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 Bisphenol A -- the Hormone-Disrupting Plastic Building Block Minimize

Bisphenol A (or BPA) is a high-volume industrial chemical used as a monomer (or chemical backbone) to make polycarbonate plastic, which is widely used in reusable water bottles, baby bottles, pacifiers, plastic utensils, children’s toys, compact discs, and certain microwaveable and reusable plastic containers. BPA is also used in some dyes, enamels, varnishes, flooring, adhesive, fungicides, antioxidants, dental sealants and artificial teeth. A chemical derivative of BPA called bisphenol A diglycidyl ether (BADGE) is used to make epoxy resins which are widely used in many applications. Human exposure to bisphenol A (and BADGE) results from the use of BADGE in the clear lining of metal food and drink cans, and from some dental sealants and composite dental fillings.

Over time, bisphenol A migrates from cans into food and leaches from polycarbonate plastic bottles, especially when the plastic is heated or as it ages. As evidence of the chemical’s “leaky” nature, BPA has been found in 40% of stream water samples surveyed by the U.S. Geological Survey. Humans are exposed through ingesting contaminated food, liquids and breast milk, and during some dental procedures.

Bisphenol A in Maine People

We tested the blood of our Maine participants for both bisphenol A and for a metabolite of BADGE known as BADGE-4OH which forms in the body. Since BPA and BADGE are not persistent in the body, detection reflects recent exposure.

Figure 4 shows that bisphenol A was found in three women of the Mainers tested, at levels ranging from 3.75 to 6.64 parts per billion. These results range from six to ten times greater than the average blood levels of BPA reported in one study of 14 women published in the scientific literature, and were also higher than the median and average in two other small studies (see Table 3 in the Appendix).

The related BADGE metabolite was found in five of the Maine participants, including the same three people with detectable levels of BPA in their blood. The two highest of the five reported Maine levels for BADGE-4OH (59.7 ppb and 119 ppb) were more than five to ten times greater than the geometric mean level of about 9.33 parts per billion resulting from one other small study (see Table 3).

Vi Raymond and Elise Roux had the highest levels of bisphenol A and BADGE exposure. Their results were significantly higher than the average levels reported elsewhere. We cannot explain their elevated levels of bisphenol A and its related compound based on their exposure surveys. The fact that these chemicals have been used in a multitude of products makes it difficult to determine the source of exposure.

Figure 4: Bisphenol A and BADGE levels, measured in blood serum. The horizontal line is the mean BPA level for women (Takeuchi, 2002). ND = none detected.

HEALTH EFFECTS: Ultra Low-Dose Hormone Disruptor

Bisphenol A is a potent endocrine disrupting chemical in lab animals at very low doses that is suspected of causing reproductive damage and birth defects that may lead to prostate and breast cancer. Studies have found that BPA can have adverse health effects at levels thousands of times lower than what the EPA considers safe. According to the low dose hypothesis, small and repeated exposures to bisphenol A can have an amplified effect on the human body by mimicking human sex hormones, or promoting cell proliferation. Bisphenol A has been found to cause estrogenic changes in animal cells at the same concentrations that are found in pregnant women and their fetuses.

Controversy over toxicity exists between public health advocates and the plastics industry, which describes bisphenol A as a weak estrogen, and says there is little concern with human exposure levels. Between 1998 and 2005, 115 studies of BPA were published. None of the 11 studies funded by industry reported adverse effects at low level exposures, whereas 94 of 104 government-funded studies found statistically significant effects on animals. Adverse effects were found at levels to which many people in the U.S. are currently exposed, levels much lower than the EPA's current acceptable level.

Much less is known about the risks of exposure to BADGE. Environmental Working Group cites research suggesting strong evidence of hormone activity with limited evidence of other health concerns. They also cite a study showing that in the human body, BADGE can break down into BPA, which raises concerns about the compound’s toxicity.

Policy Changes Needed

Growing scientific evidence on the health effects of very low doses of bisphenol A merits a much more protective Reference Dose (like a safety standard) than currently supported by U.S. EPA. It will be necessary to further reduce public exposure to bisphenol A.

The City and County of San Francisco banned the manufacture, sale, and distribution of child care articles and toys containing bisphenol A and some phthalates for children under three years old as of December 1, 2006. Under the ordinance, San Francisco manufacturers of baby bottles, pacifiers, and toys for young children must replace BPA and phthalates with the least toxic alternatives. A similar measure was introduced in the California Legislature in 2006 but failed to pass. Similar legislation is pending in several states including Maine. All of these policy initiatives have been aggressively challenged by the chemical industry.

A similar concerted effort is needed by government and product manufacturers to switch to safer substitutes for uses of polycarbonate plastic and epoxy resins that may expose the fetus and young children to bisphenol A and BADGE.

Reducing Your Exposure to BPA

Bisphenol A has been used as an ingredient in consumer products for a long time, and is difficult to avoid. In some cases, alternatives are available. Consider these tips, especially if you are or may become pregnant or are parents choosing for a child:

Avoid reusable plastic water and baby bottles. Most Nalgene reusable water bottles are made of polycarbonate plastic that leaches bisphenol A into the water. Use polyethylene or aluminum bottles instead. Use glass baby bottles instead of plastic. Discard old or damaged bottles.

Avoid polycarbonate plastic food containers and table ware. These may be labeled ‘PC’ underneath a plastic code #7 in the recycling triangle on the bottom of the container. (The #7 means ‘other’, so you need to see the ‘PC’ to confirm that the plastic is polycarbonate).

Minimize the use of canned foods and canned drinks. Until industry reformulates the laquer lining of metal cans (as is being done in Japan), choose fresh or frozen foods or glass containers or bottles. A recent study by Environmental Working Group found bisphenol A in more than half of 97 cans of brand-name fruit, vegetables, soda, and other common canned goods.

Ask you dentist for BPA-free sealants and composite fillings. Some dental resins are free from or low in BPA and BADGE. Ask your dentist if they know about BPA and request the MSDS sheet (Material Safety Data Sheet) for the sealants or composite fillings to look for BADGE in the list of ingredients. Make sure your family brushes and flosses regularly to prevent the need for dental work!


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