tiered to allow some decisions to be made with limited data, and should include analysis of the 
uncertainties in estimated risks. 
Goals 
The general goal of this work is to develop scientifically-defensible methods for better describing 
the risks of toxic chemicals to aquatic and aquatic-dependent populations and communities, in 
support of improving criteria procedures needed to satisfy GPRA Goal 2, Objective 2. The work 
to be discussed here represents only part of the ecological toxicology efforts within NHEERL 
and is focused on prospective assessments of chemicals for which WQC exist or are desired. As 
such, the proposed research will not address issues which are not closely related to such 
assessments and/or are a subject of research under other goals. This includes such areas as 
chemicals and endpoints of emerging or potential concern, biological indicators (including DNA 
or protein-based probes) for retrospective assessments and diagnostics, and basic investigations 
of the cellular/subcellular and physiological mechanisms of toxicological responses. 
Further details on research needs and NHEERL research efforts to address those needs are 
described in the following subsections. Specific goals of these efforts are summarized in the 
following APGs and APMs Note: some APGs and APMs (including those under GPRA) were 
established before this document was written. They are listed here along with APGs and APMs 
that were developed under the aquatic stressors process. 
APG 1 FY02 (GPRA #31) Provide a method for setting risk-based aquatic life criteria for toxic 
chemicals which minimizes uncertainties of translating national and site-specific water quality 
criteria. 
APM 1A FY02 (GRPA # 167) Report on integrated water and sediment quality criteria 
methods for assessing site-specific risks of persistent bioaccumulative toxicants to 
aquatic species (MED). 
APG 2 FY03 Demonstrate methods to set risk-based water quality criteria for toxic substances. 
APM 2A FY03 Describe a framework for WQC for nonbioaccumulative chemicals that 
more fully describes risk to aquatic organisms (MED). 
APG 3 FY05 (GPRA #111) Provide methods for developing WQC based on characterization of 
population-level risks of toxic chemicals to aquatic life and aquatic-dependent wildlife. 
APM 3A FY04 (GPRA # 59) Population models that project the relative risks of multiple 
stressors (toxic chemicals, habitat alterations) to piscivorous birds (AED, MED). 
APG 4 FY06 Provide methods for extrapolating chemical toxicity data across exposure 
conditions and across endpoints, life stages, and species, which can support assessment of risks 
to aquatic life and aquatic-dependent wildlife for chemicals with limited data. 
78 
