Bisphenol A Safety Confirmed In Final National Toxicology Program Report
September 4, 2008
The US National Toxicology Program’s (NTP) final report on the potential for exposure to bisphenol A to affect human reproduction or development found no direct evidence for health effects in people. It also confirmed that human exposure to bisphenol A is very low.
NTP’s overall conclusions are expressed on its standard five-level scale ranging from ‘serious concern’ to ‘negligible concern.’ NTP reported no concerns for any age group at the top two levels and only negligible concern for adult men and women. Based on limited and inconclusive evidence from laboratory animal studies, NTP expressed ‘minimal concern’ regarding effects on the mammary gland and an earlier age for puberty in females, and ‘some concern’ regarding effects on the brain, behavior, and the prostate gland. However, NTP further noted that additional research is needed to better understand whether the findings from these studies are of any human health significance.
The NTP report is designed to serve as a resource to regulatory agencies engaged in safety assessments of bisphenol A. An August 14 draft assessment from the US Food and Drug Administration, based on a draft of the NTP report and reviewing the same data, reaffirmed the safety of products made from polycarbonate plastic and epoxy resins (e.g., baby bottles, water bottles, food containers), including products intended for use by infants and children.
Who Is NTP and Why Did They Issue a Report on Bisphenol A?
The National Toxicology Program (NTP) is a US government program that, among other things, provides scientific information to other government agencies, scientific and medical communities, and to the public on the potential toxicity of chemicals.(1)
One part of NTP is the Center for the Evaluation of Risks to Human Reproduction (CERHR), which serves as an environmental health resource by providing science-based assessments of the potential for adverse effects on reproduction and development caused by agents to which people may be exposed. The assessments are accomplished through rigorous evaluations of the scientific literature by independent panels of scientists.(2)
Near the end of 2007, a CERHR expert panel on bisphenol A published their final report, which is an advisory document that represents the views of the expert panel members.(3) As part of the normal CERHR evaluation process, NTP prepares an additional report known as a ‘Brief’ that represents NTP’s views.
The final NTP Brief on bisphenol A, which has now been published,(4) is based primarily on the CERHR expert panel report and any significant new information that became available after the CERHR report was completed. The Brief has also been peer-reviewed by the NTP Board of Scientific Counselors.
What Were the Conclusions of the Report?
The NTP report confirmed that human exposure to bisphenol A is very low and stated “there is no direct evidence that exposure of people to bisphenol A adversely affects reproduction or development.” Due to various limitations, the small number of available studies that looked for associations between bisphenol A exposure and health effects in people do not support a conclusion that people are adversely affected by exposure to bisphenol A.
In contrast to the small number of studies that looked for health effects directly in people, hundreds of studies on laboratory animals are available. Regarding studies that have reported effects from low doses of bisphenol A, NTP noted that these studies: “have proven to be controversial for a variety of reasons including concern for insufficient replication by independent investigators, questions on the suitability of various experimental approaches, relevance of the specific animal model used for evaluating potential human health risks, and incomplete understanding or agreement on the potential adverse nature of reported effects.”
Based on the weight of scientific evidence from all the studies it reviewed on laboratory animals and humans, NTP expressed the following overall conclusions on its standard qualitative five-level scale.(5)
- No concerns were found at the top two levels for any health effect or any age group.
- For adult men and women, NTP expressed ‘negligible concern’ that exposure to bisphenol A causes reproductive effects or will result in fetal or neonatal mortality, birth defects or reduced birth weight and growth in their offspring.
- For fetuses, infants and children, NTP expressed ‘minimal concern’ regarding effects on the mammary gland and an earlier age for puberty in females, and ‘some concern’ regarding effects on the brain, behavior and the prostate gland. However, due to the many limitations noted above, NTP commented that the laboratory animal studies supporting these conclusions “only provide limited evidence for adverse effects on development and more research is needed to better understand their implications for human health.”
NTP’s comments on each of the potential health effects of some or minimal concern further underscore the limitations of the laboratory animal studies that support these conclusions:
- Brain and behavior effects: “the current literature cannot yet be fully interpreted for biological or experimental consistency or for relevance to human health.”
- Prostate gland: “the evidence is not sufficient to conclude that bisphenol A is a rodent prostate gland carcinogen or that bisphenol A presents a prostate cancer hazard to humans,” and “it is important to note that other studies have not reported severe consequences of urinary tract constriction in adult animals exposed during development that might be predicted”.
- Mammary gland: “the evidence is not sufficient to conclude that bisphenol A is a rodent mammary gland carcinogen or that bisphenol A presents a breast cancer hazard to humans.”
- Puberty: “limited data are available at low doses to suggest an effect of accelerating the onset of puberty in female mice.”
How Will the Report Be Used?
The NTP Brief, in combination with the CERHR expert panel report, provides a comprehensive evaluation of the scientific literature on bisphenol A. Based on the weight of evidence, NTP reports overall conclusions on potential reproductive and developmental hazards associated with bisphenol A, but the NTP Brief itself does not assess the safety of bisphenol A as it is actually used. The NTP Brief will be useful to other US government agencies that have regulatory responsibility for the safety of bisphenol A in consumer products.
Starting with a draft of the NTP Brief that was available earlier this year and reviewing the same scientific data, the US Food and Drug Administration (FDA) has already conducted an assessment of the safety of bisphenol A in food-contact products made from polycarbonate plastic and epoxy resins (e.g., baby bottles, water bottles and food containers). Key studies and potential health hazards identified in the NTP Brief were independently analyzed by FDA scientists and combined with additional information on human exposure to draw conclusions on the safety of these products. The draft FDA assessment(6), which will be peer-reviewed and finalized later this year, reaffirms the safety of products made from polycarbonate plastic and epoxy resins, including products intended for use by infants and children.
Overall, the FDA assessment states: “FDA concludes that an adequate margin of safety exists for BPA at current levels of exposure from food contact uses, for infants and adults.” The findings of the draft FDA assessment are consistent with and further support the conclusions of many earlier evaluations by other government agencies that bisphenol A is not a risk to human health at the low levels to which people might be exposed.
(5) The five levels of concern used by NTP are from highest to lowest: serious concern, concern, some concern, minimal concern, and negligible concern.