Cross-sectional neurotoxicology study of lead-exposed cohort

Abstract

Although the toxic effects of lead have been known for centuries, lead intoxication is still widespread in the United States. Without baseline tests of neuropsychological, neurobehavioral and neurophysiological testing it may be difficult to detect subtle changes in neurological function after lead exposure. This may be further confounded by partial chelation treatment and exposure to neurotoxic mixtures or inability to quantitate alcohol consumption. We undertook a cross-sectional study to address these problems in 24 exposed and 29 control subjects in a plant that manufactured electrical components using fritted leaded glass to coat capacitors and transistors. Potentially exposed workers had blood lead levels ranging between 3 micrograms/dL to 135 micrograms/dL. Industrial hygiene monitoring revealed the plant's air lead levels ranged from 61 micrograms/m3 to 1,700 micrograms/m3 in excess of OSHA permissible exposure limits of 40 micrograms/m3/10 hr day. Using a specially designed battery of neurophysiological, neurobehavioral and neuropsychological screening tests, we demonstrated a significant difference from controls in measures of psychomotor speed, motor strength and verbal memory. Although limited by the cross-sectional design, these findings support the hypothesis that the battery of neurophysiological, neuropsychological and neurobehavioral tests can detect a significant inter-group differences between lead-exposed and control subjects.

Occupational Lead Exposure

“…Bias resulting from the effects of variation in instructions and inter-or intra experimenter differences are increasingly being elimi nated with the introduction of automated testing. In ear lier studies, however, this is likely to have been a signifi cant problem and in fact only one of the studies discussed here [3] employed computer-assisted test administration. While methods of assessing tester reliability both within and between testers exist [22], these were rarely, if ever, reported and one presumes, therefore, not carried out.…”

“…This is extremely difficult to achieve in practice as those with experience in this field will appreciate. The fact that it was achieved in only four of these studies [3,6,12,13] reflects this.…”

“…Current Evidence terms of assessing cumulative effects, since it is represen tative of only recent exposure and not the total body bur den of lead, it is nevertheless superior to air measure ments as an indicator of an individual's exposure. The blood lead levels of the workers included in these studies were wide-ranging with some as high as 135 pg/dl [3], However, the majority were well below 70 pg/dl. It is interesting to note that without exception the cross-sec tional studies found significant differences between the performance of the exposed and control groups on one or more neurobehavioural tests.…”

“…In the majority of the twelve studies examined, either selection procedures were not reported [4][5][6][7][8][9] or it was stated that only volunteers were used [10,11]. Three stud ies report acceptable selection procedures [3,12,13] and one reports random selection of exposed subjects but employed volunteers as controls [14], Volunteers might have reasons for taking part in research which may bias results. For example, individuals may choose to partici pate because they have health problems which they would like investigated.…”

Characterizing Golden Eagle Risk to Lead and Anticoagulant Rodenticide Exposure: A Review

“…Occupational exposure to lead has often been associated with signs of neurotoxicity. The literature contains numerous case reports and small cohort studies that describe a higher incidence of these symptoms, including malaise, forgetfulness, irritability, lethargy, headache, fatigue, impotence, decreased libido, dizziness, weakness, and paresthesia at PbBs that range from approximately 40 to 120 μg/dL following acute-, intermediate-, and chronic-duration occupational exposure (Awad El Karim et al 1986;Baker et al 1979Baker et al , 1983Campara et al 1984;Haenninen et al 1979; Holness and Nethercott 1988;Lucchini et al 2000;Marino et al 1989;Matte et al 1989;Pagliuca et al 1990;Pasternak et al 1989;Pollock and Ibels 1986;Rosenman et al 2003;Schneitzer et al 1990;Zimmerman-Tanselia et al 1983). …”