Polycyclic aromatic hydrocarbons (PAHs) are a complex
and important group of chemicals formed during
incomplete combustion of organic material. They are
widespread in the human environment; diet and tobacco
smoke are two important sources of exposure of PAHs.
A number of occupational settings entail exposure to
high level of PAHs. These chemicals, however, occur inevitably as complex mixtures of variable composition:
an assessment of the risk from individual PAHs is
therefore impossible. An increased risk of lung cancer
has been demonstrated in several industries and
occupations entailing exposure to PAHs such as
aluminium production, coal gasification, coke production,
iron and steel founding, tar distillation, roofing
and chimney sweeping (Boffetta et al., 1997). An
increase has also been suggested in a few other
industries, including shale oil extraction, wood impregnation,
road paving, carbon black production and
carbon electrode manufacture with an exposure–response
relationship in the studies with detailed exposure
information. Other cancers that have been definitely
associated with occupational exposure to PAHs are
those from the skin, in particular for coal-tar pitches,
coal-tars and untreated mineral oils, and the urinary
bladder, in particular following exposure to coal-tar
pitches and in aluminium and coal gasification workers
(Boffetta et al., 1997).
Motor vehicle and other engine exhausts represent an
important group of mixtures of PAHs, since they
contribute significantly to air pollution. The available
epidemiological evidence strongly suggests 40–50%
excess of lung cancer among those occupationally
exposed to diesel engine exhaust (Lipsett and Campleman,
1999). The evidence for other cancers is inadequate.
Data on other types of exhausts, including
gasoline engines, do not allow any conclusions (IARC,
1989).