These Great Lakes states comprise one of the most seriously polluted regions in the nation. Detroit-Warren-Flint, MI remained ranked as the 6^th most polluted city in the nation for year-round particle pollution levels, while also ranking 15^th most polluted for short-term levels. Cleveland-Akron-Elyria, OH ranked 8^th most polluted by year-round particles, 10^th most polluted by short-term particles and 16^th for ozone pollution. The Cincinnati-Middletown-Wilmington, OH-KY-IN metropolitan area also ranked on all three lists of most polluted cities, ranking 13^th worst for year-round particle pollution and 20^th for both short-term particle pollution and ozone. Chicago-Naperville-Michigan City, IL-IN-WI ranked 11^th most polluted by year-round particle pollution and 25^th for short-term levels.

Columbus-Marion-Chillicothe, OH ranked as the 18^th city most polluted by ozone, while Youngstown-Warren-East Liverpool, OH-PA tied Cincinnati for 20^th most ozone-polluted. Illinois counties are also part of the St. Louis-St. Charles-Farmington, MO-IL metro area that ranked 24^th most ozone-polluted. South Bend-Mishawaka, IN-MI tied Huntington-Ashland, WV-KY-OH for 25^th on that list.

The Weirton-Steubenville, WV-OH area ranked on both lists of cities polluted by particle pollution, landing at 12^th most polluted year-round and at 20^th for short-term levels. Canton-Massillon, OH tied for 18^th while Indianapolis-Anderson-Columbus, IN ranked 24^th on the list of the cities most polluted by year-round pollution. The Indiana counties share the 18^th place rank of Louisville-Elizabethtown-Scottsburg, KY-IN on the list of cities most polluted by short-term particle levels and 25^th on the list of those most polluted by yearround levels.

Illinois
Chicago-Naperville-Michigan City, IL-IN-WI remained on both lists for cities with the most particle pollution, but improved its ozone levels sufficiently to drop off the list of most polluted cities for that pollutant, dropping to 31^st from 22^nd most polluted. However, its continued ranking on the particle lists, at 11^th for yearround and 25^th for short-term, signals a continuing air quality problem. Madison County tied for 17^th among the most polluted counties for year-round particle pollution.

The good news is that several cities earned a place on the lists of cleanest cities. Springfield made the list for cleanest for both ozone and short-term particle pollution, while Champaign-Urbana and Decatur also made the list for cleanest for short-term particle levels. Nine Illinois counties are on the list of cleanest counties for short-term particle pollution, while two were on the cleanest list for ozone. One of those was Sangamon County, which ranked on both the short-term and ozone cleanest counties list.

Indiana
Indianapolis-Anderson-Columbus ranked again among the cities most polluted by year-round particle pollution. Indiana counties next to major cities in other states also were ranked with those cities as among the most polluted in the nation. As part of the Chicago-Naperville-Michigan City, IL-IN-WI, the Cincinnati-Middletown-Wilmington, OH-KY-IN and the Louisville-Elizabethtown-Scottsburg, KY-IN metropolitan areas, the neighboring Indiana communities are also at risk from the ozone and particle pollution in those cities.

Several Indiana counties improved their air quality, most notably Elkhart and Vanderburgh, which rose from a failing grade to a passing grade in their yearround particle pollution levels.

Michigan
Detroit’s position continues high on the lists of the most polluted cities for yearround and short-term particle pollution. Detroit’s number of days with spikes in short-term particle pollution actually dropped compared to 2005. Good news for the Detroit metropolitan area came also from its lower levels of ozone pollution. Although still very unhealthy, it improved from being ranked as 20^th most ozonepolluted in 2005 to 35^th in the nation. The Michigan suburbs of South Bend-Mishawaka, IN-MI were included in that metropolitan area’s ranking as tied for 25^th most ozone-polluted city. Wayne County ranked 8^th among counties most polluted by year-round particle levels and 19^th for short-term particle levels.

For good news, the cities of Lansing-East Lansing-Owosso and Saginaw-Bay City-Saginaw Township North each earned a place on the list of cleanest cities for short-term exposure to particle pollution. Four counties are also on the list of cleanest counties for short-term particle levels. Some Michigan counties improved in their air quality. Most notably, Monroe County improved to passing the year-round particle grade from failing it previously. Clinton County improved to a D in ozone from an F; Allegan County improved to a D in short-term particle pollution from an F.

Minnesota
Minnesota has some of the cleanest air quality in the region. Minneapolis-St. Paul-St.Cloud, MN-WI is the largest city on any of the lists of cities ranked cleanest for short-term particle levels. Rochester joined the Twin Cities on that list. Duluth, MNWI also earned a place on the other two lists of 25 cleanest cities: for year-round particle pollution as well as for ozone. Several Minnesota counties are also on the lists of cleanest counties in the nation for year-round particle and ozone pollution.

Ohio
Ohio has serious and widespread air pollution problems. The metropolitan Cleveland-Akron-Elyria and Cincinnati-Middletown-Wilmington, OH-KY-IN areas rank on all three lists of most polluted cities. Weirton-Steubenville, WV-OH continues on both particle pollution lists, ranking at 20^th on the short-term list and 12^th on the year-round particle list. Canton-Massillon tied for 18^th on the list of cities polluted by year-round particle exposure. Columbus-Marion-Chillicothe and Youngstown-Warren-East Liverpool, OH-PA ranked 18^th and tied for 20^th respectively on the list of most ozone-polluted cities.

