to measures of biological condition being collected for each site by GLEI staff to evaluate 
measured photo-activated PAH potency as an ecological indicator. 
Products 
FY03 Journal article on bioaccumulation of PAHs in ELS fish. 
FY04 Journal article on dosimetry of photoactivated PAH toxicity to ELS fish. 
FY05 Journal article on effects of complex PAH mixtures and ambient sunlight to ELS fish in 
natural systems. 
APM 5 A FY05 Report regarding assessment of risks to aquatic organisms from combined 
exposure to PAH mixtures and UV light in natural systems (MED). 
Benefits of Products 
Research to date has indicated that current PAH risk assessments do not adequately handle such 
issues as photo-activated toxicity, incompletely-characterized complex mixtures, and ELS 
exposure issues, so that risk might be greatly underestimated. However, there has been no direct 
evidence that risk is significant for the combinations of PAH contamination, UV light, and 
biological receptors in natural systems. 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 WQC and sediment guidelines for PAHs, as 
well as hazard assessments for other classes of PBTs which might require similar considerations. 
This work will also help improve general PBT exposure assessment methodolo^es, such as fish 
ELS accumulation models. 
Gap Analysis 
The overall goal of this research program is to develop procedures for risk-based criteria for toxic 
chemicals. The Critical Path subsection described the research needed to better describe the risks 
of toxic chemicals to aquatic life and aquatic-dependent wildlife populations and communities. 
The proposed research projects address these needs. Although the research program will expand 
and improve the approaches for developing criteria, this gap analysis reviews the needs (e.g., 
models, test meth^s, toxicity data, methods for assessing temporal and spatial distributions of 
exposure, and role of life history on species vulnerability) that will not be completely addressed 
by this program, but are required for development of a complete risk assessment capability for 
toxic chemicals. 
Developing the scientific basis for risk-based criteria will require the overall conceptual 
framework and better modeling tools described in the research projects outlined above. While 
the focus of this research program is on the development of methods and models, there will be 
parameters required by these methods and models that can not be met adequately with existing 
data sources alone. New data will be generated for specific questions in a couple of our 
demonstration projects; however, a major gap for achieving our overall goal of developing risk- 
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