Three-year follow-up of serial nerve conduction among lead-exposed workers

Abstract

Objectives. The purpose of this study was to investigate the serial nerve conduction parameters of a group of lead-exposed workers and determine their correlation with the serial blood lead results over a three-year period. A 'nonresponse' level (defined as no significant changes in the nerve conduction in response to changes in the blood lead level of each exposed worker observed over the period of study) was also determined for blood lead in respect to the peripheral nerves. Methods. Seventy-two male workers from a lead battery manufacturing factory were followed at six-month intervals for three years. At each follow-up, the blood lead level was determined and nerve conduction tests (ulnar and median nerves) were conducted. A group of 82 unexposed subjects served as referents. Results. Significant differences were observed for some of the mean values of the median nerve conduction parameters between the exposed and reference groups. The 28 exposed workers who completed the follow-up were divided into the following two blood lead categories: < 40 μg·100 ml-1 (< 1.93 μmol·l-1) and ≤ 40 μg·100 ml-1 (≤ 1.93 μmol·l-1). In the latter, the median motor conduction velocity, median distal latency, median amplitude, ulnar motor conduction velocity, and ulnar amplitude were significantly correlated (adjusted for age and within-subject variation) with the blood lead levels, but not so in the former. Conclusions According to the three-year serial results, the 'nonresponse' level for blood lead with respect to the peripheral nerves would be < 40 μg·100 ml-1 (< 1.93 μmol·l-1).