TOXICOLOGICAL PROFILE FOR
 

RADIUM
 

Agency for Toxic Substances and Disease Registry
 

U.S. Public Health Service
 

In collaboration with:
 

U.S. Environmental Protection Agency
 

December 1990
 
ii
 

DISCLAIMER
 

The use of company or product name(s) is for identification only
 

and does not imply endorbement by the Agency for Toxic Substances and
 

Disease Registry.
 










1
 

1. PUBLIC HEALTH STATEMENT
 

This Statement was prepared to give you information about radium
 

and to emphasize the human health effects that may result from exposure
 

to it. The Environmental Protection Agency (EPA) has identified 1,177
 

sites on its National Priorities List (NPL). Radium has been found
 

above background levels at 18 of these sites. However, we do not know
 

how many of the 1,177 NPL sites have been evaluated for radium. As EPA
 

evaluates more sites, the number of sites at which radium is found above
 

background levels may change. The information is important for you
 

because radium may cause harmful health effects and because these sites
 

are potential or actual sources of human exposure to radium.
 

When a radioactive chemical is released from a large area, such as
 

an industrial plant, or from a container, such as a drum or bottle, it
 

enters the environment as a radioactive chemical emission. This
 

emission, which is also called a release, does not always lead to
 

exposure. You can be exposed to a radioactive chemical when you come
 

into contact with that chemical alone or with a substance that contains
 

it. You may be exposed to it in the environment by breathing, eating,
 

or drinking substances containing the radioactive chemical or from skin
 

contact with it. Exposure can also occur by being near radioactive
 

chemicals at concentrations that are found at hazardous waste sites or
 

industrial accidents.
 

If you are exposed to a hazardous substance such as radium,
 

several factors will determine whether harmful health effects will occur
 

and what the type and severity of those health effects will be. These
 

factors include the dose (how much), the duration (how long), the route
 

or pathway by which you are exposed (breathing, eating, drinking, or
 

skin contact), the other chemicals to which you are exposed, and your
 

individual characteristics such as age, sex, nutritional status, family
 

traits, life style, and state of health.
 

1.1 WHAT IS RADIUM?
 

Radium is a naturally-occurring silvery white radioactive metal
 

that can exist in several forms called isotopes. It is formed when
 

uranium and thorium (two other natural radioactive substances) decay
 

(break down) in the environment. Radium has been found at very low
 

levels in soil, water, rocks, coal, plants, and food. For example, a
 

typical amount might be one picogram of radium per gram of soil or rock.
 

This would be about one part of radium in one trillion (1,000,000,000,000)
 

parts of soil or rock. These levels are not expected to change with time.
 
2
 

1. PUBLIC HEALTH STATEMENT
 

Some of the radiation from radium is constantly being released into
 

the environment. It is this release of radiation that causes concern
 

about the safety of radium and all other radioactive substances. Each
 

isotope of radium releases radiation at its own rate, One isotope,
 

radium-224 for example, releases half of its radiation in about three
 

and a half days; whereas another isotope, radium-226, releases half of
 

its radiation in about 1,600 years.
 

When radium decays it divides into two parts. One part is called
 

radiation, and the second part is called a daughter. The daughter, like
 

radium, is not stable; and it also divides into radiation and another
 

daughter. The dividing continues until a stable, nonradioactive
 

daughter is formed. During the decay process, alpha, beta, and gamma
 

radiations are released. Alpha particles can travel only a short
 

distance and cannot travel through your skin. Beta particles can
 

penetrate through your skin, but they cannot go all the way through your
 

body. Gamma radiation, however, can go all the way through your body.
 

Thus, there are several types of decay products that result from radium
 

decay.
 

More information about the properties and uses of radium is found
 

in Chapters 3, 4, and 5.
 

1.2 HOW MIGHT I BE EXPOSED TO RADIUM?
 

Because radium is present, usually at very low levels, in the
 

surrounding environment, you are always exposed to it and to the small
 

amounts of radiation that it releases to its surroundings. You may be
 

exposed to higher levels of radium if you live in an area where it is
 

released into the air from the burning of coal or other fuels, or if
 

your drinking water is taken from a source that is high in natural
 

radium, such as a deep well, or from a source near a radioactive waste
 

disposal site.
 

Levels of radium in public drinking water are usually less than one
 

picocurie per liter of water (about one quart), although higher levels
 

(more than 5 picocuries per liter) have been found. A picocurie (pCi)
 

is a very small amount of radioactivity, and it is associated with about
 

a trillionth of a gram (a picogram) of radium. (There are approximately
 

28 grams in an ounce.) No information is available about the amounts of
 

radium that are generally present in food and air. You may also be
 

exposed to higher levels of radium if you work in a uranium mine or in a
 

plant that processes uranium ores.
 

You will find more information on how you can be exposed to radium
 

in Chapter 5.
 
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1. PUBLIC HEALTH STATEMENT
 

1.3 HOW CAN RADIUM ENTER AND LEAVE MY BODY?
 

Radium can enter the body when it is breathed in or swallowed. It
 

is not known if it can be taken in through the skin. If you breathe
 

radium into your lungs, some may remain there for months; but it will
 

gradually enter the blood stream and be carried to all parts of the
 

body, especially the bones. For months after exposure, very small
 

amounts leave the body daily through the feces and urine.
 

If radium is swallowed in water or with food, most of it (about
 

8O%) will promptly leave the body in the feces. The other 20% will
 

enter the blood stream and be carried to all parts of the body,
 

especially the bones. Some of this radium will then be excreted in the
 

feces and urine on a daily basis.
 

You will find more information on this subject in Chapter 2.
 

1.4 HOW CAN RADIUM AFFECT MY HEALTH?
 

There is no clear evidence that long-term exposure to radium at the
 

levels that are normally present in the environment (for example, 1 pCi
 

of radium per gram of soil) is likely to result in harmful health
 

effects. However, exposure to higher levels of radium over a long
 

period of time may result in harmful effects including anemia,
 

cataracts, fractured teeth, cancer (especially bone cancer), and death.
 

Some of these effects may take years to develop and are mostly due to
 

gamma radiation. Radium gives off gamma radiation, which can travel
 

fairly long distances through air. Therefore, just being near radium at
 

the high levels that may be found at some hazardous waste sites may be
 

dangerous to your health.
 

More information on this subject is presented in Chapter 2.
 

1.5 WHAT LEVELS OF EXPOSURE HAVE RESULTED IN HARMFUL HEALTH EFFECTS?
 

Radium has been shown to cause adverse health effects such as
 

anemia, cataracts, fractured teeth, cancer and death. As shown in
 

Tables l-l through l-4, the relationship between the amount of radium
 

that you are exposed to and the amount of time necessary to produce
 

these effects is not known. Although there is some uncertainty as to
 

how much exposure to radium increases your chances of developing a
 

harmful health effect, the greater the total amount of your exposure to
 

radium, the more likely you are to develop one of these diseases. More
 

information on this subject is presented in Chapter 2.
 




8
 

1. PUBLIC HEALTH STATEMENT
 

1.6 IS THERE A MEDICAL TEST TO DETERMINE WHETHER I HAVE BEEN EXPOSED
 

TO RADIUM?
 

There are few medical tests to determine if you have been exposed
 

to radium. There is a urine test to determine if you have been exposed
 

to a source of radioactivity such as radium. There is also a test to
 

measure the amount of radon, a breakdown product of radium, when it is
 

exhaled. These tests require special equipment and cannot be done in a
 

doctor's office. Another test can measure the total amount of
 

radioactivity in the body; however, this test is not used except in
 

special cases of high exposure.
 

More information on the methods used to determine levels of
 

exposure to radioactivity can be found in Chapters 2 and 6.
 

1.7 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO PROTECT
 

HUMAN HEALTH?
 

The Environmental Protection Agency (EPA) regulates the amount of
 

radium in drinking water so that it will not contain more than 5 pCi of
 

combined radium-226 and radium-228 per liter of water. The amount of
 

radioactivity from all sources that is allowed in drinking water and the
 

amount that workers may be exposed to in nuclear plants is regulated.
 

1.8 WHERE CAN I GET MORE INFORMATION?
 

If you have any more questions or concerns not covered here, please
 

contact your State Health or Environmental Department or:
 

Agency for Toxic Substances and Disease Registry
 

Division of Toxicology
 

1600 Clifton Road, E-29
 

Atlanta, Georgia 30333
 

This agency can also give you information on the location of the
 

nearest occupational and environmental health clinics. Such clinics
 

specialize in recognizing, evaluating, and treating illnesses that
 

result from exposure to hazardous substances.
 
9
 

2. HEALTH EFFECTS
 

2.1 INTRODUCTION
 

This chapter contains descriptions and evaluations of studies and
 

interpretation of data on the health effects associated with exposure to
 

radium. Its purpose is to present levels of significant exposure for
 

radium based on toxicological studies, epidemiological investigations,
 

and environmental exposure data. This information is presented to
 

provide public health officials, physicians, toxicologists, and other
 

interested individuals and groups with an overall perspective of the
 

toxicology of radium and a depiction of significant exposure levels
 

associated with various adverse health effects.
 

It is important to note that in the various studies reviewed in the
 

preparation of this document, dose levels have been presented by those
 

authors in several ways. In order to facilitate comparisons among
 

studies, these levels have generally been converted to an equivalent
 

dose in microcuries (μCi) and kilo-Becquerels (kBq). The historical 

definition of one curie is the disintegration rate exhibited by one gram 

of radium. There are 0.027 μCi per kBq. In this document, comparisons 

are usually made between total administered amounts of radioactivity, in 

μCi/kg and kBq/kg, instead of using a daily dosage level. 

In the case of radium, as well as any radionuclide, it is important
 

to note that, in addition to the usual routes of exposure that must be
 

considered (inhalation, oral, dermal, and occasionally parenteral) for
 

toxic chemicals, there is also external and internal exposure to
 

emissions of alpha and beta particles and gamma rays; and it is these
 

radioactive emissions which are considered to be responsible for most of
 

the biologically deleterious effects observed in exposed persons.
 

Further information about radionuclides is presented in Appendix B.
 

2.2 DISCUSSION OF HEALTH EFFECTS BY ROUTE OF EXPOSURE
 

To help public health professionals address the needs of persons
 

living or working near hazardous waste sites, the data in this section
 

are organized first by route of exposure -- inhalation, oral, and dermal
 

-- and then by health effect -- death, systemic, immunological,
 

neurological, developmental, reproductive, genotoxic, and carcinogenic
 

effects. These data are discussed in terms of three exposure periods -­

acute, intermediate, and chronic.
 

2.2.1 Inhalation Exposure
 

Early workers using radium undoubtedly inhaled microscopic
 

particles of the salts of radium as well as the daughter products
 

resulting from their decay, as they worked with these compounds.
 
10
 

2. HEALTH EFFECTS
 

Therefore, they must have been continually exposed to alpha and beta
 

particles as well as to the intense penetrating gamma radiation emitted
 

by radium and its daughter products, including radon. Thus, any
 

resulting health effects cannot be attributed to a specific cause but
 

were probably the consequence of a combination of all the radiation
 

insults to that individual.
 

2.2.1.1 Death
 

No information has been located regarding the lethal effects of
 

acute exposure to radium via inhalation.
 

An early case study described a 36-year-old chemist who had worked
 

with radium for 14 years and then suddenly developed acute leukopenia
 

and died of bronchopneumonia within a month after the onset (Reitter and
 

Martland 1926). Autopsy data indicated that 14 PCi of radioactive
 

material, including radium and mesothorium (radium-228), was found in
 

the body, but the observation that 1 μci was found in the lungs (as
 

compared with other internal organs such as the liver, gastrointestinal
 

tract, heart, and kidneys which had no measurable levels of
 

radioactivity) convinced the authors that inhalation was the primary
 

route by which radium had entered the body. Most of the radioactivity
 

was found in the skeleton.
 

No studies were located regarding lethality in animals after
 

inhalation exposure to radium.
 

2.2.1.2 Systemic Effects
 

No studies were located regarding systemic effects in humans or
 

animals after inhalation exposure to radium.
 

2.2.1.3 Immunological Effects
 

Acute leukopenia, with almost total absence of granular leukocytes,
 

leukoblastic groups and lymphoid tissue in the bone marrow, was reported
 

in the case of a 36-year-old chemist who had worked with radium for
 

14 years (Reitter and Martland 1926).
 

No studies were located regarding the following health effects in
 

humans or animals after inhalation exposure to radium:
 

2.2.1.4 Neurological Effects
 

2.2.1.5 Developmental Effects
 

2.2.1.6 Reproductive Effects
 
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2. HEALTH EFFECTS
 

2.2.1.7 Genotoxic Effects
 

2.2.1.8 Cancer
 

2.2.2 Oral Exposure
 

It is important to note that effects observed after the ingestion
 

of radium may be attributed not only to radium itself, but to the
 

presence of any or all of its daughter products produced in vivo and
 

their radioactive emissions.
 

2.2.2.1 Death
 

There is no information on the lethal effects of radium due to
 

acute oral exposure. Many deaths, especially from bone cancer, have
 

occurred in humans following long-term oral exposure to radium-226 and
 

radium-228. As described by Rowland et al. (1978), female radium dial
 

painters in the 1920s who "tipped" their paint brushes with their lips
 

or tongues ingested radium in the process. The dial paint usually
 

contained long-lived radium-226 and shorter-lived radium-228. A
 

toxicity ratio has been developed for these isotopes; it has been
 

estimated that radium-228 is about 2.5 times as effective, per μCi, in 

inducing bone sarcomas as radium-226 (Lloyd et al. 1986; Rowland et al. 

1978; Rundo et al. 1986). For various other effects, estimates of the 

effectiveness of radium-228 relative to radium-226 have ranged from zero 

to six (Rundo et al. 1986). Estimated systemic intakes for these 

workers and other exposed persons are listed in the Argonne National 

Laboratory case tables (Gustafson and Stehney 1985). These estimates 

are extrapolations based on body radium content at the time of 

examination (whether from living subjects or exhumed remains), modified 

by the Norris retention function (Norris et al. 1955) to account for the 

decrease in body radium content since exposure, and the known or 

presumed ratios of these isotopes in the materials to which these 

persons were exposed (Rundo et al. 1986). Radium dose levels have been 

expressed as: effective systemic radium intake = (μCi radium-226) + 

2.5 x (μCi radium-228). 

Some of the radium dial painters ingested amounts of radium
 

sufficient to cause death within a few years of their employment.
 

Martland (1931) described the cases of 18 dial painters who died of
 

cancer at ages 20 to 54 years old. Causes of death were listed as
 

anemia, necrosis of the jaw, and osteogenic sarcoma. The typical period
 

of exposure was about two years.
 

Radium was also used as a "rejuvenating" tonic in the 1920s and was
 

available to the general public in bottled water. Gettler and Norris
 

(1933) described a case of a 52-year-old man who drank about 1,400
 

bottles of "Radithor", containing radium at 2 μg/60 ml bottle, over a 
12
 

2. HEALTH EFFECTS
 

5-year period (total dose: approximately 2,800 μCi or 56 μCi/kg or 

2,074 kBq/kg for a 50-kg man). The cause of death was stated to be a 

combination of necrosis of the jaw, abscess of the brain, secondary 

anemia and terminal bronchopneumonia. However, it is important to note 

that each of these effects can also be attributed to other etiologies. 

No studies were located regarding lethality in animals after oral
 

exposure to any of the isotopes of radium.
 

2.2.2.2 Systemic Effects
 

Based on case studies of radium dial painters, Martland (1931)
 

stated that anemia, regenerative anemia, aregenerative anemia, or
 

pernicious anemia was listed on the death certificates of ten of 18
 

persons autopsied as part of this study. The bases of these diagnoses
 

(e.g., clinical impressions of the cadaver, laboratory findings, etc.)
 

were not clearly stated. Sharpe (1974) analyzed detailed hematological
 

data relating to dial painters as well as to persons exposed to radium
 

in other ways (eg., male laborers and equipment operators in radiumrelated
 

industries). He concluded, however, that there were no
 

consistent differences in hematological indices between the radiumexposed
 

patients and closely matched controls. From the limited
 

available data, it is difficult to determine if hematological effects
 

are a concern for humans exposed to radium.
 

No studies were located regarding hematological effects in animals
 

after oral exposure to radium.
 

No studies were located regarding the following health effects in
 

humans or animals following oral exposure to radium.
 

2.2.2.3 Immunological Effects
 

2.2.2.4 Neurological Effects
 

2.2.2.5 Developmental Effects
 

2.2.2.6 Reproductive Effects
 

2.2.2.7 Genotoxic Effects
 

2.2.2.8 Cancer
 

The Center for Human Radiobiology at the Argonne National
 

Laboratory has been conducting a surveillance program to identify
 

persons exposed to radium and to determine the details of their
 

exposure, in some cases through exhumation of their remains (Gustafson
 

and Stehney 1985). Based on their findings, bone sarcomas, carcinomas
 
13
 

2. HEALTH EFFECTS
 

of the perinasal sinuses and mastoid air cells (often called head
 

cancers), and deterioration of skeletal tissue are considered to be the
 

only effects that are unequivocally attributable to internal radium
 

(Rundo et al. 1986).
 

These bone sarcomas and head carcinomas have been seen in many
 

radium dial painters and have appeared from 5 to more than 50 years
 

after first exposure to radium. Of those dial painters for whom radium
 

intakes have been estimated (a total of 1,907), 41 have developed bone
 

sarcomas, 16 developed head carcinomas, and an additional 3 cases
 

developed both types. Among dial painters whose radium intakes were not
 

estimated (a total of 2,928), 20 cases with bone sarcomas and 5 with
 

head carcinomas were identified. Thus 85 out of 4,835 known dial
 

painters developed a malignancy as a consequence of their oral ingestion
 

of radium (Rundo et al. 1986).
 

Based on data on these dial painters from the 1985 listing of
 

radium cases studied at the Argonne National Laboratory (Gustafson and
 

Stehney 1985) Rundo et al. (1986) have estimated that the lowest total
 

intake level of radium associated with a malignancy was 60 μCi 

(2,222 kBq) or 1.03 μCi/kg (38 kBq/kg) based on an estimated 58 kg body 

weight for a woman. These estimates are based on current radium body 

content modified by the Norris retention function (to account for the 

decrease in body radium content with time since exposure) and an 

estimate of radium-228 from measurements of radium-226 and the known or 

presumed ratios of these isotopes in the materials to which these 

persons were exposed (Rundo et al. 1986). 

Osteogenic sarcomas were reported in 3 out of 5 rats administered 

radium for 20 days by dropper (Evans et al. 1944). Each animal was 

given a different estimated total dose ranging from 10 to 70 μCi. The 

lowest dose to clearly induce a malignancy was 22 μCi (approximately 

73 μCi/kg or 2,703 kBq/kg). 

2.2.3 Dermal Exposure
 

No studies were located regarding the following health effects in
 

humans or animals after dermal exposure to radium.
 

It is important to note, however, that the radium dial painters had
 

chronic dermal exposure to radium on their lips and tongues. Although
 

no recognition of this fact has been located in the literature, it is
 

noteworthy that no local effects on exposed skin have been described in
 

the available case studies of these workers (eg., Martland 1931; Sharpe
 

1974).
 

2.2.3.1 Death
 
14
 

2. HEALTH EFFECTS
 

2.2.3.2 Systemic Effects
 

2.2.3.3 Immunological Effects
 

2.2.3.4 Neurological Effects
 

2.2.3.5 Developmental Effects
 

2.2.3.6 Reproductive Effects
 

2.2.3.7 Genotoxic Effects
 

2.2.3.8 Cancer
 

2.2.4 Other Routes of Exposure
 

While parenteral exposure is not a route posing a significant
 

environmental threat to human health from the isotopes of radium, data
 

acquired in studies using this route are presented here because
 

thousands of persons did acquire radium via this route, and most of the
 

toxicity and metabolic studies with experimental animals have used this
 

route. It is again important to note that effects observed after
 

parenteral administration of radium may be attributed not only to radium
 

itself, but to the presence of any or all of its daughter products and
 

their radioactive emissions in vivo.
 

In the years after World War II (1946 to 1950), repeated injections
 

of radium-224 were given to adults and children in Germany for treatment
 

of tuberculosis, ankylosing spondylitis, and other diseases. Out of
 

about 2,000 persons who received this treatment, 816 of these cases are
 

currently being followed (Spiess et al. 1978). Of the 816, 204 were
 

injected as juveniles (ages 1 to 20 years) and 612 as adults. The
 

average total injected activity was 18 μCi/kg (666 kBq/kg) (Mays et al. 

1985a). 

A second study of persons injected with radium-224 in Germany from
 

1948 to 1975 included 1,473 ankylosing spondylitis patients who were
 

also treated with repeated intravenous injections of radium, but at
 

lower levels. They typically received a series of 10 to 12 injections
 

at weekly intervals, each containing 28 μCi (1,037 kBq). Some patients 

received two or three such series, and one patient received four. The 

average total injected activity was 4.8 μCi/kg (178 kBq/kg) (Wick and 

Gossner 1983, 1989). 

Pure radium-226 was given intravenously as a medication in the
 

United States from the time it first became available until the mid1930s. Treatment of patients at the Elgin State Hospital in Illinois
 

was described by Schlundt et al. (1933), where from 1931 to 1933,
 
15
 

2. HEALTH EFFECTS
 

32 patients were given 10 μCi (370 kBq) injections, usually weekly, for 

periods ranging from about 2 to 6 months. In the 195Os, these patients 

were located, their radium body content was measured, and their health 

status was subsequently followed (Norris et al. 1955). 

2.2.4.1 Death
 

No studies were located regarding acute lethality in humans
 

following parenteral administration of radium isotopes. Early uses of
 

radium-226 by physicians (usually as a treatment for arthritis) involved
 

intravenous injections as large as 1 mg (1,000 μCi or 37,037 kBq) of 

elemental radium (thus approximately 14 μCi /kg or 518 kBq/kg), which 

were claimed to have no ill effects (Proescher 1914). As described in 

Section 2.2.4.8, patients receiving injections of radium have developed 

cancer which has resulted in death. 

Injection of mice with radium (presumably radium-226) at 2,000 to 

4,000 μCi/kg (74,000 to 148,000 kBq/kg) was fatal in 7 to 10 days 

(Proescher and Almquest 1914); however, experimental details were not 

provided. In 12-week-old mice given a single intraperitoneal injection 

of radium-224 or a series of 8 such injections over a period of 4 weeks, 

there was no evidence of a decrease in life span at any level, up to the 

maximum tested, approximately 60 μCi /kg (2,220 kBq/kg) (Humphreys et al. 

1985).
 

2.2.4.2 Systemic Effects
 

No studies have been located regarding respiratory, cardiovascular,
 

gastrointestinal, musculoskeletal, renal, or dermal effects in humans or
 

animals after parenteral administration of radium.
 

Hematological Effects. In a follow-up study of the second group of 

German patients who had received repeated intravenous injections of 

radium-224, the injected doses averaged 4.8 μCi/kg (178 kBq/kg) total 

exposure (Wick and Gossner 1983; Wick et al. 1986) for 1,501 patients. 

Ten cases of bone marrow failure were observed in these patients, as 

compared with 7 cases in the controls (1,338 similar patients not 

treated with radiation) (Wick and Gossner 1989). The statistical 

significance of these findings was not addressed. 

In the bone marrow of mice given intraperitoneal injections of 

radium-226 at 17,820 μCi/kg (660,000 kBq/kg), there was a depression in 

the number of hemopoietic stem cells which lasted until at least 

100 days after the injection but returned to normal by 300 days 

(Schoeters and Vanderborght 1981). Schoeters et al. (1983) reported a 

marked depression in the number of peripheral white blood cells of mice 

at 400 days after a 670 μCi (24,800 kBq) intraperitoneal injection of 
16
 

2. HEALTH EFFECTS
 

the chloride salt of radium-226 (approximately 22,320 μCi /kg or 

827,000 kBq/kg). At 530 days post-injection, these levels appeared to 

be recovering. There were no consistent trends in the peripheral white 

blood cell levels of the lower dose groups (3,960 and 10,000 μCi/kg or 

147,000 and 370,000 kBq/kg). 

Hepatic Effects. Chronic liver diseases, mostly cirrhosis, were
 

reported in 20 cases (out of 682 adults and 218 children) who were
 

followed for an average of 20 years after repeated injections of radium224 totaling an average of 18 μCi/kg (667 kBq/kg). Eighteen of these 

patients were injected as adult men, one as an adult woman, and one as a 

juvenile. The authors suggested that this is a radiation effect; 

however, statistical significance was not addressed and the total 

incidence in this group (2.2%) may have been comparable to that of the 

general population. The higher incidence in men was thought to be 

related to their higher exposure to liver toxins such as alcohol or 

industrial chemicals (Spiess and Mays 1979). 

Ocular Effects. Cataracts were reported in 6% (12/218) of patients
 

injected with radium-224 as children. The known dosages averaged
 

28 μCi/kg (1,037 kBq/kg). Of these cases with known doses, 14% (11/80) 

had cataracts after receiving more than 28 μCi/kg (1,037 kBq/kg), 

whereas only 0.8% (l/131) developed cataracts after receiving less than 

that dose (Stefani et al. 1985). The younger patients received the 

highest doses in μCi/kg in this study, and thus, presumably, the highest 

radiation dose to the eye. The lowest dose known to be associated with 

a cataract that developed after a radium-224 treatment in childhood was 

15.6 μCi/kg (577 kBq/kg) given to a 4.5 year-old-girl (Chmelevsky et al. 

1988a). 

In beagle dogs, intravenously injected radium-226 was deposited in
 

the melanin granules of pigmented cells and rodlike organelles of the
 

tapetum in the eye (a structure that humans do not have). Retention in
 

the eye varied inversely with dose. At doses from 0.062 to 1.1 μCi/kg 

(2.3 to 41 kBq/kg), 1oss of pigment at the higher doses and melanosis
 

and intraocular melanoma formation at the lower doses were observed
 

(Taylor et al. 1972).
 

Other Systemic Effects. Radiation damage to dental tissue, or
 

perhaps to its blood supply, initiates extensive resorption of the
 

dentine, especially at the gum line. These radiation-induced caries
 

weaken teeth and cause them to fracture easily. Such tooth breakage has
 

been reported in 12% (27/218) of patients injected with radium-224 as
 

children (20 years old and younger) and by 2% (17/681) of patients
 

injected as adults (21 years old and older). The highest incidence
 
17
 

2. HEALTH EFFECTS
 

occurred in adolescents injected at 16 to 20 years of age (15/61 or
 

25%). Combining results from all age groups, the incidence of tooth
 

fracture increased significantly with dose (p=0.01) (Sonnabend et al.
 

1986).
 

2.2.4.3 Immunological Effects


 No studies were located regarding immunological effects in humans
 

after parenteral exposure to radium.
 

A marked decrease was found in the number of peripheral white blood
 

cells of mice at 400 days after an intraperitoneal injection of the 

chloride salt of radium-226 at about 22,320 μCi/kg (827,000 kBq/kg) 

(Schoeters et al. 1983). These results suggest that compromised immune 

function may be a concern for humans exposed to radium. 

2.2.4.4 Neurological Effects
 

No studies were located regarding neurological effects in humans or
 

animals after parenteral exposure to radium.
 

2.2.4.5 Developmental Effects
 

In a follow-up study of the first group of German patients injected
 

with radium-224 as therapy for tuberculosis when they were children (see
 

Section 2.2.4), it was found that the adult heights of these persons
 

were markedly lower than the heights of nontreated persons. This effect
 

was attributed to the formation of overcalcified "growth arrest plates"
 

during the radium-224 injections. The reduction was greatest for those
 

individuals who were the youngest at the age of injection; however, the
 

youngest children were given the highest doses of injected radium-224 in
 

μCi/kg (Spiess et al. 1985). The authors could not determine if this 

effect has a threshold but stated that the continued slowing of the 

growth rate long after irradiation suggests that some growth retardation 

may occur at very low doses of radium. 

2.2.4.6 Reproductive Effects
 

No studies were located regarding reproductive effects in humans or
 

animals following parenteral exposure to radium.
 

2.2.4.7 Genotoxic Effects
 

No studies were located regarding genotoxic effects in humans or
 

animals following parenteral exposure to radium.
 
18
 

2. HEALTH EFFECTS
 

2.2.4.8 Cancer
 

Bone tumors, primarily osteogenic sarcomas, have appeared in the
 

first group of German patients injected with radium-224 (see
 

Section 2.2.4) (Spiess et al. 1989). A total of 56 sarcomas have been
 

found; the expected number is 0.2 to 0.3 (Spiess et al. 1989). The
 

lowest total dose associated with a bone tumor was 6.4 μCi/kg 

(237 kBq/kg) given over two months (Mays and Spiess 1984). 

