Until now, we've been talking about a pretty crude pollution monitor -- the human anatomy. So let's take a gander at some newer, less painful, and more accurate ways to catch filthy cars at the roadside, track interstate smog, and even blame a particular particle of soot on a specific diesel engine.
a Denver freeway ramp get a "good" reading and a bit of encouragement at a drive-by carbon monoxide meter. Photos courtesy Donald Stedman, professor
of chemistry at the University of Denver.
Snagged by the smog gunIf you exit I-25 southbound at Speer Blvd. in Denver, you'll get a free profile of your car's carbon monoxide (defined) emissions, and you won't even have to slow down or pay for the test.
The smog gun shoots a beam of light (a combination of infrared and ultraviolet light) through a car's exhaust. By measuring wavelengths of light that are absorbed by the exhaust, a computer calculates the amount of carbon monoxide, particles, nitrogen oxides and hydrocarbons present within a second. When combined with license plate information taken from a video camera, the results can be used to force drivers to clean up filthy cars -- or to reward drivers of low-emissions vehicles.
"fair" reading,
and the 4 percent who are gross polluters get a "poor" reading.
The data also give a statistically useful view of which cars are hardest on the air, and it's here that some interesting statistics originate. For example, only 4 percent of the 2 million cars at the Denver roadside are what Stedman calls "gross polluters." These few cars cause about 40 percent of the carbon monoxide and hydrocarbon emissions at the test site.
Although pollution controls are more primitive on older cars, gross pollution is not simply a matter of age. Many of the worst stinkers are actually broken -- or have disconnected emissions controls. Stedman has even seen clean-burning fuel injection systems replaced on late-model cars with macho carburetors, signs that an owner is eager "to get more power for a souped-up pickup truck."
But the Denver smog gun also carries bad news for current air-pollution regulations, Stedman says. Since a few cars are causing such an outsize share of pollution, "It doesn't make any cost-effective sense to treat all cars equally, such as programs that emphasize ride-sharing, scheduled emissions testing, or reformulated gasoline." Although reformulated gasoline is intended in part to reduce evaporative emissions from the fuel tank and fuel system, Stedman notes that the picture is about as lopsided here as it is for tailpipe emissions: most cars emit almost no evaporative emissions.
With this kind of data, Stedman says the smartest thing to do is also the cheapest-- to begin a serious program of enforcing no-tampering laws and fixing dirty cars. Here's more on the economics of cleaning up dirty cars.
In the future, he plans to improve the smog gun's measurement of nitrogen oxides. He also hopes to measure benzene, a carcinogen given off by unburned gasoline, and aldehydes, pollutants given off by reformulated and oxygenated gasoline.
I'm thinking you'd like to see a mighty odd weather map --
one that tracks clouds of sulfur dioxide and ozone.
