Cancer results from the complex interplay of an individual’s genetic predisposition, lifestyle, and environmental exposure. In fact, two thirds of all cancers are environmentally linked in some way. Certain jobs are associated with an elevated risk of cancers, especially jobs with a high burden of chemical exposure such as painting, firefighting, working in the coal, steel, or rubber industries, textile and paper manufacturing, and mining.
Importantly, many of the chemicals listed by the US National Institutes of Health as cancer-causing substances are also considered endocrine disrupting chemicals (EDCs).
The connections between chemical exposures and cancer have long been established in metals and dyes, solvents and silica, and pharmaceuticals such as synthetic estrogens. According to studies using cellular and animal models and newer human-based studies, many carcinogens may also be EDCs, and could influence the development and progression of cancer by acting like hormones. EDCs can also influence cancer development across generations, including children and grandchildren.
Diethylstilbestrol (DES) is one well-studied example. From 1938-1971, DES was widely used under the mistaken belief that the drug prevented miscarriage and ensured a healthy baby. Extensive research has shown that women who took this medicine during pregnancy had daughters with higher risks of rare vaginal and cervical cancers. Up to 10 million US women took the drug before the Food and Drug Administration acted to stop its use.
Why wasn't it stopped sooner? In part because EDC research in humans is challenging due to the wide range in time, duration, and extent that exposures may have occurred. Exposures that took place years or decades earlier may impact a individual’s present health. Several studies have demonstrated that early life exposure to EDCs can increase cancer risk much later in life. For example, exposure to DDT (a formerly widespread pesticide) by females early in life is associated with increased risk of breast cancer. Despite the evidence and fact that DDT is banned in the United States and many other countries, it is still available and used in countries.
In women, EDC exposure is linked to uterine and ovarian cancer. BPA, which is found in food and beverage containers, cosmetics and household materials, can act directly on the mammary gland at low doses to significantly increase ductal growth and risk of breast cancer (the leading type of cancer in US women). Exposure can even happen before a child is born. Studies have found that BPA can be transmitted from mothers to children in the womb and even through breastfeeding.
In men, even low levels of BPA exposure may increase risk of prostate cancer (the leading type of cancer in US men). Some EDCs are associated with aberrant prostate growth and others are associated with testicular cancer. In addition, EDCs may reprogram stem and progenitor cells, potentially transmitting a lifelong predisposition to a disease like prostate cancer.
Many cancers outside of the reproductive system also have a hormone connection. Bone cancer, for example, is associated with growth hormone. Thyroid-stimulating hormones, as well as the T3 and T4 hormones that affect nearly every function of the body, are associated with thyroid cancer. Scientists are studying which EDCs may affect these cancers.
Knowing the effects of EDCs is an important first step. Here are a few resources to learn more:
