Toxic fog settles over Salt Lake City

The pollution has turned so bad that more than 100 Utah doctors called Jan. 23 on authorities to immediately lower highway speed limits, curb

industrial activity and make mass transit free for the rest of winter.

Doctors say the microscopic soot — a shower of combustion particles from

tailpipe and other emissions — can tax the lungs of even healthy

people.

Dr. Gary Kunkel arrives at the Utah State Capitol wearing a breathing mask before a news conference Wednesday, Jan. 23, 2013, in Salt Lake City. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. The U.S. Environmental Protection Agency has singled out the greater Salt Lake region as having the nation's worst air for much of January, when an icy fog smothers mountain valleys for days or weeks at a time and traps lung-busting soot. (AP Photo/Rick Bowmer)
Dr. Gary Kunkel arrives at the Utah State Capitol wearing a breathing mask before a news conference Wednesday, Jan. 23, 2013, in Salt Lake City. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. The U.S. Environmental Protection Agency has singled out the greater Salt Lake region as having the nation's worst air for much of January, when an icy fog smothers mountain valleys for days or weeks at a time and traps lung-busting soot. (AP Photo/Rick Bowmer)
Dr. Gary Kunkel arrives at the Utah State Capitol wearing a breathing mask before a news conference Wednesday, Jan. 23, 2013, in Salt Lake City. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. The U.S. Environmental Protection Agency has singled out the greater Salt Lake region as having the nation's worst air for much of January, when an icy fog smothers mountain valleys for days or weeks at a time and traps lung-busting soot. (AP Photo/Rick Bowmer)
Smog from an inversion hangs over the Utah State Capitol Wednesday, Jan. 23, 2013, in Salt Lake City. The U.S. Environmental Protection Agency has singled out the greater Salt Lake region as having the nation's worst air for much of January, when an icy fog smothers mountain valleys for days or weeks at a time and traps lung-busting soot. (AP Photo/Rick Bowmer)
Utah fog
Smog from an inversion hangs over the Utah State Capitol Wednesday, Jan. 23, 2013, in Salt Lake City. The U.S. Environmental Protection Agency has singled out the greater Salt Lake region as having the nation's worst air for much of January, when an icy fog smothers mountain valleys for days or weeks at a time and traps lung-busting soot. (AP Photo/Rick Bowmer)
A poor air quality sign is posted over a highway Wednesday, Jan. 23, 2013, in Salt Lake City. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday demanding immediate action by elected officials. (AP Photo/Rick Bowmer)
Utah fog
A poor air quality sign is posted over a highway Wednesday, Jan. 23, 2013, in Salt Lake City. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday demanding immediate action by elected officials. (AP Photo/Rick Bowmer)
A poor air quality warning is posted over a highway Wednesday, Jan. 23, 2013, in Salt Lake City. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday demanding immediate action by elected officials. (AP Photo/Rick Bowmer)
A poor air quality warning is posted over a highway Wednesday, Jan. 23, 2013, in Salt Lake City. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday demanding immediate action by elected officials. (AP Photo/Rick Bowmer)
A poor air quality warning is posted over a highway Wednesday, Jan. 23, 2013, in Salt Lake City. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday demanding immediate action by elected officials. (AP Photo/Rick Bowmer)
Smog from an inversion hangs over downtown Salt Lake City Wednesday, Jan. 23, 2013. The geography that makes Utah one of the worldís most beautiful places also brings the nationís dirtiest air in winter, when an icy fog smothers mountain valleys for days or weeks at a time. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday demanding immediate action by elected officials. The group wants Gov. Gary Herbert and mayors of northern Utah cities to cut the pollution. (AP Photo/Rick Bowmer)
Utah fog
Smog from an inversion hangs over downtown Salt Lake City Wednesday, Jan. 23, 2013. The geography that makes Utah one of the worldís most beautiful places also brings the nationís dirtiest air in winter, when an icy fog smothers mountain valleys for days or weeks at a time. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday demanding immediate action by elected officials. The group wants Gov. Gary Herbert and mayors of northern Utah cities to cut the pollution. (AP Photo/Rick Bowmer)
