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Interview with David Thornton, MPCA Assistant Commissioner


David Thornton is one of three Minnesota Pollution Control Agency (MPCA) Assistant Commissioners. He is responsible for overseeing the development and implementation of the agency’s air policies to improve and maintain air quality in Minnesota.  David joined the MPCA staff in 1980 as the Acid Rain Coordinator. After that, he managed air quality monitoring, data analysis, and air policy activities for many years. Most recently he has been involved with implementing federal regional haze regulations, and developing policies to help reduce air emissions, particularly mercury emissions from power plants.

Barb Thoman, acting executive director of TLC, talked with David in June about the transportation sector’s impact on air quality, the MPCA’s role in regulating air quality, and changing EPA air quality standards.

Barb: How has the role of the MPCA evolved in the last 10-20 years?

David: We’re working to communicate with people more effectively.  We’re hoping to let them know that the air they are breathing now, in 2010, is much cleaner than it was ten or twenty years ago. Not only do health scientists know more about how air pollution affects public health, but the standards have been reduced to reflect that understanding.  Based on that knowledge, we’ve done a more comprehensive job of monitoring air quality and alerting people when we feel that air quality could negatively affect their health. However, what people are hearing is that the air is bad – that they can’t play soccer today -- and because they didn’t hear that kind of warning ten years ago they assume the air quality has gotten worse.  I don’t want to give the impression that it is good enough, but we are working to get it there and it is getting better.

Barb: Is Minnesota’s air quality regulated by the state or by the Federal Environmental Protection Agency (EPA)?

David: Minnesota has a few separate and unique standards, but not many. The effort that it takes, mainly the research, to create and enforce regulations on our own isn’t something we can do with our current resources. Currently, we are relying on the federal EPA standards. That being said, EPA standards had been stagnant for years even though the Clean Air Act (CAA) requires updating as appropriate every five years. For a long time the EPA avoided doing that updating, but certain advocacy groups figured out that they could sue the EPA for noncompliance.  Now the EPA is more aggressive and staying in sync with the CAA schedule. Sometimes it feels like they just changed the standards when they are already coming out with another proposal to change it again. At some places in the country, we’re still trying to implement the first round of changes!

Barb: What are the new standards and is Minnesota in compliance?

David: Minnesota may be in violation with the revised federal standards for particulate matter (PM 2.5), or fine particles in the air, and ground-level ozone, depending on where the new standards are set. This past winter was pretty bad. When you add up all the numbers, we think we’ll become “nonattainment” -- a regulatory word meaning we don't meet the standards -- based on the existing standards for fine particles that EPA has on the books.  The EPA is developing a new standard for particulate matter, and there is no reason to believe Minnesota will fare any better under the new standard.

The EPA is also looking at new ozone standards. Ozone is formed in the atmosphere by a chemical reaction. While particulate matter is a problem year round, ozone is typically only a problem in the summer or when the weather is warm. The EPA has proposed a new standard, but only as a range. When the final standard is released in late August, we will have a better idea what it will mean for Minnesota. We’ve been very close to the current standard for a year. While we continue to make progress in reductions, the EPA has been slowly ratcheting the standard down.

If Minnesota is in violation of the new standards, we will be required to create a specific plan that can include mandated and voluntary regulation strategies.  These plans are known as State Implementation Plans and are enforceable at the state and national level.

Barb: What role does transportation play in air quality?

David: Transportation sources are a significant part of the problem we have with ozone and particulate matter. If you look at places like Chicago and Milwaukee, they can trace some of their air quality problems to emissions generated in the Twin Cities. Particulate matter is carried by the wind, typically moving from west to east.  In Minnesota, particulate matter is actually highest in Ramsey County to the east of the Twin Cities. The areas south of us add to our particulate matter problems as well. 

The city in Minnesota with the biggest ozone problem is Stillwater.  Ozone forms when nitrogen oxides and volatile organic compounds are given the opportunity to interact with sunlight. The pollution put into the air by the Twin Cities area doesn’t fully form ozone until it has reached the Stillwater area. But, again, there are places that are much worse off from an air quality standpoint than we are here in Minnesota.

Barb: In what ways does air pollution from the transportation sector impact people’s health?

David: The MPCA is currently working on a model to do risk analysis for all sources of pollution.  Mobile sources (cars, trucks, lawn mowers) and area sources contribute the most to public risk. Area source pollution is not easily regulated and is coming from locations such as homes, gas stations, bakeries, and automotive paint businesses. We do have monitors where freeways converge and there are densely populated neighborhoods since the risk is higher along high traffic roadways.  Those monitors track the nitrous oxide levels. One monitor is near the Lowry tunnel.  However, we can’t afford to do more than the minimum where monitoring is concerned. 

Non-road sources are a major issue as well.  Non-road sources are mobile sources that aren’t on the road such as boats, construction equipment, snowmobiles, weed whackers, and lawn mowers.

Although the EPA’s new standards for motor vehicle emissions will help to reduce pollution from cars and trucks, ultimately, all of our air problems are linked back to the use of fossil fuels for energy. Because of our lifestyle choices and how we get from point A to point B, we are degrading our air. The solution will require using less fossil fuel and increasing efficiency.

Barb: What is being done in Minnesota to address the fact that transportation is a leading source of air pollution?

David: Through the federal CMAQ Grant (Congestion Mitigation and Air Quality), the MPCA has retrofitted nearly every eligible state and county heavy-duty diesel truck in the metro area with emission-reducing exhaust equipment.  And we’re now starting to retrofit eligible city fire trucks, beginning with Minneapolis and Saint Paul’s fleets.

Diesel particulate can be very harmful in high concentrations.  California has even classified diesel emissions as a carcinogen.  Take a second and think about what is all around you all the time. There are school buses, garbage trucks, and semi-trucks –a lot of sources of vehicle emissions.

Our job at the MPCA is to keep this issue in front of everyone. Transportation is a major contributor to air quality issues.  MPCA is also part of the planning process for new standards.



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