As one of the most widely used pesticides in the US, glyphosate has long been regarded as an efficient weed killer for residential and agricultural practices. The substance is the active ingredient in popular products like Roundup, a herbicide developed in 1974 and marketed by Monsanto, which Bayer AG currently owns.

Despite the herbicidal qualities that make glyphosate an optimal tool for pest control, the substance’s health hazard potential has long been suspected and documented through a growing body of clinical research. A recent UCLA study of long-term pesticide use in California uncovered a worrying correlation between residential exposure to glyphosate and thyroid cancer.

Links to thyroid cancer and hormone disruptions

Located at the base of the neck under the Adam’s apple, the thyroid is a gland shaped like a butterfly that produces hormones which regulate bodily functions like heart rate, blood pressure, body temperature, oxygen consumption, and metabolism. When thyroid cells suffer DNA changes that increase their growth rate, they can accumulate into cancerous tumors.

Thyroid cancer (TC) is usually asymptomatic and highly treatable in its early stages, with some individuals not even realizing they suffer from the condition until it advances and causes more obvious signs and symptoms like:

• Neck swelling and pain (sometimes accompanied by lumps)
• Voice change and hoarseness
• Trouble with swallowing and breathing

Notably, while TC’s causes are not entirely understood, the condition is 3 times more prevalent in women, usually diagnosed at earlier ages (40s and 50s) than in men (60s and 70s). The most common risks associated with thyroid cancer include inherited genetic factors, low-iodine diets, higher body mass index, and exposure to radiation. The American Cancer Society estimates that 43,800 cases of TC will be diagnosed in 2022, with 2,230 expected fatalities.

Although research into the precise causes of TC is ongoing, exposure to pesticides has long been suspected as a contributing factor. One chemical of particular concern is glyphosate, the primary compound in Roundup and other similar herbicides, which the International Agency for Research on Cancer (part of the World Health Organization) listed as probably carcinogenic to humans in 2015.

The 2022 case-control study from UCLA analyzed TC cases reported in California from 1999 to 2012 and examined residential exposure to over two-dozen agricultural pesticides known to produce genetic damage and hormonal (endocrine) disruptions. Chronic exposure to glyphosate was associated with a 33 percent higher risk of thyroid cancer.

The study’s results are especially concerning given the increasing rate of TC fatalities in California and the condition’s consistent 3 percent annual increase over the past three decades in the US. Recent studies also indicate that exposure to low concentrations of Roundup (deemed acceptable) resulted in significant thyroid cell death and that glyphosate exhibits 8 out of 10 characteristics of endocrine-disrupting chemicals. Furthermore, the positive correlation between higher glyphosate use in US agriculture and rising TC incidence has been noted in even earlier research analyzing the pesticide’s hazard potential.

Exposure to glyphosate is associated with a broader range of diseases, including several types of cancers like non-Hodgkin’s lymphoma (41 percent increased risks). Despite mounting evidence to the contrary, manufacturers have long maintained their glyphosate-based products’ safety, even though recent discoveries indicate they were aware of the compound’s health risks since the 80s.

A pledge to replace glyphosate-based products in 2023

After Bayer purchased Monsanto in 2018 for $63 billion, the German-based company also took on the legal ramifications of owning Roundup, spending $10.9 billion to settle tens of thousands of claims by 2020. On July 29, 2021, the growing wave of litigation determined Bayer to announce it would replace glyphosate-based products intended for the US lawn and garden market with new formulations in January 2023, a promise that the company so far seems to be on track to fulfill.

Still denying links to cancer, Bayer’s decision to pull Roundup off the market for residential use is made exclusively to manage litigation risk. Meanwhile, the replacement of glyphosate in a narrow range of products meant for residential use dismisses the more pronounced risks of Roundup’s commercial agricultural applications.

Even though Bayer hasn’t officially disclosed the alternatives considered for its new formulations, possible options may include pelargonic acid, acetic acid, or glufosinate-ammonium.  However, even if these potential substitutes might seem safer options, they carry their own inherent exposure risks, with the World Health Organization actually categorizing glufosinate-ammonium as more dangerous than glyphosate.

Until further regulations are elaborated to reduce glyphosate’s widespread use for commercial purposes, exposed individuals are more likely to benefit by transitioning to greener, non-toxic approaches. Farmers can employ ecologically-friendly and sustainable practices like regular crop rotation, companion planting, and opting for pest-resistant plant strains, while mechanical weeding and organic biopesticides are recommended non-toxic alternatives for residential gardening and lawn care.