This thesis consists of three essays in environmental and health economics. The UK Clean Air Act, Black Smoke, and Infant Mortality This paper estimates the effects of the 1956 UK Clean Air Act on infant mortality. Using novel data, I exploit the seasonality in demand for coal to analyze the effects of a staggered expansion of a ban on local smoke emission. The findings show that the policy eliminated the seasonal difference in air quality as well as infant mortality. According to my instrumental variables estimates, the reduction in air pollution between 1957 and 1973 can account for 70 % of the observed decline in infant mortality during the same period. The results are relevant to explain the fast decline in post-war infant mortality in ...