Research by D. Mark Anderson, Kerwin Kofi Charles & Daniel I. Rees in the NBER report provides some useful graphs looking at how various public health interventions have impacted health outcomes in the U.S over the last century. Specifically, the authors show that public health interventions aimed at improving the health of the municipal water supply had large impacts on both mortality for some groups, illness, and inequality of health outcomes. Regarding the latter point, the authors find that:
…chlorinating the water supply, which was relatively cheap, had no observable effect on the White infant mortality rate (IMR), but led to a 9 percent reduction in the Black IMR and a 10 percent reduction in the Black-White IMR ratio — our measure of the Black-White infant mortality gap. Moreover, we found that adding chlorine to the water supply narrowed the Black-White infant mortality gap, at least in part, through its effect on diarrheal disease.
More details are available here.