MEMORANDUM

SUBJECT : Documents developed in connection with external peer review of the EPA's report t itled “ Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds ”

FROM : Ines Pagan Health and Environmental Impacts Division Air Toxics Assessments Group

TO : Mercury and Air Toxics Standards Rule docket EPA

- HQ

- OAR

- 2009

- 0234

The documents included in the attached p df file were developed in connection with the external peer review of the EPA's report titled “ Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds ” in support of EPA’s recently proposed ( March 2011 ) Mercury and Air Toxics Standards (MATS) Rule

. These materials includ e the following documents: 1) an external peer review report of chromium and nickel methods (May 2011), and associated attachments (A and B)

, 2 ) charge que stions for the peer reviewers, 3 ) charge responses by three external peer reviewers, and 4 ) a summary of the peer review including rev iewers recommendations and EPA ’ s conclusions based on reviewers’ recommendations.**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

1 

### M **ethods to D**  **evelop I**  **nhalation C**  **ancer R**  **isk E**  **stimates for**

**C hromium and**  **N ickel**  **C ompounds** 

**1 Purpose**  The purpose of this paper is to discuss the methods used to devel op inhalation cancer risk

estimates associated with emissions of chromium and nickel compounds f rom coal and oil

- fired electric utility steam generating units ( EGUs ) in support of EPA’s recently proposed Air Toxics Rule

. 1 The

derivation of cancer risk estimates is based on the s peciation data available from selected source categories

, and on the ava ilable unit risk estimates (UREs) reflect ing the dose that correspond s to a specific level of cancer risk. This document includes d iscussion s for both emissions of chrom ium (S ection 2) and nickel (S ection 3) compounds with regards to ( 1) the methods and rationale used in previous analys e s (where applicable)

, ( 2) the methods used in the recent analysis for the Air Toxics Rule (considering previous methods and currently available data ), and ( 3) a discussion of the uncertainties

and/or limitations of th e met hods used

. In this document, we consider the emissions of chromium compounds from both coal

- and oil

- fired EGUs and the emissions of nickel compounds from oil

- fired

EGUs
, since the se are major contributors to inhalation cancer risk estimates from each of these source
types

.



### 2 **Chromium and**  **C ompounds** 

**2.1 Background**  Chromium compounds occur in nature and are found primarily in the earth’s crust. The largest
source of chromium is the ore mineral chromite, FeC r 2 O 4 or MgCr 2 O 4 , where magnesium can substitute

for iro n

. 2

1 US EPA, 2011 . National Emission Standards for Hazardous Air Pollutants from Coal

- and Oil

- fired Elect ric Utility Steam Generating Units and Standards of Performance for Fossil

- Fuel

- Fired Electric Utility, Industrial

- commercial

- Institutional, and Small Industrial

- Commercial

- Institutional Steam Generating Units Rule. Available online at Chromium can also be found in small concentrations in certain types of igneous rocks, coal, tar, asphalt, and crude oil. Chromium oxidation valences vary from

– 2 to +6 , but only the 0, +2, +3 and +6

http://www.epa.gov/ttn/atw/utility/utilitypg.html

. 2 Guer tin, Jacques, James A. Jacobs and Cynthia P. Avakian. Chromium (VI) Handbook. Independent Environmental Technical Evaluation Group (IETEG). CRC Press
, 20 05 . ISBN 9781566706087**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

2 valence states are common. 3 However, the hexaval ent state ( Cr +6 )
, also denoted as Cr (VI)

, rarely occurs naturally, and is usually produce d from anthropogenic sources (US EPA 1984). 4 The trivalent state (Cr +3 )
, also denoted as Cr (III)

, and t he Cr ( VI ) state are the first and second most stable, respect ively, and thus the forms considered more important with regards to human health. 5
Chromium compounds are used in a variety of industrial applications and operations. They are

used in : alloys, such as stainless steel; paint pigments; refractory bricks t hat line furnaces and kilns; wood preservatives; production and processing of insoluble salts; leather tanning; catalysts for halogenation, alkylation, and catalytic cracking of hydrocarbons; fuel and propellant additives; and more

. 6 Many of these applica tions use substances containing Cr ( VI ) compounds, including various chromates,
dichromates, and chromic acid. 7 D isposal of chemicals containing chromium or burning fossil fuels can
also release chromium to the air, soil and water. In addition, some indus trial processes may produce chromium emissions, wherein the hexavalent state is favored in an oxidizing alkaline environment, and the trivalent state is favored in a reducing acidic environment. 8

In its 1998 the Integrated Risk Information System ( IRIS ) Toxicological Review, the U.S. EPA

classified C r( VI ) , including its compounds

, as “a known human carcinogen by the inhalation route of exposure” based on evidenc e from occupational epidemi o logical studies consistently indicati ng dose

dependent associations between chromium inhalation exposure and lung cancer, and on supporting

evidence from animal inhalation studies (EPA, 1998) However the exact distribution between

the hexavalent and t rivalent chromium states is unknown.

9

3 Dayan AD and Paine AJ. Mechanisms of chromium toxicity, carcinogenicity and allergenicity: review of the literature from 1985 to 2000

. Hum and Experiment Toxicol 2001, 20:439

- 4 51. . With regards to trivalent chromi um Cr ( III), the

1998 IRIS T oxicological Review notes that while the evidence from the occupational database “ could be used to suggest that total chromium is carcinogenic by inhalation, animal data support the human carcinogenicity data only on hexavalent c hromium”. Thus, based on these considerations the EPA

conclude d that only Cr(VI) should be classified as a human carcinogen via the inhalation route of

4 US EPA, 1984 . Health assessment document for ch romium. Research Triangle Park, NC: Environmental Assessment and Criteria Office, U.S. Environmental Protection Agency. EPA600883014F

. 5 Dayan AD and Paine AJ. Mechanisms of chromium toxicity, carcinogenicity and allergenicity: review of the literature fr om 1985 to 2000

. Hum and Experiment Toxicol 2001, 20:439

- 451

. 6 Guer tin, Jacques, James A. Jacobs and Cynthia P. Avakian, 2005. Chromium (VI) Handbook. Independent Environmental Technical Evaluation Group (IETEG). CRC Press. ISBN 9781566706087

7 Agency for Toxic Substances and Disease Registry (ATSDR), 199 3

. Toxicological Fact Sheet for chromium . Avail a ble online at www.nativeknowledge.org/db/files/tfacts7.htm

8 Guer tin, Jacques, James A. Jacobs and Cynthia P. Avakian. Chromium (VI) Handbook. Independen t Environmental Technical Evaluation Group (IETEG). CRC Press , 2005 . ISBN 9781566706087

9 US EPA, 1998. Integrated Risk Information S ystem (IRIS) assessment for hexavalent chromium. Available at: http://www.epa.gov/ncea/iris/subst/0144.htm

.**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

3 exposure

. 10 EPA is currently reevaluating the carcinogenicity of hexavalent chromium via the oral rout e of exposure in light of a 2

- year chronic bioassay conducted by the National Toxicology Program (NTP) concluding that Cr(VI) is carcinogenic when ingested in drinking water. The International Agency for Research on Carcinogenicity, or IARC
, conclude d tha t there is sufficient evidence for the carcinogenicity of Cr(VI) compounds in humans based on the combined evidence from the epidemiological, animal and

mechanistic data available. In agreement with the EPA, the IARC state d that compounds of chromium III are not classifiable as to their carcinogenicity

. 11 Scientific views similar to those of EPA and IARC are

reflected in the NTP’s 11 th R eport of the C arcinogens

. 12

The inhalation unit risk estimate ( URE ) for Cr (VI) on IRIS is 0.012 per μg/m 3 , which means th at inhaling Cr ( VI ) in air at an average concentration of 1 μg/m 3 daily for a lifetime poses an estimated
increased risk of cancer of 12,000 in a million. 13 This inhalation cancer potency value is among the highest values of any of the hazardous air polluta nts (HAP ) listed in the Clean Air Act.



### 2.2 **Approach for E**  **stimating I**  **nhalation C**  **ancer R**  **isks from C**  **hromium**
**C ompounds**  Based on the information in the previous section, we estimate cancer risks due to the inhalation of all chromium compounds based on the exposu re concentration of Cr(VI) alone. Thus:

Risk = EC Cr(VI) * 0.012 (ug/m 3 ) - 1

W here

EC Cr(VI) is the chronic exposure concentration estimate for hexavalent chromium and 0.012 (ug/m 3 ) - 1 is the cancer unit risk estimate for hexavalent chromium. In terms of c hronic inhalation exposure to total chromium compounds, we need to know the mass percentage of the total chromium

mixture which is hexavalent in order to estimate chronic cancer risks. Thus:

10 US EPA, 1 998 Integrated Risk Information System (IRIS) assessment for hexavalent chromium. Available online
at http://www.epa.gov/iris/subst/0144.htm

. 11 International Agency for Research on Cancer ( IARC ) , 1990. IARC monographs on the evaluation of carcinogenic ri sks to humans. Chromium, nickel and welding. Vol. 49. Lyons, France: International Agency for Research on Cancer, World Health Organization 49

- 256

. 12 National Toxicology Program ( NTP ) , 2005. Report on carcinogens. 11th ed . Research Triangle Park, NC: US De partment of Health and Human Serv ices (DHHS), Public Health Service . Available at http:// http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s045chro.pdf

. 13 US EPA, 1998. Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating U nits

– Final Report to Congress. US EPA #453/R

- 98

- 004. Available at http://www.epa.gov/ttn/caaa/t3rc.html.**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

4 Risk = EC Cr * MP Cr(VI) * 100 * 0.012 (ug/m 3 ) - 1

Where

EC Cr i s the chronic exposure concentration for the mixture of all chromium compounds and

MP Cr(VI) is the mass percent of the inhaled mixture which is hexavalent chromium.



### 2.3 **Approach for D**  **eveloping S**  **peciation P**  **rofiles for S**  **elected S**  **ource C**  **ategories**
As discussed ab ove, the toxicity of chromium compounds is largely dependent on its oxidation

state ( i.e., C r( VI ) vs. Cr(III)
, primarily) which is an important factor in evaluating the health effects from exposure to chromium compounds. Where the specific compound or oxi dation state of chromium is

available , the appropriate dose response value may be applied for the purposes of risk assessment. However, for generically reported chromium emissions where there is no information provided regarding

the oxidation state of the chromium

, we generate default “speciation profiles” that reflect the proportions of emissions that would likely be in the Cr ( VI ) and Cr ( III ) oxidation states. Appendix A contains a paper by several EPA staff wherein available chromium speciation data for different industrial categories of emission sources have been analyzed to develop default chromium speciation profiles

. The following sections describe the data, analyses , limitations and conclusions regarding chromium speciation for the

two selected sou rce categories of coal

- fired and oil

- fired utility boilers

.



### 2.4 **Chromium Speciation for Specific Source Categories**

**2.4.1 Coal** 

**- Fired**  **Boilers** Based on source test data from 7 units, including 4 utility boilers and 3 industrial boilers (which are similar in process to utility boilers but often smaller), an average of 12 percent hexavalent chromium

was derived to be used as the speciation default for coal

- fired boilers without available chromium speciation information . The average hexavalent chromium for the 4 utility boilers was 11 percent and the range for the 4 tests was 0.4 percent to 23 percent

. 14

14 US EPA, 1998

. Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units

– Final Report to Congress. U.S. EPA #453 /R

- 98

- 004. Available at http://www.epa.gov/ttn/caaa/t3rc.html

. Although the range of values was not reported, t he average hexavalent chromium for the 3 industrial boilers was 12 percent

. (Emissions database compiled
November 30, 200 0, in support of National Emission Standards for Hazardous Air Pollutants for Industrial/Commercial/Institutional Boilers and process Heaters, Final Rule, 69FR55217 September 13,**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

5 2004)

. Because of the limited number of units tested, we chose the value of 12 percent (the highest percent average of hexavalent chromium when considering both utility and industrial boilers) to be used

as the default for our analysis of potential chromium risks from coal

- fired utility boilers

.

**2.4.2 Oil** 

**- Fired**  **B oilers**  Based on source test data from 7 units, an average of 18 percent hexavalent chromium was derived

to be used as the speciation default for oil

- fired boilers without available chromium speciation

information

. The average hexavalent chromium for the 7 utility boilers was 1 8 percent , and the range for

the 7 tests was 5 to 34 percent

. 15



### 2.5 **Uncertainties and L imitations** 
The uncertainties and limitations associated with this analysis are related primarily to the speciation profile data availability

, and the assumptions made to ge nerate the default speciation profiles.

A ssumptions were made in this analysis to: 1) select the compound species of chromium driving cancer

risks based on health effects information, and 2) select the appropriate percentage of the chromium species drivin g cancer risk for derivation of the inhalation cancer risk estimates for chromium emitting

facilities. This section briefly describes the assumptions made and associated uncertainties and
limitations, and a qualitative characterization of the relative con fidence (assigned as low, moderate or high) on those assumptions

. A major limitation of this analysis is t he small number of test data (i.e., speciation profile from 7 units) available to derive chromium default speciation profile values for both c oal

- a nd oil

- fired boilers

. Th ese data represent a very small portion of the units that exist within the respective source categories (approximately 1,200 combined coal

- and oil

- fired EGUs), which introduces uncertainties when making generalization s on how ac curately the default profiles derived in this analysis reflect actual speciation profiles for coal

- and oil

- fired boilers emissions

. With regards to selecting the appropriate percent chromium to derive default speciation profiles based on the available s peciation data, we chose to

calculate the percent average based on pooling similar test data from the available units for coal

- and oil

fired boilers. Although this seems a reasonable quantitative approach given the limited data set, an
alternative, and m ore conservative, approach would have been to use the maximum measured percentage

of hex avalent chromium rather than the average of the range. Further uncertainty exists as to the percent

hexavalent chromium given the wide range present in the test data for either coal

- or oil

- fired units.

