Occupational paraquat exposure of agricultural workers in large Costa Rican farms

Objective  Paraquat is an herbicide widely used worldwide. This study determined the extent of occupational exposure to paraquat among farm workers in Costa Rica and identified determinants of occupational exposure. Methods  Twenty-four hour urine samples were collected from 119 paraquat handlers and 54 non-handlers from banana, coffee and palm oil farms. Information about herbicide handling operations was also collected. The urinary paraquat levels were determined by an enzyme-linked immunosorbent assay (ELISA) with a limit of quantification (LOQ) of 2 ng/mL. Inhalable dust and airborne paraquat levels were simultaneously measured for a subset of the participants. Results  Urinary paraquat measurements were non-detectable or very low when workers did not handle paraquat. For handlers, 83.3, 47.1 and 63.9% of the samples were below the LOQ on before-, during- and after-paraquat spray days, respectively. The arithmetic mean (±SD) of urinary paraquat level on days when workers handled paraquat was 6.3 (±10.45) μg/24 h. Paraquat exposures among handlers on spray day were significantly associated with the type of crop. Conclusion  Non-handlers had negligible urinary paraquat, while detectable paraquat exposures were observed among handlers on spray day. Urinary paraquat levels were different by crop.