VANCOUVER -- Vancouver's air quality is among the worst in the world, Environment Canada said Monday, as wildfire smoke continued to waft across the border from the United States, even reaching parts of Alberta.

An air quality advisory was issued for a seventh straight day in Vancouver and is expected to last into the weekend.

Relief will not come quickly for B.C. residents, as the air is expected to improve only marginally by Tuesday, said Blaine Lowry, a warning preparedness meteorologist with Environment Canada.

“They are looking for a brief reprieve mid-week. But in terms of a true improvement in the air quality condition, they are looking towards the weekend for that to potentially happen,” said Lowry.

The air quality index in Vancouver showed smoky conditions so poor on Monday that the city ranked as among the worst of the world's major cities, along with Portland, Ore., and Delhi.

The index uses a scale of one to 10 to rank risk from stagnant or smoky air. It listed the risk at 10-plus for all but the northern quarter of B.C.

The smoke is coming from hundreds of wildfires burning across in California, Oregon, and Washington, which have destroyed whole communities and killed at least 35 people. It has also blown towards four regions of southwestern Alberta along the Rockies, but the weather office said the smoke was likely to exit Alberta province Monday night.

Environment Canada advises people with chronic medical conditions or acute infections such as COVID-19 to postpone or reduce outdoor physical activity until the advisory is lifted, especially if breathing feels uncomfortable.

However, as a dense, fog-like haze shrouds many cities, from Victoria and Vancouver east to Kelowna, Kamloops and the Kootenay area, some runners haven't been afraid to spend time outdoors.

Elizabeth Thai said the smoke hasn't stopped her and other runners from hitting the streets of Vancouver.

The running coach at Rackets and Runners completed a 15-kilometre run on Saturday with about 15 other people.

“Our run club leaders and coaches were very good about not putting the pressure on anyone to have to come out,” Thai said.

None of her fellow runners reported health concerns, Thai added. But moving forward, they will decide whether to run depending on how fellow runners are feeling.

If people are going to spend time outdoors during the advisory, Lowry said it is recommended they not wear cloth masks that do little to filter out fine particles found in smoke. He recommends masks more suited for smoke prevention.

This report by The Canadian Press was first published Sept. 14, 2020.

- By Fakiha Baig in Edmonton

This story was produced with the financial assistance of the Facebook and Canadian Press News Fellowship.