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Bisphenol A (BPA) is an industrial chemical that has become ubiquitous in the environment and may have widespread pathophysiologic effects. BPA is an endocrine-disrupting compound that is believed to act as an estrogenic agonist and androgenic antagonist. The chemical has been linked to such disorders as obesity, hypertension, and insulin resistance, as well as attention deficit hyperactivity disorder (ADHD) and autism.
Because the full range of the potential biologic effects of BPA remains unclear, many investigations are in progress. Although more confirmatory studies are needed regarding its biologic effects, it is estimated that greater than 93% of adults in the United States have levels of BPA in the urine, indicating significant exposure.1
BPA is used in the manufacture of certain plastics and resins. It is found in such items as canned foods and beverages, baby bottles, dishware, toys, DVDs, hospital plastics, laboratory equipment, and dental sealants (Table 1). In most cases of exposure, BPA leaches into food and beverages from resin-coated containers and is ingested.
Until recently, BPA was believed to be harmless and has been used in the manufacture of plastics since the 1950s. Because it was known early on that BPA leached from containers into foods and beverages, scientists have been investigating the chemical for many years through animal testing. However, BPA has primarily been examined for its cancer-causing potential and has been found to be noncarcinogenic in the small doses found in food.
|Table 1. Items that contain BPA|
|Canned food||Fax paper|
|Canned beverages||Medical plastics and tubing|
|Canned liquid infant formula||Pacifier shields|
|CDs||Plastic baby bottles|
|Cell phones||Plastic laboratory equipment|
|Children’s toys||Plastic tableware|
|Coated paper used in receipts||Plastic water bottles|
|Dental sealants||Recycled paper products|
|DVDs||White dental fillings|
In the early 1980s, the FDA, National Cancer Institute, and U.S. Environmental Protection Agency (EPA) found no convincing evidence of BPA carcinogenicity in the doses found in water or food. By the late 1980s, U.S. production of BPA reached billions of pounds per year and was used in the manufacture of a growing number and variety of consumer goods.2 Once it had been deemed noncarcinogenic, few studies focused on other biologic effects of BPA.
How BPA exposure occurs
More than 90% of BPA exposure is derived from food or fluid containing BPA that has leached out from plastic- or resin-coated containers.3 The leaching of BPA into food or beverage is greatest when the container is heated or damaged.
The chemical is absorbed through the GI tract and is metabolized by the liver. From the liver, BPA metabolites are transported to the kidneys and excreted in the urine. BPA can cross the placenta and may be found in amniotic fluid.4
Between 1997 and 2005, 115 studies in the United States, Europe, and Japan were conducted on the biologic effects of BPA on animals. The proven effects of BPA on animals included fetal prostate and mammary gland maldevelopment, disruption in the chromosomal alignment in the developing eggs of females, altered immune function, metabolic abnormalities, and changes in brain and behavior (Table 2).1,3,5
Table 2. Effects of BPA demonstrated in animal studies
|Female reproductive system||Male reproductive system|
|Precocious puberty||Reduction in/loss of sexual dimorphism in brain|
|Breast lesions||Reduction in sexually dimorphic behaviors|
|Early breast fat-pad maturation||Decreased sperm counts|
|Enhanced growth in mammary glands||Increased prostate weight|
|Epigenetic programming in mammary glands||Prostatic lesions|
|Ovarian cysts||Altered prostate development|
|Endometrial hyperplasia||Epigenetic programming of the prostate|
|Obesity||Alterations in lipid metabolism|
|Alterations in insulin sensitivity||—|
|Epigenetic programming of the brain structure and behavior|
|Disturbance of the estrous cycle||Alterations in the immune system|