Are BPA Products Putting Us at Risk?

A class of plastics found almost everywhere may be responsible for low sperm counts.

Something funny appears to be happening to our sperm. In the 1930s, when systematic measurement of sperm levels began, half of men had over 100 million sperm in each millilitre of semen, but, by the 1990s, having that many sperm would put you among the most fertile 16 per cent of men. On average, sperm counts have dropped one per cent each year for the last 50 years, and the decline shows no signs of ending.

While theories trying to explain this phenomenon abound, an increasing number of fingers are being pointed at a set of chemical additives found in plastics. These additives go by an alphabet soup of different acronyms. Bisphenol A (BPA), polybrominated diphenyl ether (PBDE), and tetrabromobisphenol A (TBBPA) are the most commonly cited culprits, but a group of chemicals called phthalates have also been getting a lot of attention lately. All of these chemicals share two properties: They all do wonderfully useful things when added to plastics, such as making them more flexible or more transparent, and they appear to interact in a much less positive way with the mammalian endocrine system that is responsible for making and using hormones. Some of these chemicals mimic natural sex hormones like estrogen and androgens, while others interact with hormone receptors and change their properties. Collectively, such chemicals are called endocrine disruptors.

In search of a causal link, researchers have been hard at work exposing lab animals to these chemicals to see what happens. When exposed to BPA in utero, male rats develop reduced sperm counts and a wide variety of genital abnormalities that seem similar to disorders seen in humans that go under the macabre umbrella term “testicular dysgenesis syndrome.” While early animal tests involved doses roughly a thousand-fold higher than those found in normal humans, more recent studies have seen measurable effects on fetal rat reproductive organs at levels roughly corresponding to those found in our blood. Last autumn, a study of Chinese factory workers exposed to high levels of BPA was the first to find a direct link between BPA exposure and low sperm count in humans.

The truly scary thing about this group of chemicals is just how omnipresent they are in our lives. In particular, they are in plastic-lined metal food containers such as tuna and soup tins, hard plastic water bottles made with acrylonitrile butadiene styrene (ABS) and polycarbonate, and in the vinyl used for clothes and baby toys. They are also a constituent of dental fillings and cosmetics, and, perhaps most sadly, they make up the lining of nearly all beer cans. Basically, they're everywhere.

What does the government do when chemicals that are in just about everything are shown to have deleterious effects on health? Health Canada, the agency responsible for regulating our food and drugs, remains emphatic that BPA poses no measurable risk, stating in its food safety guide that “the current dietary exposure to BPA through food packaging uses is not expected to pose a health risk to the general population, including newborns and infants,” although it did, in 2008, ban BPA from use in baby bottles. Environment Canada, the agency responsible for regulating toxic chemicals, takes a different view: In October 2010, it declared BPA a toxic chemical, the first step on the road to regulating the use of BPA in Canadian products.

While it may take a while before all the regulatory agencies are on the same page, the momentum is clearly with those trying to ban or limit endocrine disruptors in consumer products, particularly those used by pregnant mothers and children. Until then, the best we poor consumers can do is to try to limit our use of products that might contain them.

Photo courtesy of Reuters.