PANNA: Low Doses of Common Weedkiller Damage Fertility


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Low Doses of Common Weedkiller Damage Fertility
October 11, 2002

A recent study by the University of Wisconsin, Madison and Universidad de Valparaiso, Chile links very low levels of a common lawn and garden weedkiller to lowered fertility. Researchers Warren Porter, Maria Fernanda Cavieres and James Jaeger tested an herbicide mixture in the drinking water of gestating mice and report a 20% increase in failed pregnancies. Even more alarming, the largest reductions in live pups occurred in mice receiving a dose seven times lower than the maximum allowable level set by the US Environmental Protection Agency (EPA) for drinking water.

Toxicologist Warren Porter said that his group deliberately selected the sort of weed killer most commonly employed by American homeowners on their lawns. He would not name the brand, other than to say, “We bought it in a hardware store.” The mixture contained three phenoxy herbicides, 2,4-D, dicamba and mecoprop, plus added ingredients to prolong shelf life and speed absorption. Phenoxy herbicides are found in more than 1,500 pesticide products, and applied by to lawns and gardens for cosmetic purposes by approximately 29 million U.S. households. (For more information on these chemicals, visit the PAN Pesticide Database at

In contrast to the EPA, which reviews toxicity studies of individual chemicals, the researchers designed their study to examine the toxicity of the herbicide mix as sold over the counter. “You’re talking about putting a lot of very reactive chemicals together in a mix, and storing it at room temperature,” explained Porter. “We have no idea what kind of reactions might be going on once these active ingredients are formulated into products.” Another important implication of the study concerns the impacts of dose levels. A common assumption in toxicology is that higher doses present greater effects, as stated in the maxim “the dose makes the poison.” In this study, at certain times of year, the lower doses had the greatest impact on rates of fertility.

The study results were called “profoundly challenging to conventional regulatory toxicology” in an analysis published on the Our Stolen Future website (, which monitors emerging science around the interference of common contaminants with fetal development. “If these results are at all indicative of what happens with other mixtures, then current regulatory standards are unlikely to be sufficiently protective of public health.” The analysis also suggests that “A more constructive regulatory approach would be to prioritize testing based on two considerations, focus first on the commonest commercial mixtures and on mixtures detected through direct measurements of body burden.”

In June 2002, a Los Angeles Times article reported that the EPA is reviewing registration for 2,4-D. Results of that investigation will be released in early 2004. A 1996 study at the University of Minnesota by pathologist Vincent Garry also turned up evidence that formulated herbicides pose a greater risk to human fertility than indicated in trials of the separate ingredients. In a study of wheat, sugar beet and potato farm workers, Garry found twice the rate of birth defects among children of crop workers that were conceived during months when the pesticide 2,4-D was sprayed. In chemical trials of 2,4-D conducted for the government, labs used pure 2,4-D, while crop workers were handling an enhanced chemical blend of 2,4-D and added ingredients.

The Porter, et al. study is also the second in recent months to report significant impacts from levels of contamination that the EPA has determined safe in drinking water. In April 2002, the widely used pesticide, atrazine was studied at levels 30 times lower than EPA standards and found responsible for sexual abnormalities in frogs.

Meanwhile, across North America citizens’ movements are prevailing upon local governments to reduce pesticide use. In the US, the General Accounting Office has found counties in 23 states that require warning signs posted after pesticides are used and the National Coalition Against the Misuse of Pesticides counts 33 states with regulations to protect children in school areas from exposure to pesticides and herbicides. A number of Canadian cities have outlawed the application of home and garden pesticides solely for cosmetic purposes. In 1991, the municipal council of Hudson, Canada was the first to enact such a ban, and a coalition of lawn care companies sued the city. In June of 2001, the Canadian Supreme Court ruled in favor of communities’ rights and health. Since the court ruling, Angela Rickman, deputy director of the Sierra Club of Canada reports “more than 40 different (Canadian) communities are looking at pesticide restriction bylaws of one form or another.” In May and June of 2002, the club declared a “Dandelion Day” and sponsored “Getting Your Lawn Off Drugs” workshops in the Ottawa City Hall. In Canada, it appears that citizens have grasped what the US EPA has not–that lawn and garden herbicides pose a real and present danger to people and the environment.

Maria Fernanda Cavieres, James Jaeger and Warren Porter, “Development Toxicity of a Commercial Herbicide Mixture in Mice: I. Effects on Embryo Implantation and Litter Size,” Environmental Health Perspectives, Volume 110, Number 11, page 1081, November 2002; V. F. Garry, D. Schreinemachers, M. E. Harkins, J Griffith, “Pesticide appliers, biocides, and birth defects in rural Minnesota ,” Environmental Health Perspectives, Volume 104, Number 4, page 394, April 1996; Sierra Club Canada,;
Los Angeles Times, June 2 and Sept. 17, 2002, Our Stolen Future website,; National Coalition Against the Misuse of Pesticides–Beyond Pesticides website,; PANUPS, May 10, 2002, “Atrazine: Possible Cause of Global Decline in Frogs?”

Contact: PANNA

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