There’s an issue where the underlying science remains a political football, and scientists are regularly challenged and called out personally. Where energy needs and short-term economic growth are set against our children’s health and future. Where the consequences of bad, short-sighted decisions may be borne primarily by a small subset of under-served and undeserving persons. And where the very descriptive terms in the debate are radioactive, words spun as epithets.

We’re not talking here about global warming, and “deniers” versus “warmists.” We’re talking about the game-changing new set of unconventional oil and gas extraction technologies and techniques collectively known as hydraulic fracturing, or “fracking.”

Ask the most hardcore of pro-fracking boosters for their take, and they’ll describe the modern miracle of America’s new-found energy independence, a reality almost inconceivable just a decade ago. For them, the oil and gas boom around the U.S. has helped to reboot the economy at a time of great need. Prices at the pump have plummeted. Sure, they may acknowledge, there are a few safety issues to be worked out and techniques yet to be perfected, but just look at the big picture.

Fracking detractors in environmental and social justice circles, meanwhile, will conjure up the iconic image: Flammable water flowing from a home faucet. And with that come other haunting images: The double-crossed landowner hapless in the face of aggressive Big Energy. The ugly rigs rising up amid the tranquility of America’s farm, pasture, and suburban lands. The stench of unknown – even secret – chemicals, sickness, and looming illnesses, and death.

Refereeing these confrontations is no easy thing, and unlike the “settled science” of climate change and its causes, the science of fracking is far from settled. But a review of the research can help clarify some of the chief points of contention.

If there’s a single source plausibly seen as the fairest, most comprehensive, and cogent assessment, it might be the 2014 literature review published in Annual Reviews of Environment and Resources. It’s titled “The Environmental Costs and Benefits of Fracking,” authored by researchers affiliated with leading universities and research organizations who reviewed more than 160 studies.

Below are the arguments and synthesized evidence on some key issues, based on the available research literature and conversations with diverse experts.

Air quality, health, and the energy menu

ISSUE: The new supply of natural gas reachable by fracking is now changing the overall picture for U.S. electricity generation, with consequences for air quality.

PRO FRACKING: Increasing reliance on natural gas, rather than coal, is indisputably creating widespread public health benefits, as the burning of natural gas produces fewer harmful particles in the air. The major new supply of natural gas produced through fracking is displacing the burning of coal, which each year contributes to the early death of thousands of people. Coal made up about 50 percent of U.S. electricity generation in 2008, 37 percent by 2012; meanwhile, natural gas went from about 20 percent to about 30 percent during that same period. In particular, nitrogen oxide and sulfur dioxide emissions have been reduced dramatically. Fracking saves lives, and it saves them right now and not at some indiscernible date well into the future.

CON FRACKING: First, it is not the case that a new natural gas facility coming online always replaces a legacy coal-fired power plant. It may displace coal in West Virginia or North Carolina, but less so in Texas and across the West. So fracking is no sure bet for improving regional air quality. Second, air quality dynamics around fracking operations are not fully understood, and cumulative health impacts of fracking for nearby residents and workers remain largely unknown. Some of the available research evidence from places such as Utah and Colorado suggests there may be under-appreciated problems with air quality, particularly relating to ozone. Further, natural gas is not a purely clean and renewable source of energy, and so its benefits are only relative. It is not the answer to truly cleaning up our air, and in fact could give pause to a much-needed and well thought-out transition to wind, solar, geothermal, and other sources that produce fewer or no harmful airborne fine particulates.

U.S. net electricity generation by energy source

Greenhouse gas leaks, methane and fugitive emissions

ISSUE: The extraction process results in some greenhouse gas emissions leakage.

Fracking in Pennsylvania, Marcellus Shale.

PRO FRACKING: We know that, at the power plant level, natural gas produces only somewhere between 44 and 50 percent of the greenhouse gas emissions compared with burning of coal. This is known for certain; it’s basic chemistry. That is a gigantic benefit. Further, some research that claims methane is so harmful uses a 20-year time horizon; but over a 100-year time horizon – the way we generally measure global warming potential – methane is not nearly so harmful as claimed. Thus, methane’s impact is potent but relatively brief compared with impacts of increased carbon dioxide emissions. The number-one priority must be to reduce the reliance on coal, the biggest threat to the atmosphere right now. Fears about emissions leaks are overblown. Even if the true leakage rate were slightly more than EPA and some states estimate, it is not that dramatic. We are developing technology to reduce these leaks and further narrow the gap. Moreover, research-based modeling suggests that even if energy consumption increases overall, the United States still will reap greenhouse benefits as a result of fracking.

CON FRACKING: Research from Cornell has suggested that leaked methane – a powerful greenhouse gas – from wells essentially wipes out any greenhouse gas benefits of natural gas derived from fracking. And at other points in the life cycle, namely transmission and distribution, there are further ample leaks. Falling natural gas prices will only encourage more energy use, negating any “cleaner” benefits of gas. Finally, there is no question that the embrace of cheap natural gas will undercut incentives to invest in solar, wind, and other renewables. We are at a crucial juncture over the next few decades in terms of reducing the risk of “tipping points” and catastrophic melting of the glaciers. Natural gas is often seen as a “bridge,” but it is likely a bridge too far, beyond the point where scientists believe we can go in terms of greenhouse gas levels in the atmosphere.

Drinking water wars

ISSUE: Fracking may threaten human health by contaminating drinking water supplies.

