Chapter 5: Bisphenol A
Originally produced for use as a synthetic hormone in 1936, today bisphenol A (BPA) is manufactured in excess of six billion pounds per year. BPA is most commonly used as the building block of polycarbonate plastic for products such as some baby bottles, reusable water bottles, plastic utensils, compact discs, certain microwaveable plastic containers, and epoxy resins (coatings that line food containers). It is also an additive in a variety of consumer products including plastic toys, dyes, enamels, varnishes, flooring, adhesives, fungicides, antioxidants, dental sealants, and artificial teeth.
Human exposure to bisphenol A results from its use in the clear lining of metal food and drink cans, baby bottles, infant chewing toys, reusable water bottles, and from some dental sealants and composite dental fillings. Over time, bisphenol A migrates from cans into food83 and leaches from polycarbonate plastic bottles, especially when the plastic is heated or as it ages.84 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.85 Humans are exposed through ingesting contaminated food, liquids, and breast milk, and during some dental procedures.
Bisphenol A in Oregonians
We tested the urine of the Oregon participants for exposure to bisphenol A. Since BPA is not persistent in the body, the results only reflect recent exposure.
Figure 7 shows that bisphenol A was found in eight of the ten Oregonians tested, at levels ranging from 0.86 to 5.65 ppb, with a median of 1.35 ppb. This median BPA level is similar to the national average median of 1.32 ppb.86 The data in Figure 7 are creatinine-corrected.
Figure 7. Bisphenol A levels, measured in urine and creatinine-corrected. The horizontal line depicts the national median BPA value of 1.32 ppb.87
Two participants, Don Sampson and Linda Hornbuckle, had bisphenol A levels that were higher than 90% of people that have been tested in national biomonitoring studies.88 Linda’s BPA levels, at 5.65 ppb, were four times higher than the Oregon median. We cannot explain Don or Linda’s elevated level of bisphenol A based on exposure surveys. The fact that BPA is used in a multitude of products makes it difficult to determine the source of exposure.
Health Effects of Bisphenol A
Bisphenol A is a potent endocrine-disrupting chemical in lab animals at very low doses.89 A number of animal studies have concluded that low-dose BPA exposure is associated with a variety of adverse health effects including reduced sperm count, impaired immune system functioning, increases in prostate tumor proliferation, altered prostate and uterus development, insulin resistance, alteration of brain chemistry, early puberty, and behavioral changes.90 Very low doses of BPA have been shown to cause chromosomal aberrations, referred to as aneuploidy in mice during cell division.91 Aneuploidy in humans is responsible for 10-20% of all birth defects.
Multiple animal studies implicate bisphenol A in many of our biggest contemporary public health problems, including diabetes and obesity, hyperactivity, and infertility. A number of studies conducted on mice show an increase in postnatal growth as a result of maternal doses of BPA between 2.4 and 500 ppb per day.92
Accelerated postnatal growth is associated with obesity, insulin-resistant diabetes, hypertension, and heart disease. Additionally, low-level, chronic exposure to BPA causes insulin resistance in adult mice.93 In humans, insulin resistance can lead to type II diabetes, hypertension and cardiovascular disease. A small 2005 prospective study found that higher BPA exposure is associated with recurrent miscarriages in human females.94
Controversy over the toxicity of bisphenol A exists between public health advocates and the plastics industry, which 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 level the EPA considers safe.95
Policy Changes Needed
Current regulations need to reflect up to date scientific evidence to protect the public’s health. The last EPA risk assessment for bisphenol A was based on research conducted in the 1980s and did not consider more recent evidence of low-level effects. The most recent risk assessment of BPA was based on a comprehensive review of the scientific literature conducted in 1998 by the European Union, with some selected articles added through 2001, at which time few of the current 151 low-dose BPA studies had been published.
The most recent review of scientific studies shows effects from exposure to BPA at levels significantly below the current “safe exposure” level established by the U.S. based on experiments conducted prior to 1988. Growing scientific evidence on the health effects of very low doses of BPA merits a much more protective reference dose (similar to a safety standard) than currently supported by the EPA. It will be necessary to further reduce public exposure to BPA.
At the state level, bills have been introduced in New York and California to prohibit manufacture, sale or distribution of toys or child care products that contain BPA (the same bills also cover phthalates, mentioned in Chapter 1).
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, 2006.96 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.
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.97 Consider these tips, especially if you are or may become pregnant or are choosing a product for a child:
Avoid reusable polycarbonate plastic water and baby bottles. As a general rule, avoid baby bottles labeled #7, which tend to be hard and clear, and polycarbonate reusable water bottles, which include many of the popular colored bottles like Nalgene. Leaching of bisphenol A can occur into formula, expressed breast milk, water and other liquids placed in these products. Choose polyethylene or metal bottles instead. Use glass baby bottles instead of plastic. If you prefer plastic baby bottles, choose milky or opaque colored baby bottles. 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 lacquer 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.98
Ask your dentist for BPA-free sealants and composite fillings. Some dental resins are free from or low in BPA. Ask your dentist if they know about BPA and request the Material Safety Data Sheet for the sealants or composite fillings to look for BADGE (a chemical derivative of BPA) in the list of ingredients. Make sure your family brushes and flosses regularly to prevent the need for dental work.
