Health Risk of Radiofrequency Radiation Toxicological and Laboratory Studies

1
Health Risk of Radiofrequency RadiationToxicologi
cal and Laboratory Studies

• Riadh W. Y. Habash, PhD, P.Eng
• McLaughlin Centre for Population Health Risk
  Assessment, Institute of Population Health
• School of Information Technology and Engineering
• University of Ottawa
• rhabash_at_site.uottawa.ca

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The electromagnetic (EM) field is a physical
influence (a field) that permeates through all of
space, and which arises from electrically charged
objects and describes one of the four fundamental
forces of nature, electromagnetism.
Electromagnetism is found almost everywhere. All
EM fields are force fields, carrying energy and
capable of producing an action at a distance.
These fields have characteristics of both waves
and particles. This energy is utilized in various
ways, though we still lack the full understanding
of its fundamental properties. Many inventions
of the late twentieth century, ranging from
everyday home and office appliances to satellite
systems and mobile phones, are so important and
so advantageous we wonder how we ever lived
without them.
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General

• EM waves at low frequencies are referred to as EM
  fields and at very high frequencies are called EM
  radiation. The term EM field is generally used
  rather than EM radiation whenever wavelengths
  greatly exceed distances from exposure sources.
• EM fields at all frequencies make one of the most
  common environmental issues, about which there is
  a growing concern and speculation. EM fields are
  present everywhere in our environment but are
  invisible to the human eye.
• All populations are now exposed to varying
  degrees of EM fields, and the levels will
  continue to increase as technological inventions
  advance. These inventions have become an integral
  part of our modern life. We just need to know
  that they are safe.

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Sources of RF Radiation (100 kHz-300 GHz)

• Broadcast (AM and FM) and TV (? 0.1 W/m2)
• Mobile Phones and cordless phones (? 0.1 W/m2)
• Microwave Ovens (? 0.5 W/m2)
• Civil and Military Radar Systems
• Portable and Radio Transceivers (? 0.2 W/m2)
• Medical and Industrial Applications
• Anti-theft Devices
• New Technologies like Worldwide Interoperability
  for Microwave Access (WiMax)

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Bioeffects?

• A biological effect occurs when a change in the
  environment causes some noticeable or detectable
  physiological change in a living system. These
  changes are not necessarily harmful to health.
  For example, listening, reading, eating or
  playing will produce a range of bioeffects.
  However, none of these activities is expected to
  cause health effects.
• The body has sophisticated mechanisms to adjust
  to the various influences that encounter in the
  environment.
• But the body does not possess adequate
  compensation mechanisms for all bioeffects.
  Changes that stress the biosystem for long time
  may lead to a health effect.

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Biological and Health Effects

• Cells and Membranes
• Tissues
• Changes in Protein Conformation
• Changes in Binding Probability
• Absorption of Vibrational States of Biological
  Components
• Genetic Material
• Carcinogenesis
• Hypothesis of Melatonin
• Cancer
• Brain and Nervous System

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Mechanisms for (RF) Radio Frequency Radiation

• Biological effects due to exposure to EM
  radiation are often referred to as being thermal
  or nonthermal/athermal.
• Heating is the primary interaction of EM
  radiation at high frequencies especially above
  about 1 MHz. Thermal effects of EM radiation
  depend on the specific absorption rate (SAR)
  spatial distribution.
• Controversy surrounds issues regarding bioeffects
  of intermediate- and low-level EM radiation.
  First, whether the radiation at such low levels
  can cause harmful biological changes in the
  absence of demonstrable thermal effects. Second,
  whether effects can occur from EM radiation when
  thermoregulation maintains the body temperature
  at the normal level despite the EM energy
  deposition.

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RF Exposure Guidelines SAR limits for RFR
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Epidemiological StudiesWhat is Already Known so
Far?

• The epidemiologic evidence is not strong enough
  to the level required to conclude that RF
  radiation are a likely cause of one or more
  types of human cancer. This is attributed to weak
  design of the studies, lack of detail on actual
  exposures, limitations of the ability of studies
  to deal with other likely factors, and in some
  cases there might be biases in the data used.
• The current epidemiologic evidence justifies
  further research to clarify the situation.
  Moreover, since there are only a few
  epidemiological studies that examine the health
  risks associated with exposure to RF radiation,
  research at the cellular and animal level is
  needed to better understand this relationship.

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Laboratory Studies Cellular and Animal

• Cellular studies play a supporting task in health
  risk assessment. Cellular model systems are good
  candidates for testing the plausibility of
  mechanistic hypotheses and investigating the
  ability of RF radiation to have synergistic
  effects with agents of known biological activity.
  They are significant to the optimal design of
  animal and epidemiological studies.
• On the other hand, animal studies are used when
  it is unethical or impossible to perform studies
  on humans and have the advantage that
  experimental conditions can be thoroughly
  controlled.

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Thermal and Non-thermal Effects

• Close to the high-power transmitter,
  high-frequency fields may be harmful to human
  beings by producing thermal effects that may
  sometimes, when thermoregulation processes are
  insufficient, produce irreversible damage (for
  example, cataract). This kind of effect is well
  known from animal experiments and for that reason
  does not constitute a particular health problem,
  as measures can be taken to prevent excessive
  exposure.
• Also low-level exposures leading to non-thermal
  effects are, at least according to certain
  investigators, possible. Non-thermal effects have
  been reported in cell cultures and animals, in
  response to exposure to low-level fields. They
  are not well established and therefore highly
  controversial.

