The power of clean water

This study examines the long-term benefits of early-life exposure to city-wide water filtration systems introduced in 25 major American cities in the early 20th century. The findings show that exposure to cleaner water adds about 3.2 months to old-age male longevity. This increase represents roughly 2 percent of the total gain in life expectancy for cohorts born between 1900 and 1940, during which male life expectancy rose by about 174 months. Approximately 15.6 percent of individuals in the sample were fully exposed to these improvements, resulting in an estimated 14,100 life years gained overall. When translated into economic terms using the Value of Statistical Life, this longevity improvement corresponds to roughly $2 billion in benefits. The study carefully rules out confounding factors and policy overlaps, confirming the lasting impact of improved water quality on health