Key points:
- 68 percent of Chicago children under age 6 live in households with tap water containing detectable levels of lead.
- “The extent of lead contamination of tap water in Chicago is disheartening—it’s not something we should be seeing in 2024,” researchers say.
- The results suggest racial disparities, with a 10 percentage-point increase in the Hispanic population associated with an 11.2 percent increase in the chance of lead contamination.
A new analysis led by researchers at the Johns Hopkins Bloomberg School of Public Health estimates that 68 percent of Chicago children under age 6 live in households with tap water containing detectable levels of lead.
“The extent of lead contamination of tap water in Chicago is disheartening—it’s not something we should be seeing in 2024,” said study lead author Benjamin Huynh, an assistant professor at Johns Hopkins.
For the analysis, the researchers used machine learning to gauge likely levels of lead in tap water in households across Chicago, based on an existing dataset that included results from 38,385 tap water tests taken from 2016 to 2023. The analysis also relied on the city’s self-reported household survey data to estimate that 19 percent of exposed children—about 129,000 across the city—used unfiltered tap water for drinking.
The threshold the researchers used was the lowest detectable level of lead in the water tests—one part per billion. More than two-thirds—68 percent—of the tests exceeded this level. From this, the machine learning model predicted lead-contaminated water in 75 percent of residential city blocks, covering 68 percent of Chicago children under 6.
The Environmental Protection Agency’s current “action” level for lead in drinking water—the point at which a municipality must take additional steps—is 15 ppb. The analysis found that 9 percent of tests had lead levels over 15 ppb.
The results, published in JAMA Pediatrics, also suggest there are racial disparities. For example, a 10 percentage-point increase in the Hispanic population was associated with an 11.2 percent increase in the chance of lead contamination. The analysis also suggests Hispanic residents of the city were the least likely to drink unfiltered tap water, with 12 percent responding that they did. By contrast, 32 percent of white residents reported using unfiltered tap water as their primary drinking water source.
Many cities still use lead water pipes that were installed prior to their ban. Chicago has more than any other U.S. city—an estimated 400,000 lead pipes that supply water to as many as 2.7 million people. The EPA has proposed that U.S. cities replace all lead water service lines within 10 years. Under the proposal, Chicago would get 40 years to comply, given the disproportionate burden its water infrastructure poses.