Concern over potentially harmful health effects from exposure to the estrogen-mimicking compound bisphenol A (BPA) initially leveled a spotlight on baby bottles, food cans and packaging. But that focus has left several other potentially important sources of estrogen mimics out of the spotlight including alternative replacements for BPA which could be just as deadly.
In fact, sources of these so-called endocrine disrupters go well beyond bottles and cans. Key among them are credit card and cash register receipts that use BPA in the printing process, natural estrogenic compounds found in foods, and estrogenic compounds that leach from a wide range of plastics, not just those that contain BPA.
“When it comes to BPA in the environment, the biggest exposure, in my opinion, is from cash register receipts,” says John C. Warner of the Warner Babcock Institute for Green Chemistry (WBI), in Wilmington, Mass. “Once on the fingers, BPA can be transferred to the mouth, onto food, and likely absorbed through the skin.”
Daniel Zalko of the French National Institute for Agricultural Research, in Paris, led a team that measured significant diffusion of C-labeled BPA through samples of pig and human skin. Separately, Harvard University's Joseph M. Braun and coworkers monitored the diets and analyzed BPA in urine samples of nearly 400 pregnant women, finding that cashiers had the highest BPA levels and that teachers and industrial workers had significantly lower levels.
Other plastics--even BPA-free ones--may also be a source of endocrine disrupters. A recent analysis of more than 450 everyday plastic products, from plastic bags to water bottles, found that about 95% of the items tested leached chemicals that triggered a bioassay for estrogenic activity, including most of the products labeled as BPA-free (C&EN, March 14, page 48).
The plastics analysis didn't attempt to identify the individual estrogenic compounds responsible in each case. Instead it focused on quantifying estrogenic activity, irrespective of the chemical causes, explains neurobiologist George D. Bittner of the University of Texas, Austin, who led the study. “Although BPA is the most notorious chemical with estrogenic activity used in plastics, it is not the only one, nor does it have the highest biological effect,” Bittner says.
Not all chemicals that show estrogen-like activity are necessarily toxic, he adds. But Bittner is concerned that ingesting these chemicals from plastics contributes to people's daily load of estrogenic compounds, and he suggests that it makes sense to seek out estrogenic-activity-free plastics, especially when the additional production cost “can often be as little as a fraction of a cent per pound.”
For now, manufacturers that have gone BPA-free have switched from polycarbonate to different base polymer systems, notably Eastman Chemical's Tritan copolyester, glycol-modified polyethylene terephthalate (also a copolyester), and clarified polypropylene, Bittner notes. “But as our data show, the switch to some new materials has not ameliorated the estrogenic activity: BPA-free does not mean estrogenic-activity-free,” he says.
The new Nalgene water bottles which are BPA-free are made of the "copolyester" plastic manufactured by Eastman Chemical. So are new bottles by Kor and Camelbak. All trumpet the fact that their bottles are BPA-free, with the implication that BPA-free is the equivalent of safe. But we have no way of knowing because the ingredients that make up Tritan have been kept secret. They could include another dangerous chemical...or not. Since the ingredients have not been identified, no one can say. All currently available information about this product's chemistry comes from its manufacturer.
The Eastman Chemical website offers Material Safety Data Sheets (MSDS) for 23 different compounds sold under the Tritan copolyester name (each intended for different product applications). The MSDS sheets list no toxicity data and note that the compounds' environmental effects have not been tested.
Eastman Chemical states that the product is not carcinogenic. Toxicological studies conducted by the company confirm that the monomers used in Tritan do not demonstrate an affinity to bind to hormone receptors, nor a potential to induce endocrine disruptive effects. However, this is contrary to the Bittner's findings which do not show estrogenic-activity-free.
The same could be said of any number of new materials used in hundreds of consumer products. Under the Toxic Substances Control Act (TSCA), the U.S. law that regulates chemicals in commerce, it's entirely permissible to launch a new material into high-volume production without disclosing its precise chemical identity or any information about its toxicity. This makes it impossible for the public to assess product safety independently of manufacturer claims. And currently, despite EPA and FDA policies that support "safe" alternatives to a chemical of concern like BPA, neither federal agency conducts safety testing of new materials destined for consumer products before they come on the market.
“Before we jump to the conclusion that all plastics are bad, some important details need to be filled in,” observes Daniel F. Schmidt, a polymeric materials chemist at the University of Massachusetts, Lowell, who reviewed the Bittner study.
Schmidt argues that rapid progress is needed on the question of human exposure to endocrine disrupters, and that better screening of plastics under actual-use conditions will be an important part of any answer. For additional context, the significance of other sources of possible estrogenic phenolic compounds, such as paper products and phytoestrogens, should also be studied, Schmidt says, “to give ourselves a reality check and make sure we're not missing the forest for the trees.”
What all this means is that while U.S. federal policy supports alternatives to BPA--and we're using products containing these new materials at increasing volume--we actually know very little about them and lack a system that would provide independent assessment of new materials before they're in our homes. With demand growing for safe plastics, it's clear that we need a better and more proactive way of ensuring their safety--and ours.