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

GLOBAL AMBIENT AIR POLLUTION CONCENTRATIONS AND TRENDS
Fig. 14. Monthly mean ozone concentrations measured at Zugspitze,
Germany since 1978
Concentration (ppb)
70
60
50
40
30
20
Source: Scheel (61).
1980 1985 1990
Year
1995 2000
Latin America
Many of the large cities in Latin America still experience high concentrations of
PM and secondary pollutants. The five million inhabitants of Santiago de Chile
are exposed to high levels of air pollution during a significant portion of the year.
Santiago ranks as one of the most polluted cities in the world. Air quality data, as
presented in Fig. 15, show that there was a slight fall in PM10 concentrations until
2001; since 2001 the levels have increased again.
A downward trend in sulfur dioxide levels is evident in large Latin American
cities such as Mexico City and São Paulo. In Mexico City, neither nitrogen
dioxide nor sulfur dioxide concentrations exceeded annual average limit values
after 2001. Nevertheless, ozone and PM still pose a severe problem in the city
(54).
Africa
In Africa, the high rate of urbanization (4–8% per year in a number of cities) that
is expected to be sustained for the next decade, combined with low-income solutions
to daily commuting, has resulted in a rapid increase in pollutants emitted
by motor vehicles. Low incomes have resulted in the importing of older used vehicles
in recent years, the use of cheap two-wheeled vehicles and cheap fuel, and
the postponement of vehicle maintenance.
In the greater Cairo area, there has been no statistically significant downward
trend in sulfur dioxide concentrations since measurements started in 1999, even
though levels fell between 1999 and 2001.
In South Africa, ambient levels of sulfur dioxide, nitrogen dioxide and ozone
do not show an upward trend. Owing to the lack of monitoring information,
however, it is difficult to be specific about numbers and impacts.
53