Download La Medicina del Lavoro

La Medicina
Meci
Lav 2006;del
97, Lavoro
2:
Health risks of exposure to non-ionizing radiationMyths or
science~based evidence
MAILA HIETANEN
Finnish Institute of Occupational Health, Helsinki, Finland
KEYWORDS
Non-ionizing radiation; UV radiation; EM fields
SUMMARY
Introduction: The non-ionizing radiation (NIR) contains large range of
wavelengths and frequencies fOi um ultraviolet (UV) radiation to static electric
and magnetic jields. Biological effects of electromagnetic (EA ation depend
greatly on wavelength and other physical parameters. Optical radiation: The
Sun is the most cant source of environmental UVexposure, so that outdoor
workers are at risk· of chronic over-exposure. Al sure to short-wave visible
light is associated with the aging and degeneration of the retina. Especially ha
are laser beams focused to a small spot at the retina, resulting in permanent
visual impairment. Electrom fields: Exposure to EM jields induces body
currents and energy absorption in tissues, depending on frequen coupling
mechanisms. Thermal effects caused by temperature rise are basically
understood, whereas the challe understand the suspected non-thermal effects.
Radiofrequency (RF) jields around frequencies of 900 M 1800 MHz are of
special interest because of the rapid advances in the telecommunication
technology. The fit of these sources are so low that temperature rise is
unljkely to explain possible health effects. Other mechanisr. teraction ha ve
been proposed, but biological experiments ha ve failed to conjirm their
existence.
RIASSUNTO
«Rischi per la salute dovuti all'esposizione a radiazioni non ionizzanti:
mito o evidenza scientijica?». L zioni non ionizzanti (NIR) contengono una
vasta gamma di lunghezze d'onda e frequenze che vanno dall zioni
ultraviolette (UV) nel vuoto a campi statiei, elettrici e magnetici. Cii effetti
biologici delle radiazioni eli gnetiche (EM) dipendono molto dalla lunghezza
d'onda e da altri parametri jisici. Radiazioni ottiche: II maggiore sorgente di
esposizione ambientale ai raggi UV, cosicchi i lavoratori all'aperto sono a
rischio di sov zione cronica. Anche l'esposizione alia luce visibile ad onda corta
e associata all'invecchiamento e alia degen della retina. In particolare i pericoli
sono i raggi laser concentrati in una piccola zona sulla retina, che esita; danno
permanente della visione. Campi elettromagnetici: L'esposizione a campi
elettromagnetici determina corporee ed assorbimento di energia nei tessuti la
cui entita dipende dalie frequenze e dai meccanismi di accopp Cii effetti
termici causati da aumenti di temperatura sono sostanzialmente noti, mentre
la sfida e di capire i j effetti non termici. 1 campi delle radiifrequenze attorno a
frequenze di· 900 MHz e di 1800 MHz sono di pc interesse per il rapido
progresso della tecnologia nelle telecomunicazioni. Ilivelli dei campi di queste
sorgenti bassi che il rialzo della temperatura e poco probabile che possa
spiegare i possibili effetti sulla salute. Sono statl altri meccanismi di
interazione, ma gli esperimenti biologici sono poco validi per confirmare la loro
esistenza.
Correspondence: Maila Hietanen, Finnish Institute of Occupational Health,
Topeliuksenkatu 41 a A, FI-00250 Helsinki, E-mail: [email protected]
HEALTH RlSKS OF NON-IONIZING RADIATION
185
INTRODUCTION
The non-ionizing radiation (NIR) spectrum contains a large range of
wavelengths and frequencies from vacuum ultraviolet (UV) radiation to static
electric and magnetic fields. Biological effects of NIR depend greatly on
wavelength, frequency and other physical parameters, with a variety of consequences for exposed human beings. Various categories ofNIR are separated,
basically reflecting different biologic al interactions. Optical radiation consists of
UV, visible and infrared (IR) radiation. The other parts of the NIR spectrum
contain static electric and magnetic fields, extremely low frequency (ELF) and
low frequency (LF) electromagnetic (EM) fields and radiofrequency (RF) radiation. Except for visible radiation, i.e. light, NIR is invisible to the human eye
and not perceived by other senses at typical occupational exposure levels.
HEALTH RISKS OF OPTICAL RADIATION
Exposure to NIR has a variety of potential consequences for a human being.
