Ozone phytotoxicity evaluation and prediction of crops production in tropical regions

Increasing ozone concentration in the atmosphere can threaten food security due to its effects on crop
production. Since the 1980s, ozone has been believed to be the most damaging air pollutant to crops. In
Malaysia, there is no index to indicate the reduction of crops due to the exposure of ozone. Therefore, this
study aimed to identify the accumulated exposure over a threshold of X ppb (AOTX) indexes in assessing
crop reduction in Malaysia. In European countries, crop response to ozone exposure is mostly expressed
as AOT40. This study was designed to evaluate and predict crop reduction in tropical regions and in
particular, the Malaysian climate, by adopting the AOT40 index method and modifying it based on
Malaysian air quality and crop data. Nine AOTX indexes (AOT0, AOT5, AOT10, AOT15, AOT20, AOT25,
AOT30, AOT40, and AOT50) were analyzed, crop responses tested and reduction in crops predicted. The
results showed that the AOT50 resulted in the highest reduction in crops and the highest R
2
value
between the AOT50 and the crops reduction from the linear regression analysis. Hence, this study
suggests that the AOT50 index is the most suitable index to estimate the potential ozone impact on crops
in tropical regions. The result showed that the critical level for AOT50 index if the estimated crop
reduction is 5% was 1336 ppb h. Additionally, the results indicated that the AOT40 index in Malaysia gave
a minimum percentage of 6% crop reduction; as contrasted with the European guideline of 5% (due to
differences in the climate e.g., average amount of sunshine)