13
Dec
Estrogen-Mediated Cancers in Humans Have Links to Endocrine Disrupting Pesticides
(Beyond Pesticides, December 13, 2022) Pesticides have a long history associated with hormone (endocrine)-disrupting properties that induce various molecular changes, prompting disease development. Adding to the science, a review published in Environmental Exposure, Biomonitoring and Exposure Assessment highlights how specific estrogen-mimicking pesticides increase the risk of disease, particularly hormone-related cancers among women (i.e., breast, ovarian, endometrial cancer) and men (i.e., testicular, prostate cancer). Like pesticides, endocrine disruptors are xenobiotic (i.e., chemical substances foreign to an organism or ecosystem). Many reports demonstrate that exposure to endocrine-disrupting chemicals can adversely affect human, animal—and thus environmental—health by altering the natural bodily hormones responsible for conventional reproductive, physical, and mental development. Endocrine disruption can lead to several health problems, including hormone-related cancer development (i.e., thyroid, breast, ovarian, prostate, testicular), reproductive dysfunction, and diabetes/obesity that can span generations. Therefore, studies related to pesticides and endocrine disruption help scientists understand the underlying mechanisms that indirectly or directly cause cancer, among other health issues.
Pesticides are one of the most potent xeno-estrogenic compounds, as estrogenic strength and environmental half-life exceed those of other xeno-estrogenic compounds. Focusing on organochlorine pesticides (OCs), the study evaluates the chemical effects on the physiological (anatomic) system to increase cancer risk. Using human studies, researchers assessed how estrogen-medicated cancer develops in women and men. Various OCs, including aldrin, dieldrin, endosulfan, HCH, DDT, 2,4,5-trichlorophenoxyacetic acid, phenoxy acid herbicides, and methoxychlor, have associations with hormone-related cancers. The International Agency for Research on Cancer (IARC) classifies many of these chemicals as potent carcinogens in animal studies. Cancer development also depends on genetic susceptibility, as impaired genes responsible for xenobiotic detoxification (elimination) increase disease risk sensitivity.
It is evident that OCs’ hormone-like activity disrupts natural estrogen function, which is concerning since these chemicals stay in the environment for extended periods (from years to decades). Despite the ban on many OCs across the globe, these chemicals remain in the environment. Many OCs can exist in the body for at least three to six years, in soil for decades, and in water for at least a century. Moreover, consumption of food and water resources contaminated with OCs can cause these chemicals to bioaccumulate in the body, resulting in the biomagnification of OCs.
The mechanisms involved in the endocrine-disrupting potential of OCs include four different actions:
- “Mimicking the effect of endogenous steroidal hormones (androgens and estrogens).
- Antagonizing steroidal hormones.
- Altering the synthesis and metabolism of endogenous steroidal hormones.
- Modifying hormone receptor expression in different tissues.”
The review notes the association between hormone-related cancers and OCs. Studies document excess estrogen can promote breast, ovarian, and endometrial cancers among women and elevate testicular and prostate cancer among men. In women, numerous studies link exposure to OC contaminants (e.g., DDT and its metabolites [DDE and DDD], heptachlor, dieldrin, and hexacyclohexane) as the prime cause of higher breast cancer risk, since these chemicals stimulate estrogenic activity. Nearly 40 percent of breast cancer incidents have direct links to environmental factors (e.g., chemical exposure) in women over 30. Although the review notes the mechanisms involved in increasing breast cancer risk are unclear, studies suggest OCs downregulate the expression of estrogen receptors (ER, a common event in many breasts cancer cases) through disruption of essential pathways. In men, although estrogen’s role in male cancer risk is much less understood, gestational and neonatal exposure to estrogen-related compounds significantly contribute to testicular cancer risk in men. Regarding OCs, studies find both work-related and non-worker-related exposure increase testicular dysfunction risk 1.29-fold, promoting testicular cancer. Furthermore, the review assessed the potential relationship of xeno-estrogenic pesticides with prostate cancer risk. Although direct connections between xeno-estrogenic pesticides and prostate cancer are lacking in establishment, animal studies suggest endocrine-disrupting chemicals can alter prostate stem cells, elevating prostate cancer risk. Additionally, maternal exposure to low doses of xeno-estrogens during gestation increases the weight of the prostate in male offspring. Increased prostate weight is a characteristic of a prostate disorder that can lead to prostate cancer. In particular, higher levels of OCs influence prostate weight, which is consistent in patients with more aggressive forms of prostate cancer.
