BPA-free? Replacement plastics are just as bad for you, study suggests

Next time you're at the supermarket, note how many of the plastic containers on sale promote the fact they're BPA-free.

Then consider this - the chemicals some manufacturers now use instead of BPA might be just as bad.

New research has found a link between BPS and BPF and obesity, just like BPA.

"This research is significant because exposure to these chemicals is very common," study author Melanie Jacobson of the NYU school of medicine said in a statement.

"BPS and BPF use is growing because manufacturers are replacing BPA with these chemicals, so that is contributing to the frequency of exposure."

BPA - Bisphenol A - is commonly found in plastic bottles and containers, and is used to line thermal paper and cans. It can be hazardous at high levels because it mimics the hormone oestrogen, according to Ministry for Primary Industries' (MPI) food safety division.

Consumers have tried to avoid it in recent years, after studies linked it to a range of problems, including weight gain, infertility, increased cancer risk, imparied thyroid and liver function, heart disease and diabetes. 

Manufacturers responded by replacing it with similar chemicals - BPS and BPF - and advertising their products as 'BPA-free'.

Last year the same researchers who first exposed BPA found similar shortcomings in BPS - it caused "remarkably similar chromosomal abnormalities" in mice when they were exposed. 

"Just because a plastic is 'BPA-free', it does not necessarily mean the replacement used is less toxic," University of Auckland chemistry professor James Wright said at the time.

"Most likely the toxicity of the replacement has not been intensely studied."

Dr Jacobson's team at NYU looked at links between BPS and BPF exposure in children - not mice - and found those with higher concentrations in their urine were more likely to be obese, just like with BPA.

The researchers said there was a chance obese kids are just exposed to more BPF because they eat more overall, but the link remained even after the effects of calorie intake were removed.

"Replacing BPA with similar chemicals does nothing to mitigate the harms chemical exposure has on our health."

MPI estimates Kiwis' BPA intake is well below the maximum safe level set by the European Commission. It makes no mention of BPF or BPS on its website, nor does Food Standards Australia New Zealand.