Depending on where they live in Shannon, some residents in the town of 5,000 that borders CFB Valcartier are 249 per cent more likely than others in the same town to develop cancer, according to one medical expert's analysis of a public health study that's not yet been made public.

Dr. Claude Tremblay, who represents Shannon residents on an experts' committee reviewing the impact of trchloroethylene (TCE) contamination in some local wells, has looked at epidemiological data compiled by the regional public health authority.

Tremblay has concluded that – depending on where they live in the community – some Shannon residents are at greatly elevated risk of developing cancer of the kidney and liver, as well as non-Hodgkin's lymphoma.

'Red triangle' residents at greatest risk

This is especially the case for those living in area known as "the red triangle" – the zone where TCE levels in groundwater have been found to be at their highest.

TCE is commonly used as a degreasing agent, and in 1997 it was discovered to have leached into the drinking water supply system at the Valcartier base. Three years later, it was detected in private wells in neighbouring Shannon.

Some Shannon wells have recorded levels of TCE that are up to 180 times what is considered acceptable by Health Canada.

Report not yet final: regional health authority

The regional health authority in the Quebec City region, the CIUSSS de la Capitale Nationale, countered Tremblay's conclusions Monday.

It said the public health report into TCE contamination of private wells that Tremblay refers to, which was ordered three years ago, is not yet final.

"Mr. Tremblay interpreted data in a document that isn't valid yet," said CIUSSS spokesman René Bouchard. "There is a final report that is currently in the hands of the committee of experts at this very moment."

The final report is due in March or April.

A long legal battle

A Shannon citizens' group said Tremblay's findings confirm what they have long been claiming, that there is a link between elevated TCE levels in their drinking water and reported cases of cancer in the town.

However, the federal government has denied that Shannon residents were ever exposed to high enough quantities of TCE, and for long enough periods, to cause cancer.

A Superior Court justice agreed with the government's position in a 2012 ruling, although the judgment acknowledged that there had been contamination of the town's drinking water. 

Citizens in Shannon are appealing that decision, which limited to 300 the number of people who could claim $15,000 in damages. 

They plan to ask the Quebec Court of Appeal to include Tremblay's findings in a hearing scheduled for Feb. 22.