15 US EPA, 1998 . Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units

– Final Report to Congress. U.S. EPA #453/R

- 98

- 004. Available at http://www.epa.gov/t tn/caaa/t3rc.html

.**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

6 Based on this information

, we have low confidence i n the results based on the overall selected assumptions. With regards to the cancer risk from chromium and chromium compounds, we selected h exavalent

chromium as the species likely to be driving cancer risks based on solid evidence from the health effects database for chromium and compounds. Major scientific bodies that conduct thorough reviews on carcinogenic compounds (e.g., IARC, NTP) agree that there is sufficient evidence for the c arcinogenicity of Cr(VI) compounds in humans based on the combined evidence from the epidemiological, animal and

mechanistic data available. These reports also state that compounds of chromium III are not classifiable

as to their carcin ogenicity . Based on this information, we have high confidence on the assumption that hexavalent chromium is the carcinogenic species a nd that the carcinogenic risk of chromium

- emitting facilities is proportional to the mass of hexavalent chromium containe d in the emissions from those

facilities

.



### 2.6 **Conclusions**
Based on the information above

, we have high confidence that hexavalent chromium is the species driving the carcinogenic risk of chromium

- emitting facilities and

, thus

, we consider it reasonable to der ive default speciation profiles based on the mass of hexavalent chromium contained in the emissions from

chromium

- emitting facilities. We have less confidence in the default speciation profiles derived based on

a limited data set with a wide range of perc ent ages of hexavalent chromium

. An alternative and more

conservative approach would be to use the maximum measured percentage of hex avalent chromium rather than the average of the range.**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

7 

### 3 **Nickel and**  **C ompounds** 

**3.1 Background** 

Nickel (Ni) is a lustrous white, hard, ferromagnetic metal found in transition group VIII of the

Periodic Table. It has high ductility, good thermal conductivity, high strength, and fair electrical conductivity. It constitutes approximately 0.009 percent of the earth's crust, making it the 24th most abundant element. Nickel can achieve several oxidation states including

- 1, O, +1, +2, +3, and +4 , and can be combined with many other elements to form different nickel compounds ; however, the majority of nickel compounds are nickel +2 speci es. Indirect sources, primari ly coal and oil combustion, are estimated to release from 85 to 94 percent of the total anthropogenic nickel emissions to the air. N ickel compounds are used for nickel alloys, electroplating, batteries, coins, industrial plumb ing, spark plugs, machinery parts, stainless

- steel, nickel

- chrome resistance wires, and as catalysts

. 16
Nickel and nickel compounds have been classified as human carcinogens. N ational and

international scientific bodies including the IARC ( 1990 ) 17 , the Worl d Health Organization (WHO,
1991) 18

, and the Europea n Union’s Scientific Committee o n Health and Environmental Risks (SCHER, 2006) 19

16 US EPA, 1986

. Health Assessment Document for Nickel. EPA/600/8

- 83/012F. National Center for E nvironmental Assessment, Office of Research and De velopment, Washington, DC. , agree that nickel compounds (including nickel sulfate), in general, are carcinogenic. In their 1 1 th Report of the C arcinogen s , the NTP has classified nickel compounds as known to be human carcinogens based on sufficient evidence of carcinogenicity from studies in humans, including epidemiological and mechanistic information, which indicates a causal relationship between exposur e to nickel compounds and human cancer. This classification is based on consistent findings of increased risk of cancer in exposed workers, and support by evidence from experimental animals that shows that exposure to an assortment of nickel compounds by m ultiple routes causes malignant tumors at various organ sites and in multiple species. The 11th Report of the Carcinogens states that the “ combined results of epidemiological studies, mechanistic studies, and carcinogenesis studies in rodents support the concept

17 International Agency for Research on Cancer ( IARC ) , 1990. IA RC monographs on the evaluation of carcinogenic risks to humans. Chromium, nickel and welding . Vol. 49. Lyons, France: International Agency for Research on Cancer, World Health Organization Vol. 49 : 256

. 18 International Labour Organization/United Nations E nvironment Programme, World Health Organization (WHO), 1991. Nickel. In Environmental Health Criteria No 108 Geneva

. 19 European Commission, Scientific Committee on Health and Environmental Risks (SCHER), 2006. Opinion on: Reports on Nickel, Human Health p art. SCHER, 11th plenary meeting of 04 May 2006 [http://ec.europa.eu/health/ph_risk/committees/04_scher/docs/scher_o_034.pdf]. CHER 2006**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

8 that nickel compounds generate nickel ions in target cells at sites critical for carcinogenesis, thus allowing consideration and evaluation of these compounds as a single group ”

. Although the precise nickel compound (or compounds) responsible for the carcinogenic effects in humans is not always clear, studies

indicate that nickel sulfate and the combinations of nickel sulfides and oxides encountered in the nickel refining industries cause cancer in humans. In agreement with the above mentioned sci entific bodies

, t he

US Department of Health and Human Services (DHHS , 1994 ) 20 has determined that nickel compounds are known human carcinogens , and that another nickel compound, nickel metal

, may reasonably be anticipated to be a carcinogen. The EPA has on ly evaluated two nickel compounds for their carcinogenic potential

-- nickel subsulfide and nickel refinery dusts

-- and has classified them both as group A, human carcinogens. Another assessment for the carcinogenic pote ntial of nickel and nickel compoun ds has been developed by the California Department of Health Services (CDHS, 1991) 21

The major scientific bodies mentioned above have recognized that the re are potential differences

in toxicity and/or carcinogenic potential across the different nickel compounds. These differences are
believed to be due

, in part

, to differences in solubility properties and /or different speciation of nickel compounds that i n turn make nickel ions more or less available at target sites. The view of the IARC’s nickel review group ( IARC’s Work ing grou p Special Report 2009 ) . With regards to speciation,

it is noted in this assessment that the available epidemiological data is inadequate to develop separate unit

risk factors for different nicke l compounds, nevertheless the view of CDHS is consistent with consideration of both insoluble and soluble nickel compounds as carcinogenic based on the available epidemiological evidence

.

22

20 US Department of Health and Human Services (DHHS), 1994. Seventh annual report on carcinogens: Summary 1994. Research Triangle Park, NC: National Institute of Environmental Health Sciences (NIEHS), 262

- 269. is that

, in addition to the release of nickel ions at target sites, there may be other less understood f actors that promote accumulation of nickel ions at critical target sites and

, given the available scientific evidence , it is difficult to predict the relative carcinogenic hazard of nickel co mpounds

. There ha ve been differences of opinions on the consider ation of all nickel compounds as carcinogenic to humans. Some authors believe that water soluble nickel, such
as nickel sulfate, should not be considered a human carcinogen

, based primarily on a negative nickel

sulfate NTP 2

- year rodent bioassay (which is different than the positive nickel subsulfide 2

- year NTP

21 California Department of Health Services (CDHS), 1991. Health Risk Assessment for Nickel. Initial Statement for Rulemaking, Proposed Identification of Nickel as a T oxic Air Contaminant

– Technical Support Document, part B. Available online at http://www.arb.ca.gov/toxics/id/summary/nickel_tech_b.pdf
22 International Agency for Research on Cancer (IARC) Working Group: Special Report. Policy; A review of human carcin ogens; Part C: metals, arsenic, dusts, and fibres. Lancet Oncol 2009, 10:453

- 454.**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

9 bioassay )

. 23
, 24
, 25 A lthough these authors agree that the epidemiological data clearly support s an
associ ation between nickel and increased cancer risk, they sustain that the data are weakest regarding

water soluble nickel

. A recent review by Grimsrud et al.

, ( 2010) 26

A s mentioned above

, the EPA has only derived URE values for nickel subsulfide and for nickel refinery dusts. N ickel subsulfide has a URE of 0.0004 8 per μ g/m 3 , which means that inhaling nickel

subsulfide in air at an average concentration of 1 μg/m 3 daily for a lifetime poses an estimated increased

risk of cancer of 480 in a million

. The nickel refinery dust has a value of 0.00024 μ g/m 3

, which suggests that this compound may have half of the carcinogenic potential of nickel subsulfide. The r e are two other

available UREs for nickel compounds derived by the CDHS (URE derived for nickel compounds as a group) and the Texas Com m ission on Environmental Quality ( TCEQ, Draft assessment, 2009) highlights the robustness and consistency of the epidemiological evidence across several decades showing associations between nickel and nickel compounds exposure (including nickel sulfat e) and cancer

.

27

, with

values of 0.00026 per μ g/m 3 and a range from 0.000 39

- 0.0009 μ g/m 3 ( this range corresponds to different adjustments in the modeling) , respectively.



### 3.2 **Approach for Estimating Inhalation Cancer Risks from Nickel Compounds** 
Based on past technical and scientific considerations, the determination of the percent o f nickel subsulfide (which has an IRIS URE value) versus nickel sulfate (with no available URE value) was
considered a major factor for estimating the extent and magnitude of the risks of cancer due to nickel

containing emissions. Thus, in previous analy s e s , we estimated cancer risks due to the inhalation of all nickel compounds based on the estimated exposure concentration of nickel subsulfide alone. Thus :

Risk = EC Ni subsulfide * 0.0004 8 (ug/m 3 ) - 1

Where

23 Oller A. Respiratory carcinogenicity assessment of soluble nickel compounds. Environ Health Perspect 2002
, 110:841

- 844.
24 Heller JG, Thornhill PG, Conard BR: New views on the hypothesis of respiratory cancer risk from soluble nickel exposure; and reconsideration of this risk's historical sources in nickel refineries. J Occup Med Toxicol 2009, 4:23.
25 Goodman JE, Prueitt RL, Thakali S, and Oller AR. The nickel iron bioavail ability model of the carcinogenic potential of nickel

- containing substances in the lung. Crit Rev Toxicol 2011, 41:142

- 174.
26 Grimsrud TK and Andersen A. Evidence of carcinogenicity in humans of water

- soluble nickel salts. J Occup Med Toxicol 2010, 5:1

- 7. Available online at http://www.ossup

- med.com/content/5/1/7.
27 Texas Commission on Environmental Quality (TCEQ), 2009. Development support document draft for arsenic/inorganic arsenic compounds, and nickel compounds . Available online at http://www.tceq. texas.gov/toxicology/dsd/reviews.html#arsenic**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

10 EC Ni subsulfide is the chronic exposure concen tration estimate for Ni subsulfide and 0.0 0048 (ug/m 3 ) - 1

is the cancer unit risk estimate for nickel subsulfid e

. In terms of chronic inhalation exposure to total

nickel compounds, we need to know the mass percentage of the total nickel mixture which is su bsulfide in

order to estimate chronic cancer risks. Thus:

Risk = EC Ni * MP Ni subsulfide * 100 * 0.00048 (ug/m 3 ) - 1

Where

EC Ni is the chronic exposure concentration for the mixture of all Ni compounds and MP Ni sunsulfide is the mass percent of the in haled mixture which is nickel subsulfide

.



### 3.3 **A pproach for**  **Developing Speciation Profiles for Selected Source Categories** 

Similar to chromium, the speciation data for nickel emissions from different source categories is

limited

. Several approaches have been c onsidered by the EPA, over time, in the determination of the

cancer risks posed by the inhalation of nickel and nickel compounds emitted by large combustion sources ( including oil

- combustion). The following sub sections describe the data, analyses and as sumptions regarding nickel speciation for risk analysis derived in the past ( A a nd B), and potential approaches (C)

based on recent nickel speciation data from oil

- fired power plants

.

**3.3.1 A.**  **Approach to**  **Derive Unit Risk Estimates: Electric Utility Report to**  **Congress 1998** A speciation analysis performed by the Electric Power Research Institute 28

28 US EPA, 1998. Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units

– Final Report to Congress. US EPA #453/R

- 98

- 004. Available at http://www.epa.gov/ttn/caaa/t3rc.html. using data from 1992

to 1994 on 5 sites with oil

- fired utilities showed the presence of numerous nickel compounds and a wide

range of the percentage s of different nicke l species measure d . This report indicated the following general speciation profile: soluble nic kel compounds 25 to 60 percent
, sulfidic nickel compounds 4 to 26 percent
, metallic nickel compounds 0 to 4 percent, and oxidic nickel compounds 27 to 70 percen t

. Based on th ese data, there were two proposed approaches to calculat ing nickel inhalation risk estimates from these

sources . The first approach used the assumption that t he mix of nickel compounds emitted by oil

- fired utilities was 50 percent as carcin ogenic as nickel subsulfide (the nickel compound with the higher cancer potency based on the existing UREs). The second approach was also based on the application of the IRIS

URE for nickel subsulfide ; however it provided a suite of risk estimates dependi ng on the percentage of

nickel subsulfide (ranging from 100 to 0 percent) believe d to be present in the emissions from oil

- fired**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

11 utilities. The assumption us ed for both approaches was that only the nickel subsulfide fraction

contribut es to the cancer ris k . T he cancer risk due to the other nickel compounds was considered as

unknown , and thus not considered as contributing to cancer

.