To begin with optical radiation, severely burned people, mostly young women,
every summer need medical help after over-exposure to the Sun. Although
the painful erythema ('sunburn') will fade gradually after a few days, recurrent
over-exposures may still cause serious late effects. Chronic UV exposure has
been indicated to be the primary factor in the induction of non-melanocytic
skin cancers (NMSC). In addition, epidemiological studies on cutaneous
melanoma suggest that UV erythema may be of particular importance in its
initiation (9). Despite the high incidence, NMSC is usually diagnosed at an
early stage and the mortality rate is relatively low compared with that of
melanoma. The risk of developing skin cancer varies greatly with skin type,
and persons who readily sunburn are also more prone to develop skin cancer.
Skin cancer of fair-skinned individuals is increasing at an alarming rate (4-6%
per year) around the world (4). In USA, for example, skin cancers are the most
common type of cancer, with about 1.3 million new cases each year (2).
An unprotected eye exposed to direct UV radiation from the Sun or to
reflected UV from snow may accumulate a sufficient dose to cause hazardous
effects on the cornea, called photokeratitis. As with erythema of the skin, the
symptoms are delayed for several hours. Within a few hours overexposure to
UV radiation gradually gives rise to symptoms from a feeling of itchiness, 'sand
in the eye' sensation, increased tearing, to severe pain and photophobia. The
condition is referred to as 'snowblindness' or 'welders flash', depending on the
source of exposure (12).
In addition to corneal injury, epidemiological data shows an increased risk of
cortical cataract with UV exposure (1). In the unusual situation where the UV
absorbing lens or lens implant are not present, retinal injury is also possible for
wavelengths over 300 nm (9). The global prevalence of blinding cataracts
exceeds 50 million, and the prevention and slowing of the progress of lenticular
opacities should be an important objective in occupational health activities.
Though the intensity of the solar UV radiation depends on latitude, being the
highest at the Equator, it is worthwhile to note some peculiarities concerning
conditions in high geographicallatitudes. In summer, the daily duration of
sunlight is very long and the height of the Sun predominantly low, so that it is
difficult to avoid looking at it. In winter, the main contributing factor to the UV
exposure is the reflection from snow and ice. Under these conditions, safe UV
exposure limits can be easily exceeded without eye protection (11). Hence,
outdoor workers, such as fishermen, merchants at marketplaces, and road
constructors are at risk of chronic over-exposure to solar UV radiation.
As for the adverse effects of visible radiation on the eye, there are numerous
epidemiological studies indicating that chronic exposure to short-wave light, so
called blue-light, is a contributing factor to aging and degeneration of the
retina. Several studies have revealed that the shorter the wavelength, the
more severe the ocular photochemical damage. Fortunately, the human eye is
protected by the aversion reflex against hazardous light sources (11).
Therefore, it is difficult to look at the sun when it is high and bright, hence
being dangerous for the retina. The amount and the spectral distribution of
the solar radiation changes with the height of the Sun, so that comfortable
and safe viewing of it is possible only at angles of less than a few degrees a moment after the sunrise or before the sunset.
Though the eyelids normally close at exposure to sudden bright light, this
aversion response is too slow in some special situations. Especially hazardous are coherent laser beams that are focused to a small spot at the
retina, resulting in permanent visual impairment (12).
These examples clearly indicate that health hazards of high exposure to
optical region of NIR are science-based and incontestable. Therefore, workplace campaigns emphasizing importance of individual responsibility and
necessity of personal protection should be part of occupational health education. However, it should be also noted that other adverse effects, e.g.
increasing prevalence of multiple sclerosis and type 1 diabetes in higher
latitudes, have been associated with low sun exposure and vitamin D
deficiency (l0).
HEALTH RISKS OF ELECTROMAGNETIC FIELDS
Correspondingly to optical radiation, people in technically developed
countries are surrounded by ELF and RF electromagnetic fields. Natural
background EM fields are several orders lower than those emitted by
human-made sources, so that most occupational exposure is caused by
sources that emit EM fields either intentionally or as byproducts (13).
Whole-body or localized exposure to EM fields induces body currents and
energy absorption in tissues, depending on specific frequencies and
coupling mechanisms (8). Thermal effects caused by local or whole-body
temperature rise are obvious and basically understood, whereas the
principal scientific challenge is to reveal and understand the suspected or
hypothesized non-thermal effects. For instance, as a matter of a scientific
mystery, some occupationally or non-occupationally exposed persons in
various countries claim to experience unpleasant feelings during or after
exposure to EM fields. Typical hypersensitive reactions and symptoms are
described as headache, dizziness, fatigue and nausea. These sensations are not regarded pathological, but they
may seriously affect the physical or mental wellbeing of such persons.