Three Ohio counties—Cuyahoga, Hamilton and Jefferson—ranked among the counties most polluted by both short- and long-term particle levels, while Stark County was on the list of most polluted year-round.

Good news: Three counties appeared on the list of cleanest counties for shortterm particle pollution—Athens, Lorain and Preble. Several other counties cleaned up their air enough to improve their grades. Notably, Lawrence, Lucas, Mahoning and Scioto each improved from failing to passing for year-round pollution levels. Scioto County also improved its short-term particle pollution grade to a C from an F, as did Stark County; while Trumbull County brought its F up to a D.

Wisconsin
Kenosha County, the Wisconsin suburb of Chicago, joins that metropolitan area’s rank among the most polluted metropolitan areas in the United States on all three lists. The Wisconsin suburban counties for Minneapolis-St. Paul joined in that metropolitan area’s ranking among the cleanest U.S. cities for short-term levels of  particle pollution. The Wisconsin suburbs of Duluth added to that city’s listing on the cleanest cities for ozone and year-round particle pollution. In addition, Wausau-Merrill earned a place on the list for cleanest cities for ozone levels. Two counties saw big improvements this year in their individual grades. Brown County cleaned up its ozone pollution enough to raise its grade to a C from an F, while Milwaukee County raised its grade for short-term particle pollution to a C from an F.

Region 6: Arkansas, Louisiana, New Mexico, Oklahoma, Texas

In these Southwestern states, the biggest air pollution problem is ozone. Four cities rank on the list of the highest levels of ozone pollution in the nation. Houston-Baytown-Huntsville, TX remained anchored in 6^th place and Dallas-Fort Worth, TX at 8^th. But Baton Rouge-Pierre Part, LA and San Antonio, TX emerged for the first time on the list of most ozone-polluted cities, with Baton Rouge tied for 20^th and San Antonio at 23^rd. Several cities in the region rank among the cleanest. Most notable are Santa Fe-Espanola, NM and Farmington, NM, which continued their rank as the 2^nd and 7^th cleanest cities in the United States for year-round particle levels, as well as earning continued spots on the list of cleanest cities for short-term particle levels. Albuquerque, NM ranked 9^th on the cleanest for year-round particle pollution list.

Arkansas
Arkansas has generally good air quality, with the exception of Crittenden and Pulaski counties, which have too many high ozone days. Four cities made the list of cleanest cities for short-term particle exposure: Fayetteville-Springdale-Rogers, AR-MO; Fort Smith, AR-OK; Hot Springs; and Texarkana, TX-AK. Ten counties made the list of cleanest counties for short-term particle pollution exposure and one made the list for cleanest counties for ozone.

Louisiana
Baton Rouge-Pierre Part ranked as the 20^th most ozone-polluted city in the nation, the first time a Louisiana city has placed on that list. More high ozone days during 2002-2004 in East Baton Rouge Parish apparently drove this, the worst ranking the city has had. Fortunately, two cities earned spots on the list of the cleanest cities for ozone, Fort Polk South-De Ridder and Houma-Bayou Cane-Thibodaux. Lafayette-Acadiana landed on the list of the cleanest cities for shortterm particle levels. In addition, several parishes improved air quality enough to raise their grades; most notably, Jefferson Parish improved to a D from an F in ozone levels.

New Mexico
Fortunately, New Mexico has some of the best air quality in the region. Santa Fe-Espanola remained ranked as the 2^nd cleanest city in the nation for year-round levels of particle pollution, while Farmington was ranked 7^th cleanest on the same list. Both cities also earned spots on the list of cleanest cities for short-term particle levels. Albuquerque ranked as 9^th cleanest city for year-round particle pollution exposure. Three counties landed on the cleanest county list for year-round particle levels and ozone, while six counties were on the cleanest list for shortterm particle exposure. Sandoval County ran the rare triple, earning a spot on the cleanest county list for all three pollutant exposures.

Oklahoma
Oklahoma’s biggest air pollution problem is unhealthy levels of ozone in Tulsa County. However, Tulsa County and nine other counties rank among the cleanest for short-term exposure to particle pollution. The Tulsa-Bartlesville metropolitan area earned a place on the list of cleanest cities for short-term particle pollution. Three counties earned spots on the list of cleanest counties for ozone air pollution.

Texas
In Texas, the most widespread air pollution problem remained ozone. Houston and Dallas-Fort Worth continue to rank as the 6^th and 8^th most ozone-polluted cities in the nation. San Antonio joined them on that list for the first time in this report, emerging at 23^rd most ozone-polluted city. Harris County and Tarrant County ranked 8^th and 11^th most ozone-polluted counties.

Despite this, Texas also has some of the nation’s cleanest cities for short-term exposure to particle pollution, including Amarillo, Corpus Christi-Kingsville, Lubbock-Levelland, Midland-Odessa and Texarkana, TX-AR. Midland-Odessa also earned a spot on the list of cleanest U.S. cities for year-round particle pollution. Laredo continued to be on the list of cleanest cities for ozone. Ten counties in Texas placed on the list of the cleanest for short-term particle pollution exposure and two made the list for cleanest for ozone pollution. Brewster County earned a rare spot on all three lists of the cleanest counties.

Several counties improved their air quality enough to improve their grades. Most notably, El Paso improved to a D from an F in ozone. Unfortunately, Jefferson and Orange counties had more unhealthy ozone days, so their grade dropped to an F from a D.