The connection between pesticides and associated cancer risks is not a new finding. Many pesticides are “known or probable” carcinogens (cancer-causing agents), and widespread uses only amplify chemical hazards, adversely affecting human health. Several studies link pesticide use and residue to various cancers, from the more prevalent breast cancer to the rare kidney cancer, nephroblastoma (Wilms’ tumor). Sixty-six percent of all cancers have links to environmental factors, especially in occupations of high chemical use. At least 45 different cancers have associations with work-related chemical exposure. Although the link between agricultural practices and pesticide-related illnesses is stark, over 63 percent of commonly used lawn pesticides and 70 percent of commonly used school pesticides have links to cancer. U.S. National Institutes of Health’s National Cancer Institute also finds many cancer-causing substances are endocrine disruptors. The entire endocrine system directly affects traditional endocrine glands and their hormones and receptors (i.e., estrogens, anti-androgens, thyroid hormones), greatly influencing hormone cancer incidents among humans (e.g., breast, prostate, and thyroid cancers). Several studies and reports, including U.S. Environmental Protection Agency (EPA) data, identify hundreds of chemicals as influential factors associated with hormone-related cancer risk. There are grave concerns over exposure to endocrine (hormone) disrupting chemicals and pollutants that produce adverse health effects. Considering not only OCs, but over 296 chemicals in consumer products can increase breast cancer risk through endocrine disruption, it is essential to understand how chemical exposure impacts chronic disease occurrence.
This review is one of the first to consider all-gender estrogen-mediated cancer risk modification by xeno-estrogenic OCs. However, OCs are not the only chemical associated with endocrine-disrupting mechanisms. The World Health Organization (WHO), European Union (EU), and endocrine disruptor expert Theo Colborn, Ph.D. (deceased), classify over 55 to 177 chemical compounds as endocrine disruptors, including various household products like detergents, disinfectants, plastics, and pesticides. Unlike many OCs, these chemicals are still in use across most parts of the world.
Previous studies demonstrate the sex-specific effect of endocrine-disrupting pesticide exposure. In 2017, scientists presented a study at the 99th meeting of the Endocrine Society, demonstrating instances of early onset puberty in boys after exposure to common pyrethroid insecticide, which exhibits endocrine-disrupting properties that interfere with the proper regulation of the human body’s hormonal system. Furthermore, a 2021 study demonstrates that exposure to current-use pesticides, like organophosphates, poses a greater health risk to women.
The review concludes, “These chemicals [xeno-estrogenic pesticides] must be completely phased out and replaced with less toxic and affordable alternatives that have negligible adverse health effects on mammalian systems.…[B]reast cancer in females and prostate cancer in males have become the top causes of morbidity and mortality, and both are estrogen-mediated cancers. More studies are needed to find out how much this increased incidence can be attributed to such harmful environmental factors.”
There is a lack of understanding of the etiology of pesticide-induced diseases, including predictable lag time between chemical exposure, health impacts, and epidemiological data. Exposure to pesticides can increase the risk of developing chronic illnesses that may be rare and disproportionately impact various populations. Cancer is one of the leading causes of death worldwide, with over eight million people succumbing to the disease every year. Notably, IARC predicts an increase in new cancer cases from 19.3 million to 30.2 million per year by 2040. Therefore, studies related to pesticides and cancer will aid in understanding the underlying mechanisms that cause the disease.
It is essential to understand the health implications of pesticide use and exposure for humans, particularly when pesticides increase chronic disease risk. Beyond Pesticides tracks the most recent news and studies on pesticides and related topics through the Daily News Blog and Pesticide-Induced Diseases Database (PIDD). For more information on the adverse effects of pesticides on human health, see PIDD pages on cancer, endocrine disruption, and other diseases.
Moreover, proper prevention practices, like buying, growing, and supporting organics, can eliminate exposure to toxic pesticides. Organic agriculture has many health and environmental benefits, given that it curtails the need for chemical-intensive agricultural practices. Regenerative organic agriculture nurtures soil health through organic carbon sequestration, while preventing pests and generating a higher return than chemical-intensive agriculture. For more information on why organic is the right choice, see the Beyond Pesticides webpage, Health Benefits of Organic Agriculture.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Environmental Exposure, Biomonitoring, and Exposure Assessment
