Change in pollution
levels from 2019-2020
Cleaner air
More polluted
-50
-10
10
50
100
329%
-85%
Portland
San
Francisco
Akron
Salt Lake City
Washington
Los Angeles
Change in pollution
levels from 2019-2020
Cleaner air
More polluted
-50
-10
10
50
100
329%
-85%
Portland
San
Francisco
Akron
Salt Lake City
Washington
Los Angeles
Change in pollution
levels from 2019-2020
Cleaner air
More polluted
-50
-10
10
50
100
329%
-85%
Seattle
Portland
Boston
Minneapolis
Salt Lake City
Chicago
Akron
San Francisco
Denver
Washington
Yosemite Lakes
Los Angeles
Charlotte
Phoenix
Houston
Honolulu
Miami
Anchorage
Change in pollution
levels from 2019-2020
Cleaner air
More polluted
-50
-10
10
50
100
329%
-85%
Seattle
Portland
Boston
Minneapolis
Salt Lake City
Chicago
Akron
San Francisco
Denver
Washington
Yosemite Lakes
Los Angeles
Charlotte
Phoenix
Houston
Honolulu
Anchorage
Miami
Change in pollution
levels from 2019-2020
Cleaner air
More polluted
-50
-10
10
50
100
329%
-85%
Seattle
Portland
Boston
Minneapolis
Salt Lake City
Chicago
Akron
San Francisco
Denver
Washington
Yosemite Lakes
Los Angeles
Charlotte
Phoenix
Houston
Honolulu
Anchorage
Miami
Wildfires that charred millions of acres in the West wiped out the country’s pandemic-related clean air gains in 2020, according to a report released this week.
Because pandemic restrictions limited travel and other activities, fine-particle pollution from the burning of fossil fuels dropped 13 percent between March and July compared to the previous year and dipped again in November and December, said Lauri Myllyvirta, lead analyst at the Centre for Research on Energy and Clean Air, who collaborated on IQAir’s annual World Air Quality Report.
But the 2020 historic wildfire season more than made up the difference. Overall, the U.S. average for the deadliest type of air pollution rose nearly 7 percent over 2019 because of smoke from fall fires, primarily those in California, Oregon and Washington.
[How escalating climate change fuels California's infernos]
Fine-particle pollution refers to bits that are 2.5 microns in diameter or smaller, or less than one-20th the diameter of a human hair. These particles are tiny enough to penetrate deep into lungs and enter the bloodstream, where they can trigger asthma attacks and other lung and heart problems and may cause cancer.
While no fine-particle pollution is considered to be safe, the World Health Organization’s about target is 10 parts per cubic meter or less. In 2020, the U.S. average was 9.6, and thirty-eight percent of U.S. cities exceeded the target level compared to 21 percent in 2019.
The country’s worst annual average was in Yosemite Lakes, Calif., 37.8 micrograms per cubic meter. The highest U.S. reading was 4,709.3 during heavy smoke in Weed, Calif., on Sept. 13.
In September, 24 of the world’s top 25 most polluted cities were in California and Oregon, the report said. Leading the list was Happy Camp, Calif., with a monthly average of 154.4 micrograms per cubic meter. The city with the lowest fine pollution levels recorded was Waimea, Hawaii, with 2.2.
On Sept. 13, Portland saw PM2.5 levels 10 times higher than the limit recommended by the World Health Organization
Portland, Ore:.
15 days above WHO guidelines
for fine particulate matter
200 μg/m3
fine particulate matter
(PM2.5),
daily average
100
30-day rolling average
Daily guidelines for
fine particulate exposure
25
0
Jan.
2021
Jan.
2020
July
Los Angeles: 48 days
100 μg/m3
50
25
0
Jan.
2021
Jan.
2020
July
San Francisco: 24 days
100 μg/m3
50
25
0
July
Jan.
2021
Jan.
2020
Seattle: 12 days
100 μg/m3
50
25
0
Jan.
2021
July
Jan.
2020
Washington, D.C.: 4 days
100 μg/m3
50
25
0
Jan.
