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United States Office of Chemical 

Environmental Protection Safety and Pollution 

Agency Prevention 

TSCA Workplan Chemical Risk Assessment

Antimony Trioxide 

CASRN: 1309-64-4 

December 2012

NOTICE

This document is an External Review Draft. This information is distributed solely for the 

purpose of pre-dissemination peer review under applicable information quality guidelines. It 

has not been formally disseminated by EPA. It does not represent and should not be construed 

to represent any Agency determination or policy. It is being circulated for review of its 

technical accuracy and science policy implications.
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Table of Contents

AUTHORS / CONTRIBUTORS / ACKNOWLEDGEMENTS / REVIEWERS ........................................4

GLOSSARY OF TERMS AND ABBREVIATIONS ................................................................................5

EXECUTIVE SUMMARY....................................................................................................................7

CHAPTER 1: BACKGROUND AND SCOPE .......................................................................................9

CHAPTER 2: SOURCES AND ENVIRONMENTAL FATE ................................................................. 12

INTRODUCTION............................................................................................................................................. 12

A. CHEMICAL AND PHYSICAL PROPERTIES OF ANTIMONY ........................................................................................... 12

B. PRODUCTION AND USE................................................................................................................................... 13

C. ENVIRONMENTAL FATE................................................................................................................................... 15

CONCLUSION OF ENVIRONMENTAL FATE ................................................................................................................. 19

CHAPTER 3: ENVIRONMENTAL ASSESSMENT.............................................................................20

A. ESTIMATES OF ENVIRONMENTAL RELEASES OF ATO DURING PROCESSING AND USE OF FLAME RETARDANTS..................... 20

B. ATO HAZARD CHARACTERIZATION FOR ECOLOGICAL ORGANISMS ............................................................................ 27

C. ENVIRONMENTAL RISK CHARACTERIZATION......................................................................................................... 35

REFERENCES..................................................................................................................................48

APPENDIX A: HUMAN HEALTH HAZARD SUMMARY ..................................................................58
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List of Tables

Table 2-1. Physical-Chemical Properties of ATO........................................................................................13

Table 2-2. US Manufacturers and Importers of ATO. ................................................................................14

Table 2-3. Major End-Uses of Antimony in the US in 2011........................................................................14

Table 2-4. Environmental Bioconcentration/Bioaccumulation of Antimony in Aquatic Species. .............18

Table 3-1. Summary of 2010 TRI Releases of Antimony Compounds.1 .....................................................21

Table 3-2. Summary of E-FAST2 Results for Facilities Reporting TRI Releases, with Assumptions for Daily 

Release Amounts.a .................................................................................................................26

Table 3-3. Aquatic toxicity data for Sb2O3 and SbCl3. .................................................................................28

Table 3-4. Soil Toxicity Data for Antimony Compounds. ...........................................................................32

Table 3-5. Sediment Toxicity Data for Antimony Compounds...................................................................34

Table 3-6. Summary of All USGS-NWIS and STORET data for Samples Above Concentrations of Concern 

per Media Type.a

....................................................................................................................37

Table 3-7. Summary of E-FAST2 Results for Facilities Reporting TRI Water Releases. ..............................43

List of Figures

Figure 2-1. Representative Chemical Structure of Senarmontite (CASRN 12412-52-1)............................12

Figure 2-2. Representative Chemical Structure of Valentinite (CASRN 1317-98-2). ................................. 12

Figure 3-1. Locations of USGS-NWIS and STORET Monitoring Samples with Concentrations Greater Than 

COCs. ......................................................................................................................................40

Figure 3-2. Locations of USGS-NWIS and STORET Monitoring Samples with Concentrations Less Than 

COCs. ......................................................................................................................................40

Figure 3-2. Locations of USGS-NWIS and STORET Monitoring Samples with Concentrations Less Than 

COCs. ......................................................................................................................................41
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Authors / Contributors / Acknowledgements / Reviewers

The report was developed by the Office of Pollution Prevention and Toxics (OPPT), Office of 

Chemical Safety and Pollution Prevention (OCSPP). The 2012 workplan risk assessments were 

prepared based on existing data and any additional information received up to June 15, 2012. 

EPA Assessment Team

Lead: Sharon Oxendine, OPPT/RAD

Team: Christina Cinalli, OPPT/EETD

Rick Fehir, OPPT/EETD

Kirsten Hesla, OPPT/CCD

Jay Jon, OPPT/EETD

Wen-Hsiung Lee, OPPT/EETD 

Timothy Lehman, OPPT/EETD

Sara Pollack, OPPT/RAD

Emma Lavoie, OPPT/DfE

 

Acknowledgements

Portions of this document were developed with support from: 

Contractor name (contract number) Task 

Abt Associates (EP-W-08-010) Production and Uses

Eastern Research Group (EP-W-10-014) Releases

Versar (EP-W-10-005) Modeling, Monitoring

SRC, Inc. (EP-W-09-027) Environmental Fate

Internal Peer Reviewers

H. Kay Austin, OPPT/EETD

Stan Barone Jr., OPPT/RAD

External Peer Review - A peer review panel is being arranged for this influential workplan 

assessment product based upon need and following Agency peer review guidance. The format 

will be a teleconference of an ad hoc panel meeting consisting of independent experts. 
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Glossary of Terms and Abbreviations

ATO Antimony trioxide

BAF Bioaccumulation factor

BCF Bioconcentration factor

°C Degree Celsius

CASRN Chemical Abstract Service Registry Number

CBI Confidential business information

cm3 Centimeters cubed 

COC Concentration of Concern

d Day

DMR Discharge Monitoring Report 

dw Dry weight

EC50 Half Maximal Effective Concentration

E-FAST2 Exposure and Fate Assessment Screening Tool, version 2

EPA Environmental Protection Agency

EU RAR European Union Risk Assessment Report

FDA Food and Drug Administration

GMATC Geometric mean of maximum allowable toxicant concentration

IARC International Agency for Research on Cancer

IUR Inventory Update Rule 

kg Kilogram 

kg/yr Kilogram(s) per year

lb Pound

LC50 Half Maximal Lethal Concentration 

LOEC Lowest-observed-effect concentration

mg Milligram

mg/kg Milligram(s) per kilogram 

mg/kg-bw Milligram(s) per kilogram body weight

mg/L Milligram(s) per liter

mg/m3 Milligram(s) per cubic meter

μg/kg Microgram(s) per kilogram

μg/L Microgram(s) per liter 

MMAD Mass median aerodynamic diameter

NAICS North American Industry Classification System

NHANES National Health and Nutrition Examination Survey

NOAEC No-observed-adverse-effect concentration 

NOEC No-observed-effect concentration

NPDES National Pollution Discharge Elimination System

NWIS National Water Information System 

OCSPP Office of Chemical Safety and Pollution Prevention

OECD Organization for Economic Co-operation and Development

OPPT Office of Pollution Prevention and Toxics 
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OSHA Occupational Safety and Health Administration

PDM Probabilistic Dilution Model 

PET Polyethylene terephthalate

PNEC Predicted no-effect concentration

POTW Publically owned treatment works

PM Particulate matter 

ppb Parts per billion

PVC Polyvinyl chloride

REACH Registration, Evaluation, Authorization and Restriction of Chemicals

RWC Realistic worst case 

Sb Antimony

Sb3+ Trivalent antimony

Sb5+ Pentavalent antimony

Sb(OH)3 Antimonious acid

Sb(OH)6

- Antimonate

SbCl3 Antimony trichloride

Sb2O3 Antimony trioxide

Sb2O5 Antimony pentoxide

STORET STOrage and RETrieval Data Warehouse

TRI Toxics Release Inventory

TSCA Toxic Substances Control Act

US United States

USGS United States Geological Survey

WHO World Health Organization

ww Wet Weight

7Q10 Refers to seven consecutive days of lowest stream flow over a 10-year 

period based on USGS (t).
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Executive Summary

The category, “Antimony and Related Compounds” was identified for assessment as part of the 

United States (US) Environmental Protection Agency (EPA) Existing Chemicals Management 

Program. EPA reviewed the readily available information on antimonial compounds, and 

selected antimony trioxide, (CASRN 1309-64-4; ATO; Sb2O3), for further assessment based on: 

(1) high potential for exposure due to high production volume and widespread use in consumer 

products; (2) expected releases to aquatic, benthic, and terrestrial environments; (3) high 

persistence and low-to-moderate bioaccumulation potential; and (4) adverse effects reported 

in humans and laboratory animals. 

ATO is the most widely used antimonial compound, accounting for roughly 80 percent of 

primary (i.e., mined) antimony consumption in the US (USGS, 2011). ATO is mainly used as a 

flame retardant synergist for halogenated flame retardants used in textiles and plastics 

(Freedman et al., 2003); approximately 25 million pounds (lbs) of ATO were consumed for this 

end-use application in 2011 (USGS, 2011). The available US Geological Survey (USGS) data 

indicated no operational antimony mines or primary antimony production in the US in 2011, 

except for one company in Montana that produced antimony metal and oxide from a foreign 

feedstock (USGS, 2012a). Approximately 87 percent of the ATO consumed in the US between 

2007 and 2011 was imported, with the majority coming from China (USGS, 2012a). 

Data from the US EPA’s Toxics Release Inventory (TRI) for the 2010 reporting cycle indicated 

that approximately 970,000 lbs of ‘antimony compounds’ were released to land and roughly 

15,700 lbs were released to water by industries that use or produce ATO-containing flame 

retardants (TRI, 2010). On-site air releases totaled approximately 12,000 lbs, of which roughly 

two-thirds were from stack releases. A significant portion of the remaining fugitive air releases 

are likely related to the combustion of fossil fuels; however, the precise quantity cannot be 

determined from TRI data.

Based on a review of the available data regarding antimony concentrations in food and 

environmental media, and biomonitoring data obtained from the latest National Health and 

Nutrition Examination Survey (NHANES), general population exposure to antimony is expected 

to be low. Because food and water are the primary sources of general population exposure, 

and the less toxic (i.e., pentavalent) form of antimony predominates in these media, significant 

human health risks are not anticipated. This conclusion is supported by recent risk assessments 

completed for ATO in Canada and Europe. In addition, the US National Toxicology Program is 

currently conducting a two-year carcinogenicity study on ATO; EPA will review these results 

when they become available. The remaining area of potential concern, for effects on ecological 

organisms, was selected as the focus of the current assessment. This decision was based on the 

Agency’s review of available ecotoxicity information and reported environmental releases of 

‘antimony compounds’ in association with the manufacture and use of ATO-containing flame 

retardants. 
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To assess the ecological risks associated with ATO releases, EPA identified hazard benchmarks 

(i.e., concentrations of concern; COC) for water-, sediment-, and soil-dwelling organisms, which 

were subsequently compared to measured antimony concentrations in these media. This 

information was obtained from two independent environmental monitoring datasets, the USGS 

National Water Information System (NWIS) (water [1972 to 2012]; sediment [1987 to 2011]; 

and soil [2005 to 2010]) (USGS, 2012b) and EPA’s Storage and Retrieval (STORET) Data 

Warehouse (water and sediment [2002 to 2010) (US EPA, 2012c). In addition, site-specific 

modeling was conducted for selected TRI facilities (i.e., those with identified use or production 

of ATO-containing flame retardants) using EPA’s Exposure and Fate Assessment Screening Tool, 

version 2 (E-FAST2) (US EPA, 2010a) to estimate ATO surface water concentrations. 

To evaluate potential risks to ecological organisms, predicted surface water concentrations 

were compared to the identified hazard benchmarks. Generally speaking, risks are indicated 

when the monitored or modeled exposure concentrations are above the COC. Under this 

paradigm, the concern for ecological risk associated with ATO use as a synergist in halogenated 

flame retardants is expected to be low. Only one exceedance of the acute COC for aquatic 

organisms was predicted using the E-FAST2 model, and very few (i.e., <1 percent) of the 

environmental monitoring samples evaluated in this assessment exceeded the hazard 

benchmarks identified for ecological organisms. Perhaps more importantly, no exceedances 

were identified within the last three years (2009 to 2012). 

EPA identified key sources of uncertainty related to limitations in the available hazard and 

exposure information, and assumptions incorporated in the E-FAST2 model estimates of ATO 

surface water concentrations. Although these uncertainties may limit data interpretation, they 

do not diminish the findings reported in this assessment. The available data show very few 

instances (i.e., less than 0.4 percent) where measured or predicted levels in the ambient 

environment exceed the hazard benchmarks identified for ecological organisms. 

In summary, risks are expected to be negligible for water-, or sediment-dwelling organisms

based on the following considerations: 

• Use of the generic category, ‘antimony compounds’ and conservative assumptions 

regarding modeled releases likely overestimate exposure potential. 

• Use of highly sensitive ecological species to delineate conservative hazard benchmarks 

showed very few exceedances of the COCs. 

• Environmental monitoring data obtained during the last three years showed no 

exceedances of COCs. 

This assessment provides important insights regarding the potential risks of concern to 

ecological organisms associated with ATO’s use in halogenated flame retardants. Measured 

and modeled concentrations of ATO are assumed to represent reasonable estimates of

environmental exposures. 
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Chapter 1: Background and Scope

The category, “Antimony and Related Compounds” was identified for assessment as part of the 

United States (US) Environmental Protection Agency’s (EPA)’s Existing Chemicals Management 

Program. EPA’s Office of Pollution Prevention and Toxics (OPPT) reviewed the readily available 

information on antimonial compounds, and selected antimony trioxide, (CASRN 1309-64-4; 

ATO; Sb2O3), for further assessment based on: (1) high potential for exposure due to high 

production volume and widespread use in consumer products; (2) expected releases to aquatic, 

benthic, and terrestrial environments; (3) high persistence and low-to-moderate 

bioaccumulation potential; and (4) adverse effects reported in humans and laboratory animals. 

Global antimony (Sb) demand is largely driven by the production of antimonial compounds 

used in various consumer products such as medicines, polymers, resins, and textiles. 

