Contaminants in the air and water from the Lac-Mégantic train disaster are steadily decreasing and pose no immediate or long-term environmental or health threats, according to test results made public by Quebec's Environment Ministry.

The release of those findings on Wednesday comes one day after a Quebec environment group, La Société pour vaincre la pollution (SVP), criticized the government for its handling of the cleanup following last month's train derailment.

'The levels of contamination that were hinted at yesterday are simply not there.'—McGill environmental research scientist Dr. Michel Bouchard

SVP reported finding dangerous levels of arsenic and other toxins in water samples it took six days after the oil spill and accused the Environment Ministry of being secretive about key data showing the extent of contamination.

Environment Minister Yves-François Blanchet dismissed that suggestion as ridiculous.

"I have every intention — and I've already announced — that we will make public and explain the findings," Blanchet said in an interview with Radio-Canada.

Blanchet said he isn't downplaying the extent of the environmental damage caused by the catastrophe.

"There is no question of minimizing that," Blanchet said in a statement. "On the contrary, people's health will be protected and damages will be cleaned up."

Levels of petroleum hydrocarbons on decline 

Among the key findings, the ministry said it has observed:

  • A decrease in the presence of petroleum hydrocarbons, the main contaminant from the spill.
  • A return to pre-spill levels of all other contaminants, both in Lac-Mégantic and the Chaudière River.
  • The water quality poses no short- or long-term danger to aquatic life.
  • The water is safe to drink. However, the restriction on drinking water in communities downstream from the spill remains in place, because of the risk of hydrocarbons settled in the sediment being stirred up by flooding or other sudden changes in the water level.

As far as air quality is concerned, the ministry said its mobile laboratory found a significant decline in airborne contaminants within two days of the July 6 derailment and explosions and a return to normal air quality by July 10.

Tests 'robust, scientifically acceptable,' McGill expert says

Dr. Michel Bouchard, an environmental research scientist at McGill University, said the findings are reassuring, but not unexpected.

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McGill research scientist Michel Bouchard says he's awaiting the most critical findings: soil contamination in the vicinity of the derailment. (CBC)

He said the Environment Ministry moved quickly to put in place booms and take other measures to limit the effect of the derailment, which spilled nearly 5.7 million litres of crude oil into the water, soil and air of Lac-Mégantic following the July 6 disaster.

He said he trusts the Environment Ministry's findings over those released on Tuesday by SVP.

"The results presented today are robust, are scientifically acceptable," and based on hundreds of samples, taken from locations well-described in the ministry's reports, Bouchard said. "It's not only one or two samples taken — we don't know where."

He said the results put to rest the "alarmist" findings announced by SVP, showing "the levels of contamination that were hinted at yesterday are simply not there."

Bouchard hypothesized that SVP based its data on samples taken directly from hydrocarbon "blobs" it collected, rather than water samples.

"If you do measure that, you are measuring the composition of the contaminant, but you are not measuring the contamination," Bouchard explained.

Still to come: 'red zone' findings

Bouchard, an international expert in environmental management and assessment, said the most critical findings are still being evaluated — the heavy soil contamination in the 60,000-square-metre "red zone" in the immediate vicinity of the derailment.

"Will it be possible to biodegrade on site or off-site, or, if this will not be possible, will we decide to transport it to a safe disposal site?" Bouchard asks.

He said none of those decisions can be made until the soil contamination has been thoroughly analyzed.

Bouchard said that determining the precise composition of the crude oil is an essential part of that work.

"This should have been made public at once," he said. "For scientists, we want to know the molecular weight, if there are other substances that were mixed with this light crude oil. We want to know the specific gravity."

"All these are quite important to model the soil contamination."