The lead paint indicator is the percentage of occupied housing units built before 1960, calculated from the U.S. Census Bureau's ACS 5-year summary estimates on age of housing stock. EJScreen uses age of housing stock as a surrogate for potential lead exposure as regulations banning lead-based residential paint in 1978 led to the reduction and finally an end to the use of such paint in housing. The percentage of older housing units is a proxy for potential exposure to lead paint and lead-containing dust that accumulates indoors, in homes, or in other buildings where lead paint was used. EJScreen uses housing units built before 1960.