Hundreds of thousands of children continue to die each year because of unsafe drinking water. Around two billion people don’t have reliable access to safe drinking water, including over 400 million in Africa, leaving them at risk of getting sick from contaminants and germs in the water. These contaminants can spread diarrheal disease, which killed 233,000 children under five in Africa in 2023.

Treating water with small amounts of chlorine is a simple, well-established, and low-cost way to save children’s lives. Families may add it at home from a small bottle or tablet, take it from a dispenser at the well or tap where they collect water, or get it already mixed into piped water. Pooling findings from a group of randomized evaluations, research shows that water treatment like chlorine can reduce the odds of death among children under five by about one-quarter (24 to 27 percent). Water treatment is a cost-effective way to save a child’s life, comparable to other preventive health products.

Making chlorine free allows many people to access it, and smart delivery design can reach a similar number of people at a lower cost. In Kenya and Malawi, charging even very small prices for chlorine sharply reduced demand, meaning families chose to go without it. Meanwhile, vouchers that let families claim free chlorine from local shops achieved chlorine use as high as door-to-door delivery, at a lower cost.

Governments can now use this evidence to embed sustainable programs. J-PAL Africa's Scaling Access to Safe Water in Africa (SASWA) is working with governments on how best to expand chlorine access through routine maternal and child health services. Pregnant women and families with young children already use these services, which makes them a promising place to try. Governments and their partners should likewise test and adapt other approaches before scaling, looking at how many families water treatment reaches and how regularly they use it.

Providing chlorine for free increases its use far more than charging for the product. Chlorine itself is relatively cheap, but programs also cost money to transport, give out, stock, and promote its use. As with many preventive health products, even very small user fees substantially reduce uptake. Providing chlorine free of charge is therefore critical to reaching families who would otherwise go without it.

A voucher system combines free access for households with lower-cost delivery for the government. In Malawi, families could collect free chlorine from nearby shops using vouchers rather than having it delivered to every home. This approach was nearly twice as cost-effective at increasing chlorine use and four times as cost-effective at preventing child illness: vouchers cost US$2.69 per child illness averted, compared with US$10.62 for universal home delivery.

Delivery innovations also look at how to encourage regular use. Reliable stocks, convenient places to obtain chlorine, and clear instructions all matter. In Nigeria, a community demonstrations program let families learn about E Coli contamination in their local water, see how chlorine is used, and try treated water themselves. Ongoing research is testing how this can increase willingness to use chlorine.

In urban areas, building pipe infrastructure and introducing in-line chlorination can guarantee access to safe water. Planners working on such infrastructure programs should be forward-looking, taking into account how people are moving from rural to urban parts of a country as the economy develops.