2021
Jan.
2020
July
Boston: 2 days
100 μg/m3
50
25
0
Jan.
2021
Jan.
2020
July
Phoenix: 2 days
100 μg/m3
50
25
0
July
Jan.
2021
Jan.
2020
On Sept. 13, Portland saw PM2.5 levels 10 times higher than the limit recommended by the World Health Organization
Portland, Ore:.
15 days above WHO guidelines
for fine particulate matter
200 μg/m3
fine particulate matter
(PM2.5),
daily average
100
30-day rolling average
Daily guidelines for
fine particulate exposure
25
0
July
Jan.
2021
Jan.
2020
Los Angeles: 48 days
100 μg/m3
50
25
0
Jan.
2021
Jan.
2020
July
San Francisco: 24 days
100 μg/m3
50
25
0
Jan.
2021
July
Jan.
2020
Seattle: 12 days
100 μg/m3
50
25
0
Jan.
2021
July
Jan.
2020
Washington, D.C.: 4 days
100 μg/m3
50
25
0
Jan.
2021
Jan.
2020
July
Boston: 2 days
100 μg/m3
50
25
0
Jan.
2020
July
Jan.
2021
Phoenix: 2 days
100 μg/m3
50
25
0
Jan.
2021
July
Jan.
2020
Portland, Ore:.
15 days above WHO guidelines
for fine particulate matter
On Sept. 13, Portland
saw PM2.5 levels 10 times higher than the limit recommended by the World Health
Organization
200 μg/m3 fine particulate matter
(PM2.5), daily average
100
30-day rolling average
Daily guidelines for fine particulate exposure
25
0
Feb.
March
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Jan.
2021
April
Jan.
2020
Los Angeles: 48 days
San Francisco: 24 days
100 μg/m3
50
25
0
Jan.
2021
Jan.
2021
Jan.
2020
July
July
Jan.
2020
Seattle: 12 days
Washington, D.C.: 4 days
100 μg/m3
50
25
0
Jan.
2020
July
Jan.
2021
Jan.
2021
July
Jan.
2020
Boston: 2 days
Phoenix: 2 days
100 μg/m3
50
25
0
July
Jan.
2021
July
Jan.
2021
Jan.
2020
Jan.
2020
Portland, Ore:.
15 days above WHO guidelines
for fine particulate matter
On Sept. 13, Portland
saw PM2.5 levels 10 times higher than the limit recommended by the World Health Organization
200 μg/m3 fine particulate matter
(PM2.5), daily average
100
30-day rolling average
Daily guidelines for fine particulate exposure
25
0
Feb.
March
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Jan.
April
Jan. 2020
Los Angeles: 48 days
San Francisco: 24 days
100 μg/m3
50
25
0
Jan. 2021
Jan. 2021
July
July
Jan. 2020
Jan. 2020
Seattle: 12 days
Washington, D.C.: 4 days
100 μg/m3
50
25
0
Jan. 2021
Jan. 2021
July
July
Jan. 2020
Jan. 2020
Boston: 2 days
Phoenix: 2 days
100 μg/m3
50
25
0
Jan. 2021
Jan. 2021
July
July
Jan. 2020
Jan. 2020
Portland, Ore:.
15 days above WHO guidelines
for fine particulate matter
On Sept. 13, Portland saw PM2.5 levels 10 times higher than the limit recommended by the World Health Organization
200 μg/m3 fine particulate matter (PM2.5), daily average
100
30-day rolling average
Daily guidelines for fine particulate exposure
25
0
Jan. 2020
Feb.
March
April
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Jan. 2021
Los Angeles: 48 days
San Francisco: 24 days
Seattle: 12 days
100 μg/m3
50
25
0
July
Jan. 2021
Jan. 2020
July
Jan. 2021
July
Jan. 2021
Jan. 2020
Jan. 2020
Washington, D.C.: 4 days
Boston: 2 days
Phoenix: 2 days
100 μg/m3
50
25
0
Jan. 2021
Jan. 2021
Jan. 2021
Jan. 2020
July
Jan. 2020
July
Jan. 2020
July
Worldwide, fine-particle pollution dropped in 84 percent of countries and 65 percent of cities included in the analysis. The company measured air quality at ground-based monitoring stations in 106 countries. About half of all European cities still missed the WHO target.
