Evaluation of postural stability in workers exposed to lead at a secondarylead smelter

Postural sway testing was carried out on a group of 145 workers exposed to lead in a secondary lead smelter and 84 workers not exposed to lead in a hi nge manufacturing plant. All workers were measured for blood lead levels (B LL) and erythrocyte zinc protoporphyrin (ZPP) concentrations at the time of testing and both a total cumulative and a time-weighted average BLL value was constructed for the lead exposed workers. The lead exposed workers mean BLL at the time of testing was 38.9 mu g/dl and the non-exposed workers me an was 2.3 mu g/dl. ZPP levels averaged 55.2 mu g/dl for exposed workers an d 18.9 mu g/dl for non-exposed workers. Total cumulative BLL averaged 83476 mu g/dl days for the exposed workers, with a mean time-weighted average BL L of 35. 1 mu g/dl. Six tests of postural stability, four two leg conditions and two single leg conditions were administered to all subjects using a force platform to pro duce measurements of sway for comparison purposes. The two leg conditions a lso manipulated the visual and proprioceptive systems. A statistically sign ificant association was observed for sway measurements and the current BLL for all workers, but not with the current BLL of only the lead exposed work ers. No statistically significant associations were present with the cumula tive measures of long-term exposure. Of the six tests of sway, only the sin gle leg conditions showed significant exposure effects. The results suggest effects of lead exposure among those with average BLL near 40.0 mu g/dl, b ut only in the most challenging one leg conditions. (C)1999 Inter Press, In c.