Scientists and engineers around the world
are becoming aware that the United States 8-hour ozone standard
may present a problem that is called "unattainability."
In November 1998, the topic was discussed at an international
meeting in Beijing, China. The unattainability issue has been
raised by A.S.L. & Associates and others. In the coming
years, policymakers will find that the 8-hour ozone standard
will be difficult to attain and control strategies will not work
as planned. Mid-range hourly average concentrations decline slower
than the higher hourly average concentrations and make it difficult
to attain the standard. Independent analyses have confirmed the
"piston effect". EPA reports and papers published in
1985, 1995, and 1996 confirm the effect. A.S.L. & Associates
has estimated that more than 50% of the areas originally
identified by the EPA as violating the 8-hour ozone standard
would have difficulty in attaining the standard. For many sites
in the United States, there are simply too many concentrations
in the mid range and these concentrations are responsible for
the violation of the new 8-hour standard. Our research indicates
that the "piston effect" will be a widespread problem
across sites in the United States. Our research results were
summarized into a final report in May 1997 and a scientific paper
was published in Environmental Science and Technology
in June 1998. A slide presentation
summarizing the "piston effect" is available. More
detailed information about the effect and the possible reasons
for its occurrences can be found by clicking
here.
