Lead-based paint is the biggest source of lead exposure in the U.S. today. Most buildings built before 1960 have lead-based paint, and buildings built as late as 1978 may also have lead-based paint. Lead-based paint that is in good condition (i.e. not peeling or chipping) generally does not pose a threat and should be left alone. However, lead-based paint that is chipping, peeling, or otherwise damaged or deteriorated is considered a “lead hazard” and can be a major health risk.
Lead dust can also be very dangerous. Leaded dust is created, or released, when surfaces with lead-based paint deteriorate, when they rub against other surfaces (such as window sashes on frequently used windows) or when they are impacted (such as stair risers). US EPA and HUD have developed action levels which define when a leaded dust hazard is present. These action levels are 40 micrograms of lead per square foot (μg/ft2) on floors, both exterior and interior, 250 μg /ft2 on window sills or interior horizontal surfaces, and 400 μg /ft2 on window wells.
Lead in soil is another common cause of lead exposure. Soil generally becomes contaminated with lead due to lead-based paint chipping off of the outsides of homes and buildings, or due to car exhaust from leaded gasoline (which is no longer used). Soil which is near roads, older homes, buildings, and industrial facilities is most likely to be contaminated with lead. Most soil must contain at least 1000 parts per million (ppm) of lead before it is considered a lead hazard. However, bare soil in children’s play areas is considered a lead hazard if it contains 400 ppm of lead or more.