In the early twentieth century, cities grew rapidly – while the basic tenants of safety, like clean drinking water, often fell by the wayside.
As a result, water trickling from household faucets often carried dangerous diseases, including typhoid and dysentery, especially after heavy rain.
Scientists experimented with chlorine – toxic in high doses – as a method for killing waterborne bacteria, though many deemed the process too risky for mainstream use.
During a 75-year career, Abel Wolman, a sanitary engineer at Johns Hopkins University, put these fears at ease. In 1918, he helped develop a simple scientific formula for chlorinating tap water by considering factors such as acidity, bacteria levels and purity.
As a result, 85 percent of U.S. water systems were using chlorination to purify water supplies by 1941. In the years that followed, Wolman advised more than 50 foreign governments on proper water sanitation, improving the lives of millions around the world.