"Higher pollution leads to worse returns for stock prices. Specifically, a usual (meaning greater than one standard deviation) increase in fine particulate matter (PM2.5) leads to an 11.9% reduction in the performance of the S&P 500 index. To be clear, this is not an 11.9% drop, but an 11.9% decline in relative returns."
For more, see http://www.aaii.com/journal/article/pollution-hurts-stock-returns.