**3.3.2 B** 

**. Approach**  **to Derive Unit Risk E**  **stimates :**  **NATA 2000** Based on p revious analysis of some of the largest nickel

- emitt ing c ombustion sources indicating

that at least 35 percent of total nickel emissions may be soluble compounds 29

, the EPA assumed that as much as 65 percent of emitted nickel could be in the insoluble form and that all insoluble nickel could be crystalline. Beca use the URE listed in IRIS for nickel subsulfide represents a form which is pure insoluble crystalline nickel, this assessment assumed that 65 percent of the total mass of emitted nickel might be of this form, and thus might be carcinogenic. Thus, f or the purpose s of th e 2000 NATA

asse ssment, the EPA assumed that 65 percent of emitted nickel was insoluble, that all insoluble nickel

was crystalline, and that the IRIS URE for nickel subsulfide c ould be applied to this portion . On this
basis, the URE for nick el subsulfide (representing pure insoluble crystalline nickel) was multiplied by 0.65 and applied to the mass emissions of all nickel compounds

.

**3.3.3 C.**  **Approach to Derive Unit Risk Estimates:**  **Alternatives Based on**  **Speciation of**  **Residual Oil Fly Ashes from Power Plants** 

**.** R ecent ly, a nickel speciation analysis was conducted by the Electric Power Research Institute 30

29 US EPA, 2001. National

- Scale Air Toxics Assessment for 1996

- Appendix

- G: Health Effects Information Used in Cancer and Noncancer Risk Characterization for the NATA 1 996 National

- Scale Assessment, EPA

- 453/R

- 01

- 003. Available online at http://www.epa.gov/ ttn/atw/sab/appendix

- g.pdf. on residual oil fly ashes (ROFA) obtained from stacks of utility boilers from two of the largest oil

- fired power plants in the country

, which are l ocated in Hawaii (Honolulu and Waiau, respectively) . The ROFA samples were analyzed using x

- ray absorption fine structure (XAFS) spectroscopy and x

- ray diffraction (XRD)

. S peciation analysis results indicated that 80 to 95 percent of the total Ni pre sent in the ROFA samples was nickel sulfate hexahydrate (NiSO 4 .6H 2 O), and that approximately 20 percent of the total Ni

was present as a Ni

- containing spinel compound, similar in composition to nickel iron oxide ( NiFe 2 O 4 )

. Sulfidic Ni compounds (such as nicke l subsulfide) were not detected in this analysis

. Given that the ROFA samples tested did not contain nickel subs ulfide , using an approach to derive unit risks estimates

similar to that used in past analysis (e.g., applying the URE for nickel subsulfide to the mass emissions of all nickel compound) would result in a unit risk estimate equal t o zero. Based on what we know

30 See appendix B

. Report of Analysis on the “ Determination of nickel species in particulate matter collected on quartz thimble filters from flue gas emissions of power plants burning residual No. 6 fule oil”. Prepared by Fran k Huggins, University of Kentucky, Lexington, July 2011

.**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

12 regarding the health effects of nickel compounds as a group, making an assumption of no risk associated

with exposure to nickel

- containin g emissions would clearly not be health

- protective

. For this reason, we considered the following alternative approaches.

1

- Using the same approach as 2000 NATA. That is, using the IRIS URE for nickel subsulfide and applying a factor of 0.65 to the mass emi ssions of all nickel compounds. While it does not take the new speciation data into account, t his approach was developed for NATA and RTR assessments years ago, and has been peer reviewed by the Science Advisory Board (SAB ) , each time receiving favorable reviews

. It would also help to provide continuity and comparability between current and past assessments. This is the approach used in assessments performed in support of the EPA’s Toxics Rule proposed in April 2011.

2

- Considering a more health

- protective approach. Based on the consistent views of major scientific bodies (i.e., NTP in their 11 th ROC, IARC, and other international agencies) that consider nickel compounds to be carcinogenic as a group, we propose considering all nickel compounds as carcinog enic as nickel subsulfide. This approach would include the application of the IRIS URE without a factor, assuming 100 percent of nickel compounds as carcinogenic as nicke l subsulfide.

3

- Considering alternative UREs . This approach would involve the direct a pplication of URE

values developed for nickel compounds as a group by governmental agencies other than the

EPA ra ther than deriving a value based on the IRIS URE for nickel subsulfide

. The application of the CDHS URE would be yield a unit risk estimate ro ughly two fold lower than using 100 percent of the IRIS URE for nickel subsulfide . The application of the TCEQ URE

range would yield unit risk estimates that would range from about 20 percent lower than to
about two fold higher than th at based on using 100 percent of the IRIS URE for nickel

subsulfide

.



### 3.4 **Uncertainties and limitations** 
T he uncertainties and limitations associated with these analyse s are related primarily to the speciation profile data availability, and the assumptions made to generate the def ault speciation profiles. Assumptions were made in this analysis to: 1) select the compound species of nickel driving cancer risks based on health effects information, and 2) select the appropriate percentage of the nickel species driving

cancer risk for derivation of the inhalation cancer risk estimates for nickel

- emitting facilities. This section**Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds** 

**– EXTERNAL PEER REVIEW**  **REPORT**

**.**

13 briefly describes the assumptions made and associated uncertainties and limitations, and a qualitative characterization of the relative confidence (assigned as low, moderate or high) on those assumptions.
Similar to chromium, a major limitation of these analyse s is the small number of test data (i.e., 3 individual nickel speciation analysis of few units ) available to derive nickel default speciation profile

va lues for and oil

- fired units

. Another source of uncertainty is the lack of a speciation profile patter n s
across the different nickel speciation analysis available , and the wide range of percentages for the

individual nickel species

. Based on this inform ation, we have low confidence in the derivation default

nickel speciation profiles based on the available speciation data

. With regards to estimating the cancer risk from inhaling nickel and its compounds, we have in the
past selected nickel subsulfide as the species likely to b e driving cancer risks based on health effects

evidence indicating that nickel subsulfide is a carcinogen ic in both humans and animals, and on the potentially higher cancer potency of nickel subsulfide when compared to that of nickel refinery dusts ( which has the only other IRIS URE value )

. Although this approach was considered reasonable at the

time (i.e., , and consistent with approaches used for derivation of speciation defaults for other compounds (e.g., chromium), an alternativ e and more conservative approach would be based on consideration of all nickel compounds to be as carcinogenic as nickel subsulfide. It is important to note that the selection of an approach using the two discussed UREs (one from

California and one from Te xas) ra ther than an approach based on use of the IRIS URE for nickel

subsulfide would yield risk estimates roughly similar to those using the IRIS URE.Chromium Emissions Speciation for Selected Source Categories March, 20 11

1 TO: Ted Palma , HEID FROM: Chuck French and Anne Pope, SPPD

DATE: March 11 , 20 11

SUBJECT: Chromium Emissions Speciation for Selected Source Categories

I. Purpose

This document provides a summary of the available chromium speciation data for selected source categories addressed in 2005 NATA and the rationale for the chromium speciation values used in the preliminary inhalation risk analyses

.

II. Background

Chromium compounds occur in nature and are found primarily in the earth’s crust. The largest source of chromium is the ore mineral chromite, FeCr 2 O 4 or MgCr 2 O 4 , where magnesium can substitute for iron (Guertin, 2005). Chromium can also be found in small concentrations in certain types of igne o us rocks, coal, tar, asphalt, and crude oil (Guertin, 2005). Chromium exists in several different oxidation states , but the most stable and most commonly found are he xavalent chromium (+6 valence state) (or Cr VI) and trivalent chromium (+3 valence state) (Cr III) (ATSDR, 2008).

Chromium compounds are used in a variety of industrial applications and operations. They are used in alloys, such as stainless steel; paint pigments; refractory bricks that line furnaces and kilns; wood preservatives; production and processing of insolubl e salts; in leather tanning; as catalysts for halogenation, alkylation, and catalytic cracking of hydrocarbons; as fuel and propellant additives; and more (Guertin, 2005)

. Many of these applications use substances containing CrVI compounds

, including vario us chromates, dichromates, and c hromic acid

. In addition, some industrial processe s may produce chromium emissions, wherein the hexavalent state is favored in an oxidizing alkaline environment, and the trivalent state is favored in a reducing acidic envir onment (Guertin, 2005).

Cr VI, including its compounds, is classified by U.S. EPA as “a known human carcinogen by the inhalation route of exposure” because there is sufficient scientific evidence that inhalation exposure to this form of chromium increases the risks of cancer in humans (EPA, 1998). Because carcinogenicity by the oral route of exposure cannot be determined based on the information available, it is not classified as to the human carcinogenicity from this route of exposure (EPA, 1998) . Cr VI has an inhalation cancer potency value of 0.012 per microgram per cubic meter (μg/m 3 ), which means that inhaling Cr VI in air at an average concentration of 1 μg/m 3 daily for a lifetime poses an estimated increased risk of cancer of 12,000 in a million (E PA, 1998) . This inhalation cancer potency value is among the highest values of the hazardous air pollutants (HAP)Chromium Emissions Speciation for Selected Source Categories March, 20 11

2 listed in the Clean Air Act. On the other hand, trivalent chromium (Cr III) is “n ot classified as to its human carcinogenicity,” as no data are available on the carcinogenic potential of chromium (III) compounds alone (EPA, 1998) . Therefore, it has no cancer potency value for inhalation or ingestion exposures and is not evaluated for cancer effects in risk assessments.

For non

- carcinogenic effects, Cr VI has a Reference Concentration for Chronic Inhalation Exposure (RfC) inhalation value of 0.0001 per milligram per cubic meter (mg/m 3 ), which means that a person inhaling Cr VI in air at an average concentration of 0.0001 mg/m 3 or less daily is likely to be without an appreciable risk of deleterious effects during a lifetime (EPA, 1998). On the other hand, data are considered to be inadequate for development of an RfC for Cr III due to the lack of a relevant toxicity study addressing respirat ory effects of Cr III (EPA, 1998). Therefore, it has no non

cancer dose

- response value for inhalation and is not evaluated for non

- cancer effects in risk assessments. Thus, when estimating the increased risk of cancer due to chromium emissions, the deter mination of the percent Cr VI versus Cr III, is a major factor for estimating the extent and magnitude of the risks.

A preliminary risk assessment was conducted based on data extracted from EPA’s 2005 National

- Scale Air Toxics Assessment (NATA) National Emissions Inventory (NEI)

. While chromium emissions are sometimes reported in the NEI as the specific compound emitted (e.g., potassium dichromate, strontium chromate, etc.) they can also be reported to the NEI as a general categor y of emissions such as “chromium & compounds,” or “chr omium. ” As t he toxicity of these compounds is largely dependent on the oxidation state

, it is an important factor in evaluating the health effects from

ex posure to chromium compounds

. Where the specific compound or oxidatio n state of chromium is reported, the appropriate dose response value may be applied for the purposes of risk assessment. However, for generically reported chromium emissions, there is no information provided regarding the oxidation state of the chromium. For the source categories with generically reported chromium emissions, available data were examined to determine the proportions of emissions that would likely be in the Cr VI and Cr III oxidation states

. Preliminary “speciation profiles” were developed from this effort and applied in the preliminary risk analyses.

III. General Approach for Developing Speciation Profiles for Source C ategor ies

T he available chromium speciation data were examined for source categories

. The available ch romium speciation data ranged from no data available at all for a few source categories, to speciated data for individual emission point types for source categor ies

. For several source categories, speciation d ata were a vailable at a facility

- wide level for one or more facilities in the source category

. In general, the data were examined and evaluated , and the speciation profile determined to be most appropriate for each source category was chosen according to a hierarchy in the quality of the data. Where available, emission point

- specific speciationChromium Emissions Speciation for Selected Source Categories March, 20 11

3 data from that source category was given the highes t weighting. Next in the hierarchy

, overall emissions speciation data that represented the profile for an entire facility (as opposed to individual emission points at the facility) were considered. If data fo r a particular source category we re unavailab le or very limited

, then we reviewed available data and information about chromium emissions from other similar industrial source categories or similar processes. In some cases, we also considered the NEI default chromium speciation values for a source ca tegory or emission point type when source category data were not available or limited

. Since the available chromium speciation data are sparse for most source categories, a conservative approach was applied in determining an appropriate profile. For ex ample, if available data indicated a range of percentages for Cr VI, the higher end of the range was generally selected. Also, i n general, an overall maximum value (or upper end value) was selected to be applied source category

- wide to all emission points and at all facilities with generically reported chromium emissions.

While we believe the conservative approach applied in determining chromium speciation profiles to use for the preliminary risk analyses is appropriate, the chromium speciation profiles will be re

- evaluated considering data received from information collection requests (ICR) under CAA Section 114, public comments re ceived in response
to proposed rule

- making, and any relevant emissions test data that EPA may obtain from other efforts

. De pending upon the amount and quality of data available during this re

evaluation, a less conservative approach may be applied. In addition, where available, emission point type

- specific chromium speciation profiles may be applied. Any revised chromium spe ciation values will be applied in the risk analyses performed for the purposes of developing residual risk standards.

The following sections describe the data, analyses

, assumptions, and conclusions regard ing chromium speciation for selected source categor ies included in the 2005 NATA with generically reported chromium emissions

.