Pentavalent antimonial compounds have been the mainstay of treatment for parasitic diseases 

(e.g., leishmaniasis and schistosomiasis) for over 70 years. ATO production is currently the 

largest end-use application for antimony, accounting for approximately 80 percent of global 

antimony consumption; a smaller portion (i.e., roughly 20 percent) is associated with metallic 

uses (Roskill, 2011). 

ATO use as a synergist in halogenated flame retardants was selected as the focus of the current 

assessment because this end-use application represents the largest global market for mined 

antimony. Global consumption of ATO in this sector has increased by approximately four

percent/yr since 2000 (Roskill, 2011). Though ATO has no inherent flame retarding capacity, 

when used as a synergist, it enhances the effectiveness of halogenated flame retardants, 

resulting in significant decreases in the total amounts of halogen (e.g., bromine or chlorine) 

needed to meet safety standards for flame resistance (Weil and Levchik, 2009). ATO is also 

used as a condensation catalyst for the manufacture of polyethylene terephthalate (PET), a 

large-volume commodity plastic used in bottles, films, and various food contact applications. 

This end-use application has been evaluated for safety and is regulated by the US Food and 

Drug Administration (FDA) and other international authorities (EU RAR, 2008; European Food 

Safety Authority,2004; Environment Canada/Health Canada, 2010); therefore, ATO use in PET 

plastics will not be further evaluated here.

Antimonial compounds are naturally occurring in the earth’s crust, though not particularly 

abundant. Environmental releases may result from natural (e.g., volcanic eruptions, windblown 

dust) or anthropogenic sources (e.g., combustion of fossil fuels, nonferrous metal smelting). 

Pentavalent antimony (Sb5+) is the most thermodynamically stable antimony species under 

most environmental conditions; however, trivalent antimony (Sb3+) predominates under 

anaerobic conditions (Environment Canada/Health Canada, 2010). 
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Chemical speciation and route of exposure are major determinants of antimony toxicity in 

humans. Generally speaking, pentavalent antimony is less toxic to humans than the trivalent 

species. Most antimony compounds are oxidized to the trivalent form when released to the 

environment; however, the available evidence suggests that over time, further oxidation to the 

less toxic pentavalent form may occur under aerobic conditions (EU RAR, 2008). 

General population exposure occurs mainly via ingestion of food and water, whereas inhalation 

and dermal contact are more common in occupational settings (ATSDR, 1992). Irritation at the 

point of contact (e.g., dermatitis, lung inflammation, pneumoconiosis) has been reported in 

workers following chronic inhalation exposure (NIOSH, 1978). The US Occupational Safety and 

Health Administration (OSHA) regulates worker exposure to antimony compounds with a 

permissible exposure limit of 0.5 mg/m3 (eight-hour, time-weighted average) (OSHA, 2012). 

ATO produces minimal systemic toxicity when administered at environmentally relevant 

concentrations due to poor systemic absorption, which effectively limits bioavailability (EU RAR, 

2008; WHO, 2003). Additional information regarding the human health effects associated with 

ATO exposure may be found in Appendix A.

Based on a review of the available data regarding antimony concentrations in food and 

environmental media, and biomonitoring data obtained from the US National Health and 

Nutrition Examination Survey (NHANES), general population exposure to antimony is expected 

to be low (CDC, 2012). Because food and water are the primary sources of general population 

exposure, and the pentavalent (i.e., less toxic) form of antimony predominates in these media, 

significant human health risks are not expected at ambient levels to which individuals may be 

exposed in the environment. This conclusion is supported by previous risk assessments for ATO 

in Europe and Canada (EU RAR, 2008; Environment Canada/Health Canada, 2010). In addition, 

the US National Toxicology Program is currently conducting a two-year carcinogenicity study on 

ATO; EPA will review these results when they become available. 

Unlike humans, there is no conclusive evidence to support a significant difference in the 

ecological hazards associated with exposure to pentavalent or trivalent forms of antimony. 

When released to the environment, antimony compounds release antimony ions upon 

dissolution and the total antimony ion concentration is of most importance when assessing the 

persistence, bioaccumulation, and toxicity of antimony in the environment (EU RAR, 2008). 

Substances that yield comparable amounts of the same antimony ion may be used to 

characterize compounds for which less information is available. EPA used studies with 

antimony trichloride (SbCl3) to assess hazards to aquatic- and sediment-dwelling organisms

because of limitations in the data available for ATO (Skeaff et al., 2012; Freedman et al., 2003). 

EPA assumed no significant impact to the risk findings, as both compounds release comparable 

amounts of antimony ion upon dissolution. 

EPA conducted an environmental exposure assessment based on monitoring data from the US 

Geological Survey (USGS) National Water Information System (NWIS) (USGS, 2012b) and the US 

Environmental Protection Agency (EPA) Storage and Retrieval (STORET) Data Warehouse (US 

EPA, 2012c), including a total of 5,493 water samples (i.e., 3,643 in USGS-NWIS and 1,850 in 
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STORET). In addition, the E-FAST2 model (US EPA, 2010a) was used to estimate surface water 

concentrations based on water releases reported in the 2010 TRI. Because TRI does not 

indicate a time-frame for reported water releases, the 2010 data were modeled using two 

exposure scenarios, based on total releases occurring over a period of 250 or 24 days/yr. This 

was done to provide a range of exposure estimates based on reported water releases from 

selected TRI facilities. 

To assess potential ecological risks, EPA identified hazard benchmarks, also designated as 

“concentrations of concern” (COCs) for water-, sediment-, and soil-dwelling organisms that 

were subsequently compared to measured antimony concentrations in these media. The 

scientific literature was reviewed to identify and evaluate the available information for use in 

hazard characterization. Publications were critically evaluated based on adherence to specific 

test guidelines, the endpoints used to assess toxicity, and the amount of detail provided in each 

study report. COCs were calculated using conservative ecotoxicity values derived from the 

most robust studies available in the published literature. 
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Chapter 2: Sources and Environmental Fate

INTRODUCTION

In order to assess the potential ecological risks of concern that may be associated with ATO use 

as a synergist in halogenated flame retardants, a firm understanding of the physical and

chemical properties, environmental releases, and the ultimate fate in environmental media are 

important. These topics are introduced here and the ATO risk characterization is discussed in 

Chapter 3.

A. CHEMICAL AND PHYSICAL PROPERTIES OF ANTIMONY

Antimony (Chemical Abstracts Service Registry Number [CASRN] 7440-36-0) is a naturally 

occurring metalloid that belongs to Group 15 of the periodic table; it can exist in +5, +3, 0, or 

-3 oxidation states, with +5 (i.e., pentavalent) and +3 (i.e., trivalent) being most common.

ATO is a dimorphic crystalline solid that exists in cubic (i.e., senarmontite; CASRN 12412-52-1) 

and orthorhombic configurations (i.e., valentinite; CASRN 1317-98-2). Cubic senarmontite is 

stable below 570 °C, whereas valentinite (i.e., infinite double chains) is formed above this 

temperature (Freedman, et al., 2003). The cubic form is shown in Figure 2-1, and the 

orthorhombic form is shown in Figure 2-2. 

Figure 2-1. Representative Chemical Structure of Senarmontite (CASRN 12412-52-1). 

O

O

O

Sb

Sb

O

O

Sb

O

O O

Sb Sb

O

Sb

O

O

Figure 2-2. Representative Chemical Structure of Valentinite (CASRN 1317-98-2). 

O

Sb

O O

Sb Sb

O

Sb

O O
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ATO exhibits negligible vapor pressure at 25 °C and tends to be soluble in hydrochloric acid, 

tartaric acid, and caustic alkalies; it is insoluble in organic solvents and only slightly soluble in 

water (Patnaik, 2003). The most reliable water solubility value (2.76 mg/L) was measured in 

reconstituted standard water (ISO 6341) at 22.2 °C during a seven-day equilibration period 

under slightly alkaline conditions (pH 8) (EU RAR, 2008). Typical physical-chemical properties of 

ATO can be found in Table 2-1. 

Table 2-1. Physical-Chemical Properties of ATO.

Property Value Comment

Physical state at 25 °C White solid

Particle size 0.2-13.89 μma

Estimated vapor pressure at 25 °C <1 × 10-6 torr

Water solubility at 22.2 °C 2.76 mg/L at pH 8b Value determined after 7 days In 

reconstituted standard water, 

loading = 100 mg/L . 

Water solubility at 20 °C 19.7 mg/L at pH 7c

25.6 mg/L at pH 9c

28.7 mg/L at pH 11c

Value determined after 24 hours in 

distilled water. 

Melting point 656 °Cd

Boiling point 1425 °Cd

a

Weidenfeller (2005) as cited in EU RAR (2008).

b

LISEC (2002) as cited in EU RAR (2008). c

Umweltanalytik GmbH (1993) as cited in EU RAR (2008). d

Lide (2000 as cited in the EU RAR, 2008).

B. PRODUCTION AND USE 

Several types of antimony compounds are known to exist in nature; however, the mineral 

stibnite is the primary source of processed antimony in commerce. In terms of the total 

production volume and potential end-use applications, ATO is the most widely used synthetic 

antimony compound. 

No primary antimony production occurred in the US in 2011, with the exception of one 

company that produced antimony metal and oxide from a foreign feedstock (USGS, 2012a). 

Approximately 87 percent of the ATO consumed in the US between 2007 and 2011 was 

imported from other countries (USGS, 2012a). 

Currently, there are no antimony mines operating within the US (USGS, 2006); the two main 

ATO producers are Chemtura Corporation and US Antimony Corporation (USGS 2005; Roskill, 

2011). While neither is listed as a manufacturer on the 2006 Toxic Substances Control Act 

(TSCA) Inventory Update Reporting (IUR) rule, their respective websites indicate that they 

currently manufacture and sell ATO products (Chemtura, 2012; US Antimony Corporation, 

2012). Table 2-2 provides a list of companies that manufacture or import ATO in the US. 
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Table 2-2. US Manufacturers and Importers of ATO. 

Company City State Manufacture Import

Arkema Inc. Philadelphia PA CBI CBI

Chemson Inc. Philadelphia PA No Yes

E. I. du Pont de Nemours and Company Wilmington DE No Yes

Eastman Kodak Company Rochester NY No Yes

Ferro Corporation Washington PA No Yes

General Electric Company

Mt. Vernon IN No Yes

Bridgeville PA No Yes

Washington WV No Yes

ICC Chemical Corporation New York NY No Yes

LG Chem America, Inc. Englewood Cliffs NJ No Yes

PolyOne Corporation Avon Lake OH No Yes

Sojitz Corporation of America New York NY No Yes

United Mineral & Chemical Corp. Lyndhurst NJ No Yes

CBI = confidential business information. 

Source: US EPA (2010b).

Approximately 240 million pounds (lbs) of ATO was produced globally in 2005, with the majority 

of production taking place in China (The Chemical Company, 2012). Total combined production 

of ATO in the US and Mexico was estimated at approximately 52.8 million lbs in 2005; however, 

the total amount of ATO consumed in the US during this time period was estimated at roughly 

70 million lbs (International Antimony Association, 2010). 

ATO is primarily used as a synergist in halogenated flame retardants applied to textiles and 

plastics; other reported applications include use as a plastic stabilizer, catalyst precursor, paint 

pigment, fining agent, or antisolarant (Freedman et al., 2003). Other major end-use

applications for ATO are shown in Table 2-3. 

Table 2-3. Major End-Uses of Antimony in the US in 2011. 

End-Use Market Share 

(%) 

Flame retardant synergist 36

Transportation (including batteries) 23

Chemicals 16

Ceramics and glass 12

Other 13

Source: USGS (2012a). 
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Though ATO has no inherent flame retarding capacity (US EPA, 2012a), when used as a 

synergist in halogenated flame retardants, it decreases the amount of halogen needed to 

impart acceptable flame resistance (USGS, 2004; Weil and Levchik, 2009). ATO interacts with 

chloride or bromide to form flame quenching antimony trichloride or antimony tribromide 

(Weil and Levchik, 2009). In many instances, ATO is added to (rather than incorporated in) the 

actual polymer matrix (AkzoNobel, 2012; Albemarle, 2000; ChemEurope, 2004), occurring as a 

separate, non-reactive (i.e., non-covalently bonded) phase. ATO may be found in a number of 

flame-retarded products, including electrical equipment, wires, automotive parts, building 

materials, furniture, carpets, mattress covers, plastics, and textiles (Environment 

Canada/Health Canada, 2010). The average ATO content in flame retardant formulations used 

to treat plastics generally ranges from 25 to 33 percent by weight, whereas the relative 

abundance of ATO in the final (flame-retarded) product can range from 1.5 to 12 percent

(USGS, 2004). Approximately 25 million lbs of ATO were consumed by this market sector in 

2011, as compared to approximately 50 million lbs in 1999. 

 

C. ENVIRONMENTAL FATE 

ENVIRONMENTAL PERSISTENCE OF ATO

Though not particularly abundant, antimonial compounds are naturally occurring in the earth’s 

crust. Environmental releases may result from natural (e.g., volcanic eruptions, windblown 

dust) or anthropogenic sources (e.g., combustion of fossil fuels, nonferrous metal smelting). 

ATO is an inorganic metal oxide; therefore, a fate analysis based on the octanol-water partition 

coefficient or the organic carbon-water partition coefficient is not applicable. Typical mass 

balance fugacity modeling is also inapplicable to ATO (or other metal ions) released upon 

dissolution, because these substances exert zero partial pressure and fugacity in air (Diamond

et al., 1992). ATO is persistent in all media (i.e., air, water, soil, and sediment), because the 

antimony ions issued upon dissolution cannot be degraded. Depending upon the ambient 

conditions (e.g., pH, redox potential, dissolved oxygen content), ATO (Sb2O3) may be oxidized to 

antimony pentoxide (Sb2O5), but this transformation may be reversed under anaerobic 

conditions in the environment (Environment Canada/Health Canada, 2010). 

