The Long-Term Effects of Exposure to Low Doses of Lead in Childhood

Abstract

To determine whether the effects of low-level lead exposure persist, we reexamined 132 of 270 young adults who had initially been studied as primary school-children in 1975 through 1978. In the earlier study, neurobehavioral functioning was found to be inversely related to dentin lead levels. As compared with those we restudied, the other 138 subjects had had somewhat higher lead levels on earlier analysis, as well as significantly lower IQ scores and poorer teachers' ratings of classroom behavior. When the 132 subjects were reexamined in 1988, impairment in neurobehavioral function was still found to be related to the lead content of teeth shed at the ages of six and seven. The young people with dentin lead levels greater than 20 ppm had a markedly higher risk of dropping out of high school (adjusted odds ratio, 7.4; 95 percent confidence interval, 1.4 to 40.7) and of having a reading disability (odds ratio, 5.8; 95 percent confidence interval, 1.7 to 19.7) as compared with those with dentin lead levels less than 10 ppm. Higher lead levels in childhood were also significantly associated with lower class standing in high school, increased absenteeism, lower vocabulary and grammatical-reasoning scores, poorer hand-eye coordination, longer reaction times, and slower finger tapping. No significant associations were found with the results of 10 other tests of neurobehavioral functioning. Lead levels were inversely related to self-reports of minor delinquent activity. We conclude that exposure to lead in childhood is associated with deficits in central nervous system functioning that persist into young adulthood.

Stable lead isotopic analyses of historic and contemporary lead contamination of San Francisco Bay estuary

“…Toxicological . and clinical studies have established no lower thresh old for deleterious human health effects from lead Ž Needleman et al, 1979;McMichael et al, 1988;Needleman et al, 1990;Bellinger et al, 1991;. Bellinger et al, 1994 .…”

Influence of the common human delta-aminolevulinate dehydratase polymorphism on lead body burden.

“…Of particular importance, exposure to low levels of lead in utero or in early childhood may lead to irreversible central nervous system damage (1)(2)(3)(4)(5)(6)(7)(8).…”

“…The homooctameric zinc metalloenzyme, 6-aminolevulinate dehydratase (porphobilinogen synthase, ALAD, EC 4.2.1.24), is the second enzyme in the heme biosynthetic pathway. ALAD is expressed in all tissues, but occurs at elevated levels in liver, which has the added burden of cytochrome P450 synthesis, and in the highest levels in erythrocytes and their precursors.…”

Socioeconomic background modulates cognition–achievement relationships in reading

“…3-0.7 (White, 1982), and evidence has suggested that SES is predictive both of decoding single words and non-words, as well as reading comprehension (Bowey, 1995;Hecht et al, 2000;Raz & Bryant, 1990). Although SES is most commonly indexed using education, occupation, and income (Ensminger & Fothergill, 2003), many other factors vary systematically with SES (Barnett, 1998; BrooksGunn, Klebanov, & Duncan, 1996;Hawley & Disney, 1992;Jackson, Brooks-Gunn, Huang, & Glassman, 2000;Klein, Hack, & Breslau, 1989;Korenman, Miller, & Sjaastad, 1995;Leventhal & Brooks-Gunn, 2003b;McCormick, 1989;Needleman, Schell, Bellinger, Leviton, & Allred, 1990;Ramey & Ramey, 1998) and are likely to play a role in creating and sustaining the SES gap in cognitive performance and achievement (Bornstein & Bradley, 2003). For this reason the association between SES and reading ability is likely to be multifactorial.…”

“…One child suffered a head injury involving loss of consciousness for several hours. Because physical and mental health factors could account for SES differences in cognitive performance (Hawley & Disney, 1992;Klein et al, 1989;McCormick, 1989;Needleman et al, 1990), analyses will be presented below both including and excluding children with medical or psychiatric histories. …”