IV

. Chromium Speciation for Specific Source Categories

1. Coal Boilers

Chromium is naturally present as a trace element in coal. When coal is burned, chromium is released to the atmosphere. The quantity of chromium emitted is dependent on many factors including the concentration of chromium in the coal, control device efficiency and type of boiler . Based o n source test data from 7 units, an assumption of 12% hexavalent chromium is used for coal boilers in 2005 NATA modeling. The 7 units included 4 utility boilers and 3 industrial boilers. The average hexavalent chromium for the 4 utility boilers was 11 % and the range for the 4 tests was 0.4 % to 23%. ( 1998 EPA “Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units

– Final Report to Congress. U.S. EPA #453/R

- 98

- 004. February 1998). As part of the development of industrial boiler rule in 2000 , hexavalent chromium was measured at 3 industrial boiler units. The average hexavalent chromium for the 3 industrial boilersChromium Emissions Speciation for Selected Source Categories March, 20 11

4 was 12 % ( Emissions database compiled November 30, 2000
, in support of National Emission Standards for Hazardous Air Pollutants for Industrial/Commercial/Institutional Boilers and process Heaters, Final Rule, 69FR55217 September 13, 2004 ) Because of the limited number of units tested, the utility and indus trial boiler data sets were combined and the more conservative value of 12% was used as a default in the 2005 NATA.

2. Ferroalloys Production

Ferroalloys are alloys of iron and one or more other elements, such as chromium, manganese, and/or silicon. F erroalloy production occurs when an electric arc furnace (EAF) is charged with raw materials to begin smelting the ores. The molten product is “tapped” or poured from the furnace. Raw material and product handling (e.g., crushing and screening operations ) also occur as part of the ferroalloy production process. Emissions of chromium compounds may be caused by chromium present in the EAF feedstocks (coal and ore) and/or the refractory linings of the furnaces.

The ANPRM data set for the ferroalloys pro duction source category includes one facility with chromium emissions (out of a total o f three facilities), which are reported generically as “chromium & compounds ” and “chromium” emissions.

During the development of the MACT for ferroalloys, there was a ferrochromium (FeCr) plant (Macalloy) located at Charleston, South Carolina. This facility was a potential major source of HAP, but closed down before the MACT standard was promulgated. A letter addressed to Conrad Chin (Env ironmental Engineer, U.S. EPA) from the South Carolina Department of Health and Environmental Control (DHEC) dated December 19, 1996, contains a table that provides Cr VI emissions data from electric arc furnaces (EAF) no. 15 and no. 14 of the Macalloy fac ility (South Carolina DHEC, 1996). Based on these data , Cr VI comprises approximately 2 percent of the total chromium emissions from the EAFs.

We do not have speciated chromium emissions data for other Ferroalloys production processes (e.g., for ferro manganese or silicomanganese). However, we do have some data for EAFs used for steel production. We believe that steel production EAFs, particularly EAF melting processes, are somewhat similar to ferroalloy processes

, in that similar feedstocks are used and the EAF would include similar refractory linings

. Therefore, we also reviewed the chromium data for the melting process from steel production EAFs for possible application to the ferroalloy category. We have Cr VI data for the baghouse dust from EAF melting for one steelmaking facility. These data include 9 samples of EAF melting baghouse dust that ranged from 0.8 percent to 2.5 percent Cr VI; the average of these data was 1.5 percent ; and, the median was 1.4 percent (Consumers Energy, Laboratory Ser vices, 2004)

. These data, all from a single plant, are not from emissions stack test data but rather are from analyses of EAF baghouse dust (i.e., we assumed that captured baghouse dust concentrations are the same as the dust concentrations emitted from t he baghouse). We believe the EAF melting data from the baghouse dust is appropriate for ferroalloy production because the steel production EAF melting is similar to ferroalloys processing.Chromium Emissions Speciation for Selected Source Categories March, 20 11

5 Based on these data, and assuming that captured baghouse dust con centrations are the same as the dust concentrations emitted from the baghouse, the estimated Cr VI emissions from one closed ferroalloy facility were 2 percent of the total chromium emissions generated by the EAF, and emissions of Cr VI are a maximum of 2. 5 percent of EAF total chromium emissions at one steel production facility. Applying a conservative approach, we have assumed that 3 percent of the total chromium emissions from ferroalloys production facilities are Cr VI, and that 97 percent are Cr III, and this speciation profile was used in the preliminary risk analysis for generically reported chromium emissions

.

3

. Oil Boilers

Chromium is naturally present as a trace element in oil. When oil is burned, chromium is released to the atmosphere. The quantity of chromium emitted is dependent on many factors including the concentration of chromium in the oil, control device efficiency and type of boiler. Based on source test data from 7 units, an assumption of 1 8 % hexavalent chromium is used for coal boilers in 2005 NATA modeling. The average hexavalent chromium for the 7 utility boiler s was 18 %, and the range for the 7 tests was 5 % to 34%. ( 1998 EPA “Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units

– Final Report to Congress. U.S. EPA #453/R

98

- 004. February 1998).

4

. Pesticide Active Ingredient Production

Pesticide Active Ingredient (PAI) Production facilities manufacture active ingredients in insecticides, herbicides, fungicides, and r elated products. Typically, the active ingredients are subsequently formulated with inert ingredients to create end

product pesticides for application.

Emissions of chromium compounds are generally not expected from facili ties in this source category. However, chromium emissions are included in the ANPRM data set for one facility (out of a total of 18 facilities) , and are reported generically as “chromium & compounds” and “chromium” emissions

.

We have no data for the PAI facility reporting chromium emissions that would provide a chromium speciation profile or information to develop such a profile

. Consequently, we considered using chromium speciation data from source categories with similar processes. However, as chromium emissions appear to be unique to one PAI facility and are not necessarily emitted by a specific process used within this industry or other industries , a process

- type comparison between facilities or industries was not appropriate in this case

. We next considered the NEI d efault chromium speciation profiles. The NEI does not have a default chromium speciation profile specific to the MACT code for PAI production (0911), but there is a NEI default chromium speciation profile specific to the SCC for these emissions (30190013) of 4 percent Cr VI and 96Chromium Emissions Speciation for Selected Source Categories March, 20 11

6 percent Cr III

. Considering that all the chromium emissions for this source category are from one facility and one emissions point classified by this SCC, we applied the NEI default chromium speciation profile to these generical ly reported chromium emission s. Therefore the speciation profile used in the preliminary risk analysis wa s 4 percent Cr VI and 96 percent Cr III.

5

. Phosphoric Acid and Phosphate Fertilizer Production

Phosphoric acid production facilities produce phosphoric acid by reacting phosphate rock with sulfuric acid. Phosphate fertilizer production facilities react phosphoric acid or phosphate rock with other materials to create a fertilizer product. These ope rations are generally co

- located, as phosphoric acid manufacturing facilities provide feedstock for phosphate fertilizer production facilities, and much of the phosphoric acid produced in the U.S. is consumed in the manufacture of fertilizers

. Chromium em issions from these source categories originate from native chromium that is present in the phosphate rock ore.

The ANPRM data set for these facilities includes emissions for both source categories together

. Of the 15 facilities in the ANPRM data set fo r the phosph oric acid and phosphate fertilizer production source categor ies

, 2 facilities report “chromium” emissions.

We have no emissions data specific the facilities reporting these chromium emissions or to the phosphoric acid or phosphate fertilizer production industries that would provide a chromium speciation profile or information to develop such a profile for these processes. As such, w e considered using chromium speciation data from source categories with similar processes. Another facility type that produces inorganic chemicals and that also process es ore containing chromium compounds are chromium chemicals production facilities

. We have emissions tests from 199 6 and 2000 for two facilities that manufacture chromium chemi cals, which include chromium speciation measurements. The estimates of chromium speciation were 20 percent Cr VI and 8 0 percent Cr III for one facility and 2 1 percent Cr VI and 7 9 percent Cr III for the other facility (METCO 1996 and 2000) . We expect tha t ores used for chromium chemicals manufacturing would have much higher levels of total chromium than phosphate rock ores. However, the speciation of the chromium that is in the ores used by these industries and that is emitted through the ore processing and production of the inorganic chemicals could be similar.

In the absence of chromium speciation data specific to phosphoric acid and phosphate fertilizer production facilities, we applied a conservative approach and assumed that the proportion of Cr VI emissions from phosphate fertilizer and phosphoric acid production facilities is similar to the upper end of the proportion of Cr VI emissions from chromium chemical production facilities. As the proportion of Cr VI measured at two of these facilities was 20 percent and 21 percent , and considering the possible differences in the ores used in by the chromium chemical production facilities and the ores used by phosphoric acid and phosphate fertilizer production facilities, weChromium Emissions Speciation for Selected Source Categories March, 20 11

7 conservatively assumed a value of 25 percent of the total chromium emissions from phosphoric acid and phosphate fertilizer production facilities are Cr VI, and that 75 percent are Cr III

. This speciation profile was used in the preliminary risk analysis for generically reported chromiu m emissions for these source categories.

6

. Pulp and Paper Production

The pulp and paper production source category includes any facility engaged in the production of pulp and/or paper, including integrated mills (where pulp alone or pulp and paper or pa perboard are manufactured on

- site), non

- integrated mills (where paper or paperboard are manufactured, but no pulp is manufactured on

- site), and secondary fiber mills (where waste paper is used as the primary raw material). The pulp and paper production op erations (e.g., pulping, bleaching, and chemical recovery) are addressed in three MACT standards as follows:

• MACT I (40 CFR 63, subpart S)

- regulates hazardous air pollutant (HAP) emissions from the pulp production areas and bleaching operations at che mical pulp mills (Kraft, sulfite, semi

- chemical, and soda wood pulping processes)

• MACT II (40 CFR 63, subpart MM)

- regulates HAP emissions from the chemical recovery combustion areas of chemical pulp mills (kraft, sulfite, semi

chemical, and soda pulpin g processes)

• MACT III (40 CFR 63, subpart S)

- regulates HAP emissions from pulp and paper production areas of pulp mills using mechanical, secondary fiber, and non

wood pulping, and papermaking systems at all mills

Emissions of chromium and other metal lic HAP are not expected from MACT I and III sources (other than for supplemental or in

- process fuel use), but are expected from many of the MACT II chemical recovery combustion sources (e.g., direct contact evaporator (DCE) and nondirect contact evaporato r (NDCE) recovery furnaces) at kraft, soda, sulfite, and stand

- alone semichemical pulp mills; and lime kilns and smelt dissolving tanks at kraft and soda pulp mills.

Three ANPRM data sets were created for pulp and paper facilities. The contents of the data sets are based on the process MACT codes assigned to NEI records: (1) emissions regulated by MACT I and MACT III, (2) emissions regulated by MACT II, and (3) emissions from other pulp and paper sources at pulp and paper mills th at are not specifically identified as being regulated by MACTs I, II, or III or other MACTs. Of the 168 facilities in the MACT I and III pulp and paper ANPRM data set , six facilities report “chromium & compounds” emissions, six report emissions of “chrom ium,” and one reports emissions of Cr VI ; o f the 141 facilities in the MACT II pulp and paper ANPRM data set, 22 facilitie s report “chromium & compounds” emissions, 23 report emissions of “chromium,” 30 report emissions of Cr VI, 21 report emissions of Cr III, two report emissions of chromic acid (VI), one reports emissions of calcium chromate, one reports emissions of sodium chromate, and one reports emissions of sodium dichromate ; and of the 107 facilities in the “other sources” pulp and paper ANPRM data set, one facility reports “chromium & compounds” emissions, 3 report emissions of “chromium,” oneChromium Emissions Speciation for Selected Source Categories March, 20 11

8 reports emissions of Cr VI, and one reports emissions of Cr III. The generically reported “chromium” and “chromium & compounds” emissions comprise over 99 percent of all the reported chromium emissions in the MACT I and III data set; approximately 38 percent of all the reported chromium emissions from the MACT I I data set ; and over 99 percent of all the reported chromium emissions from the “other sources” da ta set

. Some data were available from the industry to characterize emissions from MACT II emissions sources at pulp and paper facilities. The National Council for Air and Stream Improvement (NCASI) has produced a technical bulletin, Technical Bulletin (T

B) 858 , that contains emissions factors and summaries of emission test results for total chrom ium and Cr VI for some MACT II emissions sources (NCASI, 2003). For emissions sources in which several total chromium and Cr VI emission test results w ere presented, we selected the median value for each, based upon assuming all non

- detects

were half of the detection limits, which is a common approach used to estimate emissions when samples are below detection limit. We then divided the Cr VI emission s by the total chromium emission s to determine the approximate percentage of Cr VI. In other instances, only total chromium emission s data were presented, and we could not determine chromium speciation from this information. For these emissions sources, the
g eneral NEI default chromium speciation was assigned (34 percent Cr VI and 66 percent Cr III). We have no emissions data specific to the MACT I and III or “other” sources at pulp and paper facilities that could be used to develop a chromium speciation pro file for the generically reported “chromium” or “chromium & compounds” emissions . However, the NEI has default chromium speciation profile s specific to many of the SCCs for these emissions sources , and we applied the se NEI default chromium speciation prof ile s to these emissions. Table 1 shows the chromium speciation applied to each type of emission point at pulp and paper facilities and the source of the speciation data. These speciation profiles were used in the preliminary risk analysis for generically reported chromium emissions.

