An important aspect
of defining ways to protect human health and vegetation that
seems to get overlooked is that the higher hourly average concentrations
of ozone should be given greater weight than the mid and low
values. Some scientists simply use average values to represent
the potential for pollutant exposures to affect an organism.
However, average concentrations "smooth" the data and
treat all concentrations the same. With the higher hourly average
concentrations being potentially more important than the lower
values, calculating an average concentration index, using many
hourly average concentrations, is an inappropriate approach for
developing exposure metrics for protecting humans and plants.
Vegetation scientists have focused on the
important research relating exposure
and effects and quantifying
the results. Researchers collaborating with A.S.L. & Associates
have published numerous peer-reviewed papers on the subject of
the importance of peak hourly average ozone concentrations and
are continuing to perform research on this very important and
relevant scientific issue (see Musselman et al., 2006 for a current
critical review of the literature).
Similarly, researchers collaborating with
A.S.L. & Associates, have published peer-reviewed papers
describing controlled laboratory exposures of human volunteers
indicating that higher ozone hourly average concentrations elicit
a greater effect on hour-by-hour physiologic response (i.e.,
forced expiratory volume in 1 s [FEV1]) than lower hourly average
values. The latest results applied realistic, variable ozone
exposures in contrast to the 3 scientific experiments, which
utilized constant concentration exposures. These 3 scientific
experiments, whose results formed the basis for the 1997 8-h
average 0.08 ppm ozone standard, were based on constant
ozone exposures, which rarely occur under realistic ambient conditions.
For additional information about realistic variable concentrations,
please click here.
References
Musselman R. C., Lefohn A. S., Massman
W. J., and Heath, R. L. (2006) A critical review and analysis
of the use of exposure- and flux-based ozone indices for predicting
vegetation effects. Atmospheric Environment. 40:1869-1888.
