This paper evaluates the negative causal effect of environmental tobacco exposure on health by exploiting the time and geographical variation in public-place smoking bans implemented in Switzerland between 2007 and 2011. Using monthly data from the universe of Swiss hospitals between 2004 and 2012, we show that the incidence of acute myocardial infarction hospitalization decreases by about 10-12% immediately after the law implementation. We also find evidence of heterogeneity by age and sex and across income and education groups. In particular, the policy affected mainly men aged 50+ and the regions characterized by a lower level of income and education. We support our findings using survey data from the Swiss Health Survey showing that after the policy implementation there was a dramatic reduction in passive smoking especially among population subgroups for which we find the largest reductions in hospitalization.