world cancer report - iarc

Air pollutant WHO Air Quality Guideline, Number of cities Population in those % of population in
annual average with data cities (millions) those cities exposed
above the AQG
Sulfur dioxide (SO 2) 50 µg/m 3 100 61 14%
Black smoke 50 µg/m 3 81 52 19%
Total suspended 60 µg/m 3 75 25 52%
particles
Table 2.11 The proportion of the population in Western European cities exposed to air pollutants at levels above the WHO Air Quality Guidelines (AQG), 1995.
problem. Engine combustion products
include volatile organic compounds (benzene,
toluene, xylenes and acetylene),
oxides of nitrogen (NOx) and fine particulates
(carbon, adsorbed organic material
and traces of metallic compounds). In
developing countries, outdoor air pollution
is likely to represent a greater public
health problem than in more developed
countries, because of poorly regulated
use of coal, wood and biomass (e.g. animal
dung, crop residues) for electricity
production and heating, in addition to
vehicle emissions in urban areas.
Although the proportion of global energy
derived from biomass fuels decreased
from 50% in 1900 to about 13% in 2000,
use of such fuels is now increasing in
some impoverished regions [5].
Human exposure to air pollution is nevertheless
hard to estimate. In a study based
on air monitoring and population data for
40 The causes of cancer
100 Western European urban areas, the
proportion of the population exposed
ranged from 14% to 52%, depending on
the indicator pollutant used (Table 2.11)
[6].
Numerous studies have compared residence
in urban areas, where air is considered
to be more polluted, to residence in
rural areas as a risk factor for lung cancer
[7]. In general, lung cancer rates were
higher in urban areas and, in some studies,
were correlated with levels of specific
pollutants such as benzo[a]pyrene, metals
and particulate matter, or with mutagenicity
of particulate extracts in bacterial
assay systems. Other studies have
attempted to address exposure to specific
components of outdoor air, providing risk
estimates in relation to quantitative or
semi-quantitative exposure to pollutants.
In general, these studies have provided
evidence for an increased risk of lung
cancer among residents in areas with
higher levels of air pollution. Table 2.12
summarizes the results of three of the
best designed studies (in particular these
studies controlled for the possible concomitant
effect of smoking): no matter
which pollutant is considered, the results
suggest a moderate increase in the risk of
lung cancer.
Localized air pollution may be a hazard in
relation to residence near to specific
sources of pollution, such as petroleum
refineries, metal manufacturing plants,
iron foundries, incinerator plants and
smelters. In general, an increased risk of
lung cancer in the proximity of pollution
sources has been demonstrated. In three
Scottish towns, for example, increased
lung cancer mortality occurred in the
vicinity of foundries from the mid-1960s to
the mid-1970s and later subsided in parallel
with emission reductions [8]. Similar
Study Population, follow-up Number Exposure range Contrast / Controls Relative risk of
of subjects lung cancer (95% CI)
Dockery et al. 6 Cities, USA, 8,111 FP 11-30 µg/m 3 Highest vs. lowest city FP: 1.37 (1.11 - 1.68)
1993 1974-91
Pope et al. 151 Areas, USA, 552,138 FP 9-33 µg/m 3 Highest vs. lowest FP: 1.03 (0.80 - 1.33)
1995 1982-89 Sulfur dioxide: areas Sulfur dioxide: 1.36
3.6-23 µg/m 3 (1.11 - 1.66)
Beeson et al. California, male non- 2,278 FP 10-80 µg/m 3 Increment based on FP: 5.21 (1.94 -13.99)
1998 smokers, 1977-82 Sulfur dioxide: 0.6-11 ppb interquartile range Sulfur dioxide: 2.66
Ozone 4-40 ppb (FP 24 µg/m 3 ; (1.62 - 4.39)
Sulfur dioxide 3.7 ppb; Ozone: 2.23 (0.79 - 6.34)
Ozone 2.1 ppb)
Table 2.12 Studies indicating an increased risk of lung cancer associated with exposure to atmospheric pollutants. FP = fine particles.