farm workers

Pesticide Combination Impacts Often Greater than the Sum of Their Parts, New Study Says

Most scientists, farmers, and regulators usually consider the health effects of pesticides one at a time. But that’s not always how they’re used.

A new report by researchers at the University of California Los Angeles’s Sustainable Technology & Policy Program (STPP) took a rare look at several pesticides–all fumigants–that are often applied in combination, chloropicrin, 1,3-dichloropropene, and metam salts. It found that when mixed together, the chemicals can interact and become more toxic, endangering and leaving farmworkers, neighbors, and schoolchildren without adequate protection.

February 24, 2016 | Source: Civil Eats | by Elizabeth Grossman

Most scientists, farmers, and regulators usually consider the health effects of pesticides one at a time. But that’s not always how they’re used.

A new report by researchers at the University of California Los Angeles’s Sustainable Technology & Policy Program (STPP) took a rare look at several pesticides–all fumigants–that are often applied in combination, chloropicrin, 1,3-dichloropropene, and metam salts. It found that when mixed together, the chemicals can interact and become more toxic, endangering and leaving farmworkers, neighbors, and schoolchildren without adequate protection.

“We know these are being applied on purpose together,” and some have similar health effects, including cancer, says report co-author Susan Kegley, principal, and CEO of the California-based Pesticide Research Institute.

Millions of pounds of these three pesticides are commonly used in combination to grow strawberries, tomatoes, peppers, grapes, nuts, and other crops. All together about 30 million pounds were used on California farm fields in 2013 alone and together they account for about a fifth of all pesticides used in the state.

The three chemicals examined are all used as fumigants, meaning that they are applied to kill pests in soil rather than on plants as they grow. Unlike other types of pesticides, fumigants don’t end up in food. But because they’re often applied as gasses, they drift easily. This makes the risk of exposure for people living and working nearby very high.

According to the report, California agricultural workers and residents, including children, are regularly exposed to two or more of these chemicals simultaneously since they are often applied as a cocktail or applied on the same day. “There’s increasing evidence coming forward that [effects of] mixtures are greater than the sum of their parts,” report co-author and director of UCLA’s Sustainable Technology & Policy Program Virginia Zaunbrecher told Civil Eats.

What Sets Fumigants Apart?

“Fumigants are completely different beasts than other pesticides,” says Miranda Kram, U.S. Geological Survey (USGS) chemist and California Groundwater Ambient Monitoring and Assessment Program chief. “They are volatile”—meaning they evaporate easily—“and are applied as gasses, often injected right into the soil,” she explains. And while they disperse readily, they also take a long time to degrade so they persist in the environment, including in groundwater.

“[Fumigants are] also applied at much higher rate than other chemicals,” explains Anne Katten, California Rural Legal Assistance Foundation pesticide and work safety project director, often as much as hundreds of pounds per acre.

“Most fumigants drift when they’re being applied and for 24 hours after, but can continue for a week or so,” adds Kegley.

Throughout parts of California where these fumigants are used, there are housing developments and apartments, as well as schools, right next to fields. That people are actually being exposed “is not speculation,” says Kegley. Dozens of people have had to evacuate their homes and schools due to pesticide drift, in California and elsewhere around the country.