Water Treatment, Filters Lead to Lower THM Results
Municipalities addressing high trihalomethane, or THM, counts in their drinking water are seeing their efforts pay off.
Recent test results, carried out by the Department of the Environment and released today, show the greatest improvement is in Judique. That community measured the highest in the first round of testing and is now the lowest. A modified treatment technique that does not create THMs is being credited with the decrease.
Overall, the third round of testing on 20 municipal water supplies show 11 communities are below the Canadian drinking water quality guidelines of 100 parts per billion. Nine still have THM levels that are above.
Dave Wigmore, systems manager at the Department of the Environment, said the results show there are successful options for municipalities which are being proactive about THM treatment.
"Some of the techniques being used to lower THM levels are filters, other disinfection methods and new water treatment facilities," he said.
Mr. Wigmore said a recent meeting with a working committee of local water utility representatives and government officials addressed both short- and long-term solutions. Another meeting will take place this month.
He also said lower readings in this sample are typically due to fewer organics in the water this time of year. THMs are created when surface water containing high organics is chlorinated for drinking water.
The province's chief medical officer, Dr. Jeff Scott, said the results are not unexpected.
"Over time, fewer and fewer water utilities will be high, as water treatment technologies improve," Dr. Scott said.
Still, he said even though the risk of developing bladder cancer is very small, people can reduce THMs by using certified water treatment devices for THM removal or by using bottled water. The devices must be properly maintained to reduce THMs.
He repeated this is only the third test result and that four tests are needed to get an accurate reading.
Health Canada advises that a person would have to be exposed to high THM levels for at least 25 years or more to increase the risk of bladder cancer. The average male has about a one per cent chance of developing bladder cancer. With prolonged exposure to high levels of THM, the risk would increase to about 1.3 per cent. In women, the risk is less.
In 1993, the Canadian drinking water quality guideline for THMs was reduced from 350 parts per billion to 100 parts per billion.
The guidelines say water systems do not have to comply with the guideline immediately but over time compliance should be achieved when the systems are expanded or upgraded.
NOTE TO EDITORS: Following are the THM survey results for the 20 communities.
THM Survey Results, Spring 2000 (All results are in parts per billion; Canadian drinking water guideline = 100 parts per billion)
Municipality Fall Winter Spring Judique 453 100.1 <1
Hayden Lake 391 193 82.8
Liverpool 390 205.9 184.1
Coxheath/Westmount 309 135.5 106.4
Shelburne 299.3 55.9 35
Cornwallis 263 51.8 49.3
Bridgewater 252 459.9 338.7
Dingwall 238.1 74.9 100.4
New Glasgow 222 136.4 100.5
Antigonish 160 32.7 41.1
Windsor 159 194.1 143.7
Yarmouth 137.3 153 184
Mulgrave 121 62.3 45.8
East Hants 109 70.6 42.5
Mahone Bay 107.8 117.5 137
Kentville 103.7 39.2 16.9
Baddeck 103.3 30.6 30.8
Stewiacke 101 25.8 31.5
Glace Bay 84.9 189.6 243
Arichat 8.2 107.2 55.4