womenPotential confounders:coexposures to othermetalsOther limitations:recall biasWong and Harris2000Case-control study nested in Wongand Harris 2000 cohortCases:the 30 stomach cancer casesoccurring in a Philadelphia leadbattery plantControls:120 age-matched cohortmembersJob titles were used toclassify lead exposure aslow, intermediate, orhigh; total months of anyexposure, of intermediateor high exposure only,and of cumulativeexposure, with monthsweighted by 1, 2, or 3 ifspent in low-,intermediate-, or highexposure job.mean months of employment, of intermediateor high exposure, or of weighted exposure tolead were all nonsignificantly lower amongcasesOR for cumulative weighted exposure in the10 years prior to death:First quartile 1.00Second quartile 0.62Third quartile 0.82Fourth quartile 0.61Pfor trend = 0.47; ORs showed no positiveassociation with any index of exposurePotential confounders:unclear whetheranalyses werecontrolled for anypotential confounders;diet, co-exposures05/08/03 RoC Background Document for Lead and Lead Compounds99ReferenceStudy populationExposureEffectsCommentsPeschet al.2000Cases:935 renal-cell cancer patientsin five German areasControls:4,298 region, age, andgender-matched controls from thesurrounding populationORs were adjusted for age, center,and smoking,Exposure to cadmium,lead, and other potentialcarcinogens wasestimated from detailedjob histories and rated aslow vs. medium, high, orsubstantial. British andGerman job-exposurematrices were used.OR (95% CI); no. of casesSubstantial lead exposure based on Britishmatrix:M 1.5 (1.0–2.3); 29F 2.6 (1.2–5.5; 11Substantial lead exposure based on Britishmatrix:M 1.3 (0.9–2.0); 30F not reportedPotential confounders:coexposures toadditional metals orother carcinogens05/08/03 RoC Background Document for Lead and Lead Compounds100Table 3-6. Lead exposure and childhood cancerReferenceDesignStudy populationExposureEffectsCommentsKantoret al.1979casecontrolCases:149 Connecticutchildhood Wilms’ tumor casesfrom 1935–1973Controls:149 age-, gender-,and race-matched controlsPaternal occupation wasidentified from birthcertificate as lead-relatedor, lead/hydrocarbonrelated.Lead-related industry:OR = 5.0Hydrocarbon- or lead-relatedindustry:OR = 3.4Potential confounders:coexposuresOther limitations:small numbers, noquantitative exposureWilkins andSinks 1984a,1984bcasecontrolCases:62 Ohio childhoodWilms’ tumor cases from1950–1981Controls:62 matched controlsPaternal occupation wasidentified from birthcertificate as lead-relatedor hydrocarbon-related.OR “not significant for lead or forhydrocarbon-related occupations”Potential confounders:coexposuresOther limitations:very small numbers, noquantitative exposureBuckleyet al.1989casecontrolCases:204 childhood ANLLcases from 1980–1984Controls:204 age-, gender-,area-matched controlsidentified by random-digitdialingCumulative paternaloccupational exposure tolead was determined intelephone interviews withfathers and categorized as0, 1–1,000, > 1,000 days.178 case-control pairs withoccupational exposure data:1–1,000 days: OR = 1.0 (5 cases)> 1,000 days: not calculable;6 cases, 0 controls exposedPfor trend = 0.03Limitations:Pfor trend was only 0.08after exclusion of surrogateinterviews, maternalexposures, and otherpaternal exposures (nomultivariate models); noinformation on timing ofexposure relative togestationOlshanet al.1990casecontrolCases:200 histologicallyconfirmed U.S. Wilms’ tumorcases (less-commonsarcomatous subtype excluded)occuring from 1984–1986Controls:200 age- and areamatched population controlsA self-administeredquestionnaire on jobhistory was used toidentify lead exposed jobsand the years worked.OR (95% CI); no. of casesTiming of paternal lead exposure:preconception 1.1 (0.6–2.0); 37pregnancy 1.1 (0.6–2.4); 24postnatal 1.3 (0.6–2.8); 21Potential confounders:coexposuresOther limitations:control selection bias (52%response)05/08/03 RoC Background Document for Lead and Lead Compounds101ReferenceDesignStudy populationExposureEffectsCommentsKristensen andAndersen 1992cohort12,440 offspring of Osloprinters’ union members,followed from 1965–1987Union employmentrecords were used toidentify lead-exposedoccupations (compositors,monotype casters,stereotypers) and leadand solvent-exposedoccupations.SIR (95% CI); no. of casesCancer at age 0–14:lead 0.8 (0.2–2.3); 3lead & solvent 0.3 (0.0–1.4); 1Cancer at age 14+:lead 1.4 (0.6–2.6); 9lead & solvent 0.6 (0.2–1.4); 5Potential confounders:no control for other riskfactorsOther limitations:cancer type not specified,inadequate power (veryfew cases)05/08/03 RoC Background Document for Lead and Lead Compounds10205/08/03 RoC Background Document for Lead and Lead Compounds

103 

## 4 Studies of Cancer in Experimental Animals

IARC reviewed the carcinogenic potential of lead and lead compounds administered to mice, rats, and hamsters and concluded that there was sufficient evidence that lead subacetate is carcinogenic to mice and rats and that lead acetate and lead phosphate are carcinogenic to rats (IARC 1980, 1987). Most of the available carcinogenicity studies of lead in experimental animals were publishe d before 1980 and were included in the IARC review. A brief summary of the primary findings and data from these studies is presented below. Carcinogenicity studies that were not included in IARC’s review are discussed in
more detail.

Lead chromate compounds were not included in the IARC monographs for lead and lead compounds (IARC 1980, 1987) but were included in the monographs for chromium and chromium compounds (IARC 1973, 1990). Because the carcinogenic effects of lead chromates generally are associated with toxi city of chromium rather than lead, these compounds are not discussed in de tail in the following sections.

4.1 Mice
Lead compounds have been administered to mice in the diet, by intraperitoneal (i.p.) injection, by subcutaneous (s .c.) injection, by skin applic ation, and in drinking water.
Most of these studies have i nvestigated the carcinogenicity of lead administered to young adult mice; however, the two most recent studi es investigated the effects of lead on chemical- and viral-induced tumors (Blakley 1987) or in prenatal and neonatal mice exposed during gestation and lactation (Waalkes et al. 1995). The compounds studied include lead subacetate, lead acetate, lead naphthenate, lead chromate, and tetraethyl lead. The results from these studies are presented below.

4.1.1 Lead acetate or subacetate

Van Esch and Kroes (1969) fed lead subacetate at 0.1% and 1.0% in the diet to groups of 25 male and female Swiss mice for two year s. The 1.0% level was decreased to 0.5% beginning in the fourth mont h because of excessive toxicity; however, the authors reported that most mice in th e high-dose groups “died before tumors could be induced.” No renal tumors developed in the control group. Six male mice in the 0.1% group and one female mouse each in the 0.1% and 1.0% gr oups developed renal tumors (Table 4-1). Other tumors occurred but were not associated with lead exposure.

Groups of 20 male and female strain A/Str ong mice were given i.p. injections of lead subacetate dissolved in tricaprylin for 5 weeks (for total doses of 30, 75, and 150 mg/kg body weight [b.w.]) and observed for up to 30 weeks (Shimkin et al. 1977, Stoner et al. 1976). The incidence of pulmonary adenoma was significantly higher in the high-dose group than in vehicle controls or untreated controls (Table 4-1).

Using strain A mice, Poirier et al. (1984) investigat ed the inhibition of lead subacetateinduced lung tumors by magnesium and calci um acetate. Lead subacetate dissolved in tricaprylin was injected i.p. at 10 mg/kg b.w . (0.04 mmol/kg) alone or in combination with calcium acetate or magnesium acetate. Calcium acetate and magnesium acetate were05/08/03 RoC Background Document for Lead and Lead Compounds

104 administered at 1, 3, and 10 times the molar c oncentration of lead s ubacetate. Groups of 30 mice received three injections per week, for a total of 9 (m agnesium acetate studies) to 20 (calcium acetate studies) injections. Lead s ubacetate induced a sta tistically significant increase in lung tumors in strain A mice; however, simultaneous treatment with either calcium acetate or magnesium acetate at all molar ratios significantly decreased this response (Table 4-1).

Blakley (1987) investigated th e effects of lead on chemical - and viral-induced tumors in female Swiss mice. In the first experiment, l ead acetate was given in the drinking water at 0, 50, 200, or 1,000 μg/mL for 15 weeks beginning at three weeks of age. At six weeks of age, mice in each group received i.p. injections of 1.5 mg/g urethan or saline. Incidences of lung adenoma were reported at the e nd of the exposure period. In the second experiment, 8-week-old mice, with the same genetic background as in the first study, were given lead acetate in drinking wate r at 0, 50, or 1,000 μg/mL for 40 weeks and examined for lymphocytic leukemia of thym ic origin. These mice have a high incidence (approximately 50%) of spontaneous lymphocytic leukemia. No clinical manifestations of lead poisoning were observe d in either experiment, and neither body-weight gain nor water consumption was affected. Lead expos ure did not affect the number or size of pulmonary adenomas induced by urethan (Tab le 4-2). The spontaneous tumor incidence was less than 2 tumors per mouse in all trea tment groups injected with saline. In the second experiment, lead exposure increased incidences of viral- induced lymphocytic leukemia and tumor-related deaths (Table 4-3). The authors concluded that the immunosuppressive effects of lead allowed for increased expression of the murine lymphocytic leukemia virus.

A dose-related increase in renal prolifera tive lesions (including atypical hyperplasia, adenoma, and adenocarcinoma) was evident in B6C3F 1 mice following gestational and lactational exposure to lead (Waalkes et al. 1995). Pregnant B6C3F 1 mice were given lead (as lead acetate) in the drinking water ad libitum at 0, 500, 750 or 1,000 ppm from gestation day 12 to four weeks postpartum. These drinking-water levels of lead were estimated to provide doses of 0, 100, 150, or 200 mg/kg b.w. per day, respectively. After weaning, the offspring were grouped by sex ( 23 to 25 per group) and observed for up to 112 weeks. Other groups of offspring rece ived a tumor promoter (500 ppm sodium barbital) ad libitum in the drinking water for the bala nce of the study. Lead exposure did not affect litter size, growth of exposed o ffspring, or survival. A significant dose-related
trend was noted in total renal proliferative lesions in male progeny mice exposed to lead alone ( P < 0.001) or lead a nd sodium barbital ( P = 0.022). In addition, male mice in the high-dose group showed a significantly increased incidence of renal tubular cell adenoma and renal tubular cell atypical hyperplasia (Table 4-4). Female progeny mice exposed to lead alone showed a signif icant dose-related trend ( P = 0.017) in total re nal proliferative lesions; however, lesion inciden ces were not significantly elevated at any dose level (Table 4-4). In the control groups, atypical tubular hyperplasia occurred in one male mouse, but no tumors were observed. Postnatal exposure of the mice to sodium barbital did not promote tumor development. The author s noted that the renal tumors observed in this study developed without evidence of c oncurrent lead-indu ced nephropathy (i.e., intranuclear inclusion bodies, intersti tial fibrosis, or cystic hyperplasia).05/08/03 RoC Background Document for Lead and Lead Compounds105Table 4-1. Summary of carcinogenicitystudies of lead subacetate in miceTumor incidence (%)aKidneyLungStrainand ageExposureroute anddurationSex andno.bExposuregroupcAdenomaCarcinomaAdenomaMultiplicitydReferenceSwiss(5 wk)diet for 2 yr M (25)M (25)M (25)F (25)F (25)F (25)00.1%1.0% to 0.5%e00.1%1.0% to 0.5%e0 (0)2 (NR)0 (0)0 (0)1 (NR)0 (0)0 (0)4 (NR)0 (0)0 (0)0 (0)1 (NR)3 (NR)1 (NR)1 (NR)3 (NR)5 (NR)1 (NR)NRNRNRNRNRNRvan Esch and Kroes1969Strain A(6–8 wk)15 i.p.doses(3/wk),examined at30 wkM/F (19)M/F (18)M/F (17)M/F (12)M/F (15)untreatedvehicle30 mg/kg75 mg/kg150 mg/kgNRNRNRNRNRNRNRNRNRNR6 (31)8 (44)6 (35)5 (42)11 (73)0.28±0.070.5±0.120.35±0.090.5±0.141.47±0.38*Stoneret al.197605/08/03 RoC Background Document for Lead and Lead Compounds106Tumor incidence (%)aKidneyLungStrainand ageExposureroute anddurationSex andno.bExposuregroupcAdenomaCarcinomaAdenomaMultiplicitydReferenceStrain A(6–8 wk)20 i.p.doses(3/wk),examined at30 wk9 i.p. doses(3/wk),examined at30 wkM/F (26)M/F (26)M/F (20)M/F (23)M/F (18)M/F (16)M/F (21)M/F (29)M/F (20)M/F (1)M/F (13)M/F (18)vehiclevehicle + CAPb (10 mg/kg)Pb + CA (1:1)Pb + CA (1:3)Pb + CA (1:10)vehiclevehicle + MAPb (10 mg/kg)Pb + MA (1:1)Pb + MA (1:3)Pb + MA (1:10)NRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNRNR0.35±0.090.62±0.170.86±0.20*0.21±0.10†0.22±0.10†0.13±0.09†0.29±0.110.45±0.091.65±0.36*NRf0.08±0.08†0.28±0.11†Poirieret al.1984*P< 0.05 compared with vehicle controls.†Significantly less (P< 0.05) than in the lead subacetate group.aNR = not reported.bThe number of surviving animals except for van Esch and Kroes(1969), which reported only the initial number of animals.M/F = male and female not given separately; total number of animals reported.cPb + CA = lead subacetate plus calcium acetate (molar ratio) ; Pb + MA = lead subacetate plus magnesiumacetate (molar ratio)dThe average number of tumors per mouse±S.E.eDosage decreased because of high mortality.fOnly one of 30 animals survived.05/08/03 RoC Background Document for Lead and Lead Compounds

107 Table 4-2. Effects of lead acetate on body-wei ght gain and urethan-induced lung adenoma in
female Swiss mice

Lead
concentration (μg/mL) Weight gain

mean ± SE

(g/day) Tumors/mouse

mean ± SE (No. of mice) Tumor size

mean ± SE (mm)

0

50

200

1,000 0.18 ± 0.006

0.18 ± 0.004

0.17 ± 0.006

0.17 ± 0.005 36.0 ± 5.8 (22)

39.0 ± 6.0 (19)

49.6 ± 12.8 (24)

34.0 ± 4.9 (24) 0.71 ± 0.03

0.67 ± 0.04

0.70 ± 0.04

0.68 ± 0.02

Source: Blakley 1987.

Table 4-3. Effects of lead acetate on mortal ity and spontaneous lymphocytic leukemia in
female Swiss mice

Lead

conc. (μg/mL) Median
survival time (days) Mice surviving to

the end of

study a Leukemia deaths (%) a Other neoplasiarelated deaths b Survival probability c

0

50

1,000 223.5

170.6

165.5 20

13

10 24 (48)

34 (68)

38 (76) 2

0

1 0.007

0.0124 d

0.0034 d

Source: Blakley 1987.

a 50 mice per group. One surviving an imal in each group had evidence of leukemia at the end of the study.

b Mammary tumors (controls) and leukemia of non-thymic origin (high-dose group).

c Probability that the three treatment groups had the same survival distribution, based on the Lee-Desu statistic.

d Probabilities for lead-exposed groups are for pa irwise comparison with the control group.05/08/03 RoC Background Document for Lead and Lead Compounds

108 Table 4-4. Renal tubular cell proliferative lesions in B6C3F 1 mice following gestational and lactational exposure to lead acetate

Lesion incidence (%)

Exposure

group a (ppm) No. of
mice Atypical hyperplasia Adenoma Carcinoma Total

Males

0

500

750

1,000

SB

500 + SB

750 + SB

1,000 + SB 23

25

25

25

24

25

25

25 1 (4)

3 (12)

5 (20)

7 (28)*

2 (8)

2 (8)

5 (20)

2 (8) 0 (0)

0 (0)

0 (0)

5 (20)*

0 (0)

1 (4.0)

1 (4.0)

5 (20.0)* 0 (0)

1 (4)

1 (4)

0 (0)

0 (0)

0 (0)

1 (4)

1 (4) 1 (4)

4 (16)

6 (24)

12 (48)*

2 (8)

3 (12)

7 (28)

8 (32)*

Females

0

500

750

1,000

SB

500 + SB

750 + SB

1,000 + SB 25

24

25

25

25

25

25

25 0 (0)

0 (0)

0 (0)

4 (16)

0 (0)

0 (0)

0 (0)

1 (4) 0 (0)

0 (0)

1 (4)

0 (0)

0 (0)

0 (0)

1 (4)

0 (0) 0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

1 (4) 0 (0)

0 (0)

1 (4)

4 (16)

0 (0)

0 (0)

1 (4)

2 (8)

Source: Waalkes et al. 1995.

* P < 0.05, compared with appropriate controls.

a Concentrations of lead in the drinking water given to the dams; SB = Sodium barbital at 500 ppm in drinking water.

4.1.2 Lead naphthenate

Baldwin et al. (1964) tested the carcinogeni city of several engine oil additives, including lead naphthenate, in male albino mice. A 20% (v/v) solution of lead naphthenate in benzene was applied to the shaved backs of mice once or twice per week. The study was terminated at 648 days, for a total application of 6 mL. Lead naphthenate did no t induce a significant carcinogenic response in mouse skin. Only 2 of 59 mice de veloped benign skin tumors. Marked kidney damage was reported; however, the nature and extent of damage was not specified. Four mice developed renal tubular adenoma, and one mouse developed a renal carcino ma. No controls were
used.

4.1.3 Lead chromate

The IARC (1990) monograph includ ed only one study of mice expos ed to lead chromate. Two lymphomas and three lung adenocarcinomas were observed in 17 female NIH-Swiss weanling mice given intramuscular (i.m.) injections of 3 mg of lead chromate dissolved in trioctanoin05/08/03 RoC Background Document for Lead and Lead Compounds

109 every 4 months for 24 months. Lymphomas occurred in 1 of 15 untreated controls and 2 of 22 vehicle-injected controls, while lung adenocarcino mas occurred in 1 of 15 untreated controls and 1 of 22 vehicle-injected controls.

4.1.4 Tetraethyl lead

Subcutaneous administration of tetr aethyl lead to infant male and female Swiss mice resulted in significantly increased incidences of lymphoma in the females (Epstein and Mantel 1968). A single rangefinding dose of 2 mg on th e first day of life was lethal to all 69 mice tested before weaning. Mice received four divided doses of te traethyl lead dissolved in tricaprylin at a concentration of 1 mg/mL (109 mi ce, total dose of 0.6 mg) or 2 mg/mL (79 mice, total dose of 1.2 mg) between birth and 21 days of age. Both dose levels were toxic, resulting in 20% and 92% mortality in the low- and high-dose gr oups, respectively, before weaning. Malignant lymphomas were found between 36 and 51 weeks in 5 of 41 (12%) low-dose females, 1 of 26 (4%) low-dose males, 1 of 39 (3%) control males, and none of the female controls. No renal tumors or nephropathy were observed in the lead-exposed mice.

4.2 Rats
Lead compounds were administered to rats in the diet, by gavage, in drinking water, by injection, or through lactation. The compound s studied include lead subacet ate, lead acetate, lead phosphate, lead chromate, lead arsenate, and lead powder. Several studies also investigated the modifying effects of other compounds (e.g., di etary calcium, tumor promoters, and other carcinogens) on lead carcinogenic ity. The results from these st udies are presented below.

4.2.1 Lead acetate and lead subacetate

The carcinogenicity of lead acetate and lead s ubacetate in rats was re ported in the 1960s and 1970s (Boyland et al. 1962, van Esch et al. 1962, Shakerin and Paloucek 1965, Mao and Molnar 1967, Zawirska and Medras 1968, 1972, Ito et al. 1971, Ito 1973). The results from these studies
are summarized in Table 4-5. Other researchers investigated the carcinoge nic effects of lead compounds when co-administered with other co mpounds (see Section 4.2.4). In general, these early studies investigated onl y carcinogenic effects in the kidney; however, a few studies
examined other tissues.05/08/03 RoC Background Document for Lead and Lead Compounds110Table 4-5. Summary of carcinogenicity studies of lead subacetate and lead acetate in rats conducted before 1980Kidney tumor incidences (%)aStrainandinitialageCompound,exposureroute, anddurationSexband no.ExposuregroupAdenomaCarcinomaTotalCommentsReferenceWistar(10 wk)lead acetateor sedormid,diet, 1 yrM (20)M (20)0.5% sedormidc1.0% leadc0 (0)1 (6.3)1 (5.9)d14 (87.5)1 (5.9)d15 (93.8)Percentages based on animals surviving atleast 320 days (17 in sedormid group, 16 inlead group). No untreated control group.Boylandetal.1962Wistar(weanling)leadsubacetate,diet, 24 to 29moM/F (55)M/F (32)M/F (24)00.1%1%0 (0)8 (25)7 (29.2)0 (0)3 (9.4)6 (25)0 (0)11 (34.4)13 (54.2)Study duration of 29 months for 0.1% dietand 24 months for 1% diet. Tumors wereapproximately equally divided betweenmales and females.van Eschetal.1962Wistar(young)leadsubacetate,diet, 92 wkNR (40)NR (40)00.5%–1.0%0 (0)NR0 (0)NR0 (0)NRData reported in a meeting abstract. Treatedrats primarily developed adenomasbeginning at six months increas in size andnumber thereafter. A few adenocarcinomas,hypernephromas, or undifferentiatedcarcinomas were observed.ShakerinandPaloucek1965Wistar(NR)leadsubacetate,diet, up to677 daysM (20)M (40)01%0 (0)NR0 (0)NR1 (5)31 (77.5)The tumor in the control group was a roundcell sarcoma. Tumor incidence wascorrelated with exposure duration. All 12animals exposed to leadfor 500 days or moredeveloped tumors.Mao andMolnar 1967Wistar(NR)lead acetate,diet, 18 moM/F (32)M/F (126)03–4 mg/day0 (0)55 (43.7)0 (0)17 (13.5)0 (0)72 (57.1)Leydig-cell tumors of the testicles werereported in 23/94 treated male rats, but theincidence in controls was not reported.Zawirskaand Medras1968Wistar(6–8 wk)leadsubacetate,diet, 48 wkM (10) 1.5% 6 (60) 4 (40) 10 (100)The carcinomas included one clear-cellcarcinoma and three dark cell carcinomas.Itoet al.1971Wistar(30 wk)lead acetate,diet, 60–504daysM/F (62)M/F (94)03 mg/day0 (0)12 (12.8)0 (0)0 (0)0 (0)12 (12.8)Other tumors included 10 cerebral gliomasand 17 pituitary, 11 thyroid, 5 parathyroid,15 adrenal, 11 prostatic, and 8 mammaryadenomas.Zawirskaand Medras197205/08/03 RoC Background Document for Lead and Lead Compounds111Kidney tumor incidences (%)aStrainandinitialageCompound,exposureroute, anddurationSexband no.ExposuregroupAdenomaCarcinomaTotalCommentsReferenceWistar(6–8 wk)leadsubacetate,diet, 23–48.5wkM (13)M (11)M (11)1.5%1.5% + nephe1.5%0 (0)NRNR0 (0)NRNR0 (0)2 (18.2)9 (81.8)First two groups were treated for 23 weeks,and the third group was treated for 48.5weeks. Rats in the second group wereunilaterally nephrectomized. Of the 11 renaltumors, 7 were adenomas and 4 werecarcinomas.Ito 1973aNR = not reported.bM/F = male and female not given separately; total number of animals reported.cAfter one year, surviving animals were placed on the basal dietand were sacrificed when theybecame ill or had a palpable tumor. Sedormid was used to test thehypothesis that porphyrinuria may be responsible for lead-induced renal tumors. Both lead and sedormid caused chronic cystic nephritis.dEpidermoid carcinoma of the renal pelvis that was not likely related to treatment.eneph = nephrectomized.05/08/03 RoC Background Document for Lead and Lead Compounds

112 Kasprzak et al . (1985) investigated th e interaction of dietary calcium with lead carcinogenicity in 4-week-old male Sprague-Dawley rats. Rats were divided into seven groups (30 per group) and fed diets containing 0 or 1% lead subacetate and 0, 0.3%, 1%, 3%, or 6% calcium acetate for 79 weeks. Body weight gains were significantly depressed in lead-exposed animals, and the depressive effect was enhanced with increasi ng exposure to calcium acetate. Exposure to lead
and calcium acetate also increased the organ/body weight ratios for the liver and kidneys. Kidney
tumors were not observed in the control or ca lcium-acetate-only groups. Renal tumors occurred in approximately 45% of the lead-only group and in 62.1% to 78.6% of the lead and calcium acetate groups (Table 4-6). Bilateral tumors occu rred in 48% of the tumor-bearing rats. Primary tumors in other organs were not observed in th e lead-only group but occurred in a few animals in the lead- and calcium-exposed groups (Table 4-6).

Table 4-6. Tumor incidence in male Sprague-Da wley rats fed lead subacetate (PbSA) and calcium acetate (CA)

Kidney tumor incidence (%)

Exposure group (%) No. rats
at risk a Adenoma Adenocarcinoma Total Other tumors (no.) b

Control

CA (3)

PbSA (1)

PbSA (1) + CA (0.3)

PbSA (1) + CA (1)

PbSA (1) + CA (3)

PbSA (1) + CA (6) 30

29

29

30

29

30

28 0 (0)

0 (0)

11 (37.9)

16 (53.3)

11 (37.9)

15 (50.0)

15 (53.6) 0 (0)

0 (0)

2 (6.9)

5 (16.7)

7 (24.1)

7 (23.3)

7 (25.0) 0 (0)

0 (0)

13 (44.8)

21 (70.0)

18 (62.1)

22 (73.3)*

22 (78.6)* schwannomas (2)

odontoma (1)

none
HCA (1), SCC (1), PAP (?)

PC (1), PAP (?)

osteoma (1)

none
Source: Kasprzaket al. 1985.

* P < 0.05 (compared to lead only group)

a Rats surviving at least 58 weeks.

b HCA, hepatocellular adenoma; SCC, squamous-cell carci noma; PAP, papilloma; PC, pituitary carcinoma; (?), a total of three papillomas reported in groups 4 and 5 combined.

Bogden et al. (1991) also investigated the modifying effects of dietary calcium on lead tissue concentrations, blood pressure, and incidences ofkidney tumors in rats. Forty-eight five-weekold male Wistar rats were randomly assigne d to groups fed a low- calcium (0.2%) or highcalcium (4.0%) diet and given drinking wate r containing 0, 1.0, or 100 μg/mL lead for 31 weeks. Lead acetate trihydrate was used in the treatment groups, and sodium acetate trihydrate was used in the control groups. The lead concen trations were expected to produce blood lead
concentrations similar to those found in individua ls in the U.S. population with low or moderate exposure to lead. Tissue lead c oncentrations were not lower in groups on the high-calcium diet. All rats exposed to high calcium and high l ead concentrations developed hyperplasia or transitional cell carcinoma in the kidney. These lesions were not observed in the other groups.
The authors concluded that the high-calcium diet enhanced lead-induced renal carcinogenesis.05/08/03 RoC Background Document for Lead and Lead Compounds

113 4.2.2 Lead phosphate

IARC (1980) reviewed three carcinogenicity studie s of lead phosphate pare nterally administered to rats (Zollinger 1953, Baló et al. 1965, Roe et al. 1965). No other studies with lead phosphate
were identified. Renal tumors occu rred in 36% to 66% of the al bino rats given lead phosphate but were not observed in controls (Table 4-7).

4.2.3 Lead chromate

IARC (1990) reviewed several stud ies of lead chromates adminste red to rats by interbronchial implantation, intrapleural implantation, s.c. inj ection, or i.m. injection. Bronchial carcinomas were observed in a few rats (1% or less) admi nistered various lead chromate compounds via interbronchial implantation, but the incidences were not statistically significant. Following intrapleural administration, implan tation-site tumors (tumor type unspecified) occurred in 3 of 34 rats after 27 months, compared with 0 of 34 in the control gr oup. In contrast, injection-site sarcomas were frequent in rats given a single s.c. injection of lead chromate (26/40, 65%), basic lead chromate (27/40, 67.5%), or molybdenum orange (a mixture of lead chromate, sulfate, and molybdate) (36/40, 90%), but were not observed in 60 control animals. Results from i.m. injection studies were inconsistent. Injection-site tumors were observed in 1 of 33 (3%) rats in one study and 31 of 47 (66%) in another. No inje ction-site tumors occurred in controls. In addition, renal-cell carinomas occurr ed in 3 of 23 (13%) rats inject ed i.m. with 8 mg of lead chromate once per month for nine months. The IARC (1990) Working Group noted that the renal tumors may have been attribut able to the lead content.

4.2.4 Other inorganic lead compounds

Although studies with lead acetate, lead subaceta te, and lead phosphate show clear evidence of carcinogenicity in rats, other le ad compounds have not been asso ciated with carcinogenicity. IARC (1980) reviewed the carcinogenicity of lead arsenate and lead carbonate administered in the diet, lead nitrate administered in drinking wa ter, and lead powder administered by gavage or i.m. injection. These studies are summarized brie fly below. No additional studies of these or other lead compounds were identified.

No tumors were found in 49 young male white rats fed 0.1% lead arsenate or in 55 rats fed 0.1% lead carbonate for two years. However, th e authors reported kidne y changes, including cytomegaly, vesiculation of nuclei, and accumu lation of brown granules in the convoluted tubules (Fairhall and Miller 1941).

A study of male and female Wistar rats fed lead ar senate in the diet at a concentration of 463 or 1,850 ppm for two years did not provide cl ear evidence of carcinogenicity (Kroes et al. 1974). Eighty animals (40 of each sex) were include d in the low-dose group and 48 (19 females and 29 males) in the high-dose group. No differences were observed between groups in the numbers of malignant or benign tumors. The incidence of ma lignant tumors was 1 of 28 (3.6%) in the highdose group and 6 of 78 (7.7%) in the low-dose group, compared with 11 of 98 (11%) in controls. The authors suggested that the only tumors that may have been i nduced by lead arsenate were a
renal cortical adenoma and a bile-duct carcinoma found only in the high-dose group.

Male Long-Evans rats exposed to lead (a s lead nitrate) in drinking water at 25 μ g/L from weaning until death did not show increased mortality or tumor incidence (Schroeder et al. 1970).05/08/03 RoC Background Document for Lead and Lead Compounds

114 Tumors, unspecified with respect to location or type, were observed in 7 of 43 (16%) exposed rats and 10 of 50 (20%) controls.

Lead powder administered by i.m. injection or ga vage did not increase tumor incidence in male or female F344 rats (Furst et al. 1976). Rats received nine monthl y i.m. injections of 10 mg of lead powder, followed by three monthly injections of 5 mg. An injection-site sarcoma observed in one female rat was thought to be a random occurrence. The incidenc es of lymphoma or lymphocytic leukemia in exposed rats did not di ffer from those in controls. When lead powder was administered by gavage in corn oil (10 mg twice a month for 12 months), no tumors occurred in the gastrointestinal tract or ki dneys. Lymphoma and leukemia occurred in both exposed and control animals; however, the in cidences were not si gnficantly different.

4.2.5 Co-administration with other compounds

Three studies from the same laboratory (Shakerin et al. 1965, Hass et al. 1967, Oyasu et al. 1970) investigated the interaction of dietary le ad subacetate with 2-ac etylaminofluorene (2- AAF). Kidney, liver, urinary blad der, brain, and other tumors we re reported; however, most of these occurred in rats given both 2-AAF and lead. Shakerin et al. (1965) reported a higher incidence of hepatic and renal car cinomas with metastasis to the lungs in rats fed both lead subacetate and 2-AAF than in gr oups fed either compound alone. Hass et al. (1967) reported that the combination of 2-AAF, lead subacetate, and lin seed oil increased the an aplastic character of hepatocellular carcinomas but did not significantly increase their in cidence. No other significant interactions were reported. However, lead suba cetate was associated with kidney and brain tumors (Table 4-8).

