Lead occurs naturally in the environment at very low levels. Relatively high level sources of lead occurred in car exhaust prior to 1980 (the lead from exhaust fumes was ultimately deposited onto the ground) as well as in older paints (modern paint does not contain lead). Other sources exist such as pewter pitchers and dinnerware, birdshot, and fishing weights.

In the past, toothpaste tubes were made of lead and condensed milk cans were soldered with lead. This has been corrected. Lead can also be found in drinking water from homes whose pipes were soldered with lead solder. New building codes require lead-free solder.

Infants and children most at risk are those living in pre-1960's housing where paint often contained lead. Small children often ingest paint chips or dust from lead based paint. Soil in cities with high traffic density may contain high levels of lead from car exhaust.