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Ground-level Ozone Episodes in North East North America
The Canadian ambient air quality objective for ground-level ozone is based on three levels of ambient air quality (Fuentes and Dann, 1993):
- the maximum desirable which defines the long term goal and provides the basis for policy formulation.
- the maximum acceptable which provides adecuate protection against adverse effects.
- the maximum tolerable levels which denotes time-based concentrations of ozone beyond which appropriate action is required to protect the health of the general population.
To represent the spatial distribution of average days with ozone > 82 ppb (1986-1993) in Eastern North America several stations were grouped (Data Analysis Working Group, 1997). The Canadian ozone measurements are obtained from the National Air Pollution Surveillance (NAPS) program which involves federal, provincial and municipal governments. The Environment Protection Service, a federal agency, coordinates the program. Provincial and municipal agencies maintain the monitoring sites and perform quality control of the data. Ozone data for a number of rural sites are collected through the Canadian Air and Precipitation Monitoring Network (CAPMoN) and coordinated by the Meteorological Service of Canada. Data for the USA was obtained from 180 US Aerometric Information and Retrieval System (AIRS) and National Dry Deposition Network (NDDN) sites. A complete list of the sites and locations is given in The NAPS table and NAPS Map.
The yearly averages are based on May to September ozone mixing ratios (Data Analysis Working Group, 1997). It was based on 153 Canadian ozone monitoring stations and 69 US rural sites. Details of these data could be found in the Table of Ozone Mixing Ratio Percentiles. The map illustrates that the Ontario lakeshore sites lies within the 20-days-per-year isopleth of days with ozone > 82 ppb.
Brunett et al. (1998) found a strong correlation between high ozone episodes and hospital admissions a day later.
The following maps show the extent of the problem in urban and rural areas.
Number of days of ozone exceedances in Eastern North America (76 KB jpg image)
Source: Data Analysis Working Group (1997)Number of days of ground-level zone exceedandes in southern Ontario and Quebec (53 KB jpg image)
Southern Ontario is the most smog-prone region in Canada, typically recording 10-20 days per year with ozone concentrations exceeding national standards of 82 ppb. Healthy adults can experience permanent lung damage by spending one hour in air with an ozone concentration of 120 ppb or by spending 4 hours in air with 82 ppb. The relationship between ozone concentrations and hospital admissions reveals no threshold below which health effects disappear. In Ontario, some estimates claim that smog causes about 1800 premature deaths, 1400 hospital admissions and up to $70 million of crop and ornamental tree damage each year.
Source: Fuentes and Dann (1993).Ground-level ozone levels in cities across the country (181 KB jpg image) small version (55 KB jpg image)
Source: Smog Fact Sheet, Environment Canada, July 1999.Transboundary ozone into Ontario (57 KB jpg image)
U.S. source regions of transboundary ozone into Ontario, Canada
Source: MOE (1997)Graph of hospital admissions due to high ozone levels (58 KB jpg image)
Source: Burnett, R.T.; J.R. Brook; W.T. Yung and R.E. Dales. 1997. Association between ozone and hospitalication for respiratory diseases in 16 Canadian cities. Environmental Research, Vol. 72:24-31 pp.
References:
Brunett, R.T. S. Cakmak and J. Brook. 1998. The Effect of the Urban Ambient Air Pollution Mix on Daily Mortality Rates in 11 Canadian Cities. Canadian Journal of Public Health, Vol. 89(3): 152-156.
Data Analysis Working Group. 1997. Ground-level Ozone and its Precursors, 1980-1993. Canadian 1996 NOx/VOC Science Assessment. 295 pp.
Fuentes, J.D. and T.F. Dann. 1993. Ground-level Ozone in Canada During 1980 to 1991. Internal Report No. ARD-93-010, Meteorological Service of Canada, Environment Canada. 232 pp.
Smog Fact Sheet, Environment Canada, July 1999.