Total emissions of sulfur dioxide rose about 23 percent, from 154 thousand tons in 1990 to 190 thousand tons in 2000. Monitored levels are below the legal limit and are unlikely to exceed it unless sulfur emissions from coal-burning power plants increase dramatically. Increased sulfur emissions will reduce visibility and may hasten acidification in Minnesota's lakes.

Nitrogen oxide emissions increased about 26 percent, from 426 thousand tons to 533 thousand tons. The increase is likely due to several factors: more people driving more miles per person; growth in energy use and therefore an increase in emissions from power plants; and increased emissions from taconite mining (part of which may reflect more accurate measurement). Although nitrogen oxide emissions may continue to rise because of increased travel and fuel use, it is unlikely that these increases will violate the legal standard. Nitrogen oxides contribute to the formation of ozone and smog on hot summer days.

As with both sulfur dioxide and nitrogen oxides, emissions of carbon monoxide showed a net increase for the decade, from 1,990 thousand tons in 1990 to 2,105 thousand tons by 2000. This net increase of three percent is likely due to increased auto travel, which appears to be outpacing any improvements in vehicle emissions or fuel efficiency. Carbon monoxide is a colorless, odorless, highly toxic gas emitted from automobiles. In small amounts it can impair alertness, cause fatigue and headaches. In large amounts it can kill. People with heart conditions and respiratory ailments are especially susceptible.

Minnesota ranks 20th in carbon monoxide emissions. Monitored levels of carbon monoxide have dropped five percent across the country despite significant growth in vehicle miles traveled.

The Minnesota Pollution Control Agency's regulation of large industrial sources of air pollution has contributed to large improvements in air quality in the last two decades. However, hundreds of chemicals, including most toxic chemicals and greenhouse gases, such as carbon dioxide, remain unregulated and pose significant challenges for Minnesotans' long-term health. Since many of these pollutants come from cars, trucks, buses, airplanes and power plants, protection of air quality involves reducing fuel and energy consumption, adopting cleaner fuels and shifting to other technologies that reduce air pollution, such as fuel cells.

• Energy efficiency of the economy
• Freeway congestion
• Energy use per person
• Renewable energy sources
• Vehicle miles
• Urban air pollution
• Water quality in lakes and rivers
• Nitrate in ground water
• Changes in land use

• Energy use by fuel type (Minnesota Department of Commerce, www.commerce.state.mn.us/pages/EnergyMain.htm)
• Estimated annual carbon dioxide emissions (Minnesota Pollution Control Agency, www.pca.state.mn.us)
• Amount of solid waste by disposal method, such as recycled, composted and incinerated: (Minnesota Office of Environmental Assistance, www.moea.state.mn.us)