Mortality and cancer incidence in a large cohort of lead-exposed workers.

Abstract

Inorganic lead is a common occupational exposure and a probable carcinogen (International Agency for Research on Cancer, group 2A). Here, we analyse mortality and cancer incidence in a large cohort of US workers with measured blood lead levels. We updated the mortality follow-up for a cohort of 58 000 male lead-exposed workers and followed a subset of 36 000 for cancer incidence, both through 2021. The highest recorded blood lead was used as the exposure metric in internal exposure-response analyses via Cox regression. Time at risk began at the first blood lead test. The median birth year was 1959 and the average year of the first blood test was 1998. The mean highest blood lead was 26 µg/dL. There were 8832 deaths. The mortality results showed strong positive associations between blood lead and lung cancer, pancreatic cancer, heart disease, chronic obstructive pulmonary disease, and chronic renal disease. There were 6125 incident cancers. The lung cancer incidence showed a marked positive trend with higher lead levels; the liver cancer incidence also had a significant positive trend. Thyroid and prostate cancer showed marked negative trends. High blood lead levels were associated with several causes of mortality and cancer incidence, most markedly lung cancer. While lung cancer trends might be related to smoking, there is no a priori reason why workers with higher blood lead would have smoked more and, in a subset of 200 workers with smoking data, there was no such evidence. The lung cancer rate ratios in the order of 2.0-2.5 are also very unlikely to be explained by smoking differences.