The Health Effects Of Lead Poisoning Have Been Previously Extensively Reviewed By The Federal Public

Agency for Toxic Substances and Disease Registry (ATSDR), Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH)1,2,3. There are thousands of scientific articles on the adverse health effects of lead in either children or adults. This chapter is a synopsis of the cardinal adverse health effects of lead in adults.

Lead is a bluish-gray metal used since ancient times because of its useful properties, such as low melting point, pliability, and resistance to corrosion. The ancient Romans and Greeks first discovered its toxic effects. Hippocrates (370 B.C.) attributed a severe case of colic in a worker who extracted metals to lead exposure, and Pliny the Elder (A.D. 23–79) wrote that workers painting ships with native ceruse (white lead) wore loose bags over their faces to avoid breathing noxious dust4. Lead is ubiquitous in older American homes and lead exposures in the workplace are common because of the widespread use, during the past century, of lead compounds in paints, gasoline, and industry.

Human lead exposure occurs when dust and fumes are inhaled and when lead is ingested via lead-contaminated hands, food, water, cigarettes, and clothing. Lead entering the respiratory and digestive systems is released to the blood and distributed throughout the body. More than 90 percent of total body burden of lead is accumulated in the bones, where it is stored for decades. Lead in bones may be released into the blood and re-exposes organ systems long after the original environmental exposure. This process can also expose the fetus to lead in pregnant women.

There are several biological indices of lead exposure. Lead concentrations in blood, urine, teeth, and hair can be used as biological indicators of lead exposure. Recent advances in the measurement of skeletal bone lead levels more accurately measure cumulative lead exposure and the total body burden of lead. At present, however, the best available method for monitoring biological exposure to lead is measurement of the blood lead level (BLL). The severity of symptoms associated with lead exposure generally increases as the BLL increases (see Table 1.1). No such relationship between symptoms and the other indices of lead exposure have been as well established.

A recent national survey found that the geometric mean BLL for the United States adult population (ages 20 to 74 yrs) declined significantly between 1976 and 1991, from 13.1 to 3.0 micrograms per deciliter (µg/dL)5. This decline was largely the result of stricter federal regulations and changes in regulated industries which reduced workplace exposures and the lead content of gasoline, paint, drinking water, and soldered food containers. To protect workers from lead poisoning, the Occupational Safety and Health Administration (OSHA) promulgated a lead standard for general industry in 1978 and an interim lead standard for the construction industry in 1993. More than 90 percent of adults now have a BLL <10 µg/dL, and more than 98 percent have a BLL < 15 µg/dL.

Although much progress has been made in reducing lead exposures, exposures in the workplace continue to be a significant public health problem. Even with the federal regulations, thousands of adult elevated BLLs 25 µg/dL are reported each year to NIOSH by states participating in a NIOSH surveillance program (see Chapter 2 for a more complete discussion). Elimination of worker BLLs greater than or equal to 25 µg/dL by the year 2000 is a health goal of the United States6.

The toxic nature of lead is well documented. The most important aspects of lead toxicity are its effects on the central nervous system, which may be irreversible; however, lead affects all organs and functions of the body to varying degrees. The frequency and severity of symptoms among exposed workers depend upon the level of exposure. A summary of the lowest-observed-effect levels for key lead-induced health effects in adults is presented in Table 1.1.

The remainder of this chapter summarizes the NIOSH evaluation of the scientific literature regarding health effects of high- and low-level lead exposures and occupational exposure limits. In preparing this section, NIOSH consulted with the National Institute of Environmental Health Sciences.