“We fear the children who go missing are likely the children at higher risk,” said Dr. Courtney. Some states reported that the decline in lead screenings was particularly pronounced in children who received Medicaid, he added.

The consequences could be devastating for lead-poisoned children. While there is no way to reverse lead poisoning, nutritional supplements and education services can help reduce the damage. Children who miss their checkups may not receive these essential measures.

In addition, in many cases, increased levels of lead in the blood are required to trigger the removal or remediation of lead. “If you don’t test, you won’t find it,” said Dr. Morri Markowitz, director of the Lead Poisoning Treatment and Prevention Program at Montefiore Children’s Hospital, New York City. “If you don’t find it, don’t intervene and the child will still be exposed and may continue to ingest lead.” He added, “And then it can go on, and if you look it will get worse.”

Even as lead rates fell last spring, the amount of time children spent in their homes, where lead exposure is most likely, increased. The pandemic and the financial troubles it has brought about may also have caused some families and owners to postpone significant repair and maintenance work on buildings.

“I am very concerned that we may have more children who have been exposed when they have been in homes with peeling, peeling paint,” said Dr. Joneigh Khaldun, Michigan State’s chief medical officer and assistant general manager of health for the Michigan Department of Health and Human Services. “We just don’t even know.”

Widespread closures of buildings have created other risks. Although color is the leading cause of childhood lead poisoning, Lead pipes are also a threat. The longer the water stagnates in such pipes, the more lead seeps into them; Schools and daycare centers that closed last year could dangerously contaminate their water if they reopen.

“You can expect high levels of lead in some taps,” said Jennifer Hoponick Redmon, senior environmental health scientist at RTI International, a North Carolina-based nonprofit research organization. “In schools and day-care centers – and really in all closed places – water has to be flushed before people can use the water for drinking and cooking again.”