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Improving ecological risk assessment of persistent, bioaccumulative, and toxic (PBT) chemicals by using an integrated modeling system - An example assessing chloroparaffins in riverine environments.
Citation:
Barber, Craig AND Kate Sullivan. Improving ecological risk assessment of persistent, bioaccumulative, and toxic (PBT) chemicals by using an integrated modeling system - An example assessing chloroparaffins in riverine environments. Presented at 2015 ICCA-LRI Workshop, New Orleans, LA, June 16 - 17, 2015.
Impact/Purpose:
Poster presented at 2015 ICCA-LRI Workshop.
Description:
Chemical risk assessment (CRA) is primarily carried out at the screening level relying on empirical relationships between chemical properties and tested toxicity effects. Ultimately, risk to aquatic ecosystems is strongly dependent on actual exposure, which depends on chemical properties, loading and environmental characteristics which can mitigate or magnify the transport and fate of chemicals in the environment. It is widely recognized that chemical risk assessments for ecological endpoints would be much improved by realistic exposure estimates. As summarized in ISES (2011), "no exposure, no risk-period". Chemicals submitted for pre-registration review to EPA under the Toxic SubstancesControl Act (TSCA) often lack data regarding their basic properties, environmental or biological concentrations, or toxicity tests. More data for any or all of these important factors would undoubtedly improve understanding of potential risks, but acquiring laboratory and field data is often considered impractical or prohibitively expensive. This is especially true for low solubility chemicals that are likely to be persistent, bioaccumulative, and toxic (PBT) given the methodological challenges to measuring them with standard techniques. Models can help fill data gaps but may suffer from the same limitations as data-based methods.One approach to improving ecological chemical risk assessment is to apply process models to assess exposure. EPA has used models to predict chemical properties (e.g. EpisuiteTM), environmental concentrations (e.g. EXAMS), and biological accumulation (e.g. KABAM, BASS) in CRA. Here we use these models to demonstrate an exposure assessment of a low solubility organic chemical introduced to riverine environments. Integrating the modeling tools can improve on existing screening approaches by providing an integrated, structured, and repeatable process for assessing multiple chemicals, multiple environments, and/or multiple species.For this example, medium chain chloroparaffins (MCCPs) were introduced to and analyzed in 4 riverine ecosystems distributed throughout the United States at loading rates associated with manufacturing facilities. Modeled environmental and biological concentrations results were consistent with European chemical risk assessments (ECHA 2005, 2008), and confirmed that this family of congeners were persistent, bioaccumulative, and produced body burdens associated with narcosis. Not surprising was the importance of loading volumes. However, potential effects also varied due to environmental conditions and fish communities. The ability to characterize environmental and biological variability provides a pathway to both better understand sources of uncertainty and to evaluate control mechanisms. The integrated modeling system operates in a reasonably "high throughput" computational environment allowing rapid consideration of hundreds of environmental scenarios and chemicals.
