Agency for Toxic Substances and Disease Registry
Case Studies in Environmental Medicine (CSEM) 

Lead Toxicity
What is Lead?

Learning Objectives

Upon completion of this section, you will be able to

• explain what lead is.

Definition

Lead is a soft, blue-gray metal. Lead occurs naturally, but much of its presence in the environment stems from its historic use in paint and gasoline and from ongoing or historic mining and commercial operations.

Forms of Lead

Lead exists in both organic and inorganic forms.

Inorganic lead

The lead found in old paint, soil, and various products described below is inorganic lead. Leaded gasoline exhaust contributed to ambient inorganic lead contamination. For this reason, the focus of this document is on inorganic lead.

Organic Lead

Leaded gasoline contained organic lead before it was burned; however, since the elimination of lead from gasoline in the U.S. starting in 1976, exposure to organic lead is generally limited to an occupational context. However, organic lead can be more toxic than inorganic lead because the body more readily absorbs it. Potential exposures to organic lead should be taken very seriously.

Properties

Lead is a very soft, dense, ductile metal. Lead is very stable and resistant to corrosion, although acidic water may leach out of pipes, fittings, and solder. It does not conduct electricity. Lead is an effective shield against radiation.

Because of these properties, and because it is relatively easy to mine and work with, lead has been used for many purposes for thousands of years. Ancient Romans used lead for plumbing, among other uses. In modern times, lead was added to paint and gasoline to improve their performance but was eliminated in the 1970’s due to health concerns. Current uses of lead are discussed further in the next section.

Accumulation is the result of anthropogenic use, which has concentrated lead throughout the environment. Because lead is spread so widely throughout the environment, it can be found in everyone’s body today. The levels found today in most people are orders of magnitude greater than that of ancient times (Flegal 1995). These levels are within an order of magnitude of levels that have resulted in adverse health effects (Budd et al. 1998).

Key Points

• Lead is a naturally occurring metal.
• Lead is still used widely in commercial products.
• Lead is very stable and accumulates in the environment.
• Most lead encountered in the environment today is inorganic.
• The body absorbs organic lead (as was used in leaded gasoline and is used in occupational settings) faster than inorganic lead.

Progress Check