Visibility might not be good, but air quality is

Maybe you’ve noticed recently while crossing the Interstate 5 Bridge on your morning commute that you can’t see any mountains.

Or maybe you’ve just noticed in general that visibility hasn’t been great.

But that doesn’t mean the air quality in Clark County is suffering. According to the Air Quality Index, Friday’s air quality in Vancouver rated as “good,” which means air pollution is so low that there is little health risk, and everyone can go outdoors, according to the Washington Air Quality Advisory.

The Southwest Clean Air Agency focuses on two pollutants, said SWCAA Chief Engineer Paul Mairose. Those are ozone and particulate matter. The ozone levels are driven by heat, while particulate matter is more effected by fires. Last year, when Clark County was flooded with smoke from wildfires in just about every direction, the air quality tied to particulate matter suffered, Mairose said.

This year’s hot summer has also led to elevated ozone levels.

“This is a complex situation that we have,” Mairose said. “Both ozone and particulate matter contribute to visibility issues — what you’re seeing when you look out the window. When we refer to ozone, it’s smog. So when we refer to (Los Angeles), if you didn’t have fires in LA, there are still times when the mountains totally disappear, and they’re not that far away. On hot days, we get the same thing here, ozone levels go up and you lose your visibility. The last couple weeks, we’ve had these hotter temperatures, our ozone has become elevated, and that smog contributes to reduced visibility.”

From Tuesday through Friday, particulate matter levels have stayed in the good range, only slightly creeping into “moderate” on the Air Quality Advisory, which means that those with health conditions should limit outdoor time, and avoid strenuous outdoor activities.

In that same period, the ozone readings on the Air Quality Advisory have slid into moderate levels more frequently. On Aug. 8, the reading even crept into the “unhealthy for sensitive groups category.” On Friday morning, even though the skies weren’t clear, air quality remained good.

Smoke from fires to the south trickled north to the local area Thursday, Mairose said, but the “smoke is several thousand feet up.

“That’s what you’re seeing for the most part (Friday),” Mairose said. “Some of that smoke has made its way up from the south, but we have some more local fires, too, that can contribute to that. That, on top of, quote-unquote smog that we’re getting from elevated ozone both contribute to visibility impairment.”

Gravity eventually will bring the smoke down, though Mairose noted that satellites have tracked smoke plumes from fires over the course of a couple of orbits around Earth before seeing them dissipate.

“It takes a while for gravity to do it’s magic and pull that really fine stuff out of the air,” he said.

The best chance for improved visibility is lower temperatures, wind and rain. The Vancouver forecast called for a 30 and 40 percent chance of rain over a two-hour period early Saturday morning, but otherwise it’s all sun for the next week.

“Rain has an effect of washing stuff out of the air,” Mairose said. “If there’s a good system that comes in, then there’s a chance that it’s going to clear it better. If it’s kind of spotty, then probably not.”