The Piston Effect
Scientists and engineers
around the world are becoming aware that the United States 8-hour
ozone standard is presenting a problem that is called "unattainability."
Almost 20 years ago, the unattainability issue was discussed
by Dr. Lefohn, President and Founder of
A.S.L. & Associates. In November 1998, the topic was
discussed at an international meeting in Beijing, China by Dr.
Lefohn. Policymakers are now finding that the 8-hour ozone standard
will be difficult to attain and control strategies will not work
as planned as lower and lower standard levels are promulgated.
Mid-range hourly average concentrations decline slower than the
higher hourly average concentrations and make it difficult to
attain the lower standards. Independent analyses have confirmed
the "piston" effect. Two publications (Lefohn et al.,
2017; Lefohn et al., 2018) identifies how the "piston"
effect influences ozone monitoring sites in the EU and the US.
Watch a slide
presentation of the "piston" effect.
Lefohn, A.S., Malley, C.S., Simon, H.,
Wells. B., Xu, X., Zhang, L., Wang, T., 2017. Responses of human
health and vegetation exposure metrics to changes in ozone concentration
distributions in the European Union, United States, and China.
Atmospheric Environment 152: 123-145. doi:10.1016/j.atmosenv.2016.12.025.
Lefohn, A.S., Malley, C.S., Smith, L.,
Wells, B., Hazucha, M., Simon, H., Naik, V., Mills, G., Schultz,
M.G., Paoletti, E., De Marco, A., Xu, X., Zhang, L., Wang, T.,
Neufeld, H.S., Musselman, R.C., Tarasick, T., Brauer, M., Feng,
Z., Tang, T., Kobayashi, K., Sicard, P., Solberg, S., and Gerosa.
G. 2018. Tropospheric ozone assessment report: global ozone metrics
for climate change, human health, and crop/ecosystem research.
Elem Sci Anth. 2018;6(1):28. DOI:
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