Did you notice a tickling feeling in your lungs during the hot weather last Saturday, or earlier this week? You wouldn't be alone — Maine's Department of Environmental Protection has been issuing a string of "moderate" air pollution forecasts recently, and warning "sensitive people" to limit outdoor exercise and exertion.
Forecast for Portland, ME: Jul 13 Moderate (Yellow)
— Portland MaineDEP (@MEair_Portland) July 12, 2014
If you take the long view, though, this cloud of pollution has a silver lining. In 2004, NASA launched the Aura satellite, whose mission is to monitor Earth's atmosphere — and air pollutants – from orbit.
One of the pollutants being monitored is nitrogen dioxide, a byproduct of fossil fuel combustion that can inflame the airways in our lungs and induce more asthma attacks. Nitrogen oxides also combine with other pollutants to form ground-level ozone pollution, another pulmonary health hazard and a major component of smog.
According to air quality monitoring stations in Portland's Deering Oaks Park, there was a significant spike in nitrogen oxides last Saturday, July 12, as well as smaller spikes on the previous Friday, and on Monday and Tuesday of this week (see chart above).
But here's some good news. Now that its satellite has been in orbit for a decade, NASA has released some striking visuals that show how things are getting better (at least, as far as this specific pollutant is concerned).
The before-and-after interactive below shows the average annual concentration of nitrogen dioxide for our region in the year 2005 (on the left) and in 2011 (on the right).
Images courtesy of NASA Goddard's Scientific Visualization Studio.
Obviously, Maine's air is relatively clean compared to our more urbanized neighbors in southern New England, and air quality improvements have been much more dramatic down there. Still, in the 2005 view, Maine's coastline is flecked with orange and red areas of high pollution levels, and much of central Maine along the I-95 corridor is colored yellow. By 2011, though, most of the state registers at the low end of the map's scale.
So what's changed in the past 10 years?
"Motor vehicles are a big emitter of nitrogen oxides collectively," says Anne Arnold, the manager of the Air Quality Planning Unit at Boston's regional Environmental Protection Agency office. Her agency estimates that roughly half of New England's nitrogen oxide pollution comes from cars and trucks.
You can see evidence of this in the maps above: the worst pollution is near major highways like the Maine Turnpike, and in traffic-choked urban areas like greater Boston.
In 2004, though, the EPA established new rules for cars, trucks, and sport utility vehicles that focused on tailpipe emissions. "New cars, including SUVs and pickup trucks, are meeting more stringent emissions standards," says Arnold. "New vehicles are 77% to 95% cleaner than they were before 2004."
Diesel vehicles have also been subject to new regulations. Remember the clouds of black smoke that used to pour from buses and trucks at every stoplight? The EPA categorizes that as "fine particulate" pollution, and rules that took effect for model year 2007 required new diesel vehicles to reduce it by 95%.
Of course, the cleanest engine is one that isn't running, and federal statistics also indicate that Mainers (like people throughout the United States) are also driving less than they used to.
Arnold also points out that the EPA also has new rules that require power plants to clean up their smokestacks. That's made a big difference upwind from us in the Midwest, but it's made less of a local impact here in New England, where we have fewer coal-burning power plants.
And here's some additional good news: the recent rain seems to be helping to keep the air cleaner than it was earlier this week. To keep up to date with daily air quality forecasts from the Maine DEP, follow their Twitter feeds: @MEair_Portland, @MEair_Lewiston, @MEair_Bangor and @MEair_acadia.