New Hampshire air pollution stats

County	First data available	Last data available
Belknap Co	1997	2007
Carroll Co	1997	2002
Cheshire Co	1997	2007
Coos Co	1997	2007
Grafton Co	1997	2007
Hillsborough Co	1997	2007
Merrimack Co	1997	2007
Rockingham Co	1997	2007
Strafford Co	1997	2003
Sullivan Co	1997	2007