Fate in Wastewater Treatment 

Effluents released from industrial facilities may contain antimony as a result of material 

handling and/or washing of equipment. This material may end up in industrial or municipal 

wastewater treatment plants, and as a result of alkalinization processes, a fraction will be 

deposited in sludge. Because sludge is commonly spread on agricultural fields, this application 

could potentially release antimony to soils, which may end up in local groundwater and/or 

surface waters because of soil leaching and runoff (Environment Canada/Health Canada, 2010). 
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Fate in Water

Due to the weathering of soils and sediment and the run-off from terrestrial environments, 

aquatic ecosystems (e.g., streams, rivers, ponds, lakes, bays, etc.) may serve as a sink for ATO 

released to the environment. The aqueous chemistry of antimony is complex and involves a 

wide range of oxygenated species whose stabilities depend mainly on the acidity and oxygen 

content of the receiving waters. Dissolved antimony can transform into a variety of species and 

form numerous complexes with dissolved ligands present in the aquatic environment (Schecher 

and McAvoy, 1992; Tipping, 2002). The neutral species antimonious acid, [i.e., Sb(OH)3], is 

expected to be the primary form issued upon dissolution and hydrolysis. 

Antimony concentrations in unpolluted natural waters are low, usually on the order of one ppb 

or less; levels detected in ocean surface waters tend to be even lower ( i.e., approximately 0.2 

ppb; Filella et al., 2009). Pentavalent antimony also has been detected in anaerobic 

environments in association with the following transport processes: movement associated with

detritus sinking from aerobic waters, biotransformation by marine organisms, and advection of 

surface waters containing high levels of Sb5+. All of these potential transport mechanisms 

assume a slow rate of conversion to Sb3+ in the absence of oxygen; the rate constant for this 

reaction was estimated at approximately 1.1 × 10-6 days-1 (Cutter, 1992). 

In a comprehensive review of the published literature on antimony speciation in natural waters, 

Filella et al. (2009) reported that relatively small amounts of Sb3+ were detected in oxygenated 

waters. This finding has been corroborated by other authors, such as Garbos et al. (2000) who 

determined that the majority of antimony detected in natural waters (i.e., 96 to 99 percent) 

was Sb5+. Cutter (1992) evaluated the rate of oxidation of Sb3+ to Sb5+ by measuring the depth 

profiles for antimony species in the upper 100 meters of the Black Sea. No Sb3+ was detected at 

surface levels; however, a gradual increase in the Sb3+ concentration (in association with a 

decline in Sb5+ levels) was observed at depths beyond 60 meters. The highest concentration of 

Sb3+ was found in deeper, largely anaerobic waters (i.e., 90 to 100 meters). An estimated 

pseudo-first-order rate constant of 0.008 day-1 was calculated for the oxidation of Sb3+ to Sb5+, 

corresponding to a residence time of approximately 125 days for Sb3+ in natural waters. 

Fate in Soil and Sediment

Due to the tendency to sorb to solid particles in aquatic media, a significant portion of dissolved 

antimony will end up in sediment, as evidenced by the logarithmic sediment-water partition 

coefficient (log Ksdw) for antimony, which generally ranges from 2.5 to 4.8 (Environment 

Canada/Health Canada, 2010). This can occur through adsorption to suspended particles as 

they settle out of solution (Hamilton-Taylor et al., 1984), or through precipitation of calcium 

antimonite (EU RAR, 2008). A portion of undissolved ATO may also occur in moist soils. 

Bioaccessibility to soil-dwelling organisms is largely governed by mobility and solubility in 

environmental media, which is limited under acidic conditions (i.e., pH 3-4) by adsorption to 

hydrous oxides of iron, manganese, and aluminum (HSDB, 2012). Changes in pH can also 

influence valence state, which further impacts solubility and leaching potential. Leaching 

experiments indicate that Sb5+ is the predominant antimony species issued under normal 

environmental conditions (≥ pH 6.3), whereas Sb3+ predominates at pH 2.7 (HSDB, 2012). 
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Fate in Air

Combustion processes are a major source of antimony air releases. Antimony particulates are

removed from the atmosphere by gravitational settling or wet and dry deposition, depending 

on particle size. Larger particles are generally removed within hours, whereas smaller particles 

require a longer period (on the order of weeks). In a model comparing particle size to volatility, 

antimony exhibited an average atmospheric half-life of approximately 3.2 days (ATSDR, 1992). 

As a non-gaseous element with a negligible vapor pressure, ATO is emitted to air principally in 

the form of fine particulate matter (PM). The European Risk Assessment Report (EU RAR, 2008) 

states that: (1) combustion or incineration processes are likely to transform antimony 

compounds to ATO regardless of the pre-incinerated form of antimony; (2) anthropogenic 

activities may result in long-range transport of a portion of ATO emitted to air; and (3) there are 

indications that a significant portion of the ATO present in the atmosphere may be water 

soluble. A study of wet and dry deposition over an eight-week period in an area that was 

presumably far from release sources found that 87 percent of the deposited antimony was 

dissolved in rain, 11 percent occurred as PM in rain, and approximately two percent was 

removed from air via dry deposition of PM (Stössel and Michaelis, 1986; as cited in EU RAR, 

2008). 

ENVIRONMENTAL TRANSFORMATION, BIOAVAILABILITY, AND BIOACCUMULATION

Transformation

Antimony can transition between various organic and inorganic forms in the environment 

(Filella et al., 2007). For example, microorganisms have been shown to biomethylate relatively 

small amounts (< 0.1 percent) of antimony, and binding to metal hydroxides has been 

associated with the oxidation of Sb3+ to Sb5+ (ATSDR, 1992; Filella et al., 2007; HSDB, 2012). 

These transformations are important because they impact antimony mobility in environmental 

media, as well as the bioavailability, and toxicity to ecological organisms. 

Bioavailability

Antimony is a natural constituent of soils and sediments. It is subject to transformations in 

environmental media that may make it more or less bioavailable depending on various factors, 

such as valence, pH, soil or sediment type, and the oxic or ionic conditions of aqueous 

environments (EU RAR, 2008). In addition, behavior in environmental media (e.g., sorption/

desorption) and availability to soil- or sediment-dwelling organisms is influenced by the 

presence of other metals such as iron, manganese, and aluminum (EU RAR, 2008). 

In aquatic systems, the bioavailability of antimony compounds may be impacted by solubility. 

Water solubility is dependent upon pH, which may increase the bioavailability of antimony to 

aquatic organisms at environmentally relevant pH levels (EU RAR, 2008). In natural waters, 

antimony will occur almost exclusively as Sb(OH)3 and [Sb(OH)6

-

] via hydrolysis of Sb3+ and Sb5+

ions, respectively (OECD, 2008). 
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Bioaccumulation

Some published studies suggest a potential for antimonial compounds to accumulate in aquatic 

organisms such as fishes, plants, and invertebrates (EU RAR, 2008); however, there is 

considerable uncertainty regarding the derivation of these values. For example, the data used 

may be available in the form of an abstract or robust summary in which the underlying 

methodology used for sample analyses are not reported, making it difficult to evaluate data 

quality. 

Antimony is not expected to exhibit significant bioconcentration potential in aquatic organisms. 

The bioaccumulation of metals in aquatic ecosystems is largely governed by trophic feeding 

groups, with detritivores accumulating higher levels than herbivores or predatory groups. For 

example, Corbicula fluminea, a filter-feeding clam that consumes algae, bacteria, and fine 

detritus, has been reported to bioaccumulate antimony to a greater extent than other 

predators or omnivores (Duran et al., 2007); however, Baeza et al. (2010) found no significant 

correlation between antimony bioaccumulation in C. fluminea and elevated antimony levels in 

sediments.

Heier et al. (2009) determined that antimony accumulation is minimal in brown trout (< 0.08 

μg/L). In another study, Gal et al. (2007) evaluated antimony levels in earthworms taken from a 

mining site where the antimony concentrations in soil ranged from 10 to 1,200 mg/kg. In the 

two species of earthworms evaluated, antimony concentrations ranged from 0.72 to 26 mg/kg

dw; however, the calculated bioconcentration factors (i.e., the ratio of antimony in biota to that 

in soil) were less than one, indicating minimal bioconcentration potential for these organisms. 

Additional information on antimony bioconcentration in saltwater and freshwater species can 

be found in Table 2-4. 

Table 2-4. Environmental Bioconcentration/Bioaccumulation of Antimony in Aquatic Species.

Salt Water Speciesa Fresh Water Speciesb

Fish BCF c: 0.15 (Two spot 

goby); BCF: 0.40 

(Shanny) 

Fish BAF c: 0.43 (Labeobarbus kimberleyensis)

Aquatic 

invertebrate

No data Aquatic 

invertebrate

BAF c: 5.65 (Hyalella azteca)

Algae BCF c: 17.00 (Coralline or 

red algae)

Algae BCF c: 24.00 (Chlorella vulgaris)

a

US EPA (2012b). b

Environment Canada/Health Canada (2010). c

BAF = bioaccumulation factor; BCF = bioconcentration factor
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CONCLUSION OF ENVIRONMENTAL FATE

ATO is an environmentally persistent metalloid that exhibits high persistence and low-tomoderate bioaccumulation potential. The octanol-water and organic carbon-water partition 

coefficients are not particularly useful for assessing the environmental fate of ATO, because 

inorganic antimony compounds are outside the domain of most existing fugacity models. 

Generally speaking, Sb5+ is the most thermodynamically favorable antimony species under 

aerobic conditions in the environment; however, Sb3+ predominates under anaerobic

conditions. Antimony is primarily removed from the atmosphere via wet and dry deposition. 

Mobility in soil and sediment is influenced by various factors, such as metal composition and 

pH; increased adsorption and decreased mobility occur in the presence of oxidized iron, 

manganese, or aluminum and is maximal under acidic conditions. 
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Chapter 3: Environmental Assessment

A. ESTIMATES OF ENVIRONMENTAL RELEASES OF ATO DURING PROCESSING AND USE OF 

FLAME RETARDANTS 

Information presented in this section focuses on industrial releases from sectors associated 

with ATO-based flame retardants used in plastic, rubber, and textile manufacturing.

INTRODUCTION

Domestic release data were identified from EPA’s TRI which contains publically available 

information on releases, including on- and off-site transfers, and other recycling information 

submitted by industry to comply with environmental regulations. TRI information obtained for 

ATO is summarized below. 

TRI Data

ATO is not specifically listed on the TRI, but is included within the broader category of 

‘antimony compounds’, which covers all chemicals that contain antimony. As such, it is not 

possible to separate ATO releases from those of other antimony-containing chemicals reported 

in the TRI database.

To identify the selected TRI reporting facilities, EPA examined the primary North American 

Industry Classification System (NAICS) codes reported in the 2010 TRI for antimony compounds. 

A full description of the 6-digit NAICS codes is available from the Department of Census 

(http://www.census.gov/eos/www/naics/). The NAICS codes descriptions include a general 

heading and several subcategories. A total of 270 facilities reported releases of antimony 

compounds to the TRI in 2010 (Table 3-1). The majority of releases were sent to land and other 

disposal media (which include on- and off-site transfers, landfill, underground injection, land 

treatment, surface impoundments, and other transfers for off-site disposal). The on- and offsite land and other disposal of antimony compounds totaled approximately 970,000 lbs, of 

which, approximately one-third was associated with on-site land releases from nine facilities 

(NAICS code 325188 - All Other Basic Inorganic Chemical Manufacturing). The 2010 TRI water 

releases reported for antimony compounds were significantly less than the reported land 

releases, totaling approximately 15,700 lbs. Of the total water releases, approximately 3,100 

lbs were associated with direct surface water discharges, and approximately 12,600 lbs were 

transferred to publicly owned treatment works (POTWs) or other off-site water treatment 

facilities. 
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Table 3-1. Summary of 2010 TRI Releases of Antimony Compounds.

1

Life Cycle Stage

NAICS

Total Number of 

Facilities 

Reporting

On-site and Off-site Releases and 

Disposal (lbs/yr)a

Primary 

NAICS 

Code

Description Total Air 

Releases

Total Water 

Releases b

Total Land and 

Other Disposal

Manufacture of antimony oxides 325188 All other basic inorganic chemical 

manufacturing

9 2,106 573 364,113

Plastics material and resin, 

synthetic rubber, and fiber 

manufacturing

325211 Plastics material and resin 

manufacturing

27 884 4,939 47,394

325212 Synthetic rubber manufacturing 2 85 26 2,497

325222 Noncellulosic organic fiber 

manufacturing

5 08 186 700

Total 34 1,377 5,151 50,592

Plastics compounding and 

conversion

325991 Custom compounding of 

purchased resins

55 1,231 540 81,014

326113 Unlaminated plastics film and 

sheet (except packaging) 

manufacturing

18 339 110 7,078

326121 Unlaminated plastics profile 

shape manufacturing

2 3 0 4,648

326130 Laminated plastics plate, sheet 

(except packaging), and shape 

manufacturing

2 10 1 3,229

326150 Urethane and other foam product 

(except polystyrene) 

manufacturing

3 0 0 0 

326199 All other plastics product 

manufacturing

25 330 10 68,625
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Table 3-1. Summary of 2010 TRI Releases of Antimony Compounds.

1

Life Cycle Stage

NAICS

Total Number of 

Facilities 

Reporting

On-site and Off-site Releases and 

Disposal (lbs/yr)a

Primary 

NAICS 

Code

Description Total Air 

Releases

Total Water 

Releases b

Total Land and 

Other Disposal

Total 105 1,914 661 164,594

Rubber compounding and 

conversion

326220 Rubber and plastics hoses and 

belting manufacturing

8 14 44 20,876

326291 Rubber product manufacturing for 

mechanical use 

3 30 0 9,106

326299 All other rubber product 

manufacturing

16 1,163 33 24,298

Total 27 1,208 77 54,280

Fabric Finishing 313210 Broadwoven fabric mills 2 60 0 2,058

313230 Nonwoven fabric mills 1 0 2,167 11,328

313311 Broadwoven fabric finishing mills 4 53 1,139 2,707

313312 Textile and fabric finishing (except 

broad woven fabric) mills 1 669 669 6,025

313320 Fabric coating mills 15 2,893 4,927 88,465

Total 23 3,675 8,902 110,583

Fiberglass insulation 

manufacturing

327993 Mineral wool manufacturing 3 0 0 4,765

Drawing and insulating of wires 

and fiber optic cables

331422 Copper wire (except mechanical) 

drawing 20 844 90 60,626

335921 Fiber optic cable manufacturing 2 0 0 4,815

335929 Other communication and energy 

wire manufacturing 38 3 25 101,160
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Table 3-1. Summary of 2010 TRI Releases of Antimony Compounds.

