Maternal proximity to Central Appalachia surface mining and birth outcomes

Abstract

Background: Maternal residency in Central Appalachia counties with coal production has been previously associated with increased rates of low birth weight (LBW). To refine the relationship between surface mining and birth outcomes, this study employs finer spatiotemporal estimates of exposure. Methods: We developed characterizations of annual surface mining boundaries in Central Appalachia between 1986 and 2015 using Landsat data. Maternal address on birth records was geocoded and assigned amount of surface mining within a 5 km radius of residence (street-level). Births were also assigned the amount of surface mining within residential ZIP code tabulation area (ZCTA). Associations between exposure to active mining during gestation year and birth weight, LBW, preterm birth (PTB), and term low birth weight (tLBW) were determined, adjusting for outcome rates before active mining and available covariates. Results: The percent of land actively mined within a 5 km buffer of residence (or ZCTA) was negatively associated with birth weight (5 km: β = –14.07 g; 95% confidence interval [CI] = –19.35, –8.79, P = 1.79 × 10–7; ZCTA: β = –9.93 g; 95% CI = –12.54, –7.33, P = 7.94 × 10–14). We also found positive associations between PTB and active mining within 5 km (odds ratio [OR] = 1.06; 95% CI = 1.03, 1.09, P = 1.43 × 10–4) and within ZCTA (OR = 1.04; 95% CI = 1.03, 1.06, P = 9.21 × 10–8). Positive relationships were also found between amount of active mining within 5 km or ZIP code of residence and LBW and tLBW outcomes. Conclusions: Maternal residency near active surface mining during gestation may increase risk of PTB and LBW.

Identifying exposure pathways mediating adverse birth outcomes near active surface mines in Central Appalachia

“…We obtained birth records for four states across Central Appalachia, provided by departments of health in Kentucky (KY), Tennessee (TN), Virginia (VA), and West Virginia (WV) (Figure 1 ). This dataset is described in detail in Buttling et al 22 ; briefly, a total of 409,394 birth records were obtained from departments of health with street addresses of reported maternal addresses. Records were removed due to missingness in street addresses with many records reporting only mailing addresses (such as a rural route or P.O.…”

“…Our previous analysis shows differences in maternal characteristics of births from the original and final dataset are minimal and an additional analysis using a zip-code level exposure variable that allowed the inclusion of most of the original records resulted in similar effect estimates. 22 The exposure variable of interest within this dataset was the proportion of land designated as “active surface mining” within a 5-km radius of the maternal address during the majority gestation year. Pre-mining areas were defined as areas that were classified as actively mined in future years of the study period.…”

“…We employed mediation analyses to explore the potential exposure pathways that could explain associations between living in close proximity to active surface mining activities and increased odds of PTB and LBW described in Buttling et al 22 , accounting for premining differences and additional individual-level covariates available on birth records. Mediation analyses are helpful in exploring the underlying mechanisms underpinning a known relationship between an exposure and outcome.…”

“… 19 , 20 Within the Central Appalachia region, Ahern et al 21 have documented an independent risk of LBW among women living within an area with coal mining activities in West Virginia. More recently, Buttling et al 22 suggested an increased risk of LBW and PTB among women living within 5 km of an active surface mine.…”

“…More specifically, we aim to explore airshed and watershed exposure pathways as potential mediators of the association observed between proximity to active surface mining activities and adverse birth outcomes. 22 We undertake a mediation analysis within a logistic regression modeling framework to examine the odds of PTB, LBW, and term LBW outcomes as predicted by maternal proximity to surface mining activities during gestation from 1990 to 2015, overlaying surface mine airshed and watershed boundaries. To undertake these analyses, we use geolocated birth records spanning four states in the Central Appalachia region, representing nearly 200,000 births over 2.5 decades.…”