Characterising occupational exposure to glyphosate among amenity horticulturists
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A dearth of knowledge exists regarding occupational glyphosate exposures among amenity horticulturalists. Glyphosate is the highest volume herbicide used globally, and has recently been classified by the International Agency for Research on Cancer as a 2A 'probably carcinogenic to humans’. The objective of this study was to characterise glyphosate exposures and identify exposure determinants among amenity horticulturists. Human biomonitoring assessments were completed by collecting spot urine samples from workers. In parallel, a dermal and inadvertent ingestion study was completed by collecting wipe samples of the worker’s hands and perioral region and by analysing samples of worker gloves. Samples were analysed using liquid chromatography tandem mass spectrometry (LC-MS/MS). Linear mixed effect regression models were constructed to evaluate determinants of dermal, inadvertent ingestion and total glyphosate exposure. A total of 205 urine samples and 351 wipe and glove samples were collected and analysed for glyphosate across 69 work tasks involving the glyphosate based pesticide products. Glyphosate concentrations ranged from below the limit of quantification to 10.66 μg L−1; the human biological half-life was estimated to be 5 ½ to 10 hours. Peak exposure levels were identified in urine samples collected up to three hours after cessation of the pesticide task. A forward built mixed effect model including sampling time, participant age and application type explained 62% of the variability in worker hand glyphosate concentrations. In the inadvertent ingestion exposure model the determinants hand contamination, the frequency of hand to mouth and surrounding area contact and sampling time explained 50% of the variability in perioral concentration. Combined hand and perioral region concentrations explained 40% of the variability in the urinary glyphosate concentrations (μg L-1). Occupational glyphosate exposures among amenity horticulturalists are higher than expected from environmental exposure alone and comparable with agricultural studies. New information is reported on the human biological half-life of glyphosate.