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.”
Because many EDCs are lipophilic, our bodies often store them in our fat cells, often for years at a time.
While bisphenol A tends to exit the body quickly, we are commonly exposed to it on a daily basis, usually through a compound that leaches into our food, allowing the chemical an opportunity to exert an effect, even if the results of this effect aren’t immediately apparent. “If it’s a pregnant woman or someone planning a family, that exposure can change something,” Dr. Gore warned.
Although earlier studies had linked EDC exposure to a variety of reproductive health concerns, Dr. Gore said that since the Society’s last statement, there is much more corroborating evidence. In particular, polycystic ovarian syndrome in humans has been associated with higher body burdens of BPA and other chemicals, as have endometriosis, fibroids, and some adverse birth outcomes. Still, much of the data come from animal studies, and studies of specific links between EDCs and reproductive outcomes and cancers are inconsistent.
According to Dr. Renee Howard , a pediatric dermatologist with Sutter Health in San Francisco, who regularly gives presentations on the effects of EDCs in cosmetics and other skin care products, although much of the current research shows a link between EDCs and chronic illness, so far a causal relationship has not been established. Still, she said she routinely tells other physicians to keep an “open mind” when discussing EDCs with patients.
“We can acknowledge there is uncertainty, and we can tell patients that these chemicals are actively being studied, but that the studies are, as of now, inconclusive, and that there are still no documented adverse health effects associated with skin care products,” Dr. Howard said. Nevertheless, she said common sense dictates her to counsel patients to avoid products containing the EDC triclosan such as antimicrobials and scented products. She also advises them to eat organic produce in order to avoid pesticides.
Dr. Gore and her coauthors hope the statement will help bump EDC oversight higher up the policy chain globally.
“Exposure to endocrine disrupting chemicals during early development can have long-lasting, even permanent consequences,” Endocrine Society member Dr. Jean-Pierre Bourguignon , a professor of pediatric endocrinology at the University of Liège in Belgium, said in a statement. “The science is clear, and it’s time for policy makers to take this wealth of evidence into account as they develop legislation.”
To that end, earlier this year, twin bills are now before the House and Senate, which – if passed – will take effect in 2018, banning the sale of any personal care products containing microbeads, BPA-rich, microscopic plastic particles that have entered much of the natural water supply, threatening marine life which often mistake the tiny bits as food. Meanwhile, Minnesota has banned the use of triclosan statewide as of 2017.
Dr. Gore also said in addition to funding for this research being made a priority, it’s time to rethink who gets to be in on the science. Rather than just industrial chemists, she believes the teams should include so-called “green chemists,” basic, translational, and clinical scientists; epidemiologists, as well as public health professionals. Health care providers should be familiar with endocrine science and the latest developments in EDC research, accordingly, because, said Dr. Gore, “The [health] costs of EDCs have been estimated in the hundreds of millions of dollars. Prevention might seem expensive, but it’s far-less-expensive than all the ensuing diseases.”
Most of all, Dr. Gore and her colleagues emphasize that there will never be “absolute proof” of anything, but that taking action to stem exposure is essential.
The analysis was sponsored by the Endocrine Society. Dr. Gore is editor in chief of Endocrinology. Dr. Howard disclosed no relevant financial relationships.
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