Cash register receipts, tin can linings, and a range of cosmetics and other common household products increasingly are implicated in the most intractable of society’s diseases such as obesity and diabetes.
So-called endocrine-disrupting chemicals have become so common, according to the Washington-based Endocrine Society, that nearly every human alive has been exposed to at least one such chemical, probably more than once, and just as likely, over an extended period of time.
The World Health Organization reports that there are more than 800 known endocrine disrupting chemicals (EDCs) used in products globally, but only a fraction of them have been tested in humans. What effects, if any, this exposure is having on individuals is still unknown, but data linking the ability of EDCs – either singularly or in combination – to mimic, block, or otherwise interfere with the body’s natural hormone signaling has some experts sounding the alarm.
“The evidence is more definitive than ever before – EDCs disrupt hormones in a manner that harms human health,” Andrea C. Gore, Ph.D., a pharmacology professor at the University of Texas at Austin, said in a press conference. Dr. Gore chairs the Endocrine Society task force that recently released an executive summary of its second scientific statement on EDCs. The Society presented the statement, an update of one released in 2009, at this year’s International Conference on Chemicals Management annual meeting in Geneva.
Because the endocrine system’s role is to interact with the environment, it is predisposed to react to triggers increasingly found in everything from pesticides to shower curtains, which have now made their way into waterways and the food chain primarily without any studies on their impact. “Both natural hormones and EDCs have unique dose-response properties [and can] act at very-low doses,” Dr. Gore told reporters. “We’re exposed throughout our lives.”
The use of EDCs largely began post-WWII with pesticides such as DDT (dichlorodiphenyltrichloroethane), but over time came to include use as thickeners, plastic softeners, and scent in many common household items. Dr. Gore told a reporter that even though these chemicals were not intended to enter the environment at large, decades of use has made their entry into the food chain inevitable. The population health effects of this are only now becoming evident as data accumulate linking EDCs to a constellation of ill health effects.
“In humans, there are strong epidemiological associations between EDCs and chronic diseases.” Dr. Gore said.
She specifically cited obesity, diabetes, and a range of reproductive disorders, including infertility and certain hormone-related cancers. Research also shows a link between prenatal EDC exposure in animals to obesity, insulin resistance, and overabundant insulin later in life.
The Society’s meta-analysis of more than 1,300 studies published in the last 5 years also implicated EDCs in disorders of the prostate gland, the thyroid, and the neuroendocrine systems, the latter two being particularly vulnerable because of their role in hormone regulation at all stages of development.
“We’re particularly concerned about fetuses and how exposure can set the stage for later development of diseases,” Dr. Gore said, noting that human studies have shown a link between higher EDC exposures over time and cognitive deficits and other adverse neurocognitive outcomes.
Because the effect of EDC exposure differs according to the dose, length, and timing of exposure, designing studies to measure any harm has been difficult, said Dr. Gore, although in the past 5 years, there has been increased insight into the molecular mechanisms underlying EDCs.
Among the most common EDCs are bisphenol A (BPA) and phthalates, synthetic chemicals that bind to hormone receptors and depending upon the dose, either potentiate, inhibit – or both – the hormone’s effect on receptors. These EDCs frequently occur in toys, bottle nipples, rain coats, shower curtains, and in medical supplies such as blood bags, IV tubing, and catheters.
Initially registered as a pesticide, the EDC triclosan’s antimicrobial power has meant it is now used in deodorants and even in toothpaste. Triclosan has been shown to disrupt the thyroid, and to have antiestrogenic, and antiandrogenic properties. It also has been linked to asthma.
Plastic water bottles and disposable, plastic-based food packaging commonly found in microwaveable products often are high in BPAs, according to Dr. Gore, who urged all primary care physicians to counsel patients on the importance of avoiding products that contain them whenever possible, particularly in cases of pediatric obesity or diabetes, and for patients who are pregnant or in the family-planning stages. “You might not see an adverse outcome until years or decades later.”