High levels of carcinogens and toxic substances have been found in fish, water and sediment downstream from Alberta’s huge oil sands projects, according to a new study. The 75-page report, written by Kevin P. Timoney, an ecologist with Treeline Environmental Research, was commissioned by the local health authority of Fort Chipewyan, Alberta, where many residents say they believe the oil sands developments to the south are damaging their health.

Oil sands developments are generally vast open-pit mines that recover a form of tar mixed with sand. That tar, which is formally known as bitumen, is later separated and processed to produce oil. Most of the oil from the Alberta developments is sent to the United States.

Earlier studies by the province of Alberta had dismissed health concerns. And Dr. Timoney’s report, while highly critical of the government, does not make a specific link between the toxic substances and the oil sands. But many Fort Chipewyan residents did on Thursday. “For years the community has believed that there’s lots of cancer,” said Donna Cyprien, health director of the Nunee Health Authority. “When they drank from the water, there was an oily scum around the cup. We now know there is something wrong.”

Mrs. Cyprien said that the local health board hired Dr. Timoney largely because it had lost faith in Alberta’s provincial health department. Like Dr. Timoney, scientists who have reviewed his report say further studies are necessary to determine the cause and extent of the problem. But they also expressed concern about what his research had already found. “This could actually be worse, in some respects, than the Exxon Valdez,” said Jeffrey W. Short, a research scientist at the Alaska Fisheries Science Center who has studied the tanker accident that spilled 11 million gallons of oil off the Alaska coast in 1989.

Most disturbing, said Dr. Short, was the finding that from 2001 to 2005, concentrations in sediments of a group of chemicals called polycyclic aromatic hydrocarbons rose. “These are substantial increases over and above the natural levels,” said Dr. Short, adding that the hydrocarbons “are notorious carcinogens,” found in tar and tarlike materials. In some cases, they were more than four times recommended limits in the United States. (Canada has no guidelines.)

Dr. Timoney concluded that the town’s treated drinking water was safe, but found high levels of arsenic, mercury and polycyclic aromatic hydrocarbons in fish, which many people in Fort Chipewyan, especially members of its Native community, rely on for a substantial portion of their diet.

In an e-mail message, Howard May, a spokesman for Alberta’s Department of Health and Wellness, said that the government could not specifically comment on the report because it had not received a copy.

“There is nothing really new in these allegations, we have been looking into them for some two years now,” Mr. May wrote, adding that the government investigation has found “no higher incidence of cancer in Fort Chipewyan than the rest of the province, and we stand by that analysis unless and until we are provided with further evidence.”

(By Ian Austen, The New York Times, 09/11/2007)