A world avoided: impacts of changes in anthropogenic emissions on the burden and effects of air pollutants in Europe and North America.

Emissions from anthropogenic activity are known to have deleterious impacts on human and ecosystem health and as such a significant amount of time, effort and money has been spent developing legislation to minimise their effects. Here we use a state of the art coupled chemistry-climate model HadGEM2-ES, with extended tropospheric chemistry, to assess the impacts that changes in emissions from anthropogenic activity have had on the burden and impacts of air pollutants over the last three decades. We use HadGEM2-ES to assess an alternative trajectory in air pollutant emissions to that which we have seen, with a regional focus on the contiguous United States and areas of Western Europe. This alternative trajectory can be considered to reflect a world avoided. In this world avoided, the significant levels of air pollution legislation imposed over the last three decades are simulated to not have come into effect in the contiguous United States and Western Europe. Rather a business as usual emission scenario is followed from 1970 to the present day. By combining the results of simulations of the world avoided with a base case present day atmosphere our model runs demonstrate that as a result of air pollution legislation, over 500 000 early mortalities a year have been mitigated owing to extensive reduction in sulfate aerosol and up to 8000 early mortalities a year have been mitigated as a result of improvements in ozone and nitrogen dioxide pollution. These results highlight the important role of legislation in reducing air pollution related mortality in these areas of the globe and highlight a compelling case for developing regions to follow.