A new analysis of existing air pollution data indicates choking wildfire smoke, which blocked the sun across Washington earlier this month, presented the most hazardous breathing conditions for Spokane residents since at least 1992.
The Spokane Clean Air Agency had reported that poor air quality beginning Sept. 12 and lasting nearly a week was the worst recorded since a healthy standard for microscopic particles in the air was adopted in the late 1990s. Now, a look at readings of blowing dust and smoke prior to that date indicates the prolonged period of soot-filled skies ranks among the worst conditions going back to the late 1980s.
The challenge of comparing different eras of air quality comes from a changing understanding of what is potentially harmful and advances in technology monitoring pollutants in the air. Through the late 1980s and most of the ’90s, air quality experts monitored only particulates 10 micrometers or smaller in size with available equipment. In 1997, a new standard for smaller particles, 2.5 micrometers in diameter or smaller, was established.
Those are often created by combustion and capable of causing more damage to the circulatory system. New technology allowed monitors to observe the amount of these smaller particles, which are more hazardous to human health.
“The small particles get way deeper in the lungs,” said Ron Edgar, a retired air quality supervisor who worked in Spokane from 1977 through 2015. “The larger particles do get filtered out, to a certain extent. But if it gets to be so much of it, the body still can’t handle it, and so it does have a health impact.”
The air quality index, a color-coded measure that is now a late-summer mainstay for residents of the Inland Northwest, is a consistent measuring stick for all pollutants and their potential effects on human health.
The agency took readings from its equipment dating back to 1988 with equipment capable of capturing the coarser air particles, and then normalized those concentrations with today’s understanding of what is healthy within the index.
That analysis revealed more than three dozen days during the past 30 years in which the air outside was considered to be unhealthy due to smoke and dust for anyone, not just those with existing breathing problems. And while this September’s weeklong period of misery had several of the worst days recorded, a dust storm that kicked up in September 1992 actually posted a worse air quality average over a 24-hour period.
High winds kicked up in the afternoon on Sept. 12, 1992, sending a dust plume east of the Cascades 6,000 feet in the air, according to an account on the front page of the next day’s Spokesman-Review. Visibility on Highway 2 near Waterville that afternoon was “zero,” according to the paper, and a 44-year-old man was struck and killed by another car when he left his vehicle to assess the damage from another crash.
But by the next morning, the dust had settled and skies were sunny. That’s a distinction between the temporary dust storms that can cause extreme breathing problems for short periods of time and the settling wildfire smoke of earlier this month, Edgar said.
“The thing about dust storms is, they’re going to be worse, and average out high,” Edgar said. “But they’re very short term, and it’s much easier for people to get out of them.”
The analysis is limited to the pollution caused by dust and smoke particles, and does not include readings of hazardous air due to carbon monoxide that was seen primarily in the 1970s and 1980s, said Lisa Woodard, public information officer for the agency. Such pollution was common before technological advances to car engines that limited the amount of gases belched into the skies during car trips.
The agency could match those values to the air quality index to compare days of hazardous air, but didn’t do so for the current analysis.
It would also be difficult to compare this year’s wildfire smoke to the air above Spokane following the 1980 eruption of Mount St. Helens. At that time, air quality observers were using a standard called total suspended particles that captured even larger pollutants than those at 10 micrometers across.
“There were just some obscenely high numbers when the ash started to fall,” Edgar said. “I don’t know that we ever got a good breakdown of size ranges in those particles.
“The biggest problem was, there was so much particulate in the air, when it first was falling, that we couldn’t even keep the monitors running. They’d get clogged.”
Of the 40 unhealthy or worse days identified by the agency since 1988, more than half were due to wildfire smoke. Often, those smoky days ran back-to-back in Spokane, unlike the periods of blowing dust more common in the 1990s.
Why so bad this year?
But the weeklong dangerous air quality experienced this year was an anomaly even among the periods of late-summer smokiness that have plagued Spokane for four of the past six years, both in severity and in length.
Several meteorological factors contributed to the effect, said Ranil Dhammapala, an atmospheric scientist with the Washington Department of Ecology and contributor to a Washington smoke blog that attracted 2.5 million visitors during the weeklong smoke event. That included a strong wind from the east that first carried smoke from fires burning in the region out over the Pacific Ocean over Labor Day weekend.
“The east winds, they’re not uncommon, but they’re not super frequent, either,” Dhammapala said. “One of the unusual things was the strength of these east winds.”
They also lasted for several days, allowing what bloggers described as “a super massive plume” just off the coast.
By the end of the week, the winds shifted slowly, and the smoke that accumulated began to “leak” across Washington, Dhammapala said.
The smoke arrived Sept. 12, and the following two days were the second- and third-worst days of air quality on the index since 1988, according to the Clean Air Agency data.
The smoke was so thick it drove daytime temperatures down, thwarting the daytime warming that would have kicked up the very winds capable of pushing the smoke out, Dhammapala said.
Instead, the smoke sat in the valleys for days, until a new weather system brought rains and winds that finally pushed the smoke out of the area.
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