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Investigation into the validity of extrapolation in setting maximum residue levels for pesticides in crops of similar morphology Part A Chemistry, analysis, control, exposure & risk assessment

Reynolds, S.L., Fussell, R.J., MacArthur, R.
Food additives & contaminants 2005 v.22 no.1 pp. 31-38
Daucus carota, pesticide application, field experimentation, pesticide registration, pesticide residues, maximum residue limits, carrots, Pisum sativum subsp. sativum var. macrocarpon, Brassica napus var. napobrassica, rutabagas, cauliflower, Brassica oleracea var. botrytis, Brassica oleracea var. italica, broccoli, Phaseolus vulgaris, green beans, harvest date, application timing, estimation, validity, geographical variation, pesticide safety and handling
Field trials were initiated to investigate if extrapolation procedures, which were adopted to limit costs of pesticide registration for minor crops, are valid. Three pairs of crops of similar morphology; carrots/swedes, cauliflower/calabrese (broccoli) and French beans/edible-podded peas; were grown in parallel at four different geographical locations within the UK. The crops were treated with both systemic and non-systemic pesticides under maximum registered use conditions, i.e. the maximum permitted application rates and the minimum harvest intervals. Once mature, the crops were harvested and analysed for residues of the applied pesticides. The limits of quantification were in the range 0.005-0.02 mg kg(-1). Analysis of variance and bootstrap estimates showed that in general, the mean residue concentrations for the individual pesticides were significantly different between crop pairs grown on each site. Similarly, the mean residue concentrations of most of the pesticides in each crop across sites were significantly different. These findings demonstrate that the extrapolations of residue levels for most of the selected pesticide/crop combinations investigated; chlorfenvinphos and iprodione from carrots to swedes; carbendazim, chlorpyrifos, diflubenzuron and dimethoate from cauliflower to calabrese; and malathion, metalaxyl and pirimicarb from French beans to edible-podded peas; appear invalid.