Associations between Residential Proximity to Oil and Gas Drilling and Term Birth Weight and Small-for-Gestational-Age Infants in Texas: A Difference-in-Differences Analysis

Abstract

<div class="section"> <a class="named-anchor" id="d111170e197"> <!-- named anchor --> </a> <h5 class="section-title" id="d111170e198">Background:</h5> <p id="d111170e200">Oil and natural gas extraction may produce environmental pollution at levels that affect reproductive health of nearby populations. Available studies have primarily focused on unconventional gas drilling and have not accounted for local population changes that can coincide with drilling activity. </p> </div><div class="section"> <a class="named-anchor" id="d111170e202"> <!-- named anchor --> </a> <h5 class="section-title" id="d111170e203">Objective:</h5> <p id="d111170e205">Our study sought to examine associations between residential proximity to oil and gas drilling and adverse term birth outcomes using a difference-in-differences study design. </p> </div><div class="section"> <a class="named-anchor" id="d111170e207"> <!-- named anchor --> </a> <h5 class="section-title" id="d111170e208">Methods:</h5> <p id="d111170e210">We created a retrospective population-based term birth cohort in Texas between 1996 and 2009 composed of mother–infant dyads ( <span class="inline-formula"> <math id="i1" overflow="scroll"> <mrow> <mi>n</mi> <mo>=</mo> <mn>2,598,025</mn> </mrow> </math> </span>) living <span class="inline-formula"> <math id="i2" overflow="scroll"> <mrow> <mo>&lt;</mo> <mn>10</mn> <mspace width="0.3em"/> <mi mathvariant="normal">km</mi> </mrow> </math> </span> from an oil or gas site. We implemented a difference-in-differences approach to estimate associations between drilling activities and infant health: term birth weight and term small for gestational age (SGA). Using linear and logistic regression, we modeled interactions between births before (unexposed) or during (exposed) drilling activity and residential proximity near (0–1, 1–2, or <span class="inline-formula"> <math id="i3" overflow="scroll"> <mrow> <mn>2</mn> <mo>–</mo> <mn>3</mn> <mspace width="0.3em"/> <mi mathvariant="normal">km</mi> </mrow> </math> </span>) or far ( <span class="inline-formula"> <math id="i4" overflow="scroll"> <mrow> <mn>3</mn> <mo>–</mo> <mn>10</mn> <mspace width="0.3em"/> <mi mathvariant="normal">km</mi> </mrow> </math> </span>) from an active or future drilling site, adjusting for individual- and neighborhood-level characteristics. </p> </div><div class="section"> <a class="named-anchor" id="d111170e259"> <!-- named anchor --> </a> <h5 class="section-title" id="d111170e260">Results:</h5> <p id="d111170e262">The adjusted mean difference in term birth weight for mothers living 0–1 vs. <span class="inline-formula"> <math id="i5" overflow="scroll"> <mrow> <mn>3</mn> <mo>–</mo> <mn>10</mn> <mspace width="0.3em"/> <mi mathvariant="normal">km</mi> </mrow> </math> </span> from a current or future drilling site was <span class="inline-formula"> <math id="i6" overflow="scroll"> <mrow> <mo>–</mo> <mn>7.3</mn> <mspace width="0.3em"/> <mi mathvariant="normal">g</mi> </mrow> </math> </span> [95% confidence interval (CI): <span class="inline-formula"> <math id="i7" overflow="scroll"> <mrow> <mo>–</mo> <mn>11.6</mn> </mrow> </math> </span>, <span class="inline-formula"> <math id="i8" overflow="scroll"> <mrow> <mo>–</mo> <mn>3.0</mn> </mrow> </math> </span>] for births during active vs. future drilling. The corresponding adjusted odds ratio for SGA was 1.02 (95% CI: 0.98, 1.06). Negative associations with term birth weight were observed for the 1–2 and <span class="inline-formula"> <math id="i9" overflow="scroll"> <mrow> <mn>2</mn> <mo>–</mo> <mn>3</mn> <mspace width="0.3em"/> <mi mathvariant="normal">km</mi> </mrow> </math> </span> near groups, and no consistent differences were identified by type of drilling activity. Larger, though imprecise, adverse associations were found for infants born to Hispanic women, women with the lowest educational attainment, and women living in cities. </p> </div><div class="section"> <a class="named-anchor" id="d111170e317"> <!-- named anchor --> </a> <h5 class="section-title" id="d111170e318">Conclusions:</h5> <p id="d111170e320">Residing near oil and gas drilling sites during pregnancy was associated with a small reduction in term birth weight but not SGA, with some evidence of environmental injustices. Additional work is needed to investigate specific drilling-related exposures that might explain these associations. <a data-untrusted="" href="https://doi.org/10.1289/EHP7678" id="d111170e322" target="xrefwindow">https://doi.org/10.1289/EHP7678</a> </p> </div>