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(60-02) Probabilistic aquatic risk assessment for chlorpyrifos use on orchards in the UK. Crane, Mark1, Whitehouse, Paul*,2, Watts, Chris2, Comber, Sean2, Moore, Dwayne3, Giddings, Jeff4, 1 Crane Consultants, Chancel Cottage, 23 London Street, Faringdon, Oxon, UK2 WRc-NSF, Henley Road, Medmenham, Marlow, Bucks, UK3 The Cadmus Group, 411 Roosevelt Avenue, Suite 204, Ottawa, Canada4 The Cadmus Group, Marion, Massachusetts ABSTRACT- This presentation describes a case study performed for the UK Pesticides Safety Directorate to determine the value to UK regulators of probabilistic risk assessment techniques for aquatic environments. The organophosphorus insecticide chlorpyrifos was selected as a model compound and a realistic worst case scenario developed using the SEISMIC database, the MACRO preferential flow model, the EU spray drift model, and UK-specific information on pond biodiversity. Application of chlorpyrifos to top fruit grown on the Wick soil series presented a realistic scenario of potentially high aquatic exposure. Probability density functions (pdfs) were developed for this scenario by running MACRO 30 times with different input parameters. The pdf from MACRO was then combined with a pdf from spray drift, using the Crystal Ball software package, to produce an overall exposure pdf. This was combined with pdfs for biological effects, estimated using different models and different numbers of species, to produce a Toxicity Exposure Ratio pdf. The implications of such an approach for European pesticides regulation are discussed. Key words: Chlorpyrifos, Ecological risk assessment, Species sensitivity distributions, Pesticide exposure |
