26
Aug
As Thyroid Cancer Cases Rise, Study Finds Pesticides Link
(Beyond Pesticides, August 26, 2022) New research from a team in California finds one-third of pesticides it reviewed — including glyphosate, paraquat dichloride, and oxyfluorfen — to be associated with the development of thyroid cancer. Researchers investigated the links between exposure to pesticides — including 29 that cause DNA cell damage — and the risk of this cancer. The researchers also find that in all the single-pollutant models they employed, paraquat dichloride — a widely used herbicide — was linked to this cancer. In 2021, Beyond Pesticides covered research by the U.S. National Institutes of Health (NIH) that demonstrated that exposures to lindane and metalaxyl also cause heightened risk of thyroid cancer. These study findings add to the already considerable concern about pervasive pesticide exposure — not only among farmers and applicators, but also in the general population.
It is worth noting that, in addition to elevated thyroid cancer risks, multiple pesticides can cause other health damage. Paraquat is also acutely toxic, and can cause longer-term reproductive, renal, and hepatic damage to humans; it is toxic to birds, fish, and other aquatic organisms, and slightly so to honeybees. Glyphosate, as Beyond Pesticides has written frequently, is carcinogenic, and is associated with human, biotic, and ecosystem harm. Oxyfluorfen exposures deliver risk of reproductive, renal, hepatic, and developmental damage to humans, and toxicity to fish and other aquatic creatures.
The research team, from the University of California (UC) Los Angeles Health Sciences, published its study in The Journal of Clinical Endocrinology & Metabolism. The authors say it “provides the first evidence supporting the hypothesis that residential pesticide exposure from agricultural use is associated with an increased risk of thyroid cancer” [emphasis by Beyond Pesticides].
Thyroid cancer is one of the few cancers whose incidence has risen in recent decades — by 3% since 1992, according to Science Daily’s reporting on the California research. The American Thyroid Association also notes the dramatic increase in incidence, and says thyroid cancer is now the fastest-growing cancer in women, with most of that increase representing papillary thyroid cancer (the most common and slowest-growing of the subtypes).
Some of the increased incidence is likely attributable to better detection methods and increased use of imaging in healthcare. And genetics certainly play a role in vulnerability to thyroid disease generally, but widespread exposures to certain pesticides — whether through residues in the food supply, occupational exposures, or as in the subject study, residence in an agricultural production area — appear to pose a real risk for the development of thyroid cancers.
A Scientific American article notes that 20 years ago, a study published in the American Journal of Epidemiology found that “Iowa and North Carolina women married to men using such pesticides as aldrin, DDT and lindane were at much higher risk of developing thyroid disease than women in non-agricultural areas” — at an incidence rate of 12.5%, compared to a 1–8% rate in the general population. [Note: the organochlorine pesticides aldrin and DDT were banned by the U.S. Environmental Protection Agency in 1974 and 1972, respectively.]
Beyond Pesticides was quoted in that study article: “It’s not just farm women who should worry. Trace amounts of chemical pesticides and fertilizers most certainly end up in some of the food we eat. The nonprofit group Beyond Pesticides warns that some 60 percent of pesticides used today have been shown to affect the thyroid gland’s production of T3 and T4 hormones. Commercially available insecticides and fungicides have also been implicated.”
The UC researchers did not need to stray far for their study; they focused on residents of California, which has a huge agricultural sector that uses roughly 25% of all pesticides deployed in the U.S. (The state has been experiencing an uptick in advanced thyroid cancer diagnoses.) The team used data from the California Cancer Registry (for 1999–2012) to examine residential exposure to 29 agricultural pesticides that cause DNA damage or endocrine disruption (ED), and used GIS (geographic information system) data to identify reasonable exposure estimates for each participant.
The study sample comprised 2,067 thyroid cancer cases and 1,003 control participants. All study participants were at least 35 years old, had a thyroid cancer diagnosis, and lived in the study’s target geographic area at the time of diagnosis. Control subjects were also at least 35, lived in that same geographic area, and had been living in California for at least five years before the research interview.