PRO FRACKING: It is highly unlikely that well-run drilling operations, which involve extracting oil and gas from thousands of feet down in the ground, are creating cracks that allow chemicals to reach relatively shallow aquifers and surface water supplies. Drinking water and oil and gas deposits are at very different levels in the ground. To the extent that there are problems, we must make sure companies pay more attention to the surface operations and the top 500 to 1,000 feet of piping. But that’s not the fracking – that’s just a matter of making sure that the steel tubing, the casing, is not leaking and that the cement around it doesn’t have cracks. Certain geologies, such as those in Pennsylvania’s Marcellus Shale region, do require more care; but research has found that between 2008 and 2011, only a handful of major incidents happened across more than 3,500 wells in the Marcellus. We are learning and getting better. So this is a technical, well-integrity issue, not a deal-breaker. As for the flammable water, it is a fact that flammable water was a reality 100 years ago in some of these areas. It can be made slightly worse in a minority of cases, but it’s unlikely and it is often the result of leaks from activities other than fracking. In terms of disclosure, many of the chemicals are listed on data sheets available to first-responders: The information is disclosed to relevant authorities.

Fayetteville Shale, Arkansas

CON FRACKING: This April, yet another major study, published in the Proceedings of the National Academy of Sciences, confirmed that high-volume hydraulic fracturing techniques can contaminate drinking water. There have been numerous reports by citizens across the country of fouled tap water; it is a fact that some of the tap water has even turned bubbly and flammable, as a result of increased methane. Well blowouts have happened, and they are a complete hazard to the environment. The companies involved cannot be trusted, and roughly one in five chemicals involved in the fracking process are still classified as trade secrets. Even well-meaning disclosure efforts such as do not provide sufficient information. And we know that there are many who cut corners out in the field, no matter the federal or state regulations we try to impose. They already receive dozens of violation notices at sites, with little effect. We’ve created a Gold Rush/Wild West situation by green-lighting all of this drilling, and in the face of these economic incentives, enforcement has little impact.

Infrastructure, resources, and communities

ISSUE: Fracking operations are sometimes taking place near and around populated areas, with consequences for the local built and natural environments.

PRO FRACKING: Water intensity is lower for fracking than other fossil fuels and nuclear: Coal, nuclear and oil extraction use approximately two, three, and 10 times, respectively, as much water as fracking per energy unit, and corn ethanol may use 1,000 times more if the plants are irrigated. For communities, the optics, aesthetics, and quality of life issues are real, but it’s worth remembering that drilling operations and rigs don’t go on forever – it’s not like putting up a permanent heavy manufacturing facility. The operations are targeted and finite, and the productivity of wells is steadily rising, getting more value during operations. Moreover, the overall societal benefits outweigh the downsides, which are largely subjective in this respect.

CON FRACKING: More than 15 million Americans have had a fracking operation within a mile of their home. Still, that means that a small proportion of people shoulder the burden and downsides, with no real compensation for this intrusive new industrial presence. Fracking is hugely water-intensive: A well can require anywhere from two- to 20-million gallons of water, with another 25 percent used for operations such as drilling and extraction. It can impact local water sources. The big, heavy trucks beat up our roads over hundreds of trips back-and-forth – with well-documented consequences for local budgets and infrastructure. In places such as Pennsylvania, Ohio, and Colorado, the drilling rigs have popped up near where people have their homes, diminishing the quality of life and creating an industrial feel to some of our communities. This is poor planning at best, and sheer greed at its worst. It seldom involves the preferences of the local residents.

Finally, it’s also the case that relatively low impact fees are being charged and relatively little funding is being set aside to mitigate future problems as wells age and further clean-up is necessary. It is the opposite of a sustainable solution, as well production tends to drop sharply after initial fracking. Within just five years, wells may produce just 10 percent of what they did in the first month of operation. In short order, we’re likely to have tens of thousands of sealed and abandoned wells all over the U.S. landscape, many of which will need to be monitored, reinforced, and maintained. It is a giant unfunded scheme.

Earthquakes: Seismic worries

ISSUE: Fracking wells, drilled thousands of feet down, may change geology in a potentially negative way, leading to earthquakes.

PRO FRACKING: Earthquakes are a naturally occurring phenomenon, and even in the few instances where fracking operations likely contributed to them, they were minor. We’ve had tens of thousands of wells drilled over many years now, and there are practically zero incidents in which operations-induced seismic effects impacted citizens. There’s also research to suggest that the potential for earthquakes can be mitigated through safeguards.

CON FRACKING: We are only just beginning to understand what we are doing to our local geologies, and this is dangerous. The 2014 Annual Reviews of Environment and Resources paper notes that “between 1967 and 2000, geologists observed a steady background rate of 21 earthquakes of 3.0 Mw or greater in the central United States per year. Starting in 2001, when shale gas and other unconventional energy sources began to grow, the rate rose steadily to [approximately] 100 such earthquakes annually, with 188 in 2011 alone.” New research on seismology in places such as Texas and Oklahoma suggests risky and unknown changes. It is just not smart policy to go headlong first – at massive scale – and only later discover the consequences.

Also see: Pros and cons of fracking: Research updates

John Wihbey, a writer, educator, and researcher, is an assistant professor of journalism at Northeastern University and a correspondent for Boston Globe Ideas. Previously, he was an assistant director...