The partner and I were up in the Methow Valley for a(n AMAZING!) wedding a few days ago. We had some time to spare, so we decided to wind our way slowly over the North Cascade Highway, aka Washington “SR-20”. One of the most scenic highways in the nation, it offers 400 miles of byways along the gorgeous rivers, ridges, and forests of the Cascades. It’s well-traveled, but rarely is there much traffic– heck, it’s in the middle of a national forest! So it was a bit of a let down when the breathtaking vistas that started our journey down in Winthrop slowly faded away into a deep white smog.
But I was prepared! We expected a bit of plumage (usage?) from the nearby Wolverine and Goode fires, so before we left, I packed up one of the lab’s DustTraks– a device that measures respirable particulate matter (PM2.5)– and an extra battery. I pulled it out somewhere around Mazama, WA (see map with estimate below), about 40 miles before Diablo Lake and the first real corridor of deep walls in the pass. Prepared? Perhaps. Expecting concentrations on par with Beijing in the Winter? Not a chance.
Let’s see some data!
Note that the DustTrak is corrected using a standard forest fire correction factor (0.59, or 1/1.7) published by McNamara, et. al. in 2011. You may notice that our window of data collection is just a blip on this chart. That’s because the local reference monitors record
(and broadcast) in hour averages, but our car ride was only ~ 45 minutes. I just wanted to show some context from nearby sensor nodes. It does bring up an interesting point, though, that the hourly averages from those reference monitors are NOWHERE near the concentrations measured at the height of the pass. And who would expect them to be? The closest reference monitors are many miles away, and well outside of the local topography (i.e. the narrow valley corridors). It certainly is worth noting that the population density in this area is quite low, so placing a monitor along the pass is admittedly not the best use of limited gov. funds. Still, it’s a good example of a major weakness (perhaps funding related!) in our nation’s air quality monitoring network: its sensor nodes are few and far between. Around the time we hit the top (of the pass), ambient concentrations had breached 300 ug/m3. That’s nearly 9x the EPA 24-hour standard of 35 ug/m3, which is already a bit lenient– even Oakland violates it only 2-3 times per year.
Air pollution levels matter. Especially at these levels. Millions of folks die every year from exposures to PM2.5 that are likely far lower than what we witnessed in the Cascades. While I’ve been quick to grasp the importance of forest fires as a source of occupational exposures in fire fighters (yikes!), I don’t think it ever hit me how far their smoke plumes could travel and how much of an impact they could have on the general population. This trip was a good ol’ kick in the pants, and it’ll stick with me for a while.