EPA’s Clarifying Questions on ATO peer panel’s draft recommendations
Issue 1. Characterization of Environmental Exposures Based on Release Data.
The draft peer review report suggests that a more thorough investigation of state databases may
provide additional exposure data; however, the EPA STORET database is predicated on existing
state data which suffer from the same problems the peer reviewers identified for the USGS data.
Please provide additional clarification on how this approach would strengthen the current
assessment and if there are any state databases that reviewers believe are different from
sources used in STORET.
A number of commenters suggested that EPA use other data such as the Targeted National
Sewage Sludge Survey and various monitoring data from states and local jurisdictions. We will
review all of the suggested sources for exposure/release data; however, most of the sources EPA
examined for the ATO assessment, including the ones mentioned in the draft peer review report,
contain information on elemental antimony which includes antimony metal and all other
antimony-containing compounds.
In terms of the volume used, antimony in ATO accounts for a relatively small fraction of
the total amount of antimony used within the broader category of “antimony and related
compounds”. Given this, can you please provide specific suggestions and/or approaches
for how EPA may use data from the broader category to estimate ATO releases
associated with its use as a synergist in halogenated flame retardants?
If there are sources other than TRI that contain sufficient information on ATO or
antimony compounds for EPA to adequately characterize ATO releases and/or
concentrations in the environment, could you please provide this information?
If there are additional sources for exposure data that would facilitate a more focused
characterization of ATO releases to (or concentrations in) environmental media, please
provide the necessary data and/or citations.
Issue 2. Characterization of Environmental Exposures Based on Monitoring Data.
Dr. Sepulveda
“… A literature search for the last 5 years identified several published articles reporting
environmental concentrations (including biota concentrations) of Sb.”
Please provide the necessary citations for further revision of the ATO draft assessment.
Issue 3. Fate, Transport and Bioavailability.
Dr. Fairbrother
“…, log-log relationships between antimony in soil and biota samples had slopes less than unity
which, according to Gá l and collaborators (2007), implied that biota–soil accumulation factors
are greater when antimony levels in soils are lower. “
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Please provide additional references to support the assertion that the BCF/BAF decreases
with increasing antimony concentration.
Dr. Hope
“… Fugacity models can be formulated to take availability into account through their definition
of the fugacity capacities or Z values of the chemical in media such as water. The Z-value can
contain terms for the dissolved and non-dissolved fractions. A corresponding procedure is
adopted in the "aquivalence" models which are used for non-volatile chemicals such as metal
ions. There Z’ is the aquivalence capacity, which depends on the characteristics of the chemical,
the medium, and temperature. The aquivalence value of water (Z’W) is defined as 1.0 and the
values for other media are obtained by multiplying Z’W by partition coefficients of particular
medium. The 1992 literature cited is not the latest with respect to aquivalence models.”
Given the inherent variability in the aforementioned parameters, it is unclear how this
information could be used to strengthen the current assessment. Please provide specific
references to support the use of aquivalence models and explain how this information
would inform hazard characterization.
Issue 4. Environmental Hazard Assessment
1) Several panel members questioned why certain data were used for the ATO risk assessment
whereas other information (discovered using additional databases to identify ecotoxicity
information) was omitted.
In order to identify additional ecotoxicity data that are acceptable for hazard
characterization and adequately describe antimony toxicity to aquatic (i.e., fish,
invertebrate, plant) and sediment organisms, please provide specific references for any
new studies that satisfy the stated requirements for test criteria, as outlined in the
guideline documents mentioned in the draft ATO assessment.
2) Some panel members alluded to evidence of increased toxicity to ecological organisms
following exposure to trivalent (versus pentavalent) forms of antimony.
The studies cited in Skeaff et al (2012) relate to human health hazards. Please provide
specific references to support the assertion of increased toxicity to aquatic (i.e., fish,
invertebrate, plant) and sediment organisms from exposures to trivalent (versus
pentavalent) forms of antimony.
3) Several panel members questioned EPA’s decision not to assess terrestrial hazards. OPPT
reviewed the information provided in the U.S. EPA Ecological Soil Screening Levels for
Antimony document provided by the Office of Solid Waste and Emergency Response and
reached the same conclusions regarding the avian, mammalian, and plant hazard data (i.e., that
the available information is insufficient to characterize hazards for these groups based on a
failure to satisfy the identified selection criteria used to determine adequacy for risk assessment).
The Eco-SSL document states the following regarding the available data for terrestrial plant,
avian, and mammalian toxicity data:
“Eco-SSL values for antimony could not be derived for plants or avian wildlife. For these
receptor groups, data were insufficient to derive soil screening values.”
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The same toxicity data provided for soil invertebrates in the Eco-SSL was also used in the
current TSCA Workplan assessment.
Please provide the necessary data and/or citations for any additional toxicity studies that
EPA could use to fill the data gaps identified for antimony toxicity to terrestrial plant,
mammalian or avian species so that these may be evaluated against our selection criteria.
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