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Guest Opinion: Glyphosate poses health risks

Recently a highly respected medical journal (The Lancet Oncology) published the scientific declaration from the International Agency for Research on Cancer (a branch of the World Health Organization) that glyphosate, the most commonly used herbicide in the world, is a “probable human carcinogen.”

Glyphosate is the active ingredient in some 750 herbicide products, such as Monsanto’s Roundup. Its use in the U.S. has increased over 1,200 percent in the past 18 years due in large part to the increased cultivation of glyphosate-tolerant genetically engineered (GE) crops. American scientists have found glyphosate in our water, air and foods — including soy-based baby formulas and even U.S. honey, while others have documented glyphosate in human urine, human breast milk and in livestock.

A partial or total ban and serious discussions on discontinuing the use of glyphosate-based herbicides was recently instituted in at least eight countries. In the U.S. the conversation has been more muted, but there is every reason to seriously re-think our use of glyphosate in light of the new scientific evidence and ask whether we can reduce glyphosate exposure in our own community.

The declaration as Category 2A (probably carcinogenic to humans) is used when “there is limited evidence of carcinogenicity in humans and sufficient evidence of carcinogenicity in experimental animals.” The finding that glyphosate is a probable carcinogen was based on a unanimous vote of 17 medical and other cancer research experts from 11 countries, heavily weighted by American scientists with the National Cancer Institute, the Environmental Protection Agency, the National Institute of Environmental Health Sciences and several American universities).

Other well-known chemicals in the “probable human carcinogen” category include high-impact chemicals such as DDT, styrene oxide, TCE (used in dry cleaning), and the insecticide malathion.

Animals exposed to chemicals listed as “probable carcinogens” rarely exhibit rapid tumor responses or serious acute illnesses unless very large amounts of the chemicals are ingested. Of course, people do not generally consume large quantities of glyphosate at any one time. Instead, we and our families are exposed to glyphosate over our lifetime as a result of herbicide residue on GE foods, spraying and other environmental exposures. It is always tough to prove the effects of long-term chronic exposure to damaging chemicals, and it should not surprise anyone that it took more than 40 years for the world’s top scientists to agree that glyphosate is likely carcinogenic.

Scientists, however, have now documented a host of concerns about glyphosate risks including DNA and chromosomal damage to residents following nearby commercial agricultural spraying of glyphosate. Molecular studies also found that glyphosate triggered the growth of cancerous breast tissue cells and may contribute to birth defects in animals. After reviewing multiple lines of scientific evidence, Dr. Aaron Blair, a retired epidemiologist from the U.S. National Cancer Institute who was chairman of the IARC group, summed up the new scientific consensus about the risks of glyphosate, explaining, “All three lines of evidence (humans, animals, lab data) sort of said the same thing, which is why we ought to be concerned about this.”

The “precautionary principle” is the idea that even in the absence of scientific certainty we are wise to take precautions based on the information we do have about certain risks. For example, even decades before there was unanimous scientific consensus that smoking caused lung cancer, there was more than enough evidence to suggest people would be wise to avoid smoking and smoke exposure.

When a collection of the world’s top scientists find that there is “a plausible risk” with glyphosate exposures it makes sense at the local level to consider steps to reduce the daily level of exposure that we and our children receive. A first step could be discontinuing the use of glyphosate in public places, such as schools, parks and other common-sense places where glyphosate affects the most vulnerable among us: the very young, the elderly and the chronically ill. While a significant source of glyphosate exposure may be residues on genetically engineered crops, fortunately it is also now easier than ever to eat locally grown foods that have not been engineered for heavy glyphosate spraying.

Ray Seidler, Ph.D., of Ashland, is a professor of microbiology and a retired senior scientist and team leader for the Environmental Protection Agency's biosafety program.