Several studies published after the IARC (1980) review investig ated the promoting or cocarcinogenic effects of lead ad ministered to rats. Hiasa et al. (1983) investigated the promoting
effects of lead subacetate in male Wistar rats treated with N -ethyl- N -hydroxyethylnitrosamine (EHEN). The animals were divided into six treatm ent groups that received diets containing: (1) no EHEN or lead subacetate (controls), (2) 500 ppm EHEN, (3) 1,000 ppm EHEN, (4) 1,000 ppm lead subacetate, (5) 1,000 ppm EHEN followed by 1,000 ppm l ead subacetate, and (6) 500 ppm EHEN followed by 1,000 ppm lead subacetate. EHEN was give n during the first two weeks of the study, lead acetate from week 3 to week 22, and the contro l diet from week 23 to week 32. Animals were sacrificed at 32 weeks and examined for kidney tumors. No tumors were observed in groups 1, 2, or 4. Exposure to lead subacetate significantly increased the incidence and size of renal-cell tumors induced by EHEN (Table 4-9) . In addition, hepatocellu lar carcinomas were found in two rats in group 3 and one rat each in groups 5 and 6.05/08/03 RoC Background Document for Lead and Lead Compounds115Table 4-7. Summary of carcinogenicitystudies of lead phosphate in ratsaKidney tumor incidence (%)aStrainbExposureroute anddurationSex andno.ExposuregroupAdenomaCarcinomaTotalCommentsReferenceAlbinos.c., up to 16mo.NR (40)NR (29)020 mg/wk0 (0)NR0 (0)NR0 (0)19 (66)Total doses ranged from 40 to 760 mg. Tumorsin the renal cortex occurred in rats survivingmore than 10 mo and receiving between 120and 680 mg. Renal papilloma and cystadenomaalso reported.Zollinger1953cAlbino s.c., 18 mo. NR (20)NR (80)020 mg/wk0 (0)29 (36)0 (0)0 (0)0 (0)29 (36)The total dose was 1.3 g, and adenomas firstappeared after 354 days.Balóet al.1965cAlbinoChesterBeattys.c. and i.p.,34 wkM (24)M (23)M (23)M (3)029 mgd145 mge450 mgf0 (0)0 (0)NR2 (67)0 (0)0 (0)6 (26)0 (0)2 (8)g0 (0)14 (61)h2 (67)All groups began with 24 animals. Percentageis based on animals surviving at least 200 days.Treatment groups received 4 s.c. injectionsfollowed by 21 to 25 i.p injections withvariable periods of no treatment during thestudy (see footnotes). Most of the tumors werecuboidal-cell, tubular, or papillary adenomas oradenocarcinomas arising in the renal cortex.Several non-renal tumors occurred but were notassociated with lead.Roeet al.1965aNR = not reported.bAges not reported.cAs cited in IARC (1980). These papers were not published in English.dWeekly injections of 1 mg: 4 s.c. injections + 7 i.p. injections+ no treatment for 3 wk + 4 i.p. injections + no treatment for2 wk, + 14 i.p. injections.eSame as above except dose was 5 mg per injection.fFour s.c. injections (25 mg) + 7 i.p.injections (25 mg) + no treatment for9 wk, + 14 i.p. injections (12.5 mg).gIncludes one undifferentiated malignant tumor and one transitional cell carcinoma arising in the renal pelvis.hIncludes one undifferentiated malignant tumor and 13 adenomas or adenocarcinomas.05/08/03 RoC Background Document for Lead and Lead Compounds116Table 4-8. Summary of carcinogenicity studies of lead subacetate co-administered with 2-AAF in ratsaKidney tumor incidence (%)aStrainand ageExposureroute anddurationSexbandno.Exposure groupcAdenomaCarcinomaTotalCommentsReferenceWistar(NR)(NR)(NR)M (40)2-AAF (0.06%)Pb (1%)Pb (1%)+ 2-AAF (0.06%)NRNRNRNRNRNRNRNRNRReported incidences of hepaticand renal tumors in combinedgroup either lead subacetate or2-AAF groups alone.Shakerinetal.1965SpragueDawley(6–8 wk)diet, 30–52wkdiet, 52–74wkM (32)M (13)M (11)M (32)M (32)M (11)M (39)M (42)2-AAF + indolePb + indolePb + LO + indolePb + LO + indole + 2-AAF2-AAF + indolePb + indolePb + LO + indolePb + LO + indole + 2-AAF0 (0)8 (61.5)0 (0)10 (31.3)0 (0)11 (100)20 (51.3)19 (45.2)0 (0)3 (23.1)1 (9.1)11 (34.4)0 (0)8 (72.3)13 (44.8)14 (33.3)0 (0)NRNRNR0 (0)11 (100)NRNRLead acetate concentrations were0.5% to 1% of the diet. Indole(1.6%) was added to counteract2-AAF (0.06%) liver toxicity.Brain tumors (gliomas) occurredin 3, 2, 4, and8 animals in therespective treatment groups(including interim sacrificeanimals) but were consideredspontaneous tumors.Hasset al.1967SpragueDawley(6 wk)M/F (325)M (17)M (41)M (72)controlsPb (1%)Pb + indole (1.6%)Pb + indole + 2-AAF(0.06%)0 (0)NRNRNR0 (0)NRNRNR0 (0)13 (76.5)25 (61.0)36 (50.0)Gliomas were observed in onecontrol animal (0.3%) and in 11of 130 (8.5%) rats in the leadtreatment groups (P< 0.05).Gliomas occurred in 2, 3, and 6rats in the Pb only, Pb + indole,and Pb + indole + 2-AAFtreatment groups, respectively.Combining lead and 2-AAF didnot increase tumor incidences.Oyasuet al.1970aNR = not reported.bM/F = male and female not given separately; total number of animals reported.cLO = linseed oil containing a “lead drier” with 0.2% lead.05/08/03 RoC Background Document for Lead and Lead Compounds117Table 4-9. The promoting or co-carcinogenic effects of lead acetate or lead subacetate in ratsStrainand ageExposureroute anddurationSex andno.Exposure group (ppm)aKidney tumorsincidence (%)CommentsReferenceWistar(7 wk)diet, 22 wk M (24)M (24)M (18)M (24)M (17)M (22)ControlEHEN (500)EHEN (1,000)PbSA (1,000)EHEN (1,000) + PbSA (1,000)EHEN (500) + PbSA (1,000)0 (0)0 (0)9 (50)*b0 (0)17 (100)*c10 (45)*dSurviving animals were sacrificed at 32weeks. Incidences of renal tumors > 3 mm indiameter were 0%, 0%, 10%, and 71% intumor-bearing animalstreated with EHENalone, lead subacetate alone, 500 ppm EHENplus lead, and 1,000 ppm EHEN plus lead,respectively.Hiasaet al.1983SpragueDawley(weanling)drinkingwater, 76 wkM (7)M (8)M (7)M (10)M (16)ControlEU/NaNO2EU/NaNO2+ PbA (26)EU/NaNO2+ PbA (2,600)PbA (2,600)0 (0)0 (0)0 (0)6 (60)13 (81)The first renal tumor was observed at 54weeks. All animals in the groups treated withEU/NaNO2developed one or more tumortypes (lymphosarcoma being the mostcommon), but renal tubule carcinoma wasthe only tumor observed in the lead-onlygroup.Kolleret al.1985*P< 0.05.aEHEN =N-ethylN-hydroxyethylnitrosamine; EU/NaNO2= ethyl urea and sodium nitrite; PbSA =lead subacetate; PbA = lead acetate.bCompared with the control group (χ2test).cCompared with the EHEN 1,000-ppm group (χ2test).dCompared with the EHEN 500-ppm group (χ2test).05/08/03 RoC Background Document for Lead and Lead Compounds

118 Koller et al. (1985) investigated the carcinogenic effects of lead acetate administered with sodium nitrite and ethyl urea to male Sprague-Dawley rats. The five treatment groups included the following: (1) untreated controls, (2) ethyl urea (EU) and sodium nitrite (NaNO 2 ) (3) ethyl urea, sodium nitrite, and 26 ppm lead as lead acetate, (4) ethyl urea, sodium nitrite, and 2,600 ppm lead, and (5) 2,600 ppm lead. Groups 1 through 4 had 10 animals and group 5 had 16 animals. Lead was administered in the drinking water for 76 weeks. Ethyl urea (6.36 g/kg) and sodium nitrite (2 g/kg) (precursors of the carcinogenic agent ethylnitrosou rea) were mixed in the diet and administered for 20 weeks beginning 28 weeks after initiation of l ead exposure. Early deaths from pneumonia reduced the effective group sizes to 7, 8, a nd 7 for groups 1, 2, and 3, respectively. At the end of the study, all rats fed ethyl urea and s odium nitrite (groups 2, 3, and 4) had tumors. Lymphosarcoma was the most prevalent, with an incidence of at le ast 50% in each of these groups. Only kidney tumors were observed in group 5 (lead only). No kidney tumors were detected among the controls, the EU+NaNO 2 group (group 2), or the lowdose lead and EU+NaNO 2 group (group 3). Renal tubular carcinomas were observed in both groups receiving lead at 2,600 ppm (Table 4-9). Howeve r, tumor incidences were not increased by co-administration of lead with urea and sodium nitrite.

Tanner and Lipsky (1984) studi ed the effects of lead ace tate on induction of renal carcinogenesis by N -(4'-fluoro-4-biphenyl)acetamide (F BPA) in male Fischer-344 rats. Four groups of 50 rats each were used; howev er, mortality from acute toxicity was high in the treatment groups. Five to 10 rats were sacrificed in each group after 16, 24, 36, and 52 weeks of exposure and examined for ki dney tumors. Group 1 (controls) was fed a semi-synthetic diet, group 2 was fed the contro l diet with 400 ppm lead as lead acetate, group 3 was fed the control diet with 10,000 pp m lead as lead acetate, and group 4 was
fed the control diet with 400 ppm FBPA plus 10,000 ppm lead as lead acetate. No lesions were observed in the controls, but karyom egaly, hyperplasia, and microscopic nodules were seen in all lead-expos ed groups. Renal adenocarcinoma occurred in groups 2, 3, and 4 after 36, 52, and 24 weeks, respectively. Ki dney tumor incidence was higher in group 4 (lead acetate and FBPA) than in either the lead-only or FBPA-only group (Table 4-10). Exposure to lead acetate gene rally accelerated the onset a nd development of all renal lesions; however, karyocytomegaly was not co rrelated with the later appearance of hyperplasia, microscopic nodules, or adenocarcinomas. These researchers concluded that lead probably was acting synergistically with FBPA as a co-carcinogen by accelerating the neoplastic process in the pr oximal tubule ep ithelial cells.05/08/03 RoC Background Document for Lead and Lead Compounds

119 Table 4-10. Co-carcinogenic effects of lead acetate administered with FBPA to male
Fisher-344 rats

Renal lesion incidence (%)

Treatment group (ppm) No. of

rats Treatment duration (wk) Hyperplasia Microscopic
adenoma Adenocarcinoma

(1) Control a 5–10

5–10

5–10

5–10 16

24

36

52 0

0

0

0 0

0

0

0 0

0

0

0

(2) FBPA (400) 7

7

7

5 16

24

36

52 4 (57)

7 (100)

5 (71)

3 (60) 0

2 (29)

3 (43)

3 (60) 0

0

4 [57]

4 (80)

(3) PbA (10,000 as elemental Pb) 8

8

10

5 16

24

36

52 4 (50)

4 (50)

10 (100)

3 (60) 0

0

1 (10)

1 (20) 0

0

0

1 (20)

(4) FBPA (400) + PbA (10,000 as elemental Pb) 8

9

5

5 16

24

36

52 8 (100)

9 (100)

5 (100)

5 (100) 3 (38)

6 (67)

5 (100)

4 (80) 0

1 (11)

4 (80)

5 (100)

Source: Tanner and Lipsky 1984.

a The number of control rats sacrificed at each interval was not reported but was between 5 and 10.

4.3 Hamsters
In male and female golden hamsters (45 or 46 per group) fed cont rol diet or lead
subacetate at 0.1% and 0.5% in the diet fo r up to two years, lead exposure did not significantly increase the frequency of re nal tumors, although pleomorphic cells and
intranuclear inclusion bodi es were found in the proximal renal tubules. The overall incidences of other tumors and hyperplasias in the low-dose, hi gh-dose, and control groups were 25 of 46 (54%), 18 of 46 (39%), and 36 of 45 (80%), respectively (van Esch and Kroes 1969).

Four groups of Syrian golden hamsters (15 pe r sex) were given 10 weekly intratracheal injections of lead oxide (1 mg), benzo[ a ]pyrene (1 mg), or a combination of lead oxide and benzo[ a ]pyrene (1 mg of each). Animals were sacrificed when moribund or 60 weeks
after the first treatment. The hamsters did not develop any lung tumors when administered either lead oxide or benzo[ a ]pyrene alone; however, lead oxide induced hyperplastic and squamous metaplastic foci in the alveolar regi on. Atypical epithelial proliferations in the lungs (11 adenomas , 1 adenocarcinoma) were observed only in animals given the combination of lead oxide and benzo[ a ]pyrene. The investigators05/08/03 RoC Background Document for Lead and Lead Compounds

120 concluded that lead oxide exerted a co-carcinogenic effect with benzo[ a ]pyrene in the lungs (Kobayashi and Okamoto 1974).

4.4 Monkeys
Krugner-Higby et al. (2001) reported on a cas e of chronic myelocytic leukemia that may have been related to lead exposure in a juvenile female rhesus macaque. This monkey was part of a study that inve stigated the behavioral eff ects of subclinical neonatal exposure to lead. Lead acetat e was administered in milk formula during the first six months postpartum (beginning on day 8). After weaning, lead acetate was given daily in a fruit-flavored vehicle for 1.5 years to achie ve a blood lead level of 35 μg/dL. At 25 months of age, an increased white blood ce ll count and immature white blood cells were detected during a routine complete blood count . The animal was monitored and received chemotherapy treatments but was euthanized four months later because of deteriorating clinical conditions. No evidence of past or pres ent viral infection or other risk factors for
leukemia was observed. The authors concluded th at the possible role of lead exposure in chronic myelocytic leukemia should be investigated.

4.5 Summary
Both soluble (lead acetate and lead subacet ate) and insoluble (lead phosphate) lead compounds were found to be carcinogenic in rats and/or mice by a variety of exposure routes, including oral, subcutaneous, intramus cular, transdermal, and transplacental, and
translactational. Inhalation carcinogenicity studies of l ead compounds have not been conducted in experimental animals.

Other lead compounds found to be carcinogenic in experimental animals include lead chromates and tetraethyl lead. Exposure to l ead chromates increased the incidence of injection-site sarcomas in rats, but these e ffects were likely due to chromate. However, renal-cell carcinomas were reported in one st udy of rats administered lead chromate by i.m. injection. Female infant Swiss mice admi nistered tetraethyl l ead by s.c. injection developed malignant lymphomas, but this e ffect was not observed in male Swiss mice.

Most of the studies of in organic lead compounds focused on kidney toxicity and carcinogenicity; therefore, comp lete histopathological exam inations were not conducted. However, the few studies that examined tissues other than the kidney found little
evidence that lead induced tumors. The available data indicate that the primary target site for lead-induced neoplasia in experiment al animals is the kidney (adenoma and adenocarcinoma), but increased incidences of cerebral glioma and lung adenoma were reported in some studies.

Lead subacetate was reported to enhance li ver and kidney tumorige nicity of 2-AAF in one study but not in two others and was shown to promote renal tumors in Wistar rats administered EHEN. In other studies, lead acetate increased the incidence of viralinduced lymphocytic leukemia in mice and wa s co-carcinogenic when administered with FBPA to F344 rats. However, lead acetate di d not increase tumor incidences in SpragueDawley rats when co-administered w ith ethyl urea and sodium nitrite.05/08/03 RoC Background Document for Lead and Lead Compounds

121 Overall, renal tumors were observed in male and female rats and mice exposed to lead compounds, and were not always accompan ied by chronic lead-induced nephropathy.05/08/03 RoC Background Document for Lead and Lead Compounds

12205/08/03 RoC Background Document for Lead and Lead Compounds

123 

## 5 Genotoxicity

Numerous studies have been conducted to determine whether lead compounds are genotoxic and, if so, by what mechanism(s). Most of these studies were performed before 1990. A comprehensive review by the Agency fo r Toxic Substances and Disease Registry (ATSDR 1999) summarized their results, concluding that various inorganic lead compounds (lead acetate, chloride, and nitrate) were not genotoxic in microorganisms, with and without metabolic activation, ba sed on various end points (mutations, DNA modification, and recombination). Conversely, in vitro assays using mammalian test systems (Syrian and Chinese hamster ovary cells) gave conflicting test results when cells
were examined for chromosomal aberrations. In vivo studies using Drosophila melanogaster and various mammalian model systems also gave conflicting results concerning the genotoxic effects of lead aceta te and lead nitrate. Evaluation of the genotoxicity of lead exposu re in humans focused on in vitro and in vivo studies of
chromosomal aberrations and sister chromatid exchange in lymphocytes from healthy individuals and from occupationally or e nvironmentally exposed individuals. These studies also gave conflicting results. ATSDR concluded that the mechanism(s) of the genotoxicity of lead probably was indirect (see Section 6 for a discussion of lead’s mechanism of action).

The literature through 1987 concerning the ge notoxicity of lead compounds also was extensively reviewed by IARC (1972, 1973, 1976, 1980, 1987). The IARC reviews concluded that divalent lead compounds (lead acetate and lead ch loride) reacted with purified DNA and decreased the fidelity of DNA replication in vitro , but were not mutagenic in bacterial test systems and di d not enhance mitotic recombination in the Saccharomyces cerevisiae D3 assay. In plants, lead acet ate (at concentrations of 20 to 30 mM) induced chromosome aberrations in Allium cepa root tips, and lead chloride (0.1 mM) was weakly mutagenic in rice seeds. In vitro and in vivo studies using mammalian systems yielded conflicting results for the genotoxicity of lead compounds.

Many factors contribute to the conflicting re sults concerning the genotoxic effects of
lead. These factors include differences not only in model systems employed and end points used to determine genotoxicity, but also in the lead compounds used. As discussed in Section 1, lead is highly reactive a nd forms numerous compounds that have very different physical-chemical properties. One im portant property in bi ological systems is solubility. Lead compounds vary greatly in solubility: compounds such as lead acetate, lead chloride, and lead nitrate are extremely soluble in water, with solubility constants (K sp ) of 2 x 10 -2 , 1 x 10 -4 , and 2 x 10 -2 , respectively, whereas ot her lead compounds, such as lead chromate and lead sulfide, are virtually insoluble in water (K sp of 1.7 x 10 -14 and

1 x 10 -28 , respectively). Solubility affects the bi oavailability of these compounds. Humans are occupationally and environmentally expos ed to numerous lead compounds over the course of a lifetime. Likewise, personal ha bits such as smoking, alcohol, and drug intake can influence genotoxicity data obtained in human subjects, and it is difficult to account for the effects that these cofactors might have on lead genotoxicity. This section reviews relevant genotoxicity data reported since 1989.05/08/03 RoC Background Document for Lead and Lead Compounds

124 5.1 Prokaryotic systems: Induc tion of mutations in Salmonella typhimurium
, Escherichia coli , and Serratia marcescens
Maslat and Haas (1989) determined the mutage nic effects of lead bromide, a combustion product of the gasoline additive s TEL and 1,2-dibromoethane, in Serratia marcescens

, Escherichia coli KMBL 1851, and the Salmonella typhimurium tester strains TA 1535 (point mutations) and TA 1537 (frameshift mutations). S. marcescens mutants were scored on their inability to produce the pigment prodigiosin, E. coli mutants were scored for resistance to rifampicin, and S. typhimurium mutants were scored for histidine auxotrophy. Bacteria were exposed for various ti mes (not reported) to concentrations of
PbBr 2 ranging from 1.91 to 4.63 mM for S. marcescens , 1.91 to 3.27 mM for E. coli, and 0.5 to 68 μg/plate for S. typhimurium. The frequency of white colonies arising from S.

marcescens exposed to PbBr 2 ranged from 0.42 ± 0.01% to 2.0 ± 0.10 % for exposure at
1.91 and 4.63 mM PbBr 2 , respectively. The mutation frequency for non-exposed controls was 0.05%. The frequency of rifampicin-resist ant mutants arising following exposure of
E. coli to 3.27 mM PbBr 2 was 0.26% x 10 -4 (non-exposed control = 0.0066% x 10 -4 ). The
number of S. typhimurium TA 1535 revertants ranged from 0 to 977 after plating on
PbBr 2 medium containing 0.5 and 34 μg of PbBr 2 , respectively. No significant increase in
revertants was seen with S. typhimurium strain TA 1537 (see Table 5-1).

5.2 Plants: in vivo assays Reddy and Vaidyanath (1978) investigated th e mutagenic activity of metallic salts, including lead chloride, on chlo rophyll mutations in rice. Rice seeds were exposed to a

10 -4 M aqueous solution of lead chloride fo r 24 hours. The pooled results of three replicates indicated mutant frequencies of 0.65% in the M1 and 0.04% in M2 generations. These values represent relatively weak muta genic acticity compared with that reported for other metallic salts, including barium (6.36% in the M1 and 0.68% in the M2) and cadmium (5.23% in the M1 and 0.46% in the M2).

Sandhu et al. (1989) evaluated the clastogenic ity of lead tetraacetate in the Tradescantia micronucleus assay, using Tradescantia paludosa clone 4430, as described by Ma et al. (1983). Plant cuttings were exposed fo r 30 hours by hypotonic uptake through stems, with no time for recovery. Results were expre ssed as micronuclei per 100 tetrads. Of the compounds tested (aldrin, ar senic trioxide, 1,2-benz[ a,h ]anthracene, dieldrin, heptachlor, lead tetraacetate, and tetrachlo roethylene), lead tetraacetate was the most clastogenic, inducing 17.79 ± 8.56, 18.93 ± 2.90, and 13.07 ± 5.50 micronuclei/100 tetrads at concentrations of 0.44, 2.55, and 11.75 ppm, re spectively. Micronucleus formation was significantly greater ( P < 0.05) than in the solvent control (2.90 ± 2.0).05/08/03 RoC Background Document for Lead and Lead Compounds125Table 5-1. Genotoxicity of leadcompounds in prokaryotic systemsResultsaSpecies (test system)End pointWithmetabolicactivationWithoutmetabolicactivationCompoundConcentrationbReferencelead acetate NABruce and Heddle 1979c,Dunkelet al.1984clead nitrate 22–180 μM Kharab and Singh 1985clead chromate 0.2 mg Nestmannet al.1979cS. typhimuriumE. coliBacillus subtilismutation orDNAmodification– –lead chloride andacetate25 mM Nishioka 1975cS. typhimurium(TA 1535)S. typhimurium(TA 1537)E. coli(KMBL 1851)S. marcescensmutation ND +–++lead bromide 0.5–68 μg/plate0.5–68 μg/plate1.91–3.27 mM1.91–4.63 mMMaslat and Haas 1989lead chloride NA Fukunagaet al.1982clead nitrate 22–180 μM Kharab and Singh 1985clead chromate 25 mM Nestmannet al.1979cS. cerevisiaegene conversionor mitoticrecombination– –lead acetate 5% (v/v) Simmon 1979a, 1979bcSource: ATSDR 1999.aND = not determined.bNA = not available.cNot reviewed in the text; source: ATSDR 1999.05/08/03 RoC Background Document for Lead and Lead Compounds

126 Ma et al. (1992) determined the syne rgistic effects of mixtures of lead tetraacetate, arsenic trioxide, dieldrin, and tetrach loroethylene on genotoxicity in the Tradescantia micronucleus assay. Lead tetraacetate (0.44 ppm) alone increased the frequency of micronucleus formation in plants exposed for 30 hours over that in the solvent controls.

Gill and Sandhu (1992) determined the genotoxic effects of arsenic trioxide, dieldrin, and
lead tetraacetate alone and in combination in the Tradescantia micronucleus assay. The chemicals or their mixtures were either (1) mixed into soil, and exposure to the target cells was through the roots of intact plants grown in the soil, or (2) prepared as an aqueous solution, and exposure was by absorp tion through the stems of plant cuttings.
Lead tetraacetate was tested at concentrations of 4 μg/mL in the aqueous test system and and 4 mg/kg in the soil test system. Soil-grow n plants exposed to le ad tetraacetate had significantly more ( P < 0.05) micronuclei than did th e controls (11.2 ± 2.3 vs. 5.1 ± 0.6 micronuclei per 100 tetrads, respectively). No difference was observed between the leadexposed and control plants grown in aque ous media (2.9 ± 0.5 vs. 2.3 ± 0.1 micronuclei per 100 tetrads, respectively). The clastogenic ity of lead tetraacet ate was altered by the
ratio of individual chemicals in the aqueous or soil media.

Lerda (1992) determined the effect of lead nitrate (at concentr ations of 0.1, 1.0, 10, 50, 100, or 200 ppm) on root growth, cell prolif eration, and chromoso mal aberrations in Allium cepa . The effect of lead nitrate on root growth was determined by measuring the length of 10 to 20 roots per onion bulb at 24-hour intervals for 96 hours. Lead nitrate at a concentration of 100 or 200 ppm complete ly inhibited root growth. At lower concentrations, the rate of growth was re duced in a dose-depende nt manner. Likewise, cell proliferation, which was determined at the root tip 12, 24, and 48 hours after exposure, was progressively reduced at high co ncentrations. However, this inhibition was transient; proliferation had recovered by 48 hours after exposure. No difference from controls was observed in cell proliferation at concentrations up to 10 ppm. At each exposure level, 5,000 cells were examined fo r chromosomal aberrations. The frequency
of chromosomal aberrations in cells from oni ons exposed to lead nitrate at 0.1 or 1.0 ppm did not differ from that of the non-expos ed controls. However, significantly ( P < 0.05)
more cells contained chromoso mal aberrations in plants e xposed at 10 ppm than in nonexposed controls (0.18 vs. 0 per 5,000 cells). The author stated that these results supported those of his previ ous studies demonstrating th at lead compounds induced chromosomal aberrations in persons occupa tionally exposed to lead (Lerda 1992).

Minissi et al . (1998) examined the genotoxicity of se diments from the Tiber River and its
tributaries in the urba n area of Rome, using a micronucleus assay in Vicia faba root tips. All samples were collected in July 1992. Sediments were assayed for content of the 13 most important chemicals of the polycycli c aromatic hydrocarbon (PAH) group and for some heavy-metal ions (cadmium, chromium, copper, nickel, lead, and zinc). The lead concentration in the sediments ranged from 12.4 to 43.5 ppm. The frequency of micronuclei was significantly ( P < 0.01) higher in plants ex posed to sediment collected
from 8 of the 10 sites than in the controls. These sites also contained significant amounts of PAHs and other metal ions (see Table 5-2).05/08/03 RoC Background Document for Lead and Lead Compounds127Table 5-2. Genotoxicity of lead compounds in plantsin vivoSpeciesEnd pointResultsCompoundConcentrationReferenceTradescantiaclone4430micronucleusformation+ lead tetraacetate0.44 to 11.75 ppm inwater; 4 μg/kg in soilSandhuet al.1989, Maet al.1992, Gill andSandhu 1992inhibition of rootgrowth+ lead nitrate0.1, 1, 10, 50, 100,200 ppmLerda 1992cell proliferation + lead nitrate0.1, 1, 10, 50, 100, 200ppmLerda 1992Allium cepachromosomalaberrations+ lead nitrate0.1, 1, 10, 50, 100, 200ppmLerda 1992Vicia fabamicronucleusformation+lead with othermetals12.4 to 43.1 ppm Minissiet al.199805/08/03 RoC Background Document for Lead and Lead Compounds

128 5.3 In vitro studies using cell-free systems
Roy and Rossman (1992) reported that exposur e of supercoiled plasmid DNA with lead acetate (1 mM) for 30 minutes at room temper ature in a Tris-HCl buffer (pH 7.5) did not induce nicks or strand breaks in the DNA, as determined by agarose gel electrophoretic analysis. Addition of hydrogen peroxide (H 2 O 2 , 0.3 mM) to the reaction mixture induced
the formation of nicks and double-stranded breaks in the DNA. The levels of DNA damage in the samples exposed simultaneously to H 2 O 2 and lead acetate were greater than those observed in DNA exposed to either lead acetate or H 2 O 2 . The investigators suggested that lead(II) did not damage DNA directly, but caused damage indirectly by participating in a Fenton reaction to gene rate hydroxyl radicals in the presence of H 2 O 2

.

Calsou et al. (1996) investigated the ability of several heavy metal ions, including lead(II), to inhibit nucleotide excision repair in vitro . These investigators determined the effect of these metal ions on lesion recogniti on and strand incision/d isplacement steps in
a whole-cell extract from HeLa cells. The in cision assay was performed with ultraviolet- (UV-) treated pBluescript phagemid vector DNA, as described by Calsou and Salles (1994). Lesion recognition (UV damage) was test ed in a mobility-shift assay, in which the protein-DNA complex was detected via electrophoresis. Lead chloride (0.1, 0.3, and 1.0 mM) inhibited incision repair activity in a dose-dependent manner, with approximately 50% of the activ ity inhibited at 1 mM. Likewi se, lead chloride (1 mM) inhibited recognition of UV DNA damage by th e cell extract. The investigators reported a good correlation between the inhibi tory effects of several me tal ions, including lead(II), on the excision activity of NER and a reduced protein-binding activity to damaged DNA.

Yang et al. (1999) reported that treatment of supe rcoiled plasmid DNA with lead acetate (0.3 mM) in HEPES buffer (10 mM, pH 6.8) at 37 o C for 3 to 24 hours resulted in timedependent DNA strand breakage. In studies with a 24-hour incubation period, the DNA strand breaks also were dose-dependent (over lead acetate concentrations of 0.1 to 0.3 mM), and DNA strand breakage also occurred in Tris-HCl buffer (1 to 10 mM, pH 6.8). To determine whether H 2 O 2 was involved in the react ion, DNA was treated with
0.1 mM lead acetate for 1 hour at 37 o C in the presence and absence of H 2 O 2 (1 or 5 mM). Under these conditions, ne ither lead acetate nor H 2 O 2 induced nicks or strand breaks in the plasmid, but treatment with lead acetate and H 2 O 2 in combination increased the incidence of DNA strand breaks. Although the inve stigators stated that the effect of H 2 O 2 was dose-dependent, no numerical data were reported to sup port this premise, and only
two concentrations of H 2 O 2 were employed. The singlet oxyg en scavengers sodium azide and 2,2,6,6-tetramethyl-4-piperidone (TEM P) inhibited lead-induced DNA strand breakage more efficiently than did the hydr oxyl radical scavenge rs, mannitol and 5,5- dimethyl-1-pyrroline-1-oxide. Deuterium oxi de, a singlet oxygen enhancer, increased lead-induced DNA strand breakage, while cata lase and superoxide dismutase did not protect the DNA from lead-induced breaks. Enhancement of lead-induced breaks by

H 2 O 2 was inhibited by sodium azide, TEMP, ed etate calcium disodium, catalase, and glutathione, and was potentiated by s uperoxide dismutase and mannitol.

To further examine the potential role of reactive oxygen species-intermediates on leadinduced DNA damage, studies were pe rformed to determine whether 8- hydroxydeoxyguanosine (8-OHdG) was formed in calf thymus DNA following its05/08/03 RoC Background Document for Lead and Lead Compounds

129 exposure for 1 hour at 37 ° C to lead acetate (0.1, 0.5, and 1 mM) in the presence and
absence of H 2 O 2 (5 mM). Under these conditions, neither lead acetate nor H 2 O 2 significantly increased the am ount of 8-OHdG in DNA over that in non-treated controls (average 6.6 ± 0.7 8-OHdG per 10 5 deoxyguanosine residues). However, treatment of the DNA with lead acetate (1 mM) and H 2 O 2 (5 mM) in combination resulted in a 14.4-fold increase in the amount of 8-OHdG (95.2 ± 10.8 8-OHdG per 10 5 deoxyguanosine residues). The investigators interpreted the data to suggest that lead(II) induced DNA damage through a Fenton-like reaction and that a singlet oxygen was the principal oxygen species involved in induci ng the damage (see Table 5-3).

5.4 Mammalian systems

5.4.1 In vitro assays

5.4.1.1 Lead acetate, lead chloride, lead nitrate, and lead sulfide

Frenkel and Middleton (1987) reported that lead acetate did not inhibit DNA and RNA synthesis in HeLa cells even after exposur e to 0.5 mM of lead acetate for 18 hours. Conversely, DNA and RNA synthesi s were inhibited in int act nuclei (50% inhibition concentration [IC 50 ] = 150 and 80 μM, respectively). Likewise, HeLa DNA polymerase α and RNA polymerase II activities we re inhibited by lead acetate (IC 50 = 150 and 20 μM, respectively). E. coli DNA polymerase I was more sensitive to inhibition by lead acetate (IC 50 = 10 μM) than was HeLa DNA polymerase α , but the sensitivity of the E. coli RNA polymerase was the same as that of the HeLa enzyme.

To investigate the genotoxicity of sol uble and insoluble l ead compounds, Zelikoff et al. (1988) used Chinese hamster ovary (CHO) cells (V79) as a model system to determine the mutagenic potential and th e ability of the compounds to induce sister chromatid exchange (SCE) and Syrian hamster embr yo (SHE) cells to determine their cell transformation potential. For the mutagenicity assays, V79 cells were treated with lead sulfide (insoluble) for 1 day or lead nitrate (s oluble) for 5 days, and their resistance to 6- thioguanosine was determined. For the SCE assay, exponentially growing V79 cells were treated for 24 hours. Bromodeoxyuridine (5 μg/mL) was added for two cell cycles, followed by colcemid treatment. Two hours later, mitotic cells were collected by mechanical agitation, fixed, and stained using a modification of the technique described by Schneider et al. (1978). A minimum of 30 mitotic cells was counted, and the number of SCE per chromosome was determined. The cy totoxicity of lead acetate, lead nitrate,
and lead sulfide to V79 cells was determined by clonogenic assay. The 50% lethal doses (LD 50 ) were 0.58, 2.55, and 2.95 mM for lead sulfid e, lead acetate, and lead nitrate, respectively. Treatment of V79 cells with lead nitrate or lead sulfide increased the frequency of mutation of the hprt gene compared to non-treate d controls. The increased mutation frequency was 6.2-fold higher in ce lls treated with 0.5 mM lead nitrate for 5 days. At higher concentrations, the mutati on frequency decreased but remained 2-fold greater than background. Lead sulfide (376 μM, 24-hour trea tment) induced a 5.5-fold increase in the mutation frequency. Neither lead nitrate nor lead sulfide induced a significant increase in the fr equency of SCE, nor did they induce DNA single-strand05/08/03 RoC Background Document for Lead and Lead Compounds130Table 5-3. Genotoxicity of lead compoundsin vitroin cell-free systems (without metabolic activation)Species or testsystemEnd pointResultsCompoundConcentrationReferencelead chloride 0.05–2 mMHoffman and Niyogi1977aE. coliRNApolymerase and avianmyeloblastosis DNApolymeraseinhibition of RNA orDNA biosynthesis++lead chloride 4 mM Sirover and Loeb 1976aDNA polymerase andRNA polymerase II inHeLa cell extractsDNA and RNApolymerase inhibition+ lead acetate 25–500 μMFrenkel and Middleton1987Whole-cell (HeLa)extractinhibition of DNAdamage incision activity+ lead chloride 0.1–1 mM Calsouet al.1996Supercoiled plasmidDNADNA strand breakswith H2O2without H2O2+–lead acetate 1 mM Roy and Rossman 1992Supercoiled plasmidDNADNA strand breakswith H2O2without H2O2without H2O2+–+lead acetate0.1 mM (1 h)0.1 mM (1 h)0.3 mM (3–24 h)Yanget al.1999aNot reviewed in the text; source: ATSDR 1999.05/08/03 RoC Background Document for Lead and Lead Compounds

131 breaks, as measured by alkaline elution. For the cell transformation assay, SHE cells isolated from embryos 12 to 24 days after ge station were treated with lead acetate for 24 hours, washed, and re-treated for an addi tional 24 hours. Fresh media was added, and plates were incubated for an additional 10 days or until colonies (> 50 cells) were observed. Lead acetate (10, 25, and 50 μM) indu ced cellular transfor mation of SHE cells in a dose-dependent manner. The investigators in terpreted these results to mean that lead compounds were genotoxic by an indirect mech anism and to support the view that lead might be a carcinogen.

