Story highlights BPA-free alternatives may be no safer than BPA, say researchers

Most common alternative, BPS, linked in study to disruptions of estrogen and thyroid hormones

(CNN) Your "BPA-free" plastic product may be no safer than the product it replaced, says a new UCLA study that analyzed the impact of a common BPA alternative on zebra fish embryos. The study joins a small but growing group of similar research sounding the alarm about so called "BPA-free" alternatives.

"Our findings are frightening and important," said senior author and reproductive endocrinologist Nancy Wayne. "Consider it the aquatic version of the canary in the coal mine."

After decades of animal research linked BPA (Bisphenol A), a known endocrine disruptor, to problems with brain and reproductive development, early puberty and a rise in breast and prostate cancer, many manufacturers stopped using the chemical to harden plastics, replacing it with "BPA-free" alternatives. The most common replacement is BPS (Bisphenol S), said Wayne.

Wayne and her colleagues exposed zebrafish to low levels of both BPA and BPS, and looked at the impact of the chemicals on genes and brain cells that control reproduction. Zebrafish have often been used to study the impact of plastic additives because their transparent embryos allow scientists to see and monitor cell growth.

"Our research showed that low levels of BPS had a similar impact on the embryo as BPA," Wayne told CNN. "In the presence of either BPA or BPS, embryonic development was accelerated. Additionally, BPA caused premature birth."