One-Hour Equivalent of a 24-Hour Average Particulate Matter Standard and its Potential Application in the Index of the Quality of the Air (IQUA)

摘要

The Alberta Index of the Quality of the Air (IQUA) is part of Alberta's air qualityrnmanagement system. The IQUA provides a qualitative description of air quality based on hourlyrnconcentrations of five major air quality parameters (CO, O_3, NO_X, SO_2, and coefficient of hazern(COH)).rnThe purpose of this paper is to explore the option of incorporating a PM_(2.5) standard intornthe Alberta IQUA. When a new parameter is incorporated into the IQUA, the resulting indexrnshould reflect the relevant air quality guidelines and standards, provide the public with a clearrnpicture of the air quality, and retain the integrity of the IQUA. These issues are addressed in thisrnpaper via a three-part analysis. First, a one-hour equivalent of the 24-hour PM_(2.5) Canada WidernStandard is identified. Second, an assessment of hypothetical exposure is performed. Finally,rnthe potential application of a one-hour PM_(2.5) concentration in the IQUA is discussed.rnIn the first part, daily maximum and daily average PM_(2.5) data from monitors located atrntwo locations in Alberta were used to derive the relationship between one-hour (x) and 24-hourrnaverage (y) PM_(2.5) levels. The relationship was determined as y = ax~b, where a and b are locationspecificrnparameters. Using this relationship, a one-hour concentration of 80 μg/m~3 wasrndetermined to be equivalent to the 24-hour CWS of 30 μg/m~3.rnIn the second step, the one-hour PM2.5 concentrations of 80 μg/m~3 and 40 μg/m~3 werernused as breakpoint concentrations in a hypothetical hourly exposure analysis. This analysisrnshowed that the one-hour breakpoints could be effectively used to assist an individual in makingrna decision about their air quality exposure. A 24-hour PM_(2.5) concentration of 18 μg/m~3 was usedrnas a breakpoint to analyze daily exposure. This analysis showed some differences between thernone-hour and 24-hour breakpoints.rnFinally, an analysis was performed to determine the implications to Alberta's IQUA.rnIncorporating PM_(2.5) into the IQUA decreased the percentage of time air quality was in the Goodrncategory from 93.6% to 90.5% in 1998 at the Edmonton Northwest station and from 99.5% torn98.1% in 1998 at the Calgary Central station. Corresponding increases in the frequency of Fairrnand Poor air quality are noted at these monitoring stations, when PM_(2.5) is incorporated into thernIQUA.