Today marks the 16th installment in a series of articles by HumanProgress.org titled, Heroes of Progress. This bi-weekly column provides a short introduction to heroes who have made an extraordinary contribution to the wellbeing of humanity. You can find the 15th part of this series here.

Our 16th installment of Heroes of Progress features Abel Wolman and Linn Enslow. These two 20^th century American scientists discovered how to safely use chlorine to purify drinking water. Enslow and Wolman’s formula was perfected in 1923 and thanks to their discovery more than 190 million lives have been saved worldwide so far.

Using chlorine to purify water did not start with Wolman and Enslow. During a cholera epidemic in 1854, chlorine had been used to purify London’s drinking water. Similarly, the first American patent for a water chlorination system was granted in 1888. While it was accepted that chlorine could kill bacteria, little was understood about the cleansing process and, since chlorine can be poisonous to humans, using the chemical for water purification purposes remained dangerous.

In the early 1900s, cities across America were expanding at a rapid pace and luxuries such as indoor running water were becoming more widespread. With no safe or effective measures to clean their drinking water, city water suppliers often became unwitting disseminators of an array of diseases, including cholera, dysentery and typhoid. This is where Wolman and Enslow enter our story.

Abel Wolman was born in June 1892, in Baltimore, Maryland. Wolman was one of six children of Polish-Jewish immigrants to America. Although Wolman had initially wanted to go into medicine, his parents encouraged him to study engineering. In 1915, Wolman became the fourth person to receive a BS degree from John Hopkins University’s newly established Engineering School.

Linn Enslow was born in February 1891 in Richmond, Virginia. Enslow studied chemistry at John Hopkins University and it was there that he first met Wolman. After graduation, both Enslow and Wolman began working at the Maryland Department of Public Health. In 1918, the pair teamed up to study chlorine’s effect on water purification.

In creating their method of water purification, Enslow and Wolman analyzed chlorine’s effect on the acidity, bacterial content and taste of drinking water. By 1923, the pair had created a standard formula detailing the amount of chlorine needed to safely purify water supplies. Enslow and Wolman’s rigorous scientific research laid the foundation for water purification across the world.

After their breakthrough, Wolman took a more active role than Enslow in encouraging states and countries to adopt the formula. Eventually Wolman was able to apply the new water purification method to Maryland’s drinking water supply. By 1930, typhoid cases in the state had declined by 92 percent. By 1941, 85 percent of all U.S. water systems used the Enslow-Wolman formula. The rest of the world followed America’s lead.

Wolman’s career flourished. He became chair of the state Planning Commission in his early 30s, acted as a consultant to the U.S. Public Health Service, was the Chief Engineer at the Maryland Department of Public Health, and established the Department of Sanitary Engineering at The Johns Hopkins University in 1937

Throughout his life, Wolman sat on numerous boards and advised governments on water purification systems throughout the world. Wolman eventually retired in 1962. He died in 1989 in his native Baltimore at the age of 96.

In the meantime, Enslow went on to become the editor of the magazine Water and Sewage Works. He worked in that role until his sudden death from a heart attack in 1957.

Thanks to the work of Enslow and Wolman, billions of people now have access to drinking water that is free from an array of potentially deadly diseases. It is estimated that the adoption of their formula in water systems worldwide has saved almost 200 million lives. It is for this reason that Linn Enslow and Abel Wolman are our 16^th Heroes of Progress.

PS: Linn Enslow is on the left of our cover picture and Abel Wolman is on the right of our cover picture.