An elevated incidence of breast cancer has also been observed in
 

the female patients in this group (14 cases versus 4.1 to 6.1 expected).
 

Eight of these cases occurred among those injected as children, whereas
 

only 0.6 to 0.9 were expected. In patients injected as adults, the 6
 

observed cases are not significantly different from the 3.5 to 5.2 cases
 

expected (Spiess et al. 1989). This suggests that exposure to
 

radium-224 during childhood poses a much greater risk for the induction
 

of breast tumors than does exposure as an adult.
 

An elevated incidence of liver cancer has been seen in the first
 

series of German patients (6 versus 1.1 to 1.2 expected). Five cases of
 

kidney cancer have also been observed, compared with 2.4 to 2.6 expected
 

(Spiess et al. 1989); however, this increase is not statistically
 

significant. The authors suggest that these cancers may also have been
 

induced by the radium-224.
 

In the second group of German patients treated with radium-224 (see
 

Section 2.2.4), at lower injected doses, three malignant tumors in the
 

skeleton have been observed (versus 0.4 to 0.7 expected); two were
 

tumors of the bone marrow (a reticulum cell sarcoma and a plasmocytoma)
 

and one was a fibrosarcoma (Wick and Gossner 1989). One skeletal tumor,
 

a plasmocytoma, was observed among the controls, a group of 1,338
 

ankylosing spondylitis patients who were not treated with radiation
 

(Wick and Gossner 1989).
 

Of the Elgin State Hospital patients who received injections of
 

radium-226 (see Section 2.2.4), two patients developed bone sarcomas,
 

four developed head carcinomas, and a seventh patient had both types of
 

malignancy (statistical significance was not addressed) (Gustafson and
 

Stehney 1985).
 

Large experimental animal studies with parenterally administered
 

radium, primarily using dogs, but some using rats and mice, have
 

demonstrated that radium-224, radium-226, and radium-228 can induce bone
 

cancers and leukemias in these species (Evans et al. 1944; Humphreys
 

et al. 1985; Kofranek et al. 1985; Mays et al. 1987; Taylor et al.
 

1983). However, head carcinomas, such as those found in humans, were
 

not found in any of the species tested, indicating that this malignancy
 

was not induced under the conditions of these animal studies. The most
 
19
 

2. HEALTH EFFECTS
 

unexpected finding was the induction of intraocular melanomas in beagles
 

by radium-226 by Taylor et al. (1972). These tumors have not been seen
 

in any of the human studies.
 

2.3 TOXICOKINETICS
 

In radiation biology, the term "dose" has a specific meaning. Dose
 

refers to the amount of radiation absorbed by the organ or tissue of
 

interest per unit mass and is expressed in rads (grays). Estimation of
 

this radiation dose is sometimes accomplished by modeling the sequence
 

of events involved in the acquisition, deposition, clearance, and decay
 

of radium within the body. While based on the current understanding of
 

experimental data on radium toxicokinetics, different models make
 

different assumptions about these processes, thereby resulting in
 

different estimates of dose and risk. These models are described in
 

numerous reports including BEIR IV (1988), ICRP (1979), and Raabe et al.
 

(1983). In this section, the toxicokinetics of radium are described
 

based on the available experimental data rather than on descriptions
 

derived from models.
 

2.3.1 Absorption
 

2.3.1.1 Inhalation Exposure
 

The only study located on human absorption of radium after
 

inhalation exposure involved the accidental rupture of capsules
 

containing radium sulfate (presumed to be primarily radium-226), with
 

the resultant brief exposure of several laboratory workers (Marinelli
 

et al. 1953). Radium was deposited both in the lungs and the skeletons
 

of these individuals, indicating that some of the radium absorbed by the
 

lung had entered the systemic circulation, ultimately depositing in the
 

bones. Some of the radium, however, may have been coughed up and then
 

swallowed during the original exposure and then entered the systemic
 

circulation after being absorbed by the gut. The average half-life of
 

the decrease of gamma ray activity from the thorax was reported to be
 

about 120 days. The possibility of dermal exposure and consequent
 

absorption during this episode was not addressed.
 

No studies were located regarding the absorption of radium in
 

animals after inhalation exposure.
 

2.3.1.2 Oral Exposure
 

Based on a study of elderly human subjects (aged 63 to 83 years)
 

who ingested mock radium dial paint containing 224

RaS4, Maletskos et al.
 

(1966, 1969) have estimated that about 80% of the ingested radium was
 

promptly excreted via the feces during the first 10 days, and about 20%
 

was retained and distributed systemically. The feces to urine excretion
 
20
 

2. HEALTH EFFECTS
 

ratios remained high (about 30:1) during another phase of this study in
 

which similar subjects were given intravenous injections of radium-224.
 

This suggested that biliary excretion is probably involved and that
 

perhaps more than the estimated 20% of ingested radium was actually
 

absorbed. However, this topic was not addressed in the study.
 

Measurements of body radium acquired by adult and teenage males
 

solely from natural levels of radium in food and water indicated that
 

approximately twice the amount of ingested radium was retained by
 

younger males from one location, Lockport, Illinois (mean age:
 

16.6 years) than by older males in a penitentiary in Stateville,
 

Illinois (means of age groups: 27, 38 and 44 years) (Stehney and Lucas
 

1955). Among the prisoners, mean body radium content was increased with
 

the mean age of the men. However, boys from another location, Chicago,
 

Illinois (mean age: 16.6 years) had similar radium body contents to
 

that of the single Chicago adult man participating in this study. The
 

results of this study also suggested that the absorption of radium from
 

water was greater than that from food, based on excretion rates measured
 

in areas where either food or water was the predominant source of
 

radium. The authors acknowledged that these were speculations and not
 

clearly supportable by the results of their limited study.
 

In rats, the absorption of orally administered radium may be quite
 

low. At 400 to 500 days after administration, they retained 1 to 7% of
 

the ingested radium, primarily in the skeleton. In contrast, rats
 

intradermally injected with radium retained 77% of the administered
 

radium at 140 to 300 days after injection (Evans et al. 1944).
 

Differences seen in the results of these two studies could reflect
 

differences in time frame and/or the route of administration. The
 

probable influence of biliary excretion of orally administered radium
 

and the possibly slow rate of absorption of intradermally administered
 

radium from the site of injection may help account for these
 

differences.
 

2.3.1.3 Dermal Exposure
 

No studies were located regarding the absorption of radium in
 

humans or animals after dermal exposure.
 

2.3.2 Distribution
 

2.3.2.1 Inhalation Exposure
 

Based on the observations of Marinelli et al. (1953), immediately
 

after accidental exposure of humans to radium-226 (as the sulfate), the
 

major deposit of radium was in the lungs. This deposition decreased
 

with an average half-life of 118 days (±30 days). Elimination from the
 

lungs via the systemic circulation results in a continuous deposition in
 
21
 

2. HEALTH EFFECTS
 

the skeleton as well as distribution to soft tissue and the excretory
 

system. In addition, some of the radium salt may have been coughed up
 

and swallowed during the exposure episode.
 

It is assumed that radium that has been deposited in the lung as a
 

radium salt enters the systemic circulation either as that salt or as
 

individual radium atoms at a rate dependent upon the solubility and
 

chemical characteristics of the specific radium salt involved.
 

Subsequently, these salts or radium atoms would be systemically
 

transported in the same manner as radium acquired by oral or parenteral
 

administration. However, some of the radium in the lung could be
 

retained for a long time before this process is completed. The ultimate
 

distribution, many years after an inhalation exposure, would probably be
 

very similar to that of other routes of administration; that is, most of
 

the radium that was retained in the body would eventually be deposited
 

in the skeleton (Marinelli et al. 1953).
 

2.3.2.2 Oral Exposure
 

No studies have been located that specifically follow the
 

distribution of radium in humans or animals following oral exposure.
 

Distribution to the skeleton is assumed due to the findings of
 

osteosarcomas in the dial painter studies as well as the presence of
 

radium in their exhumed skeletal remains. The affinity for bone is
 

assumed to be related to its similarity to calcium (BIER IV 1988).
 

2.3.2.3 Dermal Exposure
 

No studies were located regarding the distribution of radium in
 

humans or animals following dermal exposure.
 

2.3.2.4 Other Routes of Exposure
 

Parenteral administration of radium to humans results in short-term
 

distribution to soft tissue which is rapidly followed by deposition of
 

most of the radium in the skeleton (BEIR IV 1988).
 

Radium, similarly to calcium, deposits in bone within those areas
 

where new bone mineral is being formed and also on all bone surfaces.
 

Radium remains in those areas of new bone formation, but the radium
 

deposits on bone surfaces eventually move into the depths of compact
 

bone as new bone matrix is deposited on top of them. In this deposition
 

process, short-lived radium-224 rapidly decays, leaving no radioactivity
 

within bone; whereas, long-lived radium-226 remains in the skeleton
 

indefinitely (Rowland 1966). Mays et al. (1975) have demonstrated that
 

the radon to radium ratio in bone increased with time after injection in
 

beagles.
 
22
 

2. HEALTH EFFECTS
 

Injected radium is deposited in the eye of the dog (Taylor et al.
 

1972) and to some extent in the human eye (Chmelevsky et al. 1988a).
 

2.3.3 Metabolism
 

Radium is an element and cannot be metabolized. In biological
 

systems in which radium salts are deposited, these compounds will
 

dissociate based on their solubility in that media. Radioactive decay
 

of the radium cation occurs over time.
 

2.3.4 Excretion
 

2.3.4.1 Inhalation Exposure
 

Based on a study of persons exposed to radium-226 during an
 

industrial accident which involved the rupture of a capsule containing
 

the insoluble salt radium sulfate (Marinelli et al. 1953), the excretion
 

of radium occurred in two phases. In the initial phase, 2 to 4% of the
 

estimated total body burden was excreted in the urine over a few days
 

and was attributed to the elimination of radium ingested during the
 

incident (due to the coughing up and swallowing of ingested radium).
 

(Fecal excretion was not monitored.) In the second phase, about
 

100 days after the exposure, the urinary excretion rate was higher than
 

predicted from the authors calculations (based on retention/excretion
 

models on dogs injected with radium chloride). This phase was
 

attributed to the presence of more radium in circulation than expected
 

as a consequence of a continual release of radium sulfate from the lung.
 

2.3.4.2 Oral Exposure
 

Following oral exposure to radium, excretion occurs in two phases.
 

In the first phase, approximately 80% of the ingested radium is rapidly
 

eliminated through the feces. In the slower second phase, most of the
 

20% that was absorbed into systemic circulation, is ultimately excreted
 

from the body via the feces (Maletskos et al. 1966, 1969). These
 

observations suggest that biliary excretion is probably involved;
 

however, no information has been located on that topic.
 

2.3.4.3 Dermal Exposure
 

No studies were located regarding the excretion of radium in humans
 

or animals after dermal exposure.
 

2.3.4.4 Other Routes of Exposure
 

Following intravenous administration of radium-224 to elderly human
 

subjects (63 to 83 years), the excretion of radium was primarily via the
 

feces, with fecal to urinary ratios of about 30-to-1 usually observed
 
23
 

2. HEALTH EFFECTS
 

(Maletskos et al. 1966, 1969). Although these observations suggest that
 

biliary excretion is involved, no data are available to verify that
 

assumption. The whole body retention was about 15% after 20 days.
 

The excretion of parenterally acquired radium from the human body
 

occurs in two phases; the first phase is very rapid, but the small
 

fraction that remains in the body is ultimately released very slowly,
 

presumably due to the turnover of bone matrix. An equation to describe
 

the retention of radium in the human body, derived by Norris et al.
 

(1955), predicts that the retention of radium 10 days after acquisition
 

will be 16%, dropping to 2.5% at 1 year, 0.76% at 10 years, and 0.43% at
 

30 years. A similar equation has been developed for dogs.
 

Seil et al. (1915) studied the excretion pattern of radium that had
 

been subcutaneously injected as the chloride salt into two dogs. The
 

resulting measurements varied widely over the next few days; however, it
 

was clear that there was a rapid initial elimination of radium in the
 

feces and that fecal to urinary excretion ratios were typically about
 

10-to-l.
 

In a study in dogs, it was shown that long-term retention of radium
 

is dependent upon age at injection, with younger dogs (3 months old)
 

that were still undergoing skeletal growth retaining more of the
 

injected activity than older dogs (18 months to 2 years old). However,
 

very young dogs (2 to 5 days old), undergoing major skeletal growth and
 

changes in bone shape lost most of their injected radium in the course
 

of these processes (Bruenger et al. 1983).
 

2.4 RELEVANCE TO PUBLIC HEALTH
 

Death. Death and decreased longevity have been reported in persons
 

who have had long-term exposure (approximately one or more years) to
 

radium. A 52-year-old man died following 5 years of consumption of
 

about 1,400 bottles of water containing radium at 2 μg per bottle, 

resulting in the total ingestion of approximately 2,800 μCi or 56 μCi/kg 

(2,074 kBq/kg) for a 50-kg man (Gettler and Norris 1933). However, the 

causes of death (jaw necrosis, brain absess, secondary anemia, and 

bronchopneumonia) can also be attributed to other etiologies. Case 

studies of women who died following ingestion of radium in dial paint 

were reported by Martland (1931). Deaths were attributed to anemia, 

necrosis of the jaw, and osteogenic sarcomas. A typical exposure 

duration was about two years. A 36-year-old chemist who had worked with 

radium for 14 years died of bronchopneumonia (Reitter and Martland 

1926). Autopsy results suggested to the authors that inhalation was the 

main route of radium intake. 
24
 

2. HEALTH EFFECTS
 

No deaths of patients (being treated mostly for arthritis) were 

reported to result from intravenous injections of radium at amounts up 

to 1,000 μCi or 14 μCi/kg (518 kBq/kg) (Proescher 1914). However, these 

patients may not have been followed clinically for more than a few 

months after these injections. 

Studies using mice have shown life-shortening effects of
 

intravenously injected radium-226 at high dose levels (2,000 to
 

4,000 μCi/kg or 74,074 to 148,148 kBq/kg) (Proescher and Almquest 1914). 

Injection of mice with radium-224 at lower levels (up to 60 μCi/kg or 

2,222 kBq/kg) did not result in life-shortening effects (Humphreys 

et al. 1985). 

Based on the results in humans and animals, lethality is a major
 

public health concern associated with long-term low-level or short-term
 

high-level exposure to radium. As discussed previously, total
 

cumulative intake appears to be the most important factor in relation to
 

health effects related to radium exposure.
 

Systemic Effects. Diseases of the hematopoietic tissues have been
 

reported in patients given repeated injections of radium-224. Anemia,
 

panmyelophthisis, and chronic myeloid leukemia were seen in excess of
 

the control levels in these cases (compared with a higher incidence of
 

acute leukemia in the control group) (Wick et al. 1986). Anemia has
 

also been reported in case studies of the radium dial painters (Martland
 

1931), but the disease patterns have not been clearly established
 

(Sharpe 1974).
 

Studies with mice injected with radium-226 at 24 μCi/kg 

(889 kBq/kg) have demonstrated reductions in the hemopoietic stem cells 

of the bone marrow for at least 100 days after radium acquisition 

(Schoeters and Vanderborght 1981). 

Ocular effects have not been reported in humans or animals exposed
 

to radium via inhalation, oral, or dermal routes. However, ocular
 

effects have been observed in both humans and animals injected with
 

radium. Cataracts were reported in 6% of the German patients who had
 

been injected with radium-224 as children (Chmelevsky et al. 1988a;
 

Stefani et al. 1985). In contrast, the incidence of cataracts in female
 

dial painters was not correlated with total radium intake or age at
 

first exposure, nor was there a difference in appearance times between
 

high and low total radium intakes (Adams et al. 1983). However, the
 

dial painters were exposed orally, the isotope was mainly radium-226,
 

and very few of these dial painters were exposed when younger than
 

15 years of age. Any of these factors may account for the difference
 

between the results observed in these two studies.
 
25
 

2. HEALTH EFFECTS
 

In beagle dogs, intravenously injected radium-226 resulted in
 

melanosis and intraocular melanoma formation at the lower doses and a
 

loss of pigment at the higher doses (Taylor et al. 1972). In this
 

study, deposition of radium was found in the melanin granules of
 

pigmented cells and rodlike organelles of the tapetum of the eye (a
 

structure that humans do not have). Although this process cannot take
 

place in humans, these results further suggest that the eye may be a
 

target for absorbed radium in exposed humans.
 

Other Systemic Effects. Information on other systemic effects is
 

not available for humans or animals exposed to radium via inhalation,
 

oral, or dermal exposure. However, tooth breakage has been reported to
 

occur in the German patients who were injected with radium-224
 

(Sonnabend et al. 1986). The incidence of these dental fractures was
 

highest (25%) in persons who had been injected at 16 to 20 years of age,
 

as compared with 12% in the total group of persons injected at age
 

20 years and younger, and 2% in persons injected when they were 21 years
 

old and older.
 

Immunological Effects. Evidence of radium's potential effects on
 

the human immune system was presented by Reitter and Martland (1926) in
 

the case study of a chemist who developed acute leukopenia after working
 

with radium for 14 years. Autopsy revealed almost total absence of
 

granular leukocytes, leukoblastic groups, and lymphoid tissue in the
 

bone marrow. Similarly, Martland (1931) described the development of
 

leukopenia in the radium dial painters.
 

Schoeters et al. (1983) showed a reduction in the number of
 

peripheral white blood cells of mice at 400 days after an
 

intraperitoneal injection of radium-226. These observations suggest
 

that immunological effects may be an important area of concern for
 

persons occupationally exposed to radium.
 

Cancer. In humans, radium-224 is known to induce bone sarcomas,
 

and it is strongly suspected of inducing breast cancer in females who
 

received this isotope when younger than 21 years of age at total doses
 

greater than 12 μCi/kg (444 kBq/kg). Liver and kidney cancers are also 

possibly induced by radium-224 (Spiess et al. 1989). 

Bone sarcomas are known to be induced by both radium-226 and
 

radium-228, while carcinomas of the bones enclosing the mastoid air
 

cells and paranasal sinuses are known to be induced by exposure to
 

radium-226. These carcinomas are believed to be caused by radon, a
 

gaseous daughter product of radium-226, which migrates from the location
 

where it was formed and becomes trapped within air cells in these
 

structures. Here the subsequent decay products of radon irradiate the
 

sensitive cells on the surfaces, and this irradiation is thought to
 
26
 

2. HEALTH EFFECTS
 

induce the malignant change. Breast cancer and multiple myeloma were
 

found to be elevated in female dial painters, but these effects may be
 

the consequence of the external radiation from the radioactive paint
 

that was used by these workers (Rowland et al. 1989; Stebbings et al.
 

1984).
 

In Great Britain, radium dial painters with higher total radium-226
 

intakes and who were younger than 30 years of age at the start of
 

painting showed an excess of breast cancers (Baverstock and Papworth
 

1989). External gamma ray exposure to the radioactive paint could also
 

have been the cause of cancer in this population.
 

In experimental animals, bone cancer has been the most prominent
 

consequence of radium incorporation and has been found in all species
 

tested.
 

It should be noted that leukemia, which is often induced in humans
 

by irradiation of marrow cells, has not been observed to occur in excess
 

in the studies of the radium-irradiated populations (i.e., dial
 

painters; patients receiving intravenous injections) above the numbers
 

expected for nonirradiated populations (Baverstock and Papworth 1985;
 

Spiers et al. 1983; Spiess et al. 1989).
 

2.5 BIOMARKERS OF EXPOSURE AND EFFECT
 

Biomarkers are broadly defined as indicators signaling events in
 

biologic systems or samples. They have been classified as markers of
 

exposure, markers of effect, and markers of susceptibility (NAS/NRC
 

1989).
 

A biomarker of exposure is a xenobiotic substance or its
 

metabolite(s) or the product of an interaction between a xenobiotic
 

agent and some target molecule or cell that is measured within a
 

compartment of an organism (NAS/NRC 1989). The preferred biomarkers of
 

exposure are generally the substance itself or substance-specific
 

metabolites in readily obtainable body fluid or excreta. However,
 

several factors can confound the use and interpretation of biomarkers of
 

exposure. The body burden of a substance may be the result of exposures
 

from more than one source. The substance being measured may be a
 

metabolite of another xenobiotic (e.g., high urinary levels of phenol
 

can result from exposure to several different aromatic compounds).
 

Depending on the properties of the substance (e.g., biologic half-life)
 

and environmental conditions (e.g., duration and route of exposure), the
 

substance and all of its metabolites may have left the body by the time
 

biologic samples can be taken. It may be difficult to identify
 
27
 

2. HEALTH EFFECTS
 

individuals exposed to hazardous substances that are commonly found in
 

body tissues and fluids (e.g., essential mineral nutrients such as
 

copper, zinc and selenium). Biomarkers of exposure to radium are
 

discussed in Section 2.5.1.
 

Biomarkers of effect are defined as any measurable biochemical,
 

physiologic, or other alteration within an organism that, depending on
 

magnitude, can be recognized as an established or potential health
 

impairment or disease (NAS/NRC 1989). This definition encompasses
 

biochemical or cellular signals of tissue dysfunction (e.g., increased
 

liver enzyme activity or pathologic changes in female genital epithelial
 

cells), as well as physiologic signs of dysfunction such as increased
 

blood pressure or decreased lung capacity. Note that these markers are
 

often not substance specific. They also may not be directly adverse but
 

can indicate potential health impairment (e.g., DNA adducts).
 

Biomarkers of effects caused by radium are discussed in Section 2.5.2.
 

A biomarker of susceptibility is an indicator of an inherent or
 

acquired limitation of an organism's ability to respond to the challenge
 

of exposure to a specific xenobiotic. It can be an intrinsic genetic or
 

other characteristic or a preexisting disease that results in an
 

increase in absorbed dose, biologically effective dose, or target tissue
 

response. If biomarkers of susceptibility exist, they are discussed in
 

Section 2.7, "POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE."
 

2.5.1 Biomarkers Used to Identify or Quantify Exposure to Radium
 

Exposure to radium can be determined by use of a whole body counter
 

to measure the presence of gamma radiation emitted by radium (Toohey
 

et al. 1983). Radium levels can also be measured in urine, feces, and
 

other biological media by means of gamma-ray spectroscopy (Lloyd et al.
 

1983).
 

2.5.2 Biomarkers Used to Characterize Effects Caused by Radium
 

Humans have not been shown to develop specific adverse effects as a
 

result of exposure to radium. Osteogenic sarcoma and cataracts are
 

associated with radium exposure but can also result from other causes.
 

Similarly, chromosomal aberrations may result from radium exposure as
 

well as from other factors such as cigarette smoking or occupational
 

exposure to solvents.
 

Attempts to correlate the estimated total intake of radium with 

observed health effects, especially bone cancer, have been conducted at 

the Argonne National Laboratory (Gustafson and Stehney 1985). For 

example, Rundo et al. (1986) have estimated that the lowest total intake 

level of radium associated with a malignancy (bone sarcoma) was 60 μCi 

(2,222 kBq) or 1.03 μCi/kg (38 kBq/kg) based on an estimated 58-kg body 
28
 

2. HEALTH EFFECTS
 

weight for a woman. If data associated with exposed populations were
 

fully analyzed, levels of radium in human tissue might be a good
 

predictor of at least the potential for developing bone cancer.
 

However, there is expected to be some degree of uncertainty, as in cases
 

of persons with high levels of exposure to radium (such as some of the
 

dial painters, the case of the chemist described by Reitter and Martland
 

and the man who drank 1,400 bottles of "Radithor"), who did not develop
 

bone cancer (Gettler and Norris 1933; Martland 1931; Reitter and
 

Martland 1926).
 

2.6 INTERACTIONS WITH OTHER CHEMICALS
 

No data have been located which evaluate the health effects of
 

radium in any of its isotopic forms in combination with any other
 

chemicals or radionuclides.
 

2.7 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE
 

The available studies suggest that persons who are exposed to
 

radium during childhood or adolescence may be at greater risk from the
 

potential health effects of radium, especially tooth breakage
 

(Section 2.2.4.2), reduction in bone growth (Section 2.2.4.5), and
 

breast tumors (Section 2.2.4.8). There may also be a subpopulation of
 

humans who are genetically more susceptible to the development of bone
 

cancer (Floyd et al. 1983). Patients with Paget's disease have 10 to
 

100 times the risk of bone sarcoma than the general population.
 

2.8 ADEQUACY OF THE DATABASE
 

Section 104(i)(5) of CERCLA, directs the Administrator of ATSDR (in
 

consultation with the Administrator of EPA and agencies and programs of
 

the Public Health Service) to assess whether adequate information on the
 

health effects of radium is available. Where adequate information is
 

not available, ATSDR, in conjunction with the National Toxicology
 

Program (NTP), is required to assure the initiation of a program of
 

research designed to determine these health effects (and techniques for
 

developing methods to determine such health effects) of radium.
 

The following categories of data needs have been identified by a
 

joint team of scientists from ATSDR, NTP, and EPA. They are defined as
 

substance-specific informational needs that, if met would reduce or
 

eliminate the uncertainties of human health assessment. In the future,
 

the identified data needs will be evaluated and prioritized, and a
 

substance-specific research agenda will be proposed.
 
29
 

2. HEALTH EFFECTS
 

2.8.1 Existing Information on the Health Effects of Radium
 

The existing data on health effects of inhalation, oral, and dermal
 

exposure of humans and animals to radium are summarized in Figure 2-l.
 

The purpose of this figure is to illustrate the existing information
 

concerning the health effects of radium. Each dot in the figure
 

indicates that one or more studies provide information associated with
 

that particular effect. The dot does not imply anything about the
 

quality of the study or studies. Gaps in this figure should not be
 

interpreted as "data needs" information.
 

Figure 2-l indicates whether information on the endpoint of a
 

particular health effect is available for a specific route and duration
 

of exposure for radium. Some information was located concerning human
 

inhalation or oral exposure to radium, and no information was located
 

concerning effects following dermal exposure to radium by humans. The
 

only information available for animals is an intermediate-duration study
 

in rats conducted via the oral route that resulted in cancer. There is
 

virtually no information on noncancer endpoints from animal studies. As
 

discussed in previous sections, most available information on radium is
 

the result of studies using parenteral administration.
 

In general, the adverse effects of radium are believed to be the
 

consequence of the radiation emitted from the element itself and its
 

daughter products. Because there is already a considerable amount of
 

information on the effects of radiation on humans and animals deri-ved
 

from studies on the effects of the atomic bomb and of therapeutic x-ray
 

and gamma-ray treatments of malignancies, the experimental animal
 

studies with radium have made no attempt to duplicate this information.
 

They have instead concentrated on radium's most sensitive endpoint,
 

cancer. For example, it can be predicted that the beta and gamma rays
 

emitted by a radium source will produce local radiation burns and tissue
 

damage when the source is placed on human or animal skin, hence there
 

have been no valid reasons to conduct such studies with radium.
 

2.8.2 Identification of Data Needs
 

Acute-Duration Exposure. There is no information available on the
 

effects of acute-duration exposure to radium by humans or animals via
 

inhalation, oral, or dermal exposure. The available toxicokinetic data
 

suggest that radium can be absorbed and retained after inhalation and
 

oral exposure. Although there are some toxicokinetic data that provide
 

information on the retention of inhaled radium sulfate in the lung, it
 

is not clear whether this compound and other salts of radium would
 

remain in the lung long enough after acute-duration exposure to cause
 

local effects such as lung cancer or other carcinogenic or
 

noncarcinogenic systemic effects.
 

31
 

2. HEALTH EFFECTS
 

Animal studies conducted via the inhalation, oral, and dermal routes of
 

exposure for this duration period would be useful since the potential
 

short-term effects of such exposure as well as effects that could emerge
 

years later, such as cancer, are not known.
 

Intermediate-Duration Exposure. There are no data on intermediate-


duration exposure of humans to radium via the inhalation, oral, or
 

dermal routes. There are no data on animals exposed via inhalation or
 

the dermal route. The only information located was a very limited
 

20-day oral study in rats that resulted in osteogenic sarcomas. The
 

data were not sufficient to calculate an MEL by any route. The
 

available toxicokinetic data show that radium can be absorbed and
 

retained after inhalation or oral exposure, although quantitative data
 

are lacking. It would be useful to have information on the effects of
 

intermediate-duration exposure to radium via inhalation, oral, and
 

dermal routes in order to help assess the potential health effects of
 

exposure to radium in the vicinity of hazardous waste sites and other
 

settings, and to evaluate the possibility of long-range effects such as
 

cancer that may emerge years later.
 

