A comparison of the fate and effects of prochloraz in artifical and natural sediments

The current draft EC regulatory guidance document for the authorisation of plant protection products, directive EEC 91/414, contains provision for testing the potential toxicity of pesticides to sediment dwelling organisms. Development of an appropriate method is currently in progress, by a German regulatory and industry working group. The compounds which are expected to trigger sediment toxicity data are likely to be those which are relatively persistent, with a high Kow, with the potential for significant adsorption to sediments, and may have previously demonstrated toxicity to aquatic organisms. The current proposal from this working group involves an artificial sediment, prepared in accordance with OECD guideline 207, as used for earthworm toxicity tests. The implications of using this sediment on the distribution, fate and availability of the compound under test are considered. This paper presents toxicity data for Chironomus riparius generated using radiolabelled Prochloraz® in systems using this artificial sediment and two natural sediments. The fate of prochloraz was also investigated in the same systems and compared with data generated from sediment/water studies carried out in accordance with regulatory guidelines. At the maximum Predicted Environmental Concentration (PEC) of 195 μg-1 nominal, prochloraz had no effects on the survival and development of Chironomus riparius. The fate of the compound in the systems used was enhanced possibly as a result of photodegradation.