To determine whether the genotoxi c effects of lead(II) were due to indirect effects rather than to direct DNA damage, Hartwig et al. (1990) used CHO (V79) and HeLa cells to
examine the effects of lead acetate on DNA repair processes as they relate to genotoxicity. Cytotoxicity was determin ed by clonogenic assay. Survival values following treatment of V79 cells withl ead acetate for 24 hours were 92.0%, 53.1%, 41.5%, 37.5%, and 32.1% at concen trations of 1, 3, 5, 10, a nd 25 μM, respectively. Lead acetate did not increase the frequency of hprt gene mutations in V79 cells, nor did exposure to lead(II) increase the frequenc y of SCE. Lead(II) al so did not induce DNA strand breaks in HeLa cells, as determined by nucleoid sedimentation. However, for all the end points tested, lead ions interfer ed with the processing of UV-induced DNA damage. Mutation frequency in UV-irradiated CHO cells was increased by treatment with lead acetate (at 0.5, 1, 3, and 5 μM) for 20 hour s prior to irradiati on. Pretreatment of CHO cells with lead acetate (1, 5, and 10 μM ) before UV irradiation also significantly increased ( P< 0.1) the frequency of SCE. The i nvestigators also concluded, based on nucleoid sedimentation assays with HeLa cells , that lead acetate inhibited repair of UVdamaged DNA.

Hartwig (1994, 1995) published two review s concerning the relationship between inhibition of DNA repair processes by metal i ons and their genotoxicity. In these reviews, she summarized previous studies concerning th e genotoxicity of a va riety of metal ions, including lead(II). With respect to lead(II), she concluded, based on research primarily with CHO (V79) cells, that the direct genotoxic ity of lead(II) was weak and restricted to toxic concentrations. Lead(II) induced DNA st rand breaks only at toxic levels (Roy and Rossman 1992), but not at lower concentr ations, and it did not induce DNA protein crosslinks as determined by alkaline elution (Zelikoff et al. 1988) or nucleoid sedimentation (Hartwig et al. 1990). Hartwig concluded that the mutagenic potential of soluble lead compounds was low (Roy and Rossm an 1992) and that lead acetate and lead sulfide did not significantly increase the frequency of SCEs in exposed V79 cells (Zelikoff et al. 1988, Hartwig et al. 1990). Hartwig also su mmarized data that she
believed demonstrated that lead co mpounds acted as co-mutagens (Hartwig et al. 1990, Roy and Rossman 1992), possibly by inhibiti ng nucleotide excisi on repair (Hartwig et al. 1990). However, as she pointed out, this explan ation was controversial even at that time,
because studies in HeLa cells demonstrated th at while lead chloride (250 μM) inhibited the recovery of DNA synthesi s after X irradiatio n, suggesting inhibition of DNA repair (Skreb and Habazin-Novak 1977), lead acetate had no effect on the resealing of X-rayinduced DNA strand breaks (Snyder et al. 1989). Hartwig sugges ted interference with DNA repair processes as a possible mechan ism for the genotoxicity of metal ions,05/08/03 RoC Background Document for Lead and Lead Compounds

132 including lead(II), because these genotoxi c effects were observed at low, nontoxic
concentrations.

Using a transgenic CHO cell line (G12) de rived from V79 cells, Roy and Rossman (1992) reported that exposure to lead acetat e (1.7 mM) for 5 days increased the frequency
of gpt recorder gene mutations approximately fivefold. Mutation frequency was not
increased at lower concentrations of l ead acetate (0.5 and 1 mM), nor at any
concentration of lead nitrat e (0.5, 1, 1.7 mM). However, pre-exposure of G12 cells for 24 hours to lead acetate at a nonmutagenic and slightly cytotoxic concentration (0.4 mM) increased the cytotoxicity and mutagenicity of N -methyl- N '-nitro- N -nitroguanidine and UVC light. The investigators concluded that lead(II) was weakly mutagenic and only at toxic doses (LD 50 = 1.7 mM for lead acetate and 1.5 mM fo r lead nitrate), but that lead(II) might act as a co-mutagen at non-lethal concentrations.

Lin et al. (1994) reported that lead nitrate (1, 5, 20, 30 μM) was not overtly cytotoxic to CHO cells (cell line not stated) (18.5% to 19.6% decrease in viability, based on trypan blue staining) following treatment for 16 hour s. However, low concentrations of lead nitrate (1 and 3 μM) significan tly increased the mito tic activity of exposed cells. Higher concentrations of lead nitrate (10 and 30 μM ) did not significantly increase the mitotic index of exposed cells (number of cells in division/total number of cells x 100). Genotoxicity was assessed with assays for micronucleus formation, chromosomal aberrations, and SCE frequency. None of the con centrations of lead nitrate tested induced micronuclei or significantly incr eased chromosomal aberrations. However, lead nitrate (3, 10, and 30 μM) did induce a significant incr ease (1.45- to 2.48-fold) in SCE. The investigators suggested that SCE may be the most sensitiv e end point for examining the genotoxicity of metal ions.

Yang et al. (1996) reported that e xposure of CHO cells ( hprt + cell line K1) to lead acetate (0.5 to 1.5 mM) for 24 hours increased the mutation frequency in a dose-dependent manner, ranging from a 3.36-fold increase at 0.5 mM to a 7.92-fold increase at 1.5 mM (the LD 50 ). Reverse-transcriptase-polymerase chain reaction (PCR) and genomic-DNA PCR analyses of cDNA and genomic DNA fr om mutants from the various exposure groups suggested that G:C base pairs might be the primary targ et sites for lead mutagenesis. Furthermore, molecu lar analyses indicated that G:C Æ C:G transversions predominated in low-mutation-frequency populations and G:C Æ A:T transitions in highmutation-frequency populations. The authors su ggested that lead might induce mutations by different mechanisms, possibly including interaction of the metal with DNA and subsequent reactive-oxygen-species- (ROS-) mediated damage and interference with DNA polymerase fidelity a nd DNA repair enzymes.

Using the CHO cell line AA8, Cai and Arenaz (1998) reported that lead nitrate was cytotoxic in a concentration-dependent manne r to cells exposed for 3 or 12 hours. Four
concentrations of lead nitrat e ( 0.5 to 1 μM) were tested, a nd cytotoxicity was determined with a clonogenic assay. Cells were exposed to lead nitrate (0.1, 0.5, 1 μM) for 24 or 36 hours, and chromatids were differentially stai ned as described by Perry and Wolff (1974). A significant increase in SCE fre quencies was observed at all lead nitrate concentrations tested, but there was no increase in the frequency of chromosomal aberrations.05/08/03 RoC Background Document for Lead and Lead Compounds

133 Hwua and Yang (1998) examined the effect of 3-aminotriazole, an inhibitor of catalase, peroxidase, and cytochrome P450 2E1, on anchorage independence and on the mutagenicity of cadmium acetate and lead ac etate in primary diploid human fibroblasts. Exponentially growing cells were treated with 80 mM 3-aminotriazole 1 hour before exposure to cadmium acetate and lead acetate for 24 hours. The concentrations of lead acetate used in these studies were 0.5, 1.5, and 2 mM. After removal of the metal ions, the cells were maintained in exponential gr owth for 7 or 9 days before mutation and anchorage-independence assays, respectively, we re performed. The cyto toxicity of lead acetate was determined by clonogenic assay. Th e concentration required to reduce the
survival of treated cells to 37% was 0.8 mM . Lead acetate exposure significantly induced anchorage-independent growth in a dose-de pendent manner. The numbers of anchorageindependent colonies induced per 10 6 viable cells were 182.6 ± 16.9 at 1.5 mM and 262.7 ± 37.8 at 2.0 mM. Exposure to lead acetat e did not increase the frequency of hprt gene mutations. Lead-induced anchorage independence and cytotoxicity were not affected by 3-aminotriazole cotreatment, but 3-aminotriazole did si gnificantly increase lead uptake and accumulation in human fibrobl asts. The investigators concluded that lead(II) might act as a tumor promoter, and that ROS were more important in cadmiumthan in lead-induced cytotoxic ity and anchorage independence.

In a series of studies using the transg enic CHO cell line AS52, Ariza and coworkers (Ariza and Williams 1996, 1999, Ariza et al. 1998) demonstrated th at low, relatively nonlethal concentrations (0.1 to 1.0 μM) of lead chloride were mutagenic. At these concentrations, lead chloride was minimally cytotoxic to cells e xposed for 1 hour (Ariza and Williams 1996). At the highest lead chloride concentration tested (1 μM), viability was reduced only by 28% in a clonogenic assay. Exposure of AS52 cells to lead chloride (at eight concentrations from 0.1 μM to 1 μM ) for 1 hour resulted in a dose-dependent increase in the frequency of gpt transgene mutations. The increase in mutation frequency ranged from 2.5-fold at 0.1 μM to 6.2-fold at 1 μM.

Multiplex PCR and Southern blot analyses were used to examine 138 lead-induced, 29 ROS-induced, and 20 spontaneously arising mu tants for point and deletion mutations in
the gpt gene (Ariza and Williams 1999). Lead(I I) induced significantly fewer point mutations (48%) than were observed in cel ls exposed to reactive oxygen intermediates (90%) or in spontaneous mutants (90%). Furt her examination of the data demonstrated that at lead chloride concentrations of 0.4 μM or lower, the majority of the mutations in
the gpt gene were point mutations, while at higher concentra tions, deletions (partial and complete) were predominant. These results ar e consistent with the hypothesis that soluble lead compounds induce mutations in eukaryotic cells by at least two distinct mechanisms (Yang et al. 1996, Ariza et al. 1998).

5.4.1.2 Lead chromate

Chromium metal salts, including lead chro mate, have been classified as human carcinogens based on epidemiological and e xperimental data (IA RC 1990). Several end points have been employed to assess the ge notoxic potential of l ead chromate, including
enhancement of simian adenovirus tr ansformation of SHE cells (Schechtman et al. 1986,
Elias et al. 1989), morphological transformati on of C3H/10T1/2 cells (Patierno et al. 1988, Patierno and Landolph 1989), morphol ogical transformation of human05/08/03 RoC Background Document for Lead and Lead Compounds

134 osteosarcoma cells (Sidhu et al. 1991), induction of mutation in CHO cells (Patierno and Landolph 1989), induction of DNA strand brea ks and DNA-protein cr osslinks in CHO cells (Xu et al. 1992), and clastogenic effects in CHO and human fibroblasts (Wise et al. 1992, 1993, Blankenship et al. 1997). However, these stud ies did not separate the genotoxic effects of lead from those of chromium; therefore, they are not considered in
this review.

Wise et al. (1994), using CHO (AA8) cells, performe d a series of studies designed to
elucidate the relative roles of lead and chromium in the clastogenic activity of lead
chromate. Cell-mediated extracellular disso lution of lead chromate resulted in
intracellular accumulation of both lead and chromium. Accumulation of chromium was time- and concentration-dependent, and wa s maximal following a 24-hour exposure to lead chromate at 8 μg/cm 2 . Accumulation of lead also wa s dose-dependent, but its timedependency was more variable. Under these conditions, the in tracellular concentration of chromium was 2.75 ± 0.3 mM, and the concentr ation of lead was 97 ± 58 μM. In similar studies with lead glutamate (500 μM), the ma ximum intracellular l ead ion concentration was 834 ± 63 μM. The clastogenic activity of lead chromate was 21% ± 7% at 0.8 μg/cm 2
and 66% ± 17% at 8 μg/cm 2 . These percentages were significantly greater ( P < 0.005) than in the vehicle control (3% ± 1%). Exposur e of cells to sodium chromate (2 or 4 μM) resulted in a significant increase ( P < 0.005) in chromosomal aberrations (12% ± 2% and 23% ± 8%). Lead nitrate (0.5 to 1 mM) did not induce chromosomal aberrations. Although lead glutamate at a concentration of 1 mM significantly increased the frequency of chromosomal aberrations (11%), this e ffect was not observed at lower (0.5 mM) or higher (2 mM) concentrations. Pretreatment of cells with vitamin E reduced sodium
chromate- and lead chromate -induced clastogenesis 54% to 93%, respectively, but the vitamin had no effect on lead glutamate-indu ced clastogenesis. The authors concluded that although lead ion was weakly clastogeni c, chromate ion was the major clastogen in lead chromate (see Table 5-4).05/08/03 RoC Background Document for Lead and Lead Compounds135Table 5-4. Genotoxicity of leadcompounds in mammalian systemsin vitroEnd pointTest systemResultsCompoundConcentrationReferenceChromosomalaberrationsCHO cells + lead acetate 0.001–10 mM Bauchinger and Schmid 1972aChromosomalaberrationsCHO cells + lead acetate 0.05–1 mM Robisonet al.1984aChromosomalaberrationsCHO cells + lead nitrate0.1, 0.5, 1μMCai and Arenaz 1998ChromosomalaberrationsCHO cells + lead nitrate 0.5, 1, 2 mM Wiseet al.1994ChromosomalaberrationsCHO cells – lead nitrate3–30μMLinet al.1994SCE CHO cells ––lead nitratelead sulfide500–3,000μM133–938μMZelikoffet al.1988SCE CHO cells – lead acetate 1–25 μM Hartwiget al.1990SCE CHO cells + lead nitrate1–30μMLinet al.1994SCE CHO cells + lead nitrate0.1–1μMCai and Arenaz 1998MicronucleiusformationCHO cells – lead nitrate3–30μMLinet al.1994MicronucleusformationSprague-Dawleyrat kidney cells+ lead acetate 0.56–1.8 mM Robbianoet al.1999MitoticdisturbanceCHO cells + lead acetate 0.001–10 mM Bauchinger and Schmid 1972aMitoticdisturbanceCHO cells + lead sulfate 10, 20, 40 μM Costaet al.1982aMitotic index CHO cells + lead nitrate3–30μMLinet al.199405/08/03 RoC Background Document for Lead and Lead Compounds136End pointTest systemResultsCompoundConcentrationReferenceMutation inhprtgeneCHO cells + lead nitratelead sulfide50–2,000μM100–938μMZelikoffet al.1988Mutation inhprtgeneCHO cells + lead acetate 0.5–2.0 mM Yanget al.1996Mutation inhprtgeneCHO cells – lead acetate 1 to 25 μM Hartwiget al.1990Mutation inhprtgeneprimary diploidhumanfibroblasts– lead acetate 0.5 to 2 mM Hwua and Yang 1998Mutation ingptgenetransgenic CHOcells+ lead chloride 0.1–1 μMAriza and Williams 1996, 1999, Arizaetal.1998Mutation ingptgenetransgenic CHOcells+–lead acetatelead nitrate500–1,700μM500–1,700μMRoy and Rossman 1992CelltransformationSHE cells + lead acetate10, 25, 50 μM Zelikoffet al.1988DNA strandbreaksCHO cells ––lead nitratelead sulfide500–3,000μM133–938μMZelikoffet al.1988DNA strandbreaksHeLa cells – lead acetate 100–2,000 μM Hartwiget al.1990DNA repair CHO cells + leadacetate 0.05–1 mM Robisonet al.1984aDNAfragmentationSprague-Dawleyrat kidney cells+ lead acetate 0.56–1.8 mM Robbianoet al.1999DNA damagetransgenic CHOcells+ lead chloride 0.1–1 μM Arizaet al.1998Inhibition ofDNA and RNAsynthesisHeLa cells – lead acetate500μMFrenkel and Middleton 198705/08/03 RoC Background Document for Lead and Lead Compounds137End pointTest systemResultsCompoundConcentrationReferenceInhibition ofDNA and RNAsynthesisintact nuclei ofHeLa cells+ lead acetate80μM (RNA) and150μM (DNA)Frenkel and Middleton 1987Inhibition ofDNA and RNApolymeraseHeLa cells andE.coli+ lead acetate10–150μMFrenkel and Middleton 1987Studies of lead as a co-factor or co-mutagenMutation inhprtgene, SCE, andnucleoidsedimentationCHO cells +increasedgenotoxicitybUV irradiationpre-exposureto lead acetate1–10 μMHartwiget al.1990Mutation ingptgenetransgenic CHOcells+increasedmutagenicitycN-methylN'-nitroNnitroguanidineor UVCpre-exposureto lead acetate0.4 mMRobisonet al.1984aNot reviewed in text; source: ATSDR 1999.bThe authors proposed that the genotoxic effects of pretreatment with lead acetateresulted from inhibition of DNA repair.cThe authors proposed an increase in DNA nicks due to inhibition ofDNA ligase as a possible mechanism for the effects of lead acetate05/08/03 RoC Background Document for Lead and Lead Compounds

138 5.4.2 In vivo assays

5.4.2.1 Reproductive genotoxicity studies

Nayak et al . (1989) determined the embryotoxicity a nd genotoxicity of lead nitrate using pregnant randomly bred ICR Swiss Webste r mice (6 to 8 weeks old). Lead nitrate dissolved in normal saline was given intr avenously (i.v.) at doses of 100, 150, or 200 mg/kg body weight on the ninth day of gesta tion. Fetuses were removed on the 18th day of gestation and used for cytogenetic and ch emical studies. For cytogenetic studies, bone marrow cells were obtained from the femurs of three dams from each exposure group, and liver or lung tissues from three fetuses per dam. The cytogenetic studies included an analysis of numerical and gross cytogenetic changes in G-banded chromosomes, frequency of SCE, frequency of nucleolar organizing regions (NORs), and analysis of changes in G-banded karyotypes. The lead le vels in maternal mice ranged from 0.04 ppm in non-exposed controls to 19.18 ppm in anim als given 200 mg/kg of lead nitrate. The
lead content in fetal tissue also increased (to a maximum 0.17 ppm in fetuses from dams given lead nitrate, compared with 0.07 ppm in fetuses from non-exposed controls). The percentage of resorptions was significantly higher ( P < 0.05) in the lead-exposed animals than in non-exposed controls. The frequenc y of SCE also was significantly higher ( P < 0.05) in dams given lead nitrate at eith er 150 mg/kg (4.87 ± 0.16 SCEs/cell) or 200 mg/kg (5.51 ± 0.17 SCEs/cell) than in th e controls (3.40 ± 0.15 SCEs/cell). No significant difference was observed in the fr equencies of SCE or NORs between fetuses from exposed animals and those from cont rols. The frequency of NORs per cell was significantly reduced ( P < 0.05) at the two highest l ead nitrate dose levels; the frequencies were 2.50 ± 0.39 at 150 mg/kg, 2.31 ± 0.23 at 200 mg/kg, and 4.1 ± 0.38 for controls. Aneuploidy was frequen tly associated with the lowest dose level of lead nitrate (100 mg/kg). Deletions also occurred freque ntly and involved several chromosomes.

Kristensen et al. (1993) performed domin ant-lethal studies of lead chloride and cyclophosphamide to quantify the genotoxic effects of lead chloride in late spermatogenesis. Male mice ( Mus musculus strain NMRI) were randomly assigned to four treatment groups (6 per group), and two groups received drinking water containing 1.33 g/L of lead chloride for six weeks. One week (seven days) before mating, one leadexposed group received an i.p. injection of cyclophospha mide (120 mg). Blood lead concentrations (μmol/L [ μ g/dL]) at time of mating were as follows: control group, 0.03 ± 0.02 [0.6 ± 0.4]; lead group, 1.24 ± 0.24 [34.3 ± 5.0]; cyclophosphamide group, 0.01 ± 0.02 [0.2 ± 0.4]; and lead plus cyclophos phamide group, 1.15 ± 0.14 [23.8 ± 2.9]. After mating, female mice were examined for the number of implants, number of live implants, number of resorptions, number of late implant losses, and mortality. Although the frequency of resorptions was lower in fema les mated with lead-treated males, the difference was not statistically significant. The data suggest that inorganic lead does not influence the mutagenicity of cyclophos phamide in the dominant-lethal assay.

Foster et al. (1996) investigated the e ffect of chronic lead exposure on semen quality in healthy cynomolgus monkeys ( Macaca fascicularis ) aged 15 to 20 years with mean (± SD) blood lead levels of 10 ± 3 μg/dL (range = 6 to 20 μg/dL, N = 4) and 56 ± 49 μg/dL (range = 22 to 148 μg/dL, N = 7) compared w ith a reference group w ith blood lead levels < 1.0 μg/dL (N = 8). Monkeys had been exposed to lead acetate (50, 100, 500, or 2,00005/08/03 RoC Background Document for Lead and Lead Compounds

139 μg/kg body weight) since birth. Blood and seme n samples were collected once from each monkey in five different m onths. Serum testosterone levels were determined by radioimmunoassay, and lead effects on chro matin structure were analyzed by flow cytometry. No effects of treatment were observe d on circulating levels of testosterone or parameters of semen quality such as sper m count, viability, mo tility, or morphology. A single sperm sample from each monkey was analyzed for effects on chromatin structure (Evenson 1990). In the flow-cytometric-base d assay, sperm with abnormal chromatin structure are defined as having an increased susceptibility to acid denaturation, resulting in a shift from green to red fluorescence, expressed as α t and determined by the ratio of
red fluorescence to total fluorescence. Sperm from lead-exposed monkeys had significantly different ( P < 0.03) α t values than that from the controls. Sperm quality also differed significantly ( P < 0.05) among the lead-exposed groups. The authors concluded that chronic lead exposure alte red sperm chromatin structure.

5.4.2.2 Genotoxicity studies in mammals

Dhir et al. (1993) determined the effects of Phyllanthus emblica fruit extract (PFE) and ascorbic acid on the ability of lead to induce SCE in the bone marrow of Swiss albino male mice ( Mus musculus ). The mice were 6 to 8 weeks old, weighed 25 to 30 g, and were divided into exposure groups of five an imals each. Mice were treated with a single priming dose of PFE by oral gavage (685 mg /kg b.w.) or with ascorbate (16.6 mg/kg b.w.) for seven consecutive days before exposure to lead nitrate. Bromodeoxyuridine (BrdU) was implanted subcutaneously in the abdomen as described by Sharief et al. (1986). Immediately after, mice were injected i.p. with lead nitrate in saline at concentrations of 10, 20, or 40 mg/kg b.w. Mice were injected i.p. with colchicine 22 hours after BrdU implantation a nd sacrificed by cervi cal dislocation 2 hours later. Bone marrow cells were obtained from femurs, a nd differential staining was performed as described by Perry and Wolff (1974) and Giri et al. (1987). Sixty intact second-division metaphase cells per animal were scored for SCEs, for a total of 300 cells per exposure

group. In vivo exposure to lead nitrate re sulted in a significant ( P < 0.001) dosedependent increase in SCE frequency over th at in the control group. The increase was 2.5-, 3.7-, and 4.2-fold for mice exposed to lead nitrate at 10, 20, and 40 mg/kg, respectively. No difference was noted in the proliferation index. Pretreatment with PFE or ascorbate significantly ( P < 0.001) reduced the increase in SCE, compared with that observed in animals exposed to lead nitrate alone.

To determine the clastogenic effect of lead nitrate, Jagetia and Aruna (1998) employed the micronucleus assay. Swiss albino mice (either sex) were injected i .p. with lead nitrate at 0, 0.625, 1.25, 2.5, 5, 10, 20, 40, or 80 mg/kg b.w., and animals were sacrificed at 12, 24, or 36 hours post-treatment. Bone marrow cells from femurs were prepared as described by Jagetia and Jacob (1992). The frequencies of micronucleated polychromatic erythrocytes (MPCE) and mi cronucleated normochromatic erythrocytes (MNCE) at 12, 24, and 36 hours after treatment were signifi cantly higher in exposed mice than in
controls. The increase in frequency of micronuclei was not dose-related and was greater
in male than in female mice. Lead ni trate exposure also resulted in increased erythropoiesis, as the ratios of polychromatic to normochromatic erythrocytes (P/N ratio) were significantly higher in lead-exposed mice than in controls at 12, 24, and 36 hours05/08/03 RoC Background Document for Lead and Lead Compounds

140 post-exposure. The P/N ratio was significantly higher in females than in males at 12 and 24 hours post-exposure.

Robbiano et al. (1999) examined five chemicals, incl uding lead acetate, that are known to induce tumors in rats; these chemicals i nduce DNA damage and micronuclei formation in primary cultures of rat and human kidney cells and in the kidneys of intact rats (SpragueDawley male albino rats). DNA damage was tested with the co met (single-cell gel electrophoresis) and micronucleus assays. Prim ary cells were exposed to lead acetate (0.56, 1, or 1.8 mM) for 20 hours and immediatel y used for the comet assay or were
cultured for a total of 48 hours for the micronuc leus assay. Cytotoxicity was determined following 20 hours of exposure to the compoun d, and relative survival was based on trypan blue exclusion. The relative survival of primary rat and human kidney cells ranged from 84% to 96%. Data from the comet assay, based on cells pooled from three different
rats and cells from three different human donor s, demonstrated that lead acetate induced a dose-dependent increase in both tail length and tail moment, indicating DNA fragmentation. DNA fragment ation was significantly ( P < 0.05) greater than in vehicle
controls. Similar results were obtained with the micronucleus assay. Lead acetate induced
a 3.7- to 6.4-fold increase in micronucleated primary rat cells a nd a 3.6- to 7.1-fold increase in micronucleated primary human kidne y cells; these increases were statistically significant ( P < 0.05). Consistent with the results observed in vitro , statistically significant increases in the average fre quency of both DNA breaks and micronucleated cells were detected in the kidneys of ra ts given a single dose of lead acetate (0.5 LD 50 ) or three successive daily doses (0.33 LD 50 ). DNA fragmentation, based on the Comet assay,
increased 5.3-fold at a le ad acetate concentration of 107 mg/kg (three successive daily doses). The frequency of micronucleated ce lls increased 3.2-fold in animals given a single dose of lead acetate (160 mg/kg b.w.) and 3.8-fold in animals given three successive daily doses of 107 mg/kg b.w.

To determine whether lead enhanced the genot oxic effect of the pyrethroid cypermethrin [( RS )- α -cyano-3-phenoxybenzyl(1 RS )- cis,trans -3-(2,2-dichlorovinyl)-2,2- dimethylcyclopropanecarboxylat e], an insectide, Nehez et al . (2000) administered cypermethrin to outbred male Wistar rats (30 days old) by gavage for 4 weeks, five times per week, at 5.54, 11.08, or 22.16 mg/ kg b.w. (1/100, 1/50, or 1/25 LD 50 ) alone or in combination with 10 mg/kg lead acetate at the 1/100 and 1/50 LD 50 dose levels. Following treatment, animals were sacrifice d, and bone marrow cells were obtained from the femur. Twenty metaphases from 10 animals per group were evaluated for the number of aberrant cells, numerical aberrations (chromosome nu mber under or over 42), and structural aberrations (gaps, iso gaps, break s, iso breaks, chromatid exchange, acentric fragments, dicentric and ring chromosomes, deletions, and translocations). Exposure to lead acetate significantly incr eased the frequencies of abe rrant cells (18% vs. 5.5% for vehicle control; P < 0.01) and numerical chromosomal aberrations (16% vs. 6% for vehicle control; P < 0.05) but did not affect the fre quency of structural chromosomal aberrations (1% in control and exposed groups ). The combination of cypermethrin and lead acetate significantly in creased the frequency of ab errant cells (21.5% at a cypermethrin concentration of 5.54 mg/kg; P < 0.01; 25% at a cypermethrin concentration of 11.08 mg/kg; P < 0.001) over that in vehicl e-treated cells (10%). The frequency of numerical aberra tions was not significantly increased by cypermethrin and05/08/03 RoC Background Document for Lead and Lead Compounds

141 lead acetate in combination. However, th e frequency of structural chromosomal aberrations was significantly increased (7.0% at a cypermet hrin concentration of 5.54 mg/kg; P <0.05; 11.5% at a cypermethrin concentration of 11.08 mg/kg; P < 0.001). The
authors concluded that the co-administration of lead increased the genotoxic effect of cypermethrin (see Table 5-5).

Table 5-5. Genotoxicity of lead compounds to mammals in vivo

End point Results Species Compound Concentration a Reference

Reproductive genotoxicity studies

SCE

fetuses

dams –

+ ICR Swiss Webster mice: pregnant mice exposed and genotoxicity
measured in
maternal bone
marrow and fetal liver and/or lung
cells lead nitrate

100, 150, 200

mg/kg b.w.

150, 200 mg/kg
b.w. Nayak et al.
1989

NORs

fetuses

dams –

+ ICR Swiss Webster mice: pregnant mice exposed and genotoxicity
measured in
maternal bone
marrow and fetal liver and/or lung
cells lead nitrate

100, 150, 200

mg/kg b.w.

150, 200 mg/kg
b.w. Nayak et al.
1989

Chromosomal

aberrations

fetuses

dams +

+ ICR Swiss Webster mice: pregnant mice were exposed and genotoxicity
was measured in
maternal bone
marrow and fetal liver and/or lung
cells lead nitrate

100 mg/kg b.w.

100, 150, 200 mg/kg b.w. Nayak et al.
1989

Fetal resorptions in unexposed females
mated with leadexposed males – male NMRI mice exposed before breeding lead chloride 1.33 g/L in water Kristensen et al. 1993

Sperm morphology – male White New
Zealand rabbits lead acetate 0.25, 0.5 mg/kg
b.w. Willems et al.
1982 b

Abnormal chromatin structure in sperm + Cynomolgus monkey sperm
cells lead acetate 50, 100, 500, 2,000 μg/kg b.w. Foster et al.
199605/08/03 RoC Background Document for Lead and Lead Compounds

142 End point Results Species Compound Concentration a Reference

Animal genotoxicity studies

DNA fragmentation +

(both doses) male albino Sprague-Dawley rat kidney cells lead acetate 117 mg/kg (1 dose)

78 mg/kg (3 doses) Robbiano et al. 1999

Chromosome loss or nondisjunction – Drosophila melanogaster lead nitrate 200 ppm in corn meal-agar substrate Ramel and Magnusson
1979 b

Structural
chromosomal
aberrations or chromatid gaps + aberrations

– gaps C57B1 mouse bone

marrow lead acetate 0.5% in food Deknudt and
Gerber 1979 b

Structural
chromosomal
aberrations or chromatid gaps – aberrations

+ gaps A/sw mouse leukocytes lead acetate 1% in food Muro and Goyer 1969 b

Structural
chromosomal
aberrations or chromatid gaps – aberrations

+ gaps female C57B1
mouse bone

marrow lead acetate 0.50%, 1% in food Jacquet et al.
1977 b

Structural
chromosomal aberrations or gaps + Sprague-Dawley
rat bone marrow lead acetate 10.4, 51.8, 77.6, 103.5 mg/kg b.w. Tachi et al.
1985 b

Chromosomal
aberrations + male Wistar rats
bone marrow lead acetate 10 mg/kg b.w. Nehez et al.

2000

Structural
chromosomal aberrations or gaps + Cynomolgus monkey lymphocytes lead acetate 1.5, 6, 15 mg/day
in water Deknudt et al.
1977 b

Structural
chromosomal aberrations or gaps + Cynomolgus monkey lymphocytes lead acetate 1, 5 mg/day Jacquet and
Tachon 1981 b

Micronucleus
formation + Sprague-Dawley
rat bone marrow lead acetate 10.4, 51.8, 77.6, 103.5 mg/kg b.w. Tachi et al.
1985 b

Micronucleus
formation +
(both doses) male albino Sprague-Dawley rat kidney cells lead acetate 117 mg/kg (1 dose)

78 mg/kg (3 doses) Robbiano et al. 1999

Micronucleus
formation + Swiss albino
mouse bone

marrow lead nitrate 0.625, 1.25, 2.5, 5, 10, 20, 40, 80 mg/kg b.w. Jagetia and
Aruna 1998

Micronucleus
formation – C57BL/6 x
C3H/He F 1 mice lead acetate 125, 250, 500, 1,000 mg/kg b.w. Bruce and
Heddle 1979 b

Micronucleus
formation – male rabbit bone

marrow erythrocytes lead acetate 0.25, 0.5 mg/kg
b.w. Willems et al.
1982 b

SCE – male rabbit peripheral blood lymphocytes lead acetate 0.25, 0.5 mg/kg
b.w. Willems et al.
1982 b05/08/03 RoC Background Document for Lead and Lead Compounds

143 End point Results Species Compound Concentration a Reference

SCE + male Swiss albino
mouse bone

marrow lead nitrate 10, 20, 40 mg/kg
b.w. Dhir et al.
1993

Cellular proliferation – male Swiss albino
mouse bone

marrow lead nitrate 10, 20, 40 mg/kg
b.w. Dhir et al.
1993

a The concentration reported is the dose level at which treatment-related effects were observed.

b Not reviewed in text; source: ATSDR 1999.

5.4.2.3 Human genotoxicity studies

Summary of ATSDR review ATSDR (1999) reviewed genotoxicity st udies of humans exposed to lead in vivo (mainly from occupational studies) published th rough 1994 and concluded that although the
results were somewhat contradi ctory, they did suggest that lead might have an effect on chromosomes. Occupational exposure to lead was associated with increased mitotic activity or effects on cell divisi on. Most, but not all, studies reported higher frequency of chromosomal aberrations in workers exposed to lead, and mixed results were reported for SCE. ATSDR noted that a common problem in these occupational studies was the possibility of confounding by occupational co -exposures. These studies and others published since 1994 (discussed below), are summarized in Table 5-6.

Current studies Rajah and Ahuja (1995) examined the in vivo genotoxic effects of smoking and occupational lead exposure in printing pre ss workers. The study population contained 29 males, including 13 printing-press worker s and 16 individuals from the general population. Previous studies had indicated that atmospheric l ead levels from the printing press were three times as high as background levels. A questionnaire was used to obtain data on age; duration of lead exposure; smoki ng; alcohol, coffee, and drug consumption; and recent illnesses. The subjects were divided into four groups: nonsmoking controls (N = 9), smoking controls (N = 7), lead-exposed nonsmokers (N = 7), and lead-exposed smokers (N = 6). Mitotic index and SCE were determined in peripheral blood lymphocytes. Lead-exposed smokers had the lo west mitotic index (0.78), compared with smoking controls (1.24) and lead-exposed nonsmokers (1.26); how ever, significance testing was not reported for the difference between lead-exposed smokers and smoking controls. The lead-expos ed nonsmokers also had a significantly ( P < 0.05) lower mitotic index than did nonsmoking controls. Smokers in the control and lead-exposed groups had significantly ( P < 0.05) higher frequencies of SCE than did the nonsmoking controls (5.66 ± 1.52/cell for smoking controls, 5.37 ± 2.53/cell for lead-exposed smokers, and 3.22 ± 0.47/cell for nonsmoking controls). The frequency of SCE in the lead-exposed nonsmokers (3.75 ± 0.58/cells) did not differ si gnificantly from that in the non-smoking controls (3.22 ± 0.47/cell). The authors conc luded that the combination of smoking and lead exposure increased the frequency of SC E and inhibited mitosi s, but that lead exposure did not appear to increase genot oxic damage beyond that caused by smoking alone. [The ability to separate the effects of lead from those of smoking or to evaluate any possible interactions between lead and smoking was limited by small numbers in05/08/03 RoC Background Document for Lead and Lead Compounds

144 each exposure category (N = 6 or 7) and by the lack of quant itative information on smoking and lead exposure. Individuals smoking 10 or more cigarettes per day for more than a year were considered smokers; thus, the “smoker” groups included both light and heavy smokers, and it is not known whethe r the degree of smoking was similar between the lead-exposed smokers a nd the smoking controls.]