Table 1 . Pulp and Paper Chromium Speciation

Pulp and Paper Process Units Emissions Source(s) SCC Estimated % Cr VI Basis MACT I and III

- Pulp and bleach systems at kraft, soda, sulfite, and semichemical pulping mills unknown operations, fuel use

– unknown fuel, and pulping not classified operations 30700X99 100 NEI default

fuel use

- unknown fuel 3079XXXX 34 General NEI default Fuel Fired Equipment: Natural Gas: Process Heaters, Fuel Fired Equipment: Natural Gas: Incinerators, In

- Process Fuel Use: Natural Gas, General 30790003 30790013 39000699 4 NEI default

wastewater 30700121 19 NEIChromium Emissions Speciation for Selected Source Categories March, 20 11

9 default causticizing 30700122 25 NEI default MACT II

- Chemical
recovery combustion sources at kraft

, soda, sulfite, and stand

- alone semichemical pulping mills smelt dissolving tank 30700105 100 NCASI unknown operations, neutral sulfite semichemical pulping, and pulping not classified 30700X99 100 NEI default recovery furnace/indirect
contact evaporator 30700110 75 NCASI

lime kiln (with ESP), MgO recovery system , NH3 recovery system, Na recovery system , and fluid bed reactor 30700106,3 0700221, 30700222, 30700223, 30700303 34 General NEI default

recovery furnace/direct contact evaporator 30700104 25 NCASI

incineration of sludge 50300506 19 NEI default

process heater

– oil, incinerator

– oil, lime kiln burning oil 30790001, 30790002, 30790011, 30790012, 39000403, 39000503 18 NEI default

lime kiln (with wet scrubber) 30700106 10 NCASI process heater

– natural gas, incinerator

- natural gas, incinerator

- process gas, lime kiln burning natural gas, in process fuel use

– natural gas 30790003, 30790013, 30790014, 39000603, 39000699 4 NEI default

unknown operations 39999999 100 NEI default Other, non

MACT processes incineration and incineration of sludge 50300107, 50300506 19

fuel use

– natural gas and in process fuel use

– natural gas 39000699 4

7

. Secondary Aluminum Production

Secondary aluminum production facilities recover aluminum from scrap materials such as beverage cans, foundry returns, dross, and other aluminum scrap. These facilities conduct the following operations: (1) preprocessing of scrap aluminum, including size reduction and removal of oils, coatings, and other contaminants, (2) furnace operations including melting, in

- furnace refining, fluxing, and tapping, (3) additional refining, by means of in

- line fluxing, and (4) cooling of dross.Chromium Emissions Speciation for Selected Source Categories March, 20 11

10 Emissions of chromium compounds may be caused by chromium present in the furnace feedstock ((i.e., the scrap aluminum) and/or the refractory linings of the furnaces

. Secondary aluminum feedstock may contain chromium from impurities in the scrap metal ( such as auto parts) and from contamination of oils, grease, paints and lubricants on the aluminum scrap being fed into the furnace. Additionally, refractory linings of various parts of the furnace and its appendages contain chromium compounds or chromium ore , which is emitted fr om the furnace along with the other metal HAP emissions.

Of the 180 facilities in the ANPRM data set for the secondary aluminum production source category, 70 facilities report “chromium” emissions, 9 report emissions of “ chromium & compounds,” 5 report emissions of Cr VI, and 2 report emissions of Cr III. The generically reported “chromium” and “chromium & compounds” emissions comprise over 99 percent of all the reported chromium emissions from the source category.

We have no emissions data specific to the secondary aluminum industry that could be used to develop a chromium speciation profile for the generically reported “chromium” or “chromium & compounds” emissions from secondary aluminum production processes. We have reports from tests conducted a t secondary aluminum facilities for which total chromium emissions were measured , but these tests did not

measure the Cr VI fraction of the total chromium emissions. Because the types of metal being recycled vary significantly from one facility to another , and because of lack of data for these facilities, it is not possible, at this time, to use industry

- specific data to estimate chromium speciation for the overall industry. We considered using chromium speciation data from facilities in source categories that have similar processes or equipment, such as wool fiberglass facilities. F acilities in both the wool fiberglass and the secondary aluminum source categories use furnaces that have linings made of refractory material containing chromium. Due to these refractory materials, melt furnaces have been identified as one of the primary sources of chromium emissions from wool fiberglass production. While chromium emissions for these furnaces may be similar for both source categories, there is uncertainty about the amount of Cr VI that is in the scrap aluminum feed, and this speciation could vary depending on the specific characteristics of the scrap material. Considering the Cr VI speciation profile for wool fiberglass melt furnaces ranges from 5 percent to 95 percent (see the wool fiberglass section for more information about this speciation range) , the uncertainty of the chromium speciation of the scrap feed material, and in applying a conservative approach, we have assumed that 100 percent of the total chromium emissions from secondary aluminum production facilities are Cr VI, and that 0 percent are Cr III. This speciation profile was used in the preliminary risk analysis for generically reported chromium emissions

.

8

. Secondary Lead Smelting

Seconda ry lead smelting facilities use blast, rotary, reverberatory, and/or electric furnaces to recover lead metal from lead

- bearing scrap materials, primarily lead

- acid batteries. Processes at these facilities include: (1) breaking lead acid batteries andChromium Emissions Speciation for Selected Source Categories March, 20 11

11 sep arating the lead

- bearing materials from the other materials, including the plastic case material and acid electrolyte, (2) melting lead metal and reducing lead compounds to lead metal in the smelting furnace, and (3) refining and alloying the lead to custo mer specifications. While it has been established that emissions of chromium from these facilities occur, the source of these emissions is not known.

The ANPRM data set for the secondary lead smelting source category includes 15 facilities with chromium emissions (out of a total of 15 facilities). The dataset includes records for “chromium” emissions for these facilities.

The data available on speciated chromium emissions from secondary lead smelters is limited to test data from one facility in Calif ornia (Exide). However, as operations at this facility are considered typical for the source category, chromium emissions are expected to be similar at other smelters. In October 1991 a nd February 1992 , Exide sampled baghouse dusts from multiple emissio ns points (EC/R, 2006) . In the four emissions source types examined at the facility

- a blast furnace, material storage unit, reverberatory furnace, and rotary dryer, total chromium and Cr VI w ere measured. The concentration of total chromium in the samp le d dust ranged from 20 to 120 mg/kg. The concentration of Cr VI was below the detection limit of 0.25 mg/kg in each of the samples . If we assume Cr VI is one

- half the detection limit (0.125 mg/kg), which is a common approach used to estimate emissions when samples are below detection limit, the range of the percent of Cr VI would be 0.1 percent (0.125 mg/kg ÷ 120 = 0.001) to 0.6 percent (0.125 mg/kg ÷ 20 mg/kg = 0.00625), depending on the amount of total chromium assumed (EC/R, 2006).

Based on these d ata, and assuming that captured baghouse dust concentrations are the same as the dust concentrations emitted from the baghouse, the estimated range of Cr VI emissions for secondary lead smelters are from 0.1 percent to 0.6 percent of the total chromium emi ssions generated. Applying a conservative approach, we have assumed that 1 percent of the total chromium emissions from secondary lead smelters are Cr VI, and that 99 percent are Cr III. Thi s speciation profile was used in the preliminary risk analysis f or generically reported chromium emissions

.

9

. Wood Furniture (Surface Coating)

The Wood Furniture Manufacturing industry encompasses the manufacture of a range of wood and wood

- based products, including kitchen cabinets, residential furniture, office furniture and fixtures, partitions, shelving, lockers, and other wood furniture. Th e MACT standard for this source category covers the f inishing, gluing, cleaning, and wash off operations at wood furniture manufacturing facilities. Emissions of chromium compounds from these facilities may be caused by the use of varnishes, glazes, paint s, and other coatings that contain chromium.

Of the 644 facilities in the ANPRM data set for the wood furniture surface coating source category, 48 facilities report “chromium & compounds” emissions, 13 report emissions of “ chromium,” and 10 report emiss ions of Cr III. The generically reportedChromium Emissions Speciation for Selected Source Categories March, 20 11

12 “chromium” and “chromium & compounds” emissions comprise approximately 22 percent of all the reported chromium emissions from the source category.

To determine whether there could be Cr VI emissions from these fac ilities, EPA contacted representatives from the industry trade association (American Furniture Manufacturers Association) and two of the primary coating suppliers ( Kazoo Nobel and Valspar). Based on these oral communications, we conclude that no p roduct f ormulations for coatings used in the wood furniture industry contain Cr VI compounds. Therefore, we have assumed that 0 percent of the total chromium emissions from wood furniture manufacturing (surface coating) facilities are Cr VI, and that 100 percent are Cr III. This speciation profile was used in the preliminary risk analysis for generically reported chromium emissions

.

10

. Wool Fiberglass Production

Wool fiberglass is manufactured in a process that forms thin fibers from molten glass using raw materials such as sand, feldspar, sodium sulfate, anhydrous borax, boric acid, or other materials. A typical wool fiberglass manufacturing line consists of the following processes: (1) preparation of molten glass; (2) formation of fibers into a wool fiberglass mat; (3) curing the binder

- coated fiberglass mat; (4) cooling the mat; and (5) backing, cutting, and packaging the finished product. According to the N orth American Insulation Manufacturers Association (NAIMA), Cr VI emissions are generated primarily from high temperature erosion and corrosion of refractory materials that contain chromium and some chromium is also generated from tramp chromium materials in the batch (Crane, 2008) . Melt furnaces and all riser/channel/conditioner/forehearth systems that are constructed from chromium

- bearing refractory materials emit Cr VI (Crane, 2008)

.

Of the 35 facilities in the ANPRM data set for the wool fiberglass production source category, 24 facilities report “chromium & compounds” emissions, 5 report emissions of “ chromium,” 3 report emissions of Cr VI, and 1 reports emissions of Cr III. The generically reported “chromium” and “chromium & compounds” emissions

c omprise over 95 percent of all the reported chromium emissions from the source category.

Information provided by NAIMA reports estimated percentages of Cr VI relative to total chromium emissions for the equipment that generates chromium emissions at wool fiberglass production facilities . This information is based on stack sampling conducted over the past several years and compiled by NAIMA (Crane, 2008). Table 2 summarizes this information.

Table 2 . Cr VI as a Percent of Total Chromium Emissions for C hromium Emissions Sources at Wool Fiberglass Production Facilities Chromium Emissions Source Type Cr VI Percent of Total Chromium Emissions Melt furnace

- OxyFuel unit with a precipitator 95%Chromium Emissions Speciation for Selected Source Categories March, 20 11

13 Melt furnace

- OxyFuel unit with electric

- boost and a precipitator 85%

Melt furnace

- electric (TECO, Intech, Western Fiberglass Hot Spot, etc.) 5%

Melt furnace

- hot top other than an OxyFuel unit 75% Channel/forehearth

- sealed, un

- vented electric 40% Channel/forehearth

- gas fired and vented 60% Channel/forehearth

- hybrid using burner and electric resistance heating 75%

Channel/forehearth

- cooled without added heating 30%

In addition to this data, information provided to EPA by the Kansas Department of Health and Environment , indicate s that one facility, Owens Corning in Kansas City, KS estimates Cr VI makes up 76 to 77 percent of total chromium emissions from melt furnaces and conditioning processes (Edmiston

- Bennett, 2008).

Based on these data, the estimated Cr VI emissions range from 5 percent to 95 percent of the total chromium emissions from melt furnaces and range from 30 percent to 75 percent of the total chromium emissions from channel/forehearths. As our data do not indicate the specific type of equipment used by facilities, and given the wide variation in the estimated chromium speciation, we have applied a conservative approach and assumed that 100 percent of the total chromium emissions from all emission points emitting chromium at wool fib erglass production facilities are Cr VI, and that 0 percent are Cr III. This speciation profile was used in the preliminary risk analysis for generically reported chromium emissions

.

D. Summary of Chromium Speciation Profiles for Selected 2005 NATA Categories

T he following table presents a summary of the estimated percent Cr VI and Cr III used in the 2005 NATA preliminary inhalation risk analyses for each source category , along with the data used to support these estimates

.

Table 3 . Summary of C hromium Emissions Speciation for Selected Source Categories in the 2005 NATA

Source Category % Cr VI % Cr III Basis for speciation Coal Boilers 12 88 Source test data Ferroalloys Production 3 97 Source category t est data, surrogate source category test data Pesticide Active Ingredient Production 4 96 NEI SCC default

Phosphate Fertilizer and Phosphoric Acid 25 75 S urrogate source category test dataChromium Emissions Speciation for Selected Source Categories March, 20 11

14 Source Category % Cr VI % Cr III Basis for speciation Production Pulp and Paper Production 4 to 100 depending on type of process unit 0 to 96 de pending

on type of process unit Industry d ata , NEI SCC defaults

Secondary Aluminum Production 100 0 S urrogate source category test data Secondary Lead Smelting 1 99 Source category t est d ata Wood Furniture (Surface Coating) 0 100 Discussion with trade association and

coatings suppliers Wool Fiberglass Production 100 0 Trade association

r eported estimates

E. References:

Agency for Toxic Substances and Disease Registry (ATSDR), 2008. Toxicological profile for Chromium (Draft for Public Comment) . Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service. Available
at: http://www.atsdr.cdc.gov/toxprofiles/tp7.html#bookmark08

. Consumers Energy, Laboratory Services , 2004. Analytical Test Results On Baghouse Dust

– at the Quanex Corporation Macsteel facility. February 27, 2004.

Crane, 2008. Email from Angus Crane (Vice President of General Council for NAIMA) to Mr. Jeff Telander (Environmental Engineer, U.S. EPA) which presents a summary of chromium emissi ons speciation data. February 8, 2008.

EC/R, 2006. Secondary Lead Smelter Industry

- Source Characterization for Residual Risk Assessment. Prepared for EPA/OAR/OAQPS/SPPD/MMG by EC/R Incorporated. November 2006.

Guertin, Jacques, James Alan Jacobs, Cynthia P. Avakian, 2005. Chromium (VI) Handbook . CRC Press. ISBN 9781566706087

.

Edmiston

- Bennett, 2008. Email from Robin Bennett

- Ed miston (ISB Environmental), to Andy Hawkins ( Kansas Department of Health and Environment). Subject: National Emissions Inventory Kansas City

– Chrome. January 16, 2008.

