Kamala Harris reiterated that she won’t ban fracking on Wednesday in an interview with KDKA-TV, the CBS affiliate in Pittsburgh, Pennsylvania. Though the US vice-president once backed a ban on the fuel extraction process, she said on Wednesday that she changed her mind since joining Joe Biden’s presidential campaign in 2020 and has since remained firm. The statement comes as she and Donald Trump compete for votes in Pennsylvania, a swing state with 20 seats in the electoral college and a major gas producer. The Trump campaign, meanwhile, has been running ads claiming that if elected, Harris would enshrine a ban on fracking, costing Pennsylvania over 300,000 jobs. Here’s an introduction to the gas and oil extraction process that has transformed the US fossil fuel industry. What is fracking? Hydraulic fracturing, better known as fracking, is a method of extracting fossil fuels. Producers drill into shale and other rocks deep underground, then pump in water, chemicals and sand to form cracks and release oil and gas. By providing access to once hard-to-reach oil, the technology unlocked oil and gas reserves across 20 US states including Texas and Pennsylvania. It is now the most commonly used fossil fuel extraction method in the United States. Since the fracking boom, US oil production has surged at a historic rate. No country in history has extracted as much oil and gas as the US has in each of the past six years, and gas has become the country’s most commonly used electricity source, eclipsing coal. Why is fracking so controversial? Fracking is controversial because of its environmental and health impacts. Scientists have long warned that the world must phase out fossil fuels to preserve a livable climate. The drilling technique can also contaminate drinking water. Many Americans’ introduction to these risks came from the 2010 documentary Gasland, which memorably showed a homeowner who was able to light on fire the water flowing out of his kitchen tap More than 17.6 million people live within a mile of a fracked well, researchers found in 2022, with those living in close proximity to wells commonly reporting health issues ranging from headaches and nosebleeds to low infant birth weights and endocrine disruption. Pennsylvania researchers have found that children living close to active wells or near many wells had a higher risk for developing lymphoma, a kind of cancer. The practice is also water-intensive, and has been linked to earthquakes. But it has become part of a larger culture war, with some rightwingers believing that calls to end fracking are anti-American calls from the so-called “woke left”. Is fracking actually bad for the climate? Fracking is used to produce fossil fuels, which account for the vast majority of all planet-heating pollution. A 2022 report found that planned US fracking projects could release 140bn metric tons of planet-heating gases, tipping the world toward climate disaster. But fracked gas has long been pitched by companies and even some environmentalists as a “bridge fuel”, or a temporary solution to transition from coal to renewable energy sources. When burned, gas emits about half of the greenhouse gas emissions of coal per unit of energy, and it can also have a smaller land footprint than coalmines. Some studies, however, suggest fracked gas may be even worse for the climate than coal throughout its life cycle from extraction to transport to usage. Importantly, fracking for gas can lead to leaks of methane – a greenhouse gas that warms the planet far faster than carbon dioxide – which research suggests are routinely underreported. The US is aiming to reduce emissions by at least 50% by 2030, but, under current plans supported by green policies in the Inflation Reduction Act, is on track to see only a drop between 32% and 43% by that time period, researchers have found. Why is fracking such an issue in the 2024 election? Trump has been a staunch supporter of the fossil fuel industry. On Tuesday, he reminded viewers that Harris once supported a ban on fracking– something he said would devastate the Pennsylvania and US economy. During her 2019 presidential campaign, Harris did back an end to fracking. But in July, her campaign said she was no longer in favor of such a policy, to the disappointment of green groups and some climate-concerned Americans. The prioritization of “energy independence” is often viewed as a point in favor of continued fossil fuel extraction including fracking. But oil and gas are part of a global market, and every US president in the past 75 years has continued to import foreign fossil fuels. And some argue that clean energy could play an important role in untethering US energy supply from volatile energy markets. In her Wednesday interview with KDKA, the Harris said Trump’s campaign ads were intentionally misleading. “I’m going to bring jobs back to rural communities. I’m going to make sure that we invest in those communities that have done the kind of work that you have in mind when you talk about Pittsburgh, when you talk about the greater aspect of Pennsylvania. And I’m going to keep doing that work,” she said. Pennsylvania, where polls show Harris and Trump are neck and neck in the polls, is the second-largest gas producer in the US – and also an important swing state in the presidential election. But Pennsylvanians have decidedly mixed opinions on fracking, with a 2020 survey finding that a slight majority of Pennsylvanians – 52% – actually oppose fracking, and a 2021 poll by the progressive thinktank Ohio River Valley Institute finding that less than a third of residents saying they want fracking in their state. Some Americans are concerned about a loss of fracking jobs, which have already been steadily declining, including in Pennsylvania. Research shows clean energy currently employs eight times more people in Pennsylvania than gas.