Associations between ambient exposure to styrene, benzene, toluene, ethylbenzene, and xylenes and hospitalizations in the US Gulf region

BACKGROUND: Styrene, benzene, toluene, ethylbenzene, and xylenes (SBTEX) are hazardous air pollutants studied primarily in occupational settings, where high exposures are linked to adverse health outcomes and are subject to strict regulation. In contrast, the health impacts of ambient SBTEX exposure, which occurs at lower concentrations, remain poorly characterized, largely because comprehensive exposure estimates are limited. METHODS: The study population comprised Medicare beneficiaries aged 65 years and older in the US Gulf region during 2011-2016. Outcomes were hospitalizations for cardiovascular (n = 601,631) and respiratory (n = 385,162) diseases. Ambient SBTEX exposures were derived from validated prediction models with high spatial (4 × 4 km) and temporal (daily) resolution. A time-stratified case-crossover design with conditional logistic regression was applied to estimate associations between daily ambient SBTEX concentrations and hospitalization risk. FINDINGS: We observed significant associations between ambient concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX) and cardiovascular and respiratory hospitalizations, but not for styrene. An interquartile range increase in daily mean benzene concentration (0.087 ppb) was associated with a 0.38% (95% CI: 0.08%, 0.68%) increase in cardiovascular hospitalizations at lag 0 and a 1.00% (95% CI: 0.60%, 1.41%) increase over lags 0-7. The corresponding increases in respiratory hospitalizations were 0.88% (95% CI: 0.50%, 1.25%) at lag 0 and 2.74% (95% CI: 2.29%, 3.19%) over lags 0-7. Similar associations were observed for toluene, ethylbenzene, and xylenes. An interquartile range increase in total BTEX (0.297 ppb) was associated with increases of 0.85% (95% CI: 0.44%, 1.27%) and 1.87% (95% CI: 1.41%, 2.32%) in cardiovascular and respiratory hospitalizations over lags 0-7, respectively. INTERPRETATION: Even at low ambient concentrations, BTEX exposures may increase the risk of cardiovascular and respiratory hospitalizations among older adults. These findings support greater public health attention to ambient BTEX, extending beyond traditional concerns focused on occupational and industrial settings.