Vaglenov et al. (1997) correlated micronucleus formation in lead smelter workers with
lead air concentrations at the work s ite, blood lead levels, employment period, and smoking habits. A total of 73 male workers were grouped by occupation: millers (N = 23), assembly workers (N = 21), plate-stacki ng workers (N = 20), and formation workers (N = 9). Controls were 23 males from admini stration and maintenance staff of the same plant who were never in direct occupational contact with lead. Th e total exposed group
and controls also were s ubdivided into smokers and nonsmokers. The frequency of micronucleated cells per 1,000 binucleated ly mphocytes was measured in peripheral blood lymphocytes. The mean concentration of l ead in the air at the work sites was 0.7 ± 0.5 mg/m 3 for mill workers, 0.38 ± 0.3 mg/m 3 for assembly workers, 0.23 ± 0.2 mg/m 3
for plate-stacking workers, and 0.19 ± 0.1 mg/m 3 for formation workers. The mean air
lead concentration for controls at the same factory was 0.06 ± 0.02 mg/m 3

.

Mean blood lead concentrations for 65 of th e 73 workers were over the “dangerous” level

of 1.92 μ mol/L [40 μ g/dL], which is associated with biological effects. Elevated micronucleus frequencies were observed in lead-exposed workers from the four groups, and micronucleus frequency was correlated with external exposure (air lead concentrations) and internal exposure (blood lead levels). The micronucleus frequencies per 1,000 binucleated cells for the groups were 51.1 for mill workers, 46.5 for assembly workers, 37.3 for plate-stacking workers, and 35.2 for formation workers, for an average of 44.0 for the lead-exposed group, compar ed with 20.1 for the control group. The number of cells containing mi cronuclei also was significantly higher in the lead-exposed group than in the control group. For the whole group, analysis of variance showed that lead exposure, but not age and smoking, was correlated with micronucleus formation. The genotoxic effect was linearly dependent ( P < 0.001) on the inte rnal exposure, supporting an association between lead exposure and micronucleus formation. Micronucleus frequency did not differ significantly ( P > 0.05) between lead-exposed smokers and nonsmokers, but did differ signif icantly between the control-group smokers and nonsmokers. [Strengths of this study include quantitative assessment of lead exposure (both external and in ternal); larger numbers of smoking (44) and nonsmoking (29) lead-exposed workers; ev aluation of effects of different variables, such as smoking, age, and lead exposure; greater power to dete ct an effect, due to the high lead-exposure levels; and the finding of an exposure-res ponse relationship. Limitations included the
small number of controls and small s ubsets of smoking (10) and nonsmoking (13) controls and the lack of reported quan titative information on smoking habits.]

Bilban (1998) analyzed th e incidence of cytogenetic damage in peripheral blood leukocytes of miners working in a lead and zinc mine in Slovenia (N = 120 males; 52% smokers), housewives living in the immediate vi cinity of the mine, but not occupationally exposed (control group 1: N = 57 females; 17% smokers), and an independent control group (control group 2: N = 100; 86 males, 14 females; 58% smokers). Workers were05/08/03 RoC Background Document for Lead and Lead Compounds

145 exposed to metals, including lead, cadm ium and zinc, and radon. The blood lead concentration in the lead-exposed miners averaged 28 μ g/dL, but 16% of these miners had blood lead concentrations greater than 40 μ g/dL (the permissible value recommended by the World Health Organization in 1980). Th e blood lead concentration in the control groups averaged 7.2 μ g/dL. Peripheral blood leukocytes were examined for structural chromosomal aberrations, SCE, and micronucleus formation.

The frequencies of chromosomal aberrations , SCE, and micronuclei were significantly higher in the miners than in the control groups. The mean percentages of cells with chromosomal aberrations were 4.09% (21,600 cells examined) in miners, 1.43% (11,400 cells) in control group 1, and 1.88% ( 20,000 cells) in control group 2. The mean frequencies of SCE were 7.97 per cell (5,800 cells examined) in miners, 6.17 (2,850 cells) in control group 1, and 6.63 (3,050 cells ) in control groups 2. The frequency of micronucleated cells was 13.00 ± 3.55 per 500 cy tokinesis cells (60,000 cells examined) for miners and 6.40 ± 2.12 (29,000 cells) in co ntrol group 2. Blood lead concentration and years worked in the mine were significantly correlated ( P = 0.012). SCE frequency was significantly dependent on blood lead concentration ( P = 0.001), as well as smoking. Chromosomal aberrations, but not SCE, were significantly dependent on radiation dose (radon). Moreover, smoking and the freque ncy of micronucleated cells were significantly correlated ( P = 0.001). The purpose of this stud y was to detect cytogenetic damage in the miners; the authors cautione d that it was not possi ble to separate the
individual effects of the di fferent occupational exposures, as well as any effects from smoking. [The strongest eviden ce of lead-induced cytogenetic damage probably was for SCE, because SCE frequency depended on blood lead levels and not on radon dose. Strengths of this study include larger numbers of exposed workers, measurements of blood lead levels and other occupati onal exposures, and smoking information.
Limitations include the lack of a relevant control group (that is, workers not exposed to lead) and the lack of analys is to control for confounders (occupational or lifestyle).]

Donmez et al. (1998) examined SCE frequencies in 32 male workers in a lead and zinc powder-producing factory in Turkey. The cont rols were 20 male sugar-refinery workers matched for age, smoking habits, and alcohol consumption. Metal-exposed workers had statistically significant higher blood lead levels than the controls ( P < 0.0001), but the
differences in blood zinc levels be tween groups were not significant ( P > 0.05). Peripheral blood lymphocytes were evaluated for SCE; for each subject, the frequency of SCE was determined in 30 metaphases. The fr equency of SCE was significantly higher in lead- and zinc-exposed subjects ( P < 0.01) than in the controls (mean SCE per cell = 8.55 in exposed subjects vs. 7.55 in controls), and was signi ficantly higher in nonsmoking lead- and zinc-exposed subjects than in nonsmoking controls ( P < 0.01). SCE frequency also was significantly higher ( P < 0.01) in control smokers than in control non-smokers (8.74 vs. 7.16). [Strengths of this study in cluded matching of controls by age, smoking, and alcohol consumption, which minimized possible confounding by these variables. Although the study population was small, si gnificant differences were observed; however, the further stratifica tion of the small number of workers and controls into
smokers and non-smokers could result in spurious associations.]05/08/03 RoC Background Document for Lead and Lead Compounds

146 Vaglenov et al. (1998) monitored the genotoxic effects of lead in 22 male workers from a starter-battery plant in Bulgaria who we re heavily exposed to lead (0.45 ± 0.5 mg/m 3 lead in air at the workplace, which exceede d the threshold limit value of 0.1 mg/m 3 ). Two control groups were included: an internal control group of 19 male workers from the same plant without direct lead exposure (control group 1) an d an external control group
of 19 male workers from the administrative staff of another factory in the same town (control group 2). A questionnaire was used to obtain data on smoking and alcohol consumption habits. Blood lead levels were 0.88 ± 0.03 μmol/L [18.23 ± 0.62 μ g/dL] for control group 2, 1.33 ± 0.08 μmol/L [27.56 ± 1.66 μ g/dL] for control group 1, and 2.94 ± 2.15 μmol/L [60.92 ± 44.55 μ g/dL] for the lead-exposed workers.

The frequency of micronucleated cell s per 1,000 binucleated lymphocytes was determined from peripheral blood lymphocytes . The lead-exposed workers had a higher frequency of micronucleated ce lls (61.95 ± 3.31) and larger nu mbers of binucleated cells containing one or more micronuclei (53.09 ± 2.36) than did the internal controls (26.47 ±
2.71 micronuclei and 23.74 ± 2.34 binucleated cells containing micronuclei) or the external controls (19.68 ± 2.14 micronuclei and 18.84 ± 2.09 binucleated cells containing micronuclei). [Strengths of this study were good exposure assessment of lead (both air
concentrations and blood levels were m easured) and the lack of any apparent occupational exposure to other genotoxic agen ts. Limitations included the small number of subjects and the lack of exposure-response analyses; how ever, the numbers may have been too small for the latter.] Although the authors assessed and reported smoking (cigarettes per day) for each individual, they did not appear to us e this information in their analyses. The lead-exposed group incl uded a higher percentage of smokers (77%) than did either control group 1 (58%) or cont rol group 2 (63%), but the average cigarettes per day in the lead-exposed gr oup (13.2) was intermediate be tween the averages for the two control groups (11.1 fo r control group 1 and 15.7 for control group 2). [Percent smokers and average cigarettes per day were calculated from data reported in the publication. Because micronucleus formation was two- to three-fold higher in the leadexposed workers than in the control groups , and the difference in smoking between the exposed and control groups di d not appear to be substant ial, it seems unlikely that smoking confounded these results.]

To explore the possible relationship be tween lead exposure and DNA damage and
oxidative stress in Chinese seconda ry lead smelter workers, Ye et al. (1999) correlated DNA damage as measured by the comet assay w ith concentrations of blood lead, urinary lead, and urinary α -aminolevulinic acid. Malondialde hyde (MDA) concentrations and superoxide dismutase (SOD) activity in plas ma also were determined. Information was obtained by questionnaire concer ning gender, age, duration of work, job type, cigarette smoking, and alcohol consumption. Heparinized blood and urine were obtained from 66 secondary lead smelter workers (41 male a nd 25 female) (46 used for the comet assay) and 28 controls (18 male and 10 female). Subj ects were divided into four groups based on blood lead concentrations (< 13, 13 to 27, 27 to 37, and > 37 μ g/dL). SOD activity and MDA concentrations were signif icantly higher in females in the three highest blood lead groups than in the lowest blood lead group, and SOD activity was higher in males with the highest blood lead levels; smoking and alcohol consumption did not significantly05/08/03 RoC Background Document for Lead and Lead Compounds

147 affect MDA concentrations or SOD activity. A positive correlation was observed between the blood lead concentration and DNA damage , which was statistically significant ( P < 0.05) for blood lead concentrations greater than 27 μ g/dL. Amounts of DNA damage differed significantly between lead-exposed work ers with the same smoking levels or alcohol consumpti on but different lead levels, except for nonsmokers and the low-lead-exposure group. DNA damage also in creased with increasing smoking levels at the same blood lead levels. [Strengths of this study were the finding of an exposureresponse relationship between lead exposure and DNA damage and attempts to separate genotoxic effects of lead e xposure from those of cigarett e smoking. Another strength was
measurement of MDA concentrations and S OD activity, which are markers of oxidative stress; elevated levels were consistent w ith potential mechanisms of lead-induced DNA damage. A potential limitation of the study wa s the stratification of a small number of subjects on many different variables (i.e., gender, smoking status, and lead exposure), resulting in very small numbers in each subgroup, which can yield spurious results.]

Restrepo et al. (2000) investigated the relations hip between lead exposure and DNA damage and repair in 43 Colombian battery -factory workers and 13 controls who were not occupationally exposed to lead. Indivi duals completed a questionnaire on smoking habits, age, and medical and occupational hi stories. Workers were highly exposed to lead; 74% of the exposed worker s exhibited clinical symptoms of lead toxicity, including headache, abdominal colic, me tallic taste, and paresthe sia. The average blood lead

concentration of the lead -exposed workers (98.5 ± 25.3 μ g/dL) was much higher than that of the non-exposed group (5.4 ± 3.6 μ g/dL). Lead-exposed workers and controls were subdivided into four groups according to cla ssification of their blood lead concentrations by Colombia’s National Institute of Health: (1) lower than 40 μ g/dL (normal), (2) 41 to

80 μ g/dL (acceptable), (3) 81 to 120 μ g/dL (excessive), a nd (4) greater than120 μ g/dL (dangerous). [The normal blood lead group cons isted of the 13 cont rols, who had blood

levels of less than 15 μ g/dL.] Approximately 70% of the workers had blood lead levels
classified as excessive or dangerous. DNA damage was measured by the comet assay, using whole blood, and DNA repair capacity was assessed by measuring DNA damage
before and after in vitro exposure of the cells to X rays , after various incubation times. A statistically significant ( P < 0.05) difference in both the level of basal DNA damage (before irradiation) and level of DNA da mage induced by X radiation was observed between the lowest and highest categories of lead exposure. Multiple regression analysis, in which variables included length of empl oyment, age, and blood lead concentrations,
showed that lead concentration was the main factor contributing to sensitization to genotoxic damage (that is, the difference in DNA damage before and immediately after irradiation). No significant differences in DNA repair capacity (as measured by DNA damage following incubation after irradia tion) among the different blood level groups were observed. The comet assay under alkalin e conditions mainly detects single-strand breaks, whereas X rays induced both single- and double-strand breaks; thus, repair of
double-strand breaks was not measured in th is study. Only 9% of the population smoked,
and the authors stated that smoking habits had no effect on DNA damage. [Strengths of this study included measurement of blood lead co ncentration and the ability to control for smoking.]05/08/03 RoC Background Document for Lead and Lead Compounds

148 Wu et al . (2002) evaluated SCE frequencies in 57 lead-exposed workers and 30 workers not occupationally exposed to lead (controls) at a stor age-battery manufacturer in Taiwan. Blood lead levels were measured, a nd lead-exposed workers were divided into a high-blood-level group ( ≥ 15 μ g/dL; mean = 32.5 μ g/dL; N = 23) and low-blood-level group (< 15 μ g/dL; mean = 9.3 μ g/dL; N = 34). The mean blood lead level in controls

was 4.2 μ g/dL. Zinc protoporphyrin also was meas ured and was significantly higher in both the high- and low-blood-level groups than in controls. [As discussed in Section 2, zinc protoporphyrin is a biom arker of effect, arising from the disturbance of heme synthesis by lead.] SCE, high-SCE frequenc y cells (HFCs) and DNA–protein crosslinks were measured by fluorescence spectrophotom etry in peripheral blood lymphocytes collected from the subjects. An HFC was de fined as a cell having a SCE frequency over
the median 95% value from the 19 nonsmoki ng control subjects. SCE frequencies and percentages of HFCs and DNA–pr otein crosslinks were signi ficantly higher in the highblood-level group (6.1 SCEs/cell, 11% HFC, a nd 1.5% crosslinks) than in the controls (5.2 SCEs/cell, 3% HFC, and 1.0% crossl inks). Moreover, frequencies of SCE and percentages of HFCs and DNA–pr otein crosslinks also were significantly higher in both smoking and nonsmoking workers with high bl ood lead levels than in smoking and nonsmoking controls. Multiple linear regres sion analysis showed that smoking and blood lead levels but not age and gender were signif icantly associated with the percentage of DNA–protein crosslinks and SC E frequency. [A strength of this study was the use of multiple linear regression models to adjust for age, gender, and smoking.]05/08/03 RoC Background Document for Lead and Lead Compounds

149 Table 5-6. Genotoxicity of lead compounds in vivo in humans

End point Results Blood lead
level a (μg/dL) Exposure (country) Reference

Chromosomal aberrations in peripheral blood lymphocytes + 37.7 lead-exposed workers Schwanitz et al.
1970 b,c Schwanitz et al. 1975 b,c

Chromosomal aberrations in peripheral blood lymphocytes + 38 to 64 storage-battery plant workers

(Italy) Forni et al. 1976 b

Chromosomal aberrations in peripheral blood lymphocytes + > 50 lead-exposed smelter workers

(Sweden) Nordenson et al. 1978 b

Chromosomal aberrations in peripheral blood lymphocytes + 38 to 96 storage-battery plant workers

(Iraq) Al-Hakkak et al. 1986 b

Chromosomal aberrations in peripheral blood lymphocytes + 22 to 48 storage-battery plant workers

(China) Huang et al. 1988 b,d

Chromosomal aberrations (also significantly dependent on radiation dose) in peripheral blood lymphocytes + 27.9 lead and zinc mine workers, also exposed to metals and
radon

(Slovenia) Bilban 1998

Chromosomal aberrations in peripheral blood lymphocytes +/– 40 to > 120 shipyard workers

(Scotland) O'Riordan and Evans
1974 b

Chromosomal aberrations in peripheral blood lymphocytes – average 48.7 lead smelter workers

(Finland) Maki-Paakkanen et al.
1981 b

Chromosomal aberrations in peripheral blood lymphocytes – > 30 children livin g near lead plant

(Germany) Bauchinger et al.
1977 b

Chromosomal
aberrations – NA lead manufacturing industry

(The Netherlands) Schmid et al. 1972 b,c

Chromosomal aberrations in peripheral blood lymphocytes – 40 volunteers who ingested lead acetate (49 days)

(The Netherlands) Bijlsma and de France
1976 e,f

SCE in peripheral blood lymphocytes + 22 to 48 storage-battery plant workers

(China) Huang et al. 1988 b,d

SCE in peripheral bloodlymphocytes (exposureresponse with blood lead levels) + 27.9 lead and zinc mine workers, also exposed to metals and
radon

(Slovenia) Bilban 199805/08/03 RoC Background Document for Lead and Lead Compounds

150 End point Results Blood lead
level a (μg/dL) Exposure (country) Reference

SCE in peripheral blood lymphocytes + 13.81 lead and zinc powder factory

(Turkey) Donmez et al. 1998

SCE in peripheral blood lymphocytes

High-SCE-frequency
cells +

+ 32.5 battery manufacturer

(Taiwan) Wu et al. 2002

SCE in peripheral blood lymphocytes +/– g average 48.7 lead smelter workers

(Finland) Maki-Paakkanen et al.
1981 b

SCE in peripheral blood lymphocytes +/– h 29 to 75 storage-battery plant workers

(Denmark) Grandjean et al. 1983 b

SCE in peripheral blood lymphocytes – 29 to 63 children living near lead
smelter

(Italy) Dalpra et al. 1983 b

SCE in peripheral blood lymphocytes – NA battery factory workers

(Mexico) Leal-Garza et al.
1986 b

SCE in peripheral blood lymphocytes – NR printing-press workers

(India) Rajah and Ahuja 1995

Micronuclei in peripheral blood leukocytes + 67.55 lead smelter workers

(Bulgaria) Vaglenov et al. 1997

Micronuclei in peripheral blood leukocytes + 27.9 lead and zinc mine workers, workers also exposed to metals
and radon

(Slovenia) Bilban 1998

Micronuclei in peripheral blood leukocytes + 60.92 starter-battery plant

(Slovenia) Vaglenov et al. 1998

Micronuclei in blood lymphocytes + 40 metal-powder producing workers (lead, zinc, cadmium)

(Turkey) Hamurcu et al. 2001

DNA-protein crosslinks in peripheral blood lymphocytes + 32.5 battery manufacture workers

(Taiwan) Wu et al. 2002

DNA damage (comet assay) in peripheral blood lymphocytes

significant relationship
at blood levels > 27

μ g/dL + four groups:

< 13

13 to 27

27 to 37

> 37 lead smelter workers (secondary)

(China) Ye et al. 199905/08/03 RoC Background Document for Lead and Lead Compounds

151 End point Results Blood lead
level a (μg/dL) Exposure (country) Reference

DNA damage (comet assay) in peripheral blood lymphocytes

basal level sensitivity to X rays +

+ 41 to >120 battery factory workers

(Colombia) Restrepo et al. 2000

DNA damage (comet assay) + 39 battery factory workers

(Italy) Fracasso et al. 2002

DNA repair capacity (comet assay) after exposure to X rays in peripheral blood lymphocytes – 41 to > 120 battery factory workers

(Colombia) Restrepo et al. 2000

Higher mitotic activity in peripheral blood lymphocytes + 40 volunteers who ingested lead acetate (49 days)

(The Netherlands) Bijlsma and de France
1976 b,e

Decrease in mitotic index in peripheral blood lymphocytes + NR printing press workers

(India) Rajah and Ahuja 1995

Increased mitotic activity + NA lead-exposed workers

(Germany) Schwanitz et al.
1970 b,c

Effects on cell division + NA (not available) Sarto et al. 1978 b,c

a NA = not available; NR = not reported.

b Not reviewed in text; source: ATSDR 1999.

c Foreign-language publication, not reviewed here; results are those reported by ATSDR 1999.

d Incorrectly listed in ATSDR (1999) as environmentally exposed children and as reporting negative results for SCE; no papers by Huang and genotoxicity in environmentally exposed children were found.

e Incorrectly listed in ATSDR (1999) as Bulsma.

f Study was reviewed in ATSDR (1999) (see mitotic index), but chromosomal aberrations were not reported.

g SCE frequency was higher in lead-exposed smokers than in non-exposed smokers, but not higher in leadexposed nonsmokers than control non-smokers.

h ATSDR (1999) also reported a slight positive corr elation with duration but not level of exposure.

5.5 Summary

Lead induced chromosomal aberrations in most studies in plants and in mammals (in

vitro and in vivo ) and DNA damage and fragmentation in mammals ( in vivo ; conflicting
results were observed in in vitro studies) and cell-free systems (in the presence of hydrogen peroxide) and inhibi ted DNA and RNA polymerase in cell-free systems and mammalian cells ( in vitro ). Conflicting results were obs erved for SCE and micronucleus induction in mammalian studies ( in vitro and in vivo ). Lead was not mutagenic in bacteria, and conflicting result s were observed in mammalian in vitro systems. Conflicting results may reflect differences in the model systems employed, the end points05/08/03 RoC Background Document for Lead and Lead Compounds

152 used to determine genotoxicity, and the lead compounds employed. In studies of humans occupationally exposed to l ead, there is evidence to s uggest that lead damages chromosomes or DNA; most studies were positive for induction of micronuclei, chromosomal aberrations, and DNA damage. Studies on SCE and studies in humans exposed environmentally to lead gave conf licting results. Studies in humans sometimes are difficult to evaluate, because little info rmation is given on how the populations were selected for study and because of potential exposure to compounds from occupational or environmental sources that may act in conjunc tion with lead to increase its genotoxic potential. Likewise, personal habits such as cigarette smoking and alcohol consumption affect the genotoxic properties of various co mpounds, including lead. However, many of
the more recent studies either controlled for smoking or reported an exposure-response relationship, suggesting that the genotoxic effects were due to lead exposure. Although lead(II) forms stable complexes with th e nitrogenous bases and phosphate groups of purified DNA, it is unlikely th at lead compounds are dire ctly genotoxic. However, several mechanisms exist by which lead compounds could indirectly alter DNA replication, fidelity, and repa ir, resulting in genotoxicity.05/08/03 RoC Background Document for Lead and Lead Compounds

153 

## 6 Other Relevant Data

This section is divided into three subsections: (1) absorp tion, distribution, and excretion of lead in humans, (2) other toxic effects of lead compounds, and (3) mechanistic studies relevant to lead carcinogenicity. In all subsec tions, the majority of the discussion focuses on human studies, since these are extensive.

6.1 Absorption, distribution, and excretion of lead in humans
6.1.1 Inorganic lead

6.1.1.1 Absorption

Inorganic lead can be absorbed by inhalation of fine particles and by ingestion. Before lead is absorbed by the lungs, a fraction of the inhaled lead is deposit ed in the respiratory tract. In adults, the rate of deposition of airborne lead is approximately 30% to 50%. This rate is dependent on the size of the particles and the ventilation rate of the individual. Smaller particles (< 1 μ m) have been shown to have greater deposition and absorption rates than larger pa rticles (ATSDR 1999).

Ingestion of inorganic lead results in gastrointestinal (GI) absorption in humans and rodents. Although GI absorption is influenced by chemical species, no inorganic lead compound studied to date is completely unavailabl e, as demonstrated in studies of rats by
Dieter et al. (1993). GI absorption of l ead also is age-dependent in humans and rodents. It is estimated that young children absorb 4 to 6 times more lead than do adults. Dietary constituents, also may influence GI absorpti on, as shown in Table 6-1. Deficiencies in iron, calcium, and zinc appear to increase the GI absorption of lead, while a high-protein diet appears to reduce absorption (Hammad et al. 1996).

Lead also can be absorbed through the ski n, as demonstrated by a study in which 4.4 mg of lead (as lead acetate or lead nitrate) was applied to the skin under a covered plastic patch on the forearms of human subjects; 1.3 mg of lead was not recovered from washing
of the skin and was detected in sweat, blood, and urine with in 6 hours of the application (Stauber et al. 1994).05/08/03 RoC Background Document for Lead and Lead Compounds

154 Table 6-1. Effects of nutritional elements on gastrointestinal lead absorption in
animals

Element Species Index of effect Interactive effect

Calcium rat lead in tissues and severity of effect at low levels of dietary
calcium low dietary calcium (0.1%) increases lead absorption and severity of effects

Calcium rat lead retention calcium deficiency increases retention

Calcium rat lead in tissues at high levels of dietary calcium during

pregnancy high dietary calcium reduces release of
lead from bone

Calcium pig lead in tissues at low levels of dietary calcium low dietary calcium increases lead absorption

Calcium horse lead in tissues at low levels of dietary calcium low dietary calcium increases lead absorption

Calcium lamb lead in tissues at low levels of dietary calcium low dietary calcium increases lead absorption

Calcium chick lead absorption and retention calcium deficiency increases lead absorption and retention

Iron rat tissue levels and relative toxicity
of lead iron deficiency incr eases lead absorption and toxicity

Iron rat lead absorption in everted duodenal sac preparation reduction in intubated iron increases lead absorption; increased levels decrease lead uptake

Iron rat in utero or milk transfer of lead in pregnant or lactating rats iron deficiency increases both in utero and milk transfer of lead to sucklings

Iron mouse lead retention iron deficiency has no effect on lead
retention

Protein rat body lead retention low dietary protein either reduces or
does not affect lead retention in various
tissues

Protein rat tissue levels of lead casein diet increases lead uptake, compared with soybean meal

Protein rat lead uptake by tissues both low and high dietary protein increase lead absorption

Milk
components rat lead absorption lactose-hydrolyzed milk does not increase lead absorption, but ordinary
milk does

Milk
components rat lead absorption lactose in diet increases lead absorption, compared with glucose

Zinc rat lead absorption low-zinc diet increases lead absorption

Zinc rat lead transfer in utero and in milk during lactation low-zinc diet of mother increases lead
transfer in utero and in maternal milk

Zinc rat tissue retention low-zinc diet increases brain lead levels

Sources: Fullmer 1997 (chick), ATSDR 1999 (all others).05/08/03 RoC Background Document for Lead and Lead Compounds

155 6.1.1.2 Distribution and PBPK models

The mean-life of lead in blood is approxima tely 30 days. In blood, lead is partitioned between red cells and plasma. The relations hip between whole-blood lead and plasma lead is linear at lower concentrations, but at higher concentrations, levels in plasma are higher than would be expected ba sed on a linear relationship (Manton et al. 2001) (see Figure 6-1).

Source: ATSDR 1999.

Figure 6-1. Curvilinear relationship of human serum lead to blood lead

Note: Crosshatched area represents several overlapping data points.

Extensive physiologically based pharmacoki netic (PBPK) modeli ng has been conducted on inorganic lead in both adults and child ren (O'Flaherty 1993, 1995). The skeleton is a major compartment for inorganic lead depos ition in mammals; between 75% and 90% of the body burden of lead is found in bones a nd teeth. In humans, bone lead levels gradually increase over the lifes pan, as demonstrated in a se ries of autopsy and biopsy studies by Aufderheide et al. (1992). The half-life of lead in bone depends on bone type;
it is estimated that the half- life of lead in cortical bone may be as long as 25 years (Marcus 1985). For this reason, analyses of teeth and bone provide an integrated biomarker of previous lead exposure, which ha s been used in severa l important studies of lead toxicity in both children and adults. L ead also is transferre d across the placenta and05/08/03 RoC Background Document for Lead and Lead Compounds

156 is excreted in breast milk. Some evidence in dicates that the fetus accumulates lead in
both the skeleton and soft tissue (ATSDR 1999).

6.1.1.3 Mobilization

Skeletal lead can be mobilized under nor mal and pathophysiological conditions that affect bone mineral metabolism. For example, lead is mobilized from the skeleton during pregnancy and lactation, as demonstrated in a series of elegant studies using stable isotope analysis to distingui sh skeletal lead from envi ronmental lead in Australian women (Gulson et al. 1997). In women, lead also is released from bone stores at menopause (Silbergeld et al. 1988), which can result in significant elevations of blood lead that may be associated with increases in blood pressure a nd other toxic effects (Hertz-Picciotto and Croft 1993). Pathophys iological conditions that favor bone resorption, such as Paget’s disease, hypothyroi dism, and prolonged bed rest, also increase blood lead concentrations; this occurrence has been in terpreted as a redi stribution of bone lead into blood (Silbergeld et al. 1993).

Mobilization of maternal lead during pregnancy was studied in female Sprague-Dawley rats (Buchet et al. 1977). Treatment regimens included controls (group 1), rats given 1 mg/L of lead as lead nitrate in drinking water for 150 days before mating, over gestation, and for three weeks after parturition (group 2) , rats given 1 mg/L lead in drinking water for 150 days before mating, discontinued on day 1 of pregnancy (group 3), and rats given 1 mg/L lead in drinking water for 150 da ys, but discontinued 50 days before mating (group 4). On day 21 after delivery, lead concentrations a nd free porphyrins were
measured in blood and various tissues. The re sults are summarized in Table 6-2. It was concluded that lead stored in the orga nism could be mobilized during gestation.

Lead also has been measured in a variety of tissue samples in humans. In one study investigating levels of inorga nic chemicals in brain tumors, Al-Saleh and Shinwari (2001) measured concentrations of lead, as well as cadmium and mercury, in samples of tumors from 23 patients with malignant and 21 patie nts with benign brain tumors who were undergoing treatment at a Saudi Arabian hospital. Lead levels were somewhat higher in malignant than in benign tumors (0.65 vs. 0.61 μ g/g); however, the authors noted that these concentrations were much higher than reported for brain tissue in a non-Saudi population. In addition, the lack of any biomar ker surveyed in nondiseased tissue or other indices of cumulative lead exposure and th e absence of a true control group for comparison preclude reliable inference from this study.05/08/03 RoC Background Document for Lead and Lead Compounds

157 Table 6-2. Mobilization of lead during gestation in Sprague-Dawley rats

Concentration of lead on day 31 after delivery Concentration of free porphyrins in brain on day 31 after delivery

Exposure group Blood ( μ g/L) Brain (ng/mg of protein) (ng/mg of protein)

Group 1 (controls)

Mothers 30 0.5 1.0

Offspring 20 0.02 0.8

Group 2 (exposed before mating, over gestation, and after parturition)

Mothers 18 0.2 0.7

Offspring 9 0.02 0.7

Group 3 (exposed before mating)

Mothers 11 0.2 0.9

Offspring 6 0.02 0.8

Group 4 (exposed until 50 days before mating)

Mothers 49 0.7 1.6

Offspring 36 0.23 1.1

Source: Buchet et al. 1977.

6.1.1.4 Excretion

Excretion of lead does not depend on the ro ute of exposure (ATSDR 1999). Dietary lead
excreted in the feces includes both lead that was not absorbed by the GI tract and lead that was excreted in the bile. The major routes of excretion of absorbed lead are urinary and biliary clearance, and excretion of lead in the feces generally is greater than excretion in the urine. In rats, fecal excretion of lead due to biliary clearance may still exceed urinary excretion even for lead administered i.v. Excretion in ra ts, dogs, and mice is a multiphasic process. In rats, excretion of l ead following i.v. administration is biphasic, with half-lives of 21 hours for the fast phase and 280 hours for the slow phase. In dogs, a triphasic process with half-lives of 12, 184, and 4,951 days has been reported. The terminal phase of the biphasic elimination curve observed for mice had a half-life of 110 days. In humans, the total excretion rate may be lower in infants than in adults, resulting in retention of a larger percentage of the total amount of lead absorbed.

6.1.2 Organic lead compounds

Organic lead compounds are toxicokinetically distinct from inorganic lead compounds in terms of absorption and distribution. Eventual ly, organic lead compounds are dealkylated by hepatic metabolism and stored in the body as inorganic lead. Owing to their greater lipophilicity, organic lead compounds are rapi dly partitioned into soft tissues, as demonstrated by average lead levels in ma jor viscera (i.e., lung, brain, liver, kidney, spleen, and heart tissue) of approximately 7 to 100 mg/kg in rats and 7 to 30 mg/kg in05/08/03 RoC Background Document for Lead and Lead Compounds

158 dogs following inhalation exposure to lethal doses of tetraethyl lead (12 to 46 mg/m 3 ) or tetramethyl lead (4 to 63 mg/m 3 ) (Davis et al. 1963).

It has been shown that inhalation of TEL results in much higher levels of lead in the brain than does exposure to in organic lead. Boudene et al. (1977) exposed 40 female Wistar rats to an aerosol of gasoline containing 0.6 g/L of tetraethyl lead and enhanced with organic 210 Pb chelated with dibenzoylmethane. Animals were placed in a box and breathed the gasoline aerosol for 30 to 45 mi nutes. Lead was rapidly cleared from the lungs, with less than 10% rema ining after 48 hours. Six days after exposure, 40% of the
dose was eliminated in the feces and 15% in the urine; 40% was fixed in the bones, 4% was distributed among soft tissues, and 1% rema ined in the lungs. In another inhalation study (nose-only exposure), 203 Pb-labelled TEL was administered over 40 to 60 minutes (Morgan and Holmes 1978). Approximately 20% to 25% of lead particulates generated from engine exhaust was deposited in the lungs of 12 male albino rats, and at least half of the deposited lead was absorbed, with a half -life of less than one hour. Less than 2% remained in the lungs after 7 days.

