Bus-ted

"32 PASSENGERS. 1 tailpipe. Riding the bus reduces pollution."

So says the ad, dreamt up by the Washington State Department of Transportation, that began appearing on the sides of Metro buses last October. It sounds so comforting if you're a bus riderand so guilt-inducing if you're a single-occupancy motorist.

It's also a bit misleading.

The truth is that Metro buses pour out much more air pollution than your average carand much, much more than new cars. According to numbers from the Environmental Protection Agency and the Union of Concerned Scientists (an environmental advocacy group based in Cambridge, Mass.), a modern diesel transit bus puts out over half a ton of smog-creating chemicals every year. Mile for mile, the bus pollutes nearly 60 times more than a new passenger car like a Ford Taurus or a Nissan Sentra. Think about that the next time you're sanctimoniously looking down from your perch on the 72 express at the soccer mom driving alone in the next lane.

The numbers are even worse for some of the older buses in Metro's fleet (you knowthe ones still bearing the shameful orange-brown-and-white color scheme). For example, Metro still uses 157 German-built MAN diesel buses that date from the mid-'80s. According to estimates done for Seattle Weekly by an EPA official, each of those buses coughs up roughly two and a half tons of smog pollutants every year. Even if all 32 passengers on the MAN bus got out and drove 32 new Ford Explorers around the clock all year, they still wouldn't come close to polluting that much.

SMOG-CREATING chemicals such as nitrogen oxides and hydrocarbons can damage the lungs, but they don't actually represent the worst pollutant associated with buses. An even bigger threat is the soot that all diesel-powered vehicles emit. If you think that cloud of exhaust fumes hanging over your Third Avenue bus stop seems a tad unhealthy, you're right.

The stuff coming out of diesel tailpipes "is much more toxic than gasoline exhaust at existing levels," according to the Washington State Department of Ecology. Says DOE scientist Matt Kadlec: DPM (or "diesel particulate matter") is "the single most risky hazardous air pollutant of anything we've studied." "A single gram of diesel soot has 90 square meters of surface area," explains DOE spokesperson Leslie Thorpe. "Toxins stick to it. Then those particles get inhaled into the lungs." Another DOE spokesperson, Larry Altose, adds, "You'll find some researchers who say they're not sure there is a safe standard for it. It's a major concern."

Even while federal regulators have been aggressively curtailing car emissions for the last couple decades, there has been little regulation of diesel until recently. Says Patricia Monahan of the Union of Concerned Scientists, "In terms of cancer risk, a bus is equal to 279 cars"not such a good ad slogan for Metro.

Of course, transit buses are by no means the only, or even the primary, source of diesel exhaust; the foul blue smoke is pumped out by everything from bulldozers to container ships to 18-wheelers. And as Metro's vehicle manager Jim Boon notes: "The buses in our fleet are extremely clean compared to trucks. And there are so many more of those [trucks] that the numbers are staggering." But then, it's not like most commuters are choosing between driving a car and a Mack tractor-trailer to work.

THE GOOD NEWS is that Metro is taking major steps to clean up its busesenough that the King County agency may even soon live up to the promise of that DOT ad.

Metro has already started using low- sulfur diesel fuel for all its buses; the cleaner fuel reduces soot emissions by about 20 percent, according to the Puget Sound Clean Air Agency. Metro is also investing in new filters that reduce tailpipe emissions even more radically, up to 90 percent. Metro's Boon says he'll be installing these new filters on nearly 400 of Metro's 1,120 diesel coaches. "That'll make our buses some of the cleanest in the country," he notes. The MAN buses from the mid-'80s are going to be retired at the end of this year, and Metro is also preparing to replace its 215 tunnel buseswhich run on diesel outside the downtown bus tunnelwith new hybrid diesel buses, much like the Toyota Prius or Honda Insight, that are partly powered by electricity.

The rest of Metro's current diesel fleet will be replaced starting in 2007, Boon says, "with buses using latest-technology clean diesel." At that point, at least, it really would be much better if the 32 Explorer drivers climbed back on the bus. Now if they could just do something about the toxic cologne on the guy sitting next to you. . . .

mfefer@seattleweekly.com