Pesticide mixtures may increase health risks but are still unregulated by California, report says

February 18, 2016 by Kathy Wyer, University of California, Los Angeles

A UCLA study has found that the state agency responsible for protecting Californians from the dangers of pesticides is failing to assess the health risks likely posed by pesticide mixtures, which are believed to be more harmful than individual pesticides.

The report was published by the Sustainable Technology and Policy Program, which is based in UCLA School of Law and the UCLA Fielding School of Public Health. It recommends the California Department of Pesticide Regulations do more to protect people from the dangers of exposure to multiple .  

"People are exposed throughout their lifetimes to mixtures of chemicals and other agents, including pesticides," said Timothy Malloy, a professor at the School of Law, faculty director of the Sustainable Technology and Policy Program and one of the report's authors. "Increasingly, research shows that pesticide mixtures can interact to cause larger-than-anticipated impacts on . Farm workers and local residents are especially at risk, given that they may be exposed to two or more pesticides simultaneously or in sequence."

The study focused on mixtures of three fumigants—chloropicrin, Telone and metam salts—that are frequently used on high-value crops such as strawberries, tomatoes, tree nuts and stone fruits. Used individually, the pesticides are suspected developmental toxins, and are known carcinogens and respiratory irritants.

But the UCLA report demonstrates that their combined effect may be even greater because the pesticides may interact to increase damage to cells, which could then increase the risk of cancer.

The report notes that the fumigants analyzed in the study can reduce the body's ability to remove or neutralize toxic substances. The study hypothesizes that pesticide mixtures may increase the possibility of gene mutations and decrease the body's ability to repair damaged DNA.                                                      

The report also shows that some California communities are being exposed simultaneously to these chemicals. Using data from the Pesticide Research Institute, which collaborated with UCLA, the report examined the area near Rio Mesa High School in Ventura County from July 26 to August 3, 2013. The model shows exposure to multiple pesticides at locations such as schools, day care centers and parks.

"Fumigant pesticides are highly toxic chemicals that are likely to vaporize and drift away from the farms where they're applied and affect people in surrounding schools, houses, businesses and fields," said John Froines, an author of the report and a professor emeritus of at the Fielding School of Public Health. 

The report concludes that California law requires the Department of Pesticide Regulations and county agricultural commissioners to assess these kinds of cumulative risks when regulating pesticides, but that they have so far failed to do so.

The report acknowledges that assessing the risks of multiple exposures is challenging, but it also finds that it is essential for fully understanding potential adverse effects. The recommends that DPR and agricultural commissioners evaluate pesticide mixtures and implement regulations to more adequately protect human health, including:

  • Testing pesticides that are sold as part of a mixture for interactive toxic effects before approving their use.
  • Requiring evaluation of products that are not used as part of a mixture but are used in combination or sequentially with other pesticides to determine the likelihood of interactive effects.
  • Considering pesticides' interactive effects—which may occur either because the pesticides are marketed in combination or because they are commonly used together—in performing risk assessments and establishing management requirements. 

Explore further: Long-term effects of common pesticides on aquatic species

More information: Interactive Effects of Fumigants.

Related Stories

Pesticide regulation in California is flawed, UCLA report says

September 23, 2013

Approximately 30 million pounds of fumigant pesticides are sprayed on valuable California crops each year—strawberries, tomatoes, peppers and the like—in an attempt to control pests. Responsibility for the safety of pesticides ...

Recommended for you

Scientists create 'Evolutionwatch' for plants

February 21, 2018

Using a hitchhiking weed, scientists from the Max Planck Institute for Developmental Biology reveal for the first time the mutation rate of a plant growing in the wild.

Triplefin fish found to have controlled iris radiance

February 21, 2018

A team of researchers with the University of Tübingen in Germany has found an example of a fish that is able to control light reflected from organs next to its pupils—a form of photolocation. In their paper published in ...

New tool tells bioengineers when to build microbial teams

February 21, 2018

Researchers at Duke University have created a framework for helping bioengineers determine when to use multiple lines of cells to manufacture a product. The work could help a variety of industries that use bacteria to produce ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.