Organic lead compounds also have been show n to be rapidly and extensively absorbed through the skin of rats and rabbits (ATSDR 1999). One st udy showed that 0.75 mL of TEL applied to the abdominal skin of rabbits resulted in 1.06 mg of lead being detected
in the carcass after 0.5 hour s and 4.41 mg after 6 hours of exposure. However, these
measurements did not include the contents of the intestinal tract, which were inadvertently discarded. Following dermal app lication of 0.75 mL of TEL to three other rabbits, 7.9 to 9.3 mg of lead was detected in the carca sses after 4 hours of exposure (Kehoe and Thamann 1931).

Excretion of organic lead differs from that of inorganic lead (see Section 6.1.1.4, above). A major route of elimination of inhaled tetr aalkyl lead compounds is exhalation (ATSDR 1999).

6.2 Other toxic effects of lead compounds
The toxicity of lead compounds to humans ha s been extensively studied. For the last 100 years, considerable attention has been focused on the neurotoxic effects of lead compounds in young children, following reports of the exposure of child ren to lead-based house paint. Because of the very large amount of published literature on lead toxicity, this section will provide only a brief review, with references to major reviews and government documents.

Human exposure to lead is regulated in the occupational and non-occupational environments (see Section 2.9 and Appendix A fo r lists of lead regul ations). Several end points of concern have been associated with human exposure to lead and lead compounds; end points identified in adults, child ren, and/or fetuses include (but are not limited to) neurotoxicity, nephr otoxicity, hematoxicity and anemia, reproductive toxicity, developmental toxicity, and car diovascular toxicity. The end points are discussed briefly
below.05/08/03 RoC Background Document for Lead and Lead Compounds

159 6.2.1 Neurotoxicity

By the 1930s, it was increasingly recognized th at exposure to lead compounds (inorganic, lead carbonate based, and lead chromate and oxide pigments) was a frequent cause of encephalopathy in children. Under conditions of chronic exposure, the neurotoxic effects of exposure to lead in pain t included loss of speech, seiz ures, and coma (McKhann 1932). Children who survived these severe events freq uently were retarded intellectually and in their motor skills (Silbergeld 1997). Reviews of several large pros pective studies of children’s neurocognitive and behavioral deve lopment reached a consistent conclusion that “subencephalopathic” expos ures to inorganic lead, i.e ., at doses associated with

blood lead levels as low as 10 μ g/dL, are significantly associ ated with poor outcomes in neurocognitive and behavioral development a nd with impairments in attention, hearing, and school attainment (ATSDR 1999, Silbergeld 1997).

Although the CNS toxicity of lead in children became the critical end point in pediatrics, inorganic lead compounds also can affect both CNS and peripheral nervous system (PNS)
function in adults. Neurotoxic manifestat ions depend on both dose and duration of exposure. High levels of exposure cause disabling impairments in PNS function, described as “painter’s wrist” or “foot drop” in the 18th and 19th centuries, as well as profound mental changes and cognitive impairme nts, which were observed in workers in
lead industries in the 19t h century. In the 1920s, when production of TEL began in the United States, cases of acute psychosis a nd hallucinations in workers were reported. Some recent reviews (Stewart et al . 2002, Kamel et al . 2002) have suggested that adult lead exposure may be associated with incr eased risks of neurodegenerative disease in aging, specifically, amyotrophic la teral sclerosis and dementias.

6.2.2 Nephrotoxicity

The renal toxicity of lead has been well described for over 100 years. Acute nephrotoxicity has been desc ribed in lead-intoxicated children (Loghman-Adham 1997). The evidence in both humans and experimental animals indicates that thresholds exist for lead nephropathy. In rodents, proximal tubul ar injury occurs at blood lead levels of 60 μg/dL. Observations in humans indicate th at blood lead levels greater than 60 μg/dL for up to 12 years are required for nephropathy. Increased risk of end-stage renal failure has been reported in lead worker s long after cessation of exposure.

6.2.3 Hematoxicity and anemia

Lead inhibits the biosynthesis of heme thr ough highly specific intera ctions with one of the rate-limiting enzymes in this pathway, ALAD. As a consequence of this effect, levels of some heme precursors are elevated (by f eedback deregulation), and heme levels are decreased (Silbergeld 1987). These effects have been widely used as biomarkers for lead exposure, but they also represent toxic effects of lead and may play a role in target organ responses. Inhibition of heme production, along with toxic eff ects on globin synthesis and erythrocyte integrity, is asso ciated with anemia at high levels of exposure (> 40 μ g/dL).05/08/03 RoC Background Document for Lead and Lead Compounds

160 6.2.4 Reproductive toxicity

Lead is toxic to sperm and can alter e ndocrine function in ad ults. Decreases in spermatologic parameters were reported in men exposed to inorganic lead compounds in battery plants and were associated with blood lead levels as low as 40 μ g/dL, which are well within current occupational standards; in some cases, these deficits were ameliorated when lead exposure and blood lead levels were reduced (Sallmen 2001). No specific effects of lead have been reported on female reproduction; however, lead is toxic to fetal development, and these effects sometimes ar e misinterpreted as effects on pregnant women or women of childbearing age.

6.2.5 Developmental toxicity

Lead crosses the placenta and is accumulated in fetal organs, including the brain. High exposure to inorganic lead can induce intraute rine death and stillbirth. At lower levels, prenatal exposure to lead, indicated by cord blood lead level obtain ed at parturition, is associated with a range of adverse effects, including decreased gr owth in stature and delays in early infant development. If no furt her elevated lead exposure occurs after birth, development generally, but not always, norma lizes, as demonstrated in longitudinal studies in which the subjects were enrolled prior to birth (Bellinger et al. 1992).

6.2.6 Cardiovascular toxicity

Several studies have reported significant a ssociations between bl ood lead level and blood pressure in adult men and women (Hertz -Picciotto and Croft 1993, ATSDR 1999). In both of the NHANES surveys (II and III) of lead e xposure and health status in the United States, blood lead level was positively associated with blood pressure, in a dose-related
fashion. It was estimated that the effects of lead exposure on blood pressure contribute significantly to risks of hypert ensive heart disease and stro ke in the U.S. population.

6.2.7 Other effects in rodents

It is important to note that all of these toxic effects of lead described in human populations have been observed in rodent models at similar blood lead levels. Lead
induces both PNS and CNS toxicity; affects CNS development in young animals, resulting in impaired learning pe rformance and hyperactivity; inhibits heme biosynthesis; affects intrauterine growth; affects aud itory-evoked responses; impairs reproductive function in males; and induces hypertension.

6.3 Mechanisms of lead carcinogenesis
Knowledge of the mechanisms by which metals cause cancer remains uncertain, even for
those metals for which the evidence of huma n carcinogenicity is considered adequate. At high concentrations, lead can bind to DNA and change its conformation (Smirnov and Shafer 2000), break nucleic acids (Brown et al. 1983, Wedrychowski et al. 1986), and induce cell proliferation, measured by increase d mitotic indices or increased thymidine incorporation (Calabrese and Baldwin 1992). Ho wever, the exposure levels used in these
studies are well above the levels associated with other severe t oxic effects of lead, including tissue damage and cytotoxicity. Because lead can cause tumors in experimental05/08/03 RoC Background Document for Lead and Lead Compounds

161 animals at exposure levels that are not associated with tissue damage (Waalkes et al. 1995), these events probably are not releva nt to mechanisms of carcinogenesis.

6.3.1 Possible mechanisms of genotoxicity and carcinogenicity

Even though lead has been intensely studied for many years, the mutagenic, clastogenic, and carcinogenic properties of lead and lead compounds are not well understood. IARC (1980, 1987) has determined that there is suffi cient evidence to conclude that lead and inorganic lead compounds cause cancer in experimental animals, but that sufficient evidence in humans is lacking. Several possi ble mechanisms have been examined to better understand the carcinogenic properties of lead and the conditions required for this effect. These include mitogenesis, chronic ne phropathy, effects on gene transcription, and various indirect mechanisms of genotoxicity.

6.3.1.1 Mitogenesis

Increased cell proliferation ( 40-fold) was noted in the prox imal tubular epithelium of adult female Sprague-Dawley rats following a single i.p. injection of lead acetate at 40 mg/kg b.w. No renal pathology was noted in le ad-exposed rats. A similar increase in the mitotic index (45-fold) was observed in the pr oximal and distal ep ithelium of the renal cortices of adult female CD-1 mice given a single dose of lead acetate at 5 mg/kg b.w. As in the rat study, no detectable microscopic lesions were observed in the renal tubules (Choie and Richter 1972). A similar prolifer ative mitogenic response, but of lesser magnitude, was observed in the liver of adu lt male Wistar rats following administration of a single dose of lead acetate at 100 μ mol/kg b.w. Lead acetate caused a significant enlargement of the liver, with a 30-fold increase in DNA synthesis as measured by labeled thymidine incorporation (Columbano et al . 1983). In this context, several other
studies were conducted to determine whether mitogen-induced cell proliferation in the liver supported the formation of foci.

A series of studies used diethy lnitrosamine to initiate hepatocytes in male Wistar rats (Columbano et al. 1990, Ledda-Columbano et al. 1992, Coni et al. 1993a, 1993b). Regenerative mitogenesis was stimulat ed by partial hepatectomy and carbon tetrachloride, whereas prolifer ative mitogenesis was stimulat ed by i.v. injection of 100 μmole/kg of lead nitrate and other mitogenic chemicals. Both types of treatment induced cell proliferation primarily w ithin zone 1, produced a sim ilar labeling index (65% to 70%), and stimulated serum growth fact ors capable of inducing DNA synthesis in primary hepatocyte cultures. However, the in itiated hepatocytes did not respond to lead nitrate but did respond to regene rative mitogenic stimuli. Therefore, DNA synthesis alone apparently is not a sufficient condition for cancer development. Some possible explanations include differences in the gene s involved in the grow th signal transduction and growth factors induced, elimination of altered hepatocytes by apoptosis during regression after proliferative mitogenesis, or differences in the subpopulation of cells responding (ploidy state).

Coni et al. (1993b) provided evidence of differen ces in patterns of mRNA expression for growth factors following regenerative mit ogenesis and proliferative mitogenesis. Following partial hepatectomy or carbon te trachloride administration, increased05/08/03 RoC Background Document for Lead and Lead Compounds

162 expression of c-fos, c-jun, and c-myc were noted; however, following lead nitrate administration, only expression of c-jun increased. Furthermore, studies by LeddaColumbano et al. (1994) demonstrated that a single injection of lead nitrate induced a rapid increase in tumor necrosis factor- α (TNF- α ). Inhibition of TNF- α resulted in an inhibition of liver cell prolif eration, suggesting that TNF- α is involved in triggering proliferative mitogenesis in the liver. This finding is in contrast to observations on regenerative mitogenesis, in which the primary growth f actors involved are hepatocyte growth factor, transforming growth factor- α , and transforming growth factor- β (Kinoshita et al. 1989, Lindroos et al. 1991). These studies sugge st that proliferative mitogenesis induced by chemical exposure, unlike regenerative mitogenesis, does not have a significant role in initiation or promotion of hepatocarcinogenesis. Although the mechanism by which lead induces renal tumors in rodents has not been established, mitogenesis may be a contribu ting factor. Furthermore, ma rked differences in organspecific susceptibility to this response are consistent with observations of renal but not liver tumors in animals (Calabrese and Baldwin 1992).

6.3.1.2 Nephropathy

Because the kidney is a frequent target fo r lead-induced cancer, studies have been undertaken to test the hypothesi s that renal cancers are a c onsequence of renal pathology due to lead exposure. Goyer (1993) reviewed several current issues in regard to lead toxicity, including nephropathy and cancer. As de scribed above, the toxic effects of lead on the kidney in both humans and experiment al animals begin with morphologic changes in tubular endothelial cells, which may sl owly progress to a chronic irreversible nephropathy after years of heavy exposure (F owler 1993). The role of nephrotoxicity in renal carcinogenesis remains unclear. In rode nts, progression from acute reversible nephropathy to chronic irreversible nephr opathy to renal adenocarcinoma has been demonstrated; however, the evidence in humans is less clear. No evidence indicates that lead induces male-specific nephropathy or hyaline-droplet nephropathy. As noted in Section 4, lead can induce tumors in female and male mice, as well as rats, and at exposures that do not indu ce frank renal toxicity.

A characteristic histologic finding of early or acute lead-induced nephropathy is the appearance of intranuc lear inclusion bodies in renal proximal tubule cells (VicenteOrtega et al. 1996). These bodies contain lead comp lexed with acidic proteins, which may include human lead-binding protein or si milar proteins; in this complex, lead is bound in a nondiffusible form (Moore and G oyer 1974, Saryan and Zenz 1994). Inclusion bodies are thought to represent a defens e mechanism by which the cytoplasmic
concentrations of lead are lowered. Furthermor e, since they are excreted in the urine, inclusion bodies would provide the kidneys with a method fo r eliminating surplus lead without destroying the viability of the tubul ar lining cells (Saryan and Zenz 1994). Few
or no nuclear inclusion bodies are observed in chronic lead ne phropathy (ATSDR 1999). The presence of intranuclear inclusion bodi es in the kidney is used as a primary biomarker of effect for lead (ATSDR 1999).

Following in vivo lead exposure, lead inclusion bodies commonly are found in the cytoplasm and the nuclei of osteoclast s, but not of other bone cells (Pounds et al. 1991).05/08/03 RoC Background Document for Lead and Lead Compounds

163 These inclusion bodies may c ontain high-affinity binding pr oteins and may sequester lead, but also may indicate a potential for modulation of gene expression. High-affinity cytosolic lead-binding proteins also have been identified in the kidneys and brain. These high-affinity zinc- and lead-b inding proteins are thought to moderate the inhibition of ALAD by lead through chelation of lead and donation of zinc; these proteins subsequently translocate lead to the nucleus, where it may influence gene expression. In the rat kidney, the high-affinity lead-binding protein was found in intranuclear inclusion
bodies and was associated with nuclear chro matin. Similar lead-binding proteins have been found in human kidney, liver, and brain cytosol. In rats, the brain lead-binding protein is not the same as that found in the kidney and is developmentally regulated. Only traces of this protein were detected in neona tal rats, but protein concentrations increased
to adult levels within 2 week s; the increased protein levels also resulted in increased resistance to lead-induced encephalopat hy. Development of this resistance is hypothetically related to the formation of lead -protein inclusion bodi es in the astroglia, which, as they mature, develop the abili ty to sequester lead (ATSDR 1999).

6.3.1.3 Clastogenicity

Exposure of mice to lead causes chromoso mal damage (Winder and Bonin 1993, Johnson 1998). More recently, Valverde et al. (2002) administered lead to mice by inhalation at a concentration of 0.0068 μg/ cc (equivalent to 6.8 mg/m 3 ) for 60 minutes twice per week; they reported induction of DNA damage, de tectable by electrophoresis, in many organs, including liver, kidney, brain, and lung. Yu an and Tang (2001) reported detection of DNA damage in the comet assay in the second and third generations of mice exposed to lead in drinking water at 1 or 0.25 mg/L. Cons istent with these findi ngs in experimental systems, researchers have reported chromoso mal aberrations, micronuclei, and increased SCE in studies of lead-exposed worker s (Gebhart 1984, Johnson 1998). However, these
effects were not found consiste ntly and generally were repor ted in occupational cohorts (Vaglenov et al. 2001) with blood lead levels in ex cess of the current OSHA standard (30 μ g/dL).

6.3.1.4 DNA repair

The strongest evidence that lead may be pe rmissive rather than initiating in its carcinogenic effects comes from studies of co-e xposures to lead a nd directly genotoxic agents. As discussed in Section 5.3.1, lead in vitro can increase mutations in cells exposed to UV radiation (Hartwig 1994), X rays (Fischer and Skreb 2001), or the chemical mutagen N -methyl- N  ́-nitrosoguanidine (Roy and Rossman 1992). Similar in

vivo interactions between lead and sensitivity to genotoxi c agents were suggested by Restrepo et al . (2000), who exposed lymphocytes fr om battery workers to X rays in vitro

. These effects may be due to lead’s ability to decrease the accuracy of DNA polymerase and the fidelity of RNA synthe sis. As reported by Zelikoff et al. (1988), lead affects DNA synthesis fidelity in CHO V79 cells. Hartwig et al. (1990) reported that lead interferes with repair of UV-induced DNA damage in vitro , which appears to be the same mechanism by which several toxic heavy metals act to prevent closure of single-strand DNA breaks (Snyder et al. 1989).05/08/03 RoC Background Document for Lead and Lead Compounds

164 6.3.1.5 Oxidative damage

A general mechanism for metal toxicity invo lves generation of fr ee radicals, either through depletion of cellular antioxidants, such as glutathione, or production of ROS (Klein et al. 1991). Lead has been shown to incr ease hydrogen peroxide production in cells (Ariza et al. 1998, Yang et al. 1999) (see Sections 5.3.1 and 5.4). In the presence of exogenously added hydrogen peroxide, lead in creases the formation of the DNA adduct 8-OHdG (Yang et al. 1999). Fracasso et al. (2002) reported that significantly elevated levels of DNA breaks in lymphocytes of lead-exposed battery plant workers were significantly and positively co rrelated with ROS producti on and negatively correlated with glutathione levels. In addition, both the increase in ROS and the decrease in glutathione levels di ffered significantly between lead -exposed and unexposed controls. Another mechanism of adduct formation may involve δ -aminolevulinic acid, the heme precursor whose levels are elevated by l ead exposure through feedback disinhibition of the enzyme ALA synthase (Silbergeld 1987) . ALA can generate free radicals (HermesLima et al. 1991) and has been shown to cause oxidative damage to DNA in CHO cells in

vitro through the formation of 8-OHdG (Yusof et al. 1999). The role of oxidative damage to DNA in human lead toxicity also is supported by a recent study of 7,8-dihydro-9- oxoguanine adducts in lymphocytes collected from persons exposed environmentally to metals, including lead, chromium, cadmium, and nickel (Merzenich et al. 2001).

6.3.1.6 DNA-binding proteins

Lead is known to bind to several DNA-bi nding proteins, including protamines and histones, as well as transcription regula tors such as stimulatory protein-1 and transcription factor IIA (Hanas et al. 1999, Petering et al. 2000, Zawia et al. 2000, Quintanilla-Vega et al. 2000, Silbergeld et al. 2000). In fact, many, if not all, zincbinding nuclear proteins proba bly also can bind lead, and thus potentially dysregulate gene expression, as first suggested by Sunderm an and Barber (1988). The critical role of zinc in conferring appropriat e conformational structure has been well demonstrated for the zinc finger proteins, many of which ar e transcription regula tors, such as the glucocorticoid receptor (O'Halloran 1993, Searles et al. 2000). Quintanilla-Vega et al

. (2000) reported that lead could bind at a sulfhydryl and a nonsulf hydryl site to human protamine (HP2), a DNA-associated protein that regulates the condensation of sperm DNA. Several lines of evidence, including sp ectroscopy, nuclear magne tic resonance, and circular dichroism analysis, indicate that prot ein configuration is changed when lead is bound (Quintanilla-Vega et al. 2000, Razmiafshari et al. 2001). When HP2 is bound to lead, its subsequent binding to consensus sequences in DNA is significantly reduced (Quintanilla-Vega et al. 2000, Silbergeld et al. 2000).

Because one of the functions of protamines and histones, analogous somatic-cell nuclear proteins, is to protect DNA (Mirsky and Silverman 1972), genetic material may become more vulnerable to damage from other s ources in the presence of lead-containing protamines or histones. Liang et al. (1999) reported that wh en nickel or copper was bound to HP2 in place of zinc, single- and double-strand DNA breakage increased, as well as oxidative damage to both purine a nd pyrimidine bases of DNA. These authors suggested that the DNA damage induced in th e presence of HP2 and metals was related05/08/03 RoC Background Document for Lead and Lead Compounds

165 to interactions of HP2 with DNA, as well as to the redox properties of HP2–metal complexes.

6.3.1.7 Tumor suppressor proteins

A final potential mechanism for lead carcinogeni city involves its inte ractions with tumorsuppressor proteins, at the pr e- and post-translational leve l. The tumor-suppressor protein p53 is a zinc-binding protein. It has been s hown that when p53 is exposed to cadmium, the protein is structurally a ltered, with functional consequenc es similar to those resulting
from mutation of the p53 gene (Hainaut and Milner 1993, Hainaut and Mann 2001). Other proteins related to tu morigenesis have been identi fied in studies of gene expression. Although these analyses were undert aken to identify novel targets related to lead neurotoxicity, some of the results are relevant to mechanisms of carcinogenicity.

Bouton et al . (2001) undertook a broad analysis of lead-induced alterations in gene expression, using immortalized rat astrocytes exposed to 10 μ M lead acetate or 10 μ M sodium acetate (as control). Extensive controls were run to ensure reproducibility of the results. In the Clontech array (which contains a set of 418 genes), expression of 48 genes was upregulated and expression of 12 gene s was downregulated. For instance, lead exposure downregulated expressi on of the gene for the tumor suppressor DCC (deleted in colon cancer) precursor protein. In the InCyte microarray (which included 282 genes also represented on the Clontech array), expr ession of 34 genes was upregulated and expression of 18 genes was downregulated. Amon g these, lead significantly affected the expression of genes for zinc-bi nding transcription factors (not further identified). In a more limited analysis of gene expression in astrocytes, Li and Rossman (2001) reported that exposure of glioma cel ls in culture to lead (at concentrations as low as 100 μ M) resulted in downregulation of expression of the gene for thrombospondin 1, which has been considered to be a tumor-suppressor pr otein. These data suggest the importance of
further research on the interaction of l ead with expression of genes involved in tumorigenesis.

6.3.2 Indirect mechanisms

Glutathione transferase P (GST-P) is increase d in rat kidney and liver following exposure to lead, and overproduction of GST-P is known to be a marker for hepatocarcinogenesis in the rat (Suzuki et al. 1996). These effects offer a possibl e explanation for the ability of
lead to induce cancer wit hout being a potent direct-a cting mutagen (Johnson 1998). Oberley et al. (1995) demonstrated marked inducti on of specific GST isoforms in specific kidney cell types in female Sp rague-Dawley rats and their pups following
chronic administration of lead acetate in drinking water. Increases in GSTs preceded irreversible renal damage; however, the au thors concluded that the observed renal damage was not related to neoplas tic events. In another study, Daggett et al. (1998) determined that glutathione depletion a nd oxidative stress were not responsible for changes in the production of GSTs in rat kidney or liver. Sprague-Dawley rats were injected with lead acetate at 114 mg/kg b.w. and examined at 0.5, 1, 3, 6, and 12 hours after the injection. Two other exposure groups received injections on three successive days and were examined at 72 hours and 7 da ys after the first injection. Lead exposure
resulted in increased levels of most GSTs in the kidney but decreased levels of most GSTs in the liver. GST-P1 was the only subuni t increased in the liv er. GST increases in05/08/03 RoC Background Document for Lead and Lead Compounds

166 the kidney were independent of glutathi one depletion or malondialdehyde (MDA) production. MDA was used as a marker for lip id peroxidation. In contrast, increased
GSTP1 in the liver did correlate with glutathione depleti on and MDA production. Histopathological effects were noted in the kidneys but not in th e liver. Although these observations suggest an adaptive response to lead toxicity, they do not indicate that oxidative stress is a primary mechanism of toxi city. One possible explan ation is that lead reduces the activity of glutathione in the kidney without de pleting it (Daggett et al. 1998).

6.4 Summary
Lead absorption in humans and laboratory animal s is affected by age, the chemical form of lead, and minerals in the diet (e.g., iron, calcium, and zinc). Inorganic lead can be absorbed by inhalation of fine particles and by ingestion. In adults, the rate of deposition of airborne lead in the resp iratory tract is approximately 30% to 50% and is dependent on the size of the particles and th e ventilation rate of the indivi dual. Ingestion of inorganic lead results in GI absorption in humans. GI absorption declines with age, with children absorbing 4 to 6 times more lead than adults . Dietary deficiencies in iron, calcium, and zinc increase lead absorption and retention, wh ereas a high-protein di et appears to reduce absorption. Lead also can be absorbed th rough the skin. After absorption, lead is distributed to blood plasma, nervous system, a nd soft tissues. In humans, the relationship between whole-blood lead and plasma lead levels is linear at lower concentrations, but at higher concentrations, levels in plasma ar e higher than would be expected based on a linear relationship.

The skeleton is a major compartment for inor ganic lead, as approximately 75% to 90% of the lead body burden is found in bones and teet h. In humans, bone lead levels gradually increase over the lifespan. Th e half-life of lead in bone depends on bone type. Lead analyses of teeth and bone provide an integr ated biomarker of previous lead exposure.
Lead also is transferred across the placenta and is excreted in breast milk. Some evidence
indicates that the fetus accumulates lead in bot h the skeleton and soft tissue. Skeletal lead can be mobilized under normal conditions, su ch as pregnancy, lactation, and menopause, and under pathophysiological conditions, includ ing Paget’s disease, hypothyroidism, and prolonged bed rest; this mobilization aff ects bone mineral metabolism and increases
blood lead concentrations.

Excretion of lead does not depend on the route of exposure. Dietary l ead excreted in the
feces includes both lead that was not absorbed by the GI tract and lead that was excreted in the bile. The major routes of excretion of absorbed lead are urinary and biliary clearance, and excretion of l ead in the feces generally is greater than excretion in the urine. In humans, the total excretion rate for lead may be lower in infants than in adults, resulting in retention of a larger percenta ge of the total amount of lead absorbed.

The toxic effects of lead include neurotoxic ity, nephrotoxicity, hematoxicity and anemia, and reproductive, developmental, and cardiovascular effects. These end points have been identified in adults, children, and/or fetuse s. Lead exposure was a frequent cause of encephalopathy in children. Chronic exposure of children to lead in paints resulted in neurotoxic effects including loss of speech, seizures, and coma. Children who survived these severe events frequently were retarded intellectually and in their motor skills. In05/08/03 RoC Background Document for Lead and Lead Compounds

167 adults, lead is a potent neur otoxin affecting the CNS and the PNS, with neurotoxic manifestations dependent on dose and durat ion of exposure. Recently, reviews have suggested that adult lead exposure may be associated with increased risks of neurodegenerative disease in aging, speci fically, amyotrophic lateral sclerosis and dementias. Acute nephrotoxicity has been described in lead-intoxicated children. Exposure to lead also results in anemia and hematopoietic disturbances. Additionally, lead is toxic to sperm and can alter endoc rine function in adults. Lead crosses the placenta and is accumulated in fetal organs, including the brain. Several studies have reported positive exposure-related associations between blood lead level and blood pressure in adult men and women. It was estim ated that the effects of lead exposure on blood pressure contribute signifi cantly to risks of hypertensive heart disease and stroke in the U.S. population. It is important to note that all these toxic effects of lead described in human populations have been observed in rode nt models at similar blood lead levels.

The mechanisms leading to the carcinogeni c effects of lead are not understood. Lead compounds do not appear to be directly genot oxic but may cause genetic damage through
several indirect mechanisms. These include inhibition of DNA synthesis and repair, oxidative damage, and interaction with DNA-binding proteins and tumor-suppressor proteins. Interference with DNA synthesis and repair has been suggested as one possible explanation for the genotoxic and co -mutagenic properties of lead.

It has been suggested that cel l proliferation may play a role in lead’s induction of renal cancer; however, the mechanisms have not b een established. Although exposure to lead also induces cell proliferation in the liver, the data suggest that the liver is not as susceptible as the kidneys to th e carcinogenicity of th is effect. No studies have associated liver tumors with lead exposure, and seve ral studies have show n that lead-induced proliferative mitogenesis does not promote the formation of liver foci or nodules from initiated hepatocytes, as observed during re generative mitogenesis. An association of renal adenocarcinoma with cystic nephropat hy has been suggested but is uncertain.05/08/03 RoC Background Document for Lead and Lead Compounds

16805/08/03 RoC Background Document for Lead and Lead Compounds

169 

## 7 References

1. ACGIH. 1999. TLVs and BEIs. American C onference of Governmental Industrial Hygienists, Cincinnati, Ohio. 44-45 pp.

2. Ades, A.E. and G. Kazantzis. 1988. Lung cancer in a non-ferrous smelter: the role
of cadmium. Br J Ind Med 45:435-442.

3. Al-Hakkak, Z.S., H.A. Hamamy, A.M. Murad, and A.F. Hussain. 1986.
Chromosome aberrations in workers at a storage battery plant in Iraq. Mutat Res
171:53-60.

4. Al-Saleh, I. and N. Shinwari. 2001. Levels of cadmium, lead, and mercury in
human brain tumors. Biol Trace Elem Res 79:197-203.

5. Anttila, A., P. Heikkila, E. Pukkala, E. Nykyri, T. Kauppinen, S. Hernberg, and K. Hemminki. 1995. Excess lung cancer among workers exposed to lead. Scand J
Work Environ Health 21:460-469.

6. Anttila, A., P. Heikkila, E. Nykyri, T. Kauppinen, E. Pukkala, S. Hernberg, and K. Hemminki. 1996. Risk of nervous system cancer among workers exposed to lead. J Occup Environ Med 38:131-136.

7. Ariza, M.E. and M.V. Williams. 1996. Mutagenesis of AS52 cells by low concentrations of lead(II) and mercury(II). Environ Mol Mutagen 27:30-33.

8. Ariza, M.E., G.N. Bijur, and M.V. Will iams. 1998. Lead and mercury mutagenesis: role of H2O2, superoxide dism utase, and xanthine oxidase. Environ Mol Mutagen
31:352-361.

9. Ariza, M.E. and M.V. Williams. 1999. Lead and mercury mutagenesis: type of mutation dependent upon metal concentration. J Biochem Mol Toxicol 13:107-112.

10. ATSDR. 1999. Toxicological Profile for Lead. U.S. DHHS, PHS, Agency for Toxic Substances and Disease Registry. Available at http://atsdr.cdc.gov/tfacts13.html.

11. Aufderheide, A.C. and L.E. Wittmers, Jr. 1992. Selected aspects of the spatial
distribution of lead in bone. Neurotoxicology 13:809-819.

12. Axelson, O. and K. Steenland. 1988. Indirect methods of assessing the effects of tobacco use in occupational studies. Am J Ind Med 13:105-118.

13. Baldwin, R.W., G.J. Cunningham, and D. Pratt. 1964. Carcinogenic action of motor engine oil additives. Br J Cancer 18:503-507.

14. Baló, J., A. Batjai, and B. Szende. 1965. Experimental adenomas of the kidney produced chronic administ ration of lead phosphate. Magyar Onkol 9:144-151.05/08/03 RoC Background Document for Lead and Lead Compounds

170 15. Barltrop, D. and F. Meek. 1975. Absorption of different lead compounds. Postgrad
Med J 51:805-809.

16. Barry, P.S. 1975. A comparison of concentr ations of lead in human tissues. Br J
Ind Med 32:119-139.

17. Bauchinger, M. and E. Schmid. 1972. [C hromosome analysis of cultures of
Chinese hamster cells after tr eatment with lead acetate]. Mutat Res 14:95-100.

18. Bauchinger, M., J. Dresp, E. Schm id, N. Englert, and C. Krause. 1977. Chromosome analyses of children after ecological lead exposure. Mutat Res 56:75-
80.

19. Bellinger, D.C., K.M. Stiles, and H.L. Needleman. 1992. Low-level lead exposure, intelligence and academic achieveme nt: a long- term follow-up study. Pediatrics
90:855-861.

20. Bertazzi, P.A. and C. Zocchetti. 1980. A mortality study of newspaper printing
workers. Am J Ind Med 1:85-97.

21. Beyer, W.N. and E.J. Cromartie. 1987. A survey of Pb, Cu, Zn, Cd, Cr, As, and Se
in earthworms and soil from diverse sites. Environ Monit Assess 8:27-36.

22. Bijlsma, J.B. and H.F. de France. 1976. Cytogenetic investigations in volunteers ingesting inorganic lead. Int Arch Occup Environ Health 38:145-148.

23. Bilban, M. 1998. Influence of the work environment in a Pb-Zn mine on the incidence of cytogenetic damage in miners. Am J Ind Med 34:455-463.

24. Birch, J., R.M. Harrison, and D.P. Laxen. 1980. Physicochemical speciation of lead in drinking water. Nature 286:791-793.

25. Blakley, B.R. 1987. The effect of lead on chemical- and viral-induced tumor production in mice. J Appl Toxicol7:167-172.

26. Blankenship, L.J., D.L. Carlisle, J.P. Wise , J.M. Orenstein, L.E. Dye, III, and S.R. Patierno. 1997. Induction of apoptotic cel l death by particulat e lead chromate:
differential effects of vitamins C and E on genotoxicity and survival. Toxicol Appl
Pharmacol 146:270-280.

27. Bogden, J.D., S.B. Gertner, F.W. Kemp, R. McLeod, K.S. Bruening, and H.R. Chung. 1991. Dietary lead and calcium: e ffects on blood pressure and renal neoplasia in Wistar rats. J Nutr 121:718-728.

28. Boudene, C., D. Malet, and R. Masse. 1977. Fate of 210 Pb inhaled by rats. Toxicol Appl Pharmacol 41:271-276.05/08/03 RoC Background Document for Lead and Lead Compounds

171 29. Bouton, C.M., M.A. Hossain, L.P. Freli n, J. Laterra, and J. Pevsner. 2001. Microarray analysis of di fferential gene expression in lead-exposed astrocytes. Toxicol Appl Pharmacol 176:34-53.

30. Boyland, E., C.E. Dukes, P.L. Grover, a nd B.C. Mitchley. 1962. The induction of renal tumours by feeding lead acetate to rats. Br J Cancer 16:283-288.

31. Bress, W.C. and J.H. Bidanset. 1991. Percut aneous in vivo and in vitro absorption
of lead. Vet Hum Toxicol 33:212-214.

32. Brown, R.S., B.E. Hingerty, J.C. De wan, and A. Klug. 1983. Pb(II)-catalysed cleavage of the sugar-phosphate backbone of yeast tRNAPhe--implications for lead toxicity and self-splicing RNA. Nature 303:543-546.

33. Bruce, W.R. and J.A. Heddle. 1979. The mutagenic activity of 61 agents as determined by the micronucleus, Salmonella, and sperm abnormality assays. Can J Genet Cytol 21:319-334.

34. Buchet, J.P., R. Lauwerys, H. Roels, and G. Hubermont. 1977. Mobilization of lead during pregnancy in rats. Int Arch Occup Environ Health 40:33-36.