In 2002, International Agency for Risk of Cancer (IARC) classified ELF
magnetic fields as a possible human carcinogen (Class 2B), based on the
risk of leukaemia in children living near electric power transmission lines
(5). Exposure to ELF magnetic fields has also been associated with several
other end-points, such as increased risk of brain cancer, breast cancer,
heart disease, and Alzheimer's disease, but these associations are
speculative and not confirmed.
At present, RF fields around frequencies of 900 MHz and 1800 MHz are of
special interest because of the rapid advances in the telecommunication
technology. As a result of the global expansion of the use of hand-held
cellular phones, RF exposure is becoming ubiquitous, and the focus of public interest has moved from power lines to mobile telephones and base
station antennas. The levels of these emissions are so low that the
mechanism of temperature rise is unlikely to explain the alleged adverse
health effects. Non-thermal mechanisms of interaction have been proposed,
but biological and human experiments have failed to confirm their existence
(7).
WHO's INTERNATIONAL EMF PROJECT
Several international bodies have realized the necessity of expanding
interest in the RF radiation research in order to identify the gaps in
scientific knowledge. For example, the World Health Organization (WHO)
acknowledges that EM fields represent one of the fastest growing
environmental factors, spreading anxiety and speculation also among
working population. Ten years ago, the WHO launched an International EMF
Project for providing independent scientific assessments of health effects
from exposure to EM fields. The Project has encouraged setting of
internationally accessible guidelines and standards for exposure limits and
device emissions. It has also provided information on risk perception, risk
communication and risk management of the EM fields (14).
186
HIETANEN retina. The amount and the spectral distribution of the solar
radiation changes with the height of the Sun, so that comfortable and safe
viewing of it is possible only at angles of less than a few degrees - a
moment after the sunrise or before the sunset.
Though the eyelids normally close at exposure to sudden bright light, this
aversion response is too slow in some special situations. Especially hazardous are coherent laser beams that are focused to a small spot at the
retina, resulting in permanent visual impairment (12).
These examples clearly indicate that health hazards of high exposure to
optical region of NIR are science-based and incontestable. Therefore, workplace campaigns emphasizing importance of individual responsibility and
necessity of personal protection should be part of occupational health education. However, it should be also noted that other adverse effects, e.g.
increasing prevalence of multiple sclerosis and type 1 diabetes in higher
latitudes, have been associated with low sun exposure and vitamin D
deficiency (l0).
HEALTH RISKS OF ELECTROMAGNETIC FIELDS
Correspondingly to optical radiation, people in technically developed
countries are surrounded by ELF and RF electromagnetic fields. Natural
background EM fields are several orders lower than those emitted by
human-made sources, so that most occupational exposure is caused by
sources that emit EM fields either intentionally or as byproducts (13).
Whole-body or localized exposure to EM fields induces body currents and
energy absorption in tissues, depending on specific frequencies and
coupling mechanisms (8). Thermal effects caused by local or whole-body
temperature rise are obvious and basically understood, whereas the
principal scientific challenge is to reveal and understand the suspected or
hypothesized non-thermal effects. For instance, as a matter of a scientific
mystery, some occupationally or non-occupationally exposed persons in
various countries claim to experience unpleasant feelings during or after
exposure to EM fields. Typical hypersensitive reactions and symptoms are
described as headache, dizziness, fatigue and nausea. These sensations are
not regarded pathological, but they may seriously affect the physical or
mental wellbeing of such persons.
In 2002, International Agency for Risk of Cancer (IARC) classified ELF
magnetic fields as a possible human carcinogen (Class 2E), based on the
risk of leukaemia in children living near electric power transmission lines
(5). Exposure to ELF magnetic fields has also been associated with several
other end-points, such as increased risk of brain cancer, breast cancer,
heart disease, and Alzheimer's disease, but these associations are
speculative and not confirmed.
At present, RF fields around frequencies of 900 MHz and 1800 MHz are of
special interest because of the rapid advances in the telecommunication
technology. As a result of the global expansion of the use of hand-held
cellular phones, RF exposure is becoming ubiquitous, and the focus of public interest has moved from power lines to mobile telephones and base
station antennas. The levels of these emissions are so low that the
mechanism of temperature rise is unlikely to explain the alleged adverse
health effects. Non-thermal mechanisms of interaction have been proposed,
but biological and human experiments have failed to confirm their existence
(7).
