When Selena Wiley signed the lease for an older rental home in South Bend, Ind., she asked the property manager about lead paint and was assured the house was safe.But in November 2018 — almost two years after moving in with her partner and three children — Ms. Wiley noticed that their 2-year-old’s appetite had vanished and his constant chattering had stopped.A doctor soon discovered that the boy, Joevonne, known as J.J., had lead poisoning. The level was so high that he immediately began a 19-day treatment to help rid his body of the toxin, which can cause irreversible damage to a child’s brain and nervous system. A health inspector soon found lead paint and dust throughout the family’s rental home.As J.J. faces an uncertain future, no one has been held responsible so far — the firm that owns the home protected its assets in a tangle of limited liability companies, and the property insurer excluded lead from its coverage. These practices are now the norm across the United States, The New York Times has found, part of a decades-long campaign by the real estate and insurance industries to shield themselves from liability in lead-poisoning cases. The effort has helped allow what is often considered a problem of the past to remain a silent epidemic today.Although lead poisoning has decreased substantially since the late 1970s as a result of regulatory actions and public health initiatives, about 500,000 children under 6 have elevated blood lead levels in the United States and are at risk of harm. The issue has only intensified in the era of Covid-19: Rental inspections lagged, exposure increased as people spent more time at home and testing of children fell by 50 percent at times in 2020.“It’s a slow-moving catastrophe that people have just gotten used to,” said Sean M. Ryan, a state senator in western New York, where high rates of lead poisoning persist.Children in the U.S. With Elevated Blood Lead LevelsNo level of exposure to lead is considered safe. Even low levels have been shown to affect a child’s intelligence, learning ability and behavior. The U.S. Centers for Disease Control and Prevention recently lowered the threshold used to identify children with the highest lead levels.