Air pollution

AOT40 - Accumulated
ccumulated dose Over
a Threshold
of 40 ppb
The long-term critical level of ozone for crops:
An AOT40 of 3000 ppb.h accumulated over 3 months.
This critical level was derived experimentally using open-top
chambers to expose field-grown wheat to ozone.
The data from spring wheat experiments in 6 countries, 10 seasons
and with 10 cultivars were used to derive an exposure response
relationship with an r 2 of 0.88.
The AOT40 associated with a 5% reduction in yield, 3000 ppb.h, was
accepted as the critical level of ozone for yield reduction in crops.
Herschbach 2007