In June 2020, after decades of back and forth over whether a key ingredient in the herbicide Roundup causes cancer in the agricultural workers and home gardeners who use it, Bayer agreed to spend $10 billion to settle the approximately 95,000 lawsuits that had accrued over time. The lawsuits are primarily against Roundup’s original producer, Monsanto, which Bayer purchased in 2018.

While the settlement is noteworthy in its scale, it also stands largely alone as a tacit acknowledgement of environmental factors that may cause non-Hodgkin lymphoma (NHL). There’s been a spate of disconnected scientific research, since the 1980s in particular, cataloguing the various carcinogenic risks that seem to face populations with documented cancer diagnoses — but the research has been piecemeal and is often done at a small scale, producing results that sometimes have conflicting conclusions —so the findings of these studies alone often fail to result in any meaningful public health settlements. And even when certain individuals do win cases, it is common that the money actually paid out to plaintiffs is significantly less than the amounts ordered to be paid in original judgments.

A recent review in Cancer Epidemiology, Biomarkers, and Prevention brings together many recent and historical studies in an attempt to better identify patterns that each individual, smaller study couldn’t on itsown.1 The review looks at methodologies, NHL subtypes, and more recent genetic factors, ultimately calling for more hyper-focused research on the latter: “It is essential to account for the unique genetic abnormalities observed in different NHL subtypes when attempting to establish the causality of chemical agents such as pesticides, herbicides, and organic solvents,” the review reads.

The very same Roundup that is the subject of Bayer’s recent settlement occupies a considerable portion of the review because it’s such a profound and high-profile example of the type of stalemate that conflicting research can cause. The alleged potential chemical culprit in Roundup is glyphosate, which can stop weed growth in its tracks, but can also end up in the human diet through produce that has been in the herbicide’s path, or even in meat if livestock eat produce from fields treated with the chemical. In 2015, authors writing on behalf of the International Agency for Research on Cancer Monograph Working Group (IARC) issued a Lancet study asserting the carcinogenic nature of glyphosate,2 but a mere year later the World Health Organization (WHO), in partnership with the Food and Agriculture Organization of the United Nations, walked that conclusion back, saying instead that “glyphosate is unlikely to pose a carcinogenic risk to humans from exposure through the diet.”3


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The review also looked at the intriguing impact of hair dyes on NHL diagnoses. In the early 1980s, hair dyes were reformulated to exclude a number of potentially risky chemicals that were thought to cause cancer, creating a compelling before-and-after scenario for researchers: Look at populations who consistently dyed their hair prior to the early 1980s compared with those who only began dying their hair later on, and you might see a pattern emerge that could make a case for environmental ties to NHL.