Unformatted text preview: are either occurring or predicted. The Air Quality Health Index has been divided into four Health Risk Categories: ! ! ! ! Low Health Risk AQHI values from 1 to 3 Moderate Health Risk AQHI values from 4 to 6 High Health Risk AQHI values from 7 to 10 Very High Health Risk above 10. (A very rare occurrence, usually connected to wildfire smoke). Page 1 of 1 The AQHI was designed as a tool that could be used by people to reduce their short-term exposure to air pollution and plan, on a daily basis, to modify their behaviour and reduce their personal health risk. Therefore, the AQHI responds to the acute, or short-term, changing levels of risk associated with air pollution. The AQHI is not intended to address the health impact on individuals of long-term (multi-year or multi-decadal) exposure to air pollutants. AQHI = 10/10.4*(100*(e(0.000871*NO2)-1+ e (0.000537*O3) -1 + e (0.000487*PM2.5)-1))
In this equation, NO2, O3 and PM2.5 (nitrogen dioxide, ozone and fine particulate matter less than 2.5 microns in size, respectively) are concentrations averaged over three consecutive hours. Units are parts per billion for each gas and micrograms per cubic metre for PM2.5. Low health risk: 1-3 Medium:4-6 High: >7 The three pollutants that form the basis of the AQHI formula each have direct health impacts, but some, particularly nitrogen dioxide9, are more likely surrogates for other pollutants that impact health but that are not included in the calculation10. These other pollutants include ultrafine particles, metals and other toxic substances. They may mimic the variations in concentrations of the three AQHI component pollutants when they are produced by the same processes (e.g., vehicle exhaust), but they are not routinely monitored. In particular, the health effects of the hundreds of products of combustion are likely being reflected in the health effects linked to NO2 and PM2.5 in the AQHI, since combustion is a primary source of these two pollutants. 2 9 10 Stieb, D., Health Canada. (2008)....
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This document was uploaded on 03/31/2014.
- Spring '14