Biomonitoring of herbicides in Ontario farm applicators

Biomonitoring of pesticide residues in urine offers the advantages of integrating exposure due to all routes of entry and accounting for individual differences in several factors such as pharmacokinetics. The study was designed to measure the body burden of 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) in farm applicators and to measure compliance with label recommendations regarding the use of personal protective gear and the impact of such use on exposure.

Farmers (N=126) from Ontario, Canada, collected a preexposure spot sample of urine and then two consecutive 24-hour urine samples immediately following the farmers' first use of these herbicides during 1996. Details on the pesticides used and handling practices were collected by questionnaire.

For the farmers who reported using 2,4-D, the mean urinary concentration was 27.6 microg/l in the day-1 sample and 40.8 microg/l in the day-2 sample. The comparable figures for MCPA were 44.4 microg/l and 58.0 microg/l, respectively. Adherence to all of the recommended personal protective gear was rare (3%). Wearing goggles or a face shield during mixing and loading was associated with the lowest exposures.

The urinary concentrations of 2,4-D and MCPA of these farm applicators were of the same order of magnitude as those published in the past decade, but lower than earlier studies, indicating that improvements in education, equipment, and labeling have likely had an impact on the degree of exposure in occupational settings.