METCO Environmental, Dallas, T X, 1996. Source Emissions Survey of American Chrome & Chemicals, L.P., located in Corpus Christi, T X on August 14

- 16, 1996.

METCO Environmental, Dallas, T X, 2000. Source Emissions Survey of Elementis Chromium, located in Corpus Christi, T X on March 29 and 30, 2000.Chromium Emissions Speciation for Selected Source Categories March, 20 11

15 NCASI, 2003. Technical Bulletin 858, Compilation of Air Toxic and Total Hydrocarbon Emissions Data for Sources at Kraft, Sulfite, and Non

- Chemical Pulp Mills

– An Update. February 2003

. South Carolina, DHEC, 1996. Letter from the South Carolina Department of Health and Enviro nmental Control (DHEC) to Conrad Chin (of U.S. EPA). December 19, 1996.

U.S. EPA, 1998. Integrated Risk Information Service (IRIS) assessment for hexavalent chromium. Available at: http://www.epa.gov/ncea/iris/subst/0144.htm

. U.S. EPA, 1998. Study of Hazardous A ir P ollutant Emissions from E lectric Utility Steam Generating Units

– Final report to Congress

. EPA#453/R

- 98

- 004. February 1998. http://www.epa.gov/ttn/atw/combust/utilt ox/utoxpg.html

# Copyrighted page(s) removed. Copyrighted material is not available in Regulations.gov since it may not be reproduced without consent of the copyright holder.

Removed pages can be viewed at the USEPA Docket Center, Public Reading Room.

Address: 1301 Constitution Ave, NW Room 3334 Washington, DC 20004

Telephone: 202-566-1744

Email: docket-customerservice@epa.govPurpose of the Review of the Nickel and Chromium Methods Report and Charge to the External

Peer Reviewers.

Purpose The purpose of this review is to seek expert advice (written report that can be shared electronically) on the methods used to develop inhalation cancer risk estimates associated with emissions of chromium and nickel compounds from coal and oil

- fired electric utility steam generating units (EGUs) in support of EPA’s recently proposed Air Toxics Rule. 1 The der ivation of cancer risk estimates is based on the speciation data available from selected source categories, and on the available unit risk estimates (UREs) reflecting the dose that corresponds to a specific level of cancer risk.

Description of the docum ent to be reviewed

This 13

- page document includes a brief description of its purpose, followed by discussions of

emissions for both chromium (Section 2) and nickel (Section 3) compounds with regards to (1) the methods and rationale used in previous EPA ana lyses (where applicable), (2) the methods used in the recent analysis for the EPA’s Air Toxics Rule (considering previous methods and currently available data), and (3) a discussion of the uncertainties and/or limitations of the methods used. In this docu ment, we consider the emissions of chromium compounds from both coal

- and oil

- fired EGUs and the emissions of nickel compounds from oil

- fired EGUs, since these are major contributors to inhalation cancer risk estimates from each these source types.

In addi tion to these discussions, we have inclu ded attachments A and B which contain information on chromium speciation profiles for different industrial sources, and nickel species in particulate matter for power plants, respectively.

Charge questions

1

- Do EPA’ s judg ments related to speciated chromium emissions adequately take into account the available chromium speciation data? Chromium and Compounds

2

- Has the EPA selected the species of chromium (i.e., hexavalent chromium) that accurately represents the toxicity of chromium and compounds?

1 US EPA, 2011 . National Emission Standards for Hazardous Air Pollutants from Coal

- and Oil

- fired Electric U tility Steam Generating Units and Standards of Performance for Fossil

- Fuel

- Fired Electric Utility, Industrial

- commercial

- Institutional, and Small Industrial

- Commercial

- Institutional Steam Generating Units Rule. Available online at http://www.epa.gov/ttn/atw/utility/utilitypg.html

.3

- Are the assumptions used in past analysis scientifically defensible, and are there

alternatives that the EPA should consider for future analysis?

1

- Do EPA's judgments related to speciated nickel emissions adequately take into account available speciation data, including recent industry spectrometry studies? Nickel and Compounds

2

- Based on the speciation information available and on what we know about the health

effects of nickel and compounds, and taking into account the existing URE values (i.e.,

values derived for IRIS, Cal EPA and Texas), the EPA has provided several approaches to derive unit risk estimates that may be more scientifically defensible than those used in past analyse s . Which of the option s presented would result in more accurate and defensible characterization of risks from exposure to nickel and compounds ? A re there alternative approaches that the EPA should consider?

Timeline for Submittal of Review

The comments from the reviewers must be submitted to the EPA no later than July 29, 2011.David A. Eastmond

1 Responses to Charge Questions and Comments on the Draft “Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds” Document

Chromium and Compounds

1. Do EPA’s judgments related to speciated chromium emissions adequately tak e into
account the available chromium speciation data?

The data on chromium speciation has been derived from test data from 7 coal

- fired boilers and 7 oil

- fired boilers. As indicated in the document, this is a small sample size. Based on the citations li sted, the values used appear to date from before 1998 and do not appear to have included more recent studies that may be directly (or indirectly) relevant. Determining which articles are specifically relevant is difficult given the limited focus of the doc ument and the differences in terminology used in the articles. Some examples of more recent articles that would appear to be relevant are listed below. I will attach copies as available.

Huggins FE, Najih M, Huffman GP (1999) Direct speciation of chro mium in coal combustion by

- products by X

- ray absorption fine structure spectroscopy, Fuel 78:233

- 242.

Goodarzi F, Huggins FE. (2001) Monitoring the species of arsenic, chromium and nickel in milled coal, bottom ash and fly ash from a pulverized coal

- fir ed power plant in western Canada. J Environ Monit. 3(1):1

- 6.

Galbreath KC, Zygarlicke CJ (2004) Formation and chemical speciation of arsenic

- , chromium

- , and nickel

- bearing coal combustion PM 2.5 , Fuel Processing Technology 85:701

- 726.

Narukawa T, Riley K W, French DH, Chiba K. Speciation of chromium in Australian fly ash. Talanta (2007) 73(1):178

- 84.

Stam AF, Meij R, Te Winkel H, Eijk RJ, Huggins FE, Brem G. (2011) Chromium speciation in coal and biomass co

- combustion products. Environ Sci Technol. 45(6): 2450

- 6.

As appropriate, inclusion of the data in these articles could substantially increase sample size for determining chromium speciation in the document and may change the calculated value.

In addition, the Center for Air Toxic Metals has conducted a number of EPA funded studies that may also provide useful information. Some examples from the EPA website can be found at the following URLs:David A. Eastmond

2 http://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.abstractDetail/abstract/7 859/report/F

http://cfpub.epa.gov/nc er_abstracts/index.cfm/fuseaction/display.abstractDetail/abstract/1 809/report/0

2. Has the EPA selected the species of chromium (i.e., hexavalent chromium) that accurately represents the toxicity of chromium and compounds?

Yes. As indicated in the do cument, multiple authoritative bodies including the EPA, IARC and the National Toxicology Program have concluded that inhalation exposure to chromium VI compounds is carcinogenic to humans. The document is correct in stating that the EPA and IARC have con cluded that Cr III compounds are not classifiable as to their carcinogenicity to humans. However, this does not convey the full story as Cr III compounds are widely accepted as essential trace minerals and are commonly included in multiple vitamin supplem ents. Also, in a recent NTP 2

- year rodent bioassay report, positive results for the induction of cancer were not seen after dietary administration of high doses of chromium picolinate, a Cr III compound, to the treated mice and rats. I leave it to the EP A to decide whether this information should be included.

3. Are the assumptions used in past analysis scientifically defensible, and are there alternatives that the EPA should consider for future analysis?

I will discuss the current analysis since I a m not sure to which past analysis the question is referring. The current analysis is based on the assumption that the risk of cancer from inhalation exposure to chromium is due to the presence of Cr VI compounds and that this risk decreases linearly with dose into the low and very low dose range. Linear extrapolation is commonly used for agents that act through a mutagenic mode of action and Cr VI compounds are widely recognized as exerting their carcinogenic effects through a mutagenic mechanism (Straif et al., 2009; McCarroll et al., 2010). As a result, I would consider the use of linear extrapolation for estimating chromium risks to be scientifically defensible. As indicated in #2 above, I believe that there is strong scientific justification for basi ng the chromium risks on the dose of Cr VI rather than the total Cr dose.

In the current assessment, as a default assumption to calculate risks, Cr VI compounds are estimated to comprise 12% of the total Cr emitted from the coal

- and oil

- fired electric generating units (EGUs). This number is the higher of the averages from the coal

- and oil fired boilers. From the information presented in the document, this would seem to be a reasonable estimate, particularly for the calculation of population risks. I t should be noted that individual risks for exposed individuals could be higher, particularly if above average Cr VI percentages are consistently seen at specific EGUs.

Specific details on the sampling locations are not presented in the document but it appears that the speciation values were determined from samples collected at the EGUDavid A. Eastmond

3 itself and not at sites where exposure to the general population would occur. It is assumed that the proportion of Cr VI compounds to which general population is exposed will be that same as that at the collection site at the EGU. This seems to be a reasonable assumption but this may not be the case if significant atmospheric transformation of the Cr compounds occurs. There is some theoretical and laboratory

- based evide nce in the literature that Cr compounds can be transformed in the environment with a portion of the Cr VI compounds being converted into Cr III compounds (Seigneur and Constantinou, 1995; Werner et al., 2006).

Other assumptions that have been used are fairly typical and are based on an inhalation rate of 20 m 3 /day, a body weight of 70 kg, and a standard 70

- year lifespan. These default values are generally higher than average for the inhalation rate, and lower than average for the body weight and lifes pan. These do not reflect the ranges of values that are commonly seen. If desired, more accurate values could be obtained from the EPA Exposure Factors Handbook for this or future analyses.

Additional Comments

The risk estimate calculated from the uni t risk estimate is an upper

- bound estimate of the excess cancer risk resulting from a lifetime of continuous exposure to Cr VI at a concentration of 1 μg/m3 in air. It should be noted on page 3 that the 12,000 in a million risk is an upper

- bound estimate. Similar changes should be made elsewhere in the document such as the risk estimate for nickel described on page 9.

The formula for calculation of risk on page 4 appears to be incorrect. This can easily be seen if one assumes that mass percent of Cr V I in the mixture is 100% and compares the results to that of the formula on page 3. The MP Cr(VI) should be divided by 100 rather than multiplied by 100. Alternatively, the formula could be changed to EC Cr * Mass Fraction Cr(VI) * 0.012 (μg/m 3 ) - 1

. On pa ge 5 (beginning of 3 rd complete paragraph), the speciation data was derived from 14 units (7+7) rather than 7 as listed.

The 12 th Report on Carcinogens has recently been released by the NTP. The references to the 11 th Report on Carcinogens mentioned th roughout the document could be updated. Please note that the report title is incorrect on pages 3 and 7 and possibly elsewhere.

Nickel and Compounds

1. Do EPA’s judgments related to speciated nickel emissions adequately take into account available sp eciation data, including recent industry spectrometry studies?

Similar to what was described above for the chromium section, it appears that much of the nickel speciation information, with the exception of the recent 2011 Huggins study in Appendix B, come s from studies that were conducted prior to 1998. There are a number of more recent studies that may be directly or indirectly relevant. As indicated above,David A. Eastmond

4 determining which articles are directly relevant is difficult given the limited focus of the docu ment and the differences in terminology used in the articles. Some examples of more recent articles that would appear to be relevant are listed below.

Goodarzi F, Huggins FE. (2001) Monitoring the species of arsenic, chromium and nickel in milled coal, b ottom ash and fly ash from a pulverized coal

- fired power plant in western Canada. J Environ Monit. 3(1):1

- 6.

Galbreath KC, Zygarlicke CJ (2004) Formation and chemical speciation of arsenic

- , chromium

- , and nickel

- bearing coal combustion PM 2.5 , Fuel Proces sing Technology 85:701

- 726.
Goodarzi F, Huggins F. (2004) Speciation of nickel in Canadian subbituminous and bituminous feed coals, and their ash by

- products. J Environ Monit. 6(10):787

- 91.

Galbreath KC, Schulz RL, Toman DL, Nyberg CM, Huggins FE, Huffma n GP, Zillioux EJ. (2005) Nickel and sulfur speciation of residual oil fly ashes from two electric utility
steam

- generating units. J Air Waste Manag Assoc. 55(3):309

- 18.

Pattanaik S, Huggins FE, Huffman GP, Linak WP, Miller CA. (2007) XAFS studies of nick el and sulfur speciation in residual oil fly

- ash particulate matters (ROFA PM). Environ Sci Technol. 41(4):1104

- 10.

Huggins FE, Galbreath KC, Eylands KE, Van Loon LL, Olson JA, Zillioux EJ, Ward SG, Lynch PA, Chu P. (2011) Determination of nickel species in stack emissions from eight residual oil

- fired utility steam

- generating units. Environ Sci Technol. 45(14):6188

- 95.

In addition, the Center for Air Toxic Metals has conducted a number of EPA

- funded studies that may also provide useful information. Some examples from the EPA website can be found at the following URL:

http://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.abstra ctDetail/abstract/7 859/report/F

http://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.abstractDetail/abstract/1 809/report/0

It should be noted that the Huggins article listed above contains speciation information for nickel for EGUs in addition to the Hawaiian sites listed in Appendix B. From this and the other studies, it appears that the sulfidic nickel compounds are prese nt at quite low levels, if present at all, in the emissions from the EGUs.

