Monday, March 9, 2009

EPA Pesticide Aquatic Life Benchmarks - Water Quality Criteria Comparison

Two Offices within US EPA derive “standards” for pesticides to protect aquatic life. However, the methods used to derive these “standards” are quite different, as are the intended uses for the information.

Aquatic life benchmarks are derived by Office of Pesticide Programs (OPP) to assist in performing its responsibilities to regulate pesticides used in the US. OPP aquatic life benchmarks are determined based on toxicity data reviewed by the Agency during its most recent risk assessment as part of the pesticide registration process. OPP relies on studies required under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) as well as laboratory and field studies available in the public scientific literature to assess environmental risk. Aquatic life benchmarks represent the most sensitive toxicity endpoint for a given aquatic organism using all scientifically acceptable toxicity data available to EPA. OPP then uses these aquatic benchmarks in risk assessments developed for pesticides. The benchmarks can be helpful in interpreting monitoring data, and to identify and prioritize sites and pesticides that may require further investigation.

[Read more about other types of "benchmarks" used by EPA and States in NPDES permits]

The US EPA Office of Water (OW) has the responsibility for evaluating aquatic toxicity data to assess the ecological effects of chemicals in surface water. The OW uses aquatic toxicity data to develop national ambient water quality criteria that can then be adopted by States and tribes to establish water quality standards under the Clean Water Act (CWA). These standards are used to determine if individual water bodies meet their intended uses, and in setting NPDES permit discharge limits. Ambient Water Quality Criteria are derived for a wide range of chemicals, which include certain chemicals which are registered by OPP under FIFRA.

In contrast to OPP benchmarks, ambient water quality criteria derived by OW are based on a statistical evaluation of the available toxicity data. This approach derives a concentration to protect the integrity of the aquatic community rather than selecting a concentration that is protective of the single most sensitive organism.

OPP and OW are currently working together to harmonize the scientific approaches that now underlie both programs. A harmonized approach is expected to result in consistent tools and approaches to use in ensuring the protection of aquatic ecosystems.

Caltha LLP provides expert consulting services to public and private sector clients nationwide to address water quality standards, wastewater permitting and assessing potential impacts of chemicals in the aquatic environment.

Caltha LLP Aquatic Toxicology / WQ Standards Services Website