First-year changes in blood lead and zinc protoporphyrin levels within two groups of occupational lead workers.
Quarterly changes in blood lead (PbB) and zinc protoporphyrin (ZPP) levels experienced by 30 male lead-acid storage battery workers and 24 auto assembly workers during their initial year of occupational lead exposure are described. The greatest absolute and percentage increases above baseline PbB levels occurred during the first 3 months of continuous exposure when battery and assembly workers' average PbB levels increased by 99% and 134%, respectively. Peak average PbB levels were reached during the second quarter of exposure for battery workers (27.3 micrograms/dL) and during the third quarter for assembly workers (34.3 micrograms/dL). Mean ZPP levels increased steadily through the first 3 quarters of exposure for both groups of workers before declining slightly during the final 3 months. Third-quarter average ZPP levels were 46.6 micrograms/dL for battery workers and 59.4 micrograms/dL for assembly workers. In general, for the assembly workers, the slopes of quarterly dose (PbB)-effect (loge ZPP) regressions increased with increasing exposure duration (up to 0.044 by the third quarter of exposure) and were significant (p less than 0.0001). Similar calculations for the battery workers were not statistically significant (p greater than 0.05) and showed no exposure-related trends. Probit-based dose (PbB)-response (ZPP level greater than two standard deviations above the baseline ZPP) analyses of the assembly worker data resulted in a 30.0 micrograms/dL ED50 estimate (PbB concentration at which 50% of a similarly exposed population would be expected to develop an "elevated" ZPP level).(ABSTRACT TRUNCATED AT 250 WORDS)