Maryland air pollution stats

County	First data available	Last data available
Allegany Co	1997	1998
Anne Arundel Co	1997	2007
Baltimore city	1997	2007
Baltimore Co	1997	2007
Calvert Co	1997	2006
Carroll Co	1997	2006
Cecil Co	1997	2007
Charles Co	1997	2006
Frederick Co	1998	2006
Garrett Co	1997	2007
Harford Co	1997	2007
Kent Co	1997	2006
Montgomery Co	1997	2007
Prince George's Co	1997	2007
Washington Co	1999	2007
Wicomico Co	1997	2001