Lead Poisoning
Michael Weitzman MD1
Deborah Glotzer MD2
1 Pediatrician-in-Chief, Rochester General Hospital, and Professor and Chief, Division of General Pediatrics, the University of Rochester School of Medicine and Dentistry, Rochester, NY
2 Assistant Professor of Pediatrics, Boston University School of Medicine and Boston City Hospital
The Changing Definition of Lead Poisoning
The understanding of childhood lead poisoning as a disease entity and the levels defined to indicate toxicity have been revised continually over the past 20 years as additional evidence has accured that demonstrates adverse health outcomes associated with levels of lead exposure previously thought to represent normal and innocuous values. Prior to 1970, significant lead poisoning was defined by blood levels greater than 60 µg/dL, levels that often are associated with clinically apparent signs and symptoms, such as vomiting, abdominal pain, irritability, and other overt behavioral changes, and that could result in seizures, coma, or death. Beginning in the early 1970s, researchers began to identify metabolic changes associated with elevated lead levels; other data also emerged suggesting that there are subtle, but serious and permanent neuropsychologic sequelae of blood lead elevations not associated with clinically recognizable symptoms. In 1971 the threshold for blood lead levels considered to represent undue lead absorption was reduced to 40 µg/dL. This was subsequently reduced to 30 µg/dL in 1975 and to 25 µg/dL in 1985, although the Centers for Disease Control's (CDC) 1985 definition of undue lead absorption was tempered by the statement that this "should not be interpreted as implying that a safe level of blood lead has been established."
