1985, 1987; Tilghman Hall and Oris 1991; Buckler et al. 1994), but use of this research to assess 
risk in natural systems is limited by the factors discussed above. 
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. To this end, PAH accumulation in ELS 
fish will be evaluated both in the laboratory and in natural systems; effects of accumulated PAH 
in ELS fish 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. This project will not 
address the incor|X)ration of effects on ELS fish into fish population models, but will provide 
information important to population-level assessment methods such as those developed in 
projects B1 and B3 and also will examine the correlation of expected ELS effects with fish 
community health indices. Extensions of this work to general PBT assessments will be 
addressed in project B1. 
Scientific Approach 
Assessing the risks of PAHs to ELS fish 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 fish behavior and environmental conditions. Third, the accumulation of PAHs must 
be estimated as a function of fish age and environmental exposure concentrations, including 
consideration of maternal transfer, uptake by both egg and fty, multiple routes of exposure, and 
age-dependent metabolism. Fourth, good dosimetry relationships are needed which link 
mortality and growth to PAH accumulation in the fish, to the varying levels of UV radiation they 
receive, and to their age. Fifth, the combined effects of complex mbctures 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 ELS fish in 
selected natural systems. 
1. ELS Accumulation of PAHs. 
Meaningful assessment of the effects of PAHs (and other PBTs) on ELS fish requires that 
toxicity test results be applied with consideration of the importance of PAH accumulation to 
organism response and how accumulation might differ from that in natural systems. Such 
consideration should include not only accumulation after hatch from water and food, but also 
uptake from water during egg incubation and transfer from the maternal fish to the egg. The 
importance of these different routes of exposure depends on how rapidly PAHs accumulate 
during different life stages and at what life stages UV exposure is most important. Laboratory 
experiments will examine the accumulation of PAHs in ELS fish as a ftmction of when exposure 
starts (parent fish, egg, newly hatched fty) to determine if PAHs originating from parents or 
taken up by eggs might significantly contribute to risks. Uptake relationships will be monitored 
as fish grow to determine at what age and to what extent metabolic transformation of PAHs 
becomes important for regulating accumulation. Accumulation also will be measured fiom ELS 
fish collected from and exposed in natural systems to determine its relationship to environmental 
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