Scrutiny of lead in drinking water at schools has increased over the years, but there are no federal rules for testing day care centers, and only seven states require providers to sample for it.

Lead has been traced to developmental delays, speech and language problems, and nervous system damage in children, health and environmental officials say.

Children are primarily exposed to lead through lead-based paint and dust, but infants younger than 6 months old who are formula-fed are equally exposed...