35. Buckley, J.D., L.L. Robison, R. Swotinsky, D.H. Garabrant, M. LeBeau, P. Manchester, M.E. Nesbit, L. Odom , J.M. Peters, and W.G. Woods. 1989. Occupational exposures of parents of children with acute nonlymphocytic leukemia: a report from the Childrens Cancer Study Group. Cancer Res 49:4030-
4037.

36. Budavari, S., M.J. O'Neil, A. Smith, P.E. Heckelman, and J.F. Kinneary. 1996. The Merck Index. Budavari, S., M.J. O'Neil, A. Smith, P.E. Heckelman and J.F. Kinneary eds. Merck & Co., Inc., Whitehouse Station, NJ.

37. Cai, M.Y. and P. Arenaz. 1998. Antimutagenic effect of crown ethers on heavy metal-induced sister chromatid exchanges. Mutagenesis 13:27-32.

38. Cake, K.M., R.J. Bowins, C. Vaillancourt, C.L. Gordon, R.H. McNutt, R. Laporte, C.E. Webber, and D.R. Chettle. 1996. Parti tion of circulating lead between serum
and red cells is different for intern al and external sources of lead. Am J Ind Med
29:440-445.

39. Calabrese, E.J. and L.A. Baldwin. 1992. L ead-induced cell pro liferation and organspecific tumorigenicity. Drug Metab Rev 24:409-416.

40. Calsou, P. and B. Salles. 1994. Measurement of damage-specific DNA incision by nucleotide excision repair in vitro. Biochem Biophys Res Commun 202:788-795.

41. Calsou, P., P. Frit, C. Bozzato, and B. Salle s. 1996. Negative interference of metal (II) ions with nucleotide excision re pair in human cell-free extracts. Carcinogenesis
17:2779-2782.05/08/03 RoC Background Document for Lead and Lead Compounds

172 42. Capar, S.G. and E.J. Rigsby. 1989. Survey of lead in canned evaporated milk. J Assoc Off Anal Chem 72:416-417.

43. Carta, P., P. Cocco, and G. Picchiri. 1994. Lung cancer mortality and airways obstruction among metal miners exposed to silica and low levels of radon daughters. Am J Ind Med 25:489-506.

44. Casarett, L.J., C.D. Klaassen, M.O. Am dur, and J. Doull. 1996. Casarett and Doull's Toxicology : The Basic Science of Poisons Fifth Edition. Klaassen, C.D., M.O. Amdur and J. Doull eds. McGraw-Hill, New York, NY.

45. CDC. 1997. Update Blood Lead Levels-United States 1991-1994. Morbidity And Mortality Weekly Report 46:141-146.

46. CDC. 2002. Adult Blood Lead Epidemiology and Surveillance - United States,
1998-2001. Morbidity And Mortality Weekly Report 51:No. SS-11.

47. Chakraborti, D., W.R. De Jonghe, W.E. Van Mol, R.J. Van Cleuvenbergen, and
F.C. Adams. 1984. Determination of ioni c alkyllead compounds in water by gas chromatography/atomic absorption spectrometry. Anal Chem 56:2692-2697.

48. Chau, Y.K., P.T. Wong, G.A. Bengert, and O. Kramar. 1979. Determination of tetraalkyllead compounds in water, sediment, and fish samples. Anal Chem 51:186-
188.

49. Chem Sources. 2002. Chemical Sources International. Available at http://www.chemsources.com.

50. Chemfinder. 2000. Lead. CambridgeSo ft Corporation. Available at http://www.chemfinder.camsoft.com/.

51. Chia, K.S., J. Jeyaratnam, C. Tan, H.Y. Ong, C.N. Ong, and E. Lee. 1995.
Glomerular function of lead-exposed workers. Toxicol Lett 77:319-328.

52. Choie, D.D. and G.W. Richter. 1972. Lead poisoning: rapid formation of
intranuclear inclusions. Science 177:1194-1195.

53. Cocco, P., P. Carta, C. Flore, P. Congia, M.B. Manca, G. Saba, and S. Salis. 1996. Mortality of lead smelter workers wi th the glucose-6-phosphate dehydrogenasedeficient phenotype. Cancer Epidemiol Biomarkers Prev 5:223-225.

54. Cocco, P., F. Hua, P. Boffetta, P. Carta, C. Flore, V. Flore, A. Onnis, G.F. Picchiri, and D. Colin. 1997. Mortality of It alian lead smelter workers. Scand J Work
Environ Health 23:15-23.

55. Cocco, P., M. Dosemeci, and E.F. Heineman. 1998a. Brain cancer and occupational exposure to lead. J Occup Environ Med 40:937-942.05/08/03 RoC Background Document for Lead and Lead Compounds

173 56. Cocco, P., M. Dosemeci, and E.F. Heineman. 1998b. Occupational risk factors for cancer of the central nervous system: a cas e-control study on death certificates from

24 U.S. states. Am J Ind Med 33:247-255.

57. Cocco, P., M.H. Ward, and M. Dosemeci. 1999. Risk of stomach cancer associated with 12 workplace hazards: analysis of d eath certificates from 24 states of the United States with the aid of job exposure matrices. Occup Environ Med 56:781-
787.

58. Cocco, P.L., P. Carta, S. Belli, G.F. Picch iri, and M.V. Flore. 1994a. Mortality of
Sardinian lead and zinc miners: 1960-88. Occup Environ Med 51:674-682.

59. Cocco, P.L., P. Carta, V. Flore, G.F. Picchiri, and C. Zucca. 1994b. Lung cancer mortality among female mine workers exposed to silica. J Occup Med 36:894-898.

60. Columbano, A., G.M. Ledda, P. Sirigu, T. Perra, and P. Pani. 1983. Liver cell proliferation induced by a si ngle dose of lead nitrate. Am J Pathol 110:83-88.

61. Columbano, A., G.M. Ledda-Columbano, M.G. Ennas, M. Curto, A. Chelo, and P. Pani. 1990. Cell proliferation and promotion of rat liver carcinogenesis: different effect of hepatic regeneration and mit ogen induced hyperplasia on the development of enzyme-altered foci. Carcinogenesis 11:771-776.

62. Coni, P., G. Simbula, A.C. de Prati, M. Menegazzi, H. Suzuki, D.S. Sarma, G.M. Ledda-Columbano, and A. Columbano. 1993a . Differences in the steady-state levels of c-fos, c-jun and c-myc mess enger RNA during mitogen-induced liver growth and compensatory regeneration. Hepatology 17:1109-1116.

63. Coni, P., G. Pichiri-Coni, M. Curto, G. Si mbula, L. Giacomini, D.S. Sarma, G.M. Ledda-Columbano, and A. Columbano. 1993b. Di fferent effects of regenerative and direct mitogenic stimuli on the growth of initiated cells in the resistant hepatocyte model. Jpn J Cancer Res 84:501-507.

64. Cooper, W.C. and W.R. Gaffey. 197 5. Mortality of lead workers. J Occup Med
17:100-107.

65. Cooper, W.C., O. Wong, and L. Khei fets. 1985. Mortality among employees of lead battery plants and le ad-producing plants, 1947-1980. Scand J Work Environ
Health 11:331-345.

66. Cooper, W.C., O. Wong, and L. Trent. 1989. Case-control study of gastric cancer deaths in a lead battery plant. Report to the International Lead Zinc Research Organization.

67. Cordioli, G., L. Goughi, P.L. Solari, F. Berrino, P. Crosignani, and E. Riboli. 1987. Mortality from tumours in a cohort of workers in the glass industry. Epidemiol

Prev 30:16-18.05/08/03 RoC Background Document for Lead and Lead Compounds

174 68. Costa, M., O. Cantoni, M. de Mars, a nd D.E. Swartzendruber. 1982. Toxic metals produce an S-phase-specific cell cycle block. Res Commun Chem Pathol
Pharmacol 38:405-419.

69. Craig, P.J., J. Emsley, D.J. Faulkner, P.M. Huang, E.A. Paul, M. Schidlowski, W. Stumm, J.C.G. Walker, P.J. Wangersky, J. Westall, A.J.B. Zehnder, and S.H.
Zinder. 1980. The Natural Environment and the Biogeochemical Cycles. Hutzinger, O. ed. Springer-Verlag, New York. 185-197 pp.

70. CRC. 1998. Handbook of Chemistry and Physics. Lide, D.R. and H.P.R. Frederikse eds. CRC Press, New York, NY.

71. Daggett, D.A., T.D. Oberley, S.A. Nelson, L.S. Wright, S.E. Kornguth, and F.L. Siegel. 1998. Effects of lead on rat kidne y and liver: GST expression and oxidative

stress. Toxicology 128:191-206.

72. Dalpra, L., M.G. Tibiletti, G. Nocera, P. Giulotto, L. Auriti, V. Carnelli, and G. Simoni. 1983. SCE analysis in children e xposed to lead emission from a smelting plant. Mutat Res 120:249-256.

73. Dalton, C.B., J.B. McCammon, R.E. Ho ffman, and R.C. Baron. 1997. Blood lead levels in radiator repa ir workers in Colorado. J Occup Environ Med 39:58-62.

74. Davies, J.M. 1984a. Lung cancer mortality among workers making lead chromate and zinc chromate pigments at three English factories. Br J Ind Med 41:158-169.

75. Davies, J.M. 1984b. Long term mortality st udy of chromate pigment workers who suffered lead poisoning. Br J Ind Med 41:170-178.

76. Davis, R.K., A.W. Horton, E.E. Larson, and K.L. Stemmer. 1963. Inhalation of tetramethyllead and tetraethyllead. A comp arison of the effects in rats and dogs.
Arch Environ Health 6:473-479.

77. De Jonghe, W.R.A., D. Chakraborti, a nd F.C. Adams. 1981. Identification and determination of individual tetraalkyllead species in air. Environ Sci Technol
15:1217-1222.

78. Degawa, M., H. Arai, M. Kubota, and Y. Hashimoto. 1994. Ionic lead, a unique
metal ion as an inhibitor for cytochrome P450IA2 (CYP 1A2) expression in the rat
liver. Biochem Biophys Res Commun 200:1086-1092.

79. Deknudt, G., A. Colle, and G.B. Gerber. 1977. Chromosomal abnormalities in lymphocytes from monkeys poisoned with lead. Mutat Res 45:77-83.

80. Deknudt, G. and G.B. Gerber. 1979. Chro mosomal aberrations in bone-marrow cells of mice given a normal or a calcium-d eficient diet supplemented with various heavy metals. Mutat Res 68:163-168.05/08/03 RoC Background Document for Lead and Lead Compounds

175 81. Dev, V.G. and R. Tantravahi. 1982. Technique for chromosome analysis. In Techniques in Somatic Cell Genetics. Shaw , J.W., ed. Plenum Press, New York. pp. 506-508.

82. Dhir, H., A.K. Roy, and A. Sharma. 1993. Relative efficiency of Phyllanthus
emblica fruit extract and ascorbic acid in modifying lead and aluminium-induced sister-chromatid exchanges in mouse bone marrow. Environ Mol Mutagen 21:229-
236.

83. Dieter, M.P., H.B. Matthews, R.A. Jeffcoat, and R.F. Moseman. 1993. Comparison of lead bioavailability in F344 rats fed lead acetate, lead ox ide, lead sulfide, or lead ore concentrate from Skagway, Alaska. J Toxicol Environ Health 39:79-93.

84. Dietrich, K.N., M.D. Ris, P.A. Succop, O.G. Berger, and R.L. Bornschein. 2001. Early exposure to lead a nd juvenile delinquency. Neurotoxicol Teratol 23:511-518.

85. Dingwall-Fordyce, I. and R.E. Lane. 1963. A follow-up study of lead workers. Br J
Ind Med 20:213.

86. Donmez, H., N. Dursun, Y. Ozkul, and H. Demirtas. 1998. Increased sister chromatid exchanges in workers exposed to occupational lead and zinc. Biol Trace
Elem Res 61:105-109.

87. Dunkel, V.C., E. Zeiger, D. Brusick, E. McCoy, D. McGregor, K. Mortelmans, H.S. Rosenkranz, and V.F. Simm on. 1984. Reproducibility of microbial mutagenicity assays: I. Tests with Sa lmonella typhimurium and Escherichia coli using a standardized protocol. Environ Mutagen 6:1-251.

88. Eldred, R.A. and T.A. Cahill. 1994. Trends in elemental concentrations of fine particles at remote sites in the United States of America. Atmos Environ 28:1009-
1019.

89. Elias, Z., O. Poirot, H. Pezerat, H. Suquet, O. Schneider, M.C. Daniere, F. Terzetti, F. Baruthio, M. Fournier, and C. Cavelier. 1989. Cytotoxic and neoplastic transforming effects of industrial hexavalent chromium pigments in Syrian hamster embryo cells. Carcinogenesis 10:2043-2052.

90. Ellen, G. and J.W. Van Loon. 1990. Determin ation of cadmium and lead in foods by graphite furnace atomic absorption spectrometry with Zeeman background
correction: test with certified reference materials. Food Addit Contam 7:265-273.

91. Englyst, V., N.G. Lundström, L. Gerhar dsson, L. Rylander, and G. Nordberg. 2001. Lung cancer risks among lead smelter workers also exposed to arsenic. Sci Total

Environ 273:77-82.

92. EPA. 1989. Code of Federal Regulations, 40 CFR 141, 142.05/08/03 RoC Background Document for Lead and Lead Compounds

176 93. EPA. 1994. Methods for derivation of inha lation reference concentrations and application of inhalation dosimetr y. Environmental Protection Agency,
Environmental Criteria a nd Assessment Office, Res earch Triangle Park, NC.

94. EPA. 1996. National Air Quality and Emissions Trends Report, 1995. Environmental Protection Agency, Resear ch Triangle Park, NC. Available at http://www.epa.gov/oa r/aqtrnd95/report/.

95. EPA. 2000. National Toxics Inventory. U. S. Environmental Protection Agency. Available at http://www.epa.gov/ttn/chief/nti/.

96. EPA. 2002. The IEUBK Model. Revise d August 13, 2002. U.S. Environmental Protection Agency. Available at http://www.epa.gov/superfund/programs/lead/ieubk.htm.

97. Epstein, S.S. and N. Mantel. 1968. Carc inogenicity of tetraethyl lead. Experientia
24:580-581.

98. Erkkila, J., R. Armstrong, V. Riihimaki, D.R. Chettle, A. Paakkari, M. Scott, L. Somervaille, J. Starck, B. Kock, and A. Aitio. 1992. In vivo measurements of lead
in bone at four anatomical sites: l ong term occupational and consequent endogenous exposure. Br J Ind Med 49:631-644.

99. Evenson, D.P. 1990. Flow cytometric an alysis of male germ cell quality. Methods
Cell Biol 33:401-410.

100. Fabia, J. and T.D. Thuy. 1974. Occupation of father at time of birth of children dying of malignant diseases. Br J Prev Soc Med 28:98-100.

101. Fairhall, L.T. and J.W. Miller. 1941. A study of the relative toxicity of the molecular components of lead arsenate. Publ Health Rep (Wash) 56:1610-1625.

102. Fanning, D. 1988. A mortality study of lead workers, 1926-1985. Arch Environ
Health 43:247-251.

103. Fayerweather, W.E., M.E. Karns, I.A. Nuwayhid, and T.J. Nelson. 1997. Casecontrol study of cancer risk in tetraethyl lead manufacturing. Am J Ind Med 31:28-
35.

104. Fischer, A.B. and Y. Skreb. 2001. In v itro toxicology of h eavy metals using
mammalian cells: an overview of collaborative research data. Arh Hig Rada
Toksikol 52:333-354.

105. Fleming, D.E., D. Boulay, N.S. Richard, J.P. Robin, C.L. Gordon, C.E. Webber, and D.R. Chettle. 1997. Accumulated body bur den and endogenous release of lead in employees of a lead smelter. Environ Health Perspect 105:224-233.05/08/03 RoC Background Document for Lead and Lead Compounds

177 106. Fleming, D.E. 1998. Lead speciati on and occupational exposure. Environ Health Perspect 106:531.

107. Forni, A., G. Cambiaghi, and G.C. Secchi. 1976. Initial occupational exposure to lead: Chromosome and biochemical findings. Arch Environ Health 31:73-78.

108. Foster, W.G., A. McMahon, and D.C. Ri ce. 1996. Sperm chromatin structure is altered in cynomolgus monke ys with environmentally re levant blood lead levels.
Toxicol Ind Health 12:723-735.

109. Fowler, B.A. 1993. Mechanisms of kidney cell injury from metals. Environ Health Perspect 100:57-63.

110. Fracasso, M.E., L. Perbellini, S. Solda, G. Talamini, and P. Franceschetti. 2002. Lead induced DNA strand breaks in lymphoc ytes of exposed workers: role of reactive oxygen species a nd protein kinase C. Mutat Res 515:159-169.

111. Frenkel, G.D. and C. Middleton. 1987. Effects of lead acetate on DNA and RNA synthesis by intact HeLa cells, isol ated nuclei and purified polymerases. Biochem
Pharmacol 36:265-268.

112. Frisch, M. and B.S. Schwartz. 2002. The pitf alls of hair analysis for toxicants in clinical practice: three case reports. Environ Health Perspect 110:433-436.

113. Froines, J.R., S. Baron, D.H. Wegman, and S. O'Rourke. 1990. Characterization of
the airborne concentrations of lead in U.S. industry. Am J Ind Med 18:1-17.

114. Fu, H. and P. Boffetta. 1995. Cancer and occupational exposure to inorganic lead compounds: a meta- analysis of published data. Occup Environ Med 52:73-81.

115. Fukunaga, M., Y. Kurachi, and Y. Miz uguchi. 1982. Action of so me metal ions on yeast chromosomes. Chem Pharm Bull (Tokyo) 30:3017-3019.

116. Fullmer, C.S. 1997. Lead-calcium interactions: involvement of 1,25- dihydroxyvitamin D. Environ Res 72:45-55.

117. Furst, A., M. Schlauder, and D.P. Sa smore. 1976. Tumorigenic activity of lead
chromate. Cancer Res 36:1779-1783.

118. Gebhart, E. 1984. Chromosome damage in individuals exposed to heavy metals.
Toxicol Environ Chem 8:253-265.

119. Gerhardsson, L., N.G. Lundstrom, G. No rdberg, and S. Wall. 1986. Mortality and lead exposure: a retrospective cohor t study of Swedish smelter workers. Br J Ind
Med 43:707-712.05/08/03 RoC Background Document for Lead and Lead Compounds

178 120. Gerhardsson, L., D.R. Chettle, V. Englyst, G.F. Nordberg, H. Nyhlin, M.C. Scott, A.C. Todd, and O. Vesterberg. 1992. Kidne y effects in long term exposed lead
smelter workers. Br J Ind Med 49:186-192.

121. Gerhardsson, L., R. Attewell, D.R. Chettle, V. Englyst, N.G. Lundstrom, G.F. Nordberg, H. Nyhlin, M.C. Scott, and A.C. Todd. 1993. In vivo measurements of lead in bone in long-term e xposed lead smelter workers. Arch Environ Health
48:147-156.

122. Gerhardsson, L., L. Hagmar, L. Rylande r, and S. Skerfving. 1995a. Mortality and cancer incidence among secondary lead smelter workers. Occup Environ Med
52:667-672.

123. Gerhardsson, L., V. Englyst, N.G. Lunds tröm, G. Nordberg, S. Sandberg, and F.
Steinvall. 1995b. Lead in tissues of deceased lead smelter workers. J Trace Elem
Med Biol 9:136-143.

124. Gill, B.S. and S.S. Sandhu. 1992. Application of the Tradescantia micronucleus assay for the genetic evaluation of chemi cal mixtures in soil and aqueous media.

Mutat Res 270:65-69.

125. Giri, A.K., T.S. Banerjee, G. Talukder, and A. Sharma. 1987. Induction of sister chromatid exchange and dominant lethal mutation by "Katha" (Catechu) in male
mice. Cancer Lett 36:189-196.

126. Goldstein, D.H. J.M. Benoit, and H.A. Tyroler. 1970. An epidemiologic study of an oil mist exposure. Arch Environ Health 21:600-3.

127. Goyer, R.A. 1993. Lead toxicity: current concerns. Environ Health Perspect

100:177-187.

128. Grandjean, P., H.C. Wulf, and E. Niebuhr . 1983. Sister chromatid exchange in response to variations in occupational lead exposure. Environ Res 32:199-204.

129. Gulson, B.L. 1996. Tooth analyses of sources and intensity of lead exposure in
children. Environ Health Perspect 104:306-312.

130. Gulson, B.L., C.W. Jameson, K.R. Mahaffe y, K.J. Mizon, M.J. Korsch, and G. Vimpani. 1997. Pregnancy increases mobiliza tion of lead from maternal skeleton. J
Lab Clin Med 130:51-62.

131. Gulson, B.L., K.J. Mizon, J.M. Palmer, M.J. Korsch, N. Patison, C.W. Jameson, and J.B. Donnelly. 2000. Urinary lead is otopes during pregnancy and postpartum indicate no preferential partitioni ng of endogenous lead into plasma. J Lab Clin
Med 136:236-242.

132. Hainaut, P. and J. Milner. 1993. A structural role for metal ions in the "wild-type"
conformation of the tumo r suppressor protein p53. Cancer Res 53:1739-1742.05/08/03 RoC Background Document for Lead and Lead Compounds

179 133. Hainaut, P. and K. Mann. 2001. Zinc bi nding and redox control of p53 structure
and function. Antioxid Redox Signal 3:611-623.

134. Hakulinen, T., T. Salonen, and L. Teppo. 1976. Ca ncer in the offspring of fathers in hydrocarbon-related occupations. Br J Prev Soc Med 30:138-140.

135. Hammad, T.A., M. Sexton, and P. La ngenberg. 1996. Relationship between blood lead and dietary iron intake in presch ool children. A cross-sectional study. Ann Epidemiol 6:30-33.

136. Hamurcu, Z., H. Donmez, R. Saraymen, and H. Demirtas. 2001. Micronucleus frequencies in workers exposed to lead, zinc, and cadmium. Biol Trace Elem Res
83:97-102.

137. Hanas, J.S., J.S. Rodgers, J.A. Bantle, and Y.G. Cheng. 1999. Lead inhibition of DNA-binding mechanism of Cys(2)Hi s(2) zinc finger proteins. Mol Pharmacol
56:982-988.

138. Hartwig, A., R. Schlepegrell, and D. Beyersmann. 1990. Indirect mechanism of lead-induced genotoxicity in cultured mammalian cells. Mutat Res 241:75-82.

139. Hartwig, A. 1994. Role of DNA repair i nhibition in lead- and cadmium-induced genotoxicity: a review. Environ Health Perspect 102 Suppl 3:45-50.

140. Hartwig, A. 1995. Current aspe cts in metal genotoxicity. Biometals 8:3-11.

141. Hass, G.M., J.H. McDonald, R. Oyasu, H.A. Battifora, and J.T. Paloucek. 1967. Renal neoplasia induced by combinations of dietary lead subacetate and N-2- fluorenylacetamide. In Renal NeoPlasia. J.S. King Jr., ed. Little Brown Co., Boston. pp. 377-412.

142. Hermes-Lima, M., B. Pereira, and E.J. Bechara. 1991. Are free radicals involved in lead poisoning? Xenobiotica 21:1085-1090.

143. Hertz-Picciotto, I., A.H. Smith, D. Holtz man, M. Lipsett, and G. Alexeeff. 1992. Synergism between occupationa l arsenic exposure and smoki ng in the induction of lung cancer. Epidemiology 3:23-31.

144. Hertz-Picciotto, I. and J. Croft. 1993. Review of the relation between blood lead and blood pressure. Epidemiol Rev 15:352-373.

145. Hiasa, Y., M. Ohshima, Y. Kitahori, T. Fujita, T. Yuasa, and A. Miyashiro. 1983. Basic lead acetate: promoting effect on the development of renal tubular cell tumors in rats treated with N-ethyl-N- hydroxyethylnitrosamine. J Natl Cancer Inst
70:761-765.

146. Hoffman, D.J. and S.K. Niyogi. 1977. Metal mutagens and carcinogens affect RNA synthesis rates in a distinct manner. Science 198:513-514.05/08/03 RoC Background Document for Lead and Lead Compounds

180 147. Howe, H.E. 1981. Lead. In Kirk-Othmer Encyclopedia of Chemical Technology,

3 rd ed, Vol 14. Wiley and Sons, New York. pp. 98-139.

148. HSDB. 2002. Hazardous Substance Data Bank. National Library of Medicine. Available at http://toxnet.nlm.nih.gov/c gi-bin/sis/htmlgen?HSDB(& type: 7439-92- 1).

149. Hu, H., A. Aro, and A. Rotnitzky. 1 995. Bone lead measured by X-ray fluorescence: epidemiologic methods. Environ Health Perspect 103 Suppl 1:105-

110.

150. Hu, J., K.C. Johnson, Y. Mao, L. Guo, X. Zh ao, X. Jia, D. Bi, G. Huang, and R. Liu. 1998. Risk factors for glioma in a dults: a case-contro l study in northeast
China. Cancer Detect Prev 22:100-108.

151. Hu, J., J. Little, T. Xu, X. Zhao, L. G uo, X. Jia, G. Huang, D. Bi, and R. Liu. 1999. Risk factors for meningioma in adults: a case-control study in northeast China. Int J
Cancer 83:299-304.

152. Huang, X.P., Z.Y. Feng, W.L. Zhai, and J.H. Xu. 1988. Chromosomal aberrations and sister chromatid exchanges in workers exposed to lead. Biomed Environ Sci

1:382-387.

153. Hunter, D. 1978. The ancient metals. In The Diseases of Occupations, 6th ed. Hodder and Stroughton, Great Britain.

154. Hussain, T., I.H. Khan, and K.M. Ali. 1990. Study of environmental pollutants in and around the city of Lahore. I. Determ ination of lead in blood of various population groups. Sci Total Environ 99:137-143.

155. Hwua, Y.S. and J.L. Yang. 1998. Effect of 3-aminotriazole on anchorage independence and mutagenicity in cad. Carcinogenesis 19:881-888.

156. IARC. 1972. Monographs on the Evaluation of Carcinogenic Risks to Man - Some Inorganic Substances, Chlorinated Hydrocarbons, Aromatic Amines, N -Nitroso Compounds, and Natural Products, Vol. 1. World Health Organization, International Agency for Research on Cancer, Lyon, France. 40-50 pp.

157. IARC. 1973. IARC Monographs on the Evalua tion of Carcinogenic Risks to Man-- Some Inorganic and Organometallic Compounds, Vol. 2. World Health Organization, Internat ional Agency for Research on Cancer, Lyon, France. 150-160

pp.

158. IARC. 1976. IARC Monographs on the Evalua tion of Carcinogenic Risks to Man-- Some Carbamates, Thiocarbamates, a nd Carbazides, Vol. 12. World Health Organization, Intern ational Agency for Reasearch on Cancer, Lyon, France. 131- 135 pp.05/08/03 RoC Background Document for Lead and Lead Compounds

181 159. IARC. 1980. IARC Monographs on the Eval uation of Carcinogenic Risks to
Humans--Some Metals and Metallic Compounds, Vol. 23. World Health Organization, Internat ional Agency for Research on Cancer, Lyon, France. 325-415

pp.

160. IARC. 1987. IARC Monographs on the Eval uation of Carcinogenic Risks to Humans--Lead and Lead Compounds: Lead and Inorganic Lead Compounds (Group 2b) Organolead Compounds (Gr oup 3b), Supplement 7. World Health Organization, Internat ional Agency for Research on Cancer, Lyon, France. 230-232

pp.

161. IARC. 1990. IARC Monographs on the Eval uation of Carcinogenic Risks to Humans--Chromium, Nickel, and Weldi ng, Vol. 49. World Health Organization, International Agency for Research on Cancer, Lyon, France. 447-525 pp.

162. Ito, N., Y. Hiasa, Y. Kamakoto, S. Makiura, and S. Sugihara. 1971. Histopathological analysis of kidney tumors in rats induced by chemical carcinogens. Gann 62:435-444.

163. Ito, N. 1973. Experimental studies on tumors of the urinary system of rats induced by chemical carcinogens. Acta Pathol Jpn 23:87-109.

164. Jacquet, P., A. Leonard, and G.B. Gerb er. 1977. Cytogenetic i nvestigations on mice
treated with lead. J Toxicol Environ Health 2:619-624.

165. Jacquet, P. and P. Tachon. 1981. Effects of long-term lead exposure on monkey leukocyte chromosomes. Toxicol Lett 8:165-169.

166. Jagetia, G.C. and P.S. Jacob. 1992. Vinblas tine treatment induces dose-dependent increases in the frequency of micronuclei in mouse bone marrow. Mutat Res
280:87-92.

167. Jagetia, G.C. and R. Aruna. 1998. Effect of various concentrations of lead nitrate
on the induction of micronuclei in mouse bone marrow. Mutat Res 415:131-137.

168. Jecklin, L. 1956. Lead dust and lung cancer (Ger.). Schweiz Med Wschr 86:891-
892.

169. Jemal, A., B.I. Graubard, S.S. Devesa, and K.M. Flegal. 2002. The association of blood lead level and cancer mortality among whites in the United States. Environ Health Perspect 110:325-329.

170. Johnson, F.M. 1998. The genetic effects of environmental lead. Mutat Res 410:123-
140.

171. Kamel, F., D.M. Umbach, T.L. Munsat, J.M. Shefner, H. Hu, and D.P. Sandler. 2002. Lead exposure and amyotrophic lateral sclerosis. Epidemiology 13:311-319.05/08/03 RoC Background Document for Lead and Lead Compounds

182 172. Kandiloris, D.C., G.A. Goletsos, T.P. Ni kolopoulos, E.A. Ferekidis, A.S. Tsomis, and G.K. Adamopoulos. 1997. Effect of subc linical lead intoxication on laryngeal

cancer. Br J Clin Pract 51:69-70.

173. Kantor, A.F., M.G. Curnen, J.W. Meigs, and J.T. Flannery. 1979. Occupations of fathers of patients with Wilms's tumour. J Epidemiol Community Health 33:253-
256.

174. Kasprzak, K.S., K.L. Hoover, and L.A. Po irier. 1985. Effects of dietary calcium acetate on lead subacetate carcinogenicity in kidneys of male Sprague-Dawley rats. Carcinogenesis 6:279-282.

175. Kauppinen, T., R. Riala, J. Seitsamo, a nd S. Hernberg. 1992. Primary liver cancer and occupational exposure. Scand J Work Environ Health 18:18-25.

176. Kehoe, R.A. and F. Thamann. 1931. The behavi or of lead in the animal organism: II. Tetraethyl lead. Am J Hyg 13:478-498.

177. Kharab, P. and I. Singh. 1985. Genotoxic eff ects of potassium dichromate, sodium arsenite, cobalt chloride and lead nitrate in diploid yeast. Mutat Res 155:117-120.

178. Kim, R., H. Hu, A. Rotnitzky, D. Belli nger, and H. Needleman. 1996. Longitudinal relationship between dentin lead levels in childhood a nd bone lead levels in young
adulthood. Arch Environ Health 51:375-382.

179. Kinoshita, T., K. Tashiro, and T. Nakamura. 1989. Marked increase of HGF mRNA in nonparenchymal liver cells of rats treated with hepatotoxin. Biochem Biophys Res Commun 165:1229-1234.

180. Klein, C.B., K. Frenkel, and M. Costa. 1991. The role of oxidative processes in metal carcinogenesis. Chem Res Toxicol 4:592-604.

181. Kobayashi, N. and T. Okamoto. 1974. Eff ects of lead oxide on the induction of lung tumors in Syrian hamsters. J Natl Cancer Inst 52:1605-1610.

182. Koller, L.D., N.I. Kerkvliet, and J.H. Exon. 1985. Neoplasia induced in male rats fed lead acetate, ethyl urea, and sodium nitrite. Toxicol Pathol 13:50-57.

183. Kristensen, P. and A. Andersen. 199 2. A cohort study on cancer incidence in offspring of male printing workers. Epidemiology 3:6-10.

184. Kristensen, P., E. Eilertsen, E. Eina rsdottir, S. Ovrebo, and A. Haugen. 1993. Effect modification by inorganic l ead in the dominant lethal assay. Mutat Res
302:33-38.

185. Kroes, R., M.J. van Logten, J.M. Berkve ns, T. de Vries, and G.J. van Esch. 1974. Study on the carcinogenicity of lead arse nate and sodium arsenate and on the possible synergistic effect of diethylnitrosamine. Food Cosmet Toxicol 12:671-679.05/08/03 RoC Background Document for Lead and Lead Compounds

183 186. Krugner-Higby, L.A., A. Gendron, N.K. Laughlin, M. Luck, J. Scheffler, and B. Phillips. 2001. Chronic myelocytic leukemia in a juvenile rhesus macaque (Macaca mulatta). Contemp Top Lab Anim Sci 40:44-48.

187. Lanphear, B.P., T.D. Matte, J. Rogers, R.P. Clickner, B. Dietz, R.L. Bornschein, P. Succop, K.R. Mahaffey, S. Dixon, W. Galke, M. Rabinowitz, M. Farfel, C. Rohde, J. Schwartz, P. Ashley, and D.E. Jacobs. 1998. The contribution of leadcontaminated house dust and residential soil to children's blood lead levels. A pooled analysis of 12 epidemiologic studies. Environ Res 79:51-68.

188. LDA. 2002. Lead Information. Lead Deve lopment Associatio n International. Available at http://www.ldaint.org/information.htm.

189. Leal-Garza, C., R. Montes De Oca, R.M. Cerda-Flores, E. Garcia-Martinez, and R. Garza-Chapa. 1986. Frequency of sister chromatid exchanges (SCE) in lead exposed workers. Arch Invest Med 17:267-276.

190. Ledda-Columbano, G.M., P. Coni, M. Curto, L. Giacomini, G. Faa, D.S. Sarma, and A. Columbano. 1992. Mitogen-induced liver hyperplasia does not substitute for compensatory regeneration during promoti on of chemical hepatocarcinogenesis. Carcinogenesis 13:379-383.

191. Ledda-Columbano, G.M., A. Columbano, A. Cannas, G. Simbula, K. Okita, K. Kayano, Y. Kubo, S.L. Katyal, and H. Shinozuka. 1994. Dexamethasone inhibits induction of liver tumor necrosis factor-alpha mRNA and liver growth induced by lead nitrate and ethylene dibromide. Am J Pathol 145:951-958.

192. Lee, R.G., W.C. Becker, and D.W. Collin s. 1989. Lead at the Tap: Sources and
Control. Am Water Works Assoc J 81:52-62.

