Report No DWI0117

Sept 1990

To derive provisional environmental quality standards (PEQSs) for fenitrothion for the protection of the different water uses, based on readily available information on environmental fate and toxicity.

This report is one of a series aimed at proposing PEQSs for those 'Red List' substances (DoE 1989a) for which no environmental quality standards (WQSs) currently exist.

Fenitrothion is not very persistent in the aquatic environment, with estimated half-lives being typically one to ten days. The bioaccumulation data suggest a moderate tendency to accumulate in aquatic organisms, but extensive food-chain bioconcentration is not expected because fenitrothion is apparently rapidly eliminated by most invertebrates and vertebrates, including humans. Aquatic organisms vary in their responses to exposure, with certain crustaceans and insects being particularly sensitive. A PEQS of 10 ng/l is proposed for the protection of freshwater life, derived by applying an arbitrary safety factor of about 100 to acute LC50s of around 1 µg/l reported for certain crustaceans in laboratory tests. This PEQS should be expressed as an annual average value. A provisional maximum acceptable concentration of 250 ng/l is also proposed, based on a no effect concentration of 1.3 µg/l for insect drift and allowing for the apparently five-fold higher sensitivity of certain crustaceans compared to the insects tested. The same provisional standards are proposed for the protection of saltwater life because the few available data suggest similar sensitivity to equivalent freshwater organisms. Because fenitrothion readily associates with suspended solids, samples should be allowed to settle for at least one hour before analysis, which should be carried out on the supernatant. These provisional standards may be revised should additional relevant field data become available.

Based on the acceptable daily intake derived by FA0 (1985) for fenitrothion the suggested safe concentration in drinking water is 1 µg/l, which is higher than the maximum allowable concentration of 0.1 µg/l specified for individual pesticides in the EC Drinking Water Directive (CEC 1980). No advisory value is included for fenitrothion in the Guidance on Safeguarding Public Water Supplies (DoE 1989b).

This is only a brief review of the available data for fenitrothion, but the suggested PEQS values are considered to be adequate as guide values to protect freshwater and saltwater life. A more detailed study is recommended for a fuller assessment of the impact of fenitrothion on the different water uses. There is a particular need for further environmental verification of laboratory toxicity data, particularly for the more sensitive crustaceans. The analytical techniques currently applied by the UK water industry require improvement to make them adequate for monitoring the proposed PEQSs.

This report reviews the readily available information on the entry of the insecticide fenitrothion into the aquatic environment, its subsequent fate and persistence, and its toxicity to and bioaccumulation in aquatic organisms. This information is used to derive provisional environmental quality standards for the protection of freshwater and marine life. Brief consideration is also given to its toxicity to non-aquatic organisms, including man.

Copies of this report may be available as an Acrobat pdf download under the 'Find Completed Research' heading on the DWI website.