Wildfires on the west coast of North American have caused intense air pollution in several coastal cities.
But today, for a while, none of them were faring worse than Vancouver, B.C.
It briefly topped the list of cities with the highest U.S. Air Quality Index rating, scoring 194.
That was just slightly ahead of Portland, Oregon.
This number puts Vancouver deep in the "red zone", where some members of the public may experience health effects. There is a chance of more serious effects for members of sensitive groups.
"Persons with chronic underlying medical conditions or acute infections such as COVID-19 should postpone or reduce outdoor physical activity until the advisory is lifted, especially if breathing feels uncomfortable," Metro Vancouver states on its website.
The regional district warns that fine particulate matter—consisting of airborne solid or liquid droplets with a diameter of 2.5 micrometres or less—can move indoors.
This is especially worrisome for people with lung disease, heart disease, asthma, chronic pulmonary disease, or diabetes, as well as pregnant women, infants, children, and seniors.
However, less than after Vancouver was topping the list, Portland moved back into first place.
That's because Portland's rating soared to 235, moving it into the "purple zone". This warrants a health alert because the risks are elevated for everyone.
The screen shot below shows the eight cities with the worst air quality at 11:24 a.m.