ENVIRONMENTAL LEAD - A REVIEW

Lead has long been recognized as a toxic material and its chronic effects on humans and its immediate effect on the environment have been extensively studied. Initially, lead poisoning of workers was the chief concern, but in the last 3 decades studies have been carried out to identify the effects of long-term exposure to low levels of lead. Deposition to and accumulation in the environment have also been examined. Lead is derived from a number of urban point sources, but also comes in significant quantities from paint and motor car exhausts. This has ensured that lead is widely distributed in the urban scene, and it is persistent. Initially, elevated blood levels in children were usually considered to be due to ingestion of lead-based paints. More recently, lead-contaminated dust and soils have been recognized as potential sources. Any program that aims to determine environmental lead levels, or intends to identify potential sources of lead that may be absorbed by humans, must take account of residual levels in soil, water, air, and dust. Studies carried out by the authors in response to elevated blood lead levels being detected in children in Port Pirie, South Australia, sampled all of the above. Although Port Pirie was the site of lead smelting operations for nearly 100 years, it was accumulated lead in the city dust that was found to be a significant contributor to blood lead, not present-day point source emissions.