|
September 7 2010
0:47 Beijing
|
|
What's the Latest on the Raging BPA Debate?
.JPG)
NEARLY all experts agree that more studies are needed to determine the toxicological effects of bisphenol A (BPA) on humans. Not that there have been too few studies, but that the results of numerous tests have been contradictory or inconclusive. A number of these findings has led some environmental and consumer groups to call for an outright ban of BPA in containers used for food, whereas some other findings seem to bolster the chemical industry's allegation that BPA as used today is entirely safe.
The issue has even polarized scientists to some extent, and the debate over BPA rages on in mainstream newspapers in the United States as well as in blogs. What is evident is that some "scare factor" is involved in the issue over the effect of BPA as in the somewhat emotion-led campaign to link MMR vaccines to autism, and the generally well-accepted but still controversial decision to ban the use of the artificial sweetener saccharine.
This article will not delve into the opinions of pro-BPA industry groups and anti-BPA consumer advocates. Instead it provides a brief on the latest findings on the possible toxicity of this common plastic additive on humans and where regulatory bodies stand on the use of BPA.
How is BPA Used in Food Packaging?
BPA is one of the most ubiquitous plastic additives, and is found in such objects as sunglasses, CD cases and plastic storage containers.
Bisphenol A is an industrial chemical known as 2,2-bis(4-hydroxyphenyl)- propane (C15H16O2 ) used as the starting material for the production of polycarbonate plastics and synthetic resins. Because of its ability to make plastic rigid, BPA is found in polycarbonate containers that come into contact with foodstuffs such as re-useable water bottles, baby bottles, plastic tableware, and microwaveable and storage plastic containers, and residential and office drinking water storage tanks and wine vats. It is also found in the internal epoxy resin coating (lacquer) on cans, including infant formula cans, used for foods and beverages.
In some circumstances, chemicals in food packaging can migrate into the food product, and vice versa, depending on the nature of the packaging and the food it contains. "BPA exposure in humans through food contact applications may occur through adult use of food contact articles or infant exposure through maternal transfer, the use of ready made (liquid) infant formula or the use of PC plastic bottles," according to the FDA.
In 1988, the Society of the Plastics Industry, Inc. introduced a coding system for different types of plastics for the purpose of simplifying the process of sorting and recycling plastic bottles and containers. Plastics identified by codes 1 through 6 do not use BPA in their manufacturing process. Code 7 is used to identify "Other Plastics", of which polycarbonate is one type; however, the majority of code 7 plastics are not polycarbonate.
Headlines in September
On one Tuesday in September, a study on the effects of the plastic additive on human health again made headlines in the United States. The results of the study likely would have stirred more controversy worldwide if it had not been overtaken by a scandal over another plastic additive, melamine, which unscrupulous traders in China had added to raw milk used to make infant formula and that led to kidney stones or renal failure or both in over 56,000 babies, four of whom died.
Higher levels of urinary BPA, a chemical compound commonly used in plastic packaging for food and beverages, is associated with cardiovascular disease, type 2 diabetes and liver-enzyme abnormalities, according to a study1 in the September 17 issue of JAMA. The study was released to coincide with a US Food and Drug Administration hearing on BPA.
UK scientists including David Melzer, M.B., Ph.D., of Peninsula Medical School, Exeter, examined associations between urinary BPA concentrations and the health status of adults, using data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004. The survey included 1,455 adults, age 18 through 74 years, with measured urinary BPA concentrations.
The researchers found that average BPA concentrations, adjusted for age and sex, appeared higher in those who reported diagnoses of cardiovascular diseases and diabetes. The participants in the highest BPA concentration quartile had nearly three times the odds of cardiovascular disease compared with those in the lowest quartile. Similarly, those in the highest BPA concentration quartile had 2.4 times the odds of diabetes compared with those in the lowest quartile. In addition, higher BPA concentrations were associated with clinically abnormal concentrations for three liver enzymes. No associations with other diagnoses were observed.
"Given the substantial negative effects on adult health that may be associated with increased BPA concentrations and also given the potential for reducing human exposure, our findings deserve scientific follow-up," the authors said.
Earlier, the National Toxicology Program (NTP) Center for the Evaluation of Risks to Human Reproduction (CERHR), released its final report2 on the potential human reproductive and developmental effects of bisphenol A. The NTP, part of the US Department of Health and Human Services, concluded that based on the review of existing literature that some concern exists for effects on the brain, behavior, and prostate gland in fetuses, infants, and children at current human exposures to bisphenol A.
NTP, which has no regulatory oversight, said, "There are insufficient data from studies in humans to reach a conclusion on reproductive or developmental hazards presented by current exposures to bisphenol A, but there is limited evidence of developmental changes occurring in some animal studies at doses that are experienced by humans. It is uncertain if similar changes would occur in humans, but the possibility of adverse health effects cannot be dismissed."
Where Do Regulatory and Safety Bodies Stand?
At present, regulatory agencies in Japan, Canada, Europe and the United States agree that there is no reason to impose a total ban on BPA in food and beverage packaging and containers owing to minimal toxic risks.
