A prospective follow-up study on psychological effects in workers exposed to low levels of lead

A prospective follow-up study on new lead workers who began work at a storage battery factory was carried out between 1975 and 1981. Psychological performances (eg, intelligence, memory, visuomotor functions, vigilance, and personality) were assessed before the commencement of exposure and after one, two, and four years of work. Of an initial number of 89 workers, 24 were available for the one-year, 16 for the two-year, and 11 for the four-year reexamination. The time-weighted average blood lead values ranged between 0.68 and 2.17 mumol/l (14 and 45 micrograms/100 ml, respectively). A reference group, nonexposed workers in a cable manufacturing plant and an electrical power plant, was similarly followed. Initially the average psychological performances were similar among the lead workers and the referents. For some of the psychological tests learning effect, which was clearly evident among the referents during the follow-up, was almost absent among the lead workers. The lead worker's visual intelligence and visuomotor functions in particular were impaired significantly after the first two years of follow-up. When the lead workers were divided into two groups according to the median time-weighted average of the blood lead values (1.30 mumol/l), the Block Design and the Santa Ana coordination tests were those which best separated the subgroups. Although the impairment of the lead workers' performance was rather slight and the dispersion in the psychological changes was wide, it was evident that some higher nervous functions were affected by lead levels above about 1.45 mumol/l.