Harvesters in strawberry fields: A literature review of pesticide exposure, an observation of their work activities, and a model for exposure prediction
Strawberry harvesters hand-pick fruit that may result in pesticide exposure from hand foliar contact. This paper included a review of publications on harvester pesticide exposure, an observation of their work activities, and development of an alternative model for pesticide exposure prediction. Previous studies monitored the dermal pesticide exposure of strawberry harvesters and found most of the exposure (> 70%) was on the hands. Exposure rates (ERs) were calculated as pesticide amount on the skin per hour worked, assuming foliar contact is proportional to daily work hours. Transfer factors (TFs), used for predicting exposure, were calculated by dividing the ER by the amount of dislodgeable foliar pesticide residue. However, the ERs for harvesters working in the same field at the same time varied by as much as 10-fold, and TFs calculated from different studies varied by up to 100-fold. We tested the assumption of foliar contact time being proportional to daily work hours. We observed full work-day activities of 32 strawberry harvesters. We found that their foliar contact time per work minute differed by up to 46%. We suggested using the amount of strawberries picked to predict harvester foliar contact. For all observed harvesters, their foliar contact time per kg of strawberries picked was 35 ± 5 s. This value was similar among harvesters with varying years of experience, of different gender, and using gloves or not. We proposed a predictive model using the amount of strawberries picked to predict harvester pesticide exposure. The exposure predicted by the model is close to the exposure measured in previous monitoring studies (R2: 0.84). The model slope is 0.33 ± 0.03 × 103 cm2/kg. Model prediction accuracy was confirmed by monitoring captan exposure to harvesters in two fields. The model may be used as a quick screening method to estimate pesticide exposure before conducting complex human monitoring research.