MHLU - Health Status Resource

Air Quality

Air Quality

Key Findings: 
  • Between 2004 and 2010 the annual number of poor air quality days generally decreased. There have been fewer smog advisories in Middlesex-London and in Ontario as a whole in recent years compared to 2005 to 2007 (Fig. 11.1 and Fig. 11.2).
  • Between the years  2003 and 2011, Middlesex-London had just over a 70% chance of experiencing a local smog advisory if an advisory was issued anywhere in Ontario (Fig. 11.2).
  • For all measured pollutants except average mean ozone levels there was a decrease in the annual means and in the maximum levels.  Generally the decrease seen over time (2000 to 2010) was greater in London than in the comparison sites in Southern Ontario(Fig. 11.3Fig. 11.4, Fig. 11.5, Fig. 11.6, Fig. 11.7, and 11.8).
  • Between 2000 and 2010, there was a gradual rise in the annual mean concentration of ozone in the City of London and in the Southern Ontario comparators (Fig. 11.5).
  • The Ontario Medical Association’s ICAP model was used to estimate the number of health events attributable to PM2.5, O3, NO2, SO2 and CO in Middlesex-London. Exposure to smog-related pollutants at the current-day ambient concentrations in Middlesex-London will lead to an estimated 434 total premature deaths in 2012 (data not shown).
Interpretive Notes

Canada’s smog ‘hot spot’ is Southwestern Ontario which experiences high levels of pollutants because of many sources of domestic and transboundary air pollution.  In Southwestern Ontario, London experiences elevated levels of ambient air pollution because it is situated at the intersection of two major highways (401 and 402) at the center of one of the busiest regional transport systems in Canada. Due to the amount of travel across the Windsor-Quebec corridor, this is an important contributor to regional air pollution.  Long-range migration of ozone is another significant contributor to air pollution in the City of London.  It is estimated that more than half of all smog forming pollutants come from the United States; from industries in Ohio, Illinois and Michigan and the rest by use of cars and electricity during hot summer days.

 Data on each pollutant may be presented here in two different ways; the average (mean) concentration and the maximum concentration.  The average concentration provides information about the sustained levels of air pollutants that the population is exposed to on a daily basis. An increase in average levels of pollutants is an important contributor to long-term chronic respiratory and cardiovascular diseases.  The maximum concentration of a pollutant observed in a timeframe (usually a year), on the other hand, is associated with acute respiratory events.

Standards have been set across Canada, for some pollutants, and within Ontario for other pollutants.  These standards sometimes correspond to the maximum allowable level of a pollutant and other times to the mean concentration.   For other pollutants there are no set standards.

 Air quality monitoring data was compared for six of the 40 Ontario monitoring sites most similar to London in regional sources of air pollution. Sites such as Sarnia, Windsor, Port Stanley and Grand Bend were selected because they are in the Great-Lakes Basin Airshed and experience transboundary pollution from the United States. Toronto, Hamilton, Sarnia and Windsor were selected because they, like London, experience pollution from the Quebec-Windsor transportation corridor.

How this Indicator was Calculated: 
Ontario Public Health Standard: 

Population Health Assessment and Surveillance Protocol - Section 1, Subsections b-iii, vi, viii

Rabies Prevention Control - Requirement #4

Infectious Diseases Prevention and Control Standard - Requirement #3

Health Hazard Prevention and Management Standard - Requirement #2

Jargon Explained

Air Quality Index 

This index is based on six pollutants that have adverse effects on human health and the environment: ozone (O3), fine particulate matter (PM2.5), nitrogen dioxide (NO2), carbon monoxide (CO), sulphur dioxide (SO2), and total reduced sulphur (TRS) compounds.

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Smog is made up of predominantly ground-level ozone and fine particulate matter. Ozone has an impact on smog levels primarily in summer whereas fine particulate matter elevates smog levels all year.

Fine Particulate Matter (PM2.5

Small airborne solid particles are referred to as fine particulate matter (PM2.5) and may contain harmful aerosols, combustion particles and metal vapours.

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Ozone (O3) is created when nitrogen oxides and volatile organic compounds combine in the presence of sunlight.

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Nitrogen Dioxide

Ambient nitrogen dioxide (NO2) is derived from oxidized nitrogen oxide (NO) and is generally a marker of combustion related air pollution, including power and chemical plants and traffic emissions.

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Sulphur Dioxide

Sulphur Dioxide (SO2) is a gaseous oxide that results from the combustion of sulphur containing fossil fuels and also from the smelting of sulphur containing ores.

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