The northwestern United States has literally become an air pollution hotspot.
The air quality in states from Nevada to Montana is worse than it was 30 years ago on the days with the most extreme air pollution. Larger and more frequent forest fires spewing particulate matter into the sky are largely to blame, researchers report on July 16 in Proceedings of the National Academy of Sciences .
By contrast, the rest of the country has observed similar trends over the past three decades with similar smog and fog. Laws such as the Clean Air Act, which requires air quality standards and the regulation of particulate emissions from vehicles and factories, make a difference, says study co-author Daniel Jaffe, atmospheric scientist at the University of Washington at Bothell.
But the increase in lung compaction particles from forest fires shows how the effects of climate change, some of which are fueling the intensifying fires, can counteract these gains, says Jaffe.
Wildfire smoke is filled with fine particles, tiny particles or droplets that can be inhaled into the lungs, causing respiratory problems. Children, the elderly, and people with asthma are the most vulnerable, but communities near forest fires can sometimes experience levels of pollutants that are not safe for someone who is out for a long time. "When we start thinking about people's health, episodic events play a big role," says Gannet Hallar, an atmospheric scientist at the University of Utah in Salt Lake City who did not attend the study
airborne pollutants (less than 2.5 microns wide or about 3 percent of the width of a human hair) have also been associated with an increased risk of chronic diseases such as heart disease and diabetes ( SN: 9/30/1
Tracking the wider impact of forest fires on air pollution can be difficult as the fires are intermittent and spotty, says Jaffe, who conducted the study with Crystal McClure at the University of Washington at Bothell. "Most forest fires have no impact on air quality, but on some of the worst days." And the fires can hit a church hard, but leave neighboring cities relatively untouched.
From 1988 to 2016, Jaffe and McClure studied daily measurements of particulate matter at more than 100 rural monitoring sites across the country. In most parts of the country, the data has been a clean air success story over time – but not in the northwest, an area hit hard by forest fires every summer.
Where air pollution has got better or worse
This map shows the change of particulate matter (less than 2.5 microns) from 1988 to 2016 on the worst air days. In most parts of the country, this type of air pollution has decreased. But in the northwest forest fires make the bad air quality days worse than before.
The team has performed similar calculations for levels of some specific pollutants – particles carbon, a trademark Particulate carbon content had increased over time in the northwest, but sulfate levels did not increase, leading to the conclusion that forest fires mainly drive air pollution in the western United States, rather than industrial activity
Forest fires did not make air pollution worse on an average day in the northwest, the team found.Most often the air quality is okay – forest fires could only have an impact Air quality on the bad days, when the air pollutants are particularly high, is in Over time, as the analysis shows t. Especially bad days were in summer, when forest fires at th are Eir peak. In the north-west, on the few days with the worst air quality, particulate matter levels have increased by an average of 0.21 micrograms per cubic meter per year, although there is considerable local variability in this number
The picture of air quality in the countryside has improved "We have to do harder work now," says Jenny Hand, an atmospheric scientist at Colorado State University in Fort Collins who was not part of the study. These challenges include finding out how to prevent and mitigate these more uncontrollable sources of air pollution that can not be regulated like emissions from human sources, she says.