Mortality among employees of lead battery plants and lead-producing plants, 1947-1980.
Two cohorts of male lead workers, 4 519 battery plant workers and 2 300 lead production workers, all of whom had been employed for at least one year during the period 1 January 1946 through 31 December 1970, were observed for mortality during the 34 years from 1 January 1947 through 31 December 1980. Vital status as of the closing date was determined for 94.7% of the former group and 91.6% of the latter. There were 1 718 deaths in the first cohort and 621 in the second. Mortality from all causes combined was significantly greater than expected in each cohort, the standardized mortality ratio (SMR) being 107 and 113, respectively. Among the battery plant workers the greater than expected mortality rate resulted in large part from a significant number of excess deaths from malignant neoplasms (SMR 113), other hypertensive disease (mainly renal) (SMR 320), chronic nephritis (SMR 222), and a group of ill-defined conditions (SMR 355). Among the lead production workers the pattern was similar, with a significant number of excess deaths from other hypertensive disease (SMR 475), hypertensive heart disease (SMR 203), chronic nephritis (SMR 265), and ill-defined conditions (SMR 214). There was also a significant excess of deaths from external causes (SMR 143). The SMR for total malignancies was 113, but this value was not significantly elevated at the 5% level. In neither cohort were deaths from cerebrovascular disease in significant excess, the SMR being 93 and 132, respectively. A proportionate mortality analysis showed that the excess deaths from cerebrovascular disease and from hypertensive heart disease among smelter workers were in part due to the high proportion of nonwhites in the smelter populations. The stomach, liver, and lungs were the sites responsible for most excess cancer deaths in both cohorts, but the elevated SMR values were statistically significant only for gastric and lung cancers in battery plant workers. There were no excess deaths from malignancies of the kidney, brain, or lymphopoietic system in either cohort. It is impossible to relate the observed mortality to levels of lead exposure; because of meager quantitative information prior to 1960. It is known that past exposures had been very high. Ethnicity, diet, alcohol, and cigarette smoking could not be ruled out as possible confounding etiologic factors for the cancer deaths.