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Supplement 2
Indicator name: Ambient levels of other air pollutants. Issue name: Urban air quality Purpose and rationale Although, ground-level ozone and airborne particules are the contaminants that generally concern us the most from a health perspective, NOx, SO2, TSP, and CO are also important to track. NOx reacts with volatile organic compounds in the presence of sunlight to form ground-level ozone. Both NOx and SO2 combine with NH3 to form secondary airborne particules. They also both combine with water molecules in the air to form nitric and sulphuric acid that contributes to acid precipitation. Directly, nitrogen dioxide (NO2), the main component of inhaled NOx, irritates the lungs, and lowers resistance to respiratory infection. In children and adults with respiratory disease, NO2 can cause symptoms including coughing, wheezing and shortness of breath. Even short-term exposure to NO2 affects lung function. Exposure to SO2 leads to eye irritation, shortness of breath and impaired lung function. When inhaled SO2 primarily stays in the nose, mouth and throat but can penetrate more deeply into the lungs during physical activity. When combined with water, SO2 converts to sulphuric acid, which is highly irritating to the sensitive surface lining the respiratory tract. Prolonged or repeated exposure can cause long-term damage to the lungs. CO is an air pollutant closely associated with harmful health effects and, in high concentrations, is deadly. While it is now known that smaller particules have a greater impact on human health, the historical trend in larger airborne pollutants represented by measurements of total suspended particulates is still useful as an overall indicator of particulate levels. Methodology The data is from the National Air Pollution Surveillance Network. Sulphur dioxide, nitrogen dioxide and total suspended particulates are expressed as percentages of the annual acceptable air quality objective. The average yearly value of each station that met the criterion of 365/2 readings for a particular pollutant were included for that year. All of the yearly averages were then averaged together to determine the final value that was compared to the annual objective. Carbon monoxide is the average of the 98th percentiles of eight-hour averages, expressed as percentages of the eight-hour maximum acceptable air quality objective. Caveats and limitations Measurement stations are preferentially located in urban areas and are not representative of all areas in Canada. The opening, closing and relocation of stations as well as missing data affect the number of stations that report data in each year. In general, the number of stations included increases over time and changes in measured pollutant levels could be due in part to the inclusion of variable station locations. Targets and/or benchmarks The national air quality objectives are: Sulphur dioxide: 30 µg/m3 (annual average) Nitogen dioxide: 60 µg/m3 (annual average) Total suspended particulates: 60 µg/m3 (annual average) Carbon monoxide: 6 mg/m3 (8 hour average) Geographic coverage Canada Units of measure Percent of standard Terminology/glossary NOx: This group of nitrogen-oxygen compounds includes the gases nitric oxide, nitrogen dioxide (NO2) and nitrous oxide. Websites and/or references The National Air Pollution Surveillance Network http://www.etcentre.org/NAPS/index_e.html
Ambient concentrations of air pollutants in Canada Data source (organization) Environmental Technology Centre Data contact person Tom Dann Environmental Technology Centre Environment Canada (613) 991-9459 Data brief description Ambient levels of total suspended particulates, nitrogen dioxide, sulphur dioxide, carbon monoxide across Canada. Data collection period and frequency Continuously |
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