Critical review of chronic toxicity testing approaches with the saltwater mysid (Americamysis bahia) used in pesticide registration.

Abstract

The United States Environmental Protection Agency (USEPA) has a conditional requirement for a chronic toxicity test with mysids (Americamysis bahia) for registration of pesticide products. Achieving performance acceptability criteria in control treatments for this study can be challenging because the current draft test guideline, which was published in 1996 under USEPA Office of Prevention, Pesticides, and Toxic Substances (OPPTS) 850.1350, Mysid Chronic Toxicity Test, provides limited information on study design and conduct. This critical review was undertaken to (1) identify areas of inconsistency in acceptability criteria between the 1996 draft OPPTS test guideline and ASTM International test guidance, (2) highlight areas that require additional clarification, (3) discuss areas that are impractical or have uncertain scientific relevance regarding the objectives of the test, and (4) provide recommendations for revision of the draft OPPTS test guideline. To achieve this, 116 final study reports from chronic mysid toxicity tests conducted over approximately the past 30 years were collected. From these reports, survival, growth, and reproduction data from negative and solvent control groups were compiled. Through investigation of trends in the data, it became apparent that no-observed-effect concentrations (NOECs) were most commonly based on reproductive endpoints, followed by adult growth endpoints and adult survival. Notably, less than 1% of studies had a NOEC based solely on a second-generation measurement endpoint. Analysis of this comprehensive data set provided clarity on the establishment of acceptability criteria for the study and elements of the testing procedure that can be streamlined without loss of critical information, which resulted in a set of recommendations to improve future versions of the chronic mysid toxicity test guideline.