An examination of more than 80 published human biomonitoring studies has concluded that the general population is exposed to bisphenol A and is at risk from internal exposure to unconjugated, or biologically active, BPA.
The biomonitoring data indicate that human exposures are higher than have been suggested from the toxicokinetic studies, said the report, released online March 24.
Toxicokinetic studies look at the change in concentration, over time, of a chemical or metabolite in blood/plasma or tissue.
These [biomonitoring] studies overwhelmingly detect BPA in individuals including adults, adolescents and children. The health of the public is at stake, said the report from a team of global researchers led by Laura Vandenberg of Tufts University. Because of the significant data showing human exposures to unconjugated BPA and animal data indicating increased susceptibility to disease at levels found in humans, we recommend that the precautionary principle be followed until further data on exposure of fetuses and children to BPA become available.
It is likely that fetuses and children are particularly vulnerable to BPA exposures and, at the same time, are exposed to higher levels of unconjugated BPA, said the report, which was published in Environmental Health Perspectives, a monthly journal of peer-reviewed research and news.
However, Steve Hentges, executive director of the polycarbonate/BPA global group of the American Chemistry Council in Arling- ton, Va., disputes the conclusions.
The opinions of the authors are quite inconsistent with the views of expert scientific and government bodies that have also reviewed these biomonitoring studies, Hentges said. Eleven safety agencies around the world, including the European Food Safety Agency, have said BPA is OK for use in food-contact applications.
Hentges said the authors' conclusions do not appear to be based on analysis that is contained in the studies, but rather opinion. There was some deception in what they described and they were selective in what they reported, Hentges claimed.
The researchers examined biomonitoring studies that involved thousands of people in the U.S., Japan, China, Korea, and the European Union, with an emphasis on urine, blood and fluids associated with pregnancy and lactation.
Biomonitoring studies allow for the determination of internal circulating levels and excreted concentrations of a chemical, accounting for exposure from all possible sources, rather than suspected exposures from specific sources.
Although some in the risk-assessment community have questioned the reliability of those biomonitoring studies, the report said the consistency of available data across investigative groups on internal exposure to BPA is more than convincing.
The report said that the only two toxicokinetic studies that have been done so far and that suggest that human exposure is negligible have significant flaws and are not reliable for risk assessment purposes.
The reliance of regulatory agencies on the two studies that predict no human exposure in contrast to the 80-plus studies that measure actual internal exposures is contrary to scientific principles, said the report.
Hentges disagreed. The authors didn't identify any real flaws in those two toxicokinetic studies, he said.
BPA is used to make PC products including baby bottles, sports bottles, reusable food and drink containers, bicycle helmets, CDs and DVDs. It is also an ingredient in the epoxy resins used to line metal cans.
Washington, Wisconsin, Connecticut, Minnesota, the city of Chicago and Suffolk County in New York have enacted bans on BPA in bottles and food and beverage containers for children 3 years old and younger. The six major makers of baby bottles agreed in 2009 to stop selling PC bottles in the U.S. Epoxy resins, however, are still used in the lining of most canned foods and beverages, including infant formula.
In mid-January, the Food and Drug Administration reversed its long-held stance that BPA is safe for food-contact applications. Regulators said they were particularly concerned about BPA's effect on the development of fetuses, infants and young children. But FDA did not ban BPA or require manufacturers to label products that contain BPA, saying there is not enough information to take such action.
The report, funded by the National Institutes of Health in the U.S. and the National Research Council in Brazil, suggest a number of areas for further research that would be helpful.
Several small biomonitoring studies that have been performed need to be repeated with large reference populations, said the report. It is imperative that estimates of urinary BPA levels over 24 hours be undertaken [and] there is a need to obtain multiple samples of blood and urine from individuals to assess variability of exposure over time, likely encompassing weeks, months or years.
The report also said that large-scale biomonitoring studies are needed to confirm levels of total and unconjugated BPA in blood, and that such studies need to compare exposure levels in men and women, adults, neonates and children, and pregnant and non-pregnant women.
Developmental periods (in utero and the neonatal periods) are the most sensitive to BPA, thus there needs to be special attention to assessment of total and unconjugated BPA in these vulnerable populations, it said.
The group of researchers also suggested that more research be conducted to examine the pregnancy outcomes from large groups of racially and socioeconomically diverse women to see how they differ, and that more research is needed to identify all sources of exposure and assess daily doses of BPA actually coming from the oral route versus other routes of exposure.
And although the report said the two existing toxicokinetic studies had significant flaws, it said more would be helpful.
What is needed, according to the report, is human toxicokinetic studies, following administration of BPA, employing sensitive methods across physiologic states and age groups.
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