It is important to relate experimental conditions with those
experienced under real-world conditions. The exposure regimes
experienced under actual ambient conditions did not match those
that elicited growth reduction in the controlled vegetation
experiments on which the 1996 proposed secondary SUM06 standard
was based. The data on which the 1996 proposed secondary
standard was based were derived from experiments associated with
the National Crop Loss Assessment Network (NCLAN). It was
pointed out in the peer-review literature, and acknowledged in
the EPA Criteria Document (U.S. EPA, 1996; U.S. EPA, 2006),
Staff Paper, December 13, 1996, and July 18, 1997 Federal
Notices that these experiments contained numerous hourly average
concentrations greater than or equal to 0.10 ppm near the 10%
yield reduction level, the level at which the standard was
proposed. Many of the locations across the United States that
would violate the 1996 proposed vegetation standard did not
experience numerous occurrences of hourly av