More than two-thirds of young children in Chicago could be exposed to lead-contaminated water, according to an estimate by the Johns Hopkins Bloomberg School of Public Health and the Stanford University School of Medicine.

The research, published Monday in the journal JAMA Pediatrics, estimated that 68 percent of children under the age of 6 in Chicago are exposed to lead-contaminated drinking water. Of that group, 19 percent primarily use unfiltered tap water, which was associated with a greater increase in blood lead levels.

“The extent of lead contamination of tap water in Chicago is disheartening — it’s not something we should be seeing in 2024,” lead author Benjamin Huynh, assistant professor of environmental health and engineering at the Johns Hopkins Bloomberg School of Public Health, said in a news release.

The study suggested that residential blocks with predominantly Black and Hispanic populations were less likely to be tested for lead, but also disproportionately exposed to contaminated water.

Gina Ramirez, Midwest regional lead of environmental health for the Natural Resources Defense Council, said she grew up in Chicago drinking bottled water, but now uses filtered water for her own family, because of a generational awareness of “not trusting my tap” to be safe.

The study “confirmed my worst fears that children living in vulnerable populations in the city are the most impacted,” she said. “All children deserve to grow up in a healthy city, and to learn that something inside their home is impacting so many kids health and development is a huge wake-up call.”

Researchers used artificial intelligence to extrapolate on 38,385 tap water tests collected from January 2016 to September 2023, provided by the Chicago Department of Water Management.

High levels of lead exposure can cause severe brain and central nervous system damage, leading to intellectual disabilities, behavioral disorders, coma, convulsions and death, according to the World Health Organization.

Even at lower levels, the effects of lead consumption in children may be decreased intelligence, behavioral difficulties and learning problems, the WHO says, along with various physical effects. It warns that there is there is “no known safe blood lead concentration” and that negative neurological and behavioral effects of lead consumption are believed to be irreversible.

Behavioral difficulties can include anxiety, depression and aggression, the National Institutes of Health says.

Children affected by the lead-contaminated water crisis in Flint, Mich., nearly a decade ago, suffered significant and lasting academic setbacks, according to a separate study released earlier this month.

The Environmental Protection Agency in November proposed regulation that would require all water utilities in the United States to replace their lead pipes, most within 10 years, in an undertaking that it said could cost $45 billion. The proposal is open for public comment before it is finalized, which the EPA expects by mid-October.

Most housing infrastructure with lead was built before the material was banned in pipes in 1986, according to the JAMA Pediatrics study.

President Biden promised last year to remove “every single” lead pipe in the country. In the $1.2 trillion infrastructure bill he signed into law in 2021, $15 billion was earmarked for replacing lead pipes.

More than 9.2 million households connect to water through lead pipes and lead service lines, disproportionately affecting low-income communities and people of color, according to the Biden administration. About 400,000 of those are in Chicago, the most of any U.S. city.

The city of Chicago has several programs for replacing lead pipes, including free replacement for low-income homeowners and for some licensed day cares. In November, it borrowed more than $336 million from the EPA to replace about 30,000 lead pipes.