 Bisphenol A, or BPA, is one of those synthetic chemicals that regularly hits the headlines. It's used in polycarbonate plastics, food can liners, thermal till receipts and other everyday objects, and most people have small amounts of it in their body. But are these levels safe, or do we have a problem? These are questions scientists the world over have been grappling with for some time, and just recently, the latest in a line of extensive expert reviews was published by the European Food Safety Agency, or EFSA. The review, which analyses and interprets the latest science on BPA and human health risks, is a whopping 500 pages long, so on the assumption that most people are more likely to use it as a doorstop than read every last word, here are the highlights. The review takes a weight of evidence approach to making sense of a large number of published studies. This is a bit like reconstructing a scene from a bunch of smartphone photos, some are crisp, some are blurry, some focus on minute details while others are so distant they lack any detail at all. You even have some selfies in there. None of them paint a complete picture, and on their own some can be downright misleading, but stitched together they give a good idea of what's going on. In the same way, a weight of evidence assessment helps construct the likely risks associated with a chemical-like BPA from a series of scientific snapshots. In this case, the review has found evidence for a number of health-related impacts following exposure to BPA, including potential impacts on the liver, kidneys and breasts. Many of these raised concerns, but the one that dominated all others at a given exposure level was kidney weight gain in mice. This was identified as the critical end point, the one that if dealt with would also mean that the other potential health impacts should be avoided. Using data from mice, the review has estimated that if an average person was exposed to 113 micrograms of BPA per day for every kilogram that they weighed, their health could be at risk. That's around 8mg of BPA per day for an adult. From here, the next step was to work out what an acceptably safe level would be in people. This is what's referred to as the Tolerable Daily Intake, or TDI. Accounting for differences between mice and people, as well as differences between individuals, the reviewers came up with a draft TDI of 5 micrograms per day per kilogram of body weight. From the available data, they concluded that at this level, no significant health effects would occur in most people, even accounting for uncertainty in the current state of science. This does of course leave a couple of questions. What levels of BPA are most people exposed to? And what if you're not most people? The first question was addressed in an earlier report from EFSA that looked at typical exposure levels. They found that teenagers seem to have the highest exposure to BPA, with an estimated upper level in this analysis of 1.3 micrograms per day per kilogram body weight. For comparison, this is four times lower than the proposed safe level. So for most people, everyday exposures to BPA are probably pretty safe. But what if you're not the same as most people? When adults, BPA is quickly converted into a relatively benign form and got rid of pretty fast. Researchers indicating though that embryos, fetuses and even young children don't handle BPA in the same way as grown adults. Which means that what is okay for most people may not be quite as okay for the very young and the unborn. These are some of the blurry bits in the BPA safety picture that are still being researched. That said, at least we do have a picture of BPA safety, imperfect though it may be. Which would seem to be better for making informed decisions than having no picture at all, which is where we are with some alternatives to not using BPA in products. If you have any thoughts on BPA's benefits and risks, please join the conversation in the comments and remember to check out the additional resources in the blurb below.