Finding the real risks
of contaminated sites
By Nathan Kim

OTTAWA — Canada has over 4,000 areas that Health Canada has designated as contaminated. Along with these sites there are around 30,000 designated brownfield sites, which are contaminated areas that may potentially be cleaned up and redeveloped.

Contaminated sites like this one may not be as risky as they seem.

But not all of these sites actually pose any risk to people even though they contain toxin levels that are supposedly unsafe, says Ken Reimer, director of the Environmental Sciences Group at the Royal Military College in Kingston.

Reimer says that although toxins may exist in an area, the bioavailability of the toxin must be determined before one can know just how dangerous the site may be to people.

Bioavailability is the amount of the toxin that is actually absorbed in the human bloodstream and is therefore potentially dangerous to people.

Finding the real risk

Reimer says there are three stages that he and his team of scientists work through when dealing with contaminated areas.

The first step is site assessment, or determining just how contaminated the area is. The second step is finding out exactly how much of a risk the area poses to people or animals and lastly, what can be done to clean up the site.

Reimer says much of his work is focused on the second step.

Because the concept of bioavailability and risk assessment is quite new, Reimer says that a lot of his team's work is to find new ways to determine how much of the existing toxins may actually pass into a person's bloodstream.

The team has developed a new technique which involves simulating the chemical composition of the various stages of the human digestive system in containers in a laboratory, and then shaking samples from contaminated sites in the containers to see how much of the toxin would be dissolved and potentially absorbed if ingested by a person.

Reimer says this test was used to explain why animals and people did not seem to be affected by elevated levels of arsenic found in Yellowknife, North West Territories.

Yellowknife has naturally elevated arsenic levels that are as high as 150 parts per million. The acceptable levels of arsenic in soil, as outlined by Health Canada, is only 12 parts per million. Despite the high levels of the toxin, Reimer's team noticed that mice populations were flourishing near mines where toxin levels were often even higher.

"If you did a conventional risk assessment, the mice living near the mine should all be dead," Reimer says.

The conventional risk assessment only considered toxin levels and did not look at how much of the area's toxins were actually absorbed by people or animals. Reimer's team found that only five per cent of the available toxin in soil samples was dissolved by the body, even if directly ingested. This meant that there was actually little risk to people in Yellowknife, despite the alarmingly high levels of arsenic.

Cleaning the mess

Plants may play a major role in cleaning up contaminated sites in the future.

Reimer's team is also conducting research into what can be done when contaminated sites are found to pose a risk to people.

The team is focusing on biological agents, such as microscopic organisms or plants, to clean up problem areas.

"Typically, soil from contaminated sites is dug-up and sent to incinerators which is very expensive," Reimer says. "We've had good success in using plants in remediation."

Reimer points out a resent study that found certain types of grasses and pumpkins proved particularly good at absorbing toxins released during transformer fluid spills which, at high levels, can cause neurological problems in people.

Treating the public

By showing just how much risk the contamination may actually pose and offering inexpensive ways to clean up sites, Reimer recognizes he is in a position to help change people's perception on dealing with this widespread concern.

"I think it is really important to alleviate some of the fears in the public," Reimer says. "We've found we’ve been very successful with this. It’s a remarkably comforting for people when they see the actual risk factor in numbers."

Reimer says he is also trying to teach policy makers that just because a site is contaminated it may not be hazardous and that expensive soil cleaning methods may not be necessary.

Reimer says governments are wasting money and resources trying to cleanup sites that pose little or no risk to people.

"Bioavailability should be the cause for action," says Reimer. "Right now, the total amount of contaminants is used to determine action."

Still, Reimer says the concept of bioavailability is slowly catching on. A new organization called Bioaccessibility Research Canada was created in August 2004 to evaluate on the risk factor of contaminated sites, not just the fact that they are contaminated.