BPA-free plastic might not be any better than what we were using before, new research has found.
The additive, also known as bisphenol A, helps make plastic durable and tough - but in the late 1990s, researchers at Washington State University found exposure to BPA caused chromosomal abnormalities in mice eggs.
That discovery was accidental - BPA leeched out of plastic cages used to hold the mice after they were washed with a strong detergent.
"In the intervening 20 years, our studies and those of colleagues have described the effects of BPA exposure on the developing brain, heart, lung, prostate, mammary gland and other tissues, and our studies have described serious effects on the production of both eggs and sperm," researcher Patricia Hunt wrote in an article for The Conversation.
"Together these findings inflamed debate about the safety of BPA and resulted in the rapid appearance of 'BPA-free' products."
The same lab has now uncovered similar adverse health effects from BPA-free plastic.
"The major culprit this time was not BPA but the replacement bisphenol, BPS, leaching from damaged polysulfone caging."
Prof Hunt called it a "strange déjà vu" - the replacement bisphenols were causing "remarkably similar chromosomal abnormalities to those seen so many years earlier in studies of BPA".
It's not clear yet if some of the replacement substances are better for health than others, Dr Hunt saying more research is needed.
But whether or not a plastic container or bottle is BPA-free, she said "plastic products that show physical signs of damage or aging cannot be considered safe".
BPA is used in a range of products, including CDs, food storage containers, cellphone casing, bumpers, lenses and visors, receipts, can liners, helmets and consoles.
"The ability of manufacturers to rapidly modify chemicals to produce structurally similar replacements undermines the ability of consumers to protect themselves from hazardous chemicals and federal efforts to regulate them," Prof Hunt wrote.
University of Auckland's Professor James Wright agreed.
"Just because a plastic is 'BPA-free', it does not necessarily mean the replacement used is less toxic. Most likely the toxicity of the replacement has not been intensely studied."
University of Canterbury Associate Professor Sally Gaw told TVNZ other bisphenols are chemically very similar to BPA, so it's not surprising they'd act in a similar way.
"I think we do need to consider all of our uses around plastic and the kind of exposures that we have."
The latest research was published in journal Current Biology.