From the NY Times:
It’s another price of living in New York: call it the dirt tax.
The dirt tax appears in cleaning costs, replacement costs and even the inability of New York homeowners to consider certain finishes and fabrics because they’re just not practical.
Not in a city where schmutz — the preferred New York term for the black gritty material — accumulates on every surface.
White rugs and sofas can become filthy anywhere. But experts (who include anyone who has ever dusted, vacuumed or swabbed in the five boroughs) say New York City’s dirt level is highly unusual.
The culprit is soot, said Richard Kassel, an air pollution expert with the nonprofit Natural Resources Defense Council.
In one study cited by Mr. Kassel, soot in one stretch of Midtown Manhattan was found to contain 52 percent diesel exhaust, mostly from trucks, buses and construction vehicles. The other 48 percent was a mix of everything from ground-up car tires to sea salt, he said.