193. Leggett, R.W. 1993. An age-specific kinetic model of lead metabolism in humans. Environ Health Perspect 101:598-616.

194. Lerda, D. 1992. The effect of lead on Allium cepa L. Mutat Res 281:89-92.

195. Li, P. and T.G. Rossman. 2001. Genes upre gulated in lead-resistant glioma cells reveal possible targets for lead-i nduced developmental neurotoxicity. Toxicol Sci
64:90-99.

196. Liang, R., S. Senturker, X. Shi, W. Ba l, M. Dizdaroglu, and K.S. Kasprzak. 1999. Effects of Ni(II) and Cu(II) on DNA interact ion with the N-terminal sequence of human protamine P2: enhancement of binding and mediation of oxidative DNA strand scission and base damage. Carcinogenesis 20:893-898.

197. Lin, R.H., C.H. Lee, W.K. Chen, and S.Y. Lin-Shiau. 1994. Studies on cytotoxic and genotoxic effects of cadmium nitrate a nd lead nitrate in Chinese hamster ovary
cells. Environ Mol Mutagen 23:143-149.05/08/03 RoC Background Document for Lead and Lead Compounds

184 198. Lindroos, P.M., R. Zarnegar, and G.K. Michalopoulos. 1991. Hepatocyte growth factor (hepatopoietin A) ra pidly increases in plasma before DNA synthesis and liver regeneration stimulated by partia l hepatectomy and carbon tetrachloride
administration. Hepatology 13:743-750.

199. Loghman-Adham, M. 1997. Renal effects of environmental and occupational lead

exposure. Environ Health Perspect 105:928-939.

200. Lundström, N.G., G. Nordberg, V. Englyst, L. Gerhardsson, L. Hagmar, T. Jin, L. Rylander, and S. Wall. 1997. Cumulative lead exposure in relation to mortality and lung cancer morbidity in a cohort of primary smelter workers. Scand J Work
Environ Health 23:24-30.

201. Lustberg, M. and E.K. Silbergeld. 2002. Blood lead and mortality. Arch Intern Med
162:2443-2449.

202. Ma, T.H., V.A. Anderson, M.M. Harris, and J.L. Bare. 1983. TradescantiaMicronucleus (Trad-MCN) test on the genotoxicity of malathion. Environ Mutagen
5:127-137.

203. Ma, T.H., S.S. Sandhu, Y. Peng, T.D. Chen, and T.W. Kim. 1992. Synergistic and antagonistic effects on genotoxicity of chemicals commonly found in hazardous
waste sites. Mutat Res 270:71-77.

204. Ma, W.C. 1989. Effect of soil pollution with metallic lead pellets on lead bioaccumulation and organ/body weight alterations in small mammals. Arch
Environ Contam Toxicol 18:617-622.

205. Mahaffey, K.R. and J.L. Annest. 1986. Asso ciation of erythrocyte protoporphyrin
with blood lead level and ir on status in the second Na tional Health and Nutrition Examination Survey, 1976-1980. Environ Res 41:327-338.

206. Maki-Paakkanen, J., M. Sorsa, and H. Vainio. 1981. Chromosome aberrations and sister chromatid exchanges in lead-exposed workers. Hereditas 94:269-275.

207. Malcolm, D. and H.A. Barnett. 1982. A mortality study of lead workers 1925-76.
Br J Ind Med 39:404-410.

208. Mallin, K., M. Rubin, and E. Joo. 1989. O ccupational cancer mortality in Illinois white and black males, 1979- 1984, for seven cancer sites. Am J Ind Med 15:699-

717.

209. Manton, W.I., S.J. Rothenberg, and M. Manalo. 2001. The lead content of blood

serum. Environ Res 86:263-273.

210. Mao, P. and J.J. Molnar. 1967. The fine st ructure and histochemistry of leaninduced renal tumors in rats. Am J Pathol 50:571-603.05/08/03 RoC Background Document for Lead and Lead Compounds

185 211. Marcus, A.H. 1985. Multicompartment kinetic models for lead. I. Bone diffusion models for long-term retention. Environ Res 36:441-458.

212. Markowitz, M.E. and X.M. Shen. 2001. Assessment of bone lead during pregnancy: a pilot study. Environ Res 85:83-89.

213. Maslat, A.O. and H.J. Haas. 1989. Mutage nic effects of lead (II) bromide. J Trace Elem Electrolytes Health Dis 3:187-191.

214. McKhann, C. 1932. Lead poisoning in chil dren: the cerebral manifestations. Arch Neurol Psychiat 27:294-304.

215. McQuarrie, D.A. and P.A. Rock. 1984. General Chemistry. W. H. Freeman and Company, New York.

216. Merzenich, H., A. Hartwig, W. Ahrens, D. Beyersmann, R. Schlepegrell, M. Scholze, J. Timm, and K.H. Jockel. 2001. Biomonitoring on carcinogenic metals and oxidative DNA damage in a cross-sectional study. Cancer Epidemiol
Biomarkers Prev 10:515-522.

217. Michaels, D., S.R. Zoloth, and F.B. Stern. 1991. Does low-level lead exposure
increase risk of death? A mort ality study of newspaper printers. Int J Epidemiol
20:978-983.

218. Minissi, S., D. Caccese, F. Passafiume, A. Grella, C. Eleonora, and M. Rizzoni. 1998. Mutagenicity (micronucleus test in Vi cia faba root tips), polycyclic aromatic hydrocarbons and heavy metal content of sedi ments collected in Tiber river and its
tributaries within the urban area of Rome. Mutat Res 420:77-84.

219. Mirsky, A.E. and B. Silverman. 1972. Blocking by histones of accessibility to
DNA in chromatin. Proc Natl Acad Sci U S A 69:2115-2119.

220. Moore, J.F. and R.A. Goyer. 1974. Lead -induced inclusion bodies: composition and probable role in lead metabolism. Environ Health Perspect 7:121-127.

221. Morgan, A. and A. Holmes. 1978. The fate of lead in petrol-engine exhaust particulates inhaled by the rat. Environ Res 15:44-56.

222. Muro, L.A. and R.A. Goyer. 1969. Chromo some damage in experimental lead poisoning. Arch Pathol 87:660-663.

223. Nawrot, T.S., L. Thijs, E.M. Den Hond, H. A. Roels, and J.A. Staessen. 2002. An epidemiological re-appraisal of the asso ciation between blood pressure and blood lead: a meta-analysis. J Hum Hypertens 16:123-131.

224. Nayak, B.N., M. Ray, T.V. Persaud, and M. Nigli. 1989. Relationship of embryotoxicity to genotoxicity of lead nitrate in mice. Exp Pathol 36:65-73.05/08/03 RoC Background Document for Lead and Lead Compounds

186 225. Nehez, M., R. Lorencz, and I. Desi. 2000. Simultaneous action of cypermethrin and two environmental pollutant metals, cadmium and lead, on bone marrow cell
chromosomes of rats in subchronic administration. Ecotoxicol Environ Saf 45:55-
60.

226. Nesbitt, M.N. and U. Francke. 1973. A system of nomenclature for band patterns of
mouse chromosomes. Chromosoma 41:145-158.

227. Nestmann, E.R., T.I. Matula, G.R. Douglas, K.C. Bora, and D.J. Kowbel. 1979. Detection of the mutagenic activity of lead chromate using a battery of microbial

tests. Mutat Res 66:357-365.

228. NIOSH. 1977. Method No. P&CAM 102. In Ma nual of analytical methods, vol 1, 2nd ed. National Institute for Occupational Safety and Health, Cincinnati, Ohio.

229. NIOSH. 1997. Protecting Workers Exposed to Lead-based Paint Hazards A Report to Congress, DHHS (NIOSH) Publication No. 98-112. Department of Health and Human Services, Center for Di sease Control. Available at http://www.cdc.gov/niosh/tc98112.html.

230. NIOSH. 2001. Health Hazard Evaluations: Occupational Exposure to Lead 1994 to 1999. Department of Health and Human Serv ices, Centers for Disease Control and Prevention. Available at http ://www.cdc.gov/niosh/pdfs/2001-113.pdf.

231. Nishioka, H. 1975. Mutagenic activitie s of metal compounds in bacteria. Mutat Res
31:185-189.

232. Nordberg, G.F., R.A. Goyer, and T.W. Clarkson. 1985. Impact of effects of acid precipitation on toxicity of metals. Environ Health Perspect 63:169-180.

233. Nordenson, I., G. Beckman, L. Beckman, and S. Nordstrom. 1978. Occupational
and environmental risks in and around a smelter in northern Sweden. IV. Chromosomal aberrations in workers exposed to lead. Hereditas 88:263-267.

234. NRC. 1993. Measuring lead exposure in in fants, children, and other sensitive populations. National Research Council, National Academy Press. Available at (http://books.nap.edu/books /030904927X/html/R15.html).

235. NSF. 1977. Physical and chemical characterist ics of environmental lead. In Lead in
the Environment. National Science Foundation

236. NTP. 2000. 9th Report on Carcinogens. U.S. Department of Health and Human Services, Public Health Service, Na tional Toxicology Program. Available at http://ehis.niehs.nih.gov/roc.

237. Oberley, T.D., A.L. Friedman, R. Moser, and F.L. Siegel. 1995. Effects of lead administration on developing rat kidne y. II. Functional, morphologic, and
immunohistochemical studies. Toxicol Appl Pharmacol 131:94-107.05/08/03 RoC Background Document for Lead and Lead Compounds

187 238. O'Flaherty, E.J. 1993. Physiologically base d models for bone-seeking elements. IV. Kinetics of lead disposition in humans. Toxicol Appl Pharmacol 118:16-29.

239. O'Flaherty, E.J. 1995. Physiologically base d models for bone-seeking elements. V. Lead absorption and disposition in childhood. Toxicol Appl Pharmacol 131:297-
308.

240. O'Halloran, T.V. 1993. Transition metals in control of gene expression. Science
261:715-725.

241. Olshan, A.F., N.E. Breslow, J.R. Dali ng, J.M. Falletta, S. Grufferman, L.L. Robison, M. Waskerwitz, and G.D. Ha mmond. 1990. Wilms' tumor and paternal occupation. Cancer Res 50:3212-3217.

242. O'Riordan, M.L. and H.J. Evans. 1974. Absence of significant chromosome damage in males occupationally exposed to lead. Nature 247:50-53.

243. OSHA. 2002. Employee Standard Summary - 1910.1025 App B. U.S. Department of Labor, Occupational Health & Sa fety Adminstration. Available at http://www.osha.gov/pls/oshaweb/owad isp.show_document?p_table=STANDARD S&p_id=10032.

244. Oyasu, R., H.A. Battifora, R.A. Clasen, J.H. McDonald, and G.M. Hass. 1970. Induction of cerebral gliomas in rats with dietary lead subacetate and 2- acetylaminofluorene. Cancer Res 30:1248-1261.

245. Parry, C. and J. Eaton. 1991. Kohl: a lead-hazardous eye makeup from the Third
World to the First World. Environ Health Perspect 94:121-123.

246. Patierno, S.R., D. Banh, and J.R. La ndolph. 1988. Transformation of C3H/10T1/2 mouse embryo cells to focus formation and anchorage independence by insoluble lead chromate but not soluble calcium chromate: relationship to mutagenesis and internalization of lead chromate particles. Cancer Res 48:5280-5288.

247. Patierno, S.R. and J.R. Landolph. 1989. Solubl e vs insoluble hexavalent chromate. Relationship of mutation to in vitro transformation and particle uptake. Biol Trace
Elem Res 21:469-474.

248. Patterson, C., J. Ericson, M. Manea-Kr ichten, and H. Shirahata. 1991. Natural
skeletal levels of lead in Homo sapiens sapiens uncontaminated by technological
lead. Sci Total Environ 107:205-236.

249. Perry, P. and S. Wolff. 1974. New Giemsa method for the differential staining of
sister chromatids. Nature 251:156-158.

250. Pesch, B., J. Haerting, U. Ranft, A. Klim pel, B. Oelschlagel, W. Schill, and MURC Study Group. 2000. Occupational risk factors for renal cell carcinoma:05/08/03 RoC Background Document for Lead and Lead Compounds

188 agent-specific results from a case-control study in Germany. Int J Epidemiol
29:1014-1024.

251. Petering, D.H., M. Huang, S. Moteki, and C.F. Shaw, 3rd. 2000. Cadmium and lead
interactions with transcri ption factor IIIA from Xenopus laevis: a model for zinc finger protein reactions with toxi c metal ions and metallothionein. Mar Environ

Res 50:89-92.

252. Poirier, L.A., J.C. Theiss, L.J. Ar nold, and M.B. Shimkin. 1984. Inhibition by magnesium and calcium acetates of lead subacetate- and nickel acetate-induced lung tumors in strain A mice. Cancer Res 44:1520-1522.

253. Pounds, J.G., G.J. Long, and J.F. Rosen. 1991. Cellular and molecular toxicity of
lead in bone. Environ Health Perspect 91:17-32.

254. Quintanilla-Vega, B., D.J. Hoover, W. Ba l, E.K. Silbergeld, M.P. Waalkes, and
L.D. Anderson. 2000. Lead interaction with human protamine (HP2) as a mechanism of male reproductive toxicity. Chem Res Toxicol 13:594-600.

255. Rabinowitz, M.B., G.W. Wetherill, and J.D. Kopple. 1976. Kinetic analysis of lead metabolism in healthy humans. J Clin Invest 58:260-270.

256. Rajah, T. and Y.R. Ahuja. 1995. In vivo genotoxic effects of smoking and occupational lead exposure in printing press workers. Toxicol Lett 76:71-75.

257. Ramel, C. and J. Magnusson. 1979. Chem ical induction of nondisjunction in drosophila. Environ Health Perspect 31:59-66.

258. Razmiafshari, M., J. Kao, A. d'Avignon, and N.H. Zawia. 2001. NMR identification of heavy metal-binding site s in a synthetic zinc finger peptide: toxicological implications fo r the interactions of xenobiot ic metals with zinc finger proteins. Toxicol Appl Pharmacol 172:1-10.

259. Reddy, T. P. and K. Vaidyanath. 1978. Syne rgistic interaction of gamma-rays and
some metallic salts in the induction of chlorophyll mutations in rice. Mutat Res 52:
361-365.

260. Rencher, A.C., M.W. Carter, and D.W. McKee. 1977. A retrospective epidemiological study of mortality at a large western copper smelter. J Occup Med
19:754-758.

261. Restrepo, H.G., D. Sicard, and M.M. Torres. 2000. DNA damage and repair in cells of lead exposed people. Am J Ind Med 38:330-334.

262. Reynolds, S.J., R. Seem, L.J. Fourtes, N.L. Sprince, J. Johnson, L. Walkner, W. Clarke, and P. Whitten. 1999. Prevalence of elevated blood leads and exposure to
lead in construction trades in Iowa and Illinois. Am J Ind Med 36:307-316.05/08/03 RoC Background Document for Lead and Lead Compounds

189 263. Risch, H.A., J.D. Burch, A.B. Miller, G.B. Hill, R. Steele, and G.R. Howe. 1988. Occupational factors and the incidence of cancer of the bladder in Canada. Br J Ind
Med 45:361-367.

264. Ritchie, J.M., M. Cresser, and J. Cott er-Howells. 2001. Toxicol ogical response of a bioluminescent microbial assay to Zn, Pb and Cu in an artificial soil solution: relationship with total metal con centrations and free ion activities. Environ Pollut
114:129-136.

265. Robbiano, L., R. Carrozzino, C.P. Puglia, C. Corbu, and G. Brambilla. 1999. Correlation between induction of DNA frag mentation and micronuclei formation in kidney cells from rats and humans and tissue-specific carcinogenic activity. Toxicol Appl Pharmacol 161:153-159.

266. Roberts, F.J., L. Ebdon, and S.J. Hill. 2000. A preliminary clin ical investigation into the potential of blood lead levels to measure bone resorption in patients with skeletal metastases, using ICP-MS. J Trace Elem Med Biol 14:108-115.

267. Robinson, T.R. 1976. The health of long service tetraethyl lead workers. J Occup
Med 18:31-40.

268. Robison, S.H., O. Cantoni, and M. Co sta. 1984. Analysis of metal-induced DNA lesions and DNA-repair repli cation in mammalian cells. Mutat Res 131:173-181.

269. Roe, F.J., E. Boyland, C.E. Dukes, and B. C. Mitchley. 1965. Failure of testosterone or xanthopterin to influen ce the induction of renal ne oplasms by lead in rats. Br J
Cancer 19:860-866.

270. Rosenblum, W.I. and M.G. Johnson. 1968. Ne uropathologic changes produced in suckling mice by adding lead to the maternal diet. Arch Pathol 85:640-648.

271. Rosman, K.J.R., W. Chisholm, C.F. B outron, J.P. Candelone, and S. Hong. 1994a. Isotopic evidence to account for changes in the concentration of lead in Greenland
snow between 1960 and 1988. Geochimica Et Cosmochimica Acta 58:3265-3269.

272. Rosman, K.J.R., W. Chisholm, C.F. Bout ron, J.P. Candelone, and C.C. Patterson. 1994b. Anthropogenic lead isotopes in Antarctica. Geophys Res Lett 21:2669-2672.

273. Roy, N.K. and T.G. Rossman. 1992. Mutagenesis and comutagenesis by lead compounds. Mutat Res 298:97-103.

274. Rudnick, R.L. and D.M. Fountain. 1995. Nature and composition of the continental-crust - a lower crustal perspective. Rev Geophys 33:267-309.

275. Sallmen, M. 2001. Exposure to lead and male fertility. Int J Occup Med Environ
Health 14:219-222.05/08/03 RoC Background Document for Lead and Lead Compounds

190 276. Sandhu, S.S., T.H. Ma, Y. Peng, and X.D. Zhou. 1989. Clastogenicity evaluation of seven chemicals commonly found at hazardous industrial waste sites. Mutat Res
224:437-445.

277. Sankila, R., S. Karjalainen, E. Pukkala, H. Oksanen, T. Hakulinen, L. Teppo, and M. Hakama. 1990. Cancer risk among gla ss factory workers: an excess of lung

cancer? Br J Ind Med 47:815-818.

278. Sarto, F., M. Stella, and A. Acqua. 1978. [C ytogenetic study of a group of workers with increased lead absorption indices]. Med Lav 69:172-180.

279. Saryan, L.A. and C. Zenz. 1994. Lead and its compounds. In Occupational Medicine. Zenz, C., B. Dickerson and E.P. Horvath, eds. Mosby, St. Louis.

280. Satzger, R.D., C.S. Clow, E. Bonnin, a nd F.L. Fricke. 1982. Determination of background levels of lead and cadmium in raw agricultural crops by using differential pulse anodic stripping voltammetry. J Assoc Off Anal Chem 65:987-
991.

281. Schechtman, L.M., G.G. Hatch, T.M. Anderson, D.L. Putman, R.E. Kouri, J.W. Cameron, R.W. Nims, J.W. Spalding, R. W. Tennant, and R.A. Lubet. 1986. Analysis of the interlaboratory and intralaboratory reproducibility of the enhancement of simian adenovirus SA7 transformation of Syrian hamster embryo cells by model carcinogenic and noncarcinogenic compounds. Environ Mutagen
8:495-514.

282. Schmid, E., M. Bauchinger, S. Pietruc k, and G. Hall. 1972. [Cytogenetic action of lead in human peripheral lymphocytes in vitro and in vivo]. Mutat Res 16:401-406.

283. Schmitt, M.D., D.L. Trippler, J.N. W achtler, and G.V. Lund. 1988. Soil lead
concentrations in residential Minne sota USA as measured by ICP AES. Water Air
Soil Pollut 39:157-168.

284. Schneider, E.L., R.R. Tice, and D. Kram. 1978. Bromodeoxyuridine differential chromatid staining: a new approach to ex amining sister chromatid exchange and cell replication kinetics. In Methods in Cell Biology. Prescott, D.M., ed. Academic Press, NY. pp. 379-409.

285. Schroeder, H.A., M. Mitchener, and A.P. Nason. 1970. Zirconium, niobium, antimony, vanadium and lead in rats: life term studies. J Nutr 100:59-68.

286. Schütz, A., I.A. Bergdahl, A. Ekholm, and S. Skerfving. 1996. Measurement by ICP-MS of lead in plasma and whol e blood of lead workers and controls. Occup
Environ Med 53:736-740.

287. Schwanitz, G., G. Lehnert, and E. Ge bhart. 1970. [Chromosome damage after occupational exposure to lead]. Dtsch Med Wochenschr 95:1636-1641.05/08/03 RoC Background Document for Lead and Lead Compounds

191 288. Schwanitz, G., E. Gebhart, H.D. Rott, K.H. Schaller, H.G. Essing, O. Lauer, and H. Prestele. 1975. [Chromosome investigations in subjects with occupational lead exposure (author's trans)]. Dtsch Med Wochenschr 100:1007-1011.

289. Schwartz, B.S., B.K. Lee, G.S. Lee, W.F. Stewart, D. Simon, K. Kelsey, and A.C. Todd. 2000. Associations of blood lead, dime rcaptosuccinic acid-chelatable lead, and tibia lead with polymorphisms in the vitamin D receptor and [delta]- aminolevulinic acid dehydratase genes. Environ Health Perspect 108:949-954.

290. Schwartz, J., P.J. Landrigan, R.G. Feldma n, E.K. Silbergeld, E.L. Baker, Jr., and
I.H. von Lindern. 1988. Threshold effect in lead-induced peripheral neuropathy. J
Pediatr 112:12-17.

291. Searles, M.A., D. Lu, and A. Klug. 2000. The role of the central zinc fingers of transcription factor IIIA in binding to 5 S RNA. J Mol Biol 301:47-60.

292. Selevan, S.G., P.J. Landrigan, F.B. Stern, and J.H. Jones. 1985. Mortality of lead
smelter workers. Am J Epidemiol 122:673-683.

293. Shakerin, M. and J. Paloucek. 1965. Intranucle ar inclusions and renal tumors in rats
fed lead subacetate. Lab Invest 14:592.

294. Shakerin, M., J. Paloucek, R. Oyasu, and G.M. Hass. 1965. Carcinogenesis in rats due to dietary 2AAF and lead subacetate. Fed Proc 24:684.

295. Sharief, Y., A.M. Brown, L.C. Backer, J.A. Campbell, B. Westbrook-Collins, A.G. Stead, and J.W. Allen. 1986. Sister ch romatid exchange and chromosome aberration analyses in mice after in vivo exposure to acrylonitrile, styrene, or
butadiene monoxide. Environ Mutagen 8:439-448.

296. Sheffet, A., I. Thind, A.M. Miller, and D.B. Louria. 1982. Cancer mortality in a pigment plant utilizing lead and zinc chromates. Arch Environ Health 37:44-52.

297. Shimkin, M.B., G.D. Stoner, and J.C. Theiss. 1977. Lung tumor response in mice
to metals and metal salts. Adv Exp Med Biol 91:85-91:85-91.

298. Shukla, V.K., A. Prakash, B.D. Tripathi, D.C.S. Reddy, and S. Singh. 1998. Biliary heavy metal concentrations in carcinoma of the gall bladder: case-control study.

BMJ 317:1288-1289.

299. Sidhu, M.K., C. Fernandez, M.Y. Khan, and S. Kumar. 1991. Induction of morphological transformation, anchorage- independent growth and plasminogen activators in non-tumorigenic human os teosarcoma cells by lead chromate.

Anticancer Res 11:1045-1053.

300. Siemiatycki, J., S. Wacholder, R. Dewar, E. Cardis, C. Greenwood, and L. Richardson. 1988. Degree of confounding bias related to smok ing, ethnic group,05/08/03 RoC Background Document for Lead and Lead Compounds

192 and socioeconomic status in estimates of the associations between occupation and

cancer. J Occup Med 30:617-625.

301. Siemiatycki, J., M. Gerin, R. Dewar, L. Nadon, R. Lakhani, D. Begin, and L.
Richardson. 1991. Associations between o ccupational circumstances and cancer. Siemiatycki, J. ed. CRC Press, Boca Raton. 141-145 pp.

302. Silbergeld, E.K. 1987. Role of altered heme synthesis in chemical injury to the
nervous system. Ann N Y Acad Sci 514:297-308.

303. Silbergeld, E.K., J. Schwartz, and K. Mahaffey. 1988. Lead and osteoporosis: mobilization of lead from bone in postmenopausal women. Environ Res 47:79-94.

304. Silbergeld, E.K., J. Sauk, M. Somerman, A. Todd, F. McNeill, B. Fowler, A. Fontaine, and J. van Buren. 1993. Lead in bone: storage site, exposure source, and
target organ. Neurotoxicology 14:225-236.

305. Silbergeld, E.K. 1997. Preventing lead poisoning in children. Annu Rev Public
Health 18:187-210.

306. Silbergeld, E.K., M. Waalkes, and J. M. Rice. 2000. Lead as a carcinogen: experimental evidence a nd mechanisms of action. Am J Ind Med 38:316-323.

307. Simmon, V.F. 1979a. In vitro assays for recombinogenic activity of chemical carcinogens and related compounds with Saccharomyces cerevisiae D3. J Natl

Cancer Inst 62:901-909.

308. Simmon, V.F., H.S. Rosenkranz, E. Zeig er, and L.A. Poirier. 1979b. Mutagenic activity of chemical carcinogens and rela ted compounds in the intraperitoneal hostmediated assay. J Natl Cancer Inst 62:911-918.

309. Sirover, M.A. and L.A. Loeb. 1976. Infideli ty of DNA synthesis in vitro: screening for potential metal mutagens or carcinogens. Science 194:1434-1436.

310. Sissoeff, I., J. Grisvard, and E. Guille. 1976. Studies on metal ions-DNA interactions: specific behaviour of reiterative DNA sequences. Prog Biophys Mol
Biol 31:165-199.

311. Skreb, Y. and V. Habazin-Novak. 1977. Lead induced modifications of the response to X-rays in human cells in culture. Stud Biophys 63:97-104.

312. Smirnov, I. and R.H. Shafer. 2000. Lead is unusually effective in sequence-specific folding of DNA. J Mol Biol296:1-5.

313. Smith, D., M. Hernandez-Avila, M.M. Tellez-Rojo, A. Mercado, and H. Hu. 2002. The relationship between lead in plasma and whol e blood in women. Environ Health Perspect 110:263-268.05/08/03 RoC Background Document for Lead and Lead Compounds

193 314. Smith, G.R. 1995. Lead. U.S. Geological Su rvey Minerals Yearbook. Available at http://minerals.usgs.gov/min erals/pubs/commodity/lead/ and select Minerals
Yearbook 2000.

315. Smith, G.R. 2000. Lead. U.S. Geological Su rvey Minerals Yearbook. Available at http://minerals.usgs.gov/min erals/pubs/commodity/lead/ and select Minerals
Yearbook 2000.

316. Smith, G.R. 2002a. Lead Statis tics and Information. U.S. Geological Survey, U.S. Department of the Interior. Available at http://minerals.usgs.gov/minerals/pu bs/commodity/ and select lead.

317. Smith, G.R. 2002b. Lead. U.S. Geological Survey, Mineral Commodity Summary. Available at http://miner als.usgs.gov/minerals/pubs/c ommodity/lead/ and select Mineral Commodity Summaries 2002.

318. Snyder, R.D., G.F. Davis, and P.J. L achmann. 1989. Inhibition by metals of X-ray and ultraviolet-induced DNA repair in human cells. Biol Trace Elem Res 21:389-
398.

319. Spear, T.M., W. Svee, J.H. Vincent, and N. Stanisich. 1998. Chemical speciation of lead dust associated with primary lead smelting. Environ Health Perspect 106:565-
571.

320. Stauber, J.L., T.M. Florence, B.L. Gulson, and L.S. Dale. 1994. Percutaneous absorption of inorganic lead compounds. Sci Total Environ 145:55-70.

321. Staudinger, K.C. and V.S. Rot h. 1998. Occupational lead poisoning. Am Fam Physician 57:719-726, 731-712.

322. Steenland, K., S. Selevan, and P. Landriga n. 1992. The mortality of lead smelter workers: an update. Am J Public Health 82:1641-1644.

323. Steenland, K., D. Loomis, C. Shy, and N. Simonsen. 1996. Review of occupational lung carcinogens. Am J Ind Med 29:474-490.

324. Steenland, K. and P. Boffetta. 2000. Lead a nd cancer in humans: where are we

now? Am J Ind Med 38:295-299.

325. Stewart, W.F., B.S. Schwartz, D. Simon, K. Kelsey, and A.C. Todd. 2002. ApoE genotype, past adult lead exposur e, and neurobehavioral function. Environ Health Perspect 110:501-505.

326. Stoner, G.D., M.B. Shimkin, M.C. Troxell, T.L. Thompson, and L.S. Terry. 1976. Test for carcinogenicity of metallic co mpounds by the pulmonary tumor response
in strain A mice. Cancer Res 36:1744-1747.05/08/03 RoC Background Document for Lead and Lead Compounds

194 327. Sunderman, F.W., Jr. and A.M. Barber. 1988. Finger-loops, oncogenes, and metals.
Claude Passmore Brown memorial lecture. Ann Clin Lab Sci 18:267-288.

328. Suzuki, T., S. Morimura, M.B. Diccianni, R. Yamada, S. Hochi, M. Hirabayashi, A. Yuki, K. Nomura, T. Kitagawa, M. Imagawa, and M. Muramatsu. 1996. Activation of glutathione tran sferase P gene by lead requi res glutathione transferase
P enhancer I. J Biol Chem 271:1626-1632.

329. Sweeney, M.H., J.J. Beaumont, R.J. Wa xweiler, and W.E. Halperin. 1986. An investigation of mortalit y from cancer and other causes of death among workers employed at an east Texas chemical plant. Arch Environ Health 41:23-28.

330. Tachi, K., S. Nishimae, and K. Saito. 1985. Cytogenetic effects of lead acetate on
rat bone marrow cells. Arch Environ Health 40:144-147.

331. Tanner, D.C. and M.M. Lipsky. 1984. Effect of lead acetate on N-(4'-fluoro-4- biphenyl)acetamide-induced renal carcinogenesis in the rat. Carcinogenesis
5:1109-1113.

332. Tassler, P.L., B.S. Schwartz, J. Core sh, W.F. Stewart, and A.C. Todd. 2001. Associations of tibia lead, DMSA-chelatable lead, and bl ood lead with measures of peripheral nervous system function in fo rmer organolead manufacturing workers.
Am J Ind Med 39:254-261.

333. Taylor, S.R. and S.M. McLennan. 1995. The geochemical evolution of the
continental-crust. Rev Geophys 33:241-265.

334. Telisman, S., P. Cvitkovic, J. Jurasovic, A. Pizent, M. Gavella, and B. Rocic. 2000. Semen quality and reproductive endocrine f unction in relation to biomarkers of lead, cadmium, zinc, and copper in men. Environ Health Perspect 108:45-53.

335. Tharr, D. and Ed. 1993. Lead contamin ation in radiator repair shops. App Occup Environ Hyg 8:434-438.

336. Todd, A.C. and D.R. Chettle. 1994. In vivo X-ray fluorescence of lead in bone:
review and current issues. Environ Health Perspect 102:172-177.

337. Todd, A.C., S. Carroll, J.H. Godbold, E.L. Moshier, and F.A. Khan. 2000. Variability in XRF-measured tibia lead levels. Phys Med Biol 45:3737-3748.

338. TRI99. 2001. Data contained in the Toxic Chemical Release Inventory (TRI). Available from the U.S. Environmental Protection Agency Office of
Environmental Information. Available at http://www.epa.gov/triexplorer/chemical.htm.

339. Tripathi, R.K., P.C. Sherertz, G.C. Ll ewellyn, C.W. Armstrong, and S.L. Ramsey. 1990. Reducing exposures to airborne lead in a covered, outdoor firing range by using totally copper-jacketed bullets. Am Ind Hyg Assoc J 51:28-31.05/08/03 RoC Background Document for Lead and Lead Compounds

195 340. Tsaih, S.W., J. Schwartz, M.L. Lee, C. Amarasiriwardena, A. Aro, D. Sparrow, and H. Hu. 1999. The independent contribution of bone and erythrocyt e lead to urinary lead among middle-aged and elderly men: the normative aging study. Environ Health Perspect 107:391-396.

341. UNEP-UNICEF. 1997. Childhood lead poisoning: information for advocacy and action. United Nations Environment Progr amme and United Nations Children's
Fund. Available at http://www.chem.unep.ch/irptc/pub lications/leadpoison/lead_eng.pdf.

342. Vaglenov, A., E. Carbonell, and R. Ma rcos. 1998. Biomonitoring of workers exposed to lead. Genotoxic effects, it s modulation by polyvitamin treatment and
evaluation of the induced radioresistance. Mutat Res 418:79-92.

343. Vaglenov, A., A. Creus, S. Laltchev, V. Petkova, S. Pavlova, and R. Marcos. 2001. Occupational exposure to lead a nd induction of genetic damage. Environ Health Perspect 109:295-298.

344. Vaglenov, A.K., S.G. Laltchev, M.S. Nos ko, S.P. Pavlova, V.V. Petkova, and A.D. Karadjov. 1997. Cytogenic monitoring of workers exposed to lead. Central Eur J Occupat Environ Med 3:298-308.

345. Vainio, H. 1997. Lead and cancer --association or causation? Scand J Work Environ
Health 23:1-3.

346. Valverde, M., T.I. Fortoul, F. Díaz-Barriga, J. Mejía, and E.R. del Castillo. 2002. Genotoxicity induced in CD-1 mice by inha led lead: differentia l organ response. Mutagenesis 17:55-61.

347. van Esch, G.J., H. Van Genderen, and H.H. Vink. 1962. The induction of renal tumours by feeding basic lead acetate to mice and hamsters. Br J Cancer 16:765-

771.

348. van Esch, G.J. and R. Kroes. 1969. The induc tion of renal tumours by feeding basic
lead acetate to mice and hamsters. Br J Cancer 23:765-771.

349. Vicente-Ortega, V., A.F. Martinez-Garcia, A. Cremades-Campos, J. RodriguezVicente, F. Calderon-Rubiales, and F. Martinez-Diaz. 1996. Ultrastructural investigation of lead-induced intr anuclear inclusion bodies in mice. Ultrastruct
Pathol 20:263-273.

