Maternal exposure to traffic-related air pollution and birth defects in Massachusetts
Introduction
Birth defects are prevalent in 3% of US live births (Parker et al., 2010), with cardiac, orofacial, and neural tube defects among the most common defects observed (Yoon et al., 2001). Exposure to air pollution during pregnancy has been suggested to increase risk of birth defects (Dadvand et al., 2011, Dolk et al., 2010, Gilboa et al., 2005, Padula et al., 2013, Schembari et al., 2014, Vrijheid et al., 2011) in some studies. The time between conception and birth is a sensitive and critical time for fetal development due to rapid cell proliferation and rapid development of various organ systems, thus understanding the influence of ambient exposures on fetal development may elucidate the mechanisms behind abnormal fetal development. Studies of fetal exposure to traffic-related air pollution including particulate matter with a diameter of 2.5 µm or less (PM2.5) have shown associations with adverse birth outcomes such as intrauterine growth retardation and preterm births (Brauer et al., 2008, Liu et al., 2007), but investigations of the association of PM2.5 on birth defect risk have been inconclusive (Agay-Shay et al., 2013, Hansen et al., 2009, Kim et al., 2007, Stingone et al., 2014, Chen et al., 2014, Marshall et al., 2010, Padula et al., 2013, DJ et al., 2013).
Exposure estimates for earlier studies were constrained to individuals living near air monitoring stations without daily assessments, limiting both spatial and temporal resolution of the exposure assessment resulting in exposure misclassification (Ritz and Wilhelm, 2008, Ghosh et al., 2012). Earlier studies were unable to adjust for important confounders such as individual-level socioeconomic status (SES) and may have been limited by case ascertainment over a short study period (Ritz and Wilhelm, 2008, Ghosh et al., 2012). Only one other study (Padula et al., 2013) to our knowledge has accounted for road density and residential distance to roadways, local measures of traffic-related air pollution, in addition to PM2.5 estimates when assessing risk of birth defects and exposure to ambient air pollution. Satellite-based PM2.5 prediction models can provide additional spatial and temporal information for exposure assessments. Models have evolved from using one single predictor (Wang and Christopher, 2003) to multiple predictors (Liu et al., 2005, Liu et al., 2007, Liu et al., 2009) and from one-stage models (Hu et al., 2013) to multi-stage non-linear models (Hu et al., 2014a, Hu et al., 2014b, Hu et al., 2014c, Kloog et al., 2011).
The objective of this study is to examine the relationship between cardiac, orofacial, and neural tube defects and traffic-related air pollution using satellite-based PM2.5 exposure estimates and eight years of birth defects data for Massachusetts. To further assess the influence of PM2.5 on birth defect risk, our study includes an analysis of geographic patterns of birth defects across Massachusetts.
Section snippets
Study population
We obtained all live and still births from the Massachusetts state birth registry with an estimated conception date from January 1, 2001 through December 31, 2008. All births in the Massachusetts Birth Defects Registry having cardiac, orofacial, and neural tube defects (International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes 740.0-743.0, 745.0-748.0 and 749.0-749.3) were identified as cases. The Massachusetts Birth Defects Monitoring Program conducts
Results
We obtained records for 2729 cardiac, 726 orofacial, 255 neural tube defect cases, and 7816 controls geocoded, non-syndromic births from the 611,854 births in Massachusetts conceived from January 1, 2001 to December 31, 2008. The percentage of cases with mothers 30–34 years old ranged from 27–31%, depending on the defect. Between 61–72% of mothers were of non-Hispanic White race/ethnicity, and between 56–74% of mothers reported education levels greater than high school (Table 1). Eight percent
Discussion
We examined the spatial relationship between PM2.5 and other traffic-related measures using anatomical groupings of cardiac, neural tube and orofacial birth defects. There is evidence to support the hypothesis that exposure to PM2.5 and traffic-related air pollution increases risk of patent foramen ovale and patent ductus arteriosus, as these defects displayed a positive but non-significant association with PM2.5. Patent foramen ovale displayed positive significant associations with both
Conclusions
In summary, we found evidence to suggest that PM2.5 exposure during pregnancy may be associated with risk of patent foramen ovale, patent ductus arteriosus, and perimembranous ventricular septal defects. Our findings also support a possible relationship between ostium secundum atrial septal defects and insufficiency of the aortic valve with local traffic-related air pollutants. Our spatial analyses show that there were geographic regions with increased risk of ostium secundum atrial septal
Conflict of interest
None declared.
Acknowledgments/grant support
This work was supported by grant number R01ES019897 and P42ES007381 from the National Institute of Environmental Health (NIEHS). Its contents are solely the responsibility of the authors and do not necessarily represent the views of NIH. The work of Y.L. and X. H. was partially supported by NASA Applied Sciences Program (grant no. NNX11AI53G).
The Institutional Review Boards of the University of California at Irvine and the MA Department of Public Health approved this research.
References (50)
- et al.
Ambient air pollution and congenital heart disease: a register-based study
Environ. Res. J.
(2011) - et al.
Air pollution and congenital heart defects
Environ. Res.
(2013) - et al.
Using aerosol optical thickness to predict ground-level PM2.5 concentrations in the St. Louis area: a comparison between MISR and MODIS
Remote. Sens. Env.
(2007) - et al.
Estimating ground-level PM2.5 concentrations in the southeastern U.S. using geographically weighted regression
Environ. Res.
(2013) - et al.
Estimating ground-level PM2.5 concentrations in the southeastern United States using MAIAC AOD retrievals and a two-stage model
Remote. Sens. Environ.
(2014) - et al.
Assessing temporally and spatially resolved PM2.5 exposures for epidemiological studies using satellite aerosol optical depth measurements
Atmos. Environ.
(2011) - et al.
Updated national birth prevalence estimates for selected birth defects in the United States, 2004-2006
Birth Defects Res. A Clin. Mol. Teratol.
(2010) - et al.
The National Birth Defects Prevention Study, Public Health Report (116)
(2001) - et al.
Ambient air pollution and risk of congenital anomalies in England, 1991–1999
Occup. Environ. Med.
(2010) - et al.
Relation between ambient air quality and selected birth defects, seven county study, Texas, 1997–2000
Am. J. Epidemiol.
(2005)