In Exxon Mobil's recent TV ad campaign, a camera tracks across a scenic landscape as a company geologist reassures us that the key to our national energy security lies just below our feet. "Technology has made it possible to safely unlock this clean and green natural gas," he says.

What you won't hear in the Exxon ad is the name of this technology: fracking. The controversial drilling method has become the new F-word after being linked to environmental calamities in at least a half dozen states.

These calamities are well documented and difficult to dispute. In Pennsylvania, Ohio and New York, explosive methane gas and hazardous fluids from fracking operations have contaminated drinking water, private wells and rivers. In several states, drilling companies have irresponsibly disposed of tainted wastewater, spilling toxic chemicals into streams and groundwater and sending radioactive wastewater to city sewage treatment plants that were unequipped to filter those kinds of materials.

Fracking is illegal in North Carolina—for now—and we would be hard-pressed to look for good examples of regulation in other states, where laws and enforcement of fracking are piecemeal at best.

"No state is a model that shows this can be done safely," says Molly Diggins, state director of the N.C. chapter of the Sierra Club. "In fact, it's quite the opposite. There's been one disaster after another."

There is little guidance from the federal government, which six years ago agreed to exempt fracking fluid—which can contain not only water and salts but cancer-causing chemicals—from many key federal clean-water regulations.

Yet given the dangers and unknowns, some North Carolina lawmakers are determined to legalize fracking in our state, especially in areas near the Triangle. Many of these legislators have cribbed their talking points from industry, claiming fracking can be done safely if it's well regulated—a big if. These proponents of fracking justify the practice by contending natural gas production will generate state revenue in royalties and taxes and help ensure our energy independence.

But several North Carolina environmental groups and scientists are skeptical that, given the power of the energy industry and the Legislature's proposed 23 percent cut to DENR's budget, the state can adequately regulate fracking to protect human health and the environment

And unlike Texas, which has an extensive history of oil and gas drilling and mineral rights laws (although the agency in charge, the Railroad Commission, is lodged deeply in the energy industry's pocket), North Carolina has little if any expertise in permitting and regulating fracking.

"Whether North Carolina wants to frack natural gas is unresolved. North Carolina needs to ask itself the question: Do we want to run the risks in favor of any benefits?" said Sam Pearsall, a senior scientist with the Environmental Defense Fund. "I don't see those questions answered. Properly enforced we could go ahead, but I can see how we might decide the risks are too great. Do we want that part of the world crisscrossed with roads and pads and hundreds of tankers coming in and out?"

About 200 million years ago, dinosaurs roamed the land that is now traversed by N.C. 751 and U.S. Highways 1 and 421 in the Triangle. The supercontinents, also known as pangea, began to separate, and in this part of the world, formed the Atlantic Ocean. Portions of what would become North Carolina split like slices of cake being pulled apart. The rift left valleys that over time filled with plants, dirt and other organic matter.

Millions of years of heat and pressure baked the sediment into seams of fossil fuels, including coal, oil and natural gas. These fuels are thought to be in the Triassic Basin, a subterranean swath that cuts from southwestern Granville County through Durham and parts of Wake, Chatham, Lee and Moore counties.

More than a half-mile below the earth's surface, particularly in southern Chatham and Lee counties near the Deep River, geologists and energy companies believe there is an untapped resource of shale gas. There are larger shale gas fields in Pennsylvania, New York, Texas and Wyoming; the one in North Carolina "is not a giant field, but it's a field," Chief of the N.C. Geological Survey Ken Taylor told the House Environment Committee.

Until the last decade, shale gas had remained largely unexplored in the U.S. because the technology had not been developed to reach gas that was buried so deeply and trapped in such compact rock. But fracking and horizontal drilling solved that problem. Fracking forcefully injects water and other chemicals into rock to fracture it and release the trapped gas that is then captured at the surface.

The combined effect of technological advances with the energy industry's influence and the political push to develop domestic fossil fuels all served to make fracking the supposed panacea for the nation's energy woes. In 2009, 63 billion cubic meters of gas was produced from deep shale formations, according to the U.S. Energy Information Administration. In 2010, production doubled to 138 billion cubic meters. In the next 25 years, shale gas is expected to amount to nearly half of the projected gas production in the U.S.

In North Carolina, fracking hasn't occurred because, in part, horizontal drilling is illegal. The state's underground injection program prohibits injecting wastewater or pollutants that could contaminate drinking water into an aquifer. These rules apply to fracking because the flowback—chemicals, salts, sands and other wastewater that is belched with the gas (think of it as acid reflux in a well)—is often reinjected into aquifers deep within the ground.

But that could soon change. With Republicans in charge of the General Assembly, the state's energy focus is shifting from renewables and energy efficiency back to fossil fuels, including offshore drilling and fracking for natural gas.

"It's my intention to move ahead with this drilling as long as it's safe and sound," said Mitch Gillespie, a Republican from Burke County and a primary sponsor of House Bill 242, which directs the N.C. Department of Natural Resources (DENR) to study fracking (see "Drill your legislators on fracking".)

Vik Rao, a former vice president at Halliburton and a longtime Sierra Club member, was among the main attractions at last month's Sustainable Energy Conference at N.C. State University.

Rao is now the executive director of the Research Triangle Energy Consortium, a partnership among Duke University, UNC, N.C. State and the nonprofit RTI, a research institute.

