Relations between lead exposure and peripheral neuromuscular functions of lead-exposed workers--results of tapping test.

In this study, four experiments using the tapping test were conducted to evaluate the possible subclinical effects of lead exposure on the neuromuscular systems of lead workers at some transfer printing factories in Japan. Decreases in the tapping ability appeared coincidentally with higher blood lead levels. The recovery of the tapping ability after 30 sec rest in the groups of 30-45 micrograms/dl and above 45 micrograms/dl PbB was worse than that in the group with less than 29 micrograms/dl PbB. The recovery of the decreased tapping ability after 60 sec rest was better even in the group with 30-45 micrograms/dl PbB. The tapping ability for 0-10 sec at the first tapping test was sustained after 30 or 60 sec rest in the group with the PbB below 29 micrograms/dl; however, the tapping ability at the second and third tapping test decreased in the two groups with the PbB level above 30 micrograms/dl. The decreased finger tapping speed may be functional evidence of low-grade motor neuropathy among the workers with higher levels of lead absorption.