What is Lead?
Lead is one of the first metals to have been used by humans. Its use dates back as far as 6500 BC
Archaeological discoveries of ancient lead pipes have been made in Egypt that date back to the time of the Pharaohs. The Roman Empire also used lead pipes and fixtures throughout its water systems that included thousands of miles of aqueducts. These and many other early cultures have also been found to use lead in the glazes on their pottery. It is believed that poising through the food and water may have had an effect in the decline of these civilizations.
Lead is a naturally occurring element present in the earth's formation. It is usually associated with other minerals, notably zinc, silver and copper. Trace amounts of other elements, including gold, are sometimes found with lead ore. The most common lead ore is galena, or lead sulfide. The ore is mined, concentrated and then smelted in a blast furnace with limestone and coal. It is refined to remove and recover other metals.
Recycled lead is a significant market since lead is easily melted and molded. Lead actually is the most recycled of all industrial metals in the world. In the United States, 80 percent of lead used is in automotive-type batteries, and more than 95 percent of these batteries are recycled.
Lead is important to many industries because of its natural properties:
- Mass
- Malleability
- Low Melting Point
- Corrosion Resistance
- Electrical Properties
- Long Life
Today we are seeing lead become essential to the production of many highly technical products such as fiber optics, microcircuits, computer monitors, TV's, Medical shielding products, etc.
Lead Health Risks
Ingestion, inhalation, and absorption at abnormally high level of lead can be harmful. Fortunately, lead exposure to both workers and the general public has been greatly reduced over the last several decades. Current uses of lead are controlled and usually pose no significant environment or health risks. However, according to the Center for Disease Control (CDC), pockets of high exposure still exist in older urban communities where there is deteriorating housing. This creates environmental health risks for both residents and the individuals working in those areas.
Child Exposure
Despite popular belief that exposure to lead among young children is a growing problem in the United States, the blood-lead level among children has dropped from a national average of over 30 micrograms of lead per deciliter (ug/dl) in the 1930's, to average levels in 1994 of about 2.7 ug/dl, according to the U.S. Center for Disease Control. The 1994 findings from the ongoing National Health and Nutrition Examination Survey (NHANES III) indicate that less than half of 1% of the children in the United States have blood lead levels (20 ug/dl) sufficient to warrant medical intervention. Broad averages, of course, can conceal important distinctions among sub-groups of the population.
In brief, the current CDC action levels are:
- Less than 10 ug/dl -- No action;
- 10-14ug/dl -- No interventions of individual children; community-wide primary prevention activities when many children in a community are in this range;
- 15-19 ug/dl - Individual case management, including nutritional and educational interventions and more frequent screening. If the levels persist, environmental investigation, including a home inspection; and
- 20 ug/dl and above - Individual medical evaluation and intervention and the source of lead exposure located and removed.
Adult Exposure
The 1994 NHANES III findings indicated the adult blood lead levels average around 2.4 ug/dl. Since the majority of elevated adult exposures occur in the workplace, the Occupational Safety & Health Administration (OSHA) has created regulations for those environments. OSHA has set lead standards that establish 40 ug/100gr as the desired maximum blood lead level.