VANCOUVER -- The smoke from American wildfires, which is blanketing B.C.’s Lower Mainland, has prompted another air quality advisory. Anyone taking shelter in public buildings should maintain physical distancing to reduce the spread of the coronavirus. 

The alert, issued for the entirety of Metro Vancouver and the Fraser Valley, says that smoke is to blame for bad air quality and reduced visibility.

“Wildfire smoke from fires in Washington and Oregon has moved northward into the region this morning and is forecasted to impact air quality through the weekend as a large mass of smoke moves through,” reads the Environment Canada statement.

The advisory is a continuation of those issued earlier in the week, and comes as wildfires across the west coast of the United States have forced evacuations and claimed lives.

People with chronic underlying medical conditions or acute infections such as COVID-19 should delay or cut back on outdoor exercise until the advisory is lifted and “especially if breathing feels uncomfortable,” the statement reads.

The advisory comes at the tail end of summer, and during a week of high temperatures. It also comes amid the global coronavirus pandemic and mounting cases of COVID-19 infections in B.C.

“As we are in the summer season with warm temperatures, it is also important to stay cool and hydrated. Indoor spaces with HEPA air cleaner filtration and air conditioning may offer relief from both heat and air pollution, but physical distancing guidelines for COVID-19 should still be observed.”

On Friday, Vancouver ranked fourth on a list of cities with the worst air quality in the world — eclipsed only by three U.S. cities closer to the wildfires burning in U.S. pacific states.

Fine particulate matter, often referred to as PM2.5, refers to airborne solid or liquid droplets with a diameter of 2.5 micrometres or less. 

Because they are so small, these particles can easily get indoors.

“Exposure to PM2.5 is particularly a concern for people with underlying conditions such as lung disease, heart disease, chronic obstructive pulmonary disease (COPD), asthma, and/or diabetes, individuals with respiratory infections such as COVID-19, pregnant women and infants, children, and older adults,” says the statement.

It also says that people who are “socially marginalized” may be at elevated risk.

Anyone who chest discomfort, shortness of breath, coughing or wheezing, is advised to seek prompt medical attention or call 9-1-1 in case of an emergency.