A longitudinal study of the effects of long-term exposure to lead among lead battery factory workers in Taiwan (1989-1999).

The objective of this study was to assess the relationship between blood-lead levels (BLL), hematological, liver and renal indicators among workers in a lead battery factory in Taiwan over a 10-year period. Blood samples were taken periodically from 30 workers and BLL, HGB (hemoglobin), RBC (red blood cells), WBC (white blood cells) and HCT (hematocrit) were measured. Levels of GPT (alanine aminotransferase) and Crea (creatinine) in the blood were assessed to indicate liver and renal function, respectively. The results showed that there was a general decrease in BLL over the 10-year period (except for 1993). There was a similar trend for HCT, RBC and Crea. There was no significant trend for the other health indicators. Four generalized estimating equation (GEE) models [correlation model (A), threshold correlation model (B), instant change model (C) and lag change model (D)] were set up to demonstrate the causal relationship between BLL and the other health indicators. Models A and C showed that BLL correlated positively with RBC, but negatively with Crea. Model B showed that BLL correlated positively with GPT. There were no significant correlations of BLL with the other indicators. Models C and D, (GEE with logit link function to analyze the association between changes BLL and the other health indicators) showed that when BLL increased, RBC and HCT increased, both longitudinally and cross-sectionally. The authors conclude that long-term exposure to lead stimulates production of RBC and HCT, but the effect on liver and renal function was unclear.