The Comparison of Forms of Ambient Air Quality Standards between Highest Value and Percentile Value for PM10

Abstract

The purpose of this research is to study the suitable form of Thailand National Ambient Air Quality Standard (NAAQS) of 24-hour PM₁₀ (Short-term standard) for assessing the effective policy in the long term and recommend the standard value of NAAQs in the new form that is as stringent as before. This study compared the existing form of 24-hour PM₁₀ Air Quality Standards (maximum 24-hour PM₁₀) with the proposed 95^th-percentile (P95) and 98^th-percentile (P98) values by using air quality data from PCD of Thailand for 10 years (B.E. 2548-2557). The scatter diagram shows that correlation coefficient (R) between annual average (AN) with 95^th-percentile (P95), 98^th-percentile (P98) and maximum (A1) values were found to be equal to 0.8517, 0.7822, 0.6880 respectively, Therefore, it can be concluded that 95^th-percentile is a more suitable form of short term standard. Furthermore, the new standard should be as stringent as before based on the number of stations that exceed the standard each year in conjunction with linear regression analysis. The appropriate standard in the P95 form was found to be equal to 80 µg/m³. It is proposed that the 95^th-percentile (P95) standard value of 80 µg/m³ can be used as a better form of 24-hour PM₁₀ standard and can evaluate the situation of air quality with less fluctuation from year-to-year. As a result, the government can make a more consistence mitigation policy than the past.