Are we wasting money on clean air?

Joel Schwartz reports a study by L. C. Green and S. R. Armstrong, "Particulate Matter in Ambient Air and Mortality: Toxicologic Perspectives, published in Regulatory Toxicology and Pharmacology 38 (2003): 326-35. which found:

It remains the case that no form of ambient PM -- other than viruses, bacteria, and biochemical antigens -- has been shown, experimentally or clinically, to cause disease or death at concentrations remotely close to US ambient levels.

Of course, there are more reasons than health to want to clean up the air we breath. Aesthetics, acid rain, global warming are examples. But beware junk science among them, as well.