From 1980 through
1994, significant decreases occurred. However, since 1994, no
significant trend in decreasing ozone has occurred. When one
compares the Fairfield County figure with the results described
in EPA's latest trends report, the similarities are observed.
The slight downward pattern observed for the periods 2002-2004,
2003-2005, and 2004-2006 is a result of the 0.081 ppm 4th highest
annual 8-hour average value experienced in 2004. The figure below
illustrates what is happening.
The 0.081 ppm value
that occurred in 2004 is the lowest 4th highest annual 8-hour
average value recorded between 1980 and 2007. The 4th highest
values recorded in the years 2005 and 2006 were 0.090 and 0.095
ppm, respectively. The effect of the 0.081 ppm value was to depress
the 3-year average of the 4th highest 8-hour concentration for
the 2004-2006 period. As noted in the previous figure, the 4th
highest 8-hour average increased from 0.089 for the 2004-2006
period to 0.092 for the 2005-2007 period. The elimination of
the 2004 contribution of the 0.081 ppm value (as a result of
including only the years 2005, 2006, and 2007), resulted in a
higher 3-year average for the 4th highest 8-hour concentration
for the 2005-2007 period. It appears that the "piston"
effect is affecting, in a large degree, the nation's ability
to improve its air quality.
