‘Very small’ risk from bisphenol A

01 Sep 2011

The risk to human health posed by bisphenol A (BPA) is “very small”, according to the latest update by a Japanese research institute as part of a six-year monitoring project on the chemical.

The Research Institute of Science for Safety and Sustainability (RISS), part of the country’s National Institute of Advanced Industrial Science and Technology, said it had reached its conclusions after examining a range of concerns relating to the substance – including next generation toxicity, carcinogenicity via oral exposure and neurotoxicity.

BPA is a monomer used in the production of polycarbonate baby bottles and the epoxy linings of food and beverage cans. A large number of scientific studies have raised concerns of potential human hazards posed by the use of the chemical in food packaging. However, while its use has been banned in polycarbonate baby bottles in the European Union, all major global food safety authorities, including the European Food Safety Authority (EFSA), have declared current exposure through food contact materials poses no risk to humans.

No concerns but no neurotoxicity evaluation

RISS has been investigating BPA since 2005 as part of a rolling programme. It latest evaluation involved a two generation reproductive study using mice under OECD GLP as “reproductive toxicity in the next generation was one of concerns with regard to the human health hazard induced by BPA”, it said.

It concluded that, in general, there was “no toxic effects on the reproductive potential" of offspring and a ”no observed-adverse-effect level (NOAEL) of 50 mg/kg bw “ was noted.

Its report, published this month, said that carcinogenicity of BPA by oral administration had “already been determined to be negative from bioassays”.

There is almost no need for concern regarding skin irritation, skin sensitization, skin photo-irritability, and photosensitization due to BPA, because these were found to be negative in animal testings at a practical dose level, it added.

The study did not evaluate developmental neurotoxicity of BPA because “the validity of the testing protocol on chemical compounds with estrogenic activities has not yet been proven”, said RISS.

Experiments in animals that had measured this were deemed “all too uncertain to conclude as being adverse to humans”.

The NOAEL for the hazard assessment of BPA was determined to be 3 mg/kg bw/day, with the uncertainty factor of 25 (= species difference: 2.5 x individual difference: 10. The body said its previous work concluded NOAEL and uncertainty factor were 5 mg/kg bw/day and 100, respectively,

In the present assessment, the uncertainty factor related to species difference with regard to the extrapolation of animal data to human was determined to be 2.5 because BPA has been shown to be detoxified mainly by glucuronide-conjugation in the liver, but it is rapidly metabolized and excreted in humans in comparison to rodents, explained RISS.

After examining exposure rates and amounts of BPA believed to be excreted in urine – both for adults and children aged 1 to 6 years - the body said the Margin of Exposure “became 730 to 770 in 1 to 6 year-olds, and 40,000 to 81,000 in adults”.

“These values were much larger than the MOE (25) estimated to cause health hazards in humans mentioned above or the conventional and conservative MOE (100), and thus the risk of BPA with regard to human health was believed to be very small,” said the RISS research.

Source: Research Institute of Science for Safety and Sustainability