Electrophysiological study of subjects occupationally exposed to lead and with low levels of lead poisoning

The relationship between the length of exposure to lead, blood lead level (PbB) and peripheral nerve damage in a population occupationally exposed to low levels was evaluated. Sixty-two foundry workers were studied whose length of exposure ranged from 5 months to 10 yr; their mean PbB in the last 2 yr had not exceeded 50 μg/100 ml (2.4 μmol/l). The referents were 27 hospital employees, of comparable ages, not occupationally exposed to lead. The electrophysiological examination consisted of the determination of the motor conduction velocity (MCV) of the median and peroneal nerves, sensory conduction velocity (SCV) of the median and sural nerves, and the latency of the T and H reflexes. The mean MCV, SCV and the amplitude of the sensory action potential (SAP) of the median nerve were significantly lower in the group of exposed workers than in the reference group. When the exposed subjects were divided into three groups according to length of exposure, no difference was observed between the three groups. When they were divided into different groups according to the maximum PbB (max PbB) value, the observed differences with respect to the reference groups were already present in those with a max PbB of 70 μg/100 ml (>3.4 μmol/l). Within the group of subjects with a max PbB of 50-69 μg/100 ml (2.4-3.3 μmol/l), the differences with respect to the reference values were more evident for subjects with a short length of exposure (