Aquatic Life Water Quality Criteria Derived via the UC Davis Method: II. Pyrethroid Insecticides

Abstract

Pyrethroid insecticides are broad spectrum agents that have been widely detected in sediments and surface waters in the USA (Amweg et al. 2006; Budd et al. 2007; Gan et al. 2005; Hladik and Kuivila 2009; Weston et al. 2004). They are hydrophobic compounds that primarily partition to sediments and solid materials in the water column, and exposure to pyrethroid-contaminated sediments has been demonstrated to produce toxicity in the environment (Anderson et al. 2006; Holmes et al. 2008; Phillips et al. 2010; Weston et al. 2004; Weston et al. 2005). Only very low concentrations are found freely dissolved in the aqueous phase, but these pesticides are still of concern to water quality managers because they exhibit toxicity to aquatic organisms at very low concentrations (<1 μg/L). Water quality regulators in the USA are required, under the Clean Water Act (section 303(c)(2)(B)), to provide numeric water quality criteria for priority pollutants that could reasonably be expected to interfere with the designated uses of a state’s waters. Numeric water quality criteria are chemical concentrations in water bodies that should protect aquatic wildlife from the toxic effects of those chemicals, if these concentrations are not exceeded. Numeric criteria are derived using existing toxicity data; consequently, criteria calculation is dependent on the availability of these data. In the USA, there are currently no numeric criteria available for the pyrethroids, and many of the available pyrethroid data sets do not meet the requirements of the 1985 US Environmental Protection Agency (USEPA) criteria derivation methodology (USEPA 1985). One of the goals of developing the UC Davis methodology (UCDM) was to be able to derive criteria for compounds that do not meet all of the USEPA (1985) data requirements, such as the pyrethroids.