An environmental group is criticizing the government for its handling of the Lac-Mégantic, Que., cleanup, and says the province is not releasing enough information about the environmental contamination.

Nearly 5.7 million litres of crude oil spilled out of derailed train cars and leached into the water, soil and air of Lac-Mégantic following the July 6 disaster.

But the government has yet to release any information about the potentially harmful contaminants in that oil and their effect on the environment.

The Quebec environmental group Société pour vaincre la pollution (SVP) took matters into its own hands and tested samples from the Chaudière River, which runs through town, a week after the train derailment.

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About 5.7 million litres of crude oil spilled into the air, water and soil in Lac-Mégantic, Que. (CBC)

The SVP released those results today, which suggest a severe impact on water quality and soil in the affected area.

The analysis suggests extremely high levels of polycyclic aromatic hydrocarbons, a figure 394,444 times the standard acceptable for surface waters mandated by the provincial government.

Polycyclic aromatic hydrocarbons are potential carcinogens materials commonly found in crude oil.

"The toxicity of this oil is quite high, which means people have to take extra precautions during cleanup," said Daniel Green,  co-president of the SVP.

As well, the concentration of arsenic detected on the water's surface is said to have exceeded the government's acceptable standard by 28 times.

The SVP worked in collaboration with Greenpeace on the study.

The organization acknowledged that "because of its limited resources," it was unable to perform the chemical analyses required to identify all the toxins, but said it hoped to carry out a second round of tests.

Concerns about recontamination

The results suggest that the ecosystem could be facing long-term consequences, according to Green.

He said many of the contaminants might have settled along the bottom of the river, and if the oil isn’t removed before winter, the spring melt could recontaminate the shoreline.

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Floating barriers were set up along the Chaudière River after the derailment to stop the spread of oil. (CBC)

But an environmental assessment expert with McGill University said it’s possible the concentration is not as widespread as it seems.

Prof. Michel A. Bouchard said he thinks it’s more likely the oil sank to several pockets along the bottom of the Chaudière River.

Either way, he said, the government should be more transparent.

"I don't see why this would be contentious material. I don't think it's a public security issue. Frankly, I can't give you an answer," Bouchard said.

Waiting for answers from the province

Green said the people of Lac-Mégantic should have access to the information they need to protect themselves.

So far, information about the exact chemical makeup of the oil has not been made public.

The Transportation Safety Board and the Environment Ministry have yet to release the results of their tests.

CBC News contacted the office of Environment Minister Yves-François Blanchet, but the ministry was not willing to comment on the findings.

"They've done extensive sampling — air, water and soil, and we've yet to see any results from the government on this environmental catastrophe," Green said.

With files from The Canadian Press