AIST. Japan's National Institute of Advanced Industrial Science and Technology has assessed human health risks and ecological risks posed by BPA, and also analyzed the economic impact of risk reduction activities3. The key toxicological endpoints for human health risks posed by BPA were reduction in body weight gain, effects on the liver, and reproductive toxicity. The risks were characterized by using margin of exposures (MOEs) that were calculated by dividing no observed adverse effect level (NOAEL) or benchmark dose lower confidence limit (BMDL) by the daily BPA intakes. The MOEs were sufficiently large (>1,000 in the worse case scenario) for all three endpoints even in case of individuals who had the highest BPA levels, i.e., children aged 1-6 years.
AIST researchers concluded that the current BPA exposure levels were unlikely to pose unacceptable risks to human health. They also concluded that the current exposure levels of BPA were unlikely to pose unacceptable risks to the local populations of aquatic life, particularly fish.
Health Canada. Canada recently completed a risk assessment of BPA under the Chemicals Management Plan, which concludes that in general, most Canadians are exposed to very low levels of BPA in polycarbonate and it does not, therefore, pose a significant health risk.
Levels of BPA reported as migrating from canned food sources are very low, in the range of parts per billion (one billionth gram in a gram of food) and are consistent with levels of BPA reported in canned foods sold worldwide. "To put this into perspective, the average Canadian would need to consume several hundred cans of food per day to reach the tolerable level established by Health Canada [consistent with TDI imposed by EFSA; see below]," the department said.
However, Health Canada wants to be prudent and further reduce exposures of newborns and infants less than 18 months. That is why, as a precautionary measure, the Government of Canada is proposing to ban polycarbonate baby bottles, which are the primary source of BPA exposure for this age group when hot or boiling liquids are added.
EFSA. BPA is rapidly inactivated and then excreted in the urine, according to the European Food Safety Authority, and it has concluded that there is little risk to humans from common plastic additive in consumer products at current levels. EFSA came to this conclusion after an expert panel reported that the human body rapidly metabolizes and eliminates BPA, and therefore it presents no risk to infants, children, or adults.
In 2007, EFSA imposed the tolerable daily intake (TDI) of 0.05 milligram per kg body weight for bisphenol A after a re-assessment of the safety of BPA for use in food contact materials based on new information (including the NHANES data cited earlier). The Tolerable Daily Intake is defined as an estimate of the amount of a substance, expressed on a body weight basis, that can be ingested daily over a lifetime without appreciable risk. (Five years earlier, the European Commission's Scientific Committee on Food issued an opinion on BPA and set a temporary TDI of 0.01 mg/kg body weight. Between 2002 and 2007, nearly 200 further papers relevant to the safety of BPA have been published and the European Commission asked EFSA to re-assess the safety of BPA for use in food contact materials in the light of this important new information.)
Separately, Germany's Federal Institute for Risk Assessment (BfR, the German equivalent to the FDA) evaluated the relevance of both studies and concluded that the results published in these studies do not question the current risk assessment of BPA in food, which is that the substance has low acute toxicity.
FDA. The agency maintains its position that products made with BPA are safe -- its current view is that the levels exposure to the chemical are too low to be dangerous to health, even in infants and children. "Right now, our tentative conclusion is that it's safe, so we're not recommending any change in habits," said Dr Laura Tarantino, director of the FDA Office of Food Additive Safety, Center for Food Safety and Applied Nutrition.
Tarantino said the evidence from animal studies -- of which there a hundreds -- does not support the suggestion that BPA is harmful at the levels currently found in the population. The NHANES 2003-2004 reports that trace amounts in over 90% of those surveyed.
On Tuesday, September 16, the FDA advisory committee met to review the evidence on BPA. The panel is due to give its final recommendations towards the end of October.
What Next?
Proponents of the continued use of BPA in food and beverage packaging will continue to cite the acceptance by regulatory agencies worldwide as a low-risk chemical additive. Scientists who believe that the research data point to the human health risks posed by this chemical compound and consumer advocates will want to see BPA banned from food and beverage containers.
1 Lang IA, Galloway TS, Scarlett A, Henley WE, Depledge M, Wallace RB and Melzer D (Epidemiology and Public Health Group, Peninsula Medical School, Barrack Rd, Exeter EX2 5DW, UK). "Association of urinary bisphenol A concentration with medical disorders and laboratory abnormalities in adults." JAMA. 2008 Sep 17;300(11):1303-10. Epub 2008 Sep 16.
2 ""NTP-CERHR Monograph on the Potential Human Reproductive and Developmental Effects of Bisphenol A" http://cerhr.niehs.nih.gov/chemicals/bisphenol/bisphenol.pdf
3 Junko Nakanishi, NEDO Project Leader, CRM, AIST; Ken-ichi Miyamoto, CRM, AIST;
Hajime Kawasaki, CRM, AIST. "Bisphenol A Risk Assessment Document" http://www.riskcenter.jp/RAD/download01/download01.cgi?BPA_e
|
|
|
|