Chronic-Duration Exposure and Cancer. A case report is available
 

on human chronic-duration exposure to radium via inhalation and
 

indicates that acute leukopenia, bronchopneumonia, and death occurred in
 

a chemist after 14 years of exposure. A case report is also available
 

on a man who regularly consumed bottles of a "rejuvenating" tonic
 

containing radium for about 5 years, resulting in effects described as
 

necrosis of the jaw, abscess of the brain, secondary anemia,
 

bronchopneumonia, and death. (Each of these causes of death can also be
 

attributed to other etiologies.) Numerous studies have followed the
 

dial painters who ingested radium, and effects reported in these studies
 

include anemia, bone sarcomas, head carcinomas, and death. Although
 

dermal exposure to radium also occurred in these cases, skin effects
 

have not been reported. No data are available on chronic-duration
 

exposure to radium by animals via any route of exposure. The available
 

data were not considered to be adequate to calculate an MEL for any
 

route of exposure. Animal studies on the noncarcinogenic effects of
 

chronic-duration exposure to radium via inhalation, oral, and dermal
 

exposure would be useful in assessing the potential health risks of
 

humans chronically exposed to low levels of radium in the vicinity of
 

hazardous waste sites and other settings.
 

Bone cancer has occurred in humans after chronic-duration oral
 

exposure to radium and in rats that were orally exposed in an
 

intermediate duration study (20 days). It would be useful to have
 

carcinogenicity information from animal studies conducted via
 
32
 

2. HEALTH EFFECTS
 

inhalation, oral, and dermal exposure since humans in the vicinity of
 

hazardous waste sites and other settings would be exposed to radium via
 

all routes of exposure.
 

Genotoxicity. Neither in vitro nor in vivo genotoxicity studies
 

have been located for radium. A battery of in vitro genotoxicity tests
 

may provide useful information on the mechanism of carcinogenicity for
 

radium.
 

Reproductive Toxicity. No studies were located on reproductive
 

effects of radium in humans or animals via inhalation, oral, or dermal
 

exposure. Animal studies using the oral route would be especially
 

useful in evaluating the potential for these effects in human
 

populations exposed to high levels of radium in drinking water (eg.,
 

more than 5 pCi). Studies using dermal and inhalation exposure would
 

also be useful, since these are also probable routes of human exposure
 

to radium in the vicinity of hazardous waste sites and other settings.
 

Developmental Effects. No information has been located on
 

developmental effects in humans or animals resulting from inhalation,
 

oral, or dermal exposure to radium. It was observed that radium-224
 

injected into young children markedly reduced their adult height due to
 

radiation damage to the growth plate in the long bones. Animal studies
 

via inhalation, oral, and dermal exposure would be useful in determining
 

if radium, like calcium, can cross the placenta and enter fetal
 

circulation, and can have adverse effects upon fetal development.
 

Immunotoxicity. Studies that assess the potential effects of
 

radium on the immune system of orally or dermally exposed humans have
 

not been located. The case report of a chemist exposed to radium
 

primarily via inhalation for 14 years reported leukopenia and the almost
 

total absence of granular leukocytes, leukoblastic groups, and lymphoid
 

tissue in the bone marrow. No studies on animals exposed via
 

inhalation, oral, or dermal routes have been located. A study reporting
 

a reduction in peripheral white blood cells in intraperitoneally
 

injected rats has been located. The reported observations suggest that
 

immunological effects may be a concern for humans exposed to radium. A
 

battery of immune function tests conducted in animals via inhalation and
 

the oral and dermal routes would provide useful information relative to
 

this concern.
 

Neurotoxicity. No reports of neurotoxicity resulting from
 

inhalation, oral, or dermal exposure were located in the available human
 

and animal studies. No further information appears to be needed at this
 

time.
 
33
 

2. HEALTH EFFECTS
 

Epidemiological and Human Dosimetry Studies. Two large studies in
 

Germany that follow radium-224 injected patients are being conducted by
 

Spiess and by Wick and Gossner, and the radium study being conducted at
 

Argonne National Laboratory has developed a large data base with
 

information on the radium dial painters, patients who were medically
 

treated with radium, and other persons exposed to radium. These studies
 

will be of value in determining any effects that may be experienced by
 

these aging populations. Additional data are not needed at this time.
 

Biomarkers of Exposure and Effect. Currently, human exposure to
 

radium can be assessed by the presence of radioactivity in the body as
 

measured by a whole body counter and in biological fluids such as blood
 

or urine by gamma spectroscopy.
 

Effects specifically related to radium exposure have not been
 

identified. Studies to identify potential biomarkers of radium's subtle
 

effects would be useful as indicators that immediate mitigation of
 

exposure to radium is warranted or that serious effects such as bone
 

cancer may follow.
 

Absorption, Distribution, Metabolism, and Excretion. Quantitative
 

data on the absorption of radium after intake via any exposure route are
 

very limited. No data were located on the absorption of radium after
 

dermal exposure. Information on laboratory workers exposed to radium
 

during an industrial accident indicates that absorption can occur via
 

the inhalation route. A study in elderly human subjects indicated that
 

at least 20% of the ingested radium-224 in mock radium dial paint was
 

absorbed and retained. No studies were located on the absorption of
 

radium by animals after inhalation or dermal exposure. A study of
 

orally exposed rats indicated that retention of radium at 400 to
 

500 days was 1% to 7% of the administered dose. Further studies to
 

investigate the absorption and retention of radium after inhalation,
 

oral, and dermal exposure would be helpful in elucidating the relative
 

risks associated with exposure by each route.
 

No studies have been located regarding the distribution of radium
 

in humans after oral or dermal exposure. Due to the findings of
 

osteosarcomas in the radium dial painters and in a study in rats and the
 

presence of radium in the exhumed skeletal remains of the dial workers,
 

it is assumed to deposit in the bone after oral exposure. Data from a
 

study of laboratory workers exposed via inhalation during an accident
 

and a case report of a chemist exposed for 14 years also indicate that
 

most radium was deposited in the skeleton. In the case of the chemist,
 

no measurable levels of activity were found in the liver,
 

gastrointestinal tract, heart, or kidneys. Information on radium
 
34
 

2. HEALTH EFFECTS
 

distribution following inhalation, oral and dermal exposure would be
 

useful in helping to determine the potential target organs in persons
 

exposed via each route.
 

Radium salts, such as radium sulfate, can be dissociated to Ra2+
 

and the corresponding anion. However, radium is an element and cannot
 

be metabolized. It is changed over time by the decay of its isotopic
 

forms, each at its own rate. Therefore, no information is needed in
 

this area.
 

Excretion data in orally and parenterally exposed humans indicate
 

that feces is the major route of radium excretion and that biliary
 

excretion is probably also involved. Some urinary elimination also
 

takes place in persons exposed via inhalation, oral, and dermal routes.
 

Continued excretion for months after exposure has been attributed to the
 

release of radium from the lungs in persons exposed via inhalation and
 

from the turnover of bone matrix in persons exposed orally or via
 

parenteral administration. It would be useful to have quantitative
 

information on the excretion patterns of radium administered to animals
 

via inhalation, oral, and dermal administration and to more clearly
 

elucidate the role of biliary excretion in the elimination process.
 

Comparative Toxicokinetics. There are currently not enough data to
 

evaluate any potential species-related differences in response to radium
 

exposure by any route. It would be useful to have information on which
 

animal models most closely approximate humans in this regard in order to
 

help interpret the relevance to humans of any toxicity findings in
 

animal studies. Studies on the toxicokinetics of radium following
 

inhalation, oral, and dermal exposure are needed to compare the
 

different routes of exposure.
 

2.8.3 On-going Studies
 

In Germany, Spiess is following about 900 patients who were
 

injected with radium-224 immediately after World War II. Wick and
 

Gossner are following a larger group of about 1,500 patients injected
 

more recently with lower doses of radium-224. These studies are
 

currently active, and summaries of their data are published
 

periodically.
 

The Center for Human Radiobiology at the Argonne National
 

Laboratory is the repository for all data accumulated in the United
 

States on radium-exposed persons. This study has recently been severely
 

reduced in magnitude, but the records on 5784 cases remain available at
 

the laboratory (Rundo et al. 1986).
 
35
 

2. HEALTH EFFECTS
 

Two large studies of radium and other bone-seeking radionuclides in
 

dogs were conducted at the University of Utah (Wrenn et al. 1986) and at
 

the University of California at Davis (Raabe et al. 1981, 1983).
 

Results of both projects are still being analyzed.
 

37
 

3. CHEMICAL AND PHYSICAL INFORMATION
 

3.1 CHEMICAL IDENTITY
 

The chemical formula and available identification numbers for
 

radium are listed in Table 3-1.
 

3.2 PHYSICAL AND CHEMICAL PROPERTIES
 

Table 3-2 lists important physical properties of radium and
 

selected radium compounds. Radioactive properties of the four
 

naturally-occurring radium isotopes are listed in Table 3-3. In
 

addition to the naturally occurring isotopes, there are 12 other known
 

isotopes of radium. The principal decay schemes of the uranium and
 

thorium decay series that produce the naturally-occurring radium
 

isotopes are presented in Figure 3-l.
 





43
 

4. PRODUCTION, IMPORT, USE, AND DISPOSAL
 

4.1 PRODUCTION
 

Between 1913 and 1920, about 70 g of radium were produced by
 

Pittsburgh refineries (Blaufox 1988). No current information on
 

production of radium has been located.
 

4.2 IMPORT
 

No current information has been located on the importation of
 

radium. In the late 1970's, Zaire and Canada were the world's principal
 

producers of radium (HSDB 1988). No quantitative data regarding U.S.
 

imports of radium from those countries have been located.
 

4.3 USE
 

Radium has been used as a radiation source for treating neoplastic
 

diseases, as a radon source, in radiography of metals, and as a neutron
 

source for research (Weast 1985; Windholz 1983).
 

Until the 196Os, radium was a component of the luminous paints used
 

for watch and clock dials, instrument panels in airplanes, military
 

instruments, and compasses (Blaufox 1988).
 

During the early years of this century, radium was used in potions
 

with supposed curative properties. This practice was discontinued by
 

the early 1930's (Blaufox 1988; Macklis 1990).
 

4.4 DISPOSAL
 

Because radium is a radioactive substance, disposal of wastes
 

containing radium is controlled by a number of federal and state
 

regulations (see Chapter 7). Both the EPA and the Nuclear Regulatory
 

Commission have promulgated regulations for land disposal of these
 

wastes detailing containment requirements and permissible exposure
 

levels based on radioactivity.
 

On a global level, the amount of radium released to the environment
 

OK disposed of through industrial use is considered to be insignificant
 

compared to the natural occurrence of radium in the environment. Radium
 

is present in the wastes of uranium mining and refining processes, and
 

disposal of these wastes is regulated.
 

45
 

5. POTENTIAL FOR HUMAN EXPOSURE
 

5.1 OVERVIEW
 

Radium is a naturally-occurring metal that is almost ubiquitous in
 

soils, water, geologic materials, plants, and foods at low
 

concentrations. The utilization of radium, uranium, and fossil fuels
 

has resulted in the redistribution of radium in the environment by way
 

of air, water, and land releases. The concentration of radium in
 

natural water is usually controlled by adsorption-desorption reactions
 

with minerals and rocks and by the solubility of radium-containing
 

minerals. In addition, radium is constantly being produced by the
 

radioactive decay of its precursors, uranium, and thorium. Radium does
 

not degrade other than by radioactive decay at rates which are specific
 

to each of four naturally-occurring isotopes. The concentrations of
 

radium-226 and radium-228 in drinking water are generally low, but there
 

are specific geographic regions where high concentrations of radium
 

occur due to geologic sources. Radium may be bioconcentrated and
 

bioaccumulated by plants and animals, and it is transferred through food
 

chains from lower trophic levels to humans.
 

The frequency of NPL hazardous waste sites in the United States at
 

which radium has been found at higher than background levels can be seen
 

in Figure 5-l.
 

5.2 RELEASES TO THE ENVIRONMENT
 

5.2.1 Air
 

The combustion of coal may be the most important mechanism for
 

releasing radium into the atmosphere. The mean concentration of
 

radium-226 in coal is on the order of 1 pCi/g (0.04 Bq/g). When
 

combusted, radium may volatilize, then condense onto coal fly ash
 

particles, which in turn may be released from power plants as fugitive
 

emissions. The concentrations of radium-226 in fly ash have ranged from
 

1 to 10 pCi/g (0.04 to 0.4 Bq/g) (Coles et al. 1978; Eisenbud and Petrow
 

1964; Morris and Bobrowski 1979).
 

The radium-228 content of fly ash has varied from 1.8 to 3.1 pCi/g
 

(0.07 to 0.12 Bq/g) (Eisenbud and Petrow 1964). If it is assumed that
 

the total radium content of fly ash is 5 pCi/g (0.19 Bq/g), and that 1%
 

of the ash generated at all coal-fired power plants in the United States
 

escapes into the atmosphere, then an order-of-magnitude estimate of the
 

amount of radium released each year would be 2.2 Ci (81,000,OOO kBq)
 

(Roy et al. 1981). Eisenbud and Petrow (1964) estimated that a single
 

lOOO-megawatt coal-fired power plant will discharge about 28 mCi
 

(1,037,OOO kBq) of total radium per year. Radium-226 has been detected
 

in soils in industrial regions at levels up to 8.1 pCi/g (0.30 Bq/g)
 

(Jaworowski and Gryzbowska 1977).
 

47
 

5. POTENTIAL FOR HUMAN EXPOSURE
 

Global releases of radium-226 by the combustion of coal have been
 

estimated as 150 Ci (5,550,000,000 kBq) per year (Jaworowski et al.
 

1971). It has also been observed that radium-226 concentrations in
 

glacial ice samples collected in Europe have increased by a factor of
 

100 during the last 80 years. The source of these elevated levels of
 

radium may have been emissions from fossil fuels (Jaworowski et al.
 

1971).
 

Another potential source of atmospheric radium is particulate
 

matter created by uranium mining and milling operations. However, no
 

information was located on estimated releases or atmospheric
 

concentrations.
 

5.2.2 Water
 

The most significant water-related releases of radium may be from 

the leaching of uranium mine tailings and from the release of ore 

-processing effluents generated by leaching, decantation, and filtration 

processes. Approximately 97 million tons of mine tailings that contain 

an estimated 60,000 Ci (2.2 x l09

 kBq) of radium-226 have been 

stockpiled at the surface in the western United States (Kaufmann et al. 

1976). It has been estimated that 10 million tons of uranium mine 

tailings are generated each year in Canada (Kalin 1988). Laboratory 

extraction studies (Havlik et al. 1968a, 1968b) have demonstrated that 

radium-226 may leach from solid wastes, particularly by acidic 

wastewaters. Surface runoff and leachate from uranium mine tailings 

have contained radium-226 ranging from 38 to 116 pCi/L (1.4 to 4.3 Bq/L) 

(Kalin 1988; Swanson 1985). Untreated uranium milling effluent has 

contained radium-226 at up to 2.2 μCi/L (81 kBq/L) (Sebesta et al. 

1981). In the past, leachate from mine tailings containing radium-226 

concentrations of 53 to 292 pCi/L (2 to 11 Bq/L) has been deep-well 

injected (Kaufmann et al. 1976). Approximately 2,000 to 3,000 Ci 

(74,000,000,000 to 111,000,000,000 kBq) of total radioactivity were 

released to the subsurface by two uranium mills in New Mexico. No 

information was located on the total amount of radium released to the 

environment by water-related discharges. As discussed in Section 5.4.2, 

however, concentrations of radium-226 and radium-228 found in surface 

and ground water sources have generally been low. 

5.2.3 Soils
 

Land releases of radium are related to atmospheric fallout of coal
 

fly ash (see Section 5.2.1). For example, elevated radium-226
 

concentrations in snow have been detected near a coal-fired power plant
 

in Poland (Jaworowski et al. 1971). Other land releases may include the
 

disposal of coal fly ash, lime slurry derived from water softening
 

processes, and uranium mine tailings and associated wind-blown dusts.
 
48
 

5. POTENTIAL FOR HUMAN EXPOSURE
 

However, no information was located on the total amount of land-released
 

radium.
 

5.3 ENVIRONMENTAL FATE
 

Radium may be transported in the atmosphere in association with
 

particulate matter. It exists primarily as a divalent ion in water, and
 

its concentration is usually controlled by adsorption-desorption
 

mechanisms at solid-liquid interfaces and by the solubility of radiumcontaining
 

minerals. Radium does not degrade in water other than by
 

radioactive decay at rates that are specific to each isotope. Radium
 

may be readily adsorbed by earth materials; consequently, it is usually
 

not a mobile constituent in the environment. It may be bioconcentrated
 

and bioaccumulated by plants and animals, and it is transferred in food
 

chains from lower trophic levels to humans.
 

5.3.1 Transport and Partitioning
 

5.3.1.1 Air
 

Radium may be transported in the atmosphere by the movement of
 

particulate matter derived from uranium and coal utilization (see
 

Section 5.2.1). These fugitive emissions would be subject to
 

atmospheric dispersion, gravitational settling and wash-out by rain.
 

No data were located on the residence time of radium in the
 

atmosphere or its deposition rate. However, data for other elements
 

adsorbed to particulate matter indicate that the residence time for fine
 

particles is about 1 to 10 days (EPA 1982b; Keitz 1980). Radium may,
 

therefore, be subject to long-range transport in the atmosphere.
 

5.3.1.2 Water
 

Radium in water exists primarily as a divalent ion (Ra2+) and has 

chemical properties that are similar to barium, calcium, and strontium. 

The solubility of radium salts in water generally increases with 

increased pH levels. The solubilities of radium sulfate and carbonate 

are low; the solubility constants for crystalline RaSO, and RaCO, have 

been estimated as 5.495 x 10-11 mole/L and 5.01 x 10-9 mole/L,respectively 

(Langmuir and Riese 1985). Radium nitrate, chloride, and iodate are very 

soluble in water (Ames and Rai 1978). However, the concentration of radium in 

water is usually controlled by adsorptiondesorption reactions at solid-liquid 

interfaces which are in turn influenced by pH (see Section 5.3.1.3) or by the 

dissolution and coprecipitation of minerals that contain radium (EPA 1985a; 

Langmuir and Riese 1985). The tendency for radium to coprecipitate with barite, 

and sparingly soluble barium sulfate, as (BaRa)SO4 is well known. Moreover,
 

water treatment by adsorption and water-softening techniques are thought
 
49
 

5. POTENTIAL FOR HUMAN EXPOSURE
 

to be effective in reducing radium in untreated drinking water (Watson
 

et al. 1984). Therefore, it is likely that radium in water does not
 

migrate significantly from the area where it is released or generated
 

(EPA 1985a). Limited field data also support the generalization that
 

radium is not mobile in groundwater (Kaufmann et al. 1976; Swanson
 

1985).
 

5.3.1.3 Aquifers, Sediments, and Soils
 

Radium in water may be readily adsorbed by sediments, soils, and
 

aquifer components. It has been experimentally demonstrated that radium
 

can be adsorbed by soils and sediments (Benes and Strejc 1986; Landa and
 

Reid 1982), ferric hydroxide and quartz (Benes et al. 1984; Valentine
 

et al. 1987), kaolinite and montmorillonite (Benes et al. 1985), and
 

muscovite and albite (Benes et al. 1986).
 

Partition coefficients such as adsorption constants (Kd) describe 

the tendency of chemicals to partition to solid phases from water. 

Adsorption constants for inorganic ions such as Ra2+ cannot be predicted 

a priori because they depend on the type of adsorbent, the pH of the 

water, and the presence of other ions in solution. Kd values for sand 

have varied from 18 to 1,742 mL/g in the pH range of 7.4 to 8.3 (Benes 

et al. 1984; Valentine et al. 1987). Kd values for clay minerals and 

other common rock-forming minerals have ranged from 2,937 to 90,378 mL/g 

in alkaline solutions (Benes et al. 1985, 1986). Similarly, Kds for 

soils in alkaline solutions have ranged from 214 to 467 mL/g (Ames and 

Rai 1978). Adsorption constants based on field studies with lake 

sediments have varied from 205 to 15,833 mL/g (Swanson 1985). The 

magnitude of these adsorption constants indicate that partitioning to 

solid surfaces is a major removal mechanism of radium from water. 

Swanson (1985) concluded that about 90% of the radium-226 released by 

uranium-mine effluent to two small lakes was adsorbed by the lake 

sediments and algae-detrital material. 

The removal of Ra2+ by adsorption has been attributed to ion 

exchange reactions, electrostatic interactions with potential determining 

ions at mineral surfaces, and surface-precipitation with 

BaSO4. The adsorptive behavior of Ra2+ is similar to that of other 

divalent cationic metals in that it decreases with an increase in pH 

and is subject to competitive interactions with other ions in solution 

for adsorption sites. In the latter case, Ra2+ is more mobile in 

groundwater that has a high total dissolved solids (TDS) content. It 

also appears that the adsorption of Ra2+ by soils and rocks may not be a 

completely reversible reaction (Benes et al. 1984, 1985; Landa and Reid 

1982). Hence, once adsorbed, radium may be partially resistant to 

removal, which would further reduce the potential for environmental 

release and human exposure. 
50
 

5. POTENTIAL FOR HUMAN EXPOSURE
 

5.3.1.4 Plants and Animals
 

Transfer from soil to plants. Radium in the soil may be readily 

absorbed by plants, depending on the specific plant type and soil (Rayno 

1983). Elevated concentrations of radium-226 above background levels 

have been detected in areas where radium and/or uranium was mined or 

processed (Kalin 1988; Rayno 1983; Tracy et al. 1983; Watson et al. 

1984). The partitioning of radium-226 to plants from soils has been 

estimated by measuring the ratio of radium activity (or concentration) 

in the plant mass to that in the host soil. Soil-plant transfer 

coefficients or concentration factors have ranged from 1.1 x 10-3 to 6.5 

(Rayno 1983; Tracy et al. 1983). Watson et al. (1984) concluded that a 

reasonable radium-226-concentration factor for fruits is 3 x 10-3 and 

that 0.1 describes the partitioning of radium-226 to forage and hay. An 

unweighted mean concentration factor for grain was 0.63. No information 

was located on soil-to-plant transfers for radium-228; however, its 

properties in this regard may be similar to those of radium-226. 

Transfer from plants to cattle. There is a potential for human 

exposure to radium by the consumption of beef and milk derived from 

cattle who graze on forage grown in soils containing radium. The mean 

ratio of radium-226 in milk to that in the animal's diet has been 

estimated to be 3.8 x 10-3 (Watson et al. 1984). A similar ratio or 

transfer coefficient for flesh was 6.8 x 10-3 . 

Transfer from water to aquatic organisms. Aquatic organisms such
 

as fish, snails, clams, and algae can bioaccumulate radium from water.
 

Bioconcentration factors (BCFs) for fish living in streams or lakes
 

receiving uranium-processing waste effluent have ranged from 1 to 60 for
 

flesh portions, and from 40 to 1,800 in bone samples (Markose et al.
 

1982; Swanson 1985). It has been proposed that bottom-feeding organisms
 

ingest suspended solids containing adsorbed radium, then are in turn
 

consumed by larger predatory fish.
 

5.3.2 Transformation and Degradation
 

5.3.2.1 Air
 

Pure metallic radium oxidizes when exposed to air, but radium
 

compounds suspended in air are not subject to transformation or
 

degradation mechanisms.
 
51
 

5. POTENTIAL FOR HUMAN EXPOSURE
 

5.3.2.2 Water
 

Radium in water exists as a stable divalent ion; it probably does
 

not hydrolyze nor is it significantly influenced by oxidation-reduction
 

reactions (Ames and Rai 1978). The solubility of radium salts is
 

increased with increasing pH levels.
 

5.3.2.3 Soil
 

Radium in soils and sediment does not biodegrade nor participate in
 

any chemical reactions that transform it into other forms. The only
 

degradation mechanism operative in air, water, and soil is radioactive
 

decay. Radium has 16 known isotopes (see Chapter 3), but only 4 occur
 

naturally (Radium-223, -224, -226, and -228). The half-life of
 

radium-226 is 1,620 years. The half-lives of radium-228, radium-223,
 

and radium-224 are 5.77 years, 11.4 days, and 3.64 days, respectively.
 

5.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT
 

Radium is a naturally-occurring metal and is almost ubiquitous at
 

low concentrations in air, water, soil, rocks, and food. The median
 

concentrations of radium-226 and radium-228 in drinking water are
 

generally low, but there are geographic areas where higher
 

concentrations of radium are known to occur. The utilization of coal
 

and uranium has resulted in re-distributing radium in the environment,
 

but the overall effects appear to be small. Estimated levels of average
 

human exposure to radium of non-occupational populations are presented in
 

Table 5-l.
 

5.4.1 Air
 

Dust samples collected from the atmosphere of New York City were 

found to contain radium-226 at 8 x 10-5 pCi/m3

 (3.0 x 10-6 Bq/m3) and 

radium-228 at 1.5 x 10-4 pCi/m3

 (5.6 x 10-6 Bq/m3) (Eisenbud and Petrow 

1964). No other published data on ambient concentrations of radium in 

the atmosphere were located. 

5.4.2 Water
 

Radium is a naturally-occurring and fairly ubiquitous metal at low
 

concentrations in water and rock-forming minerals. It has been
 

estimated that the total mass of radium-226 in the earth's oceans is
 

about 150 tons (Fremlin and Abu Jarad 1980). The occurrence of radium
 

in ground, surface, and finished (treated) drinking water has been
 

assessed (Aieta et al. 1987; Cech et al. 1988; EPA 1985a; Hess et al.
 

1985; Longtin 1988; Lucas 1985; Michel and Cothern 1986; Watson et al.
 

1984). In general, shallow wells tend to have lower radium-226
 

concentrations than deeper wells, and the total content in municipal
 

53
 

5. POTENTIAL FOR HUMAN EXPOSURE
 

(treated) water supplies is lower than that in raw well water (Watson
 

et al. 1984). The radium content of surface water is usually very low.
 

Radium-226 generally ranges from 0.1 to 0.5 pCi/L (0.004 to 0.019 Bq/L)
 

(Hess et al. 1985). Based on 990 random samples of drinking water from
 

ground water sources, the average population-weighted concentrations of
 

radium-226 and radium-228 in the United States (excluding Hawaii) were
 

about 0.91 pCi/L (0.034 Bq/L) and 1.41 pCi/L (0.052 Bq/L), respectively
 

(Longtin 1988). Approximately 90% of these samples contained radium-226
 

at less than 1 pCi/L (0.04 Bq/L); similarly, about 90% contained
 

radium-228 at less than 1 pCi/L (0.04 Bq/L). (These were not
 

necessarily the same water sources.) However, there were approximately
 

200 public water supplies with radium-226 activities after treatment
 

that were in excess of the regulatory maximum contaminant level (MCL) of
 

5 pCi (0.19 Bq) total radium/L (Hess et al. 1985). The mean radium-226
 

activity of the supplies in excess of the MCL was about 10 pCi/L
 

(0.37 Bq/L).
 

A survey on the occurrence of radium-228 in municipal water
 

supplies in Illinois, Iowa, Missouri, and Wisconsin indicated that the
 

activity of this isotope may range from 0.3 to 32.0 pCi/L (11.1 to
 

1,180 mBq/L) (Lucas 2985), while Michel and Cothern (1986) reported that
 

typical concentrations are less than 1 pCi/L (37 mBq/L).
 

There are few data on the occurrence of radium-224 in water. It
 

has been speculated that the activity of this isotope could approach 30
 

to 40 pCi/L (1,110 to 1,480 mBq/L) (EPA 1985a).
 

Data on the presence of radon in groundwater can be used as a guide
 

to the presumably corresponding presence of radium in the same source.
 

Based on descriptions of aquifer composition or lithology and data from
 

state water-resource agencies, counties with potentially high levels of
 

radon in groundwater have been identified by Michel (1987). These
 

estimates indicate that the U.S. counties with the highest levels of
 

radium would be found in many areas of the Western third of the country,
 

including large areas of California, Nevada, Idaho, and Montana.
 

Wisconsin and Minnesota would also have high levels. In the East, the
 

Appalachian Mountain region including almost all of Maine and New
 

Hampshire would have high levels, as well as a large section of central
 

Florida. It is important to note that quantitative estimates are not
 

available, and the potentially "high" values for radon and radium imply
 

only a comparison to other areas, not necessarily a risk to human health
 

or the environment.
 

