Exposure to bisphenol A in Canada: invoking the precautionary principle.

1 environmental advocates, regulatory agencies and the mainstream press have given much attention to the possible harm to health posed by bisphenol A. Bisphenol A is one of the most manufactured chemicals worldwide — more than three million tonnes of it are produced each year — and human exposure throughout the developed world is thought to be ubiquitous. Because bisphenol A has estrogenic properties in vitro and in vivo, there are concerns that perinatal exposure to the chemical can alter the development of several organs and organ systems. Animals exposed to low doses of bisphenol A during the perinatal period showed malformations or altered development of the male and female reproductive tracts, the mammary glands and the brain. These animals also displayed abnormal behaviours, had reduced fertility and often became obese or showed symptoms of metabolic syndrome. Bisphenol A predisposed rodents to cancer of the prostate and breasts, and increased the sensitivity of some of the animals to carcinogens. These effects were seen when animals were exposed to concentrations of bisphenol A similar to the levels to which humans are exposed. As an ingredient of polycarbonate plastics, bisphenol A is found in consumer products such as baby bottles, reusable water bottles, sports equipment, the lenses of eyeglasses, compact discs and im plantable medical devices. It is also a component of the epoxy resins that coat the insides of food and beverage cans and of the resins used in some plastic water pipes, dental sealants and paints. Recent studies have shown that bisphenol A is present in or on a wide variety of papers and cardboards, including cash register receipts, papers used for wrapping food, cigarette filters and American banknotes. Studies have clearly shown that bisphenol A leaches from consumer products under normal conditions of use, and that high temperatures and exposure to acidic or basic solutions can increase the amount of bisphenol A that leaches from coatings and plastics. A recent review examined more than 80 biomonitoring studies that measured the concentrations of bisphenol A in human urine, blood, saliva, breast milk, and the tissues and fluids associated with pregnancy. These studies examined thousands of people from the United States, Japan, Korea, China, Germany, the Netherlands and other nations in the European Union. Al though each of these studies reported the presence of bisphenol A and its metabolites in healthy individuals, some of the larger studies on reference populations allowed statistical comparisons to be made by age, sex and other demographic factors. A recent large-scale study examining 5476 Canadians reported that most were exposed to bisphenol A at levels similar to those that have been described elsewhere. This study, the largest conducted to date, provides us with the opportunity to compare subpopulations and to consider the relevance of current levels of human exposure.