UC Riverside

The widespread use of pesticides in California is commonly viewed as a significant public health concern. Exposure is particularly a concern for workers who use pesticides in agriculture or who are exposed to them during the harvesting of fruits and vegetables. Previous research has shown that direct dermal and clothing contact with foliar residues is primarily responsible for pesticide exposures among harvesters. These exposures occur primarily due to hand contact with treated leaf surfaces while picking the fruit. The overall objective of our research was to conduct detailed, systematic evaluations of strawberry harvester exposures for periods extending up to 3 weeks after the application of malathion, an organophosphate insecticide, and fenpropathrin, a pyrethroid insecticide. Since exposure occurs primarily through the workers' hands, we decided to also investigate the effectiveness of rubber latex gloves as sampling dosimeters to measure the transfer and dissipation of malathion and fenpropathrin.

During the first phase of our studies, we conducted controlled field studies on turf using rubber latex gloves to define the factors that could influence the transfer of pesticides to the glove and that would affect their use as a residue monitoring device. We developed a novel sampling device called the Brinkman Contact Transfer Unit (BCTU) to study the glove characteristics and residue transfer and accumulation under controlled conditions on turf. A validation of the use of rubber latex gloves as a residue sampling dosimeter was performed by comparing pesticide transfer and dissipation from the gloves with the transferable turf residues sampled using the validated California Department of Food and Agriculture (CDFA) roller, a standard measure of residue transfer. The observed correlation between the two methods were 0.93 for malathion and 0.87 for fenpropathrin, indicating that the BCTU is a useful surrogate tool for studying available residue transfer to rubber latex gloves under experimental conditions.

In the second phase of our studies, we investigated the transfer of pesticide residues from foliage to strawberry harvesters under normal work conditions in the field. In addition, foliar residue dissipation from the leaves and gloves was measured using five independent sampling methods. Malathion and fenpropathrin residues, sampled by measuring dislodgeable foliar residues or the transfer of foliar residues to cotton cloth dosimeters, decayed by 90% within 7 days after pesticide application. When harvesters picking fruit wore rubber latex gloves for food safety and hygiene reasons, the gloves accumulated pesticide residues. Within 7 days, the recovery of residues on the gloves decreased by 75%. Though this decline is slightly slower than that seen with the foliar residues, both reached low stable levels. Quantitative measurements of end-of-shift harvester hand washes and 16 hour harvester urine samples were also collected from barehanded and gloved harvesters to study hand exposures and internal exposures as absorbed daily dosages, respectively. Hand wash residue levels decayed by 90%, within 7 days after pesticide application, and less than 2% of measured residues penetrated the latex gloves to reach the harvester hands. Based on these measures, the gloved harvesters had 45% lower internal exposure than the barehanded harvesters, demonstrating that rubber latex gloves are a protective barrier to surface residues. Overall, the absorbed daily doses of malathion for barehanded and gloved harvesters were lower than 0.005 mg/kg-day. However, the decline in excreted urine metabolites were only 43% in gloved harvesters and 33% in barehanded harvesters, which was slower and more prolonged than expected based on our observations from other sampling techniques.

Our results indicate that there were likely other sources of exposure such as malathion breakdown products present on the foliar surfaces after the dissipation of malathion itself. This is consistent with recent studies that have shown that malathion degradation products are present for prolonged periods on foliar surfaces. Overall, our studies demonstrate that latex gloves can be useful as dosimeters of pesticide residues and show that malathion and fenpropathrin themselves dissipate relatively quickly from strawberry fields.