What’s Going on With Roundup®?

High profile lawsuits in California have successfully sued Monsanto, the original manufacturer of Roundup. The assertion was that their clients' long-term use of Roundup® caused the plaintiffs' cancer.

I am not a toxicologist, I am an extension forester and a faculty member at a land-grant university who is committed to looking objectively at scientific data and making recommendations. In this case the lawsuits and media do not seem to match with the science.

So why is glyphosate so important? Controlling undesirable vegetation in forestry is critical to assuring a healthy forest, establishing forest regeneration, creating wildlife habitat, and controlling invasive plants. Controlling undesirable vegetation is possible by using prescribed fire, mechanical tools and equipment, and possibly even goats, but herbicides are much more effective and efficient. In fact, mechanical control methods may pose a greater safety threat for human injury.

Glyphosate is a type of herbicide that has an active ingredient that interferes with plant growth. Glyphosate works by blocking the activity of an enzyme in one of the biochemical processes so that the plant cannot grow. The process is found only in plants and not in humans and other animals. Monsanto marketed glyphosate as Roundup® in 1974 and held the patent on the chemical until 2000. The patent expired in 2000, allowing companies to legally produce and sell glyphosate, and at lower cost, which is where we are today.

Glyphosate is found in many formulations and trade names and is sold in big box stores and through agricultural dealers. It is widely used in forestry, agriculture, and residential markets to control unwanted vegetation. It works on all types of plants, becomes inactive in the soil, breaks down quickly in sunlight, and poses little danger to the environment. Glyphosate, like every chemical active ingredient for any herbicide, goes through an assessment by the Environmental Protection Agency (EPA), which determined it to be safe when used "according to the label directions." The label is the law.

Some recent court verdicts in California have found glyphosate responsible for causing non-Hodgkin's lymphoma (NHL). Scientists do not really know what causes this cancer. If glyphosate caused cancer at realistic exposure levels, then farmers and other applicators would be the first to show this effect. The largest study ever published (see references), looking at farmers and other applicators, found no association between glyphosate and solid tumors, including NHL.

Anti-glyphosate advocates point to the 2015 report from the International Agency for Research on Cancer (IARC, www.iarc.fr), an arm of the World Health Organization. The report labeled glyphosate a probable human carcinogen, a determination that was surprising to many. IARC responded to critics by clarifying their intent - to identify potential hazards. They asked, "Can it cause cancer under any circum-stance?" They defer to others to do risk assessment based on expected levels of exposure and background cancer rates. Most governments (US, Europe, Australia, New Zealand, and Canada) have published risk assessments about glyphosate, finding it unlikely to cause cancer in humans when used according to label directions.

The EPA under the past four administrations found glyphosate to pose no risk to human health and was not a carcinogen. Likewise, the European Chemicals Agency determined glyphosate was not a carcinogen, and in 2018 the European Food Safety Authority determined the current exposure levels are not expected to pose a risk to human health.

The IARC determination put the following items in the same "probable human carcinogens" category as glyphosate: consumption of red meat, drinking very hot beverages, high temperature frying emissions, late-night shift work, hairdresser workplace exposure. "Known human carcinogens" on their list included processed meat, alcoholic beverages, and sunlight. Hazard identification is only the first step in assessing risk.

Glyphosate use in forest management is critical for controlling undesirable vegetation and using it according to labeled directions minimizes risk. As with any pesticide, risk is reduced by using the Personal Protection Equipment detailed on the product label, such as proper clothing, gloves, eye protection, etc. To do otherwise is using the material illegally. Determinations by courts and lawyers do not necessarily reflect the science on this subject. I encourage you to review the references provided below and make your own decision. Recognize that glyphosate can be a useful tool when combating competing vegetation.

Information for this article was drawn from the following sources:
* Coyle, D. R. (2019). Glyphosate: Cause for Concern?. Forest Landowner, November/December 2019, 25-38.
* Buhl, K.& Bubl, C. (2018). Glyphosate Questions & Answers. Oregon Master Gardener Coordinators. OSU Extension Master Gardener Program.
* Andreotti, G., Koutros, S., Hofmann, J.N., Sandler, D.P., Lubin, J.H., Lynch, C.F., … Beane Freeman, L.E. (2018). Glyphosate Use and Cancer Incidence in the Agricultural Health Study. JNCI: Journal of the National Cancer Institute, 110(5), 509-516.
* Kniss, A. (2018) Glyphosate and cancer - revisited.

(Reprinted from Branching Out newsletter, Fall 2019, with permission from the author)