1

Life Cycle Stage

NAICS

Total Number of 

Facilities 

Reporting

On-site and Off-site Releases and 

Disposal (lbs/yr)a

Primary 

NAICS 

Code

Description Total Air 

Releases

Total Water 

Releases b

Total Land and 

Other Disposal

Total 60 847 115 166,601

Plastic-containing 

electronic/electrical product 

manufacturing

335931 Current-carrying wiring device 

manufacturing 5 255 5 17,733

Textile product mills and apparel 

manufacturing

314110 Carpet and rug mills 3 255 207 1,942

314999 All other miscellaneous textile 

product mills 1 0 0 31,415

Total 4 255 207 33,357

1 See: supplemental data file titled “Supplemental 2010 TRI Data for the TSCA Workplan Chemical Risk Assessment of ATO (External Review Draft).pdf” a Mass in lbs/yr can be converted to kg/yr by multiplying lbs/yr by 0.4536 kg/lb. b Includes transfers to POTWs and other off-site wastewater treatment facilities.
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The on-site air releases of antimony compounds totaled approximately 12,000 lbs, of which 

approximately two-thirds were from stack air releases and one-third were from fugitive air 

releases. It is expected that a significant portion of these releases are associated with the 

combustion of fossil fuels as opposed to the use of ATO-containing flame retardants, the 

quantity of which cannot be determined from TRI data.

TRI releases reported for ‘antimony compounds’ are used as a surrogate for ATO in this 

exposure assessment. It is assumed that the total releases reported for ‘antimony compounds’ 

would be higher than those that may be expected for ATO alone. Table 3-2 summarizes the 

most recent TRI information for releases reported by industry sectors identified using the NAICS 

codes covered under the scope of this assessment (i.e., those indicating use or production of 

ATO-containing flame retardants). 

MONITORING OF ATO IN THE ENVIRONMENT 

EPA developed subsets of environmental monitoring data obtained from targeted searches of 

the USGS-NWIS and EPA’s STORET databases in July 2012. Approximately 8,500 water, 

sediment and soil samples were collected from these databases. Data collection centered on 

the 10 states in which selected TRI facilities (i.e., those reporting use or production of ATOcontaining flame retardants) were located. 

Compilation of Environmental Monitoring Data from the USGS-NWIS Database

Environmental monitoring data were downloaded from the USGS-NWIS website 

(http://nwis.waterdata.usgs.gov/usa/nwis/qwdata, accessed in July 2012). A subset1 of the 

larger dataset, which spanned more than 30 years (1987 to 2011), was used for the exposure 

assessment. 

The dataset was limited to monitoring samples obtained from states (i.e., AL, IN, KY, NC, NJ, NY, 

SC, TN, TX, and VA) that included at least one of the 15 TRI facilities identified under the scope 

of this assessment. The USGS dataset was further refined i.e., to focus specifically on water, 

sediment, and soil samples obtained from these regions. The monitoring data were split into 

two groups: (1) measured antimony concentrations from all years, and (2) measured antimony 

concentrations obtained from 2009 to 2012. 

Compilation of Environmental Monitoring Data from the STORET Database

Another large source of environmental monitoring data was obtained from EPA’s STORET 

website (http://www.epa.gov/storet/dw_home.html, accessed in July 2012). The STORET 

dataset included measured antimony concentrations in water and sediment only and was 

limited to samples taken from states that included at least one of the TRI facilities identified in 

 

1 See attached file titled “Supplemental subset of USGS-NWIS Dataset for the TSCA Workplan Chemical Risk 

Assessment of ATO (External Review Draft).xlsx”
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Table 3-2.2 The STORET data were divided into two categories: (1) concentrations measured in 

water (μg/L), and (2) concentrations measured in sediment (mg/kg dw).

EXPOSURE ASSESSMENT

This purpose of this assessment was to evaluate ATO exposures to water-, soil-, and sedimentdwelling organisms. Two separate approaches based on environmental monitoring data and

modeled water releases were used to investigate selected TRI facilities. 

In the first evaluation, approximately 8,500 data points were obtained from the USGS-NWIS 

and EPA’s STORET databases. A large amount of water and sediment data was available from 

these sources. Data collection centered on the 10 states in which the selected TRI facilities (i.e., 

those reporting use or production of ATO-containing flame retardants) were located. None of 

the actual monitoring sites were located within the primary watershed of the TRI facilities 

identified under the scope of this assessment. For this reason, a second approach, based on 

reported TRI releases, was utilized to estimate aquatic exposures using the E-FAST2 model 

(available at http://www.epa.gov/oppt/exposure/pubs/efast.htm). 

Three selection criteria were used to identify TRI facilities: (1) reported water releases of 

‘antimony compounds’ above 1 lb/yr; (2) reported NAICS codes that indicate possible use of 

ATO as a flame retardant synergist; and (3) stream releases for which the lowest streamflow 

data, or “7Q10” value (i.e., the average consecutive seven-day stream flow data over a 10-year 

period) was available. The 7Q10 streamflow data are linked to the National Pollution Discharge 

Elimination System (NPDES) codes for each facility, which were found using EPA’s Discharge 

Monitoring Report (DMR) Pollutant Loading Tool (available at 

http://cfpub.epa.gov/dmr/error_correction.cfm).

Using this selection approach, EPA identified 36 TRI facilities (TRI 2010) that reported water 

releases of ‘antimony compounds’ and listed primary NAICS codes associated with ATO use as 

a synergist in halogenated flame retardants; 33 of these indicated releases >1 lbs/yr. NPDES 

numbers matching the reported latitudes and longitudes were found for 14 TRI facilities

providing site-specific stream flow rates for use in the E-FAST2 model. A summary of the input 

data used for the E-FAST2 model is provided in Table 3-2.

 

2 See attached file titled “Supplemental subset of STORET Dataset for the TSCA Workplan Chemical Risk 

Assessment of ATO (External Review Draft).xlsx”
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Table 3-2. Summary of E-FAST2 Results for Facilities Reporting TRI Releases, with Assumptions for Daily Release Amounts.

a

Facility Name Latitude Longitude NPDES 

Code

Total Surface 

Water 

Discharge

Based on TRI 

(lbs) 

Scaled 

Annual 

Release

(kg)

Results

Daily 

Release

(250 Days) 

(kg)

Results

Daily 

Release

(24 Days)

(kg)

Eastman Kodak Co TN Eastman Co Div, Kingsport, TN, 

37662

36.519823 -82.540429 TN0002640 1,042 557.22 2.23 23.22

Guilford East Plant, Kenansville, NC, 28349 35.021587 -77.859994 NC0002305 669 357.75 1.43 14.91

Auriga Polymers Inc.Spartanburg Facility, Spartanburg, 

29307 

35.030528 -81.861366 SC0002798 320 171.12 0.68 7.13

Sabic Innovative Plastics US LLC, Selkirk, NY, 12158-0145 42.575416 -73.853563 NY0007072 250 133.69 0.53 5.57

Sabic Innovative Plastics Mt. Vernon, LLC, Mount Vernon, 

IN, 47620-9364

37.906389 -87.927778 IN0002101 250 133.69 0.53 5.57

Sage Automotive Interiors Abbeville Plant, Abbeville, SC, 

29620 

34.167222 -82.371389 SC0000353 248 132.62 0.53 5.53

Performance Fibers Operations Inc., Salisbury Plant, 

Salisbury, NC, 728147 

35.720234 -80.610867 NC0004944 95 50.80 0.20 2.12

Dupont Teijin Films, Chester, VA, 23836 37.346259 -77.285811 VA0003077 51 27.27 0.11 1.14

Haywood Co, Brownsville, TN, 380121797 35.605911 -89.240068 TN0041939 28 14.97 0.06 0.62

Bayshore Industrial La Porte, TX, 77571 29.63038 -95.030311 TX0022799 13.505 7.22 0.03 0.30

Covalence Adhesives, Franklin, KY, 42134 36.753889 -86.575278 KY0074659 5 2.67 0.01 0.11

General Cable Industries Inc., Marion, IN, 46953-2406 40.55425 -85.654944 IN0002372 5 2.67 0.01 0.11

Borealis Compounds Inc., Port Murray, NJ, 07865 40.813361 -74.888111 NJ0028657 5 2.67 0.01 0.11

Cerro Wire LLC, Hartselle, AL, 35640 34.412913 -86.917395 AL0054674 5 2.67 0.01 0.11 a

These screening-level estimates are based on a range of days of release, which may not represent actual releases and environmental concentrations at these facilities.

NPDES = National Pollution Discharge Elimination System

 
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Because TRI facilities do not indicate the total number of release days per year (i.e., a required 

input for E-FAST2 modeling), two release scenarios were modeled (assuming total TRI releases 

of ‘antimony compounds’ reported during the 2010 reporting cycle occurred over a period 

spanning 24 or 250 days). The first scenario (i.e., assuming total releases occurred over a 

period of 250 days) was selected based on the fact that a typical 260 work days and 10 holidays

generally occur during a calendar year.

3

 The more conservative scenario (i.e., 24 release 

days/yr), was selected because some facilities may only incur releases as a result of bi-monthly 

cleaning practices.4 Both release scenarios were used to estimate surface water concentrations 

using the E-FAST2 model of water releases reported by the 14 TRI facilities identified for 

consideration in this assessment (Table 3-2). These release scenarios were developed to 

provide a reasonable range of estimated surface water concentrations for assessing potential 

risks to aquatic organisms. Results of the exposure assessment are provided in table 3-7. 

 

B. ATO HAZARD CHARACTERIZATION FOR ECOLOGICAL ORGANISMS

The hazard information described in this section was evaluated for acceptability based on 

criteria established for aquatic toxicity testing within EPA’s OPPT (US EPA, 2009). The most 

reliable hazard data were obtained for ATO (Sb2O3) and antimony trichloride (SbCl3). 

The scientific literature was reviewed to identify laboratory animal studies that could be used 

to assess hazards to ecological organisms. Publications were critically evaluated based on the 

endpoints used to assess toxicity, the amount of detail provided in each study, and adherence 

to specific test guidelines. Ultimately, the COCs identified for ecological organisms in water, 

soil, and sediment were based on the most robust ecotoxicity information available in the 

published literature (Summarized in Table 3-3). 

ACUTE TOXICITY TO AQUATIC ORGANISMS

EPA selected acute aquatic toxicity studies for fish, invertebrates, and plants; SbCl3 was used as 

the test substance for all of these species, whereas Sb2O3 was used in only one plant study 

(Table 3-3). The effect levels provided below are based on the measured antimony ion 

concentrations reported in these studies. 

 

The acute toxicity to fish species was evaluated using SbCl3 with red sea bream (Pagrus major) 

(Takayanagi, 2001). A 96-hr LC50 of 6.9 mg/L was reported by the authors. Though this study 

was determined to be reliable, uncertainties regarding speciation and the specific test 

concentrations (i.e., only a range of concentrations was provided in the report) preclude its use 

for derivation of the COC.

 

3 See attached file titled “Supplemental E-FAST2 Results - 250 days per yr scenario for the TSCA Workplan 

Chemical Risk Assessment of ATO (External Review Draft).pdf” 4 See attached file titled “Supplemental E-FAST2 Results - 24 days per yr scenario for the TSCA Workplan 

Chemical Risk Assessment of ATO (External Review Draft).pdf” 
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Table 3-3. Aquatic toxicity data for Sb2O3 and SbCl3.

Test Organism Species Test 

Type Endpoint Antimony 

Compound Value Data Adequacy Reference

Fish Pagrus major Acute 96-hr LC50 SbCl3 6.9 mg Sb/L Inadequate Takayanagi (2001)

Aquatic 

invertebrate

Chlorohydra 

viridissima

Acute 96-hr LC50 SbCl3 1.77 mg Sb/L Adequate, used for 

COC derivation

(acute)

TAI (1990)

Aquatic plant Pseudokirchneriella 

subcapitata

 72-hr LC50

(growth rate)

SbCl3 EC50 > 36.6 mg/L

NOEC = 2.11 mg Sb/L

LOEC of 4.00 mg Sb/L

GMATC = 2.91 mg Sb/L

Adequate Heijerick and 

Vangheluwe (2004) 

Aquatic plant P. subcapitata 72-hr LC50

(growth rate)

Sb2O3 NOEC = 0.396 mg Sb/L

LOEC = 1.32 mg Sb/L

GMATC = 0.723 mg Sb/L

Inadequate LISEC (2001) 

Fish Pimephales 

promelas

Chronic 30-day

(growth)

SbCl3 NOEC = 1.13 mg Sb/L

LOEC = 2.31 mg Sb/L

GMATC = 1.62 mg Sb/L

Adequate, used for 

COC derivation 

(chronic)

Kimball (1978) 

Fish P. promelas Chronic 30-day

(growth)

Sb2O3 NOEC >0.0075mg /L Adequate LeBlanc and Dean 

(1984) 

Aquatic 

invertebrate

Daphnia

magna

Chronic 21-day

(reproduction)

SbCl3 NOEC = 1.74 mg Sb/L

LOEC = 3.13 mg Sb/L

GMATC = 2.33 mg Sb/L

Adequate Heijerick and 

Vangheluwe 

(2003b)a) 

NOEC = no observed effect concentration

LOEC = lowest-observed-effect concentration
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For aquatic invertebrates, a 96-hr test was conducted with SbCl3 in hydra (Chlorohydra 

viridissima) resulting in an LC50 value of 1.77 mg/L (TAI, 1990). This value is used to determine 

an acute COC for aquatic invertebrates, as it is a reliable study conducted in a sensitive species

(EU RAR, 2008). In addition, this study provided both nominal and measured concentrations for 

the trivalent form of antimony.

