Lead-based paint was used in more than 38 million homes until it was banned for residential use in 1978. For those renting, buying or renovating a pre-1978 home, receiving a copy of the EPA's Lead Pamphlet is federal law, and duly warns against things like letting your children chew on the windowsills. Lead has been shown to affect children's brains and developing nervous systems, causing reduced IQ, learning disabilities, and behavioral problems, and is also harmful to adults. Lead in dust, which is often invisible, is the most common way people are exposed to lead.