19
Feb
Hazards Linked to Still Unregulated Pesticide Mixtures
(Beyond Pesticides, February 19, 2016) Pesticide mixtures are more harmful than individual pesticides, according to a University of California, Los Angeles (UCLA) study that focuses on three commonly used fumigants — chloropicrin, Telone, and metam salts. The study also concludes that, while California law requires the Department of Pesticide Regulations (DPR) and county agricultural commissioners to assess these kinds of cumulative risks when regulating pesticides, they have so far failed to do so.
The report, titled Exposure and Interaction — The Potential Health Impacts of Using Multiple Pesticides: A Case Study of Three Commonly Used Fumigants, was published by the Sustainable Technology and Policy Program, based in the UCLA School of Law and the UCLA Fielding School of Public Health. The case study of the three fumigants, which are commonly applied together in California on high value crops, such as strawberries, tomatoes, tree nuts, and stone fruits, finds that:
- These pesticides may interact to increase the health risk for California farm workers and residents,
- Workers and residents are regularly exposed to two or more of these pesticides simultaneously, and
- DPR does not regulate the application of multiple pesticides to prevent or decrease risks to human health, despite having authority to do so.
While chloropicrin, Telone (also known as 1,3-D), and metam salts are toxic when used individually, the UCLA report demonstrates that their combined effect may be even greater because the pesticides may interact to increase damage to cells, leading to an increased 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.
“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 public health. 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 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 examines 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 including 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,Ph.D., an author of the report and a professor emeritus of environmental health sciences at the Fielding School of Public Health.
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 report 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.
The UCLA study contributes to the growing body of research on the interactive effects of pesticides on human health and the environment. For example, Tyrone Hayes, PhD, professor of integrative biology at UC Berkeley conducted research on the interactive effects of atrazine and other pesticides in a study on frogs. The study compared the impact of exposure to realistic combinations of small concentrations of corn pesticides on frog metamorphosis. The study concluded that frog tadpoles exposed to mixtures of pesticides took longer to metamorphose to adults and were smaller at metamorphosis than those exposed to single pesticides, with consequences for frog survival. The study revealed that “estimating ecological risk and the impact of pesticides on amphibians using studies that examine only single pesticides at high concentrations may lead to gross underestimations of the role of pesticides in amphibian declines.” (Watch Dr. Hayes’ talk, Protecting Life: From Research to Regulation.)
Similarly, pesticide products available for sale are often chemical mixtures of active ingredients that create a cocktail of toxins while studies on pesticide combinations have demonstrated neurological, endocrine, and immune effects at low doses. For example, research conducted by Warren Porter, PhD., professor of zoology and environmental toxicology at the University of Wisconsin, Madison, examined the effect of fetal exposures to a mixture of 2,4-D, mecoprop, and dicamba exposure ””frequently used together in lawn products like Weed B Gone Max and Trillion”” on the mother’s ability to successfully bring young to birth and weaning. Researchers began by testing pesticide concentrations diluted to levels that are considered “safe” by the U.S. Environmental Protection Agency (EPA). The results were striking: Dr. Porter found that, “This common lawn pesticide mixture is capable of inducing abortions and resorptions of fetuses at very low parts per billion. The greatest effect was at the lowest dose.”
EPA’s risk assessment process also fails to look at chemical mixtures and synergistic effects, as well as certain health endpoints (such as endocrine disruption), disproportionate effects to vulnerable population groups, and regular noncompliance with product label directions. These deficiencies contribute to its severe limitations in defining real world poisoning, as captured by epidemiologic studies in Beyond Pesticides’ Pesticide-Induced Diseases Database.
Another toxic fumigant, methyl bromide, has been linked to serious human health impacts. The substitute fumigants for methyl bromide also have severe negative health and environmental impacts. For instance, sulfuryl fluoride was also put forward as an alternative, but due to concerns of fluoride overexposure, EPA cancelled sulfuryl fluoride use on stored food products in 2011, however Congress has held up the decision (See When Politics Trumps Science and Health Suffers). The highly controversial methyl iodide, which was also put forward as an alternative, is known to cause miscarriages, thyroid dysfunction, and cancer. It was approved by California state pesticide regulators in 2010, but the manufacturer eventually agreed to stop producing the chemical in 2013.
For more information on pesticide synergy, see Synergy: The Big Unknowns of Pesticide Exposure. For information on individual pesticide health effects, see the Pesticide Gateway.
Sources: UCLA Newsroom Press Release
All unattributed positions and opinions in this piece are those of Beyond Pesticides