2. Based on the speciation information available and on what we know about the health effects of nickel and compounds, and taking into account the existing URE values (i.e., val ues derived for IRIS, Cal EPA and Texas), the EPA has provided several approaches to derive unit risk estimates that may be more scientifically defensible than those used in past analyses. Which of the options presented would result inDavid A. Eastmond

5 more accurate and de fensible characterization of risks from exposure to nickel and compounds? Are there alternative approaches that the EPA should consider?

Most authoritative bodies, including the EPA, have concluded based on human, animal and mechanistic data that nickel c ompounds as a class, are carcinogenic to humans. The sulfidic nickel compounds appear to be the most potent but there is also evidence from human studies for the carcinogenicity of soluble nickel compounds, either alone or in combination with other nickel species. However, the results of animal studies have indicated that some specific nickel compounds such as nickel sulfate hexahydrate and nickel metal powder are not carcinogenic in rodents by inhalation whereas other nickel compounds showed clear eviden ce (nickel subsulfide) or limited evidence (nickel oxide) of carcinogenicity by the inhalation route.

Based on the recent studies such as those of Galbreath et al. (2005) and Huggins et al. (2011), it appears that very low levels of the most potent sulf idic nickel compounds are emitted from EGUs. As a result, neither option 1, the 2000 NATA approach, nor option 2, treating all nickel compounds as Ni subsulfide, would seem to be appropriate. From my perspective, Option 3 would be preferable, and of the alternative UREs, I would recommend using the TCEQ URE of 1.7 x 10 - 4 m 3 /μg. The risk assessment leading to the derivation of this number was performed recently, included an updated and critical review of the literature, and appears to be comprehensive wit h an emphasis on health

protection. One additional strength of the TCEQ evaluation is its inclusion of the Grimsrud et al., (2003) study where soluble nickel compounds, one of the major types found in the EGU emissions, were associated with elevated cance r incidence. It should also be noted that the TCEQ URE is quite similar to that derived by the CDHS (2.6 x 10 - 4

m 3 /μg) and the EPA for nickel refinery dust (2.4 x 10 - 4 m 3 /μg). The TCEQ, CDHS and EPA nickel refinery dust UREs could also be combined to der ive a composite URE.

Recently a nickel nuclear bioavailability model has been proposed to explain the biological effectiveness and potency of the various nickel compounds (Goodman et al., 2011). This mechanistically based model looks promising and coul d allow the URE to be adjusted (with appropriate health

- protective assumptions) by the relative bioavailability of the actual nickel compounds present or likely to be present in the EGU emissions. The paper describing the nickel nuclear bioavailability mo del was favorably reviewed by an expert panel prior to its publication (TERA, 2010).

Additional Comments

The DHHS (1994) reference mentioned on page 8 is an earlier version of the NTP Report on Carcinogens. The reference should be updated to use the more recent version and the text integrated with that on the previous page (page 7).

The Texas Commission on Environmental Quality’s final unit risk estimate is 1.7 x 10

- 4 μg/m 3 and not the range presented on page 9. The range presented appears to be the upper 95 th percentile unit risk estimates derived based on Texas rates (rather than the United States) for one of the two studies evaluated.David A. Eastmond

6 As explained above for the chromium risk formula, the formula for nickel on page 10 also appears to be inco rrect.

On page 12, the section on point 1

- the first sentence is an incomplete sentence and needs a verb.

The expert panel convened by TERA (2010) stated that “ While the mechanism of action for nickel carcinogenesis is not known and there are a numbe r of potential MOAs, the panel reached unanimous agreement that nickel does not act by direct DNA reactivity. Instead, the available data suggest that nickel

- induced tumors result from protein

- level effects.” If this conclusion represents the general cons ensus of those in the field, use of approaches other than linear extrapolation might be warranted in estimating low dose risks from nickel inhalation. It should also be noted that there were a number of panelists who did not believe that “ there is suffici ent evidence to prove that a threshold exists for nickel compound carcinogenesis.”

References

Grimsrud TK, Berge SR, Martinsen JI, Andersen A. (2003) Lung cancer incidence among Norwegian nickel

- refinery workers 1953

- 2000. J Environ Monit. 5(2):190

- 7.

McCarroll N, Keshava N, Chen J, Akerman G, Kligerman A, Rinde E. (2010) An evaluation of the mode of action framework for mutagenic carcinogens case study II: chromium (VI). Environ Mol Mutagen. 51(2):89

- 111.

Seigneur C and Constantinou E (1995) Chemica l kinetic mechanism for atmospheric chromium, Environ. Sci Technol. 29:222

- 231.

Straif K, Benbrahim

- Tallaa L, Baan R, Grosse Y, Secretan B, El Ghissassi F, Bouvard V, Guha N, Freeman C, Galichet L, Cogliano V; WHO International Agency for Research on Canc er Monograph Working Group. (2009) A review of human carcinogens

-- part C: metals, arsenic, dusts, and fibres. Lancet Oncol. 10(5):453

- 4.

TERA (2010) Report on the Nickel Bioavailability Workshop, Vol. 1, Workshop organized by Toxicology Excellence in Risk Assessment. The report is available online
at: http://www.tera.org/Peer/NiBioavailability/

Werner M, Nico P, Guo B, Kennedy I, Anastasio C (2006) Laboratory study of simulated atmospheric tran sformations of chromium in ultrafine combustion aerosol particles, Aerosol Science and Technology 40:545

- 556.Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds

Peer Review

by

Herman Gibb

Tetra Tech Sciences

2200 Arlington Boulevard, Suite 400

Arlington, VA 22201

Email: hgibb@sciences .com

July 26, 2011Herman Gibb

1 1. Do EPA’s judgments related to speciated chromium emissions adequately take into account the available chromium speciation data? Chromium and Compounds

Answer: Yes. EPA has focused on the species that are the most stable and for whic h the most information is available.

2. Has the EPA selected the species of chromium (i.e., hexavalent chromium) that accurately represents the toxicity of chromium and compounds? Answer: Yes. At this point in time, the data support a conclusion of a causal association between hexavalent chromium and lung cancer in humans; they do not support a conclusion of a carcinogenic risk for trivalent chromium or metallic chromium. The document states : “With regards to trivalent chromium Cr (III), the 1998 IRI S Toxicological Review notes that while the evidence from the occupational database ‘ could be used to suggest that total chromium is carcinogenic by inhalation, animal data support the human carcinogenicity data only on hexavalent chromium.” The animal da ta on the carcinogenic risk of inhaled trivalent chromium are limited. A stronger argument that hexavalent chromium is the species of concern would be Gibb et al. (2000) 1

. Gibb et al. (2000) found that in a study of 2357 chromate production workers, triv alent chromium exposure

, when adjusted for hexavalent chromium exposure

, was not associated with an increased risk of lung cancer.

3. Are the assumptions used in past analysis scientifically defensible, and are there alternatives that the EPA should consid er for future analysis? Answer: The study on which the IRIS 1998 quantitative risk assessment is based is the study by Mancuso (1975). Mancuso (1975) reported cancer risk by total chromium exposure. The ratio of trivalent to hexavalent chromium in th e Painesville facility studied by Mancuso was reported to range from 1:1 to 52:1. Exposure estimates were made from industrial hygiene data collected in 1949; the cohort studied began work in 1931

- 37. No information was available on the prevalence of sm oking in the workforce. EPA ’s quantitative assessment was based on the risk to total chromium , not hexavalent chromium. The risk was justified as a risk for hexav a lent chromium by the following assumptions: (1) that the ratio of trivalent to hexavalent chromium was 6 :1 which would underestimate the risk by seven

- fold ; and (2) that higher exposure in 1931

- 37 compared to 1949 when the industrial hygiene measurements were made and a greater prevalence of smoking among the cohort would overestimate

1 Gibb HJ, Lees PSJ, Pinsky P, Rooney BC. (2000). Lung cancer among workers in chromium chemical production. American Journal of Industrial Medicine 38:115

- 126. the risk by no more than four

- fold. Gibb et al. (2000) was undertaken to address the limitationsHerman Gibb

2 presented by these assumptions. Gibb et al. was a study of a chromate production facility in Baltimore. A comparison of the advantages of Gibb et al. (2000) vs Mancu so (1975) for risk assessment can be found in the following table:



### Gibb et al. (2000) Mancuso (1975, 1997 update )

Cohort 1205 white males 848 nonwhite males 304 race unknown 332 white males

Industrial hygiene measurements vis

- à

- vis work history Concu rrent with the work history Not concurrent with work history (Measurements made in 1949 were used to estimate exposure to workers who began employment in 1931

- 37) Industrial hygiene measurements vis

- à

- vis chromium species measurement Ambient measurements of Cr +6 (Cr +3 derived from ratios of Cr +6 to Cr +3 in settled dust) Ambient measurements of total Cr (Cr +6 and Cr +3

Number of lung cancer cases estimates from settled dust)

122 42 (1975 study); 66 (1997 update)

Person

- years of observation 70,736 5,853 (19 75 study); 12,881 (1997 update) Smoking data Yes/No for 91% of the cohort at time of employment None Exposure groups (mg/m 3

- years) 0

- 0.00149, 0.0015

– 0.0089, 0.009

– 0.0769, 0.077

– 5.25 < 0.25, 0.25

- 0.49, 0.50

– 1.00, 1.00

– 1.99, > 2.00 Analysis of cancer risk of Cr VI and Cr III Multivariate Univariate

As indicated in the table, the exposure groups in Gibb et al. are closer

, by at least two orders of magnitude

, to environmental Cr +6 concentrations than are the exposure groups of Mancuso (1975). The Gibb et al. study also had more person years of observation (70,736 vs. 5,853 ) , a larger cohort (2357 vs. 332) , and more lung cancer deaths (122 vs. 42 ) than the Mancuso study. Exposure measurements in the Gibb et al. study were taken at the time of exposure ; exposure in the Mancuso study was estimated from industrial hygiene measurements taken over 10 years after the cohort was first exposed. The Gibb et al. study had data on smoking prevalence; the Mancuso study had none. Exposure concentrations of hexavalent chromium in the Gibb et al. study were the result of actual measurements; hexavalent chromium exposure in the Mancuso study was estimated from total chromium measurements.Herman Gibb

3 Gibb et al., which was funded by EPA, is the basis of the OSHA Permi ssible Exposure Limit . It also is the basis of the quantitative risk assessment by Park et al. (2004) 2 that is used by NIOSH for its Recommended Exposure Limit fo r hexavalent chromium 3 . Park et al. (2004) is also the b asis of the cancer risk estimate in the World Health Organization’s draft Concise International Chemical Assessment Document (CICAD) on Hexavalent Chromium. The draft CICAD for hexavalent chromium states that the environmental cancer risk (as opposed to the occupational cancer risk estimate ) for hexavalent chromium is 0.04 per μg/m 3 (i.e., > 3X the current EPA risk estimate of 0.012 per μg/m 3

.

1. Do EPA’s judgments related to speciated nickel emissions adequately take into account available speciation data, including re cent industry spectrometry studies? Nickel and Compounds

Answer: All nickel compounds should be regarded as carcinogenic. The 12 th Report on carcinogens (2011) 4 , reports that “ nickel compounds ” (no distinction as to solubility) are known human carcinogen s . IARC (1990) 5 conc luded that there was sufficient evidence in humans for the carcinogenicity of nickel sulfate and of the combinations of nickel sulfide and oxides in the nickel refining industry. IARC’s overall conclusion was that nickel compounds (no distinction with res pect to solubility) are carcinogenic to humans. The International Committee on Nickel Carcinogenesis in Man (ICNCM) concluded that there was “strong evidence” that soluble nickel was associated with an increased risk of respiratory cancer (ICNCM 1990) 6

. The report further concluded that the epidemiologic studies provided evidence of a nasal cancer risk due to soluble nickel and that soluble nickel exposure may enhance the risk of lung and nasal cancer associated with less soluble forms of nickel. The C ommittee ’s work was funded and supported by the U.S. EPA; the Commission of European Communities; Energy, Mines and Resources Canada; National Health and Welfare Canada; Ontario Ministry of Labor; and the Nickel Producers Environmental Resea rch Association

.
It should be noted that the carcinogenicity of hexavalent chromium was also thought to be related to solubility and that soluble chromium compounds were not believed to be

2 Park RM, Bena JF, Stayner LT, Smith RJ, Gibb HJ, Lees PSJ. (2004) Hexavalent chromium and lung cancer in the chromate industry: a quantitative risk assessment. Risk Analysis 24(5): 1099

- 1108.
3 NIOS H. 2008. Draft Criteria Document Update on Occupational Exposure to Hexavalent Chromium. Available at: http://www.cdc.go v/niosh/review/peer/HISA/pdfs/DRAFTCriteriaDocumentUpdateOccupationalExposuretoHexava lentChromium.pdf
4 National Toxicology Program. 2011. Report on Carcinogens, 12 th Edition. Available at: http://ntp.niehs.nih.gov/index.cfm?objectid=03C9AF75

- E1BF

- FF40

- DBA9EC0928DF8B15
5 IARC. 1990. Chromium, Nickel and Welding. Volume 49. Available at: http://monographs.iarc.fr/ENG/Monographs/vol49/mono49

- 7.pdf
6 International Committee on Nickel Carcinogenesis in Man. Report of the International Committee on Nickel Carciongenesis in Man [Chair: Sir Richard Doll]. Scand J Work Environ Health 16(Speci al):1

- 82.Herman Gibb

4 carcinogenic 7

. Subsequent epidemiologic studies disproved that notion, howeve r, as strong evidence of respiratory cancer risk was found in workers exposed to sodium dichromate (chromate production) and chromic acid (chrome plating), both very soluble hexavalent chromium compounds 3

.
There is some question whether metallic nickel is carcinogenic. IARC (1990) 5 indicated that metallic is possibly carcinogenic. The 12 th Report on Carcinogens 4 indicates that metallic nickel is reasonably anticipated to be a carcinogen. Considering that metallic nickel is reasonably anticipated to be a carcinogen, it would be appropriate to consider nickel and nickel compounds as carcinogenic.

