Long-Term Exposure to Low-Level Ambient Benzene and Mortality in a National English Cohort.

BACKGROUND: Benzene affects human health through environmental exposure in addition to occupational contact. However, few studies have examined the associations between long-term exposure to low-level ambient benzene and mortality risks in non-occupational settings. METHODS: This prospective cohort study consists of 393,042 participants without stroke, myocardial infarction, or cancer at baseline from the UK Biobank. Annual average concentrations of benzene for each year during follow-up were measured using air dispersion models. The main outcomes were all-cause mortality as well as mortality from specific causes. Cox proportional hazards models with time-varying exposure measurements were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for mortality risks. Restricted cubic spline models were used to estimate the exposure-response relationships. RESULTS: With each interquartile range increase in the average annual concentrations of benzene, the adjusted HRs and 95% CIs of mortality risk from all-cause, cardiovascular disease, cancer, and respiratory disease were 1.26 (1.24 to 1.27), 1.24 (1.21 to 1.28), 1.27 (1.25 to 1.29), and 1.25 (1.20 to 1.30), respectively. The monotonically increasing exposure-response curves showed no threshold and plateau within the observed concentration range. Furthermore, the effect of benzene exposure on mortality persisted across different subgroups and was somewhat stronger in younger and white people (P for interaction <0.05). CONCLUSIONS: Long-term exposure to low-level ambient benzene significantly increases mortality risk in the general population. Ambient benzene represents a potential threat to public health, and further investigations are needed to support timely pollution regulation and health protection.