Overview of Antimony Trioxide
(ATO) Workplan Risk Assessment
Antimony Trioxide (ATO)
Metal
CASRN 1309-64-4
Sharon Oxendine
Office of Pollution Prevention and Toxics
Oxide
November 13, 2013
Presentation Overview
This presentation will provide:
 Background on ATO
 Key science issues
Please comment on the clarity, strengths and weaknesses of the
assessment and how it specifically may be improved.
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Basis for Selection
* Exposure
- 23,000 metric tons imported in 2012
- widespread use in consumer products
* Human Health Effects
- inhalation toxicity
- possible carcinogen
*
Environmental Releases
- persistence
- bioaccumulation
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Scope of the Assessment
× Human health risks were not the focus of this assessment
 Evaluated ecological risks associated with ATO use in
halogenated flame retardants
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ATO
Antimony Compounds
Conceptual Model for ATO Risk Assessment
focuses on ecological risks resulting from
industrial releases to water
Chemistry, Fate and Transport
 Please comment on the use of chemistry, fate and transport
information to evaluate bioavailability in environmental media.
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Hazard Characterization
 Please comment on the use of toxicity data for
antimony trichloride to characterize aquatic toxicity.
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Criteria for Selection of TRI Facilities
 NAICS codes
 Reported water releases
 Availability of “7Q10” streamflow data
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Monitoring: USGS-NWIS & EPA STORET
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Monitoring Data:
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Can we generalize from this data to other regions?
 Please comment on the use of these data sets to characterize
ecological exposures. Do they adequately reflect conditions at other
locations in the US?
 Are there other major sources of environmental monitoring data
(or other pertinent information) that EPA should consider in the
exposure assessment? If so, please provide the necessary citations
and/or data for inclusion in the revised document.
 Are there concerns or limitations in these data sets that may impact
their utility for risk assessment?
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Use of the category ‘antimony compounds’ as a surrogate to
estimate ATO releases
 Are there other data sources and/or approaches that EPA should
consider for estimating environmental releases? If so, please
provide citations or data for consideration in further revision of the
draft assessment.
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Exposure and Fate Assessment Screening Tool (Version 2)
model estimates of surface water concentrations
 Two release scenarios (assuming total yearly TRI releases occurred
over a period of 24- or 250 days/year) were used to provide a range
of predicted water concentrations for comparison with hazard
benchmarks (concentrations of concern). Please comment on the
EFAST2 modeling approach used to assess aquatic risks.
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Risk Quotient Approach
RQ =
Environmental Concentration
COC
 Environmental concentrations reflect measured or estimated values
 COCs were calculated from the most sensitive effect levels
 Risks indicated when the environmental concentration exceeds COC
(i.e., RQ > 1)
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Validity of Assumptions
 Please comment on the implicit assumption that antimony levels
measured in environmental media reflect inputs from various types
of antimony compounds and end use applications and how this
could impact risk estimates.
 Findings reported in this assessment are thought to represent
conservative estimates of risk. Please comment on the validity of
this statement and the likelihood that actual risks have been over
(or under) estimated.
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Risk Summary
Media
Type
Organism
Endpoint
COC
Monitoring
Data
Modeled
Data
C. viridissima
96-hour LC50 = 1.77 mg/L
354 ppb (acute)
No exceedance
One exceedance
P. Promelas
30-day GMATC = 1.62 mg/L
162 ppb (chronic)
~ 0.2% above
chronic COC
No
exceedances
112 mg Sb/kg dw
(acute)
No exceedances
-
11.2 mg Sb/kg dw
(chronic)
~ 0.7% above
chronic COC
-
Water
Sediment
L. variegatus
28-d NOEC = 112 mg Sb/kg dw
or C. riparius
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Monitoring Results
Selected TRI facilities ( ) are
shown as a point of reference
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Conclusion
Minimal risks are expected for ecological organisms:
The available environmental monitoring data reflect input from
various sources and types of antimony compounds.

 Use of ‘antimony compounds’ as a surrogate for ATO and model
estimates based on the assumption of yearly TRI releases occurring over
a 24-day period provide conservative estimates of exposure potential.
 Use of highly sensitive ecological species showed few instances
where measured or predicted concentrations in environmental media
exceeded the COC for water-, or sediment-dwelling organisms.
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Uncertainty and Data Limitations
Risk findings are constrained by a number of uncertainties regarding
data quality (e.g., adequacy of TRI reporting, model assumptions, and
environmental monitoring data).
Environmental fate and transport are influenced by site-specific
conditions that can impact bioavailability. Since these parameters vary,
it is difficult to extrapolate to other geographic regions within the US.
There is little or no overlap between the geographic locations of
selected TRI facilities and the available monitoring data, therefore a
direct linkage to ATO use as a flame retardant synergist is not possible.
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Key Technical Issues Raised in Public Comments
• Exposure
- Use of conservative assumptions in exposure assessment
- Rationale for selection of end-use scenario
• Hazard
- Lack of transparency in hazard characterization
- Unclear criteria for study selection
• Risk
- Risk quotient versus margin of exposure
- Use of phrases such as “minimal concern”
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Acknowledgements
Kay Austin
Jay Jon
Stanley Barone
Sharon Oxendine
Cathy Fehrenbacher
Wen-Hsiung Lee
Nhan Nguyen
Tim Lehman
Louis Scarano
Sara Pollack
Christina Cinalli
Emma Lavoie
Rick Fehir
Kirsten Hesla
Contract Support
Portions of this document were developed with support
from SRC, Eastern Research Group and Versar.
