Can exposure to plastics harm your health? It’s a question currently being explored by researchers after a recent study suggested that traces of a synthetic chemical called Bisphenol A (BPA) can be found in more than 80 per cent of teenagers.
BPA is added to plastic to create a special form called polycarbonate plastic, used in making robust, impact-resistant materials for everything from food and drink packaging to DVD cases and medical devices. First created in 1891, it has been used commercially since the 1950s and is now one of the most commonly produced chemicals in the world, with 3.6bn tonnes of BPA generated every year.
The problem is that BPA can be ingested or absorbed through skin contact, meaning that humans are regularly exposed through the chemical leaching out of packaging into food and drink – and over the past 20 years various studies have linked BPA to a variety of adverse health effects. The biggest concerns have been the impact on foetuses and young children, who have underdeveloped systems for detoxifying chemicals – the consequences being that the younger you are, the higher the levels of BPA in your body.
Once in the human body, BPA mimics the action of the hormone oestrogen and disrupts the endocrine system – the glands that produce hormones regulating, among other things, metabolism, growth, sexual function and sleep. Studies examining the effects of very high doses of BPA in mice have shown that this can cause problems with liver and kidney function, and mammary gland development. While these studies involve much higher doses than the general public would ever be exposed to, there are concerns that the levels of BPA that accumulate in infants can still have adverse developmental consequences, leading to neurobehavioural and immune system abnormalities.
As a result, in the US, the Food and Drug Administration has banned BPA use in baby bottles and infant feeding cups. However, in teenagers and adults, the exact health risk posed by persistent levels of BPA in our systems remains controversial.
Most notably it has been linked to male infertility through decreasing sperm quality, but in addition a number of scientists believe that continuous BPA exposure, altering normal hormonal signalling in the body, may be a component in the development of a number of chronic diseases.
One study in mice found a link between BPA exposure and an increased risk of type 2 diabetes and insulin resistance, while others have explored a potential relationship between BPA exposure and coronary artery disease due to potential alterations in cardiac function over a long period of time.
Some have even suggested an association between BPA and breast cancer as, with only 10-15 per cent of breast cancer cases linked to hereditary factors, chemical exposure may be among the environmental factors driving the remaining cases.
The problem is that it is hard to get concrete proof that BPA is definitively involved in many of these diseases. "Obviously, it's not ethically possible to experiment with humans, so most of the studies have been in test tubes or animals, and then scientists extrapolate from that what might be happening in humans," says Tamara Galloway, a professor of ecotoxicology at the University of Exeter.
“There have also been epidemiological studies where we measure the concentration of BPA in people’s bodies, look at what they’re suffering from, and then infer an association. But because you can’t establish a direct causal link, it’s hard to make strong conclusions, and that’s what causes the controversy.”
However, precautionary measures are still being taken.
After a review of the scientific literature, and in light of the health uncertainties, the European Food Safety Authority saw enough to order a reduction in the tolerable daily intake that we're allowed to be exposed to in food and drink packaging. In France, the national agency for food, environmental and occupational health has gone even further, completely banning the use of BPA in any packaging that comes into contact with food.
One of the problems is that, even with these regulations, it is actually extremely hard to avoid coming into contact with BPA as it’s simply everywhere, from plastic drinks bottles to the epoxy resins that line the cans of tinned food, to the ink on supermarket till receipts. That ink can pass across your skin in small quantities,” Galloway says. “There are now studies looking at the extent of the exposure you can get from handling these receipts.”
And of course, the amount of plastic waste disposal in the environment means that BPA leaches into rivers and soil, and eventually back into our bodies through food or drinking water in a cyclic process. So while the short half-life of BPA in adult humans means that it’s rapidly excreted in a matter of hours, because it’s so ubiquitous in our world, as many as 95 per cent of us will always have traces of BPA in our body through continuous exposure.
Galloway believes there are certain steps we can take to limit our exposure – such as breastfeeding children or ensuring that any baby bottles that we purchase come with a BPA-free label. “You can do things like buying unpackaged fruit and vegetables and avoiding heavily processed and packaged food,” she adds.
In addition, several studies have shown that reheating food in the microwave in plastic polycarbonate containers can speed the transfer of trace amounts of BPA on to the food. Scientists are hoping that publicity around the potential harmful consequences of BPA exposure will encourage more manufacturers to withdraw it from their products, enabling them to analyse whether this is having a notable effect on reducing BPA levels in the population.
“If you go to your average supermarket, you’ll find that a lot of food and drink packaging will have labels saying ‘BPA free’,” Galloway says. “And with regulations like plastic bag bans hopefully reducing the amount of plastic waste in the environment, it’ll be interesting to see if that’s reflected in population levels of exposure – whether they do start to come down.”
– Guardian