Cool summer = less pollution

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August 16, 2004 // UPDATED 3:24 pm - April 25, 2007
By: Scott Russell
Scott Russell

Mellow temps and chilly breezes mean cleaner Downtown air

If you're disappointed in this year's less-than-hot-and-sunny weather, consider the silver lining: the air is cleaner.

That fact may have gone unnoticed because air-quality issues make news when there's a problem, not when things are going well. The Minnesota Pollution Control Agency (MPCA) hasn't issued an air quality warning since March 25.

"This has been an exceptionally good summer, probably the best in air quality in the last five or six years," said Rick Strassman, supervisor of the MPCA's air-quality monitoring unit.

By this time last summer, MPCA had issued three air-quality alerts for ground-level ozone, more commonly known as smog. It has issued no ozone alerts this year. (So far, the 2004 alerts such as the one March 25 have been for excessive fine-particle levels.)

The cool, cloudy weather patterns create a double benefit for Downtown and the metro area, Strassman said. First, ozone is made when tailpipe pollutants mix in heat and sunshine. Less heat and sunshine means less smog.

Second, the cooler air means the prevailing winds are from the north and northwest, he said. That means Minneapolis is getting clean Canadian air, unpolluted by major industry. When Minneapolis gets day after day of hot, southerly winds, the area gets ozone pollution from Chicago or St. Louis.

Strassman said people might think air quality is deteriorating because they are stuck in traffic longer or because they see the air quality alerts in the news. However, the state didn't issue air quality alerts five years ago -- not because the air was cleaner, but because it didn't have the technology to do it.

"Air quality is not getting worse," he said. "It is a perception I fight daily."

Major improvement ahead

Cooler weather and favorable winds are matters of chance. How well is the Twin Cities cleaning up its own pollution?

The good news is that industrial polluters will be or are polluting less.

Consider Xcel Energy's planned $1 billion upgrade of its North Minneapolis Riverside plant and two other Twin Cities facilities. Bill Anderson, Minneapolis deputy director of environmental operations, called it "the single most important air-quality improvement in a generation."

Xcel will convert the Riverside plant from coal to "combined cycle" natural gas by 2009, its Web page said. Researcher Carl Nelson, writing for the city, estimated the Minneapolis plant conversion alone would save a net $53 million on health care annually.

Nelson's study, which MPCA cites, looked only at the reduced fine-particle levels. Fine-particle pollution contributes to chronic bronchitis, respiratory hospital admissions, asthma attacks, emergency room visits and even premature deaths, Nelson wrote.

By the ton, the pollution reductions are staggering.

Xcel estimates its Minneapolis conversion would reduce sulfur dioxide by 12,000 tons a year by 2009. That is equivalent to more than 60 percent of all Hennepin County sulfur dioxide production in 1999. The conversion would eliminate 13,100 tons of nitrogen oxides a year, according to Xcel data, or 20 percent of all 1999 county emissions.

In addition, particle pollution would drop 540 tons a year, or 3 percent of 1999 totals, Xcel and MPCA data said.

Another major pollution reduction on the horizon is stage-one vapor recovery. It prevents fumes from escaping while gas stations refuel their tanks.

Jeff Buss, MPCA's mobile sources policy analyst, said by the end of 2005, the state would require all stations in the seven-county area to have stage-one vapor recovery.

Half the gas stations in the seven-county area already upgraded, said MPCA's Mary Jean Fenske. When the other 50 percent switches to the new technology, it would eliminate 3,000 tons of volatile organic compounds from the atmosphere, which contributes to ozone.

To put 3,000 tons in perspective, Fenske said Rosemount's Flint Hills refinery releases 1,152 tons of volatile organic compounds a year. Therefore, stage-one vapor recovery would eliminate the equivalent of nearly three Flint Hills plants -- and Flint Hills is the nation's largest heavy-crude processing facility, according to its Web site.

More broadly, as Minneapolis becomes

less industrial and industrial technology improves, the amount of industrial pollution is falling. Between 1998 and 2001, Minneapolis industries cut their air toxin emissions by 57 percent -- from 795,000 pounds to 344,000 pounds -- according to a toxic release inventory provided by the city's environmental operations division.

All that driving

Pollution is becoming less about industrial smokestacks and more about myriad exhaust pipes.

MPCA documents report that facilities it regulates generate less than a third of Minnesota's air pollution while approximately 50 percent is from mobile sources including cars, trucks, planes and off-road equipment.

And of course, locals are driving more cars more miles.

A Metropolitan Council report said between 1975 and 2000, vehicle miles traveled increased 140 percent while population grew 37 percent.

Still, even relentless drivers can't outweigh industrial air-quality gains. In fact, pollution from driving is going down, too.

Better car technology and gas formulas are cutting pollution. For example, carbon monoxide levels -- which triggered the local vehicle-inspection programs of the 1990s -- continue to drop.

Dave Thornton, MPCA's manager of policy and planning on air issues, pronounced the carbon-monoxide problem solved. "We don't expect it to come back as a problem in the future," he said.

Said Strassman, "even though vehicle miles driven have exploded, the concentration of pollutants that are primarily emitted by vehicles has been trending downward."

Buss said exhaust pollution should drop for the next 10 to 15 years despite driving increases.

The oft-beleaguered bus system also deserves some credit.

Buss said Metro Transit buses began phasing in ultra-low sulfur diesel fuel in late July, more than two years ahead of government mandates. The fleet uses approximately nine million gallons of diesel a year. It would finish the changeover next year.

The ultra-low-sulfur diesel will take tons more pollution out of the air each year: 3.5 tons of volatile organic compounds and 10 tons of carbon monoxide, and it will virtually eliminate sulfur dioxide.

Still, compared to Minnesota's overall pollution problem, the impact is tiny, Buss said.

Metro Transit's purchasing power could encourage other diesel buyers to switch to ultra-low-sulfur fuel ahead of schedule.

"We needed someone to purchase large quantities to make it cost-effective to send it by pipeline," Buss said. "Our thinking was, if we could move that much fuel through a Metro Transit contract, it would then become available to others."