Two studies using an algal species (Pseudokirchneriella subcapitata) were conducted using

either Sb2O3 or SbCl3. Growth rate (ErC50; effective concentration wherein 50 percent of the 

tested organisms experienced a decline in growth rate) was determined to be the most 

sensitive endpoint, with the geometric mean of the maximum allowable toxicant concentration 

(GMATC) determined to be 2.91 and 0.723 mg/L for Sb2O3 and SbCl3, respectively (Heijerick and 

Vangheluwe, 2004; LISEC, 2001). The LISEC (2001) study is considered unreliable because the 

ErC50 value could not be determined due to uncertainties regarding the concentration response. 

For example, the limit concentration resulted in minimal inhibition (three percent) of the 

growth rate, which is considered to be the most sensitive endpoint (EU RAR, 2008). Though the 

data reported by Heijerick and Vangheluwe (2004) are reliable (i.e., based on the Organization 

for Economic Cooperation and Development (OECD) Guidelines for the Testing of Chemicals 

(Freshwater Alga and Cyanobacteria, Growth Inhibition Test)), the reported ErC50 value 

(>36.6 mg/L) indicates that this species is not particularly sensitive to SbCl3. 

CHRONIC TOXICITY TO AQUATIC ORGANISMS

Chronic toxicity studies using both Sb2O3 and SbCl3 are available, but only for fish and aquatic

invertebrates (Table 3-3). No reliable chronic toxicity studies were available for aquatic plants; 

therefore, acute studies were considered for this endpoint. 

In a 30-day chronic toxicity study with SbCl3 in fathead minnows (Pimephales promelas), growth 

was determined to be the most sensitive endpoint (Kimball, 1978). The authors reported a 

GMATC value of 1.62 mg/L, which was used to calculate a chronic COC for this assessment. A 

second study that evaluated Sb2O3 effects in P. promelas reported a no-observed effect 

concentration (NOEC) > 0.0075 mg/L, based on growth as the most sensitive endpoint (LeBlanc 

and Dean, 1984). This study was not selected for calculating a chronic COC due to the lack of 

effects observed at the highest concentration tested. Heijerick and Vangheluwe (2003b) 

conducted a 21-day test with SbCl3 in aquatic invertebrates (Daphnia magna). Reproduction 

was the most sensitive endpoint identified in this study, yielding a GMATC value of 2.33 mg/L. 

Though this study was reliable, the data were not selected for derivation of a chronic COC 

because the GMATC for P. promelas indicates that of the species evaluated, fish are most 

sensitive. 

AQUATIC COC DERIVATION

The acute COC for aquatic organisms was derived from the 96-hr LC50 of 1.77 mg/L obtained 

using SbCl3 in the aquatic invertebrate, Chlorohydra viridissima. This value was divided by an 
DRAFT DO NOTE CITE OR QUOTE

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assessment factor (uncertainty factor) of five for invertebrate species to yield an acute COC of 

0.354 mg/L (354 ppb) in accordance with OPPT guidance (US EPA, 2009). 

The chronic COC for aquatic organisms was derived from the 30-day GMATC for growth 

(1.62 mg/L ) determined using SbCl3 in fish (P. promelas) (Kimball, 1978). This value was divided 

by an assessment factor (uncertainty factor) of 10 for fish species in accordance with OPPT 

guidance (US EPA, 2009) to yield a chronic COC of 0.162 mg/L (162 ppb).

The Kimball (1978) study was also used to determine a predicted no-effect concentration 

(PNEC) of 0.113 mg/L in the EU risk assessment (EU RAR, 2008); however, only the NOEC value 

(1.13 mg/L) was used. For hazard assessment purposes, the EU derives PNECs by utilizing the 

lowest NOEC value and applying an assessment factor of 10 (EU RAR, 2008; EU, 2003). The EPA 

approach for determining a COC from a chronic study utilizes the GMATC value (if applicable) 

from the lowest-observed-effect concentration (LOEC) and the NOEC. EPA applied an

assessment factor of 10 in accordance with OPPT guidance (US EPA, 2009). The Environment 

Canada/Health Canada (2010) risk assessment used the same data provided in the European 

Union Risk Assessment Report (EU RAR, 2008) and relied on similar methods to calculate a 

PNEC of 0.113 mg/L. 

CHRONIC TOXICITY TO TERRESTRIAL SOIL INVERTEBRATES 

EPA identified chronic toxicity studies for soil dwelling invertebrates. Several studies were 

available from secondary sources; however, only the study from Moser (2007) was considered 

reliable. The study is described in the following excerpt taken from the EU RAR (2008): 

“Moser (2007) studied the toxicity of Sb to the springtail Folsomia candida 

(reproduction and mortality) using aged (approximately 32 w) Sb2O3-amended soil. Ten 

(10-12 d old) synchronized springtails were put onto 30 g moist soil in a glass vessel 

during a four-week exposure. Five replicates were used for each test concentration and 

the measured test concentrations were 90, 322, 999, 2930, and 10119 mg Sb/kg soil dw. 

Additionally, the springtails were also tested using uncontaminated field soil and an 

untreated artificial soil as controls, based on OECD 207. The positive control used on 

springtail reproduction was the herbicide Betosip (a.i. 159 g/L phenmedipham). At the 

end of the exposure period, the number of juveniles in each test vessel was counted 

after floating. The mortality of the springtails was also recorded. At day 28, the pHvalue and the moisture of the artificial soil for each concentration in additional vessels 

without springtails were determined for both mortality and reproduction, the highest 

effect observed was below 50% in any of the treatments. Consequently, LC50 and EC50

values could not be calculated, but were estimated as >10,119 mg Sb/kg soil dw for each 

one of the endpoints. The NOECreproduction was approximately 999 mg Sb/kg dw; the 

LOECreproduction was approximately 2,930 mg Sb/kg dw. All reported values refer to 

measured concentrations.” 
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The remaining studies were reviewed and evaluated by EPA, but were not used for COC 

derivation due to deficiencies (or discrepancies) in study design and uncertainties associated 

with inadequate or missing information are summarized in Table 3-4. 

TERRESTRIAL SOIL COC DERIVATION

To determine the COC for soil invertebrates, the NOEC (999 mg Sb/kg dry weight [dw]) and 

LOEC (2,930 mg Sb/kg dw) for reproductive endpoints (Moser, 2007) were used; the GMATC 

from these values was 1,710.9 mg Sb/kg dw. This was divided by an assessment factor5 of 10 to 

yield 171.09 mg Sb/kg dw for the chronic COC. Since no acute toxicity studies were identified 

that assessed effects on soil-dwelling organisms, EPA used the GMATC value obtained from the 

chronic study (1,710.9 mg Sb/kg dw) as the acute COC, in accordance with OPPT guidance, (US 

EPA, 2009). 

 5 The (US EPA, 2009) ecotoxicity assessment factors used to calculate concern concentrations for aquatic 

organisms will be used to calculate the concern concentrations for soil and sediment organisms for the purposes of 

this hazard assessment. While this document also refers to the assessment of discrete organic chemicals, it is also 

part of the guidance used in OPPT to use the same assessment factors for assessing hazards associated with 

inorganic metals. 
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Table 3-4. Soil Toxicity Data for Antimony Compounds.

Test 

Organism Species Test 

Type Endpoint Antimony 

Compound Value Data Adequacy Reference

Springtail Folsomia candida ISO 

11267 

Reproduction Sb2O3 NOECreproduction = 999 mg 

Sb/kg dw

LOECreproduction=2,930 mg 

Sb/kg dw

Adequate, used for COC 

derivation

Moser (2007)

Earthworm Eisenia fetida ISO

11268-2 

Adult survival/ 

juvenile 

production

Sb2(SO4)3 NOEC/LOEC adult survival = 

617/697 mg Sb/kg

NOEC/LOEC juvenile production = 

60/86 mg Sb/kg

Inadequate Simini et al.

(2002) 

Enchytraeid Enchytraeus 

crypticus

ISO 

16387 

Adult 

survival/ 

juvenile 

production

Sb2(SO4)3 NOEC/LOEC adult survival = 

384/538 mg Sb/kg 

NOEC/LOEC juvenile production = 

100/140 mg Sb/kg

Inadequate Kuperman et 

al. (2002) 

Springtail F. candida ISO 

11267 

Adult 

survival/ 

juvenile 

production

Sb2(SO4)3 NOEC/LOEC adult survival = 

100/126 mg Sb/kg

NOEC/LOEC juvenile production = 

100 /126 mg/kg

Inadequate Phillips et al.

(2002) 
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SEDIMENT INVERTEBRATE TOXICITY

Toxicity to sediment organisms in freshwater systems has been investigated in three different 

species (EU RAR, 2008). These test species included: (1) the bottom-dwelling amphipod 

(Hyalella azteca), which is a surface deposit and filter feeder, (2) the midge larvae (Chironomus 

riparius), which burrows and feeds in sediment and on detritus, and (3) the oligochaete 

(Lumbriculus variegatus), which feeds in sediment and interstitial spaces below the watersediment interface (Heijerick and Vangheluwe, 2003a, 2005 a, 2005b). A summary of the 

sediment toxicity studies is provided in Table 3-5.

Heijerick and Vangheluwe (2003a) exposed amphipods (H. azteca) to SbCl3 at five 

concentrations (ranging from 30.8 to 249 mg Sb/kg weight wet [ww]; 44 to 355 mg Sb/kg dw) in 

a sediment-water system for 28 days. Each test concentration included 13 replicates with 

10 amphipods each. Four replicates were used for the 28-day growth and survival endpoints, 

and eight replicates were used to evaluate effects on survival and reproduction on day 35 and 

42 (including growth). The remaining replicate was used to measure the antimony 

concentration in sediment. After the initial exposure period, the amphipods were removed 

from the sediment and placed in sediment-free chambers for another 14 days. Effects on 

survival (day 28, 35, 42), growth (day 28, 42), and reproduction (number of offspring per female 

from day 28 to 42) were evaluated. Growth (weight and length) was identified as the most 

sensitive endpoint after 28 days of exposure, resulting in a NOEC of 87 mg Sb/kg ww (124 mg 

Sb/kg dw).

For the study with the oligochaete (L. variegatus), Heijerick and Vangheluwe (2005a) exposed 

adult animals to SbCl3 in a sediment-water system for 28 days. Effects on survival, 

reproduction, and growth were evaluated at the end of the exposure period. The study was 

performed using six exposure concentrations (23 to 445 mg Sb/kg ww; 33 to 636 mg Sb/kg dw), 

a control (<1.4 mg Sb/kg ww), and seven replicates per concentration. Six replicates were used 

to evaluate effects on survival, reproduction, and growth after 28 days of exposure; the

remaining replicate was used to measure the antimony concentration in sediment. Growth 

(weight) was determined to be the most sensitive endpoint, resulting in a NOEC of 78 mg Sb/kg 

ww (112 mg Sb/kg dw).

Two-day-old midge larvae (C. riparius) were exposed to a range of SbCl3 concentrations in a 

sediment-water system until the larvae transformed to the adult phase (Heijerick and 

Vangheluwe, 2005b). Larval mortality and growth, and emergence to midges were determined 

after 14 and 28 days of exposure. The study was performed with six concentrations (23 to 445 

mg Sb/kg ww; 33 to 636 mg Sb/kg dw) and a control (<1.4 mg Sb/kg ww; <2.0 mg Sb/kg dw). 

Eleven replicates were included for each concentration, five of which were used to evaluate 

effects on survival and growth after 14 days of exposure. Another five were used to determine 

the extent of emergence after 28 days of exposure, and the remaining replicate was used to 

measure the antimony concentration in sediment. Growth (weight) was the most sensitive 

endpoint, resulting in a NOEC of 78 mg Sb/kg ww (112 mg Sb/kg dw).
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Table 3-5. Sediment Toxicity Data for Antimony Compounds.

Test Organism Species Test Type Endpoint Antimony

Compound

Value Data 

Adequacy

Reference

Amphipod Hyalella 

azteca

42-day chronic 

sediment toxicity test Survival/growth/

reproduction SbCl3

NOEC = 87 

mg Sb/kg ww 

(124 mg 

Sb/kg dw)

Adequate Heijerick and 

Vangheluwe (2003a) 

Oligochaete Lumbriculus 

variegatus

OECD 

“Bioaccumulation; 

Sediment test using 

benthic 

oligochaetes” and the 

EPA 600/R-99/064 

Section 13, Test 

Method 100.3 

“Lumbriculus

variegatus 

bioaccumulation test 

for sediments”

Survival/growth/

reproduction SbCl3

NOEC = 78 

mg Sb/kg ww 

(112 mg 

Sb/kg dw)

Adequate Heijerick and 

Vangheluwe (2005a) 

Midge larvae Chironomus 

riparius

OECD guideline 218 

sediment-water 

chironomid toxicity 

test using spiked 

sediment

Survival/growth/

reproduction SbCl3

NOEC = 78 

mg Sb/kg ww 

(112 mg 

Sb/kg dw)

Adequate Heijerick and 

Vangheluwe (2005b) 
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To determine the chronic COC for toxicity to invertebrates in freshwater sediment, the NOEC 

for the growth endpoint (78 mg Sb/kg ww) was used as 112 mg Sb/kg dw (based on a 

70/100 calculated ww/dw ratio). The effect levels reported in the Heijerick and Vangheluwe 

(2005a, b) studies on oligochaete and the midge larvae were divided by an assessment factor6

of 10 to yield 11.2 mg Sb/kg dw as the chronic COC. In the absence of a reliable acute toxicity 

study, the NOEC value obtained from the chronic study (112 mg Sb/kg dw) was used for the 

acute COC. The dw value is used for comparison with the suspended sediment data obtained 

from the USGS-NWIS samples (collected as mg Sb/kg dw). 

