17
Dec
Study Links Numerous Chemical Families of Pesticides to Endocrine Disrupting Effects, Including Obesity
(Beyond Pesticides, December 17, 2024) A systematic review of studies on pesticides as endocrine-disrupting chemicals (EDCs) on body weight, published in Biomedicines, evaluates 36 clinical and preclinical studies and links their agricultural use to obesity. The authors, with the lead researchers from the School of Medicine and Health Sciences at Catholic University of Valencia San Vincente, Valencia, Spain, assess studies on a range of pesticides, including organophosphates, pyrethroids, neonicotinoids, and others. In addition to concluding that the EDCs promote obesity, they report that the chemicals cause “other anthropometric changes by altering lipid and glucose metabolism, modifying genes, or altering hormone levels such as leptin.â€
Endocrine disruption and obesity are public health concerns, and there is a wide body of science linking pesticide exposure to these effects (see more here). “Obesity is considered to be a worldwide pandemic that leads to an increase in medical costs and thus becomes a public health problem,†the researchers share. They continue, “[Obesity] is also associated with the increased production of environmental chemicals, also called environmental obesogens, used mainly in agriculture, as disease vector control, helping to prevent harmful effects caused by fungi, bacteria, or even pests, using pesticides, insecticides, and herbicides, or endocrine disruptors (ED), which interfere in different processes.â€
In analyzing five human cross-sectional studies, 24 animal studies, and seven in vitro studies published since 2000, the authors investigate how environmental and dietary pesticide exposure is associated with anthropometric parameters, such as weight and body mass index (BMI), and metabolic changes that promote fat accumulation and adipogenesis (the process of creating fat cells).
Within the observational human studies, the pesticides evaluated span many different chemical families. These include: 2,4,5-dichlorophenol (2,4-D and 2,5-D, phenoxy herbicides); imidacloprid, acetamiprid, and clothianidin (neonicotinoid insecticides); glyphosate (phosphanoglycine herbicide); diuron (dimethylurea herbicide); chlorpyrifos (organophosphate insecticide); permethrin (synthetic pyrethroid insecticide); mancozeb and maneb (ethylene bisdithiocarbamate fungicides); carbendazim and thiophanate (carbamate fungicides); and benomyl (benzimidazole fungicide). The studies compare urinary concentrations of the pesticides to weight gain and obesity. Three of the studies use data from the National Health and Nutrition Examination Survey (NHANES) for children and adolescents aged 6–19 years and adults aged 20–85 years.
“Participants with obesity were found to have higher urinary concentrations of 2,4-D and 2,5-D. Higher concentrations of these pesticides were associated with increased BMI and waist circumference,†the authors note. “As in children, the adult study showed a higher prevalence of obesity with higher urinary levels of 2,4-D and 2,5-D.†The additional studies find that carbendazim, thiophanate, benomyl, metalaxyl, propineb, and chlorpyrifos show a statistically significant association with obesity prevalence.
In the studies on animals, 17 focus on species of mice while the other seven use rats, with nine of the 24 studies investigating chlorpyrifos. “[T]o evaluate the effect of pesticides on obesity, BMI, waist circumference, weight gain, and fat mass were the main measures used. In addition, several studies assessed biochemical parameters such as insulin levels, blood glucose, serum leptin, thyroid hormones, and lipid profile, as well as biomarkers and indicators of lipid metabolism,†the researchers explain.
As a result, chlorpyrifos exposure is associated with increased body mass, adiposity, impaired glucose tolerance, and insulin sensitivity in mice and rats when combined with a high-fat diet. It is also observed to alter gut microbiota, which can have “a significant effect on weight gain, serum-free lipopolysaccharide concentrations, and fasting glucose. Furthermore, this alteration could promote body weight gain, insulin resistance, and glucose intolerance,†the authors say.
Chlorpyrifos also alters intestinal permeability and causes an increase in lipopolysaccharide levels, “which could induce chronic inflammation and promote the development of insulin resistance and obesity. In addition, chlorpyrifos exposure may alter leptin levels, which could be associated with increased fat deposition, and a strong correlation was found between increased leptin levels and weight gain,†the researchers find.
Additional effects are noted with exposure to the organophosphate malathion (increased body weight and serum glucose levels in mice), synthetic pyrethroids bifenthrin and permethrin (significantly increased body weight, fat mass, and serum cholesterol levels in mice), and lambda-cyhalothrin and cypermethrin (increased plasma concentrations of free fatty acids, increased cholesterol, and increased hepatic triglyceride levels).
In mice, exposure to the neonicotinoid imidacloprid causes significant increases in body weight and adipose tissue, as well as increased serum glucose levels, insulin, and leptin levels, while exposure to thiamethoxam results in “[i]ncreased epididymal and retroperitoneal adipose tissue in males, increased omental adipose tissue in females, and increased adipocyte size.†Both imidacloprid and thiamethoxam exposure leads to increased levels of TG [triglycerides], free fatty acids, and cholesterol in male mice.
