health at imperial college london, and he did a review of the global evidence on health impacts of low emission and congestion charging zones. good to talk to you, thanks to speaking to us. let me ask first, how does one go about analysing the health impacts of these kinds of the emission zones in cities? it’s a emission zones in cities? it s a aood emission zones in cities? it s a good question- emission zones in cities? it s a good question. there - emission zones in cities? it s a good question. there are - emission zones in cities? it s . good question. there are different ways you can do it, but what we did is we searched through all of the published evidence on globally, if you look at schemes that have measured health impacts before, after similar schemes have been implemented, so we really read all that evidence, to get the combined picture, up to date, what the global evidence says and really, what we find is, we find pretty consistent evidence that cardiovascular disease