The data plotted is sent to us approximately one hour after it is
collected, between 8am and 8pm, from the
Environmental Protection Agency
(EPA). The EPA uses its
Air Quality
Index to provide general information to the public about air quality
and associated health effects. An Air Quality Index (AQI) of 100 for any
pollutant corresponds to the level needed to violate the federal health
standard for that pollutant. For ozone, an AQI of 100 corresponds to 0.08
parts per million (ppm) over an 8-hour period -- the current federal
standard. Over half of the U.S. population lives in areas where
the AQI exceeds 100 and violates the federal health standard at least once
per year.