Course Content Page 5

History of Blood Lead Levels (BLL)

Prior to 1970, the blood lead level of concern was ≥ 60 µg/dl. The Surgeon General of the United States reduced the level of concern to ≥ 40 µg/dl in 1970. The CDC further reduced that number to ≥ 30 µg/dl in 1978, to ≥ 25 µg/dl in 1985, and to the current level of ≥ 10 µg/dl in 1991. The current level of concern is ≥ 10 µg/dl. Levels greater than 9 µg/dl are considered elevated (5).

National blood lead concentrations have dropped over the years. The average blood lead concentration in the United States was 16 µg/dl around 1980. More current estimates from the CDC's National Health and Nutrition Examination Surveys (NHANES) II and III (phase 1) place average blood lead concentrations at 2.8 µg/dl (3,4).

Key initiatives that have helped reduce lead exposure include the elimination of tetraethyl lead from the manufacture of gasoline and the creation of the Lead-Based Paint Poisoning Prevention Act of 1971. The poisoning prevention act created lead screening and lead poisoning treatment programs and prohibited use of lead-based paint for interior household painting.

Despite progress in lowering blood lead levels however, poisoning continues. Data from NHANES from 1991--1994 and 1999 showed that elevated blood lead levels remain common and concentrated at a local level among low-income children, urban children, and children living in older housing ( 1,2 ). The CDC's Childhood Blood Lead Surveillance (CBLS) program indicated that, among 19 states, county-specific proportions of children with elevated blood lead levels ranged from 0.5% to 27.3%. This wide variation indicates that concentrated proportions of elevated blood lead levels exist in specific populations or geographic areas.

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