Associations of Prenatal BTEX Exposure with Preterm Birth: A Nationwide Birth Cohort Study in 337 Chinese Cities

Long-term exposure to benzene, toluene, ethylbenzene, and xylene (BTEX) has been linked to preterm birth (PTB), yet evidence from China remains limited. This study included 4,321,599 live singleton births from the National Free Preconception Health Examination Project between 2010 and 2015. Prenatal BTEX exposure was estimated using a chemistry-climate model. Multivariate linear regression and logistic regression models were applied to examine associations of BTEX exposure with gestational age and PTB risk, respectively. For the entire pregnancy, each interquartile range (IQR, 11.6 μg/m3) increase in BTEX exposure was associated with a reduction of 0.138 (95% confidence interval [CI]: 0.133-0.142) weeks in gestational age and a 23% (odds ratio [OR]: 1.23, 95% CI: 1.22-1.24) increase in PTB risk. Among individual components, IQR increases in benzene, toluene, and xylenes concentrations were associated with 21% (95% CI: 20-22%), 25% (95% CI: 24-26%), and 20% (95% CI: 19-21%) higher odds of PTB, respectively. The strongest associations were observed for exposures during the third trimester for both BTEX (OR = 1.27, 95% CI: 1.26-1.28) and individual components (benzene: OR = 1.25, 95% CI: 1.24-1.26; toluene: OR = 1.29, 95% CI: 1.28-1.30; and xylenes: OR = 1.25, 95% CI: 1.24-1.26). Subgroup analyses indicated that the associations were more pronounced among male fetuses, mothers who were overweight or obese, engaged in farming, or had lower educational attainment. Prenatal BTEX exposure was significantly associated with an elevated risk of PTB, emphasizing the potential adverse effects of BTEX pollution on maternal and infant health.