Just like the controversial compound it's designed to replace, a chemical used in cash register receipts and other consumer products messes with hormones, according to research published today.
The study by University of Texas scientists is the first to link low concentrations of bisphenol S (BPS)—a bisphenol A (BPA) alternative—to disruption of estrogen, spurring concern that it might harm human health.
Researchers exposed rat cells to levels of BPS that are within the range people are exposed to. And, just like BPA, the compound interfered with how cells respond to natural estrogen, which is vital for reproduction and other functions.
Previous studies already have shown BPS mimics estrogen, but the new study advances that by showing it can alter the hormone at low doses people are exposed to.
"People automatically think low doses do less than high doses," said Cheryl Watson, a University of Texas biochemistry professor and lead author of the study published in Environmental Health Perspectives. "But both natural hormones and unnatural ones like [BPS] can have effects at surprisingly low doses."
Laura Vandenberg, a postdoctoral fellow at Tufts University who studies BPA, said one limitation of the research was that it used rat cells, but she was quick to point out the method is "extremely informative about predictions for a whole animal."
The study " is a great first research step on BPS and, in my opinion, should be sufficient to say this is an estrogen and we don't want it in our bodies," Vandenberg said.
As its name would suggest, BPS has a similar structure to BPA, which has been used since the 1950s for a variety of purposes, including the manufacture of polycarbonate plastics.
In the past several years, BPS has replaced BPA in the printing of thermal paper used for cash register receipts. Every thermal receipt tested in a study published last year contained BPS.
Bill Van Den Brandt, a manager at Wisconsin-based Appleton Papers, said company representatives couldn't comment on the Watson study because they had not fully reviewed it yet. He added that they "welcome ongoing scientific review of BPS and other potential BPA substitutes."
The largest manufacturer of thermal papers in North America, Appleton switched to BPS after it stopped using BPA in 2006 due to health concerns.
Nearly everyone worldwide is exposed to BPS. Eighty-one percent of urine samples from eight different countries contained traces of it, according to a study published last year. In comparison, about 93 percent of Americans have BPA in their urine.
Watson said she is worried that BPS is becoming more widespread without proper testing for health impacts.
"I think we should all stop and be very cautious about just accepting this as a substitute for BPA," Watson said. "And not just BPS. We should question the whole process about how we introduce chemicals into the marketplace without properly testing them first."
In addition to thermal papers, BPS is used in some hard plastics, Vandenberg said.
"A lot of consumer products say BPA-free, but they don't say BPS, a similar compound, replaced it," she said. She said BPS is less likely to leach into food and beverages because the bonds that hold the compounds in the plastic are stronger than those in BPA products.
A lesser-known use for thermal paper is for ultrasound and other medical machine printouts. According to a 2012 report by the EPA, these BPA-free printouts largely contain BPS.
"I think that might be the most scary use, here you have pregnant women in these ultrasound and imagery rooms handling these printouts with BPS," said John Warner, president of the Warner Babcock Institute for Green Chemistry.
Data are not available on how much BPS is produced annually. Each year about six billion pounds of BPA are produced globally and more than one million pounds are released into the environment, according to the U.S. Environmental Protection Agency.
The American Chemistry Council, which represents chemical manufacturers, did not respond to requests for comment about BPS.
Research investigating possible health impacts from BPS is nascent.
Some studies have proven a link between BPS and estrogen mimicking, but these studies used such high doses it is unlikely people would ever ingest so much, Watson said.
BPS is only a little less potent than BPA in mimicking estrogen, according to a 2005 study in Japan. And a 2012 study in Europe found the two compounds to be equally potent in their estrogen mimicking.
Given the discovery of hormone changes spurred by BPS, some scientists say the chemical could be linked to similar health effects as BPA. Animal studies suggest that BPA exposure causes reproductive problems, obesity and cancers. In human adults, it has been linked to increased risk of diabetes and heart disease.
Researchers haven't focused much on BPS because they're still trying to get policymakers to pay attention to BPA, Vandenberg said.
The EPA and Food and Drug Administration are currently reviewing BPA to determine if regulations are necessary. The EPA also mounted a program in 2010 with manufacturers and green chemists to evaluate BPS and other alternatives used in receipts.