world cancer report - iarc

sources of electromagnetic fields [8], principally
extremely low frequency and
radiofrequency fields. Such sources
include all equipment using electricity, television,
radio, computers, mobile telephones,
microwave ovens, anti-theft gates
in large shops, radars and equipment used
in industry, medicine and commerce.
Static fields and extremely low frequency
fields occur naturally, and also arise as a
consequence of the generation and transmission
of electrical power and through
Immune suppression
Cytokine release
Langerhans cell depletion
Local/ systemic responses
54 The causes of cancer
UV
trans UCA cis UCA
Lifetime risk Number of years of life lost
per case
0.2 Sv 1 Sv 0.2 Sv 1 Sv
Solid cancers 2.4% 10.9% 11.2 11.6
Leukaemia 0.14% 1.1% 31 31
Table 2.17 Estimated risk of cancer following acute whole-body exposure to gamma radiation at two
dose levels.
DNA
DNA damage
Genetic mutations
Tumour suppressor gene
inactivation
p53
patched, Shh
Proto-oncogene
H-RAS, K-RAS, N-RAS
the operation of a range of industrial
devices and domestic appliances, the latter
often at a greater field intensity.
Exposure to extremely low frequency fields
is mainly from human-made sources for
the generation, transmission and use of
electricity. Occupational exposure occurs,
for example, in the electric and electronics
industry, in welding and in use and repair
of electrical motors. Environmental exposure
to extremely low frequency fields
occurs in residential settings due to prox-
Cell cycle arrest
DNA repair
(p53, p21)
Abnormal cell proliferation Normal cell proliferation
TUMORIGENESIS
Epidermis
Unrepaired DNA damage
Sunburn cells
Apoptosis
(Fas, Fas-L, Bax)
Fig. 2.39 Pathways implicated in the induction of non-melanoma skin cancer by ultraviolet radiation
(UCA = urocanic acid).
imity to electricity transmission lines and
use of electric appliances. Levels of exposure
from many environmental sources are
typically low [9].
Exposure to radiofrequency radiation can
occur in a number of ways. The primary
natural source of radiofrequency fields
is the sun. Man-made sources, however,
are the main source of exposure.
Radiofrequency fields are generated as a
consequence of commercial radio and
television broadcasting and from
telecommunications facilities (Table
2.16). Radiofrequency fields in the home
are generated by microwave ovens and
burglar alarms. Mobile telephones are
now, however, the greatest source of
radiofrequency exposure for the general
public.
In respect of the work environment,
employees working in close proximity to
radiofrequency-emitting systems may
receive high levels of exposure. This
includes workers in the broadcasting,
transport and communication industries,
and in antenna repair, military personnel
(e.g. radar operators) and police officers
(utilizing traffic control radars). There
are also industrial processes that use
radiofrequency fields and these include
dielectric heaters for wood lamination
and sealing of plastics, industrial induction
heaters and microwave ovens, medical
diathermy equipment to treat pain
and inflammation of body tissues, and
electrosurgical devices for cutting and
welding tissues.
Cancer causation
Several expert groups have recently
reviewed the scientific evidence concerning
the carcinogenicity of extremely low
frequency fields e.g. [9,10]. A number of
epidemiological studies on childhood
leukaemia indicate a possible relationship
between risk and exposure to extremely
low frequency fields. Studies of adult cancers
following occupational or environmental
exposures to extremely low frequency
fields are much less clear. There is
little experimental evidence that these
fields can cause mutations in cells.
Mechanistic studies and animal experiments
do not show any consistent positive