Glyphosate Is Widely Used, Probably Carcinogenic To Humans

The International Agency for Research on Cancer (IARC), an agency of the World Health Organization (WHO), recently reviewed new scientific data on pesticides that cause widespread exposures. The IARC meeting and subsequent report provided new or updated evaluations on five organophosphate chemicals, including glyphosate, which was found to be “probably carcinogenic” to humans. Glyphosate is a broad-spectrum herbicide widely used to control weeds.

The evidence of carcinogenicity is based on human studies of agricultural exposure to glyphosate in the United States, Canada, and Sweden—primary exposure to glyphosate can occur from living near farms that spray herbicides or through home use on lawns or gardens. One study from the Journal of Toxicology and Environmental Health, cited by the IARC report, found that chromosomal damage in community members increased after glyphosate-containing herbicides were sprayed nearby; and another study by geneticists in Ecuador found chromosomal aberrations and malformations in children. Glyphosate also caused DNA and chromosomal damage in human cells during laboratory experiments. Furthermore, according to Dr. Nancy Swanson of the Massachusetts Institute of Technology, glyphosate can act as a hormone disruptor, causing many adverse health effects and potentially driving up healthcare costs.

Moreover, the IARC report cites convincing evidence that glyphosate causes cancer in laboratory animals.

The chemical has been found to cause adverse effects in male offspring of pregnant rats that transfer glyphosate via breast milk. On the basis of tumors in laboratory mice, the U.S. Environmental Protection Agency (EPA) originally classified glyphosate as a possible cause of cancer in humans in 1985.

In 1991, the Scientific Advisory Panel of the EPA reversed that decision, but noted that the original results were still statistically significant. The IARC Working Group that conducted the evaluation considered the significant findings from the EPA report, in addition to several more recent positive results, concluding that there is “sufficient evidence” of carcinogenicity in experimental animals.

Glyphosate is the active ingredient in Monsanto’s Roundup, a weed killer widely used on both corn and soybeans in the U.S. Globally, glyphosate represents the highest production volume of any herbicide and is used as an ingredient in more than 750 different products for agriculture, forestry, urban, and home applications. The chemical is highly prevalent in the environment—it’s been found in the blood and urine of agricultural workers, in air and water samples, and in human breast milk.

The IARC report identified studies confirming the toxicity of glyphosate specifically, rather than assessing herbicide formulations as a whole, which could be toxic because of other inert ingredients.

Inert ingredients are added to glyphosate to make it more effective when sprayed on plants and are largely unregulated. Polyethoxylated tallowamine, or POEA, is a common inert ingredient in Roundup that has been found to kill human cells. The EPA approves nearly 4,000 inert ingredients for use in agriculture.

Despite the evidence of glyphosate toxicity, industry groups have been quick to denounce the findings of the IARC report. “We are outraged with this assessment,” said Robert Fraley, Monsanto’s chief technology officer, arguing that the finding was derived from “cherry picking” data. The National Corn Growers Association also attacked the report, stating, “Notably, although IARC is part of the World Health Organization, it appears that the WHO does not always endorse IARC’s decisions. Thus, it would be presumptive to conclude that the WHO would do so in this situation.” However, the WHO stood by the IARC report.

“We feel confident that our process is transparent and rigorous, based on the best available scientific data, and that it’s free from conflicts of interest,” said Dr. Dana Loomis, deputy head of the monographs section for the IARC and a co-author of the agency’s report. The report involved 17 experts from 11 countriesAccording to Loomis, it is “categorically not true” that the IARC overlooked research on glyphosate, as Monsanto and other agriculture groups alleged

The EPA raised the tolerance levels for glyphosate at Monsanto’s request in 2010. Food and Water Watch, a non-profit organization, petitioned against the move, asking the EPA to ignore industry pressure. Maximum residue levels for glyphosate in food are now at extremely high thresholds, undermining the supposed “scientific consensus” on the safety of genetically modified foods for human consumption. Urban populations are most likely to be exposed to glyphosate through diet, rather than through home use of herbicides or proximity to spraying sites. But tolerable pesticide levels in foods are determined nationally by the EPA, and international reports from the WHO may or may not be considered in policy decisions.

The Center for Science in the Public Interest recommends that farmers reduce their use of glyphosate and practice integrated weed management. Many farmers are already working to slow the spread of glyphosate-resistant weeds and reduce their use of herbicides. Farmers in the Midwest, for example, have even been able to combine herbicide-free weed management with no-till systems to prevent soil erosion. Glyphosate is prohibitedunder organic production systems, according to the U.S. Department of Agriculture national standards.

Continue Reading