In a study conducted in California, we discovered that pregnant women residing near operational high-output oil and gas wells have a higher likelihood of bearing babies with low birth weight. This discovery contributes to a growing collection of research regarding the potential public health effects of oil and gas activities.
We examined the birth records of close to 3 million infants born to individuals living within 6.2 miles (10 kilometers) of at least one oil or gas well in regions such as Sacramento, San Joaquin Valley, South Central Coast, and South Coast of California—areas known for oil production—from 2006 to 2015. Our analysis indicated that in rural areas, expectant mothers who lived within 0.62 miles (1 kilometer) of the most productive wells were 40% more likely to have babies with low birth weight compared to those living further away from wells or only near inactive wells. We also discovered that rural women living near these top-producing wells had a 20% higher likelihood of having babies small for their gestational age, a sign of reduced fetal growth.
For full-term births, babies born to rural women within 0.62 miles of a well were, on average, 1.3 ounces (36 grams) lighter than their counterparts. Although this decrease in weight might seem insignificant at an individual clinical level, a downward shift of such magnitude at the population level can have important implications for overall neonatal and infant health. Additionally, in urban areas, we found that pregnant women living near high-production wells had a 4% increased risk of having a small-for-gestational-age baby.
These trends remained consistent even when accounting for known risk factors related to poor birth outcomes, including maternal age, level of education, access to prenatal care, race and ethnicity, neighborhood socioeconomic conditions, and other air pollution sources. Oil and gas production has been a significant American industry for over a hundred years, with the United States currently the largest petroleum producer globally. In recent decades, new extraction methods, such as hydraulic fracturing or “fracking,” have notably increased production in states like Pennsylvania, Colorado, and Texas.
Local potential impacts of oil and gas development encompass pollution of air, water, and soil, as well as excessive light and noise at night due to well pad construction, truck activity, drilling, pumping, gas flaring, and other procedures. Studies conducted in states like Pennsylvania, Colorado, Texas, and Oklahoma have shown that living near active oil and gas wells may increase the risk for pregnant women of having babies with low birth weight, premature births, and babies small for gestational age.
California’s distinct oil and gas infrastructure dates back to the early 1900s, and by 2017, the state was among the top five crude oil producers in the U.S., though production is declining. Oil and gas production in California takes place in both rural and urban settings, primarily using traditional drilling and enhancement techniques, with a lesser extent of hydraulic fracturing. A study from 2017 estimated that 2.1 million Californians lived within one mile of an active oil and gas well. However, no epidemiological studies had previously examined potential health risks in California. There may be certain factors not accounted for in our analysis that could increase the susceptibility of rural pregnant women to the adverse health effects of oil and gas development, such as chemical exposures related to maternal work, housing quality, or reliance on untreated groundwater for drinking.
In a similar vein, a 2019 study from Colorado noted rural and urban differences, with a heightened likelihood of congenital heart defects in babies born to women near high-production oil and gas wells in rural areas. Our findings contribute to the growing evidence linking proximity to active oil and gas wells with negative birth outcomes. Another recent study in California’s San Joaquin Valley highlighted increased risks of preterm spontaneous birth among women living nearer to producing oil and gas wells.
As the number of studies on oil and gas grows, it remains uncertain which elements of these operations potentially threaten human health. Multiple hazards related to intensive oil production, such as air toxins, water pollutants, noise, and intense light, could each impact health differently. A deeper understanding of these exposures and how they occur could guide regulation and assist in determining priorities for pollution monitoring, reducing emissions, and implementing exposure reduction strategies.
As Californians discuss whether the state should expand oil and gas production, including new drilling permits, findings from health studies like ours may inform current efforts to establish buffer areas between active wells and where people—especially the most vulnerable—live, attend school, and play. We believe future studies should better discern the specific health risks posed by oil and gas production. Importantly, we advocate for research and regulatory endeavors to fully engage with communities living near oil and gas production facilities, collaborating to identify and enforce effective strategies for reducing exposure that specifically protect vulnerable populations.