There’s no shortage of evidence suggesting that BPA is bad for our health. The compound has profound effects on the hormone system, and appears to affect fertility in both men and women, the risk for obesity and certain developmental problems in girls.

A new study suggests that there’s even more to the story. BPA can become chlorinated from the tap water with which it comes into contact, and the BPA-chlorine combo may pose an additional, and perhaps more serious, set of health risks.

Even when BPA is removed from products, something else typically replaces it. And, given the spotty nature of product safety regulation, there’s no telling whether the replacement chemical is any better than the one it is replacing.

The researchers who devised the study wondered about what BPA might trigger when it picks up chlorine molecules from tap water, which is chlorinated to kill pathogens. BPA in our water can come from trace amounts of plastic in the water supply or from PVC pipes through which it flows.

Their results showed that chlorinated BPA can significantly interfere with cell signaling. This seems to work through estrogen receptors on the cell membrane.

“We found that when you modify the BPA it works just as dramatically but in different ways on the same systems,” study author Cheryl Watson said in a statement.

The different types of chlorinated BPA all affect JNK and ERK kinases, enzymes which play important roles in how cells communicate. “These kinases are major control centers, gathering all the cell signals, making decisions and then expediting them,” Watson said. “If you change the dynamic by inactivating kinases, you can mess up cell signaling.”

So it appears that chlorinated BPA can affect cell machinery just as regular BPA can – whether the effects are worse or just different remains to be seen.

Given the huge number of chemicals out there that still need to be tested, the team used a robot to do the work. This raises the important point that even when BPA is removed from products, something else typically replaces it. And, given the spotty nature of product safety regulation, there’s no telling whether the replacement chemical is any better than the one it’s replacing.

In general, experts recommend reducing your exposure to products containing BPA, and being especially careful of what your kids come into contact with. Even though it’s been banned from baby bottles and sippy cups, BPA is still present in a number of other products, from plastic dinnerware to soup cans to plastic water bottles to dental fillings to store receipts.

According to the authors, over 92% of people over the age of six have some level of BPA in their urine. It may not be possible to avoid BPA completely, but reducing exposure is a good idea.

The study was carried out by a team at the University of Texas Medical Branch at Galveston and published in the journal Endocrine Disruptors.