Estimation of cumulative exposure to organophosphate sheep dips in a studyof chronic neurological health effects among United Kingdom sheep dippers

Objectives-To derive a method for retrospectively estimating cumulative exp osure to organophosphate (OP) pesticides among a cross section of United Ki ngdom sheep dippers, as part of a wider epidemiological study of neurologic al abnormality within this group of workers. Methods-A hygiene study of dipping sessions at 20 farms using diazinon base d dips was carried out by two experienced occupational hygienists. Observat ions on the exposure of people to concentrate and dilute dip were recorded throughout each dipping session, together with the other relevant factors i ncluding the use and condition of protective clothing. Concentrations of ur inary metabolites of diazinon were used to measure actual exposure to OPs. To estimate exposure in the subsequent epidemiological study, an occupation al exposure history questionnaire was developed using results from the hygi ene study and an empirical exposure model. Results-In the hygiene study, increased urinary metabolites were associated with the handling of concentrate dip and exposure to dilute dip wash throu gh splashing. Very few dippers wore the recommended protective clothing. Th e handling of concentrate dip was the principal source of exposure to OPs. Dipping task was used as a surrogate for splashing of dilute dip in retrosp ective exposure estimation. In the epidemiological study, cumulative exposu re to OP sheep dips was highly correlated with the total number of dipping days, but not with age.. Conclusions-Sheep dip concentrate is the most important source of OP exposu re among sheep dippers and estimates of exposure to OPs during routine dipp ing should take due account of exposure to concentrate dip as well as to th e dilute dip wash. The observed use of recommended protective clothing by m ost subjects was insufficient to allow a proper empirical assessment of its effectiveness.