Bisphenol S (BPS) could be just as harmful to the reproductive system as Bisphenol A (BPA)—the chemical it replaced—and may damage a woman's eggs at lower doses than does BPA, a study by UCLA researchers suggests.

While looking for replacements to toxic chemicals, manufacturers tend to choose substitute chemicals that, while technically different, often share similar physical properties. Due to increasing consumer pressure, companies have replaced BPA with other related compounds now found in many “BPA-free” products, including BPS.

Patrick Allard, assistant professor of environmental health sciences at the UCLA's Fielding School of Public Health. Image credit: UCLA Fielding School of Public Health.Researchers led by Patrick Allard, assistant professor of environmental health sciences at UCLA's Fielding School of Public Health, exposed a common laboratory model, the roundworm, to several concentrations of BPA and/or BPS to approximate the levels of BPA and/or BPS found in humans. They followed the worms through the duration of their reproductive periods and measured their fertility.

Compared to the control group, worms exposed to either BPA or BPS, or a combination of the two, had decreased fertility. These effects were seen at lower internal doses of BPS than BPA—suggesting that BPS may be more damaging to the reproductive system. This was especially significant when they examined the viability of young embryos.

“This study clearly illustrates the issue with the ‘whack-a-mole’ approach to chemical replacement in consumer products,” Allard says. “There is a great need for the coordinated safety assessment of multiple substitutes and mixtures of chemicals before their use in product replacement."

The researchers say their findings are also a cause for concern in humans, as the same reproductive processes that are disrupted by BPS in roundworms are found in mammals.