The Role of Immigrant Enclaves and Ambient Air Pollution Exposure in the Immigrant Birthweight Paradox

Abstract

BACKGROUND AND AIM: Foreign-born Black and Latina women have higher birthweight infants that their US-born counterparts, despite generally worse socioeconomic status and prenatal care access, i.e. immigrant birthweight paradox (IBP). Residence in immigrant enclaves and associated socio-cultural and economic benefits may be drivers of IBP. Yet, enclaves are known to have higher air pollution, a risk factor for lower birthweight. We investigated IBP accounting for both residential immigrant composition and air pollution exposure. METHODS: In the Boston-based Children’s HealthWatch cohort of non-smoking women-child dyads (n=2,116), we obtained birthweight-for-gestational age z-scores (BWGAZ) for US-born births from 2006-2015. Using maternal address, we estimated trimester-specific PM2.5 concentrations, proximity to major roadways, and immigrant orientation level based on census-tract percentages of foreign-born, non-citizen, and linguistically-isolated households (proxy for immigrant enclave). We fit multivariable linear regressions of BWGAZ by maternal nativity and sequentially adjusted for immigrant orientation and ambient air pollution sources. We also examined effect modification of IBP by immigrant orientation. RESULTS:Fifty-one percent of women were foreign-born. Immigrant orientation was negatively correlated with PM2.5 concentrations and proximity to major roads. Overall, children of foreign-born women had 0.19 (95% CI: 0.10, 0.28) higher mean BWGAZ than those of US-born mothers, demonstrating IBP in our cohort. BWGAZ did not significantly change after adjustment for immigrant orientation and air pollution sources. However, we found an additive effect of immigrant orientation on maternal nativity (p-interaction: ≤0.01), with IBP observed only in moderate (0.27, 95% CI: 0.09, 0.46) and high (0.29, 95% CI: 0.15, 0.44) immigrant-oriented tracts. CONCLUSIONS:Foreign-born women in higher immigrant-oriented areas had higher BWGAZ, supporting the role of immigrant enclaves on IBP. Prenatal air pollution exposure did not impact associations observed in this study. Future research should consider the role of immigrant enclaves and their spatial correlation with potential protective resources and environmental risk factors. KEYWORDS: Air pollution, Particulate matter, Birth outcomes, Environmental disparities, Exposures, Environmental epidemiology