Non-Hodgkin Lymphoma & Roundup

How Glyphosate Causes Non-Hodgkin Lymphoma

Non-Hodgkin lymphoma encompasses a group of over 60 blood cancers originating in lymphocytes — white blood cells that form a critical component of the immune system. Glyphosate, the active ingredient in Roundup, triggers NHL through a well-documented biological pathway. When absorbed through the skin during spraying or inhaled as a mist, glyphosate enters the bloodstream and reaches the bone marrow and lymph nodes where lymphocytes are produced and mature.

Once inside lymphoid tissue, glyphosate generates reactive oxygen species that cause oxidative DNA damage — specifically double-strand DNA breaks that overwhelm the cell's repair mechanisms. This genotoxic damage can activate oncogenes or disable tumor suppressor genes in lymphocyte precursor cells, initiating the uncontrolled cell division that characterizes cancer. The commercial Roundup formulation is more genotoxic than glyphosate alone because its surfactants — particularly polyethoxylated tallow amine (POEA) — dramatically increase cellular penetration.

The IARC Classification and Its Significance

In March 2015, the International Agency for Research on Cancer (IARC), a specialized agency of the World Health Organization, convened a Working Group of 17 independent scientists from 11 countries to evaluate the carcinogenicity of glyphosate. After reviewing the totality of publicly available evidence — epidemiological studies, animal bioassays, and mechanistic data — the Working Group classified glyphosate as "probably carcinogenic to humans" (Group 2A).

The classification was based on "sufficient evidence" of cancer in experimental animals and "limited evidence" of cancer in humans, with strong mechanistic evidence of genotoxicity. The human evidence centered on studies of agricultural workers in the United States, Canada, and Sweden showing elevated NHL risk among those with the highest cumulative glyphosate exposure. Critically, IARC evaluated only publicly available, peer-reviewed science — not industry-sponsored studies that Monsanto had submitted to regulators but never published.

Monsanto responded to the IARC classification with a coordinated campaign to discredit the agency, including ghostwriting published papers attacking IARC's methodology, lobbying to defund IARC's budget, and cultivating relationships with EPA officials who could provide favorable regulatory assessments.

Dose-Response Evidence

The epidemiological evidence demonstrates a clear dose-response relationship — the more Roundup a person used and the longer they used it, the greater their risk of developing NHL. The landmark meta-analysis by Zhang et al. (2019), published in Mutation Research, pooled six epidemiological studies and found a statistically significant 41 percent increase in NHL risk among the highest-exposed individuals (meta-RR = 1.41, 95% CI: 1.13-1.75).

The Agricultural Health Study (AHS), a massive prospective cohort study of over 50,000 licensed pesticide applicators conducted by the National Cancer Institute, found elevated NHL risk in the highest-exposure quartile of glyphosate users (HR = 1.36 for the longest duration of use). While the overall association was not statistically significant across all exposure levels, the trend of increasing risk with increasing exposure supports a causal relationship.

Individual plaintiff cases provide powerful illustrations of this dose-response pattern. Dewayne Johnson, the San Francisco groundskeeper who won the first Roundup trial, applied Roundup 20-30 times per year for several years before developing an aggressive form of NHL called mycosis fungoides. The Pilliod plaintiffs in Oakland each used Roundup for over 30 years before their diagnoses.

NHL Subtypes Most Strongly Linked to Glyphosate

Several specific NHL subtypes have been identified in the epidemiological literature as elevated among glyphosate-exposed populations. Diffuse large B-cell lymphoma (DLBCL) is the most common aggressive NHL subtype and the one most frequently seen in Roundup litigation. Follicular lymphoma, chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), and marginal zone lymphoma have also been associated with glyphosate exposure in multiple studies.

For purposes of Roundup litigation, any NHL diagnosis in a person with a history of Roundup use may support a legal claim. Expert oncology testimony evaluates whether the plaintiff's specific NHL subtype, exposure history, latency period, and absence of other risk factors are consistent with glyphosate causation.