Endocrine Disruptors and the ‘Cocktail Effect’
For years, I’ve been warning about the dangers of harmful chemicals hiding in plain sight. These toxins are present in a wide array of consumer products, ranging from furniture and bedding, to personal care products, to everyday items such as food can liners and plastic bottles. They’re numerous, and often all but unavoidable. Some, such as bisphenol-A (BPA), are so alarming, manufacturers have begun to respond to market pressures and phase out their use, or they have begun to substitute alternatives. Unfortunately, in the case of BPA, its replacement, BPS, is little better. Both fall under the general category of endocrine disruptors.
These are chemicals that behave like estrogens in the body. Their activity tends to be much weaker than that of natural estrogens. But evidence is mounting that these widespread estrogen mimics are capable of interacting with endocrine receptors on the cells in our bodies, triggering any number of unpredictable—and invariably negative—effects. Among other things, endocrine disruptors are thought to affect sexual health, maturation, and reproduction—and they may be linked to rising rates or type 2 diabetes, obesity, and even cancer.
Experts, policy makers, and industry apologists have reacted to this developing crisis with underwhelming responses that range from indifference, to skepticism, to dismissal, to vague unease. Laws that might be expected to protect the public from harmful chemicals in our products and environment are woefully inadequate and antiquated. The Toxic Substances Control Act has not been updated, for example, since 1976. Although the act regulates some instances of toxins, entire industries are excluded. As it happens, the most relevant ones, such as food, cosmetics, and pesticides, are free of scrutiny under this weak and ineffectual framework.
Scientists have been slow to respond to mounting evidence that endocrine disruptors are harming the public health. Perhaps one reason has to do with the nature of individual chemicals. Because they only weakly bind with estrogen receptors, for instance, there’s an assumption that chemicals such as BPA can’t really do much harm. But new research indicates that assumption is faulty.
The problem, according to scientists at INSERM (a renowned French biomedical research institute), is that single substances that may appear safe on their own often combine with other such chemicals to promote harmful effects in the body. They call this the “cocktail effect”. Researchers have shown, for the first time, that compounds that are weakly estrogenic are capable of binding with estrogen receptors simultaneously to produce a strong effect in a given cell. This synergy among various weak endocrine disruptors may be the smoking gun that explains the harmful effects scientists have been documenting for decades.
Laura N. Vandenberg, Theo Colborn, Tyrone B. Hayes, Jerrold J. Heindel, David R. Jacobs, Jr., Duk-Hee Lee, Toshi Shioda, Ana M. Soto, Frederick S. vom Saal, Wade V. Welshons, R. Thomas Zoeller, and John Peterson Myers. Hormones and Endocrine-Disrupting Chemicals: Low-Dose Effects and Nonmonotonic Dose Responses. Endocrine Reviews, 2012 DOI: 10.1210/er.2011-1050
René Viñas, Cheryl S. Watson. Bisphenol S Disrupts Estradiol-Induced Nongenomic Signaling in a Rat Pituitary Cell Line: Effects on Cell Functions. Environmental Health Perspectives, 2013; DOI: 10.1289/ehp.1205826
Vanessa Delfosse, Béatrice Dendele, Tiphaine Huet, Marina Grimaldi, Abdelhay Boulahtouf, Sabine Gerbal-Chaloin, Bertrand Beucher, Dominique Roecklin, Christina Muller, Roger Rahmani, Vincent Cavaillès, Martine Daujat-Chavanieu, Valérie Vivat, Jean-Marc Pascussi, Patrick Balaguer, William Bourguet. Synergistic activation of human pregnane X receptor by binary cocktails of pharmaceutical and environmental compounds. Nature Communications, 2015; 6: 8089 DOI: 10.1038/ncomms9089