Impact/Purpose:

The risks of polyaromatic hydrocarbons (PAHs) to fish and other aquatic organisms in natural systems is highly uncertain due to the occurrence of complex, incompletely-characterized mixtures of these chemicals, large spatial heterogeneity in exposure concentrations, incomplete understanding of the importance of UV-activated PAH toxicity, the biological and physical controls on fish exposure to UV light, and the bioaccumulation of PAHs. These uncertainties are especially great for early-life-stage fish, which might be particularly susceptible to UV-activated because of their small size, lack of protective pigmentation and gill coverings, and ready accumulation of PAHs. The overall objective of this research project is to develop more comprehensive and accurate assessments of the risks of PAHs to early-life-stages of fish that address the influence of UV radiation and exposure relationships in natural systems. Zooplankton are also being considered as some species inhabit the open water column where UV exposure is high. This work will determine whether there should be concern regarding such toxicity for fish populations in PAH-contaminated areas. If this is the case, this would greatly impact the development of water quality criteria and sediment guidelines for PAHs. This work will also help improve general PBT exposure assessment methodologies.

Description:

Assessing the risks of PAHs to aquatic organisms requires consideration of several factors. First, environmental PAH concentrations must be characterized, including chemical partitioning information important to bioavailability. Second, UV radiation exposures must be evaluated relative to organism behavior and environmental conditions. Third, the accumulation of PAHs must be estimated as a function of organism physiology, development, and environmental exposure concentrations, including consideration of maternal transfer, uptake by egg and early life stages, multiple routes of exposure, and age-dependent metabolism. Fourth, good dosimetry relationships are needed which link mortality and growth to PAH accumulation, to the varying levels of UV radiation they receive, and to age-specific sensitivity. Fifth, the combined effects of complex mixtures of PAH must be evaluated, including the effects of those PAHs which are not measured. This project will develop needed capabilities in these areas and will assess the likely risk of PAHs to early life stage fish and other aquatic organisms in selected natural systems. PAH accumulation in ELS fish and zooplankton will be evaluated both in the laboratory and in natural systems; effects of accumulated PAH will be evaluated both under laboratory UV light and natural sunlight for both individual PAHs and PAH mixtures from contaminated systems; and likely risks based on these observed effects and on fish habits will be estimated for natural systems.

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