By MATT HUNT GARDNER

SYDNEY - For a second time, the petrochemical naphthalene has leaked from the cleanup site of the Domtar tank.

Sydney Tar Ponds Agency spokesman Parker Donham confirmed Wednesday that the strange smell near the Domtar tank earlier this week was caused by a leak of naphthalene.

"I was driving by Monday and noticed a smell that was different than a sewer smell," Mr. Donham said from Halifax.

He said air quality tests and a work stoppage were immediately ordered because last time a strange smell wafted from the Domtar tank, it was naphthalene leaking.

Naphthalene is a polycyclic aromatic hydrocarbon that smells like mothballs when released into the air.

The United States Environmental Protection Agency says naphthalene can cause hemolytic anemia, cataracts, jaundice, nausea, vomiting or abdominal pain.

Clean Harbours Canada Ltd. won the $3.6-million contract to clean up the Domtar tank, which holds coal-tar oil and toxins similar to those at Sydney's tar ponds.

The heating process used to make it easier to transfer the coal-tar oil to transport trucks is what produces naphthalene. Monitors are used daily to detect chemicals outside the building housing the tank.

On Monday, the monitors weren't working because of the stormy weather in Sydney. So canisters lined with resin were used to take samples, which were sent to ESL laboratories in Sydney.

Power outages meant it took until Wednesday afternoon to analyse the canisters.

Mr. Donham said two samples taken downwind of the tanks on Monday registered 1.37 micrograms of naphthalene per cubic metre of air and 3.92 micrograms of naphthalene per cubic metre of air.

He said the level is below the one-hour Sydney standard of 5.0 micrograms per cubic metre. The 24-hour naphthalene standard for Sydney is 3.0 micrograms per cubic metre.

Naphthalene was not detected in samples taken Tuesday, Mr. Donham said.

On June 4, the Sydney Tar Ponds Agency received test results from an air-monitoring station reporting an elevated level of naphthalene in the air on or before May 27. The reported level was 12.3 micrograms per cubic metre.

The leak shut down the cleanup until mid-July, and before work resumed, several changes were made to make gas leaks less likely.

Two fans the size of rail cars are used to keep negative pressure inside the building surrounding the Domtar tank, which keeps gases from leaking. Mr. Donham said the high wind Monday probably caused a pressure imbalance and the leak.

Clean Harbours stopped the cleanup work Monday. On Wednesday afternoon, workers began to heat up the coal-tar oil inside the tank and expected by evening to have a truck leave for Quebec, where the oil is being incinerated.