The Heijerick and Vangheluwe (2005a, b) studies were also used in the EU risk assessment to 

derive a PNEC value of 11.2 mg/kg dw (EU RAR, 2008); however, even though a GMATC can be 

calculated, the EU derived a PNEC by utilizing the lowest NOEC value and applying an 

assessment factor of 10 (EU RAR, 2008). OPPT has not established an approach for determining 

a chronic COC for sediment based on a chronic study; therefore, in the absence of an 

established OPPT methodology, the EU approach will be used in combination with a 10-fold 

assessment factor, in accordance with OPPT guidance (US EPA, 2009). 

C. ENVIRONMENTAL RISK CHARACTERIZATION

The goal of this environmental risk characterization is to evaluate potential risks to water and 

sediment-dwelling organisms as a result of exposure to ATO. To this end, measured and 

modeled environmental concentrations are compared to the hazard benchmarks (COCs) 

identified for these compartments. EPA’s environmental exposure assessment included a 

characterization of the available environmental monitoring data and modeling of industryreported water releases. 

SUMMARY OF EXCEEDANCES AS INDICATED BY ENVIRONMENTAL MONITORING DATA

EPA’s exposure assessment utilized a robust environmental monitoring dataset. Out of a total 

of 8,500 environmental monitoring samples for water, sediment, and soil, only a small number 

exceeded the respective COCs for these media. The environmental monitoring data are 

summarized below and presented in Table 3-6. 

A total of 5,493 water samples were evaluated. Of the 3,643 water samples obtained from the 

USGS-NWIS database from 1972 to 2012, only five samples (~0.4 percent) exceeded the chronic 

COC for water (162 μg/L); these samples were collected between 1987 and 1988. Of the 1,850 

water samples obtained from the STORET database between 2002 and 2010, seven samples 

(~0.4 percent) exceeded the chronic COC for water.

 6 The US EPA (2009) ecotoxicity assessment factors used to calculate concern concentrations for aquatic organisms 

will be used to calculate the concern concentrations for soil and sediment organisms for purposes of this hazard 

assessment. While this document also refers to the assessment of discrete organic chemicals, it is also part of the 

guidance used in OPPT to use the same assessment factors for assessing hazard associated with inorganic metals. 
DRAFT DO NOTE CITE OR QUOTE

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A total of 2,985 sediment samples were evaluated in the exposure assessment; 1,753 sediment 

samples collected from 1987 to 2011 were obtained from the USGS-NWIS database. Of these, 

only 14 samples (~0.9 percent) exceeded the chronic COC for sediment (11.2 mg/kg dw) and all 

were obtained before 2005. There were 1,222 sediment samples obtained from the STORET 

database from 2002 to 2010; six (~0.5 percent) were determined to be above the chronic COC

for sediment (11.2 mg/kg dw). No exceedance of the COC for water-, sediment-, or soildwelling organisms was identified within the last three years (i.e., from 2009 to 2012) for any of 

the TRI facilities evaluated in this assessment. 

Only 32 soil samples were obtained from the USGS-NWIS database between 2005 and 2010; 

none were above the acute COC for soil (171.09 mg/kg dw); no soil samples were available in 

the STORET database. Figure 3-1 shows locations where water or sediment samples obtained 

from the USGS-NWIS and STORET data subsets exceeded the respective COCs for water- or

sediment-dwelling organisms. Figure 3-2 shows all of the locations evaluated and determined 

to be lower than the identified hazard benchmarks (i.e., COCs). 

In summary, the environmental monitoring data collected from two national datasets (USGSNWIS and STORET) indicated minimal concern for ecological risks from ATO use in halogenated 

flame retardants. Less than 0.01 percent of the environmental monitoring samples collected in 

the 10 states covered under the scope of this assessment showed antimony concentrations 

above the COC for water or sediment, and all were collected more than three years ago (Figure

3-1). The average antimony concentration for the 3,643 water samples obtained from the 

USGS-NWIS dataset was 4 μg/L, which is roughly 40 times lower than the COCs for aquatic 

organisms. In addition, there were 1,753 sediment samples in the USGS-NWIS dataset with an 

average antimony concentration of 1.3 mg/kg dw, which is approximately 10 times lower than 

the chronic COC for sediment-dwelling organisms (Figure 3-2). 
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Table 3-6. Summary of All USGS-NWIS and STORET data for Samples Above Concentrations of Concern per Media Type.

a

Sample Type Parameter Code Date of 

Sample

Value

Above

COC

Station Name Latitude Longitude

Data Quality 

Description (USGSNWIS data only)b

Water – USGS-NWIS 

Chronic COC for water =

162 μg/L 

Acute COC for water =

354 μg/L 

3,6439 total water 

samples;

Only 5 were above COC; 

No samples above COC in 

2009 or later

01097: Antimony, 

water, filtered,

μg/L

26-Aug-87 350c μg/L Red River near Quanah, TX 34.4131291 -99.7345385 Historical data

17-Feb-88 350c μg/L Red River near Quanah, TX 34.4131291 -99.7345385 Historical data

25-Aug-87 350c μg/L Buck Creek at Loco, TX 34.70283589 -100.1881691 Historical data

25-Aug-87 350c μg/L Buck Creek near Childress, 

TX

34.61172738 -100.1109427 Historical data

26-Aug-87 350c μg/L Salt Fork Red River near 

Wellington, TX

4.95755294 -100.220949 Historical data

Water – STORET

Chronic COC for water =

162 μg/L 

Acute COC = 354 μg/L 

1,850 total water samples: 

7 Samples reported above 

COC for water (162 μg/L) 

10-Dec-08 7,600 μg/L Grays Creek, TN 35.200600 -89.681500 NA

26-Oct-04 2,000 μg/L Beech River, TN 36.605000 -88.118800 NA

3-Nov-04 2,000 μg/L Muddy Creek-Unnamed 

Tributary, TN

35.095833 -88.499444 NA

18-Dec-02 1,000 μg/L Alexander Creek, TN 36.520600 -82.717800 NA

26-Oct-04 1,000 μg/L Big Sandy River, TN 36.232500 -88.100300 NA

23-Sep-04 1,000 μg/L Buffalo River, TN 35.457800 -87.775800 NA

12-Oct-04 1,000 μg/L Clinch River, TN 36.569400 -83.041700 NA

Sediment – USGS 

Chronic COC = 11.2 mg/kg

Acute COC = 112 mg/kg 

1,753 total sediment

samples;

14 samples above COC 

for sediment (dw); No 

29816: Antimony, 

suspended 

sediment, total 

digestion, dw

12-Jan-88 90 mg/kg Kentucky River at Lock 4 at 

Frankfort, KY

38.2017388 -84.8816171 Historical data

20-Dec-89 42 mg/kg Kentucky River at Lock 2 at 

Lockport, KY

38.43895654 -84.9632844 Historical data

01098 26-Oct-05 12 mg/kg Lake Mohawk 1.3 miles

upstream of dam near 

Sparta, NJ

41.0176111 -74.6578056 Presumed 

satisfactory

34795 26-Oct-05 12 mg/kg Lake Mohawk 1.3 miles

upstream of dam near 

41.0176111 -74.6578056 Presumed 

satisfactory
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Table 3-6. Summary of All USGS-NWIS and STORET data for Samples Above Concentrations of Concern per Media Type.

a

Sample Type Parameter Code Date of 

Sample

Value

Above

COC

Station Name Latitude Longitude

Data Quality 

Description (USGSNWIS data only)b

samples above COC in last 

3 years

Sparta, NJ

29816 14-Apr-95 26 mg/kg Mohawk River at Cohoes,

NY

42.78535559 -73.7076188 Historical data

29816 14-Apr-95 23 mg/kg Mohawk River at Cohoes, 

NY

42.78535559 -73.7076188 Historical data

29816 17-Sep-96 13 mg/kg St. Lawrence River at

Cornwall Ontario near 

Massena, NY

45.0061599 -74.7949099 Historical data

29816 26-Sep-96 20 mg/kg Rio Grande bl Falcon Dam, 

TX

26.5572768 -99.1683666 Historical data

29816 21-Mar-96 14 mg/kg Rio Grande bl Falcon Dam, 

TX

26.5572768 -99.1683666 Historical data

29816 01-May-96 18 mg/kg Rio Grande at Foster Rh 

near Langtry, TX

29.78075694 -101.7559523 Historical data

34795 19-Dec-05 20 mg/kg ZK-58-27-7 at Avery Deer

Spring, TX

30.5075 -97.7491667 Reviewed and 

accepted

29816 29-May-96 18 mg/kg Rio Grande at El Paso, TX 31.80288488 -06.5408218 Historical data

29816 23-Oct-96 16 mg/kg Rio Grande at El Paso, TX 31.80288488 -06.5408218 Historical data

34795 30-Aug-03 18 mg/kg AF Plant 4 Ofl No. 4 near 

Bomber Road, Fort Worth, 

TX

32.77619444 -97.4535833 Reviewed and 

accepted

Sediment – STORET

Chronic = 11.2 mg/kg (dw)

Acute = 112 mg/kg (dw)

1,222 total sediment

samples;

21-Sept040488.1 mg/kg West/East Creeks, NJ 39.176000 -74.900000 NA

24-Sept040457.2 mg/kg Great Sound, NJ 39.009000 -74.815000 NA

28-Sept040435.8 mg/kg Great Egg Harbor, NJ 39.366000 -74.716000 NA

8-Aug-005 20.5 mg/kg Upper NY/NJ Harbor, NY 40.699000 -74.020000 NA
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Table 3-6. Summary of All USGS-NWIS and STORET data for Samples Above Concentrations of Concern per Media Type.

a

Sample Type Parameter Code Date of 

Sample

Value

Above

COC

Station Name Latitude Longitude

Data Quality 

Description (USGSNWIS data only)b

6 samples above COC for 

sediment (dw ) 

3-Oct-006 13.7 mg/kg Raritan Bay, NJ 40.494000 -74.288000 NA

3-Oct-0606 11.8 mg/kg Raritan River, NJ 40.503000 -74.292000 NA

a

USGS-NWIS dataset collected was filtered using the following selection criteria:

1

st Data selection factor = Site type name (Site_tp_In). All types listed; those in blue bold are the ones selected: Atmosphere; Coastal - 18 water samples; Collector or Ranneytype well; Ditch; Estuary - only sediment samples; Hyporheic-zone well; Lake, Reservoir, Impoundment - 279 water samples; Outfall - 27 water samples; Pavement; Soil hole; 

Spring - 174 water samples; Storm sewer; Stream - 3,151 water samples; Test hole not completed as well; Tunnel, shaft, or mine; Unsaturated zone; Wastewater land 

application; Water-distribution system; Water-use establishment; and Well. 2

nd Data selection factor = Media Name (Medium_nm). All types listed; those in blue bold are the 

ones selected: Animal tissue; Artificial; Bottom material; Core material; Effluent- 1 water sample; Groundwater; Interstitial water; Soil; Surface water - 3,648 water samples; 

Suspended sediment; and Wet deposition. Data selection factor for Water samples: medium_nm = Surface water and Effluent. Data selection factor for Sediment samples: 

Medium Name - Bottom Material, Effluent, Surface water (as reported in mg/kg), Suspended sediment, and wet deposition. Data selection factor for Soil samples: medium_nm 

= Soil.b

The USGS-NWIS dataset contains a field named ‘dqui_nm,’ which is defined as ‘Data Quality Descriptions.’ STORET does not have this field; therefore, NA (Not 

applicable) is denoted in this column. c

1⁄2 detection/reported value. 
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Figure 3-1. Locations of USGS-NWIS and STORET Monitoring Samples with Concentrations Greater Than COCs.
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Figure 3-2. Locations of USGS-NWIS and STORET Monitoring Samples with Concentrations Less Than COCs.
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SUMMARY OF TRI MODELING RESULTS

ATO surface water concentrations were predicted using the E-FAST2 screening-level model of 

water releases reported by selected TRI facilities in 2010. Because TRI does not indicate the 

number of days associated with reported releases, two scenarios were developed (i.e., 

assuming either 24 or 250 days of release) to provide a range of predicted water concentrations 

for comparison with hazard benchmarks identified for aquatic organisms.

The Probabilistic Dilution Model (PDM), a module of E-FAST2 that predicts the number of days a 

stream concentration will exceed a COC value, was used for both release scenarios. The 

estimated 7Q10 concentrations (μg/L) and the predicted days of exceedance of the COC for 

aquatic organisms (as predicted by the PDM model), are shown in Table 3-7. The COC 

exceedance days refers to the total number of release days in a given year that the chronic COC 

would be exceeded using the surface water concentrations predicted using the E-FAST2 model. 
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Table 3-7. Summary of E-FAST2 Results for Facilities Reporting TRI Water Releases. 

Facility name NPDES Code

EFAST Results

(250 days of release)

EFAST Results

(24 days of release)

7Q10 

Concentration

(ppb)

Days of 

Exceedance

7Q10 

Concentration

(ppb)

Days of 

Exceedance

Eastman Kodak Co TN Eastman Co Div, 

Kingsport, TN, 37662 TN0002640 1.15 0 11.99 0 

Guilford East Plant, Kenansville, NC, 28349

NC0002305 62.07 0 674.14 3 

Auriga Polymers Inc.Spartanburg Facility, 

Spartanburg, 29307 SC0002798 2.29 0 23.97 0 

Sabic Innovative Plastics US LLC, Selkirk, 

NY, 12158-0145 NY0007072 0.08 0 0.81 0 

Sabic Innovative Plastics Mt. Vernon, LLC, 

Mount Vernon, IN, 47620 IN0002101 0.02 0 0.25 0 

Sage Automotive Interiors Abbeville Plant, 

Abbeville, SC, 29620

SC0000353 29.86 1 311.55 6 

Performance Fibers Operations Inc.

