The federal government is launching two reviews of a controversial natural gas drilling practice known as fracking, to address concerns it may be damaging to the environment.

Fracking releases natural gas from shale deposits deep underground by blasting large volumes of fresh water, sand, and chemicals into the rocks at high pressure.

What is fracking? Hydraulic fracturing, or "hydro-fracking," is a form of natural gas extraction in which a pressurized mix of water and other substances is injected into shale rock formations or coal beds to release trapped natural gas.

A fluid mixture of water and chemicals is injected under high pressure deep underground, creating or widening fissures in the rock.

Then, sand or other solids, often ceramic beads, are pumped in to keep the fissures propped open so that methane gas can escape from pores and fractures in the rock.

Federal Environment Minister Peter Kent has asked Environment Canada and a panel of independent scientists with the Council of Canadian Academies to conduct two parallel studies of its environmental impacts.

"We also need to know a great deal more...about this. What I'm trying to do now is accumulate the best scientific information about [it] to make sound decisions," said Kent.

Concerns about fracking's impact on the environment and ground water supplies have led to bans on the practice in Quebec, New York and France.

But in northern B.C. fracking for shale gas is a booming, billion-dollar industry that's growing rapidly with the full support of Premier Christy Clark.

"Fracking is safely regulated in British Columbia," Clark said earlier this September during an oil and gas announcement.

Kent says he's also confident fracking is being practiced responsibly in British Columbia and there is no reason for the federal government to step in and ban fracking now.

Critics of fracking, like Ben Parfitt of the Canadian Centre for Policy Alternatives, are welcoming news of an official federal review of the controversial drilling practice.

What are the environmental concerns? The process uses large amounts of fresh or potable water.

Space is needed to store the waste water safely; sometimes, this involves clearing trees or disrupting habitats.

The waste water must be treated at facilities that critics say are not always equipped to remove the contaminants particular to hydro-fracking.

The fear is that the chemicals used and released during fracking contaminate drinking- and groundwater — either during the process itself or through the waste water that is recycled and used afterward. The substances released along with the natural gas can continuing leaking from the well for decades after the extraction process.

Some of the methane gas being extracted during fracking escapes or is vented at the well head during the process and contributes to greenhouse gas emissions.

Some people living near fracking wells have complained of noxious fumes that they say cause headaches, nausea and other symptoms and that they attribute to some of the substances released during fracking, such as benzene and toluene.

Researchers say that shale gas extraction through fracking causes enough emissions to give it a bigger greenhouse gas footprint than conventional gas or oil.

"Any scrutiny by federal or provincial bodies is welcome news. We need to see, I think, greater attention paid to the potential for water resources to be degraded. Anything that happens by way of shedding light on what industry is doing is very important," said Parfitt.

Provinces take different approaches

B.C. Independent MLA Vicki Huntington said she welcomed the news of the two federal reviews, but questioned why the provincial government had not made a similar move, since natural resources are a provincial responsibility.

"B.C. should have led the way by announcing its own, independent examination of the environmental issues surrounding fracking," said Huntington.

"Instead, we now face a situation where the federal government may step into the scientifically-based policy and regulatory void vacated by the B.C. government. And so they should, if B.C. continues to avoid that responsibility," she said.

Critics in B.C. have also raised concerns that the B.C. government is allowing a natural gas company to draw water from a northern BC Hydro reservoir for fracking.

The practice has also generated protests and controversy in New Brunswick. This past June the government announced that it will require the disclosure of chemicals used in the contentious process, mandatory water testing and a security bond to compensate landowners if there are any accidents.

The New Brunswick government is also planning to set up a system that allows communities to tap into some of the natural gas companies’ profits.

In March the Quebec government said it would respect the findings of a report by the province's environmental-impact assessment bureau, commonly known as the BAPE, which recommended a halt to hydraulic fracturing until a study into its environmental impact is complete.

A panel of 11 experts has been mandated to undertake a strategic environmental assessment expected to take between two and three years. In the meantime, the province has cancelled exploration permits without compensation and issued a new set of regulations to govern shale gas development.