Today, all of the major oil companies can be found in the once sleepy town of Fort McMurray, northern Alberta. The town sits just south of the state's most significant tar-sand reserves — which house 173 billion barrels of recoverable crude oil. Over the past 14 years, the population of this town has increased by 50,000, owing to the development of cheap methods for extracting oil from the tar sands.

Credit: STILLS COURTESY OF DOGWOOF

Each day, coach loads of workers exit the city, and make their way down what locals refer to as the 'highway to hell', to make enviable amounts of money in the oil mines. Young men with little education can earn over $100,000 a year by operating huge digger trucks. Nothing, of course, compared with the billions of dollars that the industry draws in for the Canadian government.

The documentary Dirty Oil delves into the darker side of the Albertan tar-sand industry. Razed forests, congested highways, toxic ponds and polluted skies all bear testament to the environmental toll. In a series of interviews with scientists and journalists, it becomes clear that the tar sands are a colossal source of greenhouse-gas emissions. Waste water from the operations — laden with arsenic, mercury and a host of other toxic compounds — is pumped into huge artificial lakes, termed tailings ponds. Wild animals, including moose and wild fowl, drink from these ponds. And the sand linings do little to prevent the water leaching into the surrounding environment; one study reported losses of 5.7 million litres of toxic water a day from just one pond.

Local aboriginal communities have absorbed a lot of the shock. In a hamlet 10 miles downstream from the state's main mining operations, residents have resigned themselves to the erosion of their culture and way of life. Before the arrival of the oil firms, they wandered freely in the forest. Now they are trapped in by fences, cordoning off ever-expanding sections of the wilderness, and have to keep their windows shut at night because of the stench from the mines. A nearby creek that used to supply drinking water and fresh fish is now toxic, and the fish — deformed and covered in sores — are no longer fit for human consumption. Asthma, once unheard of, is now commonplace.

Each day, coach loads of workers exit the city, and make their way down what locals refer to as the 'highway to hell', to make enviable amounts of money in the oil mines.

Farther downstream in the 1,200-strong aboriginal town of Fort Chipewyan, rare forms of cancer are rife. The resident doctor describes with some disturbance the way in which his medical reputation was called into question by the Alberton and federal governments when he raised concerns about the health of the locals with scientists. Accusations of irresponsible practice and raising undue alarm, as well as threats to take away his licence, clearly took their toll. Meanwhile, a friendly looking representative from the Albertan government quotes excellent environmental standards and impressive land-reclamation strategies.

Unfortunately, these powerful scenes are mixed up with overly sensationalist shots of melting ice caps, references to the end of civilisation and protests from niche celebrities (Eddie Vedder). This might sound interesting, but the attempt to cover virtually every aspect of the industry's environmental impact — from climate change to pollution in Lake Michigan — significantly detracts from the most interesting aspect of the film: the all-too-familiar struggle between big business and local communities. As a result, many issues are skirted over, and the structure of the film — if present — is difficult to decipher.

In the final scenes, empowering speeches by Obama, in which he calls for an end to the age of oil, are intertwined with references to the mobilization of the American people during the Second World War (to make weapons and planes). Inspiring perhaps, but the overly positive tone assumes that the film engaged you in the first place.

That said, the documentary raises awareness of the environmental issues connected with Albertan oil exploration. And with Britain and China looking to invest in the oil sands — now that the US is starting to withdraw funding — the industry needs all the scrutiny it can get.