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 5–20% 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 w35–75 ppb 4–8 h 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.