Salisbury Plant, Salisbury, NC, 28147 NC0004944 2.83 0 30.04 0 
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Table 3-7. Summary of E-FAST2 Results for Facilities Reporting TRI Water Releases. 

Facility name NPDES Code

EFAST Results

(250 days of release)

EFAST Results

(24 days of release)

7Q10 

Concentration

(ppb)

Days of 

Exceedance

7Q10 

Concentration

(ppb)

Days of 

Exceedance

Dupont Teijin Films, Chester, VA, 23836 VA0003077 0.07 0 0.78 0 

Haywood Co, Brownsville, TN, 380121797

TN0041939 0.03 0 0.33 0 

Bayshore Industrial La Porte, TX, 77571b

TX0022799 2.54b NA 25.36b NA

Covalence Adhesives, Franklin, KY, 42134 KY0074659 0.69 0 7.61 0 

General Cable Industries Inc., Marion, IN, 

46953 IN0002372 0.19 0 2.14 0 

Borealis Compounds Inc., Port Murray, NJ, 

07865 NJ0028657 0.09 0 0.96 0 

Cerro Wire LLC, Hartselle, AL 35640 AL0054674 0.08 0 0.92 0 

a

These screening- level estimates are based on a range of days of release, which may not represent actual releases and environmental 

concentrations at these facilities. b

Dilution factor of 1 used as standard practice for sites that discharge into lakes, bays, estuaries and oceans. This facility releases to Galveston Bay.

NPDES = National Pollution Discharge Elimination System NA = Not Applicable
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The modeling results obtained for the TRI facilities evaluated in this assessment indicate

negligible risks for aquatic organisms. No exceedance of the COC was predicted using the 250 

days/yr release scenario; stream concentrations generated by the model were from 2 to 

100,000 times lower than the COCs identified for aquatic organisms. The 24 days/yr release 

scenario also predicted stream concentrations that were well below the acute and chronic 

COCs for aquatic organisms for most sites; however, one exceedance of the acute COC was 

predicted (i.e., predicted stream concentration = 647 μg/L). The predicted stream water 

concentration for another site also exceeded the chronic COC for aquatic species (i.e., 311 

μg/L); however, the PDM only predicted three and six days of exceedance, respectively for 

these sites which is less than the time required to trigger a concern for chronic risk (20 days) 

based on EPA guidance (US EPA 2009). 

UNCERTAINTY AND DATA LIMITATIONS

The primary sources of uncertainty identified in this assessment are related to limitations in the 

available exposure and hazard data, the E-FAST2 model, and the parameters that support them, 

as discussed below. 

Limitations of the Exposure and Release Data

The environmental fate and transport of antimony is complex, and is influenced by site-specific 

conditions. For example, the surface environment is enriched in antimony as a result of natural 

events (e.g., volcanic eruptions, hydrothermal vents, etc.) and various forms can exist (e.g., 

free, complexed to metal ligands, or incorporated in suspended particles), which may affect 

bioavailability to living organisms. In addition, the stability of antimony complexes in aqueous 

environments may be influenced by the acidity, oxygenation and content of the receiving 

water. Because site-specific environmental parameters that can impact bioavailability vary

significantly, it is difficult to extrapolate to other sites or geographic regions within the US. 

The USGS-NWIS database is one of the most robust environmental monitoring databases in the 

US; however, information needed for accurate data interpretation is not always available. In 

some instances, proprietary information may be withheld, or specific details regarding 

analytical techniques may be unclear, or not reported. As a result, there are uncertainties in 

the reported data that may be difficult to quantify with regard to their impact on exposure

estimates. 

The quality of the data provided in the USGS-NWIS and STORET datasets varies, and some of 

the information provided is non-quantitative. While a large number of individual sampling 

results were obtained from these datasets, the monitoring studies used to collect the data were

not specifically designed to evaluate ATO distribution across the US. These data represent a 

variety of discrete locations and time periods; therefore it is unknown whether the data are 

representative of other locations in the US. This limitation does not, however, diminish the 

overall findings reported in this assessment. The data show very few instances (i.e., less than 
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0.01 percent) where measured or predicted antimony levels in the ambient environment 

exceed the identified hazard benchmarks (COCs). 

The TRI database is a comprehensive source of environmental release data for the US; 

however, it has many inherent uncertainties. TRI information is self-reported by facilities (that 

are subject to minimum reporting thresholds) and may use approximations, based on mass 

balances and emission factors, rather than actual emissions or release data. As such, the use of 

TRI data to estimate environmental exposures is constrained by a number of uncertainties 

including: the heterogeneity of processes and releases among facilities grouped within a given 

sector; assumptions made during the identification of facilities using sector definitions

provided in the TRI database; lack of information regarding the distribution of specific 

antimonial compounds reported within the selected TRI category of ‘antimony compounds’; 

and fluctuations in the level of production and associated environmental releases reported 

from year to year. Uncertainty may also arise from omissions in the TRI reporting data, such as 

sectors that are not required to report, facilities that fall below the reporting threshold, or 

facilities for which forms simply are not filed. While these limitations are important, their 

impact on estimating exposure potential may be less than that associated with the conservative 

assumptions that were made regarding environmental releases. ATO is reported in TRI under 

the broader category of ‘antimony compounds’, which covers all chemicals that contain

antimony. As such, EPA expects the actual releases of ATO to be lower than those reported in 

TRI. 

E-FAST2 Model Uncertainties

By definition, models represent simplifications of real world conditions. They cannot include all 

of the parameters necessary to capture the complexity of the natural environment. The major 

limitations associated with use of the E-FAST2 model relate to the assumptions made regarding 

missing information required as model input, including specific information regarding the 

pattern of releases or the type of antimony compounds reflected in reported TRI releases. It is 

important to note however, that these limitations are unlikely to change the conclusions of this 

assessment, because they are based on a series of conservative assumptions that, in general, 

overestimate exposures to ecological organisms. 

Limitations of the Hazard Data 

The laboratory studies used to identify hazard benchmarks (i.e., COCs) for ecological organisms 

varied in terms of the analytical methods used to measure antimony concentrations and the 

form of antimony used to assess toxicity. For example, the aquatic COCs were derived from 

studies using SbCl3, whereas the data used to assess ecological exposures are for ‘antimony 

compounds’. Minimal impacts on risk findings determined for water- and sediment-dwelling 

organisms are expected since both compounds produce comparable amounts of antimony ion 

upon dissolution. The potential risk to soil-dwelling organisms was shown to be low; however, 

this conclusion is drawn from a limited set of data that may not be representative of the US. 
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CONCLUSIONS

The purpose of this assessment was to evaluate the potential ecological risks of concern that 

may be associated with ATO use as a synergist in halogenated flame retardants. To this end, 

hazard benchmarks, or COCs, were compared to the measured antimony concentrations in 

water, soil, and sediment, and to the predicted ATO surface water concentrations based on 

modeled releases reported in the 2010 TRI. Despite the data limitations and uncertainties 

described above, negligible risks of concern are expected for ecological organisms based on the 

following considerations: 

• Use of ‘antimony compounds’ as a surrogate for ATO and modeled exposure estimates 

based on the conservative assumption of total releases (during the 2010 TRI reporting 

cycle) occurring over a 24-day period are likely to overestimate exposure potential. 

• Use of sensitive ecological species to identify the most conservative COCs showed very 

few instances where measured or predicted values exceed the COCs for water-, 

sediment-, or soil-dwelling organisms.

• Measured antimony concentrations from environmental monitoring samples collected 

within the last three years did not exceed any of the calculated COCs.

This assessment provides important insights regarding the potential risks of concern to 

ecological organisms associated with ATO use in halogenated flame retardants. Monitored and 

modeled values of ATO are assumed to represent reasonable estimates of environmental 

exposures.
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http://www.epa.gov/dfe/pubs/projects/decaBDE/deca_fullreport.pdf. Accessed November 7, 2012. 

US EPA (2012b). ECOTOX database. Advances database query. U.S. Environmental Protection Agency. 

http://cfpub.epa.gov/ecotox/advanced_query.htm Accessed August 16, 2012. 

US EPA (2012c). STORET/WQX data warehouse. US Environmental Protection Agency. 

http://www.epa.gov/storet/dw_home.html. Accessed July, 2012. 
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USGS (2004). Antimony. Mineral commodity profiles. US Geological Survey. 

http://pubs.usgs.gov/of/2003/of03-019/of03-019.pdf. Accessed November 7, 2012. Open-File Report 

03-019.

USGS (2006). 2005 Minerals yearbook. Antimony. US Geological Survey. 

http://minerals.usgs.gov/minerals/pubs/commodity/antimony/antimmyb05.pdf. Accessed November 7, 

2012. 

USGS (2011). 2010 Minerals yearbook. Antimony [advanced release]. US Geological Survey. 

http://minerals.usgs.gov/minerals/pubs/commodity/antimony/myb1-2010-antim.pdf. Accessed 

November 7, 2012. 

USGS (2012a). Antimony. Mineral commodity summary. US Geological Survey. 

http://minerals.usgs.gov/minerals/pubs/commodity/antimony/mcs-2012-antim.pdf. Accessed 

November 7, 2012. 

USGS (2012b). Water quality samples for the nation. National Water Information System: Web 

Interface. http://nwis.waterdata.usgs.gov/usa/nwis/qwdata. 

Watt, W. D. (1983). Chronic inhalation toxicity of antimony trioxide: Validation of the threshold limit 

value. Wayne State University, Detroit, Michigan. (as cited in EU RAR, 2008).

Weidenfeller (2005). Final report of the distiness testing of powdery substances (Antimony trioxide)

on behalf of EBRC Consulting Gmbh. GF-no. 00 009 05. (as cited in EU RAR, 2008).

Weil, E., and Levchik, S. (2009). Flame retardants for plastics and textiles: Practical applications. Hanser 

Publications, Munich, Germany.

WHO (2003). Antimony in drinking-water. Background document for development of WHO guidelines 

for Drinking-water Quality. World Health Organization. 

www.who.int/water_sanitation_health/dwq/chemicals/antimony.pdf. Accessed November 2, 2012. 
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Appendix 
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Appendix A: Human Health Hazard Summary 

Toxicokinetics

Precise quantitative information regarding antimony absorption, distribution, and retention in 

humans is lacking; however, increased levels of antimony have been reported in blood and 

urine obtained from workers following ATO inhalation exposure, indicating that trivalent 

antimony may be absorbed from the lungs and excreted in the urine (Bailly et al., 1991). A 

renal elimination half-life of four days was estimated in 21 employees of a starter battery 

manufacturing plant who were exposed to ATO via inhalation(Kentner et al., 1995). 

Systemic absorption following inhalation exposure is mainly influenced by chemical form, 

particle size, and solubility. In general, large particles (≥ 2.5 μm) tend to deposit in the upper 

airway and are cleared more rapidly (via mucociliary transport) than smaller particles that can 

deposit in the lower lung, where clearance times depend more on solubility (i.e., less soluble 

particles will be cleared more slowly) (Brain et al., 1994). 

Antimony may be retained in the lungs for long periods following inhalation exposure. Lung 

retention times measured in seven male workers accidentally exposed to radiolabeled aerosols 

of ATO (125Sb) showed that most of the radiolabeled material was confined to the lungs, with 

negligible amounts detected in other parts of the body. The estimated elimination half-life for 

antimony varied significantly, ranging from 600 to 1,100 days in non-smokers and 1,700 to 

3,700 days in smokers, suggesting that ATO lung clearance may be negatively impacted by 

smoking (Garg et al., 2003). Deceased smelter and refinery workers exposed to ATO primarily 

via inhalation, exhibited elevated lung concentrations when compared to non-occupationally 

exposed individuals (Gerhardsson et al., 1982); however, antimony concentrations measured in 

other organs (e.g., liver and kidney) were comparable, suggesting either a short biological halflife or limited systemic distribution for antimony in these tissues.

Laboratory animal data indicate low systemic absorption of ATO when administered via the oral 

route (Felicetti et al., 1974; De Bie and Salmon-te Rietstap, 2005). Therapeutic use of 

antimonial compounds for the treatment of parasitic diseases has also demonstrated poor 

systemic bioavailability following oral exposure in humans (WHO, 2003). Based on results 

reported by the International Commission on Radiological Protection, limited systemic 

absorption (~1%) may be assumed when estimating ATO uptake from the gastrointestinal tract 

(as cited in EU RAR, 2008); dermal absorption (0.26 %) is negligible (Roper and Stupart, 2006). 

It has been suggested that a portion of systemic absorption observed following inhalation 

exposure is due to the clearance of large particles (via mucociliary transport) and subsequent 

uptake into the gastrointestinal tract (Brain et al., 1994). Using the Multiple Path Particle 

Deposition model and predicted deposition patterns for inhaled ATO particles (4 μm), the total 

systemic absorption (reflecting combined uptake in the lungs and gastrointestinal tract) was 

estimated at approximately 7% (as cited in EU RAR, 2008). 

Once taken up into the systemic circulation, trivalent antimony accumulates in red blood cells 

and is distributed primarily to liver, spleen, and bone (Casals, 1972). It has been suggested that 
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this pattern of distribution may reflect clearance from circulation via phagocytic macrophages 

located in these organs which effectively sequester non-endogenous molecules (Sarin, 2010). 

Acute Toxicity

The available laboratory animal data indicate low acute toxicity via oral, dermal, and inhalation 

routes (as cited in EU RAR, 2008): 

• oral LD50 >20,000 mg/kg-bw (rats)

• dermal LD50 >8,300 mg/kg-bw (rabbits)

• inhalation LC50 (4-hour) >5,200 mg/m3 (rats) 

Irritation

No adverse skin reactions have been reported in laboratory animals; however, workers have 

reported skin irritation following dermal exposure to ATO under conditions of intense heat and 

heavy sweating (NIOSH, 1978; Potkonjak and Pavlovich, 1983). It has been suggested that ATO 

may induce skin rashes (i.e., antimony spots) as a result of physical obstruction of the sweat 

ducts. Lung and eye irritation have also been noted with occupational exposure, but no causal 

relationship has been established. Although ATO is not classified as an irritant under the 

Registration, Evaluation, Authorization and Restriction of Chemicals, workers are encouraged to 

avoid excessive contact via use of personal protective equipment. 

