Pesticide residues on the external surfaces of field-crop sprayers: environmental impact

There is increased awareness of the need to clean the external surfaces of sprayers, but the extent to which the washings may impact on the environment is not known. Quantification of the levels of external residues on sprayers could give an indication of the potential environmental impact of sprayer cleaning. The presence of azoxystrobin, carbendazim, chlorothalonil, cyanazine, cypermethrin, epoxiconazole, flusilazole, isoproturon, kresoxim-methyl, metazachlor, pendimethalin, pirimicarb and tebuconazole on thirteen sprayers, sampled on two occasions was investigated. Composite samples were taken from the boom, nozzles and spray tank (delivery system) and the mudguard, cab door, rear window and windscreen (tractor body). Despite being subject to some form of cleaning, pesticides were detected on all sprayers. Residues were found at higher quantities and with greater frequency on the nozzles and booms, but the mean dose on the spray tank was equal to that on the mudguard (7.2 mg m(-2)). Isoproturon, pendimethalin, metazachlor, chlorothalonil and azoxystrobin were all detected above 1000 mg m(-2) on the delivery system, whereas on the tractor body the highest concentrations were between 100 and 1000 mg m(-2) (isoproturon, pendimethalin, chlorothalonil and carbendazim). On the whole, azoxystrobin was detected on the least number of occasions. However, there was great variation within and between compounds and sampling sites. Generally sprayers were not cleaned frequently or efficiently, enabling residues to accumulate on the external surfaces where they can remain for years. The findings here indicate that the quantity of these residues may be sufficient to be harmful to aquatic organisms should the residues enter a watercourse. In addition, if all the residues were removed by cleaning in the field and the washings catchment area was 15 m2 or less, overdosing could occur. Further work is required to assess whether a more frequent cleaning regime would reduce the overall environmental impact of cleaning sprayers. Implications for potential occupational exposure are considered elsewhere.