In this Jan. 9, 2013, photo, an inversion cloud covers downtown Salt Lake City. A group of Utah doctors is declaring a health emergency over the Salt Lake City area's lingering air pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday, Jan. 23, 2013, demanding immediate action by elected officials. (AP Photo/The Deseret News, Ravell Cal)
In this Jan. 9, 2013, photo, an inversion cloud covers downtown Salt Lake City. A group of Utah doctors is declaring a health emergency over the Salt Lake City area's lingering air pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday, Jan. 23, 2013, demanding immediate action by elected officials. (AP Photo/The Deseret News, Ravell Cal)
In this Jan. 9, 2013, photo, an inversion cloud covers downtown Salt Lake City. A group of Utah doctors is declaring a health emergency over the Salt Lake City area's lingering air pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday, Jan. 23, 2013, demanding immediate action by elected officials. (AP Photo/The Deseret News, Ravell Cal)
In this Jan. 9, 2013, photo, an inversion cloud covers downtown Salt Lake City. A group of Utah doctors is declaring a health emergency over the Salt Lake City area's lingering air pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday, Jan. 23, 2013, demanding immediate action by elected officials. (AP Photo/The Deseret News, Ravell Cal)
In this Jan. 9, 2013, photo, an inversion cloud covers downtown Salt Lake City. A group of Utah doctors is declaring a health emergency over the Salt Lake City area's lingering air pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday, Jan. 23, 2013, demanding immediate action by elected officials. (AP Photo/The Deseret News, Ravell Cal)
In this Jan. 9, 2013, photo, an inversion cloud covers downtown Salt Lake City. A group of Utah doctors is declaring a health emergency over the Salt Lake City area's lingering air pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday, Jan. 23, 2013, demanding immediate action by elected officials. (AP Photo/The Deseret News, Ravell Cal)
In this Jan. 9, 2013, photo, an inversion cloud covers downtown Salt Lake City. A group of Utah doctors is declaring a health emergency over the Salt Lake City area's lingering air pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday, Jan. 23, 2013, demanding immediate action by elected officials. (AP Photo/The Deseret News, Ravell Cal)
In this Jan. 9, 2013, photo, an inversion cloud covers downtown Salt Lake City. A group of Utah doctors is declaring a health emergency over the Salt Lake City area's lingering air pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday, Jan. 23, 2013, demanding immediate action by elected officials. (AP Photo/The Deseret News, Ravell Cal)
In this Jan. 9, 2013, photo, an inversion cloud covers downtown Salt Lake City. A group of Utah doctors is declaring a health emergency over the Salt Lake City area's lingering air pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday, Jan. 23, 2013, demanding immediate action by elected officials. (AP Photo/The Deseret News, Ravell Cal)
FILE - This Jan. 4, 2013, file photo, shows the haze from an inversion hanging over downtown Salt Lake City. The geography that makes Utah one of the world’s most beautiful places also brings the nation’s dirtiest air in winter, when an icy fog smothers mountain valleys for days or weeks at a time. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday demanding immediate action by elected officials. The group wants Gov. Gary Herbert and mayors of northern Utah cities to cut the pollution. (AP Photo/Rick Bowmer)
FILE - This Jan. 4, 2013, file photo, shows the haze from an inversion hanging over downtown Salt Lake City. The geography that makes Utah one of the world’s most beautiful places also brings the nation’s dirtiest air in winter, when an icy fog smothers mountain valleys for days or weeks at a time. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday demanding immediate action by elected officials. The group wants Gov. Gary Herbert and mayors of northern Utah cities to cut the pollution. (AP Photo/Rick Bowmer)
FILE - This Jan. 4, 2013, file photo, shows the haze from an inversion hanging over downtown Salt Lake City. The geography that makes Utah one of the world’s most beautiful places also brings the nation’s dirtiest air in winter, when an icy fog smothers mountain valleys for days or weeks at a time. A group of doctors is declaring a health emergency over northern Utah's lingering pollution problem. Utah Physicians for a Healthy Environment planned to deliver a petition Wednesday demanding immediate action by elected officials. The group wants Gov. Gary Herbert and mayors of northern Utah cities to cut the pollution. (AP Photo/Rick Bowmer)

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