2. Based on the speciation information available and on what we know about the health effects of nickel and compounds, and taking into account the existing URE values (i.e., values derived for IRIS, Cal EPA and Texas), the EPA has provided several approaches to drive unit risk estimates that may be more scientifically defensib l e than those used in past analyses. Which of the options presented would result in mor e accurate and defensible characterization of risks f ro m exposure t o nickel and co m p o unds? Are there alternative approaches that the EPA should consider? Answer: Use the TCEQ URE of 2.64 - 4 per μ g/m 3 ( smoking adjusted Relative Risk Estimate with a U.S. ba ckground rate ) 8

. This approach : (1) uses human data for the risk estimate, (2) takes advantage of a nickel

- exposed cohort (Grimsrud 2003 9 ) for which there are data on the prevalence of smoking. None of the other epidemiologic studies used for quantitati ve risk estimates by TCEQ, CDHS, or EPA had data on smoking prevalence. Furthermore, t he study has a large cohort (N = 5,297), person

- years of observation (15 3,952.9)
, and lung cancer

cases (147)

.

SUMMARY OF RECOMMENDATIONS

1. Use Gibb et al. (2000) to justify selecting hexavalent chromium compounds (vs. trivalent chromium compounds) as the carcinogenic species of chromium

. 2. Use a risk estimate based on Gibb et al. (2000) for hexavalent chromium . One can use the risk estimate from Park et al. (2004) adj usted for environmental exposures (24 hours/day;

7 Levy LS, Martin PA, Bidstrup PL. 1986. Investigation of the potential carcinogenicity of a range of chromium containing materials on rat lung. British Journal of Industrial Medicine 43(4): 243

- 256.
8 Texas Commission on Environmental Qua lity (TCEQ), 2009. Development support document draft for arsenic/inorganic arsenic compounds, and nickel compounds. Available online at http://www.tceq.texas.gov/toxicology/dsd /reviews.html#arsenic
9 Grimsrud TK, Berge SR. Martinsen JI, Andersen A. 2003. Lung cancer incidence among Norwegian nickel

refinery workers 1953

- 2000. J Environ Monit 5(2):190

- 7.Herman Gibb

5 365 days/year; lifetime exposure) or the cancer risk estimate in the WHO CICAD on hexavalent chromium. Both are derived from Gibb et al. (2000). 3. Regard all nickel species as carcinogenic. 4. Use the TCEQ smo king

- adjusted risk estimate from the Grimsrud (2003) study with U.S. background data as the cancer risk estimate for nickel (2.64 - 4 per μg/m 3 )

.Michael Waalkes

This is a review of the methods used to develop cancer risk estimates associated with emissions of chromium and nickel compounds from coal and oil

- fired electric utility steam generated units (EGU). Specifically the reviewer was charged with several questions mostl y with regard to use of speciation data. The charge questions and comments (in bold ) are as follows:

Chromium and compounds:

General comments:

Specific compounds of chromium are not discussed at all in the document. Species of chromium are discussed. This amounts to an implied assumption that the chromium will exist in an ionic form in the emission, which may or may not be the case. The ionic hexavalent form would be presumed to be the most carcinogenic but is there clear evidence that this is the sp ecies that is in emissions? The data are sparse. This is also in sharp contrast to the Nickel section where specific compounds are considered.

More testing of speciation is required for truly accurate cancer risk estimates. Only very few data were avai lable and these varied greatly ( e.g. 0.4% to 23% for utility boilers) for hexavalent chromium.

The speciation my change with fuel source. Default emissions profiles may change as industrial practices change.

Charges Questions: 1) Do EPA’s judgments r elated to speciated chromium emissions adequately take into account the available chromium speciation data.

Yes but these are very sparse and limit the confidence in the resulting estimates.

2) Has the EPA selected the species of chromium (i.e. hexavalen t chromium) that accurately represents the toxicity of chromium and chromium compounds?

Hexavalent chromium ion is likely the carcinogenic species and to the extent this “represents the toxicity” of chromium and chromium compounds this is true for cancer but perhaps not all toxicity nor is it true for all chromium compounds (see general comments). The draft does not address specific compounds or if all compound would be degraded to ionic form. I n addition the term “chromium” could be interpreted as chromium metal.

3) Are the assumptions used in past analysis scientifically defensible, and are there alternatives that the EPA should consider for future?

The EPA recognizes the small number of spec iation data sets as a major limitation. This needs to be corrected in the future with advanced and consistent methods that look at extensive factors that could influence levels. With a data set this small, and the ranges as large as they are , it is questi onable if using the single maximum level is defensible. ThenMichael Waalkes

t here is no concept of variability, a key factor in defense of this approach , and this is largely done blind

. Basing any major decisions on data that vary over 57

- fold is a poor choice but there seems to be no alternative. Additional speciation and compound data is a critical need.

Nickel and nickel compounds:

General comments:

The 12 ROC is now available and should be cited. Not considering soluble nickel carcinogenic is contrary to the views of major Scientific bodies and this reviewer and should not be an option. More independent testing of emissions would enhance confidence. The draft talks about selecting appropriate nickel “species” when it is actually trying to select appropriate compoun ds

- it is assumed that all the compounds are +2 (page 12 two line up from bottom).

1) Do EPA judgments ...including recent industry spectrometry studies?

Yes.

2) Based on ..?

Option 2 based on clear evidence of the carcinogenic effects of soluble ni ckel compounds in humans. Alternative approaches would require a great deal of additional testing for carcinogenic potency and would be very costly and time consuming.1 Summary of the Peer Review of the Technical Support Document Titled: Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Nickel Compounds

. Three independent external peer reviewers 1
, 2
, 3 were asked to participate in the review of the methods for developing inhalation cancer risk estimates associated with emissions of chromium and nickel compounds from coal

- and oil

- fired electric utility steam generating units (EGUs) estimates in
support of EPA’s recently proposed Mercury Air Toxics Rule. 4 The approaches and rationale for the

technical and scientific considerations used to derive inhalation cancer risks were summarized in the

document titled Methods to Develop Inhalation Cancer Risk Estim ates for Chromium and Nickel Compounds

. A series of charge questions were posed to the peer reviewers in order to determine the technical and scientific relevance of the approaches used to develop the inhalation unit risk estimates

which are based on the speciation data available from selected source categories, and on the available unit risk estimates (UREs) reflecting the dose that corresponds to a specific level of cancer risk. This document presents the individual charge questions (chromium and compou nds presented first, followed by nickel compounds), a brief summary of the peer reviewers’ comments and recommendations, and how those recommendations can be addressed by the EPA in future risk characterizations.

1

-

a. Do EPA’s judgments related to speciated chromium emissions adequately take into account the available chromium speciation data? Two of the reviewers were in agreement with the EPA in that

, although the chromium speciation data available

ar e limited, the E PA had both considered appropriately the available data and highlighted the high level of uncertainty associated with these data. The third author also agreed that the chromium speciation database is limited and recommended

several additional studies for EPA’s consideration. The EPA reviewed these studies

and added relevant information from studies of coal

- combustion speciation indicating the percentage of hexavalent chromium ranging from below detection limits to levels two fold higher than those reporte d in past speciation analyses. Thus, the more Chromium and Compounds

1 Dr. Michael Waalkes

, National Toxicology Program, National Institute of Environmental Health Sciences

- National Institutes of Health, Research Triangle Park, North Carolina.

2 Dr. Herman Gibbs, Sciences International Inc., Alexandria, Virginia.

3 Dr. David Eastmond, Department of Cell Biology and Neuroscience, University of California, Riverside

. 4 US EPA, 2011

. National Emission Standards for Hazardous Air Pollutants from Coal

- and Oil

- fired Electric Utility Steam Generating Units and Standards of Performance for Fossil

- Fuel

- Fired Electric Utility, Industrial

- commercial

- Institutional, and Small Industrial

- Comme rcial

- Institutional Steam Generating Units Rule. Available online at http://www.epa.gov/ttn/atw/utility/utilitypg.html

.2 recent speciation data available is unlikely to reduce the uncertainty of the chromium speciation analyses used by EPA as the bases for risk characterization analysis.

b. Has the EPA selected the species of chro mium (i.e., hexavalent chromium) that accurately represents the toxicity of chromium and compounds? All three authors were in agreement that hexavalent chromium was the best scientifically supported carcinogenic species that represents the toxicity of chr omium and compounds.

c. Are the assumptions used in past analysis scientifically defensible, and are there alternatives that the EPA should consider for future analysis? Two reviewers considered the assumptions applied (primarily, the assumption that hexaval ent
chromium constitutes 12 % of the total coal

- fired utilities, and 18% of oil

- fired utilities, based on the speciation data available) to be reasonable given the limited data available for chromium speciation profiling. Given the limited chromium specia tion data available, and the view of the majority of the peer reviewers, the EPA considers it reasonable to use the same approach in future risk analyses. The third reviewer did not comment on the speciation assumptions used in past analysis.

2

-

a. Do EPA's judgments related to speciated nickel emissions adequately take into account available speciation data, including recent industry spectrometry

studies? T he reviewers, which are in agreement with the views of the EPA , consider all nickel compounds as carcinogenic, and thus did not focus on nickel speciation or nickel solubility as strong determinants of carcinogenicity

. These views are based in agreement of major scientific bodies (i.e., NTP, IARC, WHO ) in that the integrated

e vidence from epidemiological studies, mechanistic studies and carcinogenesis studies in rodents support the concept that nickel compounds should be considered carcinogenic, as a group. Further, with exception of IRIS (which has only derived

unit risk esti mates for nickel subsulfide and nickel refinery dusts) Nickel and C ompounds

5

5 IRIS derived URE values for 2 nickel compounds, nickel subsulfide (0. 00048 per μg/m 3 ) and nickel refinery dust (0.00024 μg/m 3 ). The other available UREs that have both been derived for nickel compounds, as a group, are the one developed by the California Department of Health Services (CDHS, 1991) and another by the Texas C ommission on Environmental Quality (TCEQ, Development Support Document, 2011) , with values of 0.00026 per μg/m 3 and 0.00017 μg/m 3 , respectively. , the other two unit

risk estimates derived by California Department of Health Services (CDHS, 1991)3 and the Texas Commission on Environmental Quality (TCEQ, Development Support Document, 2011) 6

b. Based on the speciation information available and on what we know about the health effects of nickel and compounds, and taking into account the existing

U RE values (i.e., values derived for IRIS, Cal EPA and Texas), the EPA has provided several approaches have b een derived for nickel compounds as a group. One

reviewer recommended that the EPA review several manuscripts that might (directly or indirectly) be relevant to nickel speciation profiling. However, as mentioned

above

, EPA, in agreement with the peer reviewers, considers nickel compound s to be carcinogenic as a group.

7

Two of the reviewers suggested the consideration of all nickel compounds as carcinogenic, which would lead to using the URE selected without application of a factor. The third reviewer pointed at only considering nickel subsulfide as the most potent carci nogen among nickel compounds (which was an approach used by the EPA in past analyses) with the application of a factor that would account for the fraction of nickel subsulfide from total nickel emissions. EPA disagrees with the latter reviewer

based on th e information discussed above (i.e., the available scientific evidence supports considering all nickel compounds as carcinogenic). The other aspect of this charge question was related to whether the EPA should consider an alternative approach. Two of the reviewers suggested using the URE derived by TCEQ rather than the one derived by Integrated Risk Information System (IRIS). The third author did not comment on alternative approaches. The EPA has decided to continue using

the current IRIS URE because IRI S derived values are at the top of our hierarchy with respect to dose response information used in EPA’s risk characterization

. to derive unit risk estimates that may be more scientifically defensible than those used in past analyses. Which of the options presented would result i n more accurate and defensible characterization of risks from exposure to nickel and compounds? Are there alternative approach es that

the EPA should consider?

8

6 Texas Commission on En vironmental Quality (TCEQ), 2011 . Development Support D ocument for nickel and inorgan ic nickel compounds . Available online at http://www.tceq.state.tx.us/assets/public/implementation/tox/dsd/final/june11/nickel_&_compounds.pdf
7 See section 3.3 of the document titled “ Methods to Develop Inhalation Cancer Risk Estimates for Chromium and Ni ckel Compounds ”

. Available online at http://cfpub.epa.gov/si/si_public_record_Report.cfm?dirEntryId=238881

. 8 H ealth Effects Information Used i n Cancer and Noncancer Risk Characterization4 Nevertheless, taking into account that there may be differences in toxicity and/or carcinogenic potential across the different nickel compounds, and given that there have been two URE values derived for exposure to mixtures of nickel compounds that are

two to three fold lower than the IRIS URE for nickel su bsulfide, the EPA also considers it reasonable to use a value that is 50 percent of the IRIS URE for nickel subsulfide for providing an estimate of the lower end of a plausible range of cancer potency values for different mixtures of nickel compounds.

f or the 1999 National

- Scale Assessment. Available online at http://www.epa.gov/ttn/atw/nata1999/99pdfs/healtheffectsinfo.pdf

.