WHO's INTERNATIONAL EMF PROJECT
Several international bodies have realized the necessity of expanding
interest in the RF radiation research in order to identify the gaps in
scientific knowledge. For example, the World Health Organization (WHO)
acknowledges that EM fields represent one of the fastest growing
environmental factors, spreading anxiety and speculation also among
working population. Ten years ago, the WHO launched an International EMF
Project for providing independent scientific assessments of health effects
from exposure to EM fields. The Project has encouraged setting of
internationally accessible guidelines and standards for exposure limits and
device emissions. It has also provided information on risk perception, risk
communication and risk management of the EM fields (14).
HEALTH RlSKS OF NON-IONIZING RADIATION
187 THE ROLE OF ICNIRP IN HEALTH RISK ASSESSMENT
The principal scientific organization supporting the work by WHO is the
International Commission on Non - Ionizing Radia tion Protection (ICNIRP). The
main activity of ICNIRP is to provide guidance on safe exposure and protection
of workers and members of the public by issuing statements and
recommendations. ICNIRP monitors continuously and periodically carries out
critical reviews of the scientific literature concerned with the sources and
possible biological and adverse health effects of NIR. ICNIRP performs critical
scientific analysis by evaluating the relevance, scientific quality and credibility
of each report (6).
The exposure limits developed by ICNIRP are intended to protect against
diseases and other adverse health effects. Because risk assessment is focused
to humari health, ICNIRP prefers the data derived from human studies. The
relationship between exposure and certain short-term biological effects can be
evaluated from human laboratory studies, whereas data on long-term human
effects can only be derived from epidemiological studies. However, the
epidemiological studies are not considered sufficient to provide evidence of
caus al relationships without biological data from experimental studies.
In its exposure guidelines, ICNIRP defines occupational and public exposures
in general terms. When applying the guidelines to specific situations, it is
ICNIRP's opinion that authorities in each country should decide on whether
occupational or general public guideline levels are to be applied, according to
existing national rules or policies.
EUROPEAN DIRECTIVE ON WORKERS' EM FIELD EXPOSURE
In Europe, it has been considered necessary to introduce specific measures
protecting workers from the risks associated with EM fields. Therefore, a new
Directive given by the European Commission and Council was published in
2004 (3). Similar to ICNIRP's philosophy, this Directive refers to the health
risks of workers due to known short-term adverse effects caused by the
circulation of induced currents and by energy absorption as well as by contact
currents. Hence, it does not address suggested long-term effects, including
possibIe carcinogenic effects, stating that there is no conclusive scientific
evidence establishing a causal relationship.
REFERENCES
1. BALASUBRAMANIAN D: Ultraviolet radiation and cataract. J Ocular
Pharmacol Therap 2000; 88: 329-344
2. BENvENUTo-ANDRADE C, ZEN B, FONSECA G, et al:
Sun exposure and sun protection habits among highschool adolescents in
Porto Alegre, Brazil. Photochem Photobiol2005; 81: 630-635
3.Directive of the European Parliament and of the CounciI on the minimum
health and safety requirements regarding the exposure of workers to the
risks arising from physical agents (electromagnetic fields) (2004/40/EC).
Official Journal of the European Union 2004; L 184: 1-9
4. GODAR DE: UV doses worldwide. Photochem Photobio12005; 81: 736-749
5. INTERNATIONAL AGENCY FOR RESEARCH ON CANCER:
Static and extremely low-Jrequency (ELF) electric and magnetic jields. Lyon:
IARC, 2002 (IARC Monographs on non-ionizing radiation no 80)
6. INTERNATIONAL COMMISSION ON NON-IONIZING RADIATION PROTECTION
(ICNIRP): General approach to protection against non-ionizing radiation.
Health Physics 2002; 82: 540-548
7. INTERNATIONAL EXPERT GROUP ON MOBILE PHONES:
Mobile phones and health. IEGMP, 2000. (Report of an Independent Expert
Group on Mobile Phones). ISBN 0-85951-450-1
8. NATIONAL RAmOLOGICAL PROTECTION BOARD: Advice on limiting exposure
to electromagnetic jields (0-300 GHz). Chilton, UK: Documents of the NRPB
2004: 15 (2)
9. NATIONAL RADIOLOGICAL PROTECTION BOARD:
Health effects Irom ultra violet radiation. Chilton, UK:
Documents of the NRPB 2002: 13 (1)
10.PONSONBY AL, LUCAs RM, VAN DER MEI AF: UVR, Vitamin D and three
autoimmune diseases - Multiple sclerosis, type 1 diabetes, rheumatoid
arthritis. Photochem Photobiol2005; 81: 1267-1275