5.4.3 Soil
 

The mean concentration of radium-226 in 356 surface soil samples
 

collected from 0 to 6 cm in 33 states was 1.1 pCi/g (0.041 Bq/g) (Myrick
 

et al. 1981). This mean concentration is very similar to those reported
 
54
 

5. POTENTIAL FOR HUMAN EXPOSURE
 

for typical igneous rocks (1.3 pCi/g or 0.048 Bq/g), sandstone
 

(0.71 pCi/g or 0.026 Bq/g), shale (1.1 pCi/g or 0.041 Bq/g), and
 

limestone (0.42 pCi/g or 0.016 Bq/g) (Eisenbud 1973). The concentration
 

of radium-226 in soils in Northern Italy was reported to average
 

0.72 pCi/g [range: 0.08 to 3.8 pCi/g (0.003 to 0.14 Bq/g)] (DeBortoli
 

and Gaglione 1972), excluding regions with extremely high levels of
 

natural radioactivity (no data presented).
 

The concentrations of radium-226 in soils that were contaminated by
 

mining or milling activities have ranged from less than 1 to 3,700 pCi/g
 

(0.037 to 137 Bq/g) (Kalin 1988; Landa 1984; Tracy et al. 1983). No
 

information was located on the occurrence of the other radium isotopes
 

in soil or rocks.
 

The presence of uranium in soil can be used as an indication of
 

occurrence of radium and radon in the same location. Based on
 

geological reports and data synthesized from the National Uranium
 

Resource Evaluation (NURE) program, areas with potentially high radon
 

levels in soil gas have been identified by Michel (1987). These areas
 

would have correspondingly high soil radium levels, although
 

quantitative estimates are not available. These uranium "hot spots"
 

occur with more frequency in the Western third of the United States, and
 

include large areas of California and Idaho. High concentrations have
 

been found in Wisconsin and Minnesota and a very dense area has been
 

identified in western Missouri/eastern Kansas. In the East, high levels
 

appear generally along the Appalachian mountains and near industrialized
 

sites. High levels have also been found in the northern to central
 

sections of Florida.
 

5.4.4 Other Media
 

Radium-226 may occur in many different foods, and reported
 

activities have varied considerably. The mean radium-226 contents of
 

diets in 11 cities in the United States were estimated to be 0.52 to
 

0.73 pCi/kg of food consumed (0.019 to 0.027 Bq/kg) (Eisenbud 1973).
 

Estimates of the mean concentrations of radium-226 in milk and beef are
 

0.23 pCi/L (0.009 Bq/L) and 0.22 pCi/kg (0.008 Bq/kg) (fresh weight),
 

respectively, in the United States (Watson et al. 1984). No information
 

was located on the occurrence of radium-228 in food.
 

5.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE
 

Major sources of exposure to radium by the general population are
 

the consumption of drinking water and food (Table 5-l). Of the many
 

radionuclides found in nature, radium is considered to be one of the
 

most important because of its wide occurrence in groundwater, and
 

because it, like calcium, is retained in bone tissues (Aieta et al.
 

1987). Bone cancer is the greatest health risk from exposure to radium.
 
55
 

5. POTENTIAL FOR HUMAN EXPOSURE
 

Based on assumptions about the concentration of radium in drinking water
 

provided by utilities, the size of the population consuming this water,
 

and the associated risk of cancer, Hess et al. (1985) estimated that the
 

average concentration of radium in drinking water may cause cancer in
 

941 persons per year in the United States. The risk of exposure to
 

radium in food is uncertain because of the variability in diets and in
 

the radium-226 content of foods. It has been estimated that the yearly
 

intake of radium-226 for food in New York City is on the order of 640
 

pCi (24 Bq) (Eisenbud 1973).
 

Levels of occupational exposure to radium are difficult to assess.
 

Workers who are occupationally exposed to radium through the mining and
 

processing of uranium are also probably exposed simultaneously to
 

uranium itself, thorium, and radon by inhalation and probably dermal
 

exposure. Nielson and Rogers (1981) suggested that inhalation exposures
 

during uranium mining and milling operations involving crushing,
 

grading, or blasting are the most significant routes of exposure. There
 

is also some concern about ingesting dust at processing plants (Dixon
 

1985). It has also been suggested that inhalation of
 

fugitive emissions from mine tailings could be locally significant
 

(Ruttenber et al. 1984), but radium-specific data were not located.
 

5.6 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES
 

The populations at greatest risk of exposure from the consumption
 

of drinking water with a high radium content are located in the Piedmont
 

and Coastal Plain province in New Jersey, North Carolina, South
 

Carolina, and Georgia and parts of Minnesota, Iowa, Illinois, Missouri,
 

and Wisconsin (Hess et al. 1985; Longtin 1988). It has been estimated
 

that about 600,000 people consume water with radium-226 concentrations
 

in excess of the MCL (5 pCi/L or 0.19 Bq/L) in Illinois, Iowa, Missouri,
 

and Wisconsin. Isolated occurrences of high radium-226 have also been
 

detected in Arizona, New Mexico, Texas, Mississippi, Florida, and
 

Connecticut. There is also a high probability of exposure to high
 

radium-228 concentrations in many of the states listed above in addition
 

to parts of California, Colorado, Idaho, Montana, New Mexico, and
 

Wyoming (Michel and Cothern 1986).
 

It has been suggested that uranium miners and millers who are in
 

chronic contact with dust are at risk. However, such workers are
 

simultaneously exposed to several radionuclides and no generalization
 

specific to radium can be made.
 

5.7 ADEQUACY OF THE DATABASE
 

Section 104(i)(5) of CERCIA, directs the Administrator of ATSDR (in
 

consultation with the Administrator of EPA and agencies and programs of
 

the Public Health Service) to assess whether adequate information on the
 
56
 

5. POTENTIAL FOR HUMAN EXPOSURE
 

health effects of radium is available. Where adequate information is
 

not available, ATSDR, in conjunction with the National Toxicology
 

Program (NTP), is required to assure the initiation of a program of
 

research designed to determine the health effects (and techniques for
 

developing methods to determine such health effects) of radium.
 

The following categories of data needs have been identified by a
 

joint team of scientists from ATSDR, NTP, and EPA. They are defined as
 

substance-specific informational needs that, if known, would reduce or
 

eliminate the uncertainties of human health assessment. Each data need
 

discussion highlights the availability, or absence, of the relevant
 

exposure information. A statement that reflects the importance of
 

identified data needs is also included. In the future, these data needs
 

will be evaluated and prioritized, and a substance-specific research
 

agenda will be proposed.
 

5.7.1 Identification of Data Needs
 

Physical and Chemical Properties. Although some of the physical
 

and chemical properties of radium and radium compounds have not been
 

determined, many of those that are needed to evaluate its behavior in
 

the environment are known. The adsorption-desorption behavior of radium
 

with geologic materials depends on the specific system under study and
 

should be determined on a case-by-case basis. Also, thermodynamic and
 

kinetic data for solid solution formation are scarce. Research in this
 

area would facilitate modeling the fate of radium in water.
 

Production, Import, Use, and Disposal. Radium is apparently used
 

only in small quantities (e.g., in laboratories) in the United States.
 

The quantities discharged to the environment from this source are
 

probably insignificant compared to naturally-occurring radium. However,
 

data on actual amounts of radium currently in use and amounts disposed
 

of as waste would be useful in estimating human exposure potential.
 

Environmental Fate. Studies of releases of radium that result from
 

uranium mining and processing would be helpful to fully assess the total
 

amount and environmental fate of radium released to the environment.
 

Field data on the mobility of radium in groundwater would also be
 

helpful in attempts to predict its potential for occurrence in sources
 

of drinking water at remote sites.
 

Bioavailability from Environmental Media. Data on the absorption
 

of radium from environmental media via inhalation, oral, and dermal
 

exposure would be useful in determining potential risks for organisms
 

(humans, animals and plants) that have been exposed to radium in air,
 

soil, or natural waters.
 
57
 

5. POTENTIAL FOR HUMAN EXPOSURE
 

Food Chain Bioaccumulation. The existing information indicates
 

that radium may be transferred through the food chain from lower trophic
 

levels to humans. Additional monitoring studies in areas where radium
 

occurs naturally at high concentrations in soil would be helpful to
 

determine if this pathway is a significant route of exposure. The
 

transfer of radium-228 from soils through the food chain has not been
 

assessed.
 

Exposure Levels in Environmental Media. The concentration of
 

radium-226 in drinking water has been the subject of numerous studies,
 

and average values are reasonably well known. It appears that emphasis
 

could be given to monitoring radium-226 concentrations in regions where
 

high concentrations are expected to occur ("hot spots"), such as regions
 

with high levels of natural radioactivity, in the vicinity of uranium
 

mining and milling operations, and at NPL and other hazardous waste
 

sites. Information on the occurrence of radium in the atmosphere would
 

also be useful in helping to predict exposure via inhalation.
 

The occurrence of radium-228 has not been as well established, and
 

additional data would be helpful, particularly in geologic regions where
 

high concentrations are likely. There is virtually no information on
 

the occurrence and levels of radium-223 and radium-224 in drinking
 

water. The occurrence and levels of any of the isotopes of radium in
 

food are highly variable, and additional data would facilitate exposure
 

estimates.
 

Exposure Levels in Humans. There is no information available on
 

the general background levels of radium in human tissue. Information on
 

these levels, especially in the skeleton, would be especially useful as
 

a means to monitor continuing exposure to radium.
 

Exposure Registries. A national exposure registry for persons
 

exposed to radium was not located but would be useful in relating
 

factors such as age, sex, season, geography, regulations, environment
 

and other factors to measured exposure concentrations and health
 

outcomes.
 

5.7.2 On-going Studies
 

The EPA is presently conducting a survey called the National
 

Inorganics and Radionuclides Survey (NIRS). This study has been ongoing
 

since 1981, and preliminary reports have been published. These
 

data are still being analyzed for the establishment of revised interim
 

drinking water regulations.
 

59
 

6. ANALYTICAL METHODS
 

The purpose of this chapter is to describe the analytical methods
 

that are available for detecting and/or measuring and monitoring radium
 

in environmental media and in biological samples. The intent is not to
 

provide an exhaustive list of analytical methods that could be used to
 

detect and quantify radium. Rather, the intention is to identify well
 

established methods that are used as the standard methods of analysis.
 

Many of the analytical methods used to detect radium in environmental
 

samples are the methods approved by federal agencies such as EPA and the
 

National Institute for Occupational Safety and Health (NIOSH). Other
 

methods presented in this chapter are those that are approved by a trade
 

association such as the Association of Official Analytical Chemists
 

(AOAC) and the American Public Health Association (APHA). Additionally,
 

analytical methods are included that refine previously used methods to
 

obtain lower detection limits and/or to improve accuracy and precision.
 

6.1 BIOLOGICAL MATERIALS
 

The presence of radium in biological materials or environmental
 

samples is generally determined by virtue of its radioactivity. Except
 

in the laboratory where radium compounds have been isolated and
 

determined for a certain purpose, determination of radium compounds in
 

biological and environmental samples is relatively rare. As a Group IIA
 

alkaline earth element, radium is similar in its chemical behavior to
 

other members of that group, especially its nearest neighbor, barium.
 

For example, radium tends to precipitate as the sulfate, which is the
 

basis for its isolation for chemical analysis by coprecipitation with
 

barium sulfate. Furthermore, radium associates with calcium in living
 

systems and accumulates in bone. The determination of radium compounds
 

or specific isotopes is usually accomplished by a separation procedure,
 

followed by quantitative analysis of total radium based on its
 

radioactivity.
 

Radium is determined in both biological and environmental samples
 

by the emission of ionizing radiation from its radioisotopes (alphaeemitting radium-223, radium-224, and radium-226, as well as
 

beta-emitting radium-228) and from its daughter products. Gamma-ray
 

spectrometry of the gamma rays emitted by decay products of radium can
 

also be used to measure radium. One of the most important examples is
 

the measurement of gamma rays emitted by 214Bi (Davis et al. 1987).
 

Intermediate loss of radon gas in the decay chain can be troublesome in
 

this kind of measurement. One method of radium measurement in bone
 

collects the radioactive radon-222 gas product of the decay of radium226, and its radioactivity is measured and extrapolated back to the
 

concentration of radium-226 (Walton et al. 1959).
 
60
 

6. ANALYTICAL METHODS
 

A method has been developed to measure the rate of elimination of
 

radon in exhaled breath (Stehney et al. 1955). Based on the assumption
 

that 70% of the radon from fixed body radium is exhaled, this test can
 

be used to calculate approximate levels of the body burden of radium.
 

Some analytical methods for the determination of radium in
 

biological materials are given in Table 6-l. It is important to note
 

that the major contributions of these studies are descriptions of sample
 

preparation techniques rather than advances in alpha or gamma
 

spectrometry.
 

6.2 ENVIRONMENTAL SAMPLES
 

Because small amounts of radium radionuclides in environmental
 

samples may be regarded as hazardous, it is usually necessary to detect
 

very small quantities of radium which may require processing large
 

quantities of sample (Quinby-Hunt et al. 1986). This introduces
 

possibilities for contamination and sample loss. Specifically, in the
 

case of water samples, sorption of the radionuclide to container walls
 

and to suspended matter may be important sources of error.
 

Significant concentrations of contaminant radium may be
 

submicromolar. Therefore, radiochemical separations are commonly
 

employed that make use of a carrier, a nonradioactive element with
 

chemical properties similar to those of radium. For radium, barium is
 

the element of choice, and radium is coprecipitated from solution with
 

barium sulfate, BaSO4. Correction for losses in the precipitation
 

procedure may be made by adding a tracer consisting of an isotope of
 

radium not expected in the sample and noting its recovery at the end of
 

the analytical procedure. The isotope radium-223 can be used for this
 

purpose.
 

Radium is commonly determined in environmental samples by the
 

emission of alpha particles from the radium-226 radioisotope. Beta-


emitting radium-228 can also be measured. Measurement of the
 

radioactive radon-222 gas product of the decay of radium-226 can be used
 

to give the concentration of radium-226. Gamma-ray spectroscopy of
 

daughter radioisotopes such as 214Bi can also be used to determine
 

radium.
 

Because of the low penetrating power of alpha particles, special
 

counters are required to assay alpha activity. These include gas-filled
 

counters (thin window or internal, proportional counters), scintillation
 

counters, and semiconductor detectors. In addition, a very thin sample
 

is required to prevent the sample itself from absorbing alpha particles.
 

62
 

6. ANALYTICAL METHODS
 

A promising method has been developed for measuring radium-226
 

concentrations in water samples of one liter size (Whittaker 1986). All
 

nongaseous alpha-emitting radionuclides are coprecipitated with barium
 

sulfate and iron hydroxide, followed by counting alpha emissions from
 

the precipitate. A count at 3 hours followed by one at 7 days is used
 

to measure radium-226.
 

Some analytical methods for the determination of radium in
 

environmental samples are given in Table 6-2.
 

6.3 ADEQUACY OF THE DATABASE
 

Section 104(i)(5) of CERCLA, directs the Administrator of ATSDR (in
 

consultation with the Administrator of EPA and agencies and programs of
 

the Public Health Service) to assess whether adequate information on the
 

health effects of radium is available. Where adequate information is
 

not available, ATSDR, in conjunction with the National Toxicology
 

Program (NTP), is required to assure the initiation of a program of
 

research designed to determine the health effects (and techniques for
 

developing methods to determine such health effects) of radium.
 

The following categories of data needs have been identified by a
 

joint team of scientists from ATSDR, NTP, and EPA. They are defined as
 

substance-specific informational needs that, if known, would reduce or
 

eliminate the uncertainties of human health assessment. Each data need
 

discussion highlights the availability, or absence, of the relevant
 

exposure information. A statement that reflects the importance of
 

identified data needs is also included. In the future, these data needs
 

will be evaluated and prioritized, and a substance-specific research
 

agenda will be proposed.
 

6.3.1 Identification of Data Needs
 

Methods for Determining Biomarkers of Exposure and Effect. As
 

discussed above, the presence of radium in biological materials is
 

usually determined by virtue of its radioactivity. Methods available
 

for the determination of radioactivity in biological materials include
 

alpha spectroscopy and gamma spectrometry, which is more convenient, but
 

generally less sensitive, than alpha spectroscopy (Joshi 1987). It
 

would be useful to have additional data on the sensitivity and accuracy
 

of the methods that are currently in use.
 

Effects specifically associated with radium exposure have not been
 

identified. The development of methods for detecting biomarkers of
 

radium's effects would be useful.
 

64
 

6. ANALYTICAL METHODS
 

Methods for Determining Parent Compounds and Degradation Products
 

in Environmental Media. It would be useful to have data on the
 

sensitivity and accuracy of methods that are currently used to determine
 

radium in environmental media. In addition, continued development of
 

sensitive and accurate methods and instrumentation that would minimize
 

problems with background and contamination would be useful in
 

determining radium levels in environmental media. It would also be
 

useful to develop portable, compact instruments to conduct field
 

analyses with optimum sensitivity and accuracy.
 

6.3.2 On-going Studies
 

Refinements continue to be made in detecting radioactivity from
 

radium isotopes and their daughter products. These developments include
 

better, more sensitive detectors and more efficient data handling
 

systems. Substantial improvements may be anticipated in the area of
 

high resolution gamma spectroscopy. Research is underway to improve
 

sample preparation and separation to give more sensitive analysis and
 

better speciation. Because of the demands of cleanup programs including
 

Superfund II, the Formerly Utilized Sites Remedial Action Program, and
 

the Uranium Mill Tailings Remedial Action Program, research is underway
 

to increase sample output and to decrease time and costs per sample
 

(Donivan et al. 1987).
 
65
 

7. REGULATIONS AND ADVISORIES
 

International and national regulations and guidelines pertinent to
 

human exposure to radium are summarized in Table 7-l. Recommendations
 

for radiation protection for people in the general population as a
 

result of exposure to radiation in the environment are found in the
 

Federal Radiation Guidance (FRC 1960) and ICRP No. 26 (ICRP 1977).
 

National guidelines for occupational radiation protection are found in
 

the "Federal Radiation Protection Guidance for Occupational Exposure"
 

(EPA 1987). This guidance for occupational exposure supercedes
 

recommendations of the Federal Radiation Council for occupational
 

exposure (FRC 1960). The new guidance presents general principles for
 

the radiation protection of workers and specifies the numerical primary
 

guides for limiting occupational exposure. These recommendations are
 

consistent with the ICRP (ICRP 1977).
 

The basic philosophy of radiation protection is the concept of
 

AURA (As Low As Reasonably Achievable). As a rule, all exposure should
 

be kept as low as reasonably achievable, and the regulations and
 

guidelines are meant to give an upper limit to exposure. Based on the
 

primary guides (EPA 1987a), guides for Annual Limits on Intake (ALIs)
 

and Derived Air Concentrations (DACS) have been calculated (EPA 1988).
 

The AL1 is defined as "that activity of a radionuclide which, if inhaled
 

or ingested by Reference Man (ICRP 1975), will result in a dose equal to
 

the most limiting primary guide for committed dose" (EPA 1988; ICRP
 

1979) (see Appendix B). The DAC is defined as "the concentration of
 

radionuclide in air which, if breathed by Reference Man (ICRP 1975) for
 

a work-year, would result in the intake of one AL1 (EPA 1988). The ALIs
 

and DACs refer to occupational situations but may be converted to apply
 

to exposure of persons in the general population by application of
 

conversion factors (Table 7-l).
 



69
 

8. REFERENCES
 

∗	 Adams EE, Brues AM, Anast GA. 1983. Survey of ocular cataracts in 

radium dial workers. Health Phys 44:73-79. 

∗	 Aieta EM, Singley JE, Trussell AR, et al. 1987. Radionuclides in 

drinking water: An overview. J AWWA 79:144-152. 

Albert RE, Shore RE. 1986. Carcinogenic effects of radiation on the
 

human skin. In: Upton AC, Albert RE, Burns FJ, et al., eds. Radiation
 

carcinogenesis. New York, NY: Elsevier Science Publishing Co., 335­

345.
 

∗	 Ames LL, Rai D. 1978. Radionuclide interactions with soil and rock 

media. Vol. 1: Processes influencing radionuclide mobility and 

retention. Las Vegas, NV: U.S. Environmental Protection Agency, Office 

of Radiation Programs. EPA 520/6-78-007. 

∗	 APHA. 1985a. Radium in water by precipitation method 705. In: 

Greenberg AE, Trussell RR, Clesceri LS, eds. Standard methods for the 

examination of water and wastewater. 16th ed. Washington DC: 

American Public Health Association, 652-656. 

∗	 APHA. 1985b. Radium 226 by radon in water (soluble, suspended and 

total) - method 706. Standard methods for the examination of water and 

wastewater. 16th ed. Washington, DC: American Public Health 

Association, 657-667. 

∗	 APHA. 1985c. Radium 228 (soluble) (tentative) - method 707. Standard 

methods for the examination of water and wastewater. 16th ed. 

Washington, DC: American Public Health Association, 667-670. 

∗	 Archer VE. 1977. Occupational exposure to radiation as a cancer 

hazard. Cancer 39(suppl):1802-1806. 

∗	 ASTM. 1988a. Standard method for sampling surface soil for 

radionuclides - Method C 998-83. 1988 annual book of ASTM standards. 

Vol. 11.03: Atmospheric analysis; occupational safety and health. 

Philadelphia, PA: American Society for Testing and Materials, 512-514. 

∗	 ASTM. 1988b. Standard method for soil preparation for the 

determination of radionuclides - Method C 999-83. 1988 annual book of 

ASTM standards. Vol. 11.03: Atmospheric analysis; occupational safety 

and health. Philadelphia, PA: American Society for Testing and 

Materials, 515-516. 

∗	 Cited in text. 
70
 

8. REFERENCES
 

∗	 ASTM. 1988c. Standard test methods for radionuclides of radium in 

water - Method D 2460-70. 1988 annual book of ASTM standards, Vol. 

11.02: Water and Environmental Technology. Philadelphia, PA: American
 

Society for Testing and Materials, 660-662.
 

Aub JC, Evans Rd, Gallagher DM, et al. 1938. Effects of treatment on
 

radium and calcium metabolism in the human body. Ann Intern Med
 

11:1443-1463.
 

∗	 Barnes D, Bellin J, DeRosa C, et al. 1987. Reference dose (RFD): 

Description and use in health risk assessments. Vol I, Appendix A: 

Integrated risk information system supportive documentation. 

Washington, DC: U.S. Environmental Protection Agency, Office of Health 

and Environmental Assessment. EPA/600/8-86/032a. 

∗	 Baverstock KF, Papworth DG. 1985. The U.K. radium luminiser survey: 

Significance of a lack of excess leukaemia. Strahlentherapie [Sonderb] 

80:22-26. 

∗	 Baverstock KF, Papworth DG. 1989. The U.K. radium luminiser survey. 

Br J Radio1 21:72-76. 

∗	 Bean JA, Isacson P, Hahne RM, et al. 1982. Drinking water and cancer 

incidence in Iowa: II. Radioactivity in drinking water. Am J 

Epidemiol 116:924-932. 

∗	 BEIR IV. 1988. Radium. In: Health risks of radon and other 

internally deposited alpha-emitters. Washington, DC: National Academy 

Press, 176-244. 

∗	 Benes P, Strejc P. 1986. Interaction of radium with freshwater 

sediments and their mineral components: IV. Wastewater and riverbed 

sediments. Journal of Radioanalytical and Nuclear Chemistry 99:407-422. 

Benes P, Sebesta F, Sedlacek J, et al. 1983. Particulate forms of
 

radium and barium in uranium mine waste waters and receiving river
 

waters. Water Res 17:619-624.
 

∗	 Benes P, Strejc P, Lukavec Z. 1984. Interaction of radium with 

freshwater sediments and their mineral components: I. Ferric hydroxide 

and quartz. Journal of Radioanalytical and Nuclear Chemistry 82:275­

285.
 

∗	 Benes P, Borovec Z, Strejc P. 1985. Interaction of radium with 

freshwater sediments and their mineral components: II. Kaolinite and 

montmorillonite. Journal of Radioanalytical and Nuclear Chemistry 

89:339-351. 
71
 

8. REFERENCES
 

∗	 Benes P, Borovec Z, Strejc P. 1986. Interaction of radium with 

freshwater sediments and their mineral components: III. Muscovite and 

feldspar. Journal of Radioanalytical and Nuclear Chemistry 98:91-103. 

∗	 Blaufox MD. 1988. Radioactive artifacts: Historical sources of modern 

radium contamination. Semin Nucl Med 18:46-64. 

∗	 Brandon WF, Saccomanno G, Archer VE, et al. 1978. Chromosome 

aberrations as a biological dose-response indicator of radiation 

exposure in uranium mines. Radiat Res 76:159-171. 

∗	 Bruenger FW, Smith JM, Atherton DR, et al. 1983. Skeletal retention 

and distribution of 226Ra and 239Pu in beagles injected at ages ranging 

from 2 days to 5 years. Health Phys 44(Suppl 1):513-527. 

Brues AM. 1971. Radiation thresholds. Arch Environ Health 22:690-691.
 

∗	 Burns B, Clulow FV, Cloutier NR, et al. 1987. Transfer coefficient of 

226Ra from food to young weaned meadow voles, Microtus pennsvlvanicus, 

in the laboratory. Health Phys 52:207-211. 

Calabrese EJ. 1977. Excessive barium and radium-226 in Illinois
 

drinking water. J Environ Health 39:366-369.
 

∗	 Cech I, Lemma M, Kreitler CW, et al. 1988. Radium and radon in water 

supplies from the Texas Gulf coastal aquifer. Water Res 22:109-121. 

CFR. Code of Federal Regulations. Washington, DC: Office of Federal
 

Register, National Archives and Records Administration.
 

∗	 CHEMNAME Database. 1989. Dialog Information Services, Inc., Palo Alto, 

CA. February 1989. 

Chmelevsky D, Kellerer AM, Spiess H, et al. 1985. A proportional 

hazards analysis of bone sarcoma rates in German 224radium patients. 

Strahlentherapie [Sonderb] 80:32-37. 

∗	 Chmelevsky D, Mays CW, Spiess H, et al. 1988a. An epidemiological 

assessment of lens opacifications that impaired vision in patents 

injected with radium-224. Radiat Res 1151238-257. 

Chmelevsky D, Kellerer AM, Land CE, et al. 1988b. Time and dose
 

dependency of bone-sarcomas in patients injected with radium-224.
 

Radiat Environ Biophys 27:103-114.
 

Clark C. 1987. Physicians, reformers and occupational disease: The
 

discovery of radium poisoning. Women Health 12:147-167.
 
72
 

8. REFERENCES
 

CLC. 1988. Coordinated List of Chemicals. U.S. Environmental
 

Protection Agency, Office of Research and Development, Washington DC.
 

Clifford D, Vijjeswarapu W, Subramonian S. 1988. Evaluating various
 

adsorbents and membranes for removing radium from groundwater. J AWWA
 

(July):94-104.
 

Cloutier RJ. 1980. Florence Kelley and the radium dial painters.
 

Health Phys 39:711-716.
 

∗	 Coles DG, Ragaini RC, Ondov JM. 1978. Behavior of natural 

radionuclides in western coal-fired power plants. Environ Sci Technol 

12:442-446. 

Cosandey M, Wenger P. 1977. Long-term radium retention in contaminated
 

dial painters. Health Phys 33:221-225.
 

Crawford DJ, Leggett RW. 1980. Assessing the risk of exposure to
 

radioactivity. Am Sci 68:524-536.
 

∗	 Davis NM, Hon R, Dillon P. 1987. Determination of bulk radon emanation 

rates by high resolution gamma ray spectroscopy. In: Graves B, ed. 

Radon, radium, and other radioactivity in ground water. Chelsea, MI, 

Lewis Publishers, 111-122. 

∗	 De Bortoli M, Gaglione P. 1972. Radium-226 in environmental materials 

and foods. Health Phys 22:43-48. 

Dingman PV. 1987. Waterbury and the hazards of prolonged radiation.
 

Orthopaedic Review 16:352/113-361/122.
 

∗	 Dixon DW. 1985. Occupational exposure to natural radiation. Sci Total 

Environ 45:111-120. 

∗	 Donivan S, Hollenbach M, Costello M. 1987. Rapid determination of 

thorium-230 in mill tailings by alpha spectrometry. Anal Chem 

59:2256-2558. 

∗	 D'Souza TJ, Mistry KB. 1970. Comparative uptake of thorium-230, 

radium-226, lead-210, and polonium-210 by plants. Radiation Botany 10: 

293-295. 

