PRB 98-4E
INTRODUCTION: SMOG AND HEALTH
Prepared by:
Christine Labelle
Science and Technology Division
October 1998
A
correlation between air pollution and its effects on health was first observed in 1952 in
London, England, when 4,000 persons died from respiratory diseases aggravated by a high
concentration of acid smog. The term "smog," which has for some 30 years been
used to mean chemical air pollution, is a contraction of the words "smoke" and
"fog." Smog is formed mainly above urban centres by concentrated human
activities that include the combustion of fossil fuels and the smelting of ores. Smog is
composed mainly of tropospheric ozone, produced by a photochemical reaction between
volatile organic compounds and nitrogen oxides; primary particulate matter such as pollen
and dust; and secondary particulate matter such as sulphur oxides, volatile organic
compounds, and ammonia gas. The severity of smog is usually assessed by measuring
ground-level ozone.
In
Canada, air pollution is greatest in the four regions described below, where inhabitants
are increasingly concerned about the effects of air pollution, particulate matter, and
tropospheric ozone on their health.
The
Windsor-Quebec corridor is a region including the north shore of Lake Erie and Lake
Ontario and the north and south shores of the St Lawrence River as far east as Quebec. The
pollution concentrated in this region results from activities there and in regions such as
Ohio and cities such as Cleveland and Detroit in the United States. Windsor is the city
most affected by smog.
Southern
Ontario, especially rural southwestern Ontario, is the region in Canada most affected
by pollution. Nearly 50% of this region’s measured ground-level ozone, the main
component of smog, results from air pollution from the United States.
The
Atlantic region includes southern New Brunswick, southwestern Nova Scotia, and the
Bay of Fundy. Saint John, New Brunswick, experiences 90% of the periods of smog in this
region, most of whose pollution comes from the east coast of the United States.
The
Lower Fraser Valley is in southern British Columbia and includes Vancouver.
Approximately 80% of ground-level ozone in this region comes from local sources,
particularly tailpipe emissions.
The scientific
community is paying increasing attention to the effects of air pollution on health. Most
studies are carried out on ozone, sulphates, or particulate matter. Increasingly, they
show that there is no minimum threshold at which human beings are not sensitive to smog
and that, to varying degrees, most persons may be affected. The federal government is
providing itself with ever more legislative and technical tools to combat the situation.
The next two sections of this document describe the various components of smog and their
effects on health. |