Health risk from smoky skies off the charts in parts of B.C.

Smoke from more than 130 wildfires burning across the province is making the air hard to breathe in several B.C. communitiesincluding "very high risk"air conditions in the mountain resort of Whistler andit's likely to get worse before it gets better.

Kamloops in the B.C. Interior hadthe worst air in the province most of Wednesday, and reached 18 out of 10 on the Air Quality Health Index at about 1:00 p.m. PT, a level considered "very high risk."

The air quality there changed dramatically over the course of the day, risingfrom low risk levelsWednesday morning, to 18, then down to 8 in the afternoon.

By late afternoon, Whistler had the worst air conditions, hitting a 12 or "very high risk."

The Lower Mainland, though farther from the fires, hasnotbeen spared, as winds from the Interiorpush wildfire smoke through the valleys to the coast creating high riskconditions.

Here's how the air quality in some regions ranks on the index at 5:00 p.m. PT, for which 7 to 10 represent "high risk" conditions. Numbers higher than 10 are unusual and indicate a very high risk.

• Whistler 12
• Central Fraser Valley 10
• Squamish 8
• Eastern Fraser Valley 7
• Metro Vancouver NW 7

An air quality advisory hasbeen in place for Metro Vancouver and the Fraser Valley since Tuesday, but the smoke had stayed at higher elevations until Tuesday night, saidMetro Vancouver air quality planner Geoff Doerksen.

"Overnight, we've had widespread smoke get mixed down and fine particulate matter levels have become elevated in many parts of the region," said Doerksen, who monitors air from West Vancouver to Hope.

• Current air quality health ratings

"Air quality forecast models are predicting this trend to continueand air quality is likely to worsen throughout today."

Williams Lake in the Interior where air quality last month hit an off-the-charts 36 out of 10 wasalso high risk (7) as of mid-day Wednesday, though conditions were forecast to improve in that region later in the day.

Smoke could last days

The key measure driving the health warnings is fine particulate matter, also known as PM 2.5, which is much smaller than the width of a human hairand can go deep into thelungs and bloodstream.

When PM 2.5 levels cross a certain threshold of 25 micrograms per cubic metre that's enough to prompt health warnings, said Doerksen.

Burnaby and North Vancouver are just slightly above that threshold, while Hope hadmore than four times that amount as of 1p.m. PT.

Watch the wildfire smoke reach the Lower Mainland

At high risk levels, vulnerable people including children, the elderly, and those with heart or breathing problems are advised to reduce any strenuous outdoor activities.

At very high risk levels, those groups are advised to avoid any outdoor exertion.

The general population is also asked to exercise cautionand watch for symptoms like coughing and throat irritation.

"We typically experience very good air quality throughout the region, so to see our skies obscured by smoke is quite startling," said Doerksen.

The smoke is likely to stay for several days on the South Coast, as long as the hot weather and winds from the Interior persist, he said.

"Until there's a change in the weather, we'll be stuck with this."