∗	 Dvorak V, Kofranek V, Malatova I, et al. 1978. Osteogenic sarcomas in 224 226
 mice after Ra or Ra administrations. In: Muller WA, Ebert HG,
 

eds. Biological effects of 224Ra. Brussels, Belgium: CEC, 109-119.
 

∗	 Eisenbud M. 1973. Natural radioactivity. In: Environmental 

radioactivity. New York, NY: Academic Press, 159-174. 
73
 

8. REFERENCES
 

∗	 Eisenbud M, Petrow HG. 1964. Radioactivity in the atmospheric 

effluents of power plants that use fossil fuels. Science 144:288-289. 

EPA. 1979. Radiological impact caused by emissions of radionuclides
 

into air in the United States - preliminary report. Washington, DC:
 

U.S. Environmental Protection Agency, Office of Radiation Programs (ANR460). EPA 520/7-79-006. NTIS No. PB80-122336.
 

∗	 EPA. 1982a. U.S. Environmental Protection Agency. Federal Register 

47:54598-54621. 

∗	 EPA. 1982b. An exposure and risk assessment for arsenic. Final draft 

report. U.S. Environmental Protection Agency, Office of Water 

Regulations and Standards. Washington, DC: 4-64. 

∗	 EPA. 1985a. U.S. Environmental Protection Agency: Part II. Federal 

Register 50:13456, 13474, 13496. 

EPA. 1985b. Drinking water criteria document for radium (draft).
 

Washington, DC: U. S. Environmental Protection Agency, Office of
 

Drinking Water (WH-550). NTIS No. PB86-241866.
 

∗	 EPA. 1986a. Gross alpha and gross beta - method 9310. In: Test 

methods for evaluating solid waste. 3rd ed. SW-846. Washington, DC: 

U. S. Environmental Protection Agency, Office of Solid Waste and
 

Emergency Response, 9310-l-9310-9.
 

∗	 EPA. 1986b. Alpha-emitting radium isotopes - method 9315. In: Test 

methods for evaluating solid waste. 3rd ed. SW-846. Washington, DC: 

U. S. Environmental Protection Agency, Office of Solid Waste and
 

Emergency Response, 9315-1-9315-6.
 

∗	 EPA. 1986c. U.S. Environmental Protection Agency: Part VI. Federal 

Register 51:34836-34862. 

∗	 EPA. 1987a. U.S. Environmental Protection Agency. Federal Register 

52:2822-2834. 

EPA. 1987b. U.S. Environmental Protection Agency. Federal Register
 

52:28140-28141.
 

EPA. 1987c. U.S. Environmental Protection Agency. Federal Register
 

52:8172-8186.
 

∗	 EPA. 1988. Limiting values of radionuclide intake and air 

concentration and dose conversion factors for inhalation, submersion, 

and ingestion. Federal Guidance Report No. 11. Washington, DC: U.S. 
74
 

8. REFERENCES
 

Environmental Protection Agency, Office of Radiation Programs.
 

EPA-520/l-88-020.
 

∗	 EPA. 1989a. Interim Methods for Development of Inhalation References 

Doses. U.S. Environmental Protection Agency, Office of Health and 

Environmental Assessment. Washington, DC. EP 600/8-88/066F. 

∗	 EPA. 1989b. U.S. Environmental Protection Agency. Federal Register 

54:9612-9667. 

∗	 EPA. 1989c. U.S. Environmental Protection Agency: Part II. Federal 

Register 54:22524-22543. 

∗	 Evans RD, Harris RS, Bunker JW. 1944. Radium metabolism in rats and 

the production of osteogenic sarcoma by experimental radium poisoning. 

Am J Roentgen01 & Radium Therapy 52:353-373. 

EXICHEM Data Base 1988. Organization for Economic Cooperation and
 

Development.
 

Finkel AJ, Miller CE, Hasterlik RJ. 1969a. Radium-induced malignant
 

tumors in man. In: Mays CW, Jee WS, Lloyd RD, et al., eds. Delayed
 

effects of bone-seeking radionuclides (Sun Valley Symposium, September
 

12-14, 1967). Salt Lake City, UT: University of Utah Press, 195-225.
 

Finkel MP, Biskis BO, Jinkins PB. 1969b. Toxicity of radium-226 in
 

mice. In: Ericson A, ed. Radiation induced cancer. Vienna, Austria:
 

International Atomic Energy Agency, 369-391.
 

∗	 FRC. 1960. Federal Radiation Council. Federal Register 60:4402-4403. 

∗	 Fremlin JH, Abu Jarad F. 1980. Alpha-emitters in the environment. I: 

Natural sources. Nuclear Instruments and Methods 173:197-200. 

Fremlin JH, Wilson CR. 1980. Alpha-emitters in the environment. II:
 

Man-made activity. Nuclear Instruments and Methods 173:201-204.
 

∗	 FSTRAC. 1988. Summary of state and federal drinking water standards 

and guidelines. Washington, DC: Federal-State Toxicology and 

Regulatory Alliance Committee, Chemical Communication Subcommittee. 

∗	 Gettler AO, Norris C. 1933. Poisoning from drinking radium water. 

JAMA 100:400-402. 

Goldman M. 1986. Experimental carcinogenesis in the skeleton. In:
 

Upton AC, Albert RE, Burns FJ, et al., eds. Radiation carcinogenesis.
 

New York, NY: Elsevier Science Publishing Co., 215-231.
 
75
 

8. REFERENCES
 

Gossner W. 1986, Pathology of radiation-induced bone tumors. Leuk Res
 

10:897-904.
 

∗	 Gustafson PF, Stehney AF. 1985. Exposure data for radium patients. 

In: Environmental research division annual report. Argonne, IL: 

Argonne National Laboratory. ANL-84-103 Part 11:98-180. 

∗	 Havlik B, Grafova J, Nycova B. 1968a. Radium-226 liberation from 

uranium ore processing mill waste solids and uranium rocks into surface 

streams - I: The effect of different pH of surface waters. Health Phys 

14:417-422. 

∗	 Havlik B, Nycova B, Grafova J. 1968b. Radium-226 liberation from 

uranium ore processing mill waste solids and uranium rocks into surface 

streams - II: The effect of different chemical composition of surface 

water. Health Phys 14:423-430. 

∗	 Hess CT, Michel J, Horton TR, et al. 1985. The occurrence of 

radioactivity in public water supplies in the United States. Health 

Phys 48:553-586. 

Hickey JL, Campbell SD. 1968. High radium-226 concentrations in public
 

water supplies. Public Health Rep 83:551-557.
 

∗	 Hoegerman SF. 1976. The cytogenetic effects of internal alpha emitters 

on human lympocytes: a review. In: The health effects of plutonium 

and radium. Jee WSS, ed. Salt Lake City, Utah, J.W. Press. pp 779-791. 

Howe GR, Nair RC, Newcombe HB, et al. 1987. Lung cancer mortality
 

(1950-80) in relation to radon daughter exposure in a cohort of workers
 

at the Eldorado Port Radium uranium mine: Possible modification of risk
 

by exposure rate. J Nat1 Cancer Inst 79:1255-1260.
 

∗	 HSDB. 1988. Hazardous Substances Data Bank. National Library of 

Medicine, National Toxicology Information Program, Bethesda, MD. 

December 1988. 

∗	 Humphreys ER, Loutit JF, Major IR, et al. 1985. The induction by 224Ra 

of myeloid leukaemia and osteosarcoma in male CBA mice. Int J Radiat 

Biol 47:239-247. 

Hunt CD. 1986. Fate and bioaccumulation of soil-associated low-level
 

naturally occurring radioactivity following disposal into a marine
 

ecosystem. Washington, DC: U.S Environmental Protection Agency, Office
 

of Radiation Programs.
 

ICRP. 1972. Alkaline earth metabolism in adult man, ICRP Publication
 

No. 20. Health Phys 24:125-221.
 
76
 

8. REFERENCES
 

∗	 ICRP. 1975. Report of the Task Group on Reference Man. ICRP 

Publication 23. International Commission on Radiological Protection. 

New York: Pergamon Press. 

∗	 ICRP. 1977. Recommendations of the International Commission on 

Radiological Protection. ICRP Publication No. 26. New York: Pergamon 

Press. 

∗	 ICRP. 1979. Limits for intakes of radionuclides by workers. ICRP 

Publication 30. International Commission on Radiological Protection. 

New York: Pergamon Press. 

∗	 IRIS. 1988. Integrated Risk Information System. U.S. Environmental 

Protection Agency, Washington, DC. December 1988. 

∗	 IRIS. 1989. Integrated Risk Information System. U.S. Environmental 

Protection Agency, Washington, DC. January 1989. 

∗	 Jaworowski Z, Bilkiewicz J, Zylicz E. 1971. 226Ra in contemporary and 

fossil snow. Health Phys 20:449-450. 

∗	 Jaworowski Z, Gryzbowska D. 1977. Natural radionuclides in industrial 

and rural soils. Sci Total Environ 7:45-52. 

Jee WS, Parks NJ, Miller SC, et al. 1985. Relationship of bone
 

composition to the location of radium-induced bone cancer.
 

Strahlentherapie [Sonderb] 80:75-78.
 

∗	 Joshi SR. 1987. Nondestructive determination of selected U- and ThSeries radionuclides in biological samples. Health Phys 53:417-420. 

∗	 Kalin M. 1988. Long-term ecological behaviour of abandoned uranium 

mill tailings. 3. Radionuclide concentrations and other characteristics of 

tailings, surface waters, and vegetation. Report to Environment Canada, 

Ottawa, Ontario, Canada, by Institute for Environmental Studies, University 

of Toronto, Ontario, Canada. Report No. EPS 3/HA/4. 

∗	 Kaufmann RF, Eadie GG, Russell CR. 1976. Effects of uranium mining and 

milling on ground water in the Grants Mineral Belt, New Mexico. Ground 

Water 14:296-308. 

Keane AT, Lucas HF, Markun F, et al. 1986. The estimation and
 

potential radiobiological significance of the intake of 228Ra by early
 

Ra dial workers in Illinois. Health Phys 51~313-327.
 
77
 

8. REFERENCES
 

∗	 Keitz EL. 1980. Atmospheric cycles of cadmium and lead: Emissions, 

transport, transformation and removal. The Mitre Corporation. 

McLean, VA: MTR-8OW343: 2-29-2-30. 

∗	 Klener V, Kofranek V, Onyskowova Z, et al. 1972. The late effects 

induced by 226Ra in mice. In: Bujdoso E, ed. Proceedings of the IRPA 

Second European Congress. Budapest, Hungary: Akademiaii Kiado, 

227-230. 

∗	 Kofranek, V, Sedlak A, Bubenikova D, et al. 1985. Late effects of 

226 224 239
 Ra , Ra and Pu in female mice of the ICR strain. Strahlentherapie
 

[Sonderb] 80:88-92.
 

∗	 Kramer GH, Beaulieu PC. 1983. The determination of radium-226 in urine 

[Abstract]. Atomic Energy Canada Ltd., (CA 99: 2380s) 

∗	 Landa ER. 1984. Geochemical and radiological characterization of soils 

from former radium processing sites. Heath Phys 46:385-394. 

∗	 Landa ER, Reid DF. 1982. Sorption of radium-226 from oil-production 

brine by sediments and soils. Environ Geol 5:1-8. 

Landa ER, Miller CL, Updegraff DM. 1986. Leaching of 226Ra from U mill
 

tailings by sulfate-reducing bacteria. Health Phys 51:509-518.
 

∗	 Langmuir D, Riese AC. 1985. The thermodynamic properties of radium. 

Geochimica et Cosmochimica Acta 49:1593-1601. 

Littman MS, Kirsh IE, Keane AT. 1978. Radium-induced malignant tumors
 

of the mastoid and paranasal sinuses. Am J Roentgen01 131:773-785.
 

∗	 Lloyd RD, Wrenn ME, Taylor GN, et al. 1986. Toxicity of 228Ra and 228Th 

relative to 226Ra for bone sarcoma induction in beagles. 

Strahlentherapie [Sonderb] 80:65-69. 

∗	 Longtin JP. 1988. Occurrence of radon, radium, and uranium in 

groundwater. J AWWA (July):84-93. 

∗	 Looney WB. 1955. Late effects (twenty-five to forty years) of the 

early medical and industrial use of radioactive material: Their 

relation to the more accurate establishment of maximum permissible 

amounts of radioactive elements in the body. Part I. J Bone Joint Surg 

[Am] 37-A:1169-1187. 
78
 

8. REFERENCES
 

Looney WB. 1956a. Late effects (twenty-five to forty years) of the
 

early medical and industrial use of radioactive material: Their
 

relation to the more accurate establishment of maximum permissible
 

amounts of radioactive elements in the body. Part II. J Bone Joint Surg
 

[Am] 38-A:175-218.
 

Looney WB. 1956b. Late effects (twenty-five to forty years) of the
 

early medical and industrial use of radioactive material: Their
 

relation to the more accurate establishment of maximum permissible
 

amounts of radioactive elements in the body. Part III. J Bone Joint
 

Surg [Am] 38-A:392-406.
 

Lucas HF Jr. 1960. Correlation of the natural radioactivity of the
 

human body to that of its environment: Uptake and retention of 226Ra
 

from food and water. In: Argonne National Laboratory Radiological
 

Physics Division semiannual report, July-December, 1960. Argonne
 

National Laboratory, Argonne, Illinois. ANL-6297.
 

∗	 Lucas HF. 1985. 226Ra and 228Ra in water supplies. J AWWA 7:57-66. 

∗	 Lucas HF. 1987. An improved method for the simultaneous determination 

of 224RA 226Ra, and 228Ra in water soils and sediments. In: Graves B,
 

ed. Radon, radium, and other radioactivity in groundwater. Chelsea,
 

MI: Lewis Publishers, 219-227.
 

∗	 Luz A, Muller WA, Gossner W, et al. 1976. Estimation of tumour risk at 

low dose from experimental results after incorporation of short-lived 

bone-seeking alpha-emitters 224Ra and 227Th in mice. In: Biological and 

environmental effects of low-level radiation. Vol. II. Vienna, 

Austria: International Atomic Energy Agency, 171-181. 

∗	 Lyman GH, Lyman CG. 1985. Leukemia and groundwater contamination 

[Letter] JAMA 256:2676-2677. 

∗	 Lyman GH, Lyman CG, Johnson W. 1985. Association of leukemia with 

radium groundwater contamination. JAMA 254:621-626. 

∗	 Lyman GH, Lyman C, Johnson W. 1986. Leukemia and radium groundwater 

contamination [Letter]. JAMA 255:902-903. 

∗	 Maletskos CJ, Keane AT, Telles NC, et al. 1966. The metabolism of 

intravenously administered radium and thorium in human beings and the 

relative absorption from the human gastrointestinal tract. In: Radium 

and mesothorium poisoning and dosimetry and instrumentation techniques 

in applied radioactivity. Cambridge, MA: Massachusetts Institute of 

Technology, Physics Department, 202-317. MIT-952-3. 
79
 

8. REFERENCES
 

∗	 Maletskos CJ, Keane AT, Telles NC, et al. 1969. Retention and 

absorption of 224Ra and 234Th and some dosimetric considerations of 224Ra

in human beings. In: Mays CW, Jee WS, Lloyd RD, eds. Delayed effects 

of bone-seeking radionuclides. Salt Lake City, UT: University of Utah
 

Press, 29-49.
 

∗	 Marinelli LD, Norris WP, Gustafson PF, et al. 1953. Transport of 

radium sulfate from the lung and its elimination from the human body 

following single accidental exposures. Radiology 61:903-914. 

∗	 Markose PM, Eappen KP, Raghavayya M, et al. 1982. Bioaccumulation of 

radium in a fresh water ecosystem. In: Vohra KG, ed. Natural 

radiation environment: Proceedings of the 2nd special symposium on 

natural radiation environment, held at the Bhaba Atomic Research Centre, 

Bombay, India, during January 19-23. New Delhi, India: Wiley Eastern 

Ltd., 234-238. 

∗	 Martland H. 1931. The occurrence of malignancy in radioactive persons: 

A general review of data gathered in the study of the radium dial 

painters, with special reference to the occurrence of osteogenic sarcoma 

and the inter-relationship of certain blood diseases. Am J Cancer 

15:2435-2515. 

Martland HS, Conlon P, Knef JP. 1925. Some unrecognized dangers in the
 

use and handling of radioactive substances with especial reference to
 

the storage of insoluble products of radium and mesothorium in the
 

reticula-endothelial system. JAMA 85:1769-1775.
 

Mays CW. 1988. Alpha-particle-induced cancer in humans. Health Phys
 

55:637-652.
 

∗	 Mays CW, Speiss H. 1984. Bone sarcomas in patients given radium-224. 

In: Boice JD, Fraumeni JF, eds. Radiation carcinogenesis; epidemiology 

and biological significance. N.Y. Raven Press. pp 24-1252. 

∗	 Mays CW, Cochran TH, Jee WS. 1963. Radium and radon retention in mice. 

Health Phys 9:615-619. 

∗	 Mays CW, Lloyd RD, Van Dilla MA. 1975. Fractional radon retention in 

bone. Health Phys 29:761-765. 

∗	 Mays CW, Spiess H, Chmelevsky D, et al. 1985a. Bone sarcoma cumulative 

tumor rates in patients injected with 224Ra. Strahlentherapie [Sonderb]
 

80127-31.
 

∗	 Mays CW, Rowland RE, Stehney AF. 1985b. Cancer risk from the lifetime 

intake of Ra and U isotopes. Health Phys 48:635-647. 
80
 

8. REFERENCES
 

∗	 Mays CW, Lloyd RD, Taylor GN, et al. 1987. Cancer incidence and 

lifespan vs. alpha-particle dose in beagles. Health Phys 52:617-624. 

∗	 Michel J. 1987. Sources. In: Cothern C, Smith J, eds. Environmental 

radon. New York, NY: Plenum Press, 81-130. 

∗	 Michel J, Cothern CR. 1986. Predicting the occurrence of 228Ra in 

groundwater. Health Phys 51:715-721. 

Milgram JW, Jasty M. 1986. Case report 361. Skeletal Radio1
 

15:258-267.
 

Miller CE, Finkel AJ. 1968. Radium retention in man after multiple
 

injections: The power function re-evaluated. Am J Roentgenol Radium
 

Ther Nucl Med 103:871-80.
 

Mole RH. 1985. Leukaemia induction in man by radionuclides and some
 

relevant experimental and human observations. Strahlentherapie
 

[Sonderb] 80:1-13.
 

226 214
 ∗	 Morris JS, Bobrowski G. 1979. The determination of Ra, Pb, and 

214Bi in fly ash samples from eighteen (18) coal fired power plants in 

the Untied States. In: Spencer JD, Whieldon CE Jr, eds. Proceedings 

of the Fifth International Ash Utilization Symposium, Atlanta, GA, 

February 25-27. Morgantown, WV: U.S. Department of Energy, Morgantown
 

Energy Technology Center. METC/SP-79/10 (Pt.1).
 

Muth H, Rajewsky B, Hantke H-J, et al. 1960. The normal radium content 

and the Ra226/Ca ratio of various foods, drinking water and different 

organs and tissues of the human body. Health Phys 2:239-245. 

∗	 Myrick TE, Berven BA, Haywood FF. 1981. State background radiation 

levels: Results of measurements taken during 1975-1979. Report to the 

U.S. Department of Energy by Oak Ridge National Library, Oak Ridge, TN.
 

ORNL/TM-7343.
 

NAS. 1977. Radioactivity in drinking water. In: Drinking water and
 

health. Washington, DC: National Academy of Sciences, 857-903.
 

∗	 NAS/NRC. 1989. Biologic markers in reproductive toxicology. 

Washington, DC: National Academy of Sciences/National Research Council, 

National Academy Press, 15-35. 

226 222
 Nason R, Cohen BL. 1987. Correlation between Ra in soil, Rn in
 

soil gas, and 222Ra inside adjacent houses. Health Phys 52:73-77.
 
81
 

8. REFERENCES
 

∗	 NCRP. 1987. Exposure of the population in the United States and Canada 

from natural background radiation. Bethesda MD: National Council on 

Radiation Protection and Measurement, 119-120. NCRP Report No. 94. 

∗	 Nielson KK, Rogers VC. 1981. Health effect coefficients for radium and 

radon released in the mining and milling of uranium. In: Gomez M, ed. 

Radiation Hazards in Mining, 760-763. 

∗	 NLM. 1988. Chemline. National Library of Medicine, Bethesda, MD. 

December 1988. 

∗	 Norris WP, Speckman TW. Gustafson PF. 1955. Studies of the metabolism 

of radium in man. Am J Roentg Rad Therapy Nuclear Med 73:785-802. 

∗	 NRC. 1988. Nuclear Regulatory Commission. Maximum permissble 

concentrations for uranium and thorium. 10 CFR 20. 

Parkin DM, Wahrendorf J, Demaret E, et al. 1987. Directory of on-going
 

research in cancer epidemiology. Lyon, France: International Agency
 

for Research on Cancer, 114, 327-328, 612.
 

Penna-Franca E, Fiszman M, Lobao N, et al. 1970. Radioactivity in the
 

diet in high background areas of Brazil. Health Phys 19:657-662.
 

∗	 Peterson NJ, Samuels LD, Lucas HF, et al. 1966. An epidemiologic 

approach to low-level radium 226 exposure. Public Health Rep 

81:805-814. 

Pinder JE III, McLeod KW, Alberts JJ, et al. 1984. Uptake of 244

Cm,
 238Pu and other radionuclides by trees inhabiting a contaminated flood
 

plain. Health Phys 47:375-384.
 

∗	 Pohl-Ruling J, Fischer P, Pohl E. 1976. Chromosome aberrations in 

peripheral blood lymphocytes dependent on various dose levels of natural 

radioactivity. In: Biological and environmental effects of low-level 

radation. Proceedings of the Symposium on Biological Effects of LowLevel Radiation, International Atomic Energy Agency and World Health 

Organization, Chicago, 11/3-7/75. Vol. II. Vienna, Austria: 

International Atomic Energy Agency, 317-324. 

Polednak AP. 1986. Leukemia and radium groundwater contamination
 

[Letter]. JAMA 255:903-904.
 

Polednak AP, Stehney AF, Rowland RE. 1978. Mortality among women first
 

employed before 1930 in the U.S. radium dial-painting industry: A group
 

ascertained from employment lists. Am J Epidemiol 107:179-195.
 
82
 

8. REFERENCES
 

∗	 Proescher F. 1914. The intravenous injection of soluble radium salts. 

Radium 2:45-53. 

∗	 Proescher F, Almquest BR. 1914. Contribution on the biological and 

pathological action of soluble radium salts II: Resume of the effect of 

soluble radium salts on the circulating blood cells of white mice and 

white rats. Radium 3:85-95. 

∗	 Quinby-Hunt MS, McLaughlin RD, Quintaniha A. 1986. Radiation 

monitoring: In: Greenberg AE, Morton GA, eds. Instrumentation for 

environmental monitoring. Vol. 2: Water. 2nd ed. New York, NY: 

John Wiley and Sons, 696-742. 

Raabe OG. 1984. Comparison of the carcinogenicity of radium and boneseeking
 

actinides. Health Phys 46:1241-1258.
 

∗	 Raabe OG, Book SA, Parks NJ, et al. 1981a. Lifetime studies of 226Ra 

and 90Sr toxicity in beagles - a status report. Radiat Res 86:515-528. 

Raabe OG, Parks NJ, Book SA. 1981b. Dose-response relationships for
 

bone tumors in beagles exposed to 226Ra and 90Sr. Health Phys
 

40:863-880.
 

∗	 Raabe OG, Book SA, Parks NJ. 1983. Lifetime bone cancer dose-response 

relationships in beagles and people from skeletal burdens of 226Ra and

90Sr. Health Physics 44(Suppl. 1):33-48. 

∗	 Rayno DR. 1983. Estimated dose to man from uranium milling via the 

beef/milk food-chain pathway. Sci Total Environ 31:219-241. 

∗	 Reitter GS, Martland HS. 1926. Leucopenic anemia of the regenerative 

type due to exposure to radium and mesothorium: Report of a case. Am J 

Roentgen01 16:161-166. 

Rowland RE. 1966. Exchangeable bone calcium. Clinical Orthopaedics
 

49:233-248.
 

∗	 Rowland RE, Stehney AF, Lucas HF. 1978. Dose-response relationships 

for female radium dial workers. Radiat Res 76:368-383. 

∗	 Rowland RE, Lucas HF, Schlenker RA. 1989. External radiation doses 

received by radium dial painters. Br J Radio1 21:67-71. 

∗	 Roy WR, Thiery RG, Schuller RM, et al. 1981. Coal fly ash: A review 

of the literature and proposed classification system with emphasis on 

environmental impacts. Champaign, IL: Illinois State Geological 

Survey, l-69. 
83
 

8. REFERENCES
 

∗	 Rundo J, Keane AT, Lucas HF, et al. 1986. Current (1984) status of the 

study of 226Ra and 228Ra in humans at the center for Human Radiobiology. 

Strahlentherapie [Sonderb] 80:14-21. 

∗	 Ruttenber AJ Jr, Kreiss K, Douglas RL, et al. 1984. The assessment of 

human exposure to radionuclides from a uranium tailings release and mine 

dewatering effluent. Health Phys 47:21-35. 

∗	 Sax NI, Lewis RJ Sr, eds. 1987. Hawley's condensed chemical 

dictionary. 11th ed. New York, NY: Van Nostrand Reinhold Company, 

993-995. 

Schlenker RA. 1986. Comparison of intake and committed dose equivalent
 

permitted by radiation protection systems based on annual dose
 

equivalent and committed dose equivalent for a nuclide of intermediate
 

effective half-life. Health Phys 51:207-213.
 

Schlenker RA. 1988. Skeletal 212Pb retention following 224Ra injection: 

Extrapolation of animal data to adult humans. Health Phys 54:383-396. 

Schlenker RA, Keane AT, Unni KK. 1989. Comparison of radium-induced
 

and natural bone sarcomas by histologic type, subject age and site of
 

occurrence. Br J Radio1 21:55-62.
 

∗	 Schlundt H, Nerancy JT, Morris JP. 1933. The detection and estimation 

of radium in living persons: IV. The retention of soluble radium salts 

administered intravenously. Am J Roentg Rad Therapy 30:515-522. 

∗	 Schoeters GE, Vanderborght OL. 1981. Temporal and spatial response of 

marrow colony-forming cells (CFU-S and CFU-c) after 226Ra incorporation 

in BALB/c mice. Radiat Res 88:251-265. 

Schoeters GE, Vanderborght OL. 1983. Relative effectiveness of 241Am

226Ra approached by haemopoietic stem cell studies in various bone 

marrow sites of contaminated mice. Health Phys 44:555-570. 

∗	 Schoeters GE, Luz A, Vanderborght OL. 1983. 226Ra induced bonecancers: The effects of a delayed Na-alginate treatment. Int J Radiat 

Biol 43:231-247. 

∗	 Sebesta F, Benes P, Sedlacek J, et al. 1981. Behavior of radium and 

barium in a system including uranium mine waste waters and adjacent 

surface waters. Environ Sci Technol 15:71-75. 

∗	 Seil HA, Viol CH, Gordon MA. 1915. The elimination of soluble radium 

salts taken intravenously and per OS. NY Med J 101:896-898. 
84
 

8. REFERENCES
 

∗	 Sharpe WD. 1974. Chronic radium intoxication: clinical and autopsy 

findings in long-term New Jersey survivors. Environ. Res. 8:243-383. 

Simon SL, Deming EJ. 1986. Time-dependent leaching of radium from
 

leaves and soil. J Environ Qua1 15:305-308.
 

∗	 Sonnabend E, Spiess H, Mays CW. 1986. Tooth breakage in patients 

injected with 224Ra. Strahlentherapie [Sonderb] 80:60-64. 

Sorahan T. 1985. Radium luminizers - selection effects [Letter]. J
 

Occup Med 27:7.
 

Sorahan T. 1986. Radium luminizers [Letter]. J Occup Med 28:1202.
 

∗	 Spencer H, Kramer L, Samachson J, et al. 1973. Intake and excretion 

patterns of naturally occurring radium-226 in humans. Radiat Res 

56:354-369. 

Spiers FW. 1988. Particle dosimetry in bone and the toxicity of boneseeking
 

radionuclides. Phys Med Biol 33:395-411.
 

∗	 Spiers FW, Lucas HF, Rundo J, et al. 1983. Leukaemia incidence in the 

U.S. dial workers. Health Phys 44 (Suppl 1):65-72.
 