Rao supports fracking, and at the conference, he addressed the inevitable questions about the method's environmental hazards. His solutions to these problems, while earnest and theoretically possible, would require us to trust regulators and the energy companies.

The first environmental hazard posed by fracking is water quantity. Fracking requires enormous amounts of water—3 million to 5 million gallons per well—to blast into the rock.

North Carolina doesn't regulate large water withdrawals, leaving the state's waterways vulnerable especially during droughts. The 2007 drought drained many of the state's waterways—that summer the bed of Falls Lake was dry—and also depleted shallow groundwater.

In southern Chatham and Lee counties, fracking could harm the Deep River and its watershed. "It's already a dry basin with almost no groundwater," said Pearsall of the Environmental Defense Fund. "And the surface streams don't carry a lot of water. It's hard to say if there is enough water to frack."

About a third of the amount of water that is initially injected into the well returns as flowback, or discharge. It is often dozens of times saltier than the original fluid and contains fracking chemicals. That means it should not be dumped into lakes and rivers or pumped into shallow groundwater aquifers.

Rao's answer to the water withdrawal problem is to reuse the discharge, although that would still require some new water to mix with the old. Another possible solution is to use saltwater from saline aquifers, eliminating the need for fresh water. Fracking chemicals would need to be tinkered with to work with saltwater, but it's possible.

"The industry took the easy way out and used fresh water because it's free," Rao said.

Or drilling operators could inject the discharge into deep aquifers—commonly done in Texas—that have no known use. (That's not to say, though, the aquifers will never be used.)

Excess discharge presents another problem for drilling companies: disposing of it. In North Carolina, it is illegal to put those materials back in the ground, although in Texas wells are designated for just that purpose—and they can fail. (See this story about how a faulty disposal well in East Texas polluted a neighborhood's drinking water supply.)

In Pennsylvania, some operators have shipped the discharge to wastewater treatment plants. But these plants can't handle or even detect many of the types of chemicals and salts and, in some cases, naturally occurring radioactivity. In Pittsburgh, radioactive material from discharge passed through a city treatment plant and wound up in the drinking water supply.

"This is not the kind of wastewater that municipal treatment plants are designed to treat," DENR Assistant Secretary for the Environment Robin Smith told legislators.

Some companies store the flowback in tanks and recycle it, although that could intensify the levels of contamination as the fluid is reused. Other operators discharge it in lined lagoons and let it evaporate, although that method can produce air toxins and hazardous residue. The liners can also break. "At some point, you're running out of options," Pearsall said.

Water can also become contaminated by methane, which comprises 99 percent of natural gas. High levels of methane have been found in drinking water wells near fracking sites in Pennsylvania and New York. The levels have been so high, as documented in the anti-fracking documentary Gasland, that some residents can ignite water running from their kitchen faucet.

A peer-reviewed study released Monday by four Duke University scientists for the first time authoritatively linked fracking and shale gas to methane levels in drinking water wells, a connection the industry energy had long denied.

The scientists surveyed 60 drinking water wells in Pennsylvania and New York and found that wells near gas extraction sites had, on average, 17 times higher levels of methane gas than wells that weren't.

"Essentially, the closer you are to a natural gas well, the more likely you are to have methane in your drinking water well," said Rob Jackson, one of the scientists involved in the study. "What surprised me was the consistency of the results."

Scientists analyzed the chemical and radiological makeup of the methane found in the wells and concluded it was similar to the methane formed under heat and pressure in deep shale where the fracking was occuring. The methane found in the wells, however, was different from the type formed by bacteria and is generally found in shallow wells.

The immediate danger of methane in drinking water is that it can build up in the well or in a home and explode. Last year, a well in Pennsylvania did just that, as did a home in 2007 in Ohio. In both cases, state investigators concluded methane from nearby extraction sites contributed to the explosions.

The health effects of drinking water containing methane are unknown, although residents whose wells are contaminated have complained of headaches, rashes and other ailments. The federal government does not regulate methane in drinking water.

In a subsequent paper, Jackson and his colleagues listed several recommendations. Those included an independent medical panel review of the health effects of inhaling methane and drinking water that contains the gas. The team also recommended that government officials sample drinking water and groundwater before and after drilling.

Rao blames "a bad cement job, bad well casings" for methane leaks. "This can be completely prevented," he told the Indy. However, Rao acknowledged that if the Duke study holds up to further review, then "unfortuantely for the nation and the industry," something is at work beyond bad cement.

A greenhouse gas, methane also pollutes the air—it's also emitted from landfills and cattle farms—and contributes to global warming more than carbon dioxide. A Cornell University study found that over the lifetime of a fracking well, 3.6 percent to nearly 8 percent of the gas will escape into the air. Pollution from methane and fracking activities have created ozone levels near one town in Wyoming that are higher than in Los Angeles, according to a New York Times report.

While Duke scientists' methane findings were startling, they did not discover evidence of fracking fluid or radioactivity in drinking water wells. However, hundreds of thousands of gallons of fluids have spilled into Pennsylvania rivers and streams, harming ecosystems and water supplies.

These cautionary tales gave state Rep. Kelly Alexander, D-Mecklenburg, pause. He was among the members of the House Environment Committee to address the water and disposal problems. "I'd like to urge a very serious look at the use of water and groundwater contamination issues," he said. "That's something that is extremely serious and we should be careful about it."