Styrene exposure and ischemic heart disease: A case-cohort study

Epidemiologic studies have consistently reported increased daily mortality and hospital admissions for ischemic heart disease related to daily changes in ambient particulate levels. One theory is that substances adhering to particulates might have a cardiovascular effect. Styrene has been found in very low doses in air and has chemical characteristics that would cause adherence to particles. Industrial studies have found an increase in cardiovascular disease among styrene-exposed workers. To explore a possible dose-response relation between styrene exposure and ischemic heart disease, the authors of this case-cohort study included 498 cases that died from ischemic heart disease and a 15% random sample (n = 997) of all male workers who were employed during 1943-1984 in two styrene-butadiene rubber-manufacturing plants in the United States. Proportional hazards models showed that recent styrene exposure was significantly associated with acute ischemic heart disease death among active workers. The relative hazard of death from acute ischemic heart disease for exposure during the most recent 2 years among active workers with 2 or more years of employment was 2.95 (95% confidence interval: 1.02, 8.57) at a time-weighted styrene concentration of 0.2-<0.3 ppm and 4.30 (95% confidence interval: 1.56, 11.84) at >= 0.3 ppm for the same exposure period, respectively.