∗	 Spiess H, Mays CW. 1979. Liver diseases in patients injected with

224Ra. Environ Res 18:55-60. 

∗	 Spiess H, Gerspach A, Mays CW. 1978. Soft-tissue effects following

224Ra injections into humans. Health Phys 35:61-81. 

∗	 Spiess H, Mays CW, Spiess-Paulus E. 1985. Growth retardation in 

children injected with 224Ra. Strahlentherapie [Sonderb] 80:45-50. 

∗	 Spiess H, Mays CW, Chmelevsky D. 1989. Malignancies in patients 

injected with 224Ra. Br J Radio1 21:7-11. 

∗	 SRC (Syracuse Research Corporation). 1989. Toxicological profile for 

thorium. Report to Agency for Toxic Substances and Disease Registry, 

U.S. Public Health Service, Atlanta GA, by Syracuse Research
 

Corporation, Syracuse, NY.
 

∗	 Stebbings JH, Semkiw W. 1989. Central nervous system tumors and 

related intracranial pathologies in radium dial workers. Br J Radio1 

21:63-66. 

∗	 Stebbings JH, Lucas HF, Stehney AF. 1984. Mortality from cancers of 

major sites in female radium dial workers. Am J Ind Med 5:435-459. 
85
 

8. REFERENCES
 

Stebbings JH, Lucas HF, Toohey RE. 1986. Leukemia and radium
 

groundwater contamination [Letter]. JAMA 255:902.
 

∗	 Stefani FH, Spiess H, Mays CW. 1985. Cataracts in patients injected 

with 224Ra. Strahlentherapie [Sonderb] 80:51-59. 

Stehney AF. 1954. Radium and thorium X in some potable waters. Acta
 

Radiologica 43:43-51.
 

∗	 Stehney AF, Lucas HF. 1955. Studies on the radium content of humans 

arising from the natural radium of their environment. In: Proceedings 

of the international conference on peaceful uses of atomic energy. New 

York, NY: United Nations, l-13. 

∗	 Stehney AF, Norris WP, Lucas HF, et al. 1955. A method for measuring 

the rate of elimination of radon in breath. Am J Roentgenol, Rad 

Therapy and Nuclear Med 73:774-784. 

∗	 Stehney AF, Lucas HF, Rowland RE. 1978. Survival times of women radium 

dial workers first exposed before 1930. In: Late biological effects of 

ionizing radiation. Vol. I. Vienna, Austria: International Atomic 

Energy Agency, 333-351. 

Sunshine I. 1983. Dr. Alexander 0. Gettler's documentation of a
 

radiation hazard. Am J Forensic Med Path01 4:307-309.
 

∗	 Swanson SM. 1983. Levels of 226RA 210Pb ToTALU in fish near a 

Saskatchewan uranium mine and mill: Health Phys 45:67-80. 

∗	 Swanson SM. 1985. Food chain transfer of U-series radionuclides in a 

northern Saskatchewan aquatic system. Health Phys 49:747-770. 

∗	 Taylor GN, Dougherty TF, Mays CW, et al. 1972. Radium-induced eye 

melanomas in dogs. Radiat Res 51:361-373. 

∗	 Taylor GN, Mays CW, Lloyd RD, et al. 1983. Comparative toxicity of

226Ra, 239Pu, 241AM, 249Cf, and 252Cf in C57BL/Do black and albino mice. 

Radiat Res'95:584-601. 

∗	 Teixeira, VS, Franc0 EP. 1986. Root uptake of exogenous radium-226 by 

three edible vegetables grown in farm soils from the vicinity of the 

first Brazilian uranium mine and mill [Abstract]. Chem Environ Proc Int 

Conf: 837-842. (CA 110: 7068b) 

Tempel V, Mehler E, Berndt G. 1970. Multiple Plattenepithelkarzinome
 

nach unkontrolliertem Gebrauch einer Radiumkompresse. Dermatol
 

Monatsschr 156:115-119. (German)
 
86
 

8. REFERENCES
 

∗	 Toohey RE, Keane AT, Rundo J. 1983. Measurement techniques for radium 

and the actinides in man at the center for human radiobiology 

[Abstract]. Health Phy 44:323-341. (CA 99: 60681b) 

Tracy BL, Letourneau EG. 1986. Leukemia and radium groundwater
 

contamination [Letter]. JAMA 255:3365.
 

∗	 Tracy BL, Prantl FA, Quinn JM. 1983. Transfer of 226Ra, 210Pb, and 

uranium from soil to garden produce: Assessment of risk. Health Phys 

44:469-477. 

United Nations. 1971. Ionizing radiation: Levels and effects.
 

New York, NY: United Nations.
 

United Nations. 1972. Ionizing radiation: Levels and effects. Vol 1:
 

Levels. New York, NY: United Nations.
 

∗	 Valentine RL, Mulholland TS, Splinter RC. 1987. Radium removal using 

sorption to filter sand. J AWWA (April):170-176. 

Vaughan J. 1986. Carcinogenic effects of radiation on the human
 

skeleton and supporting tissues. In: Upton AC, Albert RE, Burns FJ,
 

et al., eds. Radiation carcinogenesis. New York, NY: Elsevier Science
 

Publishing Co., 311-334.
 

VIEW Database. 1989. Agency for Toxic Substances and Disease Registry
 

(ATSDR), Office of External Affairs, Exposure and Disease Registry
 

Branch, Atlanta, GA. June 20, 1989. (Map based on VIEW Database,
 

June 12, 1989)
 

∗	 Walton A, Kologrivov, Kulp JL. 1959. The concentration and 

distribution of radium in the normal human skeleton. Health Phys 

1:409-416. 

∗	 Watson AP, Etnier EL, McDowell-Boyer LM. 1984. Radium-226 in drinking 

water and terrestrial food chains: Transfer parameters and normal 

exposure and dose. Nuclear Safety 25:815-829. 

Weant GE, McCormick GS. 1984. Nonindustrial sources of potentially
 

toxic substances and their applicability to source apportionment
 

methods. Research Triangle Park, NC: U. S. Environmental Protection
 

Agency (MD 14). EPA-450/4-84-003. NTIS No. PB84-231232.
 

∗	 Weast RC, ed. 1985. CRC handbook of chemistry and physics: A readyreference book of chemical and physical data. 66th ed. Boca Raton, FL: 

CRC Press, Inc., B-133. 
87
 

8. REFERENCES
 

Whittaker EL. 1986. Test procedure for gross alpha particle activity
 

in drinking water: Interlaboratory collarobrative study. Las Vegas,
 

NV: U.S. Environmental Protection Agency, Environmental Systems
 

Laboratory, EPA/600/S4-86/027.
 

∗	 WHO. 1984. Radioactive materials in drinking water. In: Guidelines 

for drinking-water quality. Vol. I: Recommendations. Geneva, 

Switzerland: World Health Organization, 103-108. 

∗	 Wick RR, Gossner W. 1983. Follow-up study of late effects in 224Ra 

treated ankylosing spondylitis patients. Health Phys 44:187-195. 

∗	 Wick RR, Gossner W. 1989. Recent results of the follow-up of radium224 treated ankylosing spondylitis patients. Br J Radio1 21:25-28. 

∗	 Wick RR, Chmelevsky D, Gossner W. 1986. 224Ra: Risk to bone and 

haematopietic tissue in ankylosing spondylitis patients. 

Strahlentherapie [Sonderb] 80:38-44. 

∗	 Windholz M, ed. 1983. The Merck index: An encyclopedia of chemicals, 

drugs, and biologicals. 10th ed. Rahway, NJ: Merck and Company, Inc., 

1170-1171. 

Wishart DL. 1986. Leukemia and radium groundwater contamination
 

[Letter]. JAMA 255:901-902.
 

∗	 Wrenn ME, Taylor GN, Stevens W, et al. 1986. Summary of dosimetry, 

pathology, and dose response for bone sarcomas in beagles injected with 

radium-226. In: Thompson RC, Mahaffey JA, eds. Life span radiation 

effects studies in animals: What can they tell us? Washington, DC: 

U.S. Department of Energy, Office of Scientific and Technical
 

Information. CONF-830951.
 

∗	 Wrenn ME, Durbin PW, Willis DL, et al. 1987. The potential toxicity of 

uranium in water. J AWWA (April):177-181. 

89
 

9. GLOSSARY
 

Absorbed Dose -- The mean energy imparted to the irradiated medium, per
 

unit mass, by ionizing radiation. Units: gray (GY), rad.
 

Absorbed Fraction -- A term used in internal dosimetry. It is that
 

fraction of the photon energy (emitted within a specified volume of
 

material) which is absorbed by the volume. The absorbed fraction
 

depends on the source distribution, the photon energy, and the size,
 

shape and composition of the volume.
 

Absorption -- The process by which radiation imparts some or all of its
 

energy to any material through which it passes.
 

Self-Absorption -- Absorption of radiation (emitted by radioactive
 

atoms) by the material in which the atoms are located; in
 

particular, the absorption of radiation within a sample being
 

assayed.
 

Absorption Coefficient -- Fractional decrease in the intensity of an
 

unscattered beam of x or gamma radiation per unit thickness (linear
 

absorption coefficient), per unit mass (mass absorption coefficient), or
 

per atom (atomic absorption coefficient) of absorber, due to deposition
 

of energy in the absorber. The total absorption coefficient is the sum
 

of individual energy absorption processes. (See Compton Effect,
 

Photoelectric Effect, and Pair Production.)
 

Linear Absorption Coefficient -- A factor expressing the fraction 

of a beam of x or gamma radiation absorbed in a unit thickness of 

material. In the expression I=Ioe

-μx , Io is the initial intensity, 

I the intensity of the beam after passage through a thickness of 

the material x, and μ is the linear absorption coefficient. 

Mass Absorption Coefficient -- The linear absorption coefficient
 

per cm divided by the density of the absorber in grams per cubic
 

centimeter. It is frequently expressed as μ/•, where μ is the
 

linear absorption coefficient and p the absorber density.
 

Absorption Ratio, Differential -- Ratio of concentration of a nuclide in
 

a given organ or tissue to the concentration that would be obtained if
 

the same administered quantity of this nuclide were uniformly
 

distributed throughout the body.
 

Activation -- The process of inducing radioactivity by irradiation.
 

Activity -- The number of nuclear transformations occurring in a given
 

quantity of material per unit time. (See Curie.)
 
90
 

9. GLOSSARY
 

Activity Median Aerodynamic Diameter (AMAD) -- The diameter of a unit-


density sphere with the same terminal settling velocity in air as that
 

of the aerosol particulate whose activity is the median for the entire
 

aerosol.
 

Acute Exposure -- Exposure to a chemical for a duration of 14 days or
 

less, as specified in the toxicological profiles.
 

Acute Radiation Syndrome -- The symptoms which taken together
 

characterize a person suffering from the effects of intense radiation.
 

The effects occur within hours or weeks.
 

Adsorption Coefficient (Koc) -- The ratio of the amount of a chemical
 

adsorbed per unit weight of organic carbon in the soil or sediment to
 

the concentration of the chemical in solution at equilibrium.
 

Adsorption Ratio (Kd) -- The amount of a chemical adsorbed by a sediment
 

or soil (i.e., the solid phase) divided by the amount of chemical in the
 

solution phase, which is in equilibrium with the solid phase, at a fixed
 

solid/solution ratio. It is generally expressed in micrograms of
 

chemical sorbed per gram of soil or sediment.
 

Alpha Particle -- A charged particle emitted from the nucleus of an
 

atom. An alpha particle has a mass charge equal in magnitude to that of
 

a helium nucleus; i.e., two protons and two neutrons and has a charge of
 

+2.
 

Annihilation (Electron) -- An interaction between a positive and a
 

negative electron in which they both disappear; their energy, including
 

rest energy, being converted into electromagnetic radiation (called
 

annihilation radiation) with two 0.51 Mev gamma photons emitted at an
 

angle of 180° to each other.
 

Atomic Mass -- The mass of a neutral atom of a nuclide, usually 

expressed in terms of "atomic mass units." The "atomic mass unit is 

one-twelfth the mass of one neutral atom of carbon-12; equivalent to 

1.6604x10-24 gm. (Symbol: u) 

Atomic Number -- The number of protons in the nucleus of a neutral atom
 

of a nuclide. The "effective atomic number" is calculated from the
 

composition and atomic numbers of a compound or mixture. An element of
 

this atomic number would interact with photons in the same way as the
 

compound or mixture. (Symbol: Z)
 

Atomic Weight -- The weighted mean of the masses of the neutral atoms of
 

an element expressed in atomic mass units.
 
91
 

9. GLOSSARY
 

Auger Effect -- The emission of an electron from the extranuclear
 

portion of an excited atom when the atom undergoes a transition to a
 

less excited state.
 

Background Radiation -- Radiation arising from radioactive material
 

other than that under consideration. Background radiation due to cosmic
 

rays and natural radioactivity is always present. There may also be
 

background radiation due to the presence of radioactive substances in
 

building materials.
 

Becquerel (Bq) -- International System of Units unit of activity and
 

equals one transformation (disintegration) per second. (See Units.)
 

Beta Particle -- Charged particle emitted from the nucleus of an atom.
 

A beta particle has a mass and charge equal in magnitude to that of the
 

electron. The charge may be either +l or -1.
 

Biologic Effectiveness of Radiation -- (See Relative Biological
 

Effectiveness)
 

Bone Seeker -- Any compound or ion which migrates in the body
 

preferentially into bone.
 

Branching -- The occurrence of two or more modes by which a radionuclide 

can undergo radioactive decay. For example, radium C can undergo • or 

ß- decay, 64Cu can undergo ß-

, ß+, or electron capture decay. An 

individual atom of a nuclide exhibiting branching disintegrates by one 

mode only. The fraction disintegrating by a particular mode is the 

"branching fraction" for that mode. The "branching ratio" is the ratio 

of two specified branching fractions (also called multiple 

disintegration). 

Bremsstrahlung -- The production of electromagnetic radiation (photons)
 

by the negative acceleration that a fast, charged particle (usually an
 

electron) undergoes from the effect of an electric or magnetic field,
 

for instance, from the field of another charged particle (usually a
 

nucleus).
 

Cancer Effect Level (CEL) -- The lowest dose of chemical in a study, or
 

group of studies, that produces significant increases in the incidence
 

of cancer (or tumors) between the exposed population and its appropriate
 

control.
 

Capture, Electron -- A mode of radioactive decay involving the capture
 

of an orbital electron by its nucleus. Capture from a particular
 

electron shell is designated as "K-electron capture," "L-electron
 

capture,II etc.
 
92
 

9. GLOSSARY
 

Capture, K-Electron -- Electron capture from the K shell by the nucleus
 

of the atom. Also loosely used to designate any orbital electron
 

capture process.
 

Carcinogen -- A chemical capable of inducing cancer.
 

Carcinoma -- Malignant neoplasm composed of epithelial cells, regardless
 

of their derivation.
 

Cataract -- A clouding of the crystalline lens of the eye which
 

obstructs the passage of light.
 

Ceiling Value (DL) -- A concentration of a substance that should not be
 

exceeded, even instantaneously.
 

Chronic Exposure -- Exposure to a chemical for 365 days or more, as
 

specified in the Toxicological Profiles.
 

Compton Effect -- An attenuation process observed for x or gamma
 

radiation in which an incident photon interacts with an orbital electron
 

of an atom to produce a recoil electron and a scattered photon of energy
 

less than the incident photon.
 

Containment -- The confinement of radioactive material in such a way
 

that it is prevented from being dispersed into the environment or is
 

released only at a specified rate.
 

Contamination, Radioactive -- Deposition of radioactive material in any
 

place where it is not desired, particularly where its presence may be
 

harmful.
 

Cosmic Rays -- High-energy particulate and electromagnetic radiations
 

which originate outside the earth's atmosphere.
 

Count (Radiation Measurements) -- The external indication of a
 

radiation-measuring device designed to enumerate ionizing events. It
 

may refer to a single detected event to the total number registered in a
 

given period of time. The term often is erroneously used to designate a
 

disintegration, ionizing event, or voltage pulse.
 

Counter, Geiger-Mueller -- Highly sensitive, gas-filled
 

radiation-measuring device. It operates at voltages sufficiently
 

high to produce avalanche ionization.
 

Counter, Scintillation -- The combination of phosphor,
 

photmultiplier tube, and associated circuits for counting light
 

emissions produced in the phosphors by ionizing radiation.
 
93
 

9. GLOSSARY
 

Curie – A unit of activity. One curie equals 3.7x1010 nuclear 

transformations per second. (Abbreviated Ci.) Several fractions of the 

curie are in common usage. 

Megacurie -- One million curies. Abbreviated MCi.
 

Microcurie -- One-millionth of a curie (3.7x104 disintegrations 

per sec). Abbreviated μCi.
 

Millicurie -- One-thousandth of a curie (3.7x107 disintegrations 

per set). Abbreviated mCi.
 

Nanocurie -- One-billionth of a curie. Abbreviated nCi.
 

Picocurie -- One-millionth of a microcurie (3.7x10-2 

disintegrations per second or 2.22 disintegrations per minute).
 

Abbreviated pCi; replaces the term μμc.
 

Decay, Radioactive -- Transformation of the nucleus of an unstable
 

nuclide by spontaneous emission of charged particles and/or photons.
 

Decay Chain or Decay Series -- A sequence of radioactive decays
 

(transformations) beginning with one nucleus. The initial nucleus, the
 

parent, decays into a daughter nucleus that differs from the first by
 

whatever particles were emitted during the decay. If further decays
 

take place, the subsequent nuclei are also usually called daughters.
 

Sometimes, to distinguish the sequence, the daughter of the first
 

daughter is called the granddaughter, etc.
 

Decay Constant -- The fraction of the number of atoms of a radioactive
 

nuclide which decay in unit time. (Symbol •). (See Disintegration
 

Constant).
 

Decay Product, Daughter Product -- A new isotope formed as a result of
 

radioactive decay. A nuclide resulting from the radioactive
 

transformation of a radionuclide, formed either directly or as the
 

result of successive transformations in a radioactive series. A decay
 

product (daughter product) may be either radioactive or stable.
 

Delta Ray -- Energetic or swiftly moving electrons ejected from an atom
 

during the process of ionization. Delta rays cause a track of secondary
 

ionizations along their path.
 

Developmental Toxicity -- The occurrence of adverse effects on the
 

developing organism that may result from exposure to a chemical prior to
 

conception (either parent), during prenatal development, or postnatally
 

to the time of sexual maturation. Adverse developmental effects may be
 

detected at any point in the lifespan of the organism.
 
94
 

9. GLOSSARY
 

Disintegration Constant -- The fraction of the number of atoms of a 

radioactive nuclide which decay in unit time; 3, is the symbol for the 

decay constant in the equation N=Noe

-λt

 where No is the initial number 

of atoms present, and N is the number of atoms present after some time, 

t. (See Decay Constant.)
 

Disintegration, Nuclear -- A spontaneous nuclear transformation
 

(radioactivity) characterized by the emission of energy and/or mass from
 

the nucleus. When large numbers of nuclei are involved, the process is
 

characterized by a definite half-life. (See Transformation, Nuclear.)
 

Dose -- A general term denoting the quantity of radiation or energy
 

absorbed. For special purposes it must be appropriately qualified. If
 

unqualified, it refers to absorbed dose.
 

Absorbed Dose -- The energy imparted to matter by ionizing
 

radiation per unit mass of irradiated material at the place of
 

interest. The unit of absorbed dose is the rad. One rad equals
 

100 ergs per gram. In SI units, the absorbed dose is the gray
 

which is 1 J/kg. (See Rad.)
 

Cumulative Dose (Radiation) -- The total dose resulting from
 

repeated or continuous exposures to radiation.
 

Dose Assessment -- An estimate of the radiation dose to an
 

individual or a population group usually by means of predictive
 

modeling techniques, sometimes supplemented by the results of
 

measurement.
 

Dose Equivalent (DE) -- A quantity used in radiation protection.
 

It expresses all radiations on a common scale for calculating the
 

effective absorbed dose. It is defined as the product of the
 

absorbed dose in rad and certain modifying factors. (The unit of
 

dose equivalent is the rem. In SI units, the dose equivalent is
 

the sievert, which equals 100 rem.)
 

Dose, Radiation -- The amount of energy imparted to matter by
 

ionizing radiation per unit mass of the matter, usually expressed
 

as the unit rad, or in SI units, 100 rad=l gray (Gy). (See
 

Absorbed Dose.)
 

Maximum Permissible Dose Equivalent (MPD) -- The greatest dose
 

equivalent that a person or specified part thereof shall be
 

allowed to receive in a given period of time.
 

Median Lethal Dose (MLD) -- Dose of radiation required to kill, 

within a specified period, 50 percent of the individuals in a 

large group of animals or organisms. Also called the LD50. 
95
 

9. GLOSSARY
 

Threshold Dose -- The minimum absorbed dose that will produce a
 

detectable degree of any given effect.
 

Tissue Dose -- Absorbed dose received by tissue in the region of
 

interest, expressed in rad. (See Dose and Rad.)
 

Dose, Fractionation -- A method of administering radiation, in which
 

relatively small doses are given daily or at longer intervals.
 

Dose, Protraction -- A method of administering radiation by delivering
 

it continuously over a relatively long period at a low dose rate.
 

Dose-distribution Factor -- A factor which accounts for modification of
 

the dose effectiveness in cases in which the radionuclide distribution
 

is nonuniform.
 

Dose Rate -- Absorbed dose delivered per unit time.
 

Dosimetry -- Quantification of radiation doses to individuals or
 

populations resulting from specified exposures.
 

Early Effects (of radiation exposure) -- Effects which appear within 60
 

days of an acute exposure.
 

Electron -- A stable elementary particle having an electric charge equal 

to ±1.60210x10-19 C (Coulombs) and a rest mass equal to 9.1091x10-31 kg. 

A positron is a positively charged "electron." (See Positron.) 

Electron Volt -- A unit of energy equivalent to the energy gained by an 

electron in passing through a potential difference of one volt. Larger 

multiple units of the electron volt are frequently used: keV for 

thousand or kilo electron volts; MeV for million or mega electron volts. 

(Abbreviated: eV, 1 eV=1.6x10-12 erg.) 

Embryotoxicity and Fetotoxicity -- Any toxic effect on the conceptus as
 

a result of prenatal exposure to a chemical; the distinguishing feature
 

between the two terms is the stage of development during which the
 

insult occurred. The terms, as used here, include malformations and
 

variations, altered growth, and in utero death.
 

Energy -- Capacity for doing work. "Potential energy" is the energy 

inherent in a mass because of its spatial relation to other masses. 

"Kinetic energy" is the energy possessed by a mass because of its 

motion; MKSA unit: kg-m2

/sec2 or joules. 

Binding Energy -- The energy represented by the difference in mass
 

between the sum of the component parts and the actual mass of the
 

nucleus.
 
96
 

9. GLOSSARY
 

Excitation Energy -- The energy required to change a system from
 

its ground state to an exited state. Each different excited state
 

has a different excitation energy.
 

Ionizing Energy -- The average energy lost by ionizing radiation
 

in producing an ion pair in a gas. For air, it is about 33.73 eV.
 

Radiant Energy -- The energy of electromagnetic radiation, such as
 

radio waves, visible light, x and gamma rays.
 

Enriched Material -- (1) Material in which the relative amount of one or 

more isotopes of a constituent has been increased. (2) Uranium in which 

the abundance of the 235U isotope is increased above normal. 

EPA Health Advisory -- An estimate of acceptable drinking water levels
 

for a chemical substance based on health effects information. A health
 

advisory is not a legally enforceable federal standard, but serves as
 

technical guidance to assist federal, state, and local officials.
 

Equilibrium, Radioactive -- In a radioactive series, the state which
 

prevails when the ratios between the activities of two or more
 

successive members of the series remains constant.
 

Secular Equilibrium -- If a parent element has a very much longer
 

half-life than the daughters (so there is not appreciable change
 

in its amount in the time interval required for later products to
 

attain equilibrium) then, after equilibrium is reached, equal
 

numbers of atoms of all members of the series disintegrate in unit
 

time. This condition is never exactly attained, but is
 

essentially established in such a case as radium and its series to
 

Radium D. The half-life of radium is about 1,600 years; of radon,
 

approximately 3.82 days, and of each of the subsequent members, a
 

few minutes. After about a month, essentially the equilibrium
 

amount of radon is present; then (and for a long time) all members
 

of the series disintegrate the same number of atoms per unit time.
 

Transient Equilibrium -- If the half-life of the parent is short
 

enough so the quantity present decreases appreciably during the
 

period under consideration, but is still longer than that of
 

successive members of the series, a stage of equilibrium will be
 

reached after which all members of the series decrease in activity
 

exponentially with the period of the parent. An example of this
 

is radon (half-life of approximately 3.82 days) and successive
 

members of the series to Radium D. Equilibrium, Radiation -- The
 

condition in a radiation field where the energy of the radiations
 

entering a volume equals the energy of the radiations leaving that
 

volume.
 
97
 

9. GLOSSARY
 

Equilibrium Fraction (F) -- In radon-radon daughter equilibrium, the
 

parents and daughters have equal radioactivity, that is, as many decay
 

into a specific nuclide as decay out. However, if fresh radon is
 

continually entering a volume of air or if daughters are lost by
 

processes other than radioactive decay, e.g., plate out or migration out
 

of the volume, a disequilibrium develops. The equilibrium fraction is a
 

measure of the degree of equilibrium/disequilibrium. The working-level
 

definition of radon does not take into account the amount of
 

equilibrium. The equilibrium fraction is used to estimate working
 

levels based on measurement of radon only.
 

Excitation -- The addition of energy to a system, thereby transferring
 

it from its ground state to an excited state. Excitation of a nucleus,
 

an atom, or a molecule can result from absorption of photons or from
 

inelastic collisions with other particles. The excited state of an atom
 

is a metastable state and will return to ground state by radiation of
 

the excess energy.
 

Exposure -- A measure of the ionization produced in air by x or gamma
 

radiation. It is the sum of the electrical charges on all ions of one
 

sign produced in air when all electrons liberated by photons in a volume
 

element of air are completely stopped in air, divided by the mass of the
 

air in the volume element. The special unit of exposure is the
 

roentgen.
 

Fission, Nuclear -- A nuclear transformation characterized by the
 

splitting of a nucleus into at least two other nuclei and the release of
 

a relatively large amount of energy.
 

Gamma Ray -- Short wavelength electromagnetic radiation of nuclear
 

origin (range of energy from 10 keV to 9 MeV).
 

Genetic Effect of Radiation -- Inheritable change, chiefly mutations,
 

produced by the absorption of ionizing radiation by germ cells. On the
 

basis of present knowledge these effects are purely additive; there is
 

no recovery.
 

Gray (Gy) -- SI unit of absorbed dose. One gray equals 100 rad. (See
 

Units.)
 

Half-Life, Biological -- The time required for the body to eliminate
 

one-half of any absorbed substance by regular processes of elimination.
 

Approximately the same for both stable and radioactive isotopes of a
 

particular element. This is sometimes referred to as half-time.
 

Half-Life, Effective -- Time required for a radioactive element in an
 

animal body to be diminished 50% as a result of the combined action of
 

radioactive decay and biological elimination.
 
98
 

9. GLOSSARY
 

Effective half-life: = Biological half-life x Radioactive half-life


 Biological half-life + Radioactive half-life
 

Half-life, Radioactive -- Time required for a radioactive substance to
 

lose 50% of its activity by decay. Each radionuclide has a unique halflife.
 

Immediately Dangerous to Life or Health (IDLH) -- The maximum
 

environmental concentration of a contaminant from which one could escape
 

within 30 minutes without any escape-impairing symptoms or irreversible
 

health effects.
 

Immunologic Toxicity -- The occurrence of adverse effects on the immune
 

system that may result from exposure to environmental agents such as
 

chemicals.
 

In Vitro -- Isolated from the living organism and artificially
 

maintained, as in a test tube.
 

In Vivo -- Occurring within the living organism.
 

Intensity -- Amount of energy per unit time passing through a unit area
 

perpendicular to the line of propagation at the point in question.
 

Intermediate Exposure -- Exposure to a chemical for a duration of 15 to
 

364 days as specified in the Toxicological Profiles.
 

Internal Conversion -- One of the possible mechanisms of decay from the
 

metastable state (isomeric transition) in which the transition energy is
 

transferred to an orbital electron, causing its ejection from the atom.
 

