Brochures

Smog

• Air Quality Objectives
• Ozone Problem Areas
• How Does Smog Affect Our Health?
• Smog Research
• Smog Alerts
• Federal Smog Management Plan
• What You Can Do

Originally, the term "smog" referred to a mixture of smoke and fog in the air. Today, "smog" describes a noxious mixture of many air pollutants-including vapors, gases and particles-that can often be seen as a brownish-yellow haze.

In Canada smog is a concern in most major urban centres but, because it travels with the wind, it can affect sparsely populated areas as well.

Particularly vulnerable to smog are the elderly, those with existing heart or lung disease and small children. Even healthy adults can be adversely affected by high levels of smog.

Two key components of smog are airborne particles and ground-level ozone.

Airborne Particles: These are dust or minute droplets of liquid that are small enough to remain suspended in the air. These particles give smog its color and can affect visibility. Depending on the types of particles present, the air can appear yellowish-brown, or even white.

Particles small enough to be inhaled seem to have a significant effect on human health, particularly for those who already suffer from heart or lung disease. Of particular concern to our health are the ultra-fine and very fine particles (less than 2.5 microns across) that can penetrate deep within the lungs. These very small particles may remain suspended in the air for days or even weeks.

Recent studies have shown that every major Canadian urban centre has levels of airborne particles high enough to pose a health risk.

Ground-Level Ozone: Ozone is a colorless and highly irritating gas that forms when sunlight "cooks" the soup of air pollutants often found over urban areas on hot summer days. Two common air pollutants, nitrogen oxides (NOx) and volatile organic compounds (VOC) react with each other to produce ground-level ozone.

Unlike the ozone that forms naturally in the stratosphere, ground-level ozone does not provide any significant protection from the sun's harmful UV rays, nor does it find its way to the upper atmosphere.

More than half of all Canadians live in areas where ground-level ozone may reach unacceptable levels during the summer months. Periods of high ozone often last several days and frequently occur when a stagnant air mass traps pollutants over a region.

Exposure to ozone can irritate the nose and throat and cause chest tightness, coughing and wheezing. High ozone levels in Canada have been linked to increased emergency hospital visits and admissions There is also evidence that ozone exposure heightens the sensitivity of asthmatics to allergens.

Not only do airborne particles and ground-level ozone pose problems for humans, they are known to damage vegetation, reduce crop productivity, and to cause deterioration in some natural and synthetic materials, paints and dyes.

Air Quality Objectives

Smog levels are measured against air quality objectives developed jointly by federal and provincial governments. These objectives aim to protect the health of humans, crops and forests by specifying target levels for key air pollutants.

The current air quality objective for ground-level ozone in Canada is 82 ppb (parts per billion) over a one-hour period-one of the most stringent ozone guidelines in the world. During especially hot summers, concentrations of ozone in parts of Ontario and Quebec have been more than twice the air quality objective of 82 ppb.

Canada is currently re-evaluating its air quality objective for ozone, and is looking at developing new objectives for airborne particles. These would reflect the latest scientific research, which reveals that there are no "safe" levels of exposure to either of these smog components.

Ozone Problem Areas

Three regions of Canada are particularly prone to ground-level ozone problems.

Windsor-Québec City Corridor:

This narrow strip along the north shores of Lake Erie, Lake Ontario and the St. Lawrence River experiences high levels of ozone more often and for longer periods of time than any other area of the country. While much of the smog here is generated locally, air pollution from the United States contributes about 50 per cent of ground level ozone in the region.

Lower Fraser Valley:

This valley, which includes the City of Vancouver, is bordered by the Coastal Mountains to the north and the Cascade Mountains to the southeast. These unique geographical features, along with the sea-to-shore breezes off the Strait of Georgia, restrict air-flow patterns and contribute to the area's ozone problem. Here, 80 per cent of the smog is generated locally. Motor vehicles in the Vancouver area are the major source of NOx and VOC emissions.