Office of Chemical Safety and Pollution
Prevention
Office
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Thank you!
Aquatic Toxicity Data
Test Organism
Species
Endpoint
Antimony
Compound
SbCl3
SbCl3
Fish
Aquatic invertebrate
Pagrus major
Chlorohydra viridissima
96-hour LC50
96-hour LC50
Aquatic plant
Pseudokirchneriella
subcapitata
72-hour LC50
(growth rate)
SbCl3
Aquatic plant
P. subcapitata
72-hour LC50
(growth rate)
Sb2O3
Fish
Pimephales promelas
30-day (growth)
SbCl3
Fish
P. promelas
30-day (growth)
Sb2O3
Aquatic invertebrate
Daphnia magna
21-day
(reproduction)
SbCl3
Value
Reference
6.9 mg Sb/L
1.77 mg Sb/L
Takayanagi (2001)
TAI (1990)
EC50 > 36.6 mg/L
NOEC = 2.11 mg Sb/L
LOEC of 4.00 mg Sb/L
GMATC = 2.91 mg Sb/L
NOEC = 0.396 mg Sb/L
LOEC = 1.32 mg Sb/L
GMATC = 0.723 mg Sb/L
NOEC = 1.13 mg Sb/L
LOEC = 2.31 mg Sb/L
GMATC = 1.62 mg Sb/L
NOEC >0.0075mg /L
Heijerick and
Vangheluwe
(2004)
LISEC (2001)
Kimball (1978)
LeBlanc and Dean
(1984)
NOEC = 1.74 mg Sb/L Heijerick and
LOEC = 3.13 mg Sb/L Vangheluwe
GMATC = 2.33 mg Sb/L (2003b)a)
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Sediment Toxicity Data
Test Organism
Species
Antimony
Compound
Endpoint
Value
Reference
Amphipod
Hyalella azteca
Survival/growth/
reproduction
SbCl3
NOEC = 87 mg Sb/kg ww Heijerick and
(124 mg Sb/kg dw)
Vangheluwe
(2003a)
Oligochaete
Lumbriculus
variegatus
Survival/growth/
reproduction
SbCl3
NOEC = 78 mg Sb/kg ww Heijerick and
(112 mg Sb/kg dw)
Vangheluwe
(2005a)
Midge larvae
Chironomus
riparius
Survival/growth/
reproduction
SbCl3
NOEC = 78 mg Sb/kg ww Heijerick and
(112 mg Sb/kg dw)
Vangheluwe
(2005b)
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Soil Toxicity Data
Test Organism
Species
Endpoint
Antimony
Compound
Springtail
Folsomia candida Reproduction
Sb2O3
Earthworm
Eisenia fetida
Adult survival/
Sb2(SO4)3
juvenile production
Enchytraeid
Enchytraeus
crypticus
Adult survival/
Sb2(SO4)3
juvenile production
Springtail
F. candida
Adult survival/
Sb2(SO4)3
juvenile production
Value
NOECreproduction =
999 mg Sb/kg dw
LOECreproduction=
2,930 mg Sb/kg dw
NOEC/LOEC adult survival =
617/697 mg Sb/kg
NOEC/LOEC juvenile production
=
60/86 mg Sb/kg
NOEC/LOEC adult survival =
384/538 mg Sb/kg
NOEC/LOEC juvenile production
= 100/140 mg Sb/kg
NOEC/LOEC adult survival =
100/126 mg Sb/kg
NOEC/LOEC juvenile production
= 100 /126 mg/kg
Reference
Moser (2007)
Simini et al. (2002)
Kuperman et al.
(2002)
Phillips et al. (2002)
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U.S. Geological Survey Open-File Report
http://mrdata.usgs.gov/geochem/doc/home.htm
USGS National Stream Quality Accounting Network (1996-2000)
http://pubs.usgs.gov/wri/wri014255/results/detect/pd01095.png
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ANTIMONY STATISTICS1
(Metric tons of antimony content)
United States:
Mine production
Smelter production:
Primary
Secondary
Exports:
Metal, alloys, waste and scrap
(gross weight)
2
Antimony oxide
Imports for consumption
Reported industrial consumption, primary antimony
Price, average3
(cents per pound)
Global mine production
2008
--
2009
--
2010
--
2011
--
2012
--
W
3,180
W
3,020
W
3,520
W
3,230
W
3,730
366
1,830
29,000
8,140
279.5
185,000r
385
1,710
20,200
6,770
235.6
154,000
427
2,120
26,200
8,860
401.2
178,000r
581
3,590
23,500
10,200
650.3
183,000r
847
3,870
22,600
10200
564.5
174,000e
e Estimated. r Revised.
W Withheld to avoid disclosing company proprietary data, -- Zero.
are rounded to no more than three significant digits, except prices.
2Antimony content data were calculated by the U.S. Geological Survey.
3New York dealer price for 99.5% to 99.6% metal, cost, insurance, freight U.S. ports.
(USGS, 2012)
1Data
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