Doses that produce statistically significant effects in animals are 1–4 magnitudes of order lower than the current lowest observed adverse effect level (LOAEL) of 50 mg/kg/day for laboratory animals set by US National Toxicology Program.
The Vandenberg et al review is an update of the 2007 version to determine the evidence for low dose effects based on the LOAEL or the US EPA reference dose of 50 μg/kg per day.
“The fact that there are any studies showing low dose effects of BPA…indicates that the current safety guidelines for BPA are not protective of human health,” said the researchers.
BPA is an endocrine disruptor that traditional toxicology studies indicate only affects exposed animals in doses as high as 50 mg/kg/day.
Low dose debate
Low dose effects have been demonstrated in cell lines, primary cells and tissues, laboratory animals, and in some human populations, claims the review.
More than 50 epidemiology studies examined health outcomes in relation to BPA exposure since 2007, indicating effects of exposure on endpoints including behaviours, metabolic syndrome, and thyroid hormone signalling.
“Although we did not assess the quality of each of these studies, and some are certainly limited due to their size and/or design, these findings taken together lead to the conclusion that current levels of BPA exposure are related to a number of disease outcomes in humans that are consistent with results from controlled animal studies and mechanistic in vitro studies.”
Several "low dose" studies show effects of BPA at current levels of human exposure.
Referring to a different study, the American Council on Science and Health (ACSH) said that low dose centres on the “claim that small doses of a chemical or drug can have an effect while large doses of the same substance cannot. If this sounds completely crazy, it is.”
In the review which looked at reproducibility, there are examples of specific endpoints shown to be sensitive to low doses of BPA by some scientists but not reproduced by other groups.
“Weight-of-evidence analyses using principles of endocrinology indicate that low dose effects of BPA are highly reproducible and consistent between many different studies,” said the researchers.
The scientists detail the effects of exposure in vitro and in vivo, and how it contributes to health problems in humans, such as polycystic ovarian syndrome, immune response to allergens, behavioral problems and decreased fertility.
“With the knowledge that such tiny amounts of BPA can have such far-reaching implications for humans and wildlife, stricter regulations of this chemical and other endocrine disruptors should be fast on its heels,” said Vandenberg et al.
Turkey: No risk factor
In a separate study, BPA in foods and beverages sold in Turkish markets was carried out using liquid chromatography.
The analysed samples included 36 canned foods, 24 in paper boxes and 18 in glass jars.
They found that the amount of BPA rises with an increase in the amount of glucose, sodium chrolide (NaCl) and expiration date.
Only in bean samples, were BPA concentrations found at levels greater than the European Union migration limit of 0.6 mg of BPA/kg of food.
Sungur et al concluded that BPA is not a risk factor for human health in Turkey at the present time.
Still a place for BPA?
The BPA market is expected to reach $18.8bn by 2019, growing at a CAGR of 5.4% from 2012 to 2018, according to a market analysis from Transparency Market Research.
BPA volume demand in 2012 was around 6.5 million tons and is expected to grow at a CAGR of 4.6% from 2013 to 2019.
Polycarbonates and epoxy resins are important derivatives of BPA. Polycarbonate was the most dominant application segment in terms of production and consumption last year.
Asia Pacific accounted for 53.5% of the market in 2012, followed by North America and Europe.
Industry participants include Bayer Material Science, SABIC Innovative Plastics, Dow Chemicals, Nan Ya plastics Plastics and Mitsui Chemicals.