Eight scientific societies have voiced their concern over people’s exposure to chemicals, especially ones that mimic hormones, in the environment and their often-untested effects on public health in a letter in Science published today.
There is “growing recognition that currently accepted testing paradigms and government review practices are inadequate for chemicals with hormone-like actions,” states the letter. The scientists urge the U.S. Food and Drug Administration and the U.S. Environmental Protection Agency (EPA) to use a multi-disciplinary panel of researchers from across their boards to develop protocols for testing chemicals for health effects.
Humans are exposed to a number of chemicals through air, water, food, personal cleaning products and other routes. The Centers for Disease Control and Prevention found 212 environmental chemicals in the blood, serum and urine of Americans between 2003 and 2004.
The ability of some of these chemicals to mimic hormones and bind to hormone receptors has caused concern. Recent studies have linked exposures to chemicals at the earliest stages of life, in the womb, to disease in adulthood. Bio-monitoring studies have shown that most Americans have some chemicals in their blood that cause “serious health effects in animal models,” states the letter.
“Direct links to humans remain uncertain, but there is sufficient experimental evidence to raise concern,” states the letter. “Furthermore, there is growing evidence that some chemicals once thought to be safe and allowed into common and, in some cases, abundant commercial use may not be as benign as previously assumed.”
Bisphenol A (BPA), especially, has been controversial, with the European Union and Canada banning the chemical in plastic baby bottles last year. The science behind the controversy was examined by Nature last April – Toxicology: The big test for bisphenol A.
There are other chemicals with properties similar to BPA and new ones are synthesized everyday in chemist’s labs. Approximately 12,000 new substances are added daily to the American Chemical Society’s Chemical Abstracts Service registry, and some of these become used widely in consumer products. Of these, only a fraction will get adequate hazard analysis, states the letter.
The problem is that federal agencies and manufacturers study chemicals using routine toxicology tests and generate dose-response curves that identify a safe limit for using a compound. Unfortunately, such hazard tests appear to be insufficient for hormone-mimics that trigger receptors at lower doses and lose their activity at high doses. This is the inverse of normal dose-response toxicology.
Since any restrictions placed on a chemical need to stand up to legal scrutiny in courts, only routine toxicology tests have so far been used in regulations, according to Greenwire/New York Times. And these tests show that hormone mimics are safe at larger doses, though other biological tests suggest otherwise (see Nature‘s previous coverage). The EPA is already struggling to assess the health impact for a backlog of 478 chemicals using traditional toxicology data, according to the Center for Progressive Reform.
In the letter, the scientific societies say that chemical testing and risk assessment needs to involve toxicologists, and also scientists from a number of scientific disciplines. They offer their services:
“Collectively, our societies represent approximately 40,000 research scientists and clinicians,” states the letter. “The membership of our societies represents leaders in the fields of reproductive biology, endocrinology, reproductive medicine, genetics, and developmental biology. As concerned scientists and clinicians, we are writing to offer the expertise of our collective societies.”
The letter is signed by The American Society of Human Genetics, The American Society for Reproductive Medicine, The Endocrine Society, The Genetics Society of America, The Society for Developmental Biology, The Society for Paediatric Urology, The Society for the Study of Reproduction, and The Society for Gynecologic Investigation.