Sarah Frostenson and Sarah Kliff:

Neighborhoods where kids face the highest risk of lead poisoning exist all across America.

The trouble is that exposure risk is surprisingly difficult estimate, due to a variety of state-by-state differences in reporting standards. So we worked with epidemiologists in Washington state to estimate risk levels in every geographic area in America.

“As a parent, I found it very alarming,” says Holly Davies, who works in Washington’s Department of Ecology on lead exposure reduction. “My son was born in West Virginia, and there it was standard practice that at one year they get screened [for lead poisoning risk]. But here it wasn’t a standard thing; I was the one who had to bring it up.”