Subchronic Toxicity 

Repeated inhalation exposure has been shown to cause respiratory irritation in rodents (Groth

et al., 1986; Newton et al., 1994; Potkonjak and Vishnjich, 1983). Although detailed 

occupational exposure data are lacking in the US, early case reports of adverse pulmonary 

effects (inflammation, pneumoconiosis, emphysema) and decreased lung function (Potkonjak 

and Vishnjich, 1983) indicate a potential for adverse respiratory effects in humans following 

repeated inhalation exposure. In addition, gastrointestinal disorders (vomiting, diarrhea), 

fatigue, dizziness, and headaches have been reported in workers heavily exposed to smelter 

fumes (NIOSH, 1978). It is important to note however, that working conditions have improved 

significantly over the past 30 years; a permissible exposure limit of 0.5 mg/m3 has been set to 

protect this population.

Carcinogenicity

The International Agency for Research on Cancer (IARC) concluded that “there is sufficient 

evidence for the carcinogenicity of ATO in experimental animals" (IARC, 1989) based on one 

published, and one unpublished report of increased lung tumors in female rats following ATO 

inhalation exposure (Groth et al., 1986; Watt, 1983). Another chronic inhalation study has 

since been published that found no increased cancer incidence following ATO inhalation 

exposure in rats (Newton et al., 1994). 

The proliferation of alveolar macrophages is generally regarded as a normal physiological 

response to the deposition of poorly soluble particulates in the lung; however, in rats 

repeatedly exposed at high levels, macrophage clearance is impaired, resulting in “lung 
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overload”. This condition is characterized by macrophage infiltration, chronic interstitial 

inflammation, metaplasia, and the subsequent development of lung tumors. Although the 

cascade of effects caused by pulmonary overload are unlikely to be relevant for humans, the rat 

is assumed to be an appropriate model for both neoplastic and non-neoplastic responses to 

poorly soluble particulates (Mauderly, 1997). Because the responsiveness of the rat model to

non-genotoxic agents (under conditions of lung overload) is dependent upon chronic active 

inflammation and cell proliferation, no lung cancer hazard is anticipated for humans exposed to 

ATO at lower, environmentally relevant concentrations, where chronic active inflammation and 

cell proliferation are not present (ILSI, 2000). 

 

IARC concluded that “there is inadequate evidence for the carcinogenicity of ATO in humans”

(IARC, 1989). Since this evaluation, two epidemiological studies of increased cancer incidence 

in smelter workers have been published.

A mortality study conducted in 1,014 male workers employed in an antimony smelter plant 

between 1937 and 1971 showed a significant excess in mortality from lung cancer, ischemic 

heart disease and non-malignant respiratory disease; however, the authors acknowledged that 

the observed increase in cancer mortality may be influenced by co-exposure to arsenic (Schnorr

et al., 1995). 

A survey of antimony smelter workers employed before 1961 showed a significant increase in 

lung cancer mortality (12 expected vs. 5.3 observed, p = 0.016), with a minimum latency period 

of approximately 20 years between the first exposure and death from lung cancer (Jones, 

1994). No correlation between the length of employment at the smelter and cancer mortality 

was found. In addition, no excess cancer mortality was found in the cohort recruited after 

1960. This study is limited by the lack of an appropriate control population, and confounding 

factors such as cigarette smoking and co-exposure to polycyclic aromatic hydrocarbons, arsenic, 

and sulfur. As such, the increased cancer mortality observed in the earlier cohort could not be 

attributed to a specific agent. 

While it is clear that ATO inhalation exposure can impair pulmonary clearance in rats (Newton

et al., 1994), it is important to note that animal studies tend to employ significantly higher 

concentrations and longer durations of exposure than would generally be expected for humans. 

Although the available information is limited, there is no evidence of carcinogenicity via the oral 

route (Schroeder et al. 1968; Schroeder et al.,1970). 

Mutagenicity

The available in vitro data for ATO-induced mutagenicity is mixed. ATO was not mutagenic 

when tested in Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537 or 

Escherichia coli WP2P and WP2P uvrA with or without metabolic activation; however, ATO

induced chromosomal aberrations in cultured human leukocytes and lymphocytes (Elliott et al., 

1998). No mutagenic potential was observed in mouse lymphoma cells (Paton and Allison, 

1972), but weak induction levels (~ two-fold above background) were reported in a sister 

chromatid exchange assay using V79 cells in vitro (Kuroda et al., 1991). Conflicting results have 
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also been obtained for ATO-induced mutagenicity in vivo. Mice gavaged with aqueous ATO at 

400, 668, and 1,000 mg/kg-bw/day for up to 21 days were positive for chromosomal 

aberrations, but not clastogenic effects (Gurnani et al., 1992). A mouse micronucleus test 

conducted with ATO showed no clastogenic effects following one high dose (5,000 mg/kg-bw) 

or repeated exposure at 400, 668, or 1,000 mg/kg-bw/day for 7, 14, or 21 days (Elliott et al., 

1998). Negative results were also reported for micronuclei induction in rats following oral 

exposure at 250, 500, or 1,000 mg/kg-bw/day for 21 days (Kirkland et al., 2007). 

Limited evidence of mutagenic potential has been demonstrated for ATO; however, a number 

of technical experts have independently concluded that ATO is unlikely to be mutagenic in vivo

(European Food Safety Authority, 2004; Environment Canada/Health Canada, 2010; Tweats et 

al., 2007a, b). Since a possible local genotoxic effect of ATO would only be relevant under 

exposure conditions that also produce lung overload, minimal concerns are indicated for 

humans(EU RAR, 2008). 

Reproductive Toxicity

A relative paucity of data exists regarding the potential for ATO-induced reproductive or 

developmental effects; however, a weight-of-evidence approach may be used to address these 

endpoints. Toxicokinetic considerations, together with the absence of effects on reproductive 

organs in repeated-dose studies suggest low concern for reproductive effects.

Limited information is available from a Russian report on ATO (Belyaeva, 1967), which indicated 

adverse reproductive effects in rats (e.g., ovarian cysts, uterine metaplasia, decreased fertility) 

following inhalation exposure at 250 mg/m3 for 4 hours/day during a two-month period. These 

study authors also reported adverse reproductive outcomes (spontaneous abortions, 

premature births, gynecologic problems) in women following exposure to metallic dusts (of 

antimony, ATO, and antimony pentasulfide) at unspecified concentrations while working in a 

metallurgical plant. The reported results are largely inconclusive and inadequate for risk 

assessment due to inadequate or missing information regarding study design (e.g., lack of 

information on experimental conditions, controls, and purity of test substance) and exposure 

conditions. 

No testicular effects were observed in male rats or mice following repeated gavage exposure to 

ATO at doses ≥1,000 mg/kg-bw/day (Gurnani et al., 1992; Omura et al., 2002). In addition, oral 

exposure to ATO during a 90-day feeding in rats study showed no effects on male reproductive 

organs up to the highest dose tested (1,686 mg/kg-bw/day; Hext et al., 1999). Gerber et al.

(1982) used a readily soluble, radiolabeled compound, antimony trichloride (

125SbCl3), to 

determine the extent of uptake in pregnant mice following dietary exposure to a mixture of 

antimony chloride and arsenic throughout pregnancy. Minimal absorption (~7 %) was observed 

in treated dams, with limited distribution to reproductive organs (~0.1 to 0.2 % in ovaries and 

uteri). This finding is supported by another prenatal developmental toxicity study, in pregnant 

ewes dosed orally throughout gestation with antimony tartrate (a highly soluble form of 

antimony expected to exhibit higher absorption as compared to ATO) at 2 mg/kg-bw/day 

showed no adverse maternal or developmental effects (James et al., 1966). 
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Developmental Toxicity

In a prenatal developmental toxicity study, female Sprague-Dawley rats (26/dose) were 

exposed to ATO via (nose-only) inhalation at 0, 2.6, 4.4, and 6.3 mg/m3 (mass median 

aerodynamic diameter [MMAD] = 1.59 to 1.82 μm) for 6 hours/day from the day of fertilization 

through day 19 of gestation. Significant increases in lung weights and an accumulation of ATO

in erythrocytes were observed in all treated dams as compared to controls. In addition, 

histological examination revealed an accumulation of pigmented alveolar macrophages, and 

discrete areas of acute inflammation and hyperplasia in the lungs. An increase in postimplantation loss (3.4, 3.6, 3.5, and 7.1 % in the 0, 2.6, 4.4, and 6.3 mg/m3 groups; p = 0.11) was

observed at the highest concentration tested; however, these changes were not statistically 

significant. No developmental effects were reported; the no-observed-adverse-effect 

concentration (NOAEC) for developmental toxicity was determined to be > 6.3 mg/m3

. A 

NOAEC for maternal toxicity could not be established, as increased lung weight was observed at 

all levels of exposure (Schroeder, 2003). 

 

Synopsis

Inhalation of airborne dusts is the primary concern for ATO exposure in occupational settings, 

whereas the general population is primarily exposed to low levels of ATO in food and water.

Chemical speciation and route of exposure are major determinants of antimony toxicity in 

humans. Generally speaking, pentavalent antimony is less toxic than the trivalent species; 

however, most antimony compounds are oxidized to ATO upon release into the environment, 

and the available evidence suggests that over time, further oxidation to the pentavalent form 

may occur under aerobic conditions (EU RAR, 2008). In addition, quantitative studies indicate 

that minimal amounts of ATO are released from flame-retarded consumer products (CPSC, 

2006, 2012; Thomas and Stevens, 2005). 

The general population is exposed mainly via ingestion of food and water, whereas inhalation 

and dermal contact are more common in occupational settings. Irritation at the point of 

contact (e.g., dermatitis, lung inflammation, pneumoconiosis) has been reported in workers 

following chronic inhalation exposure (NIOSH, 1978); however, a permissible exposure limit of 

0.5 mg/m3 has been set to protect this population. ATO produces minimal systemic toxicity 

when administered via oral, dermal, or inhalation routes due to poor systemic absorption, 

which effectively limits bioavailability. Because food and water are the primary sources of 

general population exposure, and the pentavalent (i.e., less toxic) form of antimony 

predominates in these media, significant health risks are not expected at concentrations to 

which individuals may be exposed in the environment (ATSDR, 1992). This conclusion is 

supported by previous risk assessments for ATO in Europe and Canada (EU RAR, 2008; 

Environment Canada/Health Canada, 2010). 
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PREVIOUS ASSESSMENTS

Environment Canada/Health Canada: Screening Assessment for the Challenge – Antimony

Trioxide (Environment Canada/Health Canada, 2010) 

(http://www.ec.gc.ca/ese-ees/9889ABB5-3396-435B-8428-F270074EA2A7/batch9_1309-64-

4_en.pdf) 

In Canada, ATO is listed on the Domestic Substances List and is characterized as “inherently 

toxic to aquatics,” but did not meet the full categorization criteria and was not recommended 

for further assessment. In this assessment, it was concluded: 

“The margins between upper-bounding estimates of exposure to antimony trioxide from 

environmental media (based on antimony) and from use of household items and levels 

associated with effects in experimental animals are considered to be adequately 

protective to account for uncertainties in the health effects and exposure databases. 

On the basis of the adequacy of the margins between conservative estimates of 

exposure to antimony trioxide and critical effect levels in experimental animals, it is 

concluded that antimony trioxide is not entering the environment in a quantity or 

concentration or under conditions that constitute or may constitute a danger in Canada 

to human life or health.”

EU RAR – Diantimony Trioxide (CASRN 1309-64-4) (EU RAR, 2008) 

(http://esis.jrc.ec.europa.eu/doc/risk_assessment/REPORT/datreport415.pdf) 

In Europe, ATO is registered under REACH regulations; the European Commission classifies and 

labels ATO as “H351: suspected of causing cancer by inhalation;” therefore, “a need for limiting 

the risks” was identified for workers.

The assessment of human health and environmental risks concluded:

“Overall results of the risk assessment for surface water, waste water treatment plants, 

terrestrial compartment, atmosphere, secondary poisoning, marine water, marine 

sediment, secondary poisoning in the marine environment: There is at present no need 

for further information and/or testing and no need for risk reduction measures beyond 

those which are being applied already.”

OECD Assessment for Antimony Trioxide (OECD, 2008) 

(http://webnet.oecd.org/Hpv/UI/handler.axd?id=13e93c97-6605-4eac-961f-8af23cc6ad32) 

Environment:

“This chemical is currently of low priority for further work.”
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Human Health:

“Despite the poor quality of the available acute oral and dermal toxicity studies with 

diantimony trioxide in laboratory animals, diantimony trioxide is considered to be of low 

acute inhalation, oral and dermal toxicity. The chemical possesses properties indicating 

a hazard for human health (skin irritation, lung toxicity and lung carcinogenicity after 

repeated exposure). Member countries are invited to perform an exposure assessment 

for workers and if then indicated, a risk assessment. As all studies on chronic 

toxicity/carcinogenicity deviate from the OECD guideline...and because of other critical 

shortcomings in the data set on chronic toxicity/carcinogenicity, the US NTP (National 

Toxicology Program) has initiated 2-year inhalation toxicology and carcinogenicity 

studies on diantimony trioxide in rats and mice.”

(http://ntp.niehs.nih.gov/?objectid=BCD52E6A-123F-7908-7BD5298A5D912AF9)

Antimony in Drinking Water: Background Document for Development of World Health 

Organization (WHO) Guidelines for Drinking-water Quality (WHO, 2003)

(http://www.who.int/water_sanitation_health/dwq/chemicals/antimony.pdf) 

“The WHO guideline for antimony in drinking water was quadrupled from 5 ppb to 

20 ppb in 2003 after the incorporation of information obtained from an updated 

literature review.”