Hydraulic fracturing, commonly called fracking, is a method of extracting oil and natural gas from rock formations deep underground by pumping high-pressure fluid into the rock to crack it open. It has transformed the U.S. into the world’s largest oil and gas producer, but it carries a range of environmental costs, from water contamination and heavy water use to methane emissions, earthquakes, and health risks for nearby communities.
How Fracking Works
The process starts with drilling a well vertically, sometimes thousands of feet below the surface, until it reaches a layer of shale or other tight rock that holds trapped oil or gas. In most modern operations, the drill then turns horizontally, extending thousands of feet sideways through the target formation. This horizontal reach is what makes fracking so productive: a single well can access far more rock than a traditional vertical well.
Once drilling is complete, operators pump massive volumes of fluid down the wellbore at pressures high enough to fracture the rock. That fluid is mostly water mixed with sand (or ceramic pellets) and a cocktail of chemical additives. The sand grains wedge into the newly opened cracks and hold them open, creating pathways for oil or gas to flow back up to the surface. What comes back up with the gas is a mixture called flowback, which contains the injected chemicals along with substances picked up from deep underground, including salts, heavy metals, hydrocarbons, and naturally occurring radioactive materials like radium.
Water Use and Contamination
Fracking is water-intensive. A single horizontal gas well used a median of about 5.1 million gallons of water in 2014, up from less than 177,000 gallons per well in 2000. Horizontal oil wells used around 4 million gallons each. Vertical and directional wells require far less, typically under 687,000 gallons, but they now make up a shrinking share of new drilling. In arid regions like West Texas and eastern New Mexico, that demand competes directly with agriculture and municipal water supplies.
The contamination risk comes through several pathways. Fracking chemicals and methane can migrate through natural cracks in the rock into underground drinking water sources. If the steel and cement casing that lines a well is poorly installed or degrades over time, it can leak gas or fluids into surrounding aquifers. On the surface, chemical spills from trucks, tanks, or storage pits can reach streams and soil. And flowback water, if not properly contained, carries a concentrated mix of salts, metals, and radioactive materials that can pollute surface water and groundwater alike.
The produced water that returns from deep formations is essentially brine laced with contaminants. Radium isotopes are the most common radioactive elements found in it. Managing this waste is one of the industry’s biggest challenges: most of it gets injected into deep disposal wells, which creates its own set of problems.
Methane Emissions and Climate
Methane is the primary component of natural gas, and it traps roughly 80 times more heat than carbon dioxide over a 20-year period. Every stage of the fracking supply chain leaks it: wellheads, pipelines, compressor stations, and storage facilities. The federal government has long estimated that these leaks average about 1% of total gas production nationwide, but aerial and satellite surveys tell a different story.
A Stanford-led study found that actual methane leakage across major U.S. oil and gas regions averaged about 3% of total production, with some areas far worse. The New Mexico portion of the Permian Basin was the highest emitter, losing nearly 10% of its total methane output straight to the atmosphere. Midstream infrastructure, the pipelines and processing plants between the wellhead and the end user, accounted for roughly half of all leaked emissions, a larger share than earlier estimates had suggested.
These leakage rates matter because they erode the climate advantage natural gas is supposed to have over coal. At leak rates above roughly 3%, the near-term climate benefit of switching from coal to gas for electricity generation largely disappears.
In December 2023, the EPA finalized a rule targeting methane from oil and gas operations, including, for the first time, existing facilities nationwide. The rule requires operators to monitor for leaks using technologies like optical gas imaging and to repair them on set timelines. It also limits routine flaring of gas at new wells.
Earthquakes From Wastewater Disposal
Fracking itself occasionally triggers small tremors, but the bigger seismic risk comes from what happens to the wastewater afterward. Billions of gallons of produced water get injected into deep disposal wells each year, and when that fluid reaches faults underground, it reduces the friction holding the fault in place. The result is earthquakes in places that historically had almost none.
Oklahoma went from averaging fewer than two magnitude-3+ earthquakes per year before 2009 to becoming one of the most seismically active places in the continental U.S. Four earthquakes of magnitude 5 or greater struck the state, three of them in 2016 alone. The largest documented injection-induced earthquake was a magnitude 5.8 near Pawnee, Oklahoma, in September 2016. A magnitude 5.3 quake hit the Raton Basin in Colorado in 2011, also linked to wastewater injection. The USGS has identified 17 areas in the central and eastern U.S. with elevated earthquake rates tied to fluid injection.
After Oklahoma imposed volume limits on disposal wells in the most active zones, seismicity dropped significantly. But the relationship between injection volumes, geology, and fault activation is complex, and some induced earthquakes have occurred months or even years after injection rates changed.
Land and Habitat Disruption
Each well pad requires roughly three acres of cleared land, with an equivalent amount for access roads, pipeline corridors, and supporting infrastructure. That adds up quickly in heavily drilled regions. In parts of Pennsylvania, West Virginia, and North Dakota, thousands of well pads have fragmented forests, grasslands, and agricultural land.
The footprint extends beyond the pad itself. Roads increase erosion and sediment runoff into streams. Pipeline corridors cut through wildlife habitat, creating barriers for species that avoid open ground. Noise, light, and truck traffic during the drilling and completion phase, which can last weeks to months, displace wildlife and disrupt breeding. For migratory birds and species that depend on large, unbroken tracts of habitat, cumulative fragmentation from dense drilling is a serious concern.
Health Effects for Nearby Communities
People living close to fracking operations face exposure to air pollutants including volatile organic compounds, particulate matter, and ground-level ozone formed when methane and other emissions react with sunlight. Diesel exhaust from the heavy truck traffic associated with well development adds another layer of exposure.
A growing body of research links proximity to fracking sites with adverse health outcomes, particularly for pregnant women and children. A 2019 systematic review found significant associations between living near unconventional gas development and preterm birth, low birth weight, and babies born small for gestational age. In one study published in JAMA Pediatrics, people living near 100 or more wells within about six miles had a 64% higher risk of spontaneous preterm birth and a 65% higher risk of having a smaller-than-expected baby compared to those living farther away.
Respiratory symptoms, including increased asthma attacks and other breathing problems, have also been reported more frequently in communities near active drilling. The challenge with all of this research is separating the effects of air pollution, water contamination, noise, and stress, since they often overlap in the same communities. But the pattern across multiple studies and multiple regions points consistently toward measurable health risks for people living closest to operations.