Air pollution exists in two physical forms: as a gas (molecules) and as particles (usually heterogeneous agglomerations of huge numbers of molecules stuck together). Particles in the air are also called aerosols. Depending upon their size (really their aerodynamic behavior), their abundance and their composition, they can affect our lungs, vegetation or visibility. They can come from anywhere. Sometimes they are formed “in place” by secondary chemical reactions of precursor pollutants. Photochemical oxidant pollution (“smog”) is of this type. Sometimes it is of natural origin and can be transported over huge distances. Dust storms in Asia can wind up as particulates over the US continent. And sometimes they are of local or regional origin, for example, sent up the stacks of power plants. In fact a new study from NASA (the National Aeronautical and Space Agency) suggests most surface particulates in US air are local:
Researchers using an innovative global aerosol tracking model have for the first time produced a global estimate of sources and movements of aerosols near the ground where they can affect human health and run afoul of environmental regulations. Previously, researchers studying aerosols moving between continents focused primarily on tracking a single type of aerosol, such as dust or black carbon, or measuring their quantities throughout the atmosphere. This left gaps in understanding where ground-level particulate pollution comes from.
[Mian Chin, an atmospheric scientist at NASA's Goddard Space Flight Center, Greenbelt, Md.] and colleagues estimate that between 65-70 percent of surface particulate matter in the eastern U.S. originates from regional pollution aerosols from fuel combustion in North America. The report was in the Nov. 1 edition of the European Geosciences Union’s Atmospheric Chemistry and Physics.
They also found that 30-40 percent of fine particulates in the western U.S. come from local pollution sources. The model results estimated that just 2-6 percent of U.S. surface fine particulates come from fuel combustion particles emitted outside of North America, including Asia and Europe. About 50 percent of surface fine particulate matter in the western U.S. stems from a natural source: dust transported from Asia or from local deserts and organic aerosols from vegetation. (NASA)
Here’s a pic of haze over the eastern US (Cape Cod, Massachusetts is that thing that looks like a flexed arm at the upper right):
The lesson here is pretty clear. If you want to clear the air (and your lungs), you’ll get the biggest effect from controlling your local and regional air pollution sources, mainly vehicles and large stationary sources like power plants.
We can’t blame anyone on the other side of the planet for this. But you knew that, didn’t you? I mean, really. In your heart you did know that, didn’t you?