world cancer report - iarc
world cancer report - iarc
world cancer report - iarc
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Fig. 2.37 Deliberate exposure to solar radiation in<br />
order to achieve a sun-tan.<br />
Internalized radionuclides that emit α-particles<br />
and β-particles are carcinogenic to<br />
humans. For most people, exposure to<br />
ionizing radiation from inhaled and tissuedeposited<br />
radionuclides is mainly from<br />
naturally-occurring radon-222. Exposure<br />
to thorium-232, which occurs in soil, is<br />
less common. Cancers associated with<br />
exposure to particular nuclides, usually<br />
in an occupational context, include lung<br />
<strong>cancer</strong>, bone sarcomas, liver <strong>cancer</strong>,<br />
leukaemia and thyroid <strong>cancer</strong>.<br />
The United Nations Scientific Committee<br />
on the Effects of Atomic Radiation [5] has<br />
estimated the lifetime risk of solid <strong>cancer</strong>s<br />
and of leukaemia following an acute<br />
Static direct current (DC) fields<br />
0<br />
Frequency (Hz)<br />
Wavelength (m)<br />
Extremely low<br />
frequencies (ELF)<br />
Superconducting<br />
DC magnets (MRI)<br />
Photon energy (eV)<br />
3x102<br />
Electromagnetic fields and radiation<br />
Fig. 2.38 The spectrum of electromagnetic fields and their use in daily life.<br />
10 6<br />
Mains power<br />
transmission,<br />
distribution<br />
1.2x10 -12<br />
VDUs<br />
and<br />
TVs<br />
whole-body exposure to γ radiation,<br />
together with the corresponding estimated<br />
numbers of years of life lost per radiation-induced<br />
case (Table 2.17). The current<br />
recommendations of the<br />
International Commission for Radiological<br />
Protection are to limit exposures to the<br />
general public to 1 mSv per year, and<br />
doses to workers to 100 mSv over 5<br />
years [6] (1 Sievert equals 1 joule per<br />
kilogram).<br />
Ultraviolet radiation<br />
The major source of human exposure to<br />
ultraviolet radiation is sunlight.<br />
Approximately 5% of the total solar radiation<br />
received at the surface of the<br />
earth is ultraviolet [7]. Intensity of solar<br />
terrestrial radiation varies according to<br />
geography, the time of day and other<br />
factors. The level of skin exposure to<br />
sunlight depends on many parameters<br />
including cultural and social behaviour,<br />
clothing, the position of the sun and the<br />
position of the body. Few measurements<br />
of personal exposure have been<br />
<strong>report</strong>ed. Artificial sources of ultraviolet<br />
radiation are common and such<br />
devices are used to treat a number of<br />
diseases (e.g. psoriasis) as well as for<br />
cosmetic purposes.<br />
3x10 5<br />
10 3<br />
Radiofrequencies<br />
(VLF-VHF)<br />
1.2x10 -9<br />
Broadcast<br />
AM FM TV<br />
3x108<br />
10 0<br />
Microwaves<br />
(UHF-EHF)<br />
Mobile phones<br />
1.2x10 -6<br />
3x10 11<br />
10 -3<br />
1.2x10 -3<br />
Optical radiation<br />
Infrared<br />
Cancer causation<br />
Solar radiation, and specifically the ultraviolet<br />
component of it, causes cutaneous<br />
malignant melanoma and non-melanocytic<br />
skin <strong>cancer</strong> (Fig. 2.39). Exposure of skin<br />
to ultraviolet radiation causes DNA damage<br />
(Carcinogen activation and DNA<br />
repair, p89) and also the conversion of<br />
trans-urocanic acid to cis-urocanic acid,<br />
which leads to cell injury and ultimately to<br />
<strong>cancer</strong>. Incidence of skin <strong>cancer</strong> is<br />
increasing rapidly among fair-skinned<br />
populations [7] (Melanoma, p253). In<br />
Canada, for example, occurrence of this<br />
disease has doubled over the past 25<br />
years. IARC has estimated that at least<br />
80% of all melanomas are caused by exposure<br />
to sunlight. Non-melanocytic skin<br />
<strong>cancer</strong>, which includes basal cell carcinoma<br />
and squamous cell carcinoma, is the<br />
most prevalent human malignancy: more<br />
people are living with this <strong>cancer</strong> than any<br />
other. In the USA and Australia, one of<br />
every two new <strong>cancer</strong>s diagnosed is a<br />
non-melanocytic skin <strong>cancer</strong>. Use of sunlamps<br />
and sunbeds probably causes skin<br />
melanomas in humans.<br />
Electromagnetic fields<br />
Recent years have seen an unprecedented<br />
increase in the number and diversity of<br />
CO 2 laser<br />
3x10 14<br />
10 -6 10 -9 10 -12<br />
1.2x10 0<br />
Ultraviolet<br />
Visible<br />
3x10 17<br />
Ionizing radiation<br />
X-and gamma radiation<br />
1.2x10 3<br />
Diagnostic X-rays<br />
3x10 20<br />
1.2x10 6<br />
Radiation 53