Wednesday, August 20, 2003

Just how clean are today’s cars and light trucks?Have we really made significant strides toward ridding the air of vehicle-induced pollution over the past three decades? The answer is a resounding “yes,” and to prove it we need to put the issue in perspective by making a real-world comparison between two real vehicles, one from the past and one from the present.

To do so, let’s grab the keys to a fully restored 1967 Corvette and a brand-new 2004 Corvette and drive them enough miles to equal a specific amount of emissions output. Put another way; how many miles does the 2004 Corvette have to go to chalk up the amount of pollutants the 1967 belches in a one-way trip from, say, the District to Baltimore — exactly 42.32 miles from the Capitol building to the Inner Harbor. Place your bets, please.

The two major pollutants in gasoline are volatile organic compounds (VOCs) and oxides of nitrogen (NOx). The other major gas streaming out of exhausts is carbon dioxide, a greenhouse gas. We’re not going to count it in this exercise because it really isn’t a “pollutant” (we exhale CO2 with every breath, so we’re just as guilty as the machine.)

In 1967 federal pollution standards for VOCs allowed a maximum of 10.6 grams per mile. NOx standards allowed a maximum of 4.1 grams per mile. Driving the 1967 Corvette from Washington to Baltimore would, therefore, produce 10.6 times 42.32 equals 448.59 grams of VOCs, which is nearly 1 pound. As for NOx, the 1967 would produce 4.1 times 42.32 equals 173.51 grams, or 0.38 pounds. Hmmmm.

Now it’s time to drive the 2004 Corvette. Its engine is allowed only .075 grams per mile of VOCs and .05 grams per mile of NOx (that’s a reduction of 99.29 percent and 98.78 percent, respectively) so we’re going to have to drive the car considerably farther.

How far? It doesn’t take a mathematician to figure out we’re going to have to drive the new Corvette 5,981 miles to equal the VOC figure; a drive equal to a trip from the Capitol building to Los Angeles International Airport and back (5,367 miles) plus a quick side-trip to New York’s Central Park and back. As for NOx, we only (only?) have to drive the car 3,470 miles to equal the numbers of the old Corvette’s trip to Baltimore. Therefore, we could stop driving on the return trip from Los Angeles around St. Louis.

And what about those gas-guzzling SUVs? The fact that they are gas-guzzlers doesn’t matter, because pollution is measured in grams per mile. Therefore, SUV engines have to be clean enough to meet the federal standards (for 2004 the VOC standard is the same as for passenger cars and the NOx standard is 0.07, just 0.02 more than for cars) even though they are burning more fuel per mile. The plain truth of the matter is that we can drive a 2004 Chevrolet Tahoe the same number of miles as the new Corvette before we equal the 1967 Corvette’s VOCs. It can go for 2,478 miles before equaling the NOx, and that’s not too shabby.

This little exercise proves just how much cleaner today’s cars are (141 times cleaner, actually) than those of the 1960s and earlier. The fact is, automobiles really did pollute our atmosphere throughout most of the 20th century, but the combination of regulation and creativity on the part of manufacturers has largely eliminated the problem.