Humans have been mining and using this heavy metal for thousands of years, poisoning themselves in the process due to accumulation and exposure. The dangers have also long been known. Reducing the hazard requires both individual actions and public policy regulations. Blood lead levels once considered safe are now considered hazardous, with no known threshold.
Today almost everyone is exposed to environmental lead. Exposure to lead and lead chemicals can occur through inhalation, ingestion or occasionally dermal contact. Lead mining and lead smelting are common in many countries, where children and adults can receive substantial lead exposure from sources uncommon today in the U.S. Most countries will have phased out use of leaded gasoline by 2007. Lead exposure in the general population (including children) occurs primarily through ingestion, although inhalation also contributes to lead body burden and may be the major contributor for workers in lead-related occupations. Inhalation is the second major pathway of exposure. Almost all inhaled lead is absorbed into the body, whereas from 20% to 70% of ingested lead is absorbed (with children generally absorbing a higher percentage than adults do). Dermal exposure plays a role for exposure to organic lead among workers, but is not considered a significant pathway for the general population, except in areas where leaded gasoline is used. Organic lead from gasoline additives may be absorbed directly through the skin.
Lead-contaminated household dust is the major source of lead exposure to children in the U.S. In 1978 there were 13.5 million children in the United States with elevated blood lead levels (i.e., 10µg/dl). By 2002, that number had dropped to 310,000 kids. The U.S. incurs $43.4 billion annually in the costs of all pediatric environmental disease, with childhood lead poisoning alone accounting for the vast majority of it.
Although children are at greater risk from lead exposure, adult exposures can also result in harmful health effects. Most adult exposures are occupational and occur in lead-related industries such as lead smelting, refining, and manufacturing industries. One frequent source of lead exposure to adults is home renovation that involves scraping, remodeling, or otherwise disturbing lead-based paint. Adults can also be exposed during certain hobbies and activities where lead is used. Workers may inhale lead dust and lead oxide fumes, as well as eat, drink, and smoke in or near contaminated areas, thereby increasing their probability of lead ingestion. Between 0.5 and 1.5 million US workers are exposed to lead in the workplace (ATSDR, 1999). Other than the developmental effects unique to young children, the health effects experienced by adults from adult exposures are similar to those experienced by children, although the thresholds are generally higher.