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
as it is lowered 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, 1996, 2014, and 2019 confirm
the effect. 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 8-hour standard as the
standard is lowered. Our research indicates that the "piston
effect" will be a problem across many sites in the United
States. Our research results about the "piston effect"
were summarized into a final report in May 1997 and a scientific
paper was published in Environmental Science and Technology
in June 1998 (Lefohn et
al., 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.
Lefohn A. S., Shadwick D. S. and
Ziman S. D. (1998). The Difficult Challenge of Attaining EPA's
New Ozone Standard. Environmental Science & Technology. 32(11):276A-282A.
