Pesticide-Induced Diseases: Endocrine Disruption
Common household products –detergents, disinfectants, plastics, and pesticides– contain chemical ingredients that enter the body, disrupt hormones and cause adverse developmental, disease, and reproductive problems. Known as endocrine disruptors, these chemicals, which interact with the endocrine system, wreak havoc in humans and wildlife. The endocrine system consists of a set of glands (thyroid, gonads, adrenal and pituitary) and the hormones they produce (thyroxine, estrogen, testosterone and adrenaline), which help guide the development, growth, reproduction, and behavior of animals, including humans. Hormones are signaling molecules, which travel through the bloodstream and elicit responses in other parts of the body.
Download Beyond Pesticides' Endocrine Disruption brochure (bi-fold), or read Beyond Pesticides article, "Pesticides That Disrupt Endocrine System Still Unregulated by EPA."
Endocrine disruptors function by: (i) Mimicking the action of a naturally-produced hormone, such as estrogen or testosterone, thereby setting off similar chemical reactions in the body; (ii) Blocking hormone receptors in cells, thereby preventing the action of normal hormones; or (iii) Affecting the synthesis, transport, metabolism and excretion of hormones, thus altering the concentrations of natural hormones. Endocrine disruptors have been linked to attention deficit hyperactivity disorder (ADHD), Parkinson’s and Alzheimer’s diseases, diabetes, cardiovascular disease, obesity, early puberty, infertility and other reproductive disorders, and childhood and adult cancers.
More than 50 pesticide active ingredients have been identified as endocrine disruptors by the European Union and endocrine disruptor expert Theo Colborn, PhD. Endocrine disruption is the mechanism for several health effect endpoints. See the related sections (Cancer, Developmental and Learning Disorders, Parkinson’s disease, Reproductive Health) for more information.
- Human exposure to endocrine disrupting compounds: Their role in reproductive systems, metabolic syndrome and breast cancer. A review
Endocrine disrupting chemicals (EDCs) are released into the environment from different sources. They are mainly used in packaging industries, pesticides and food constituents. Clinical evidence, experimental models, and epidemiological studies suggest that EDCs have major risks for humans by targeting different organs and systems in the body (e.g. reproductive system, breast tissue, adipose tissue, pancreas, etc.). Due to the ubiquity of human exposure to these compounds the aim of this review is to describe the most recent data on the effects induced by phthalates, bisphenol A and parabens in a critical window of exposure: in utero, during pregnancy, infants, and children. The interactions and mechanisms of toxicity of EDCs in relation to human general health problems, especially those broadening the term of endocrine disruption to 'metabolic disruption', should be deeply investigated. These include endocrine disturbances, with particular reference to reproductive problems and breast, testicular and ovarian cancers, and metabolic diseases such as obesity or diabetes.
[Giulivo M, Lopez de Alda M, Capri E, Barceló D. 2016. Environ Res. 151:251-264.]
- Individual and combined effect of chlorpyrifos and cypermethrin on reproductive system of adult male albino rats.
Commercial mixtures of chlorpyrifos and cypermethrin pesticides are widely used to enhance the toxic effects of cypermethrin on target insects. So, the purpose of the current study was to evaluate the individual and combined toxic effects of chlorpyrifos (CPF) and cypermethrin (CYP) on reproductive system of adult male albino rats. Forty adult male albino rats were randomized into main four groups. All treatments were given by oral gavage for 12 weeks. Single CPF and CYP exposures significantly have adverse effects on reproductive function of adult male albino rats manifested by reduced testicular weight, decreased sperm count, motility and viability, significantly increased percent of morphologically abnormal spermatozoa, and significant increments in sperm DNA fragmentation index (DFI) with respect to control group. Furthermore, serum follicle stimulating hormone, luteinizing hormone, and testosterone levels were decreased significantly compared to control group. This was accompanied with histopathological changes in the testis of rats such as necrosis, degeneration, decreasing number of spermatogenic cells in some seminiferous tubules, edema, congested blood vessels, and exudate in interstitial tissue of the testis. Notably, all these changes were exaggerated in rats treated concomitantly with chlorpyrifos and cypermethrin rendering the mixture more toxic than the additive effects of each compound and causing greater damage on the reproductive system of male albino rats than the individual pesticides.
[Alaa-Eldin EA, El-Shafei DA, Abouhashem NS. 2016. Environ Sci Pollut Res. doi:10.1007/s11356-016-7912-6]
- The Increasing Prevalence in Intersex Variation from Toxicological Dysregulation in Fetal Reproductive Tissue Differentiation and Development by Endocrine-Disrupting Chemicals
An increasing number of children are born with intersex variation (IV; ambiguous genitalia/hermaphrodite, pseudohermaphroditism, etc.). Evidence shows that endocrine-disrupting chemicals (EDCs) in the environment can cause reproductive variation through dysregulation of normal reproductive tissue differentiation, growth, and maturation if the fetus is exposed to EDCs during critical developmental times in utero. Animal studies support fish and reptile embryos exhibited IV and sex reversal when exposed to EDCs. Occupational studies verified higher prevalence of offspring with IV in chemically exposed workers (male and female). Chemicals associated with endocrine-disrupting ability in humans include organochlorine pesticides, poly-chlorinated biphenyls, bisphenol A, phthalates, dioxins, and furans. Intersex individuals may have concurrent physical disorders requiring lifelong medical intervention and experience gender dysphoria. An urgent need exists to determine which chemicals possess the greatest risk for IV and the mechanisms by which these chemicals are capable of interfering with normal physiological development in children.
[Rich AL, Phipps LM, Tiwari S, et al. 2016. Environ Health Insights. 10:163-71. ]
- Hormones and endocrine-disrupting chemicals: low-dose effects and nonmonotonic dose responses
Here, a team of researchers review two major concepts in EDC studies: low dose and nonmonotonicity. Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies. They review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, they explore nonmonotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined. Authors illustrate that nonmonotonic responses and low-dose effects are remarkably common in studies of natural hormones and EDCs. Whether low doses of EDCs influence certain human disorders is no longer conjecture, because epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities. Authors conclude that when nonmonotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses. Thus, fundamental changes in chemical testing and safety determination are needed to protect human health.
[Vandenberg LN, Colborn T, Hayes TB, Heindel JJ, Jacobs DR Jr, et al. 2012. Endocr Rev.33(3):378-455.]