The country with the worst air quality was Bangladesh, with an annual average of 77.1 micrograms per cubic meter. All but one of the world’s 50 most polluted cities are in Bangladesh, China, India and Pakistan.
WHO annual air quality guideline
120 μg/m3
Cities with more air pollution in 2020 than 2019
Higher PM2.5
in 2020
80
Delhi, India
Yosemite
Lakes
40
Cities with cleaner air in 2020
Beijing
Los Angeles
10
U.S. cities
Higher PM2.5 in 2019
0
0
10
40
80
120 μg/m3
WHO annual air quality guideline
120 μg/m3
Cities with more air pollution in 2020 than 2019
Higher PM2.5
in 2020
Delhi, India
80
Dhaka, Bangladesh
Karachi, Pakistan
Yosemite
Lakes
40
Beijing
Cities with cleaner air in 2020
Los Angeles
10
U.S. cities
Higher PM2.5 in 2019
0
0
10
40
80
120 μg/m3
WHO annual air quality guideline
120 μg/m3
Higher PM2.5
in
2020
Cities with more air pollution in 2020 than 2019
Delhi, India
80
Dhaka, Bangladesh
Karachi, Pakistan
40
Yosemite Lakes
Beijing
Cities with cleaner air in 2020
Los Angeles
10
U.S. cities
Higher PM2.5 in 2019
0
0
10
40
80
120 μg/m3
WHO annual air quality guideline
120 μg/m3
Moradabad, India
Hotan, China
Higher PM2.5 in 2020
Cities with more air pollution in 2020 than 2019
Kanpur, India
Delhi, India
80
Dhaka, Bangladesh
Gujranwala, Pakistan
Karachi, Pakistan
40
Yosemite Lakes
Beijing
Peshawar, Pakistan
Cities with cleaner air in 2020
Los Angeles
10
U.S. cities
Higher PM2.5 in 2019
0
0
10
40
80
120 μg/m3
WHO annual air quality guideline
120 μg/m3
Moradabad, India
Hotan, China
Higher PM2.5 in 2020
Cities with more air pollution in 2020 than 2019
Kanpur, India
Delhi, India
80
Dhaka, Bangladesh
Gujranwala, Pakistan
Karachi, Pakistan
40
Yosemite Lakes
Beijing
Peshawar, Pakistan
Cities with cleaner air in 2020
Los Angeles
10
U.S. cities
Higher PM2.5 in 2019
0
0
10
40
80
120 μg/m3
Fire was not just a U.S. problem. Wildfires and agricultural fires significantly contributed to air pollution in Australia, Siberia, South America, Indonesia and Africa.
During a fire, the concentration of tiny pollution particles soars and increases the risk of acute respiratory problems such as asthma attacks.
[Tracking Biden's environmental actions]
“You might get up to a thousand [parts per million] in some of these places that are just downwind of a really bad fire in California,” said Jeffrey Pierce, an associate professor at Colorado State University who studies the health effects of wildfire smoke. “But generally those only last for a few days or few weeks at most. What we don’t know is, if you get hit by really high concentrations, is it the same as if you just took that and averaged it over a long period of time?”
For example, perhaps one large fire raises the annual average in an area from 10 to 20 micrograms per cubic meter. Epidemiologists are trying to figure out whether that is more — or less — harmful to a person’s long-term health than year-round exposure to 20.
The working hypothesis is that they are the same, Pierce said.
Now that wildfires are becoming larger and more common while fossil-fuel emissions have trended downward in the United States for decades, a better question may be which type of pollution is more toxic. Unfortunately, new research from the Scripps Institution of Oceanography suggests that wildfire smoke may be significantly worse.
[2020 rivals hottest year on record, pushing Earth closer to a critical climate threshold]
