Objectives Although the most common cause of death in infants, little is known about the aetiology of congenital anomalies. Recent studies have increasingly focused on environmental exposures, including benzene. While benzene is known to affect the central nervous system, the effects on the developing fetus are unclear.
Methods We conducted a retrospective cohort study to evaluate the association between ambient benzene exposure and the prevalence of congenital anomalies among 628 121 singleton births in Oklahoma from 1997 to 2009. We obtained benzene from the Environmental Protection Agency’s 2005 National-Scale Air Toxics Assessment for the census tract of the birth residence. We used modified Poisson regression with robust SEs to calculate prevalence proportion ratios (PPRs) and 95% CIs between quartiles of benzene exposure and critical congenital heart defects (CCHDs), neural tube defects (NTDs) and oral clefts adjusted for maternal education and tobacco use.
Results Median benzene exposure concentration in Oklahoma was 0.57 µg/m3. We observed no association between benzene exposure and oral clefts, CCHDs or NTDs. When specific anomalies were examined, we observed an increased prevalence of cleft lip among those exposed to the second quartile of benzene compared with the first (PPR 1.50, 95% CI 1.05 to 2.13), though no association with higher levels of exposure.
Conclusions Our findings do not provide support for an increased prevalence of anomalies in areas more highly exposed to benzene. Future studies would benefit from pooling data from multiple states to increase statistical power and precision in studies of air pollutants and specific anomalies.
- congenital anomalies
- air pollution
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Contributors AEJ was primarily responsible for designing the study, analysing the data and writing the manuscript. HDD programmed and contributed to data analysis, interpretation and review of the manuscript. JEC contributed to the study design and data access and provided critical review of the manuscript. JAS contributed to the statistical analysis and critical review of the manuscript. JDP contributed to the design and analysis of the study and critical review of the manuscript.
Funding Research reported in this publication was supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number U5GM104938 and an award from the National Institute on Minority Health and Health Disparities (R25MD011564) of the National Institutes of Health.
Disclaimer The content is solely the responsibility of the authors and does not necessarily reflect the official views of the NIH.
Competing interests None declared.
Patient consent Not required.
Ethics approval University of Oklahoma Health Sciences Center, Oklahoma State Department of Health.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement We are unable to share the Oklahoma births or congenital anomalies data due to state laws. However, interested investigators may request these data from the Oklahoma State Department of Health. The benzene data from the Environmental Protection Agency are publicly available online (https://www.epa.gov/national-air-toxics-assessment).
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