Limit prior to 2008: .08 parts per million
New limit set in 2008: .075 parts per million
New limit pending in 2010: Between .06 and .07 parts per million
How WNC stacks up
Ozone levels have improved gradually in WNC over the past 10 years. They can vary widely from year to year depending on weather, however. Wetter and cooler summers see fewer bad ozone days that hotter, drier ones.
To determine whether WNC meets the new ozone limits, an average of three years worth of ozone readings — from 2008 through 2010 — will be used.
Here’s the levels for ozone monitoring stations in the region based on the three-year average from 2007-2009. Ozone is worse at higher elevations and surprisingly consistant across the mountains.
Waynesville .068 parts per million
Bryson City .064 parts per million
Asheville .069 parts per million
High elevation sites
Purchase Knob .074 parts per million
(near Hemphill Knob above Jonathan Creek in Haywood County)
Frying Pan .074 parts per million
(near Mount Pisgah off the Blue Ridge Parkway in Haywood County)
Mount Mitchell .074 parts per million
(highest elevation on the east coast)
• A monitoring station has been recently installed on Barnet Knob on Cherokee Indian Reservation and will be providing data this year.