Environmental poisons aren't at all like they used to be. Sure, tobacco smoke and asbestos still kill. But a more insidious — and more pervasive — class of chemicals is increasingly getting scientists' attention.
Endocrine-disrupting chemicals (EDCs) are substances that imitate natural hormones in the body. We absorb them constantly, mostly through plastics and personal-care products. And a growing stack of studies links these synthetic chemicals to everything from asthma to low IQ, cancer and altered reproductive development.
One widely publicized EDC was bisphenol-A, found in places like the linings of food cans. Possibly even more prevalent are a group of EDCs called phthalates. Though mostly used as binding agents and softeners in plastics, phthalates ("thale-ates") are found in hundreds of products, from vinyl flooring and raincoats to cosmetics, personal-care items and food.
In 2012, responding to research about risks to infants, Congress banned some phthalates in children's toys and some child-care products. A 2014 Columbia University study tied prenatal phthalate exposure to a more than six-point decrease in IQ. Now, research from the University of Pittsburgh Graduate School of Public Health suggests further risks to pregnant women and their babies.
The study explores how phthalates affect hCG, a pregnancy hormone produced by the placenta that affects fetal sex development. Data collected from more than 350 women (in states including California) found that among women with high phthalate exposure, there was lower hCG in those carrying male babies and higher hCG in those carrying female babies. Higher hCG, in turn, correlates with a shorter anogenital distance — the distance from anus to scrotum — in male babies. And shorter anogenital distance is strongly associated with low sperm count.
The findings were presented at the Endocrine Society's annual meeting, March 5 in San Diego, by Pitt epidemiologist Jennifer Adibi. "Our study is the first to look at hCG as a target of phthalate exposure in pregnancy," Abidi said. Because a mother's blood does not reach the fetus directly, the study suggests how maternal exposure to EDCs might influence fetal development.
Though worrisome in itself, the Pitt study is only the tip of the EDC iceberg. Besides phthalates, other EDCs include pesticides and flame retardants. In another study presented at the Endocrine Society meeting, Canadian researchers examined exposures by rats to both phthalates and the flame retardants on foam furniture cushions. (Flame retardants are also found in mattresses, children's pajamas, electronics and car seats.) Researchers found that rat pups whose mothers received low doses of these compounds exhibited increased behaviors like those seen in humans with autism-spectrum disorders: less social interaction, for instance, and more hyperactivity.
Study of EDCs — a field that barely existed 20 years ago — produced about 750 research papers last year, according to pioneering, New York-based researcher Shanna S. Swan, on whose work the recent Pitt study expanded.
Some effects of EDCs might seem small: In the Pitt study, for instance, the average decline in anogenital distance was 5 percent. But these changes add up. As Adibi says, "We're talking about something like lead and IQ," where tiny toxic exposures, at levels once thought safe, proved disastrous in large populations over time.
Prenatal EDC exposure has also been linked to problems like obesity, diabetes and attention-deficit disorder. A recent paper in the The Journal of Clinical Endocrinology & Metabolism estimated that EDC exposure costs the European Union 157 billion euros (about $209 billion) a year in medical expenses and lost earning potential. (Most of that is from pesticides, and most impacts are neurological, researchers said.) But that estimate accounts for only a fraction of the 1,000 or so likely EDCs. Most of those substances are neither regulated nor rigorously tested for health effects (let alone for interactions with other chemicals, including pharmaceuticals, in human bodies).
Many will ask how individuals can protect themselves. And indeed, scientists say checking product labels and not microwaving plastic food containers are smart strategies for avoiding EDCs.
But Adibi says we have to address EDC exposures on a bigger scale — with consumer advocacy, education of health-care providers and, yes, regulation: "The research is raising the red flag that the only way to tackle these exposures is to address them as a society."