Health effects of low level occupational exposure to lead: the trail, British Columbia study

Blood lead (PbB) was measured in a sample of 245 lead smelter employees and their wives in Trail, B.C. and 144 controls in Nelson, B.C. Smelter workers were divided into three groups according to lead exposure: (1) directly-exposed, (2) indirectly-exposed, and (3) office workers. The average PbB values found (41, 33, and 16 micrograms/dl, respectively) reflected exposure level. In the highest exposure group, male smokers had significantly higher PbB concentrations than nonsmokers (44 vs. 37 micrograms/dl). For exposed males, average number of "days off work ill" increased with increasing PbB range and significant correlations were found between PbB values and five biologically plausible health symptoms. None of those symptoms planted to detect response bias correlated. Because of a 4-month strike, PbB values were measured in a sub-sample from each exposure group before and 1, 2, and 4 months after smelter operation resumed. Exposed workers' PbB levels stabilized after 1 month's operation.