Principal investigator Avital Harari, M.D., pointed to the increased incidence of thyroid cancer and implications of the study’s findings. She said, “[T]he risk of advanced thyroid cancers, which can increase risk of mortality and cancer recurrence, has been found to be higher in the state of California as compared to other states. Therefore, it is essential to elucidate risk factors for getting thyroid cancer and understand potentially alterable causes of this disease in order to decrease risks for future generations. . . . Our research suggests several novel associations between pesticide exposure and increased risk of thyroid cancer. Specifically, exposure to the pesticide paraquat is positively associated with thyroid cancer risk.” She cited additional findings: that exposures to other pesticides, in combination with those to paraquat (in multi-pollutant models) also suggest increase thyroid cancer risk, and that exposures (over a 20-year period) to a larger number of unique pesticides proportionately increase the cancer risk.
Most previous research has focused on the role of endocrine-disrupting pesticides in the development of thyroid cancer, or disease development among those exposed occupationally (e.g., in this research, this, and this). The pesticides metalaxyl and lindane, both established endocrine disruptors, have been implicated in heightened thyroid cancer risk across multiple studies, including the NIH study mentioned above. See more, older research on Beyond Pesticides’ Pesticide-Induced Diseases Database webpage, in the section on thyroid cancer.
The Science Daily coverage of the UC study explains further that “certain pesticides are established mutagens or have been shown to induce tumor growth and chromosomal abnormalities in vitro. These include glyphosate — the active ingredient in widely used herbicides — and pesticides that induce DNA cell damage in vitro. Pesticides also can alter thyroid hormone production, which has been associated with thyroid cancer risk.”
The relevant methods of action of pesticides re: thyroid cancer are the mutagenic or the (less direct) endocrine disrupting. The actions of endocrine disruptors were laid out by Beyond Pesticides in 2021: “‘The ingredients in many pesticides (and in many consumer products) act as endocrine disruptors in humans and other animals in several ways. They may: (1) mimic actions of hormones the body produces (e.g., estrogen or testosterone), causing reactions similar to those generated by the naturally produced hormones; (2) block hormone receptor cells, thereby preventing the actions of natural hormones; or (3) affect the synthesis, transport, metabolism, and/or excretion of hormones, thus altering the concentrations of natural hormones in tissues or at receptor sites.’ Pesticides acting as EDs can, through disruption of the activities in #3, distort hormone levels in the body.”
Threats to public health — in the subject study, from pesticides associated with development of thyroid cancer, but from toxic pesticides and chemicals far more broadly — are not being adequately mitigated by governments at federal, state, or local levels. And those threats are certainly not front and center in the business models of the agrochemical companies that manufacture pesticide products. Thus, the onus for changing our system of allowing toxic chemical use without adequate, precautionary, and protective review falls on the public and its organizational health, environment, climate (and other) advocates — such as Beyond Pesticides and many, many others. To that end, we invite everyone to participate in our 2022 National Forum Series, beginning September 15.
The event will focus on the existential problems associated with current public health and environmental crises — public health threats, biodiversity collapse, and the climate emergency — and chart a path for solving these urgent issues. Our involvement, whether as professionals, lay people, elected officials, or concerned advocates, is critical to enhancing public understanding of the science that underlies these crises, and to motivating action on the local, state, and national levels.
These crises arise from a confluence of issues, and are harming all life and every environment on the planet. The need for carefully defined sustainable land management, building and household practices, and consumer and industrial products is urgent. The 2022 National Forum Series launches Beyond Pesticides’ campaign to eliminate fossil fuel-based pesticide use within the next decade — putting a stop to toxic emissions, exposure, and residues, while embracing an organic systems approach that is holistic and respectful of life.
Source: https://www.sciencedaily.com/releases/2022/08/220818175207.htm
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