350. Völkening, J., H. Baumann, and K.G. He umann. 1988. Atmospheric distribution of particulate lead over the Atlantic ocean from Europe to Antarctica. Atmos Environ
22:1169-1174.

351. Waalkes, M.P., B.A. Diwan, J.M. Ward, D.E. Devor, and R.A. Goyer. 1995. Renal tubular tumors and atypical hyperplasias in B6C3F1 mice exposed to lead acetate05/08/03 RoC Background Document for Lead and Lead Compounds

196 during gestation and lactation occu r with minimal chronic nephropathy. Cancer Res
55:5265-5271.

352. WebElements. 2000. Available at http://www.webelements.com/webelements/scholar/index.html.

353. Wedeen, R.P. 1997. Occupational and environmental renal disease. Semin Nephrol
17:46-53.

354. Wedrychowski, A., W.N. Schmidt, and L.S. Hnilica. 1986. The in vivo crosslinking of proteins and DNA by heavy metals. J Biol Chem 261:3370-3376.

355. WHO. 1977. Environmental Health Criteri a 3 Lead. World Health Organization. Available at http://www.inchem.or g/documents/ehc/ehc/ehc003.htm.

356. Wilkins, J.R.d. and T.H. Sinks, Jr. 1984a . Occupational exposur es among fathers of
children with Wilms' tumor. J Occup Med 26:427-435.

357. Wilkins, J.R.d. and T.H. Sinks, Jr. 1984b. Paternal occupation and Wilms' tumour in offspring. J Epidemiol Community Health 38:7-11.

358. Willems, M.I., G.G. de Schepper, A.A. Wi bowo, H.R. Immel, A.J. Dietrich, and
R.L. Zielhuis. 1982. Absence of an effect of lead acetate on sperm morphology, sister chromatid exchanges or on micronuclei formation in rabbits. Arch Toxicol
50:149-157.

359. Winder, C. and T. Bonin. 1993. The genotoxicity of lead. Mutat Res 285:117-124.

360. Wingren, G. and O. Axelson. 1985. Mortalit y pattern in a glass producing area in
SE Sweden. Br J Ind Med 42:411-414.

361. Wingren, G. and O. Axelson. 1987. Mortalit y in the Swedish glassworks industry.
Scand J Work Environ Health 13:412-416.

362. Wingren, G. and V. Englander. 1990. Mortal ity and cancer morbidity in a cohort of Swedish glassworkers. Int Arch Occup Environ Health 62:253-257.

363. Wingren, G. and O. Axelson. 1993. Epidemio logic studies of occupational cancer as related to complex mixtures of tr ace elements in the art glass industry. Scand J
Work Environ Health 19:95-100.

364. Wise, J.P., J.C. Leonard, and S.R. Patier no. 1992. Clastogenicity of lead chromate particles in hamster and human cells. Mutat Res 278:69-79.

365. Wise, J.P., J.M. Orenstein, and S.R. Pa tierno. 1993. Inhibition of lead chromate clastogenesis by ascorbate: relationshi p to particle dissolution and uptake. Carcinogenesis 14:429-434.05/08/03 RoC Background Document for Lead and Lead Compounds

197 366. Wise, J.P., Sr., D.M. Stearns, K.E. Wetterhahn, and S.R. Patierno. 1994. Cellenhanced dissolution of carcinogenic lead chro mate particles: the role of individual dissolution products in clastogenesis. Carcinogenesis 15:2249-2254.

367. Wong, O. and F. Harris. 2000. Cancer morta lity study of employees at lead battery plants and lead smelters, 1947-1995. Am J Ind Med 38:255-270.

368. Wu, F.Y., P.W. Chang, C.C. Wu, and H. W. Kuo. 2002. Correlations of blood lead with DNA-protein cross-links and sister chromatid exchanges in lead workers. Cancer Epidemiol Biomarkers Prev 11:287-290.

369. Xu, J., J.P. Wise, and S.R. Patier no. 1992. DNA damage induced by carcinogenic lead chromate particles in cultured mammalian cells. Mutat Res 280:129-136.

370. Yang, J.L., S.C. Yeh, and C.Y. Chan g. 1996. Lead acetate mutagenicity and mutational spectrum in the hypoxanthine guanine phosphoribosyltransferase gene of Chinese hamster ovary K1 cells. Mol Carcinog 17:181-191.

371. Yang, J.L., L.C. Wang, C.Y. Chang, a nd T.Y. Liu. 1999. Singlet oxygen is the major species participating in the induction of DNA strand breakage and 8- hydroxydeoxyguanosine adduct by lead acetate. Environ Mol Mutagen 33:194-201.

372. Ye, X.B., H. Fu, J.L. Zhu, W.M. Ni, Y. W. Lu, X.Y. Kuang, S.L. Yang, and B.X. Shu. 1999. A study on oxidative stress in lead-exposed workers. J Toxicol Environ
Health A 57:161-172.

373. Yuan, X. and C. Tang. 2001. The accumulation effect of lead on DNA damage in mice blood cells of three generations and the protection of selenium. J Environ Sci Health Part A Tox Hazard Subst Environ Eng 36:501-508.

374. Yusof, M., D. Yildiz, and N. Ercal. 1999. N-acetyl-L-cysteine protects against
delta-aminolevulinic acid-induced 8-hydroxydeoxyguanosine formation. Toxicol

Lett 106:41-47.

375. Zawia, N.H., T. Crumpton, M. Brydie, G.R. Reddy, and M. Razmiafshari. 2000. Disruption of the zinc finger domain: a common target that underlies many of the
effects of lead. Neurotoxicology 21:1069-1080.

376. Zawirska, B. and K. Medras. 1968. [Tumors and disorders of porphyrin metabolism in rats with chronic experimental lead poisoning. I. Mor phological studies]. Zdrav

Prac 111:1-12.

377. Zawirska, B. and K. Medras. 1972. The ro le of the kidneys in disorders of porphyrin metabolism during carcinogene sis induced with lead acetate. Arch Immunol Ther Exp 20:257-272.

378. Zelikoff, J.T., J.H. Li, A. Hartwig, X. W. Wang, M. Costa, and T.G. Rossman. 1988. Genetic toxicology of lead compounds. Carcinogenesis 9:1727-1732.05/08/03 RoC Background Document for Lead and Lead Compounds

198 379. Zhang, Z.W., S. Shimbo, N. Ochi, M. E guchi, T. Watanabe, C.S. Moon, and M.
Ikeda. 1997. Determination of lead and cadmium in food and blood by inductively coupled plasma mass spectrometry: a co mparison with graphite furnace atomic absorption spectrometry. Sci Total Environ 205:179-187.

380. Zollinger, H.U. 1953. Kidney adenomas and carcinomas in rats following chronic administration of lead and their possi ble relationship to the corresponding neoplasms in man (Ger.). Virchows Arch Pathol Anat 326:694-710.05/08/03 RoC Background Document for Lead and Lead Compounds

199 

## Appendix A: Lead Regulations05/08/03 RoC Background Document for Lead and Lead Compounds

20005/08/03 RoC Background Document for Lead and Lead Compounds

A-1 Table A-1. CPSC regulations

Regulatory citation Regulatory action

16 CFR 1303 - PART 1303 - BAN OF LEADCONTAINING PAINT AND CERTAIN CONSUMER
PRODUCTS BEARING LEAD-CONTAINING
PAINT. 1978. Bans paint or any other similar surface coating that
contains more than 0.06% lead.

The regulations in this table have been updated through the 2001 Code of Federal Regulations 29 CFR, July 1, 2001.

Table A-2. EPA regulations

Regulatory citation Regulatory action

40 CFR 50 – PART 50 – NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS. Promulgated: 36 FR 22384, 11/25/71. U.S. Codes: 42 U.S.C. 7409, 7601(a). National primary and secondary ambient air quality standards for lead and its compounds, measured as elemental lead, are 1.5 μ g/m 3 , maximum arithmetic mean averaged over a calendar quarter.

40 CFR 60 - PART 60, SUBPART L - STANDARDS
OF PERFORMANCE FOR SECONDARY LEAD SMELTERS. Promulgated: 42 FR 37937, 7/25/77. U.S.
Codes: 42 U.S.C. 7401-7601. Standards for particulate matter for secondary lead smelters are: < 50 mg/dscm (0.022 gr/dscf) for blast (cupola) or reverberatory furnace and < 20% opacity.

40 CFR 60 - PART 60, SUBPART P - STANDARDS
OF PERFORMANCE FOR PRIMARY COPPER SMELTERS. Promulgated: 41 FR 2338, 1/15/76. U.S.
Codes: 42 U.S.C. 7401-7601. Standards for particulate matter have been set for primary copper smelters.

40 CFR 60 - PART 60, SUBPART R - STANDARDS
OF PERFORMANCE FOR PRIMARY LEAD SMELTERS. Promulgated: 41 FR 2340, 1/15/76. U.S.
Codes: 42 U.S.C. 7401-7601. Standards for particulate matter for secondary lead smelters are: < 50 mg/dscm (0.022 gr/dscf) for blast furnace, dross reverberator y furnace, or sintering machine discharge, < 20% opacity, and < 0.065% by volume sulfur dioxide.

40 CFR 60 - PART 60, SUBPART CC - STANDARDS
OF PERFORMANCE FOR GLASS MANUFACTURING PLANTS. Promulgated: 36 FR 24877, 12/23/77l U.S. Codes: 42 U.S.C. 7401-7601. Standards for particulate matter have been set for glass manufacturing plants.

40 CFR 60 - PART 60, SUBPART KK - STANDARDS
OF PERFORMANCE FOR LEAD-ACID BATTERY MANUFACTURING PLANTS. Promulgated 47 FR 16573, 4/16/82. U.S. Codes: 42 U.S.C. 7401-7601. Standards for lead are: < 0.40 mg/m 3 of exhaust (0.000176 gr/dscf) for grid casting facilities, <1 mg/m 3 of exhaust (0.00044 gr/dscf) for paste mixing facilities or three-process operation facilities, <5.0 mg/kg lead feed (0.010 lb/ton) for lead oxide manufacturing facilities, < 4.50 mg/m 3 of exhaust (0.00198 gr/dscf), 1.0 mg/m 3 of exhaust (0.00044 gr/dscf) for any other lead-emitting operation, 0%opacity for affected facilities other than leadreclamation facilities, < 5% opacity for lead
reclamation facilities.05/08/03 RoC Background Document for Lead and Lead Compounds

A-2 Regulatory citation Regulatory action

40 CFR 60 - PART 60, SUBPART VV - STANDARDS OF PERFORMANCE FOR EQUIPMENT LEAKS OF
VOC IN THE SYNTHETIC ORGANIC CHEMICALS MANUFACTURING INDUSTRY (SOCMI), Promulgated 48 FR 48335, 10/18/83. U.S. Codes: 42

U.S.C. 7401-7601. Standards of performance have been set for equipment leaks for facilities in the Synthetic Organic Chemicals Manu facturing Industry producing tetraethyl lead and tetramethyl lead.

40 CFR 60 - PART 60, SUBPART NNN -
STANDARDS OF PERFORMANCE FOR VOC
EMISSIONS IN THE SYNTHETIC ORGANIC
CHEMICALS MANUFACTURING INDUSTRY (SOCMI) DISTILLATION OPERATIONS, Promulgated 55 FR 26942, 6/29/90. Codes: 42 U.S.C.
7401-7601. Standards of performance have been set for VOC emissions for facilities in the Synthetic Organic Chemicals Manufacturing Industry, distillation operations, producing tetraethyl lead and tetramethyl lead.

40 CFR 60 - PART 60, SUBPART NNN -
STANDARDS OF PERFORMANCE FOR VOC
EMISSIONS IN THE SYNTHETIC ORGANIC
CHEMICALS MANUFACTURING INDUSTRY (SOCMI) REACTOR PROCESSES, Promulgated 58 FR 45962, 8/31/93. Codes: 42 U.S.C. 7401-7601. Standards of performance have been set for VOC emissions for facilities in the Synthetic Organic Chemicals Manufacturing Industry, reactor processes, producing tetraet hyl lead and tetramethyl
lead.

40 CFR 63 - PART 63, SUBPART RRR - NATIONAL
EMISSION STANDARDS FOR HAZARDOUS AIR
POLLUTANTS FOR SOURCE CATEGORIES. Promulgated: 57 FR 61992, 12/29/92. U.S. Codes: 42 U.S.C. 7401 et seq.1. Hazardous waste incinerato rs must not discharge lead and cadmium > 240 g/dscm, combined emissions, corrected to 7% oxygen.

40 CFR 80 - PART 80, SUBPART A - DEFINITION. Promulgated 38 FR 1255, 1/10/73, as amended at 38 FR 33741, 12/6/73; 42 FR 25732, 5/19/77. U.S. Codes: 42 U.S.C. 7414, 7545, and 7601(a). Definition of unleaded gasoline is < 0.05 g of lead per gallon and < 0.005 g phosphorus/gallon.

40 CFR 80 - PART 80, SUBPART B - CONTROLS AND PROHIBITIONS. Promulgated 38 FR 1255, 1/10/73, as amended at 6/26/96. U.S. Codes: 42 U.S.C. 7414, 7545, and 7601(a). No person shall sell gasoline with > 0.05 g of lead per gallon.

40 CFR 80 - PART 80, SUBPART D - REFORMULATED GASOLINE. Promulgated 59 FR 7813, 2/16/94. U.S. Codes: 42 U.S.C. 7414, 7545, and 7601(a). Reformulated gasoline may not contain lead.

40 CFR 80 - PART 80, SUBPART G - DETERGENT GASOLINE. Promulgated 59 FR 54706, 11/1/94. U.S. Codes: 42 U.S.C. 7414, 7545, and 7601(a). Detergent gasoline must meet the requirements outlined, including the definition of unleaded gasoline.

40 CFR 80 - PART 80, APPENDIX B - TEST METHODS FOR LEAD IN GASOLINE. Promulgated 38 FR 1255, 1/10/73. U.S. Codes: 42 U.S.C. 7414, 7545, and 7601(a). Test methods have been established for lead in gasoline.

40 CFR 86 - PART 86, SUBPART F - EMISSION
REGULATIONS FOR 1978 AND LATER NEW MOTORCYCLES; TEST PROCEDURES. Promulgated 42 FR 1137, 1/5/77. U.S. codes: 42 U.S.C. 7401 - 7671q. For leaded fuel, the lead content shall not exceed 0.1 g of lead per gallon.05/08/03 RoC Background Document for Lead and Lead Compounds

A-3 Regulatory citation Regulatory action

40 CFR 116 - PART 116 - DESIGNATION OF HAZARDOUS SUBSTANCES. Promulgated: 43 FR 10474, 03/13/78. U.S. Codes: 33 U.S.C. 1251 et seq. Lead acetate, lead arsenate, lead chloride, lead fluoroborate, lead fluoride, lead iodide, lead nitrate, lead stearate, lead salt, lead sulfate, lead sulfide, and lead thiocyanate are cl assified as hazardous
substances.

40 CFR 117 – PART 117 – DETERMINATION OF REPORTABLE QUANTITIES FOR HAZARDOUS SUBSTANCES. Promulgated: 44 FR 50776, 08/29/79. U.S. Codes: 33 U.S.C. 1251 et seq., as amended by the
Clean Water Act of 1977. Discharges to water of amounts equal to or greater than the Reportable Quantity (RQ) must be reported to EPA. RQs for environm ental releases of lead acetate, lead chloride, lead fluoborate, lead fluoride, lead iodide, lead nitrate, l ead stearate, lead sulfate, lead sulfide, and lead th iocyanate are 10 lb (4.54 kg). The RQ for lead arsenate is 1 lb (0.454 kg).

40 CFR 136 - GUIDELINE S ESTABLISHING TEST
PROCEDURES FOR THE ANALYSIS OF POLLUTANTS. Promulgated: 55 FR 33442, 8/15/90. U.S. Codes: 33 U.S.C. 1251, et seq., as amended by the
Clean Water Act of 1977. Established test methods for the identification of
lead.

40 CFR 141 - PART 141, SUBPART E - SPECIAL REGULATIONS, INCLUDING MONITORING
REGULATIONS AND PROHIBITION ON LEAD USE. Promulgated: 52 FR 20674 6/2/87, as amended at 65 FR 2002, 1/12/00. U.S. Codes: 42 U.S.C. 300 g-6(e). All plumbing shall be lead-free. The definition of

lead-free is: solder and flux must contain ≤ 0.2% lead; pipes and pipe fittings must contain ≤ 8.0%
lead.

40 CFR 141 - PART 141, SUBPART I - NATIONAL PRIMARY DRINKING WATER REGULATIONS, CONTROL OF LEAD AND COPPER. Promulgated: 56 FR 26548, 6/7/91. U.S. Codes: 42 U.S.C. 300f, g, and j. To protect a safe drinking water supply, a treatment technique that includes corrosion control, source water treatment, lead service line replacement, and public education has been set for lead. An action level of 0.015 mg/l has been established for lead;
this action level is exceeded if the concentration of lead in > 10% of the tap water samples is > 0.015 mg/L.

40 CFR 141 - PART 141, SUBPART Q - PUBLIC
NOTIFICATION OF DRINKING WATER VIOLATIONS. Promulgated: 65 FR 26035, 5/4/00. U.S. Codes: 42 U.S.C. 300f, g, and j. Public water systems must notify the public for
violations of maximum contaminant levels or treatment techniques for a ll regulated contaminants, including lead.

40 CFR 258 - PART 258 - CRITERIA FOR
MUNICIPAL SOLID WASTE LANDFILLS. Promulgated 56 FR 51016, 10/9/91. U.S. Codes: 33 U.S.C. 1345(d)(e); 42 U.S.C. 6902(a), 6907, 6912(a), 6944, 6945(c), 6949a(c). Lead is considered a hazardous inorganic compound in municipal solid waste landfills. A maximum contaminant level (MCL) of 0.05 mg/L has been set
for lead.

40 CFR 261 - PART 261 - IDENTIFICATION AND LISTING OF HAZARDOUS WASTES. Promulgated: 46 FR 4619, 1981 with numerous amendments. U.S. Codes: 42 U.S.C. 6905, 6912(a), 6921, 6922, and 6938. Solid wastes containing lead are subject to notification requirements and the constituent maximum concentration of lead in any composite wastewater sample is 0.15 mg/L.

40 CFR - PART 264, SUBPART CC - AIR EMISSION STANDARDS FOR TANKS, SURFACE IMPOUNDMENTS AND CONTAINERS. Promulgated 56 FR 62927, 12/6/94. U.S. Codes 42 U.S.C. 6906, 6912, 6922-6925, 6937, 6938. The Sisterville Plant in West Virginia shall monitor
for lead.05/08/03 RoC Background Document for Lead and Lead Compounds

A-4 Regulatory citation Regulatory action

40 CFR - PART 264, SUBPART EE - HAZARDOUS
WASTE MUNITIONS AND EXPLOSIVES STORAGE. Promulgated 62 FR 6652, 2/12/97. U.S. Codes 42 U.S.C. 6906, 6912, 6922-6925, 6937, 6938. Lead must be monitored for in groundwater.

40 CFR 266 - PART 266, SUBPART H -
HAZARDOUS WASTE BURNED IN BOILERS AND INDUSTRIAL FURNACES. Promulgated 56 FR 7208, 2/21/91 and 64 FR 53075, 9/30/99. 42 U.S.C. 1006, 2002(a), 3004, 3014, 6905, 6906, 6912, 6922, 6924, 6925, 6937. Reference air concentrations have been set for
release of lead from h azardous waste burned in
boilers and industrial furnaces as follows: lead = 0.00009 mg/L, tetraethyl lead = 0.0000001 mg/L.

40 CFR 266 - PART 266, SUBPART M - MILITARY MUNITIONS. Promulgated 62 FR 6654, 2/12/97. 42 U.S.C. 1006, 2002(a), 3004, 3014, 6905, 6906, 6912, 6922, 6924, 6925, 6937. Military munitions wastes containing lead must be
stored as hazardous wastes.

40 CFR 268 - PART 268 - LAND DISPOSAL RESTRICTIONS. Promulgated 51 FR 40638. 42 U.S.C. 6905, 6912(a), 6921, 6924. Lead is listed as a hazardous waste restricted from land disposal.

40 CFR 300 - PART 300, SUBPART L - NATIONAL
OIL AND HAZARDOUS SUBSTANCES POLLUTION CONTINGENCY PLAN; INVOLUNTARY ACQUISITION OF PROPERTY BY THE GOVERNMENT. Promulgated 62 FR 34602,
6/26/97. U.S. Codes: 42 U.S.C. 9605 and 33.U.S.C.1321(d). Provides procedures for responding to discharges of oil and hazardous substances. In the hazard ranking system, lead has a human to xicity factor value of 10,000.

40 CFR 302 – PART 302 – DESIGNATION, REPORTABLE QUANTITIES, AND NOTIFICATION. Promulgated: 50 FR 13474, 04/04/85. U.S. Codes: 42 U.S.C. 9602, 9603, and 9604; 33 U.S.C.
1321 and 1361. This part designates RQs for lead acetate, lead subacetate, lead chloride , lead fluoborate, lead fluoride, lead iodide, lead nitrate, lead phosphate, lead stearate, lead sulfate, lead sulfide, lead thiocyanate, and tetraethyl lead are 10 lbs (4.54 kg). The RQ for lead arsenate is 1 lb (0.454 kg).

40 CFR 372 – PART 372 – TOXIC CHEMICAL
RELEASE REPORTING: COMMUNITY RIGHT-TOKNOW. Promulgated: 53 FR 4525, 02/16/88; 1/16/01.
U.S. Codes: 42 U.S.C. 11023 and 11048. Toxic release information is collected for lead to inform the general public and the communities surrounding covered facilities about releases of toxic chemicals, to assist research, and to aid in the development of regulations, guidelines, and standards. The reporting threshold for lead and lead compounds was lowered to 100 lbs (1/16/01).

40 CFR 401 – PART 401 – GENERAL PROVISIONS. Promulgated: 39 FR 4532, 02/01/74. U.S. Codes: 33 U.S.C. 1251, 1311, 1314 (b) and (c), 1316 (b) and (c), 1317 (b) and (c) and 1326(c); 86 Stat. 816 et seq.; Pub.
L. 92-500. Lead and lead compounds are classified as toxic pollutants under the Clean Water Act.

40 CFR 414 - PART 414 - ORGANIC CHEMICALS, PLASTICS, AND SYNTHETI C FIBERS. Promulgated 52 FR 42568, 11/5/87, as amended at 57 FR 41844, 9/11/92. U.S. codes: 33 U.S.C. 1311, 1314(b)(c)(e), 1316(b)(c), 1317(b)(c), 1318, and 1361. Effluent limitation guidelines have been set for tetraethyl lead and tetram ethyl lead for organic chemicals, plastics, and synthetic fiber
manufacturers.05/08/03 RoC Background Document for Lead and Lead Compounds

A-5 Regulatory citation Regulatory action

40 CFR 415 - PART 415, SUBPART AR -
INORGANIC CHEMICALS MANUFACTURING POINT SOURCE CATEGORY, LEAD MONOXIDE PRODUCTION SUBCATEGORY. Promulgated 47 FR 28278, 6/29/82. U.S. codes: 33 U.S.C. 1311, 1314(b)(c)(e), 1316(b)(c), 1317(b)(c), 1318, and 1361. Effluent limitation guidelines have been set for lead for inorganic chemicals manufacturers.

40 CFR 420 - PART 420 - IRON AND STEEL
MANUFACTURING POINT SOURCE CATEGORY. Promulgated 47 FR 23284, 5/27/82. U.S. codes: 33 U.S.C. 1311, 1314(b)(c)(e), 1316(b)(c), 1317(b)(c), 1318, and 1361. Effluent limitation guidelines have been set for lead
for iron and steel manufacturers.

40 CFR 421 - PART 421 - NONFERROUS METALS MANUFACTURING POINT SOURCE CATEGORY,
SUBPART G - PRIMARY LEAD SUBCATEGORY. Promulgated 49 FR 8790, 3/8/84. U.S. codes: 33 U.S.C. 1311, 1314(b)(c)(e), 1316(b)(c), 1317(b)(c), 1318, and
1361. Effluent limitation guidelines have been set for lead
for nonferrous metals manufacturers.

40 CFR 423 - PART 423 - STEAM ELECTRIC
POWER GENERATING POINT SOURCE CATEGORY. Promulgated 47 FR 52304, 11/19/82. U.S. codes: 33 U.S.C. 1311, 1314(b)(c)(e), 1316(b)(c), 1317(b)(c), 1318, and 1361. Effluent limitation guidelines have been set for lead for steam electric power generating manufacturers.

40 CFR 455 - PART 455 - PESTICIDE CHEMICALS,
SUBPART A - ORGANIC PESTICIDE CHEMICALS MANUFACTURING SUBCATEGORY. Promulgated 43 FR 17776, 4/25/78. U.S. codes: 33 U.S.C. 1311, 1314(b)(c)(e), 1316(b)(c), 1317(b)(c), 1318, and 1361. Effluent limitation guidelines have been set for lead for organic pesticide manufacturers.

40 CFR 461 - PART 461 - BATTERY MANUFACTURING, POINT SOURCE CATEGORY, SUBPART C - LEAD SUBCATEGORY. Promulgated 49 FR 9134, 3/9/84. U.S. codes: 33 U.S.C. 1311, 1314(b)(c)(e), 1316(b)(c), 1317(b)(c), 1318, and 1361. Effluent limitation guidelines have been set for lead for battery manufacturers.

40 CFR 464 - PART 464 - METAL MOLDING AND
CASTING POINT SOURCE CATEGORY. Promulgated 50 FR 45247, 10/30/85. U.S. codes: 33 U.S.C. 1311, 1314(b)(c)(e), 1316(b)(c), 1317(b)(c), 1318, and 1361. Effluent limitation guidelines have been set for lead for metal molding and casting manufacturers.

40 CFR 468 - PART 468 - COPPER FORMING POINT SOURCE CATEGORY. Promulgated 48 FR 36957, 8/15/83. U.S. codes: 33 U.S.C. 1311, 1314(b)(c)(e), 1316(b)(c), 1317(b)(c), 1318, and 1361. Effluent limitation guidelines have been set for lead for copper forming manufacturers.05/08/03 RoC Background Document for Lead and Lead Compounds

A-6 Regulatory citation Regulatory action

40 CFR 471 - PART 471 - NONFERROUS METALS
FORMING POINT SOURCE CATEGORY, SUBPART
A - LEAD-TIN-BISMUTH FORMING SUBCATEGORY, SUBPART F - TITANIUM
FORMING SUBCATEGOR Y, SUBPART G - URANIUM FORMING SUBCATEGORY, SUBPART
J - METALS POWDERS SUBCATEGORY. Promulgated 48 FR 36957, 8/15/83. U.S. codes: 33 U.S.C. 1311, 1314(b)(c)(e), 1316(b)(c), 1317(b)(c), 1318, and 1361. Effluent limitation guidelines have been set for lead for metals powders, titanium forming, uranium, and lead-tin-bismuth forming manufacturers.

40 CFR 503 - PART 50 3 - STANDARDS FOR THE
USE AND DISPOSAL OF SEWAGE SLUDGE. Promulgated 58 FR 9387, 2/19/93. U.S. Codes: 33 U.S.C. 1345 (d) and (e) and 33 U.S.C. 1251 et seq. The following standards have been set for lead in sewage sludge applied to the land, placed on a surface disposal site, or fired in a sewage sludge incinerator: ceiling concentration = 840 mg/kg; cumulative pollutant loading rate = 300 kg/hectare; annual loading rate = 15 kg/hectare/365 days.

40 CFR 745 - PART 745 - LEAD-BASED PAINT
PREVENTION IN CERTAIN RESIDENTIAL STRUCTURES. Promulgated 61 FR 9085, 3/6/96. U.S. Codes: 15 U.S.C. 2605, 2607, 2681-2692 and 42 U.S.C. 4852(d). A seller must disclose to the purchaser any leadbased paint in a home for sale; paint used in home

renovations must not contain lead ≥ 1.0 mg/cm 2 or ≥ 0.5% by weight; a pamphlet on the health hazards of lead must be provided to the homeowner. Amended

3/6/01: Dust-lead hazar d consists of lead ≥ 40 μ g/ft 2

on floors or 250 μ g/ft 2 on interior window sills.

Soil-lead hazard consists of lead ≥ 400 ppm ( μ g/g) in play area, or average of 1,200 ppm in bare soil.

The regulations in this table have been updated through the 2001 Code of Federal Regulations 40 CFR, July 1, 2001

Table A-3. FDA regulations

Regulatory citation Regulatory action

21 CFR 73 - PART 73 -LISTING OF COLOR
ADDITIVES EXEMPT FROM CERTIFICATION. Promulgated: 42 FR 15643, 03/22/77. U.S. Codes: 21 U.S.C. 321, 341, 342, 343, 348, 351, 352, 355, 361, 362, 371, 379e. Concentration limits for lead in various color additives used in foods, drugs, cosmetics, and medical devices may not exceed 5–70 ppm. The
concentration of lead acet ate may not exceed 0.6% (weight to volume) in hair coloring for scalp use only.

21 CFR 74 - PART 74 - LISTING OF COLOR
ADDITIVES SUBJECT TO CERTIFICATION. Promulgated: 42 FR 15654, 03/22/77. U.S. Codes: 21 U.S.C. 321, 341, 342, 343, 348, 351, 352, 355, 361, 362, 371, 379e. Concentration limits for lead in various color additives used in foods, drugs, cosmetics, and medical devices may not exceed 10–40 ppm.05/08/03 RoC Background Document for Lead and Lead Compounds

A-7 Regulatory citation Regulatory action

21 CFR 109 - PART 109 - UNAVOIDABLE
CONTAMINANTS IN FOOD FOR HUMAN
CONSUMPTION AND FOOD-PACKAGING MATERIAL. Promulgated: 42 FR 52819, 09/30/77. U.S. Codes: 21 U.S.C. 321, 336, 342, 346, 346a, 348,

371. A conspicuous stick-on label shall be on the surface of ornamental or decorative ceramics clearly visible
to consumers that states one of the following messages: "Not for Food Use. May Poison Food,"
"Not for Food Use. Glaze contains lead. Food Use May Result in Lead Poisoning," and "Not for Food Use-Food Consumed from this Vessel May be Harmful,"

21 CFR 109 and 509 - PARTS 109 and 509 - ACTION

LEVELS FOR POSIONOUS OR DELETERIOUS
SUBSTANCES IN HUMAN FOOD AND ANIMAL FEED. Compliance Policy Guide 545.450 Action levels for lead in ceramicware are: flatware

= 3.0 μ g/mL leaching solution, small hollowware (other than cups and mugs) = 2.0 μ g/mL leaching solution, large hollowware (other than pitchers) =

1.0 μ g/mL leaching solution, cups and mugs = 0.5

μ g/mL leaching solution, pitchers = 0.5 μ g/mL leaching solution.

21 CFR 109 and 509 - PARTS 109 and 509 - ACTION

LEVELS FOR POSIONOUS OR DELETERIOUS
SUBSTANCES IN HUMAN FOOD AND ANIMAL FEED. Compliance Policy Guide 545.500 Action levels for silver-plated hollowware are: product intended for use by adults = 7 μ g/mL leaching solution, product intended for use by

infants and children = 0.5 μ g/mL leaching solution.

21 CFR 189 - PART 189 - SUBSTANCES
PROHIBITED FROM INDIRECT ADDITION TO
HUMAN FOOD THROUGH FOOD-CONTACT SURFACES. Promulgated: 60 FR 33109, 06/27/95. U.S. Codes: 21 U.S.C. 321, 342, 348, 371. Food packaging must not contain lead solder.

21 CFR 584 - PART 58 4 - FOOD SUBSTANCES
AFFIRMED AS GENERALLY RECOGNIZED AS
SAFE IN FEED AND DRINKING WATER OF ANIMALS. Promulgated: 61 FR 43453, 08/23/96. U.S. Codes: 21 U.S.C. 321, 342, 348, 371. Amorphous fumed hydrophobic silica or precipitated hydrophobic silica may be used as an anticaking/free-flow agent in vitamin preparations for animal feed provided that lead concentration do not exceed 10 ppm.

The regulations in this table have been updated through the 2001 Code of Federal Regulations 21 CFR, April 1, 2001.

Table A-4. OSHA regulations

Regulatory citation Regulatory action

29 CFR 1910 - PART 1910.1025, SUBPART Z -
TOXIC AND HAZARDOUS SUBSTANCES. Promulgated 60 FR 52856, 10/11/95, as amended numerous times. U.S. codes: 29 U.S.C. 653, 655, 657. Establishes permissible exposure limit (PEL) for

lead of 50 μ g/m 3 as an 8-hour time-weighted average (TWA). Action level of 30 μ g/m 3 TWA, 8- hour workday. Initiates exposure monitoring, medical surveillance, and training and education.

29 CFR 1910 - PART 1910.1200, SUBPART Z - HAZARD COMMUNICATION. Promulgated 59 FR 17479, 4/13/94; 59 FR 65947, 12/22/94; and 61 FR 5507, 2/13/96. U.S. codes: 29 U.S.C. 653, 655, 657. Requires that the hazards of all chemicals produced or imported are evaluated, and that information concerning their hazards is transmitted to employers and employees. Hazard communication programs are to include container labeling and other forms of warning, material safety data sheets and employee training.05/08/03 RoC Background Document for Lead and Lead Compounds

A-8 Regulatory citation Regulatory action

29 CFR 1910 - PART 1910.1450, SUBPARAT Z -
OCCUPATIONAL EXPOSURE TO HAZARDOUS CHEMICALS IN LABORATORIES. Promulgated 61 FR 5507, 2/13/96. U.S. codes: 29 U.S.C. 653, 655, 657. Establishes requirements for laboratory use of hazardous chemicals, in cluding initial exposure determination, development of a chemical hygiene plan, employee information and training, and other requirements.

29 CFR 1926 - PART 1926, SUBPART D -
OCCUPATIONAL HEALTH AND ENVIRONMENTAL CONTROLS. Promulgated 57 FR 26627, 5/4/93, as amended numerous times. U.S. codes: 40 U.S.C. 333, 29 U.S.C. 653, 655, 657. Establishes PEL for lead of 50 μ g/m 3 as an 8-hour

TWA in construction. Action level of 30 μ g/m 3 TWA, 8-hour workday. Initiates exposure monitoring, medical surveillance, and training and
education.

The regulations in this table have been updated through the 2001 Code of Federal Regulations 29 CFR, July 1, 2001.