Seven in vitro studies evaluate the “effects of pesticides on the anatomy and physiology of hepatocytes and adipocytes” and the prevalence of obesity. Regarding hepatocytes, which are cells primarily in the liver that play a role in metabolism, cis-Bifenthrin is found to increase intracellular triglyceride levels in these cells after just 24 hours.
Adipocytes, fat cells found in adipose tissue, experience impacts from multiple pesticides:
- β-Cypermethrin induces autophagy and adipogenesis by increasing oxidative stress.
- Exposure to quizalofop-p-ethyl, dicamba, and isoxaflutole promotes lipid accumulation.
- Chlorpyrifos leads to a “significant increase in the number of differentiated adipocytes and their internal lipid storage capacity. In addition, there was an increase in the expression of PPARγ and C/EBPα transcription factors involved in the function of adipogenesis.â€
- Treatment with fipronil significantly increases the triglyceride content in adipocytes, as well as causes changes in differentiation and lipid metabolism within the cells.
- Adipocytes exposed to imidacloprid show an increase in fat droplets, as well as a higher accumulation of triglycerides and enzymes responsible for lipogenesis (a metabolic process for creating fat).
- The carbamate fenoxycarb increases lipid accumulation and reduces adipocyte viability at high concentrations. This pesticide also causes an increase in the expression of genes, PPARγ and FATP1, which are involved in fat transport.
- Pyriproxyfen exposure induces an increase in lipid deposition.
“This systematic review shows the association between pesticide use and a greater tendency to be overweight and obese,†the authors conclude. In highlighting the disruption of biological processes, such as metabolism, and changes in the expression levels of genes, more evidence of pesticides as EDCs is added to existing scientific literature. Â
“EDs have been implicated in a variety of adverse effects, including neurotoxicity, autism spectrum disorder and developmental delays in children after prenatal exposure, impaired behavior, learning, memory, attention, sensation and neurodevelopment, depression and anxiety in children, reduced fertility in women due to increased polycystic ovarian syndrome or premature ovarian failure, and even breast or vaginal cancer,†the researchers state. “EDs can also affect fertility in men, especially in the case of some pesticides. They are also associated with endocrine disruption, causing thyroid dysfunction, affecting both iodine uptake and thyroid hormone metabolism, and interfering with insulin physiology, becoming a risk factor for the development of diabetes.â€
As the researchers mention, “The World Health Organization (WHO) has also recognized EDCs as a public health priority, emphasizing the need for improved regulatory strategies and public education to protect vulnerable populations… Government agencies and regulators need to consider these findings to develop stronger regulations and promote good agricultural practices that protect both the environment and human health.â€
While many countries have bans in place for some EDCs, pesticides in the U.S. are still registered and available on the market without a regulatory framework for evaluating endocrine-disrupting effects. The long half-life of EDCs is also of concern as levels can be detected in the environment and within the body for many years after use. With agricultural pesticides such as EDCs, there are high risks associated with both environmental and dietary exposure.
“There is evidence that some pesticides can be endocrine disruptors and, among some of their effects, we find alterations in pubertal development and in the function of the thyroid gland, which could be related to a greater tendency of obesity,†the authors note. A keynote speaker at Beyond Pesticides’ 41st National Forum: Imperatives for a Sustainable Future—Reversing the existential crises of pesticide-induced illness, biodiversity collapse, and the climate emergency, Tracey Woodruff, PhD, MPH, has written in the New England Journal of Medicine, “We need to recognize the very real harm that petrochemicals [including pesticides] are having on people’s health. Many of these fossil-fuel-based chemicals are endocrine disruptors, meaning they interfere with hormonal systems, and they are part of the disturbing rise in disease.â€â€¯Dr. Woodruff’s Forum talk is available here.
To mitigate these health risks, the adoption of organic land management as a holistic solution is necessary. Removing the use of petrochemical pesticides and synthetic fertilizers, especially in agriculture, prevents toxic chemicals from being present in our food and protects the health of all organisms and the environment. Take action to expand the Organic Dairy Product Promotion Program to all-organic lunches, as all kids should have access to safe and healthy food.
Make The Safer Choice to avoid hazardous home, garden, community, and food use pesticides and join the Parks for a Sustainable Future program. You can also become a member of Beyond Pesticides. By doing so, you can add your voice to the urgent movement to eliminate fossil fuel-based pesticide use within the next 10 years and advocate for public health and the environment.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source:
Pérez-Bermejo, M. et al. (2024) Impact of Endocrine Disrupting Pesticide Use on Obesity: A Systematic Review, Biomedicines. Available at: https://www.mdpi.com/2227-9059/12/12/2677.
