Nerve conduction velocity studies on lead workers

ABSTRACT

Neuroconduction measurements were carried out amongst lead workers and referent groups, the exposed group being surveyed twice with a one year interval between examinations . No dose-effect or dose-response relationships was found between the motor and sensory conduction velocities in the nerves examined (median and ulnar nerves of the dominant arm) and the concentrations of lead in blood. There was an association between the delay in motor distal latency in the median nerve and the incrasing of the levels of lead in blood, however, with a dose-repone which was assessed by the "ratio risk" method and found to be statistically significant. Although age was found to be an important confounding factor when analysing those relationships, legth of exposuere did not show any association with neuroconduction changes. Taking into account the data from neuroconduction studies on lead worker goups available in the literature, and considering that the group examined in this study was heavily exposed to lead, the neurophysiological response found (prolonged motor distal latency in the median nerve, with no slowing in conduction velocities) was slight. However the same pattern is shown in the biochemical response (low concentrations of ALA-U and small changes in Hb). A possible explanation for these findings is an interaction between lead and zinc, resulting in low levels of delta aminolevulinic acid in plasma, which might explain the weak neurophysiological response found