Air Quality Guidelines Global Update 2005 - World Health ...

2. Global ambient air pollution
concentrations and trends
Bjarne Sivertsen
Summary
Air quality measurements over the last decade have revealed air pollution
problems in many of the major urban areas of the world, with some cities in
developing countries currently facing the greatest challenges. Some typical
ranges of concentrations of the four indicator pollutants found in a selection
of cities around the world are summarized in Table 1.
Table 1. Ranges of annual average concentrations (μg/m 3 ) of PM10, nitrogen
dioxide and sulfur dioxide and one-hour average maximum concentrations of
ozone for different regions, based on a selection of urban data
Region
Africa
Asia
Australia/New Zealand
Canada/United States
Europe
Latin America
PM10
40–150
35–220
28–127
20–60
20–70
30–129
Annual average concentration
Nitrogen
dioxide
35–65
20–75
11–28
35–70
18–57
30–82
Sulfur
dioxide
10–100
6–65
3–17
9–35
8–36
40–70
Ozone
(1-hour maximum
concentration)
120–300
100–250
120–310
150–380
150–350
200–600
The highest concentrations of the “classical” indicators such as PM10 and
sulfur dioxide are found in Africa, Asia and Latin America. The highest
levels of secondary pollutants such as ozone and nitrogen dioxide are measured
in Latin America and in some larger cities and urban airsheds in the
developed countries.
Trends in air quality development differ in respect of the four indicator
pollutants. In Europe, PM10 levels had decreased by the end of last century
but have tended to rise again, which may be partially explained by changing
weather conditions. Even though large Asian cities have seen a slight reduction
in PM10 levels over the last few decades, PM (PM10 and PM2.5) is still
the major air pollutant in Asia. Many of the large cities in Latin America, as
well as Mexico City, still experience high levels of PM.
Sulfur dioxide levels have fallen in most parts of the world, including
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