Benzene Comparison*
The major source of benzene and other volatile organic
compounds (VOCs) at urban locations is automobile emissions. VOCs are emitted by numerous other sources including gasoline
marketing and storage tanks, petroleum and chemical industries, dry cleaning, fireplaces, natural gas combustion and
aircraft.
The 5 year average benzene concentration for the years 1998 to 2003 was 1.8 mg/m3 (micrograms
per cubic metre) for Edmonton and 1.7 mg/m3 for Calgary. These values were similar
to those of the other Canadian cities compared. Montreal was significantly higher than the
rest of the cities with an average of 4.2 mg/m3 during the five-year period;
double the benzene concentration of any other Canadian city.
The 2003 annual averages showed that benzene concentrations in Edmonton and Calgary
decreased about 0.1 mg/m3 when compared to the previous five years. All cities
experienced a small decrease in annual benzene concentrations in 2003, except Ottawa (which saw a very small increase).
Montreal had significantly higher benzene concentrations than any other Canadian city in 2003, but it did decrease
to 3.9 mg/m3.
|
Annual Average Benzene Concentrations in Canadian Cities (mg/m3)
|
|
City
|
5 Year Average (1998-2003)
|
2003
|
|
Montreal
|
4.2
|
3.9
|
|
Ottawa
|
1.5
|
1.5
|
|
Toronto
|
1.6
|
1.4
|
|
Winnipeg
|
1.1
|
1.0
|
|
Edmonton
|
1.8
|
1.7
|
|
Calgary
|
1.7
|
1.6
|
|
Vancouver
|
1.7
|
1.1
|
*The cities were compared by looking at the differences in their annual averages over a five-year period (1998-2003) and their most recent annual averages (2003). The city averages were calculated by finding the average of the annual average values for each station within a city. Each city did not necessarily have the same number of stations and it is important to note that this may affect exactly how representative an average is for a given city. Also, some stations may not have been operational for a majority of the time of the comparison, and therefore only stations that had data for at least four out of the five years were used. These same stations were also used in calculating the 2003 averages. The table below shows the number of stations that satisfied the criteria and were thus used for calculating the city averages.
|
City
|
# of Stations Used in Analysis
|
|
Montreal
|
2
|
|
Ottawa
|
2
|
|
Toronto
|
2
|
|
Winnipeg
|
1
|
|
Edmonton
|
2
|
|
Calgary
|
1
|
|
Vancouver
|
1
|
|