The ratio of the number of internal conversion electrons to the number
 

of gamma quanta emitted in the de-excitation of the nucleus is called
 

the "conversion ratio.II
 

Ion -- Atomic particle, atom, or chemical radical bearing a net
 

electrical charge, either negative or positive.
 

Ion Pair -- Two particles of opposite charge, usually referring to the
 

electron and positive atomic or molecular residue resulting after the
 

interaction of ionizing radiation with the orbital electrons of atoms.
 

Ionization -- The process by which a neutral atom or molecule acquires a
 

positive or negative charge.
 

Primary Ionization -- (1) In collision theory: the ionization
 

produced by the primary particles as contrasted to the "total
 

ionization" which includes the "secondary ionization" produced by
 
99
 

9. GLOSSARY
 

delta rays. (2) In counter tubes: the total ionization produced
 

by incident radiation without gas amplification.
 

Specific Ionization -- Number of ion pairs per unit length of path
 

of ionizing radiation in a medium; e.g., per centimeter of air or
 

per micrometer of tissue.
 

Total Ionization -- The total electric charge of one sign on the
 

ions produced by radiation in the process of losing its kinetic
 

energy. For a given gas, the total ionization is closely
 

proportional to the initial ionization and is nearly independent
 

of the nature of the ionizing radiation. It is frequently used as
 

a measure of radiation energy.
 

Ionization Density -- Number of ion pairs per unit volume.
 

Ionization Path (Track) -- The trail of ion pairs produced by ionizing
 

radiation in its passage through matter.
 

Isobars -- Nuclides having the same mass number but different atomic
 

numbers.
 

Isomers -- Nuclides having the same number of neutrons and protons but
 

capable of existing, for a measurable time, in different quantum states
 

with different energies and radioactive properties. Commonly the isomer
 

of higher energy decays to one with lower energy by the process of
 

isomeric transition.
 

Isotones -- Nuclides having the same number of neutrons in their nuclei.
 

Isotopes -- Nuclides having the same number of protons in their nuclei,
 

and hence the same atomic number, but differing in the number of
 

neutrons, and therefore in the mass number. Almost identical chemical
 

properties exist between isotopes of a particular element. The term
 

should not be used as a synonym for nuclide.
 

Stable Isotope -- A nonradioactive isotope of an element.
 

Joule -- The unit for work and energy, equal to one newton expended
 

along a distance of one meter (lJ=lNxlm).
 

Labeled Compound -- A compound consisting, in part, of labeled
 

molecules. That is molecules including radionuclides in their
 

structure. By observations of radioactivity or isotopic composition,
 

this compound or its fragments may be followed through physical,
 

chemical, or biological processes.
 
100
 

9. GLOSSARY
 

Late Effects (of radiation exposure) -- Effects which appear 60 days or
 

more following an acute exposure.
 

Lethal Concentration (LO) (LCLO ) -- The lowest concentration of a chemical 

in air which has been reported to have caused death in humans or 

animals. 

Lethal Concentration (50) (LC50) -- The calculated concentration of a 

chemical in air to which exposure for a specific length of time is 

expected to cause death in 50% of a defined laboratory animal 

population. 

Lethal Dose (LO) (LDLO) -- The lowest dose of a chemical introduced by a 

route other than inhalation that is expected to have caused death in 

humans or animals. 

Lethal Dose (50) (LD50) -- The dose of a chemical which has been 

calculated to cause death in 50% of a defined laboratory animal 

population. 

Lethal Time (50) (LT50) -- A calculated period of time within which a 

specific concentration of a chemical is expected to cause death in 50% 

of a defined laboratory animal population. 

Linear Energy Transfer (LET) -- The average amount of energy transferred
 

locally to the medium per unit of particle track length.
 

Low-LET -- Radiation characteristic of electrons, x-rays, and
 

gamma rays.
 

High-LET -- Radiation characteristic of protons or fast neutrons.
 

Average LET -- is specified to even out the effect of a particle
 

that is slowing down near the end of its path and to allow for the
 

fact that secondary particles from photon or fast-neutron beams
 

are not all of the same energy.
 

Lowest-Observed-Adverse-Effect Level (LOAEL) -- The lowest dose of
 

chemical in a study, or group of studies, that produces statistically or
 

biologically significant increases in frequency or severity of adverse
 

effects between the exposed population and its appropriate control.
 

Linear Hypothesis -- The assumption that a dose-effect curve derived
 

from data in the high dose and high dose-rate ranges may be extrapolated
 

through the low dose and low dose range to zero, implying that,
 

theoretically, any amount of radiation will cause some damage.
 
101
 

9. GLOSSARY
 

Malformations -- Permanent structural changes in an organism that may
 

adversely affect survival, development, or function.
 

Mass Numbers -- The number of nucleons (protons and neutrons) in the
 

nucleus of an atom. (Symbol: A)
 

Minimal Risk Level -- An estimate of daily human exposure to a chemical
 

that is likely to be without an appreciable risk of deleterious effects
 

(noncancerous) over a specified duration of exposure.
 

Mutagen -- A substance that causes mutations. A mutation is a change in
 

the genetic material in a body cell. Mutation can lead to birth
 

defects, miscarriages, or cancer.
 

Neurotoxicity -- The occurrence of adverse effects on the nervous system
 

following exposure to chemical.
 

Neutrino -- A neutral particle of very small rest mass originally
 

postulated to account for the continuous distribution of energy among
 

particles in the beta-decay process.
 

No-Observed-Adverse-Effect Level (NOAEL) -- The dose of chemical at
 

which there were no statistically or biologically significant increases
 

in frequency or severity of adverse effects seen between the exposed
 

population and its appropriate control. Effects may be produced at this
 

dose, but they are not considered to be adverse.
 

Nucleon -- Common name for a constituent particle of the nucleus.
 

Applied to a proton or neutron.
 

Nuclide -- A species of atom characterized by the constitution of its
 

nucleus. The nuclear constitution is specified by the number of protons
 

(Z) number of neutrons (N), and energy content; or, alternatively, by
 

the atomic number (Z), mass number A=(N+Z), and atomic mass. To be
 

regarded as a distinct nuclide, the atom must be capable of existing for
 

a measurable time. Thus, nuclear isomers are separate nuclides, whereas
 

promptly decaying excited nuclear states and unstable intermediates in
 

nuclear reactions are not so considered.
 

Octanol-Water Partition Coefficient (Kow) -- The equilibrium ratio of
 

the concentrations of a chemical in n-octanol and water, in dilute
 

solution.
 

Pair Production -- An absorption process for x and gamma radiation in
 

which the incident photon is annihilated in the vicinity of the nucleus
 

of the absorbing atom, with subsequent production of an electron and
 

positron pair. This reaction only occurs for incident photon energies
 

exceeding 1.02 MeV.
 
102
 

9. GLOSSARY
 

Parent -- A radionuclide which, upon disintegration, yields a spec ified
 

nuclide--either directly or as a later member of a radioactive series.
 

Photon -- A quantity of electromagnetic energy (E) whose value in joules
 

is the product of its frequency (v) in hertz and Planck constant (h).
 

The equation is: E=hv.
 

Photoelectric Effect -- An attenuation process observed for x- and
 

gamma- radiation in which an incident photon interacts with an orbital
 

electron of an atom delivering all of its energy to produce a recoil
 

electron, but with no scattered photon.
 

Positron -- Particle equal in mass to the electron (9.1091x10-31 kg) and 

having an equal but positive charge (+1.60210x10-19 Coulombs). (See 

Electron). 

Potential Ionization -- The potential necessary to separate one electron
 

from an atom, resulting in the formation of an ion pair.
 

Power, Stopping -- A measure of the effect of a substance upon the
 

kinetic energy of a charged particle passing through it.
 

Progeny -- The decay products resulting after a series of radioactive
 

decays. Progeny can also be radioactive, and the chain continues until
 

a stable nuclide is formed.
 

Proton -- Elementary nuclear particle with a positive electric charge
 

equal numerically to the charge of the electron and a rest mass of
 

1.007277 mass units.
 

q1* -- The upper-bound estimate of the low-dose slope of the doseresponse 

curve as determined by the multistage procedure. The q1* can 

be used to calculate an estimate of carcinogenic potency, the 

incremental excess cancer risk per unit of exposure (usually μg/L for 

water, mg/kg/day for food, and ,μg/m3

 for air). 

Quality -- A term describing the distribution of the energy deposited by
 

a particle along its track; radiations that produce different densities
 

of ionization per unit intensity are said to have different "qualities."
 

Quality Factor (QF) -- The linear-energy-transfer-dependent factor by
 

which absorbed doses are multiplied to obtain (for radiation protection
 

purposes) a quantity that expresses - on a common scale for all ionizing
 

radiation - the effectiveness of the absorbed dose.
 

Rad -- The unit of absorbed dose equal to 0.01 J/kg in any medium. (See
 

Absorbed Dose.)
 
103
 

9. GLOSSARY
 

Radiation -- (1) The emission and propagation of energy through space or
 

through a material medium in the form of waves; for instance, the
 

emission and propagation of electromagnetic waves, or of sound and
 

elastic waves. (2) The energy propagated through space or through a
 

material medium as waves; for example, energy in the form of
 

electromagnetic waves or of elastic waves. The term radiation or
 

radiant energy, when unqualified, usually refers to electro-magnetic
 

radiation. Such radiation commonly is classified, according to
 

frequency, as Hertzian, infra-red, visible (light), ultra-violet, X-ray
 

and gamma ray. (See Photon.) (3) By extension, corpuscular emission,
 

such as alpha and beta radiation, or rays of mixed or unknown type, as
 

cosmic radiation.
 

Annihilation Radiation -- Photons produced when an electron and a
 

positron unite and cease to exist. The annihilation of a
 

positron-electron pair results in the production of two photons,
 

each of 0.51 MeV energy.
 

Background Radiation -- Radiation arising from radioactive
 

material other than the one directly under consideration.
 

Background radiation due to cosmic rays and natural radioactivity
 

is always present. There may also be background radiation due to
 

the presence of radioactive substances in other parts of the
 

building, in the building material itself, etc.
 

Characteristic (Discrete) Radiation -- Radiation originating from
 

an atom after removal of an electron of excitation of the nucleus,
 

The wavelength of the emitted radiation is specific, depending
 

only on the nuclide and particular energy levels involved.
 

External Radiation -- Radiation from a source outside the body -­

the radiation must penetrate the skin.
 

Internal Radiation -- Radiation from a source within the body (as
 

a result of deposition of radionuclides in body tissues).
 

Ionizing Radiation -- Any electromagnetic or particulate radiation
 

capable of producing ions, directly or indirectly, in its passage
 

through matter.
 

Monoenergetic Radiation -- Radiation of a given type (alpha, beta,
 

neutron, gamma, etc.) in which all particles or photons originate
 

with and have the same energy.
 

Scattered Radiation -- Radiation which during its passage through
 

a substance, has been deviated in direction. It may also have
 

been modified by a decrease in energy.
 
104
 

9. GLOSSARY
 

Secondary Radiation -- Radiation that results from absorption of
 

other radiation in matter. It may be either electromagnetic or
 

particulate.
 

Radioactivity -- The property of certain nuclides to spontaneously emit
 

particles or gamma radiation or x radiation following orbital electron
 

capture or after undergoing spontaneous fission.
 

Artificial Radioactivity -- Man-made radioactivity produced by
 

particle bombardment or electromagnetic irradiation, as opposed to
 

natural radioactivity.
 

Induced Radioactivity -- Radioactivity produced in a substance
 

after bombardment with neutrons or other particles. The resulting
 

activity is "natural radioactivity" if formed by nuclear reactions
 

occurring in nature, and "artificial radioactivity" if the
 

reactions are caused by man.
 

Natural Radioactivity -- The property of radioactivity exhibited
 

by more than 50 naturally occurring radionuclides.
 

Radioisotopes -- A radioactive atomic species of an element with the
 

same atomic number and usually identical chemical properties.
 

Radionuclide -- A radioactive species of an atom characterized by the
 

constitution of its nucleus.
 

Radiosensitivity -- Relative susceptibility of cells, tissues, organs,
 

organisms, or any living substance to the injurious action of radiation.
 

Radiosensitivity and its antonym, radioresistance, are currently used in
 

a comparative sense, rather than in an absolute one.
 

Reaction (Nuclear) -- An induced nuclear disintegration, i.e., a process
 

occurring when a nucleus comes in contact with a photon, an elementary
 

particle, or another nucleus. In many cases the reaction can be
 

represented by the symbolic equation: X+a→Y+b or, in abbreviated form, 

X(a,b) Y. X is the target nucleus, a is the incident particle or 

photon, b is an emitted particle or photon, and Y is the product 

nucleus. 

Reference Dose (RfD) -- An estimate (with uncertainty spanning perhaps
 

an order of magnitude) of the daily exposure of the human population to
 

a potential hazard that is likely to be without risk of deleterious
 

effects during a lifetime. The RfD is operationally derived from the
 

NOAEL (from animal and human studies) by a consistent application of
 

uncertainty factors that reflect various types of data used to estimate
 

RfDs and an additional modifying factor, which is based on a
 
105
 

9. GLOSSARY
 

professional judgment of the entire database on the chemical. The RfDs
 

are not applicable to nonthreshold effects such as cancer.
 

Relative Biological Effectiveness (RBE) -- The RBE is a factor used to
 

compare the biological effectiveness of absorbed radiation doses (i.e.,
 

rad) due to different types of ionizing radiation. More specifically,
 

it is the experimentally determined ratio of an absorbed dose of a
 

radiation in question to the absorbed dose of a reference radiation
 

required to produce an identical biological effect in a particular
 

experimental organism or tissue. NOTE: This term should not be used in
 

radiation protection. (See Quality Factor.)
 

Rem -- A unit of dose equivalent. The dose equivalent in rem is
 

numerically equal to the absorbed dose in rad multiplied by the quality
 

factor, the distribution factor, and any other necessary modifying
 

factors.
 

Reportable Quantity (RQ) -- The quantity of a hazardous substance that
 

is considered reportable under CERCIA. Reportable quantities are (1) 1
 

lb or greater or (2) for selected substances, an amount established by
 

regulation either under CERCLA or under Section 311 of the Clean Water
 

Act. Quantities are measured over a 24-hour period.
 

Reproductive Toxicity -- The occurrence of adverse effects on the
 

reproductive system that may result from exposure to a chemical. The
 

toxicity may be directed to the reproductive organs and/or the related
 

endocrine system. The manifestation of such toxicity may be noted as
 

alterations in sexual behavior, fertility, pregnancy outcomes, or
 

modifications in other functions that are dependent on the integrity of
 

this system.
 

Roentgen (R) -- A unit of exposure for photon radiation. One roentgen
 

equals 2.58x10-4 Coulomb per kilogram of air.
 

Short-Term Exposure Limit (STEL) -- The maximum concentration to which
 

workers can be exposed continually for up to 15 minutes. No more than
 

four excursions are allowed per day, and there must be at least 60
 

minutes between exposure periods. The daily TLV-TWA may not be
 

exceeded.
 

SI Units -- The International System of Units as defined by the General
 

Conference of Weights and Measures in 1960. These units are generally
 

based on the meter/kilogram/second units, with special quantities for
 

radiation including the becquerel, gray, and sievert.
 

Sickness, Radiation -- (Radiation Therapy): A self-limited syndrome
 

characterized by nausea, vomiting, diarrhea, and psychic depression
 

following exposure to appreciable doses of ionizing radiation,
 
106
 

9. GLOSSARY
 

particularly to the abdominal region. Its mechanism is unknown and
 

there is no satisfactory remedy. It usually appears a few hours after
 

irradiation and may subside within a day. It may be sufficiently severe
 

to necessitate interrupting the treatment series or to incapacitate the
 

patient. (General): The syndrome associated with intense acute
 

exposure to ionizing radiations. The rapidity with which symptoms
 

develop is a rough measure of the level of exposure.
 

Sievert -- The SI unit of radiation dose equivalent. It is equal to
 

dose in grays times a quality factor times other modifying factors, for
 

example, a distribution factor; 1 sievert equals 100 rem.
 

Specific Activity -- Total activity of a given nuclide per gram of an
 

element.
 

Specific Energy -- The actual energy per unit mass deposited per unit
 

volume in a given event. This is a stochastic quantity as opposed to
 

the average value over a large number of instance (i.e., the absorbed
 

dose).
 

Standard Mortality Ratio (SMR) -- Standard mortality ratio is the ratio
 

of the disease or accident mortality rate in a certain specific
 

population compared with that in a standard population. The ratio is
 

based on 200 for the standard so that an SMR of 100 means that the test
 

population has twice the mortality from that particular cause of death.
 

Stopping Power -- The average rate of energy loss of a charged particle
 

per unit thickness of a material or per unit mass of material traversed.
 

Surface-seeking Radionuclide -- A bone-seeking internal emitter that is
 

deposited and remains on the surface for a long period of time. This
 

contrasts with a volume seeker, which deposits more uniformly throughout
 

the bone volume.
 

Target Organ Toxicity -- This term covers a broad range of adverse
 

effects on target organs or physiological systems (e.g., renal,
 

cardiovascular) extending from those arising through a single limited
 

exposure to those assumed over a lifetime of exposure to a chemical.
 

Target Theory (Hit Theory) -- A theory explaining some biological
 

effects of radiation on the basis that ionization, occurring in a
 

discrete volume (the target) within the cell, directly causes a lesion
 

which subsequently results in a physiological response to the damage at
 

that location. One, two, or more "hits" (ionizing events within the
 

target) may be necessary to elicit the response.
 

Teratogen -- A chemical that causes structural defects that affect the
 

development of a fetus.
 

108
 

9. GLOSSARY
 

Working Level (WL) -- Any combination of short-lived radon daughters in 

1 liter of air that will result in the ultimate emission of 1.3x105

 MeV 

of potential alpha energy. 

Working Level Month (WLM) -- Inhalation of air with a concentration of 1
 

WL of radon daughters for 170 working hours results in an exposure of 1
 

WLM.
 

X-rays -- Penetrating electromagnetic radiations whose wave lengths are
 

shorter than those of visible light. They are usually produced by
 

bombarding a metallic target with fast electrons in a high vacuum. In
 

nuclear reaction, it is customary to refer to photons originating in the
 

extranuclear part of the atom as X-rays. These rays are sometimes
 

called roentgen rays after their discoverer, W.C. Roentgen.
 
109
 

APPENDIX A
 

PEER REVIEW
 

A peer review panel was assembled for radium. The panel consisted of
 

the following members: Dr. Carmia Borek, Professor of Pathology,
 

Columbia University; Dr. Douglas Crawford-Brown, Assistant Professor in
 

the Department of Environmental Science, University of North Carolina;
 

Dr. Haluk Ozkaynak, Lecturer, Harvard School of Public Health, Research
 

Fellow, Energy and Environmental Policy Center, Kennedy School of
 

Government, Harvard University; Dr. Ray Lloyd, Research Professor,
 

Radiobiology Division, University of Utah. These experts collectively
 

have knowledge of radium's physical and chemical properties,
 

toxicokinetics, key health end points, mechanisms of action, human and
 

animal exposure, and quantification of risk to humans. All reviewers
 

were selected in conformity with the conditions for peer review
 

specified in Section 104(i)(13) of the Comprehensive Environmental
 

Response, Compensation, and Liability Act, as amended.
 

A joint panel of scientists from ATSDR and EPA has reviewed the peer
 

reviewers' comments and determined which comments will be included in
 

the profile. A listing of the peer reviewers' comments not incorporated
 

in the profile, with a brief explanation of the rationale for their
 

exclusion, exists as part of the administrative record for this
 

compound. A list of databases reviewed and a list of unpublished
 

documents cited are also included in the administrative record.
 

The citation of the peer review panel should not be understood to
 

imply their approval of the profile's final content. The responsibility
 

for the content of this profile lies with the Agency for Toxic
 

Substances and Disease Registry.
 

111
 

APPENDIX B
 

OVERVIEW OF BASIC RADIATION PHYSICS, CHEMISTRY AND BIOLOGY
 

Understanding the basic concepts in radiation physics, chemistry,
 

and biology is important to the evaluation and interpretation of
 

radiation-induced adverse health effects and to the derivation of
 

radiation protection principles. This appendix presents a brief
 

overview of the areas of radiation physics, chemistry, and biology and
 

is based to a large extent on the reviews of Mettler and Moseley (1985),
 

Hobbs and McClellan (1986), Eichholz (1982), Hendee (1973), and Early et
 

al. (1979).
 

B.l RADIONUCLIDES AND RADIOACTIVITY
 

The substances we call elements are composed of atoms. Atoms in
 

turn are made up of neutrons, protons, and electrons; neutrons and
 

protons in the nucleus and electrons in a cloud of orbits around the
 

nucleus. Nuclide is the general term referring to any nucleus along
 

with its orbital electrons. The nuclide is characterized by the
 

composition of its nucleus and hence by the number of protons and
 

neutrons in the nucleus. All atoms of an element have the same number
 

of protons (this is given by the atomic number) but may have different
 

numbers of neutrons (this is reflected by the atomic mass or atomic
 

weight of the element). Atoms with different atomic mass but the same
 

atomic numbers are referred to as isotopes of an element.
 

The numerical combination of protons and neutrons in most nuclides
 

is such that the atom is said to be stable; however, if there are too
 

few or too many neutrons, the nucleus of the atom is unstable. Unstable
 

nuclides undergo a process referred to as radioactive transformation in
 

which energy is emitted. These unstable atoms are called radionuclides;
 

their emissions are called ionizing radiation; and the whole property is
 

called radioactivity. Transformation or decay results in the formation
 

of new nuclides some of which may themselves be radionuclides, while
 

others are stable nuclides. This series of transformations is called
 

the decay chain of the radionuclide. The first radionuclide in the
 

chain is called the parent; the subsequent products of the
 

transformation are called progeny, daughters, or decay products.
 

In general there are two classifications of radioactivity and
 

radionuclides: natural and man-made. Naturally-occurring radionuclides
 

exist in nature and no additional energy is necessary to place them in
 

an unstable state. Natural radioactivity is the property of some
 

naturally occurring, usually heavy elements, that are heavier than lead.
 

Radionuclides, such as radium and uranium, primarily emit alpha
 

particles. Some lighter elements such as carbon-14 and tritium
 

(hydrogen-3) primarily emit beta particles as they transform to a more
 

stable atom. Natural radioactive atoms heavier than lead cannot attain
 
112
 

APPENDIX B
 

a stable nucleus heavier than lead. Everyone is exposed to background
 

radiation from naturally-occurring radionuclides throughout life. This
 

background radiation is the major source of radiation exposure to man
 

and arises from several sources. The natural background exposures are
 

frequently used as a standard of comparison for exposures to various
 

man-made sources of ionizing radiation.
 

Man-made radioactive atoms are produced either as a by-product of
 

fission of uranium atoms in a nuclear reactor or by bombarding stable
 

atoms with particles, such as neutrons, directed at the stable atoms
 

with high velocity. These artificially produced radioactive elements
 

usually decay by emission of particles, such as positive or negative
 

beta particles and one or more high energy photons (gamma rays).
 

Unstable (radioactive) atoms of any element can be produced.
 

Both naturally occurring and man-made radioisotopes find
 

application in medicine, industrial products, and consumer products.
 

Some specific radioisotopes, called fall-out, are still found in the
 

environment as a result of nuclear weapons use or testing.
 

B.2 RADIOACTIVE DECAY
 

B.2.1 Principles of Radioactive Decay
 

The stability of an atom is the result of the balance of the forces
 

of the various components of the nucleus. An atom that is unstable
 

(radionuclide) will release energy (decay) in various ways and transform
 

to stable atoms or to other radioactive species called daughters, often
 

with the release of ionizing radiation. If there are either too many or
 

too few neutrons for a given number of protons, the resulting nucleus
 

may undergo transformation. For some elements, a chain of daughter
 

decay products may be produced until stable atoms are formed.
 

Radionuclides can be characterized by the type and energy of the
 

radiation emitted, the rate of decay, and the mode of decay. The mode
 

of decay indicates how a parent compound undergoes transformation.
 

Radiations considered here are primarily of nuclear origin, i.e., they
 

arise from nuclear excitation, usually caused by the capture of charged
 

or uncharged nucleons by a nucleus, or by the radioactive decay or
 

transformation of an unstable nuclide. The type of radiation may be
 

categorized as charged or uncharged particles (electrons, neutrons,
 

neutrinos, alpha particles, beta particles, protons, and fission
 

products) or electromagnetic radiation (gamma rays and X-rays). Table
 

B-l summarizes the basic characteristics of the more common types of
 

radiation encountered.
 

B.2.2 Half-Life and Activity
 

For any given radionuclide, the rate of decay is a first-order
 

process that depends on the number of radioactive atoms present and is
 

114
 

APPENDIX B
 

characteristic for each radionuclide. The process of decay is a series of
 

random events; temperature, pressure, or chemical combinations do not effect
 

the rate of decay. While it may not be possible to predict exactly which atom
 

is going to undergo transformation at any given time, it is possible to
 

predict, on the average, how many atoms will transform during any interval of
 

time.
 

The source strength is a measure of the rate of emission of radiation.
 

For these radioactive materials it is customary to describe the source
 

strength in terms of the source activity, which is defined as the number of
 

disintegrations (transformations) per unit time occurring in a given quantity
 

of this material. The unit of activity is the curie (Ci) which was originally
 

related to the activity of one gram of radium, but is now defined as:
 

1 curie (Ci) = 3.7x1010 disintegrations (transformations)/second (dps) or
 

2.22x1012 disintegrations (transformations)/minute (dpm).
 

The SI unit of activity is the becquerel (Bq); 1 Bq = 1 transformation/second.
 

Since activity is proportional to the number of atoms of the radioactive 

material, the quantity of any radioactive material is usually expressed in 

curies, regardless of its purity or concentration. The transformation of 

radioactive nuclei is a random process, and the rate of transformation is 

directly proportional to the number of radioactive atoms present. For any 

pure radioactive substance, the rate of decay is usually described by its 

radiological half-life, TR, i.e., the time it takes for a specified source 

material to decay to half its initial activity. 

The activity of a radionuclide at time t may be calculated by:
 

-0.693t/T
 A = Ao e
 rad
 

where A is the activity in dps, Ao is the activity at time zero, t is the time
 

at which measured, and Trad is the radiological half-life of the radionuclide.
 

It is apparent that activity exponentially decays with time. The time when
 

the activity of a sample of radioactivity becomes one-half its original value
 

is the radioactive half-life and is expressed in any suitable unit of time.
 

The specific activity is the radioactivity per unit weight of material.
 

This activity is usually expressed in curies per gram and may be calculated by
 

curies/gram = l.3x108

/(Trad)(atomic weight)
 

where Trad is the radiological half-life in days.
 

In the case of radioactive materials contained in living organisms, an
 

additional consideration is made for the reduction in observed activity due to
 

regular processes of elimination of the respective chemical or biochemical
 

substance from the organism. This introduces a rate constant called the
 
115
 

APPENDIX B
 

biological half-life (Tbiol) which is the time required for biological 

processes to eliminate one-half of the activity. This time is virtually the
 

same for both stable and radioactive isotopes of any given element.
 

Under such conditions the time required for a radioactive element to be
 

halved as a result of the combined action of radioactive decay and biological
 

elimination is the effective half-life:
 

Teff = (Tbiol x Trad)/(Tbiol + Trad). 

Table B-2 presents representative effective half-lives of particular interest.
 

B.2.3 Interaction of Radiation with Matter
 

Both ionizing and nonionizing radiation will interact with materials,
 

that is, it will lose kinetic energy to any solid, liquid or gas through which
 

it passes by a variety of mechanisms. The transfer of energy to a medium by
 

either electromagnetic or particulate radiation may be sufficient to cause
 

formation of ions. This process is called ionization. Compared to other
 

types of radiation that may be absorbed, such as ultraviolet radiation,
 

ionizing radiation deposits a relatively large amount of energy into a small
 

volume.
 

The method by which incident radiation interacts with the medium to cause
 

ionization may be direct or indirect. Electromagnetic radiations (X-rays and
 

gamma photons) are indirectly ionizing; that is, they give up their energy in
 

various interactions with cellular molecules, and the energy is then utilized
 

to produce a fast-moving charged particle such as an electron. It is the
 

electron that then secondarily may react with a target molecule. Charged
 

particles, in contrast, strike the tissue or medium and directly react with
 

target molecules, such as oxygen or water. These particulate radiations are
 

directly ionizing radiations. Examples of directly ionizing particles include
 

alpha and beta particles. Indirectly ionizing radiations are always more
 

penetrating than directly ionizing particulate radiations.
 

