In February this year, the US Maryland DC Society of Clinical Oncologists issued the most unequivocal statement yet about bisphenol A, saying: "Make no mistake about it: the research is clear and reproducible in multiple studies. This product is dangerous."
Which is a stark statement to make about a substance widely found in food packaging, linings of tins and drinks, dental sealant and polycarbonate plastics and which biomonitoring studies have found is present in 92 per cent of adults.
Health problems have been discovered in the overwhelming majority of published studies. Animal research has connected bisphenol A (BPA) exposure to a range of health problems including metabolic disorders and obesity, male fertility problems, asthma and intestinal inflammation. Recent human epidemiological research has implicated BPA exposure in elevated risk of heart disease.
Research focusing on the effects of prenatal exposure strongly suggests that exposure to BPA in the womb pre-programmes adult health problems. Nor are these effects being observed at high doses, but at the levels at which people have BPA in their blood – levels which are much lower than that permitted by regulators.
Human data is undoubtedly lacking. There are technical reasons for this: with BPA, the simple ubiquity of exposure presents a serious challenge. Where researchers can easily compare groups of smokers to groups of non-smokers to determine the effects of smoking, with BPA it is very hard to isolate people who are exposed from people who are not. The 20-, 30- or 40-year delay between exposure and health consequence also makes it difficult to identify health effects.
There is also the issue of ethical constraints on research: we can't test potentially harmful chemicals on pregnant women to find out about health effects on their children, making researchers dependent on animal studies.
But, given that almost everyone has BPA in their bodies, and that the children of pregnant women are exposed even before birth to a chemical with demonstrated potential to pre-programme animals for adult illness, the question to ask must be: given the evidence we already have, is it really sensible to wait and see what effects BPA has in people before restricting use of the chemical?
Paul Whaley is communications manager for the Cancer Prevention and Education Society