Canada has become the first country in the world to officially declare bisphenol A (BPA) – a common plasticizer found in food containers – to be a toxic substance. (Globe and Mail)

BPA has been linked to an increased risk of cardiovascular disease and diabetes in humans. And animal studies have suggested that since BPA mimics the hormone oestrogen, it can disrupt normal hormone signalling – particularly worrying if foetuses or young babies are exposed to significant amounts of the substances.

How much exposure is too much, though? There is no clear answer. Two weeks ago, the European Food Safety Authority declared that BPA did not pose sufficient risk to stop using it in food containers. While tiny amounts can leach out into food, they cannot raise human exposure to unacceptably risky levels, the authority concluded after an assessment of existing scientific studies.

The US Food and Drug Administration has reached similar conclusions, although it is “taking reasonable steps to reduce human exposure to BPA in the food supply”.

Canada, however, has been more cautious – it banned BPA from baby bottles in 2008. The government says it has no immediate plans to ban BPA from all food packaging.

Earlier this year, a Nature news feature highlighted the difficulties in drawing firm conclusions about the effects of BPA based on the wide range of different animal studies – some of which involve injecting, rather than ingesting, the substance. Until more studies are completed, the debate will undoubtedly continue.