Mass, charge, and velocity of a particle all affect the rate at which
 

ionization occurs. The higher the charge of the particle and the lower the
 

velocity, the greater the propensity to cause ionization. Heavy, highly
 

charged particles, such as alpha particles, lose energy rapidly with distance
 

and, therefore, do not penetrate deeply. The result of these interaction
 

processes is a gradual slowing down of any incident particle until it is
 

brought to rest or "stopped" at the end of its range.
 

B-2.4 Characteristics of Emitted Radiation
 

B.2.4.1 Alpha Emission. In alpha emission, an alpha particle consisting
 

of two protons and two neutrons is emitted with a resulting decrease in the
 

117
 

APPENDIX B
 

atomic mass number by four and reduction of the atomic number by two, thereby
 

changing the parent to a different element. The alpha particle is identical
 

to a helium nucleus consisting of two neutrons and two protons. It results
 

from the radioactive decay of some heavy elements such as uranium, plutonium,
 

radium, thorium, and radon. Alpha particles have a large mass as compared to
 

electrons. Decay of alpha-emitting radionuclides may result in the emission
 

of several different alpha particles. A radionuclide has an alpha emission
 

with a discrete alpha energy and characteristic pattern of alpha energy
 

emitted.
 

The alpha particle has an electrical charge of +2. Because of this
 

double positive charge, alpha particles have great ionizing power, but their
 

large size results in very little penetrating power. In fact, an alpha
 

particle cannot penetrate a sheet of paper. The range of an alpha particle,
 

that is, the distance the charged particle travels from the point of origin to
 

its resting point, is about 4 cm in air, which decreases considerably to a few
 

micrometers in tissue. These properties cause alpha emitters to be hazardous
 

only if there is internal contamination (i.e., if the radionuclide is
 

ingested, inhaled, or otherwise absorbed).
 

B.2.4.2. Beta Emission. Nuclei which are excessively neutron rich decay
 

by B-decay. A beta particle (ß) is a high-velocity electron ejected from a
 

disintegrating nucleus. The particle may be either a negatively charged
 

electron, termed a negatron (ß-) or a positively charged electron, termed a
 

positron (R+). Although the precise definition of "beta emission" refers to
 

both fi- and D+, common usage of the term generally applies only to the
 

negative particle, as distinguished from the positron emission, which refers
 

to the 13+ particle.
 

B.2.4.2.1 Beta Negative Emission. Beta particle (ß-) emission is
 

another process by which a radionuclide, usually those with a neutron excess,
 

achieves stability. Beta particle emission decreases the number of neutrons
 

by one and increases the number of protons by one, while the atomic mass
 

remains unchanged. This transformation results in the formation of a
 

different element. The energy spectrum of beta particle emission ranges from
 

a certain maximum down to zero with the mean energy of the spectrum being
 

about one-third of the maximum. The range in tissue is much less. Beta
 

negative emitting radionuclides can cause injury to the skin and superficial
 

body tissues but mostly present an internal contamination hazard.
 

B-2.4.2.2 Positron Emission. In cases in which there are too many
 

protons in the nucleus, positron emission may occur. In this case a proton
 

may be thought of as being converted into a neutron, and a positron (ß+) is
 

emitted, accompanied by a neutrino (see glossary). This increases the number
 

of neutrons by one, decreases the number of protons by one, and again leaves
 

the atomic mass unchanged. The gamma radiation resulting from the
 

annihilation (see glossary) of the positron makes all positron emitting
 

isotopes more of an external radiation hazard than pure 13 emitters of equal
 

energy.
 
118
 

APPENDIX B
 

B.2.4.2.3 Gamma Emission. Radioactive decay by alpha, beta, positron
 

emission or electron capture often leaves some of the energy resulting from
 

these changes in the nucleus. As a result, the nucleus is raised to an
 

excited level. None of these excited nuclei can remain in this high-energy
 

state. Nuclei release this energy returning to ground state or to the lowest
 

possible stable energy level. The energy released is in the form of gamma
 

radiation (high energy photons) and has an energy equal to the change in the
 

energy state of the nucleus. Gamma and X-rays behave similarly but differ in
 

their origin; gamma emissions originate in the nucleus while X-rays originate
 

in the orbital electron structure.
 

B.3 ESTIMATION OF ENERGY DEPOSITION IN HUMAN TISSUES
 

Two forms of potential radiation exposures can result -- internal and
 

external. The term exposure denotes physical interaction of the radiation
 

emitted from the radioactive material with cells and tissues of the human
 

body. An exposure can be "acute" or "chronic" depending on how long an
 

individual or organ is exposed to the radiation. Internal exposures occur
 

when radionuclides, which have entered the body (e.g., through the inhalation,
 

ingestion, or dermal pathways), undergo radioactive decay resulting in the
 

deposition of energy to internal organs. External exposures occur when
 

radiation enters the body directly from sources located outside the body, such
 

as radiation emitters from radionuclides on ground surfaces, dissolved in
 

water, or dispersed in the air. In general, external exposures are from
 

material emitting gamma radiation, which readily penetrate the skin and
 

internal organs. Beta and alpha radiation from external sources are far less
 

penetrating and deposit their energy primarily on the skin's outer layer.
 

Consequently, their contribution to the absorbed dose of the total body dose,
 

compared to that deposited by gamma rays, may be negligible.
 

Characterizing the radiation dose to persons as a result of exposure to
 

radiation is a complex issue. It is difficult to: (1) measure internally the
 

amount of energy actually transferred to an organic material and to correlate
 

any observed effects with this energy deposition; and (2) account for and
 

predict secondary processes, such as collision effects or biologically
 

triggered effects, that are an indirect consequence of the primary interaction
 

event.
 

B.3.1 Dose Units
 

B.3.1.1 Roentgen. The roentgen (R) is a unit of exposure related to the 

amount of ionization caused in air by gamma or x-radiation. One roentgen 

equals 2.58x10-4 Coulomb per kilogram of air. In the case of gamma radiation, 

over the commonly encountered range of photon energy, the energy deposition in 

tissue for a dose of 1 R is about 0.0096 joules(J)/kg of tissue. 

B.3.1.2 Absorbed Dose and Absorbed Dose Rate. Since different types of
 

radiation interact differently with any material through which they pass, any
 
119
 

APPENDIX B
 

attempt to assess their effect on humans or animals should take into account
 

these differences. The absorbed dose is defined as the energy imparted by the
 

incident radiation to a unit mass of the tissue or organ. The unit of
 

absorbed dose is the rad; 1 rad = 100 erg/gram = 0.01 J/kg in any medium. The
 

SI unit is the gray which is equivalent to 100 rad or 1 J/kg. Internal and
 

external exposures from radiation sources are not usually instantaneous but
 

are distributed over extended periods of time. The resulting rate of change
 

of the absorbed dose to a small volume of mass is referred to as the absorbed
 

dose rate in units of rad/unit time.
 

B.3.1.3 Working Levels and Working Level Months. Working levels are 

units that have been used to describe the radon decay-product activities in 

air in terms of potential alpha energy. It is defined as any combination of 

short-lived radon daughters (through polonium-214) per liter of air that will 

result in the emission of 1.3x105

 MeV of alpha energy. An activity 

concentration of 100 pCi radon-222/L of air, in equilibrium with its 

daughters, corresponds approximately to a potential alpha-energy concentration 

of 1 WL. The WL unit can also be used for thoron daughters. In this case, 

1.3x105 MeV of alpha energy (1 WL) is released by the thoron daughters in 

equilibrium with 7.5 pCi thoron/L. The potential alpha energy exposure of 

miners is commonly expressed in the unit Working Level Month (WIN). One WLM 

corresponds to exposure to a concentration of 1 WL for the reference period of 

170 hours. 

B.3.2 Dosimetry Models
 

Dosimetry models are used to estimate the internally deposited dose from
 

exposure to radioactive substances. The models for internal dosimetry
 

consider the quantity of radionuclides entering the body, the factors
 

affecting their movement or transport through the body, distribution and
 

retention of radionuclides in the body, and the energy deposited in organs and
 

tissues from the radiation that is emitted during spontaneous decay processes.
 

The models for external dosimetry consider only the photon doses to organs of
 

individuals who are immersed in air or are exposed to a contaminated ground
 

surface. The dose pattern for radioactive materials in the body may be
 

strongly influenced by the route of entry of the material. For industrial
 

workers, inhalation of radioactive particles with pulmonary deposition and
 

puncture wounds with subcutaneous deposition have been the most frequent. The
 

general population has been exposed via ingestion and inhalation of low levels
 

of naturally occurring radionuclides as well as man-produced radionuclides
 

from nuclear weapons testing.
 

B.3.2.1 Ingestion. Ingestion of radioactive materials is most likely to
 

occur from contaminated foodstuffs or water or eventual ingestion of inhaled
 

compounds initially deposited in the lung. Ingestion of radioactive material
 

may result in toxic effects as a result of either absorption of the
 

radionuclide or irradiation of the gastrointestinal tract during passage
 

through the tract, or a combination of both. The fraction of a radioactive
 
120
 

APPENDIX B
 

material absorbed from the gastrointestinal tract is variable, depending on
 

the specific element, the physical and chemical form of the material ingested,
 

and the diet, as well as some other metabolic and physiological factors. The
 

absorption of some elements is influenced by age usually with higher
 

absorption in the very young.
 

B.3.2.2 Inhalation. The inhalation route of exposure has long been
 

recognized as being of major importance for both nonradioactive and
 

radioactive materials. The deposition of particles within the lung is largely
 

dependent upon the size of the particles being inhaled. After the particle is
 

deposited, the retention will depend upon the physical and chemical properties
 

of the dust and the physiological status of the lung. The retention of the
 

particle in the lung depends on the location of deposition, in addition to the
 

physical and chemical properties of the particles. The converse of pulmonary
 

retention is pulmonary clearance. There are three distinct mechanisms of
 

clearance which operate simultaneously. Giliary clearance acts only in the
 

upper respiratory tract. The second and third mechanisms act mainly in the
 

deep respiratory tract. These are phagocytosis and absorption. Phagocytosis
 

is the engulfing of foreign bodies by alveolar macrophages and their
 

subsequent removal either up the ciliary "escalator" or by entrance into the
 

lymphatic system. Some inhaled soluble particulates are absorbed into the
 

blood and translocated to other organs and tissues. Dosimetric lung models
 

are reviewed by James (1987) and James and Roy (1987).
 

B.3.3 Internal Emitters
 

The absorbed dose from internally deposited radioisotopes is the energy
 

absorbed by the surrounding tissue. For a radioisotope distributed uniformly
 

throughout an infinitely large medium, the concentration of absorbed energy
 

must be equal to the concentration of energy emitted by the isotope. An
 

infinitely large medium may be approximated by a tissue mass whose dimensions
 

exceed the range of the particle. All alpha and most beta radiation will be
 

absorbed in the organ (or tissue) of reference. Gamma-emitting isotope
 

emissions are penetrating radiation and a substantial fraction may travel
 

great distances within tissue, leaving the tissue without interacting. The
 

dose to an organ or tissue is a function of the effective retention half-time,
 

the energy released in the tissue, the amount of radioactivity initially
 

introduced, and the mass of the organ or tissue.
 

B.4 BIOLOGICAL EFFECTS OF RADIATION
 

When biological material is exposed to ionizing radiation, a chain of
 

cellular events occurs as the ionizing particle passes through the biological
 

material. A number of theories have been proposed to describe the interaction
 

of radiation with biologically important molecules in cells and to explain the
 

resulting damage to biological systems from those interactions. Many factors
 

may modify the response of a living organism to a given dose of radiation.
 

Factors related to the exposure include the dose rate, the energy of the
 
121
 

APPENDIX B
 

radiation, and the temporal pattern of the exposure. Biological
 

considerations include factors such as species, age, sex, and the portion of
 

the body exposed. Several excellent reviews of the biological effects of
 

radiation have been published, and the reader is referred to these for a more
 

in-depth discussion (Hobbs and McClellan 1986; ICRP 1984; Mettler and Moseley
 

1985; Rubin and Casarett 1968).
 

B.4.1 Radiation Effects at the Cellular Level
 

According to Mettler and Moseley (1985), at acute doses up to 10 rad (100
 

mGy), single strand breaks in DNA may be produced. These single strand breaks
 

may be repaired rapidly. With doses in the range of 50 to 500 rad (0.5 to 5
 

Gy) , irreparable double-stranded DNA breaks are likely, resulting in cellular
 

reproductive death after one or more divisions of the irradiated parent cell.
 

At large doses of radiation, usually greater than 500 rad (5 Gy), direct cell
 

death before division (interphase death) may occur from the direct interaction
 

of free-radicals with essentially cellular macromolecules. Morphological
 

changes at the cellular level, the severity of which are dose-dependent, may
 

also be observed.
 

The sensitivity of various cell types varies. According to the Bergonig-


Tribondeau law, the sensitivity of cell lines is directly proportional to
 

their mitotic rate and inversely proportional to the degree of differentiation
 

(Mettler and Moseley 1985). Rubin and Casarett (1968) devised a
 

classification system that categorized cells according to type, function, and
 

mitotic activity. The categories range from the most sensitive type,
 

"vegetative intermitotic cells," found in the stem cells of the bone marrow
 

and the gastrointestinal tract, to the least sensitive cell type, "fixed
 

postmitotic cells," found in striated muscles or long-lived neural tissues.
 

Cellular changes may result in cell death, which if extensive, may
 

produce irreversible damage to an organ or tissue or may result in the death
 

of the individual. If the cell recovers, altered metabolism and function may
 

still occur, which may be repaired or may result in the manifestation of
 

clinical symptoms. These changes may also be expressed at a later time as
 

tumors or mutations.
 

B.4.2 Radiation Effects at the Organ Level
 

In most organs and tissues the injury and the underlying mechanism for
 

that injury are complex and may involve a combination of events. The extent
 

and severity of this tissue injury are dependent upon the radiosensitivity of
 

the various cell types in that organ system. Rubin and Casarett (1968)
 

describe and schematically display the events following radiation in several
 

organ system types. These include: a rapid renewal system, such as the
 

gastrointestinal mucosa; a slow renewal system, such as the pulmonary
 

epithelium; and a nonrenewal system, such as neural or muscle tissue. In the
 

rapid renewal system, organ injury results from the direct destruction of
 

highly radiosensitive cells, such as the stem cells in the bone marrow.
 
122
 

APPENDIX B
 

Injury may also result from constriction of the microcirculation and from
 

edema and inflammation of the basement membrane (designated as the
 

histohematic barrier - HHB), which may progress to fibrosis. In slow renewal
 

and nonrenewal systems, the radiation may have little effect on the
 

parenchymal cells, but ultimate parenchymal atrophy and death over several
 

months result from HHB fibrosis and occlusion of the microcirculation.
 

B.4.3 Acute and Chronic Somatic Effects
 

B.4.3.1 Acute Effects. The result of acute exposure to radiation is
 

commonly referred to as acute radiation syndrome. This effect is seen only
 

after exposures to relatively high doses (>50 rad), which would only be
 

expected to occur in the event of a serious nuclear accident. The four stages
 

of acute radiation syndrome are prodrome, latent stage, manifest illness
 

stage, recovery or death. The initial phase is characterized by nausea,
 

vomiting, malaise and fatigue, increased temperature, and blood changes. The
 

latent stage is similar to an incubation period. Subjective symptoms may
 

subside, but changes may be taking place within the blood-forming organs and
 

elsewhere which will subsequently give rise to the next stage. The manifest
 

illness stage gives rise to symptoms specifically associated with the
 

radiation injury. Among these symptoms are hair loss, fever, infection,
 

hemorrhage, severe diarrhea, prostration, disorientation, and cardiovascular
 

collapse. The symptoms and their severity depend upon the radiation dose
 

received.
 

B.4.3.2 Delayed Effects. The level of exposure to radioactive
 

pollutants that may be encountered in the environment is expected to be too
 

low to result in the acute effects described above. When one is exposed to
 

radiation in the environment, the amount of radiation absorbed is more likely
 

to produce long-term effects, which manifest themselves years after the
 

original exposure, and may be due to a single large over-exposure or
 

continuing low-level exposure.
 

Sufficient evidence exists in both human populations and laboratory
 

animals to establish that radiation can cause cancer and that the incidence of
 

cancer increases with increasing radiation dose. Human data are extensive and
 

include epidemiological studies of atomic bomb survivors, many types of
 

radiation-treated patients, underground miners, and radium dial painters.
 

Reports on the survivors of the atomic bomb explosions at Hiroshima and
 

Nagasaki, Japan (with whole-body external radiation doses of 0 to more than
 

200 rad) indicate that cancer mortality has increased (Kato and Schull 1982).
 

Use of X-rays (at doses of approximately 100 rad) in medical treatment for
 

ankylosing spondylitis or other benign conditions or diagnostic purposes, such
 

as breast conditions, has resulted in excess cancers in irradiated organs
 

(BEIR 1980, 1990; UNSCEAR 1977, 1988). Cancers, such as leukemia, have been
 

observed in children exposed in utero to doses of 0.2 to 20 rad (BEIR, 1980,
 

1990; UNSCEAR 1977, 1988). Medical use of Thorotrast (colloidal thorium
 

dioxide) resulted in increases in the incidence of cancers of the liver, bone,
 
123
 

APPENDIX B
 

and lung (ATSDR 1990a; BEIR 1980, 1990; UNSCEAR 1977, 1988). Occupational
 

exposure to radiation provides further evidence of the ability of radiation to
 

cause cancer. Numerous studies of underground miners exposed to radon and
 

radon daughters, which are alpha emitters, in uranium and other hard rock
 

mines have demonstrated increases in lung cancer in exposed workers (ATSDR
 

1990b). Workers who ingested radium-226 while painting watch dials had an
 

increased incidence of leukemia and bone cancer (ATSDR 199Oc). These studies
 

indicate that depending on radiation dose and the exposure schedule, ionizing
 

radiation can induce cancer in nearly any tissue or organ in the body.
 

Radiation-induced cancers in humans are found to occur in the hemopoietic
 

system, the lung, the thyroid, the liver, the bone, the skin, and other
 

tissues.
 

Laboratory animal data indicate that ionizing radiation is carcinogenic
 

and mutagenic at relatively high doses usually delivered at high dose rates.
 

However, due to the uncertainty regarding the shape of the dose-response
 

curve, especially at low doses, the commonly held conservative position is
 

that the cancer may occur at dose rates that extend down to doses that could
 

be received from environmental exposures. Estimates of cancer risk are based
 

on the absorbed dose of radiation in an organ or tissue. The cancer risk at a
 

particular dose is the same regardless of the source of the radiation. A
 

comprehensive discussion of radiation-induced cancer is found in BEIR IV
 

(1988), BEIR V (1990), and UNSCEAR (1982, 1988).
 

B.4.4 Genetic Effects
 

Radiation can induce genetic damage, such as gene mutations or
 

chromosomal aberrations, by causing changes in the structure, number, or
 

genetic content of chromosomes in the nucleus. The evidence for the
 

mutagenicity of radiation is derived from studies in laboratory animals,
 

mostly mice (BEIR 1980, 1988, 1990; UNSCEAR 1982, 1986, 1988). Evidence for
 

genetic effects in humans is derived from tissue cultures of human lymphocytes
 

from persons exposed to ingested or inhaled radionuclides (ATSDR 199Oc,
 

1990d). Evidence for mutagenesis in human germ cells (cells of the ovaries or
 

testis) is not conclusive (BEIR 1980, 1988, 1990; UNSCEAR 1977, 1986, 1988).
 

Chromosome aberrations following radiation exposure have been demonstrated in
 

man andn in experimental animals (BEIR 1980, 1988, 1990; UNSCEAR 1982, 1986,
 

1988).
 

B.4.5 Teratogenic Effects
 

There is evidence that radiation produces teratogenicity in animals. It
 

appears that the developing fetus is more sensitive to radiation than the
 

mother and is most sensitive to radiation-induced damage during the early
 

stages of organ development. The type of malformation depends on the stage of
 

development and the cells that are undergoing the most rapid differentiation
 

at the time. Studies of mental retardation in children exposed in utero to
 

radiation from the atomic bomb provide evidence that radiation may produce
 
124
 

APPENDIX B
 

teratogenic effects in human fetuses (Otake and Schull 1984). The damage to
 

the child was found to be related to the dose that the fetus received.
 

B.5 UNITS IN RADIATION PROTECTION AND REGULATION
 

B.5.1 Dose Equivalent and Dose Equivalent Rate. Dose equivalent or rem
 

is a special radiation protection quantity that is used to express the
 

absorbed dose in a manner which considers the difference in biological
 

effectiveness of various kinds of ionizing radiation. The ICRU has defined
 

the dose equivalent, H, as the product of the absorbed dose, D, the quality
 

factor, Q, and all other modifying factors, N, at the point of interest in
 

biological tissue. This relationship is expressed as follows:
 

H = D x Q x N.
 

The quality factor is a dimensionless quantity that depends in part on the
 

stopping power for charged particles, and it accounts for the differences in
 

biological effectiveness found among the types of radiation. By definition it
 

is independent of tissue and biological end point and, therefore, of little
 

use in risk assessment now. Originally Relative Biolotical Effectiveness
 

(RBE) was used rather than Q to define the quantity, rem, which was of use in
 

risk assessment. The generally accepted values for quality factors for
 

various radiation types are provided in Table B-3. The dose equivalent rate
 

is the time rate of change of the dose equivalent to organs and tissues and is
 

expressed as rem/unit time or sievert/unit time.
 

B.5.2 Relative Biological Effectiveness. The term relative biologic
 

effectiveness (RBE) is used to denote the experimentally determined ratio of
 

the absorbed dose from one radiation type to the absorbed dose of a reference
 

radiation required to produce an identical biologic effect under the same
 

conditions. Gamma rays from cobalt-60 and 200 to 250 KeV X-rays have been
 

used as reference standards. The term RBE has been widely used in
 

experimental radiobiology, and the term quality factor used in calculations of
 

dose equivalents for radiation protection purposes (ICRP 1977; NCRP 1971;
 

UNSCEAR 1982). The generally accepted values for RBE are provided in Table
 

B-4.
 

B.5.3 Effective Dose Equivalent and Effective Dose Equivalent Rate. The
 

absorbed dose is usually defined as the mean absorbed dose within an organ or
 

tissue. This represents a simplification of the actual problem. Normally
 

when an individual ingests or inhales a radionuclide or is exposed to external
 

radiation that enters the body (gamma), the dose is not uniform throughout the
 

whole body. The simplifying assumption is that the detriment will be the same
 

whether the body is uniformly or nonuniformly irradiated. In an attempt to
 

compare detriment from absorbed dose of a limited portion of the body with the
 

detriment from total body dose, the ICRP (1977) has derived a concept of
 

effective dose equivalent.
 


 

127
 

APPENDIX B
 

The effective dose equivalent, HE is
 

HE = (the sum of) Wt Ht 

where Ht is the dose equivalent in the tissue, Wt is the weighting factor,
 

which represents the estimated proportion of the stochastic risk resulting
 

from tissue, T, to the stochastic risk when the whole body is uniformly
 

irradiated for occupational exposures under certain conditions (ICRP 1977).
 

Weighting factors for selected tissues are listed in Table B-5.
 

The ICRU (1980), ICRP (1984), and NCRP (1985) now recommend that the rad,
 

roentgen, curie and rem be replaced by the SI units: gray (GY), Coulomb per
 

kilogram (C/kg), becquerel (Bq), and sievert (Sv), respectively. The
 

relationship between the customary units and the international system of units
 

(SI) for radiological quantities is shown in Table B-6.
 



131
 

APPENDIX B
 

References
 

ATSDR. 1990a. Toxicological profile for thorium. U.S. Department of Health
 

and Human Services. Public Health Service. Agency for Toxic Substances and
 

Disease Registry. Atlanta, GA.
 

ATSDR. 1990b. Toxicological profile for radium. U.S. Department of Health
 

and Human Services. Public Health Service. Agency for Toxic Substances and
 

Disease Registry. Atlanta, GA.
 

ATSDR. 199oc. Toxicological profile for radon. U.S. Department of Health
 

and Human Services. Public Health Service. Agency for Toxic Substances and
 

Disease Registry. Atlanta, GA.
 

ATSDR. 1990d. Toxicological profile for uranium. U.S. Department of Health
 

and Human Services. Public Health Service. Agency for Toxic Substances and
 

Disease Registry. Atlanta, GA.
 

BEIR III. 1980. The effects on populations of exposure to low levels of
 

ionizing radiation. Committee on the Biological Effects of Ionizing
 

Radiations, National Research Council. Washington, DC: National Academy
 

Press.
 

BEIR IV. 1988. Health risks of radon and other internally deposited alpha
 

emitters. Committee on the Biological Effects of Ionizing Radiations,
 

National Research Council. Washington, DC: National Academy Press.
 

BEIR V. 1990. Health effects of exposure to low levels of ionizing
 

radiation. Committee on the Biological Effects of Ionizing Radiations,
 

National Research Council. Washington, DC: National Academy Press.
 

Early P, Razzak M, Sodee D. 1979. Nuclear medicine technology. 2nd ed. St.
 

Louis: C.V. Mosby Company.
 

Eichholz G. 1982. Environmental aspects of nuclear power. Ann Arbor, MI:
 

Ann Arbor Science.
 

Hendee W. 1973. Radioactive isotopes in biological research. New York, NY:
 

John Wiley and Sons.
 

Hobbs C, McClellan R. 1986. Radiation and radioactive materials. In: Doull
 

J, et al., eds. Casarett and Doull's Toxicology. 3rd ed. New York, NY:
 

Macmillan Publishing Co., Inc., 497-530.
 

ICRP. 1977. International Commission on Radiological Protection.
 

Recommendations of the International Commission on Radiological Protection.
 

ICRP Publication 26. Vol 1. No. 3. Oxford: Pergamon Press.
 
132
 

APPENDIX B
 

ICRP. 1979. International Commission on Radiological Protection. Limits for
 

intakes of radionuclides by workers. ICRP Publication 20. Vol 3. No. l-4.
 

Oxford: Pergamon Press.
 

ICRP. 1984. International Commission on Radiological Protection. A
 

compilation of the major concepts and quantities in use by ICRP. ICRP
 

Publication 42. Oxford: Pergamon Press.
 

ICRU. 1980. International Commission on Radiation Units and Measurements
 

ICRU Report No. 33. Washington, DC.
 

James A. 1987. A reconsideration of cells at risk and other key factors in
 

radon daughter dosimetry. In: Hopke P, ed. Radon and its decay products:
 

Occurrence, properties and health effects. ACS Symposium Series 331.
 

Washington, DC: American Chemical Society, 400-418.
 

James A, Roy M. 1987. Dosimetric lung models. In: Gerber G, et al., ed.
 

Age-related factors in radionuclide metabolism and dosimetry. Boston:
 

Martinus Nijhoff Publishers, 95-108.
 

Kato H, Schull W. 1982. Studies of the mortality of A-bomb survivors. Report
 

7 Part 1, Cancer mortality among atomic bomb survivors, 1950-78. Radiat Res
 

90:395-432.
 

Mettler F, Moseley R. 1985. Medical effects of ionizing radiation. New
 

York: Grune and Stratton.
 

NCRP 1971. National Council on Radiation Protection and Measurements. Basic
 

radiation protection criteria. NCRP Report No. 39. Washington, DC.
 

NCRP. 1985. A handbook of radioactivity measurements procedures. 2nd ed.
 

Bethesda, MD: National Council on Radiation Protection and Measurements.
 

NCRP Report No. 58.
 

Otake M, Schull W. 1984. Mental retardation in children exposed in utero to
 

the atomic bombs: A reassessment. Technical Report RERF TR l-83, Radiation
 

Effects Research Foundation, Japan.
 

Rubin P, Casarett G. 1968. Clinical radiation pathology. Philadelphia: W.B.
 

Sanders Company, 33.
 

UNSCEAR. 1977. United Nations Scientific Committee on the Effects of Atomic
 

Radiation. Sources and effects of ionizing radiation. New York: United
 

Nations.
 

UNSCEAR. 1982. United Nations Scientific Committee on the Effects of Atomic
 

Radiation. Ionizing radiation: Sources and biological effects. New York:
 

United Nations.
 
133
 

APPENDIX B
 

UNSCEAR. 1986. United Nations Scientific Committee on the Effects of Atomic
 

Radiation. Genetic and somatic effects of ionizing radiation. New York:
 

United Nations.
 

UNSCEAR. 1988. United Nations Scientific Committee on the Effects of Atomic
 

Radiation. Sources, effects and risks of ionization radiation. New York:
 

United Nations.