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Health and Environmental Effects Research

Toxic Chemicals

Procedures for deriving aquatic life water quality criteria have existed for many years and have been useful for managing toxic chemical inputs to aquatic systems. However, these procedures are based on simplifying assumptions and a relatively narrow framework that limit their use in fully assessing the risk of a wide range of toxic chemicals to both aquatic life and aquatic-dependent wildlife. Recent advances in the science regarding the toxicity and bioaccumulation of toxic chemicals need to be incorporated as improvements or used to develop new water quality criteria.

The general goal of EPA's research in this area is to develop scientifically defensible methods for better describing the risks toxic chemicals pose to aquatic life and aquatic-dependent wildlife. Specific projects in EPA's plan for toxic chemicals research include the following:

View information about the Implementation Plan for Toxic Chemicals Research within the Aquatic Stressors PDF file. (PDF, 197 pp, 3.21 MB, About PDF).


Oil on a beach

Crude oil on a beach.

Risk-characterization Methods For Nonbioaccumulative Toxicants

The goal of this project is to update the guidelines used to develop water quality criteria for nonbioaccumulative toxicants so that aquatic life can be more adequately protected. An important component of this project is the review and formulation of models that are used to describe the relationship between the level and duration of exposure to a toxicant and the effects this exposure induces in aquatic organisms. The ability of models to predict the effects of variable exposure times and exposure conditions will be evaluated using standard toxicity tests.

Extrapolation Methods For Limited Data Sets

The use of predictive models is essential in performing probability-based ecological risk assessments; this is especially true for endangered species that cannot be studied in the same manner as other species and for species about which data is sparse. To meet this challenge, research is planned to evaluate the utility of using surrogate species to estimate the effects of toxic chemicals and to develop models that will facilitate extrapolation from one species or taxonomic group to another. Additional effort will focus on improving acute-to-chronic endpoint models so that assessors can better predict chronic toxicity to endangered and other species on a population basis.

Risks Of Heavy Metals Exposure Through Multiple Routes

A shortcoming in current assessments of the risk of exposure to metals in aquatic systems is an incomplete understanding of the importance of multiple exposure routes. Conventional wisdom holds that water is the most significant source of exposure; however, recent studies suggest that dietary exposure to metals could be important especially in areas where metal concentrations in the water column are low but are high in the food chain due to past contamination of sediments. Plans to address this knowledge gap will include a review and synthesis of past and ongoing work of other researchers and a series of experiments to assess how juvenile fish and other organisms are affected by exposure to metals their diet and the sediment.

Risk-based Criteria For Persistent Bioaccumulative Toxicants

Research in under this topic will describe and demonstrate a framework that will facilitate a more accurate determination of where and to what extent loadings of persistent bioaccumulative toxicants (PBTs) pose unacceptable ecological risks to aquatic ecosystems. Three major groups of PBTs will be addressed: halogenated organics, polycyclic aromatic hydrocarbons (PAHs), and organometallic compounds. The result of this research will be a scientific basis for the setting of risk-based water quality criteria to protect fish and wildlife populations from the effects of bioaccumulative toxicants.


Fish-eating Birds

Multiple Stressor Risks To Fish-eating Bird Populations

This project will examine existing methods and design new approaches for evaluating the risks that multiple stressors pose to aquatic dependent wildlife. Through a demonstration project that focuses on a multi-tiered assessment of the risks of the exposure of fish-eating birds posed by exposure to PBTs, e.g., mercury in fish, this work will produce the groundwork necessary to develop risk-based criteria. A variety of research is planned, including work to characterize the spatial and temporal distribution of stressors within a given landscape, development of stressor-response relationships for endpoints such as survival and fecundity, and an exploration of ways to extrapolate between species and to take population dynamics and life-stages into account.

Toxic Effects Of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are important contaminants of aquatic systems, but the risks they pose are poorly characterized because PAHs exist as complex mixtures and their toxicity can be greatly increased in the presence of UV radiation. To assess this risk, four factors must be taken into account: (1) photoactivated toxicity; (2) complicated bioaccumulation relationships; (3) the combined toxicity of multiple chemicals; and (4) spatial variation in the distributions of UV radiation, PAHs, and the potentially affected organisms. This project involves a series of laboratory and field experiments aimed at establishing methods and collecting data to support a model-based assessment of the risks posed by PAHs with a special focus on risks to fish in their early stages of development.

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