Q: I normally use Round-up to remove weeds around my property. But now this weed killer is being called a carcinogen. Should I stop using it altogether? Is my health seriously in danger from the amount I have already used?
GG: The status quo on Round-up was shaken when the World Health Organization’s leading cancer team called IARC (International Agency for Research on Cancer) determined in 2015 that the main ingredient (glyphosate) is “probably carcinogenic to humans.” (http://www.iarc.fr/en/media-centre/iarcnews/pdf/Q&A_Glyphosate.pdf ) This was based upon testing showing an ability to damage DNA (genes) and somewhat mixed but nevertheless concerning cancer findings in animals and humans (non-Hodgkin’s lymphoma). The IARC evaluation touched off disagreement among various parties including regulators in Europe who viewed the same data differently, concluding not enough evidence that glyphosate is an actual cancer threat (https://www.theguardian.com/environment/2017/mar/15/no-cancer-risk-to-using-glyphosate-weedkiller-says-eu-watchdog ).
So, I certainly understand the public’s confusion over this issue. With the debate continuing, the prudent approach is to be cautious; look for other ways to remove weeds rather than tread into uncertain waters. Supporting this view is the fact that the State of California recently proposed a carcinogen listing for glyphosate (https://oehha.ca.gov/public-information/press-release/press-release-proposition-65/glyphosate-be-added-proposition-65#downloads ), the only regulatory body in the United States (EPA or otherwise) that I am aware of that has made such determination. The only thing preventing this determination going final are legal actions brought on by the pesticide manufacturer.
So instead of considering glyphosate as safe as anything else that comes from the garden shop, you may want to see it as more dubious and a less desirable choice to control weeds. There is always hand picking, mechanical edging (“Weedwacker”) and corn gluten or mulch to prevent weeds if you apply these materials before weeds emerge.
Regarding your personal health question from past uses of Round-Up, remember that we are exposed to many carcinogens in our diet, air and even in tap water. Relative to some of these agents, glyphosate’s cancer potency as calculated by California is quite low. Therefore, while prudent to go light on using this herbicide, it is unlikely you have caused a high risk for your health from past uses.
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Dr. Gary Ginsberg is a public health toxicologist in Connecticut and a lecturer at the Yale School of Public Health (Department of Environmental Health Sciences). He has written a book geared toward the general public, “What’s Toxic, What's Not,” and also has a website, whatstoxic.com, to answer questions about chemicals found in consumer products and in our homes.
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The Yale School of Public Health invites you to submit questions for Dr. Ginsberg as part of this recurring series. Contact us through Facebook or by e-mailing Michael Greenwood at michael.greenwood@yale.edu.