A vast study of past and present residents of Shannon, Que. has concluded those residents have a higher incidence of liver and biliary tract cancer than other Quebecers – but researchers don't know if Shannon's history of contaminated water is to blame.

The regional health authority in the Quebec City region, the CIUSSS de la Capitale Nationale, released the findings Thursday.

TCE-laced water discovered in 1997

This is the first time public health officials have issued a report on the potential impact of Trichloroethylene (TCE) contamination on the health of the community.

It comes 19 years after the industrial solvent was first found to have leaked into the drinking-water supply system on the neighbouring Valcartier military base. 

In 2001, TCE, which is commonly used as a degreasing agent, was detected in private wells in Shannon.

Some Shannon wells tested since have recorded levels of TCE 180 times what is considered acceptable by Health Canada.

Residents believe the contamination has led to higher than average rates of cancer.

Health records examined

The CIUSS looked at the health records of 17,397 people who lived in Shannon between January 1987 and the end of February, 2001.

It found 10 incidents of liver or biliary tract cancer between 1987 and 2010 – double the rate observed overall in Quebec in a similar population.

Researchers also examined the incidence rate of three other kinds of cancer: kidney, brain and non-Hodgkin's lymphoma. However, they did not find elevated incidence rates for those specific cancers, nor for cancer in general.

Report should be reassuring, says public health director

The director of public health at the CIUSSS, Dr. François Desbiens, said he hopes the findings reassure people in Shannon that they're not at greater risk for most types of cancer than any other Quebec resident.

"We're telling the people they should not be afraid, not stressed about the health hazards related to TCE, because there is no more Trichloroethylene since 2001," Desbiens said.

CIUSSS Shannon cancer findings

The public health study found Shannon residents had double the expected rate of liver and biliary tract cancer, however they were not diagnosed with other cancers at a rate higher than that of the general population. (CIUSSS de la Capitale-Nationale)

additional reporting by Kate McKenna, graphics by Ariane Pelletier