A group of Santa Maria farmworkers has volunteered to participate in a UC study to determine whether they are exposed to hazardous pesticide residues when harvesting strawberries.

The study is led by Robert Krieger, UC Cooperative Extension specialist in the Department of Entomology at UC Riverside. Krieger is an expert in environmental and occupationaltoxicology.

This summer, Krieger and a team of researchers spent nearly three weeks in Santa Maria with workers at DB Specialty Farms. The workers wear gloves as they pick strawberries. Before each break, their gloves are collected and frozen for later lab analysis.

“We’ve found that pesticides are transferred to the gloves during normal work and we’re measuring the amounts that are transferred in hopes that we can use it to measure total exposure,” Krieger said. “The real question is how much exposure occurs, how much is OK, and how little occurs under normal conditions of use.”

The team is also collecting samples of strawberries harvested by the workers and samples of leaves.

In order to understand uptake and excretion, the workers are asked to collect urine for 24-hour periods after working in sprayed fields. To be certain any sign of pesticides in the urine came from work exposure, the researchers have also collected 24-hour urine samples from spouses or roommates of the field workers to assess dietary or home exposure.

“The levels of exposure are determined by how much is applied, how much remains on the crop and how much is transferred to people. We’ve independently measured those and came up with an assessment of how much a person is exposed to during their normal work,” Krieger said.

The research focuses on two pesticides: the organophosphate malathion and the pyrethroid fenpropathrin. After the pesticides are applied, there is a three-day waiting period before harvest gets under way. In the project, as soon as the workers are back in the field, the monitoring begins.

Studies that Krieger has conducted over the past 18 years show that low, safe levels of pesticide are absorbed and rapidly excreted by harvesters. Breakdown products of the pesticides – parts of the pesticide molecule that are not toxic – can be measured in the urine, but it is not known whether the pesticide broke down on the plant, before the workers were exposed, or if the workers’ metabolism broke down the pesticides.

“Those breakdown products are not toxic, but if they are absorbed, they will appear in the urine and we can’t tell whether a plant made it or a person made it and that complicates our analysis and that’s one of the new areas that we’re investigating in 2012,” Krieger said.

By comparing the gloves, fruit, leaves and urine and using sophisticated metabolic chemistry in the laboratory analyses, the researchers will be able to reconstruct how much exposure there was during the work day.