Southern Atlantic Region:

The areas around the Bay of Fundy, southern New Brunswick, and parts of Nova Scotia southwest of Halifax receive air pollution from the United States-primarily the eastern seaboard. Cross border pollution contributes between 50 and 90 percent of this region's smog problem.

How Does Smog Affect Our Health?

Elderly people and those with heart or lung disease-such as asthma, emphysema and chronic bronchitis-are particularly sensitive to air pollutants. Sensitive people may experience symptoms after only one or two hours outdoors.

Children and active adults are also at a greater risk because they typically spend more time outdoors. Children tend to be more sensitive than adults because they breathe faster.

Health studies have focused on two groups of airborne particles that have proven harmful, even at very low levels.

PM10 (particulate matter less than 10 microns across): these particles measure about 1/8 the width of a human hair and are composed primarily of soil, soot and dust from construction and roadways.

PM2.5 (particulate matter less than 2.5 microns across): These very fine particles cause the greatest concern. They penetrate deep into the lungs, where they cause irritation and can exacerbate lung disease. PM 2.5 is derived primarily from common air pollutants, such as sulphur dioxide, NOx, and VOC. Chemical reactions in polluted air convert these gases into particles of sulphate, nitrate and organic compounds; or minute liquid droplets of sulphuric or nitric acid.

Recent studies in Ontario and 16 Canadian cities have demonstrated that hospital admissions for respiratory problems increase with increases in smog levels, and that air pollution may be related to premature deaths from respiratory disease. Other studies on animals have indicated that ozone exposure decreases the lungs' ability to ward off disease.

Smog Research

Environment Canada is working with other federal, provincial and municipal agencies to measure levels of air pollution across Canada. These measurements are needed to understand the extent of the smog problem and to provide a scientific basis for action to reduce smog, and ultimately, to determine the success of these actions.

A monitoring network helps scientists pinpoint the location of significant smog sources, track the flow of air pollution from the United States and understand the nature of smog in different regions of Canada.

More research is needed to establish precisely where smog controls will be most effective. Environment Canada is taking the lead role in this research, which has enabled scientists to develop a method to predict when high levels of smog will occur in urban areas.

Smog Alerts

Environment Canada works with provincial and municipal partners to issue advisories to the public when high levels of smog are expected in their community. These advisories encourage people and industries to take steps to help reduce air pollution, and they help make people aware of the effects of smog on their health and the environment.

A pilot project in Saint John NB examined the feasibility of issuing forecasts of smog levels on a daily basis, regardless of the expected level. This pilot project was very successful and Environment Canada will explore the possibility of providing this service to other urban centres.

Federal Smog Management Plan

Canada's NOx/VOC Management Plan was developed in 1990 by the federal and provincial governments in consultation with industry, public interests and environmental groups. The first phase included 59 initiatives to be undertaken by the federal government to reduce the pollutants that cause ground-level ozone, to advance research and to collect better information. Most of these actions have been completed.

A Phase 2 Federal Smog Management Plan, published in November 1997, builds on the Phase I initiatives, adding further measures, and considering a wider range of pollutants implicated in smog, especially particulate matter. This Plan also takes into account other programs that address acid rain, climate change, energy efficiency and transportation, all of which can contribute to cleaner air and help Canada meet its international air quality commitments.

Phase 2 also assists provinces in resolving regional smog problems, addresses the air pollution that crosses the border from the US and works to co-ordinate regional and federal initiatives.

What You Can Do

To reduce your exposure to the harmful ingredients in smog, listen during the summer for Environment Canada's Smog Advisories and avoid vigorous outdoor exercise when concentrations of ground-level ozone and airborne particles are high.

To do your part to clean up the air, avoid using gas-powered engines around your home during smog advisories and look for opportunities to car pool or use public transit during peak traffic periods.

For further information:

1-800-668-6767

Visit Environment Canada's Clear Air web site at :
http://www.ec.gc.ca/air/introducion_e.cfm

Cette publication est aussi disponible en français -- June/98

Published by Authority of the Minister of the Environment, September 1998
Minister of Supply and Services Canada 1998

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