Azinphos-methyl is a broad spectrum, non-systemic, organophosphorus insecticide and acaricide with contact and stomach action. It is an inhibitor of acetylcholinesterase (AChE). It is used for the control of chewing and sucking insects in agriculture and forestry.

Entry into the aquatic environment arise from accidental spillages during transport, storage, use or bad practice. Diffuse pollution sources include spray-drift during application, agricultural run-off from treated land and the waste disposal of azinphos-methyl products.

Monitoring data from the National Rivers Authority and the National Monitoring Programme Survey of the Quality of UK Coastal Waters are presented in Appendix D. One water column concentration was found to exceed the EQS value in the NRA survey. However, no details on the actual concentration or the reason for exceedence are available. Monitoring data were not available for sediments or biota.

The available data suggest that concentrations of in UK coastal and estuarine waters are generally unlikely to exceed relevant quality standards derived for the protection of saltwater life.

The fate and behaviour of azinphos-methyl was reviewed by Jones et al (1996). Azinphos-methyl is only sparingly soluble in water (14 mg l^-1 at 15 °C) and the octanol/water partition coefficient is moderate (log Kow = 2.99 to 3.77). Based on the soil organic carbon sorption coefficient (log Koc = 3.56), sorption on suspended solids and aquatic sediments is likely.

Meyer (1965) applied azinphos-methyl WP directly to a farm pond containing algal, plant and fish life and calculated a half-life of approximately 2 days.

Flint et al (1970, cited in US EPA 1986) determined the half-life of Guthion (a formulation containing azinphos-methyl) at 30 °C in illuminated pond water and in phosphate buffer protected from light in the laboratory. The half-life in pond water was 1.2 days (pH 6.9), whereas that in the buffer solution (pH 7) was 10 days. The more rapid degradation in pond water was attributed to the effect of sunlight and micro-organisms.

An exhaustive literature review on the toxicity of azinphos-methyl to marine organisms has not been carried out for the purposes of this profile. The information provided in this section is taken from existing review documents (Jones et al 1996). The most sensitive groups of organisms have been identified.

The toxicity of azinphos-methyl to aquatic organisms was reviewed by Jones et al (1996). Few data were available for marine organisms.

Jones et al (1996) concluded that crustaceans were the most sensitive group of saltwater species. For the European species pink shrimp Pandalus montagui and brown shrimp Crangon crangon 48-hour LC50 values between 0.3 and 1 µg l^-1 have been reported, whereas the cockle Cerastoderma edule was the least sensitive species tested, with a 48-hour LC50 greater than 10 mg l^-1 (Portmann and Wilson 1971).

A number of acute LC50 values were reported for fish species. For the threespined stickleback Gasterosteus aculeatus, a 96-hour LC50 of 12.1 µg l^-1 was obtained in slightly saline water (5 ppt) and of 4.8 µg l^-1 in water with a salinity of 25 ppt (Katz 1961). Similar LC50s of 8 µg l^-1 (96-hour; Lahav and Sarig 1969, cited in US EPA 1986) and 3.2 µg l^-1 (48-hour; Mayer 1987) have been reported for the striped mullet Mugil cephalus. The 24-hour LC50 for the white mullet Mugil curema was found to be 5.5 µg l^-1 (Butler 1963, cited in US EPA 1986).

Inhibition of acetylcholinesterase (AChE) activity and mortality caused by exposure to azinphos-methyl was investigated by Coppage (1972) in a static test in 4 ppt salinity using the sheepshead minnow Cyprinodon variegatus as test species. After 48 hours exposure greater than 80%, AChE inhibition and 40 to 60% mortality were observed at 3.5 µg l^-1. After 120 hours exposure to 2 µg l^-1 78%, AChE inhibition was observed but there were no mortalities.

In a partial life-cycle toxicity test on the sheepshead minnow Cyprinodon variegatus (Cripe et al 1984), significant reductions in egg numbers from spawning adults were observed at 0.42 µg l^-1.

No data could be located for sediment-dwelling organisms.

Jones et al (1996) found no reliable data to quantify the bioaccumulation potential of azinphos-methyl but, based on the octanol/water partition coefficient (Log Kow 2.99-3.77), the authors concluded that it is only likely to be moderate.

Potential effects include:

• acute toxicity to invertebrates, in particular crustacea, and fish at concentrations above the EQS of 0.01 µg l^-1 (annual average) and 0.04 µg l^-1 (maximum allowable concentration);
• accumulation in sediments and potential effects on sediment dwelling organisms, although no data were available;

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