A comparison of North American and Asian exposure-response data for ozone effects on crop yields

Modelling-based studies to assess the extent and magnitude of ozone (O3) risk to agriculture in Asia suggest that yield losses of 5 to 20 % for important crops may be common in areas experiencing elevated O3 concentrations. These assessments have relied on European and North American dose-response relationships and hence assumed an equivalent Asian crop response to O3 for local cultivars, pollutant conditions and climate. To test this assumption we collated comparable dose-response data derived from fumigation, filtration and EDU experiments conducted in Asia on wheat, rice and leguminous crop species. These data are pooled and compared with equivalent North American dose-response relationships. The Asian data show that at ambient O3 concentrations found at the study sites (which vary between 30 and 80 ppb 4-8 hr growing season mean), yield losses for wheat, rice and legumes range between 5-48, 3-47 and 10-65 %, respectively. The results indicate that Asian grown wheat and rice cultivars are more sensitive to O3 than the North American dose-response relationships would suggest. For legumes the scatter in the data makes it difficult to reach any equivalent conclusion in relative sensitivities. As such, existing modelling-based risk assessments may have substantially underestimated the scale of the problem in Asia through use of North American derived dose-response relationships.