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Chain of Events Leading from RF exposure to
Disease
RF radiation
Interaction RF force induce currents
Transduction Modify tissues and membranes or ion
currents Not perceptible by cells No
amplification triggered
Cell Signal Signal cascade or amplification Signa
l within normal variation No functional
consequences
Biological Response Changes in cell
behavior Sensory effects Neutral effects No
adverse effects
Cell Dysfunction Adverse Effects Progress
Toward Disease Transient Reversible .. No
effect Repair adaptation .. No effect With
reserve capacity .. No effect
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Cancer!

• There are no laboratory studies in humans with
  cancer as the direct end point of investigation.
• Carcinogen activity could be identified by
• Evidence from human populations, including
  epidemiology, clinical studies, and case reports.
• Animal studies.
• Cellular (in vitro) studies and studies of
  biophysical and biochemical mechanisms.
• As a useful concept for assessing risk,
  scientists and regulatory agencies have generally
  divided carcinogens into two types genotoxic and
  non-genotoxic (epigenetic).

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Genotoxicity and Non-genotoxic Carcinogens

• Genotoxicity does have a clear cancer endpoint or
  any other adverse health outcome, however, there
  is the possibility that genotoxic effects on
  cells might lead to adverse health effects such
  as cancer or other diseases. Studies in this
  regard have been performed at a variety of levels
  including damage to DNA in vitro or in vivo,
  damage to chromosomes, induction of sister
  chromatid exchange (SCE), or induction of
  mutations.
• Non-genotoxic carcinogens do not directly damage
  the genetic material of cells. Rather, they
  affect carcinogenesis indirectly by increasing
  the probability that other agents will cause
  genotoxic injury or that genotoxic injury caused
  by other agents will lead to cancer.

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Genotoxicity (In Vivo) StudiesWhat is Already
Known so Far?

• The in vivo experiments by Lai and Singh
  (1995,1996) are special, in view of the attention
  they have received. They reported an increase in
  DNA strand breaks in the brain cells of rats
  exposed for two hours to pulsed or CW 2450 MHz RF
  fields at averaged whole body SARs of 0.6 and 1.2
  W/kg. In 1997, they found that melatonin, and
  another compound known to be a free radical
  scavenger, blocked the RF effect of increased DNA
  strand breaks. They have also reported that a
  temporally incoherent magnetic field (noise)
  blocked RF-induced increases in DNA strand breaks
  (Lai and Singh, 2004).
• Diem (2005) reported that exposure to 1800 MHz RF
  radiation was associated with DNA strand breaks
  in human and rat cells.
• Malyapa (1997) could not replicate Lai and
  Singh's results at 2450 MHz or at a frequency of
  835/847 MHz. Lagroye (2004), using methods
  identical to those of Lai and Singh, could find
  no evidence that pulsed-wave 2450 MHz RF produced
  DNA damage in rat brain cells. Hossmann and
  Hermann (2003) suggest that the experiments by
  Lai and Singh used peak power that was much
  higher than the mean power, which may have
  accounted for the observed DNA damage.
• Vijayalaxmi (2003) found no evidence of
  genotoxicity in rats exposed for 2 years to
  near-field RF exposure.

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Genotoxicity (In Vivo) Studies

• Repacholi et al. (1997) have induced a two-fold
  increase in lymphoma incidence in a strain of
  lymphoma-prone transgenic mice following daily
  exposure ( 2 ? 30 min) up to 18 months to 900 MHz
  radiation with a signal similar to the GSM
  modulation ( pulse repetition frequency of 217 Hz
  and a pulse width of 0.6 ms). Utteridge et al.
  (2002) and Oberto et al. (2007) failed to
  replicate or confirm the above results.
• Several other studies have evaluated the
  carcinogenicity of RF fields at nonthermal levels
  in various models. Many studies have tested
  whether RF radiation alone induce any kind of
  cancer in normal or genetically predisposed
  animals, and other studies investigated whether
  exposure to RF radiation could enhance the
  development of tumors induced by chemical
  carcinogens, X-ray, or UV radiation. No
  significant increase of tumor incidence has been
  reported in any of these studies.

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Genotoxicity (In Vitro) Studies

• In vitro studies in general have failed to show
  evidence of DNA damage (Malyapa 1997 Vijayalaxmi
  2000, 2001, 2006 Gos, 2000 Roti Roti, 2001
  Maes, 2001, Lagroye, 2004, Hook, 2004, Zeni,
  2005, Sakuma, 2006, Stronati, 2006).
• Tice et al. (2002) found an increased frequency
  of micronucleated lymphocytes exposed to
  different RF signals for 24 hours at an average
  SAR of 5.0 W/kg or 10 W/kg. Micronuclei arise
  from chromosomal damage. Others have found an
  increased frequency of micronucleated cells
  following exposure to RF signals (Garaj-Vrhovac,
  1991 Maes, 1995 d'Ambrosio 2002 Trosic 2002).
  Zotti-Martelli (2005) also found an increase in
  micronuclei in lymphocytes exposed to 1800 MHz at
  different power densities and for different time
  periods, but also found a wide inter-individual
  variability in the response. However, Vijayalaxmi
  (2001, 2006) Bisht (2002) and McNamee (2002
  2003), Zeni (2003), Gorlitz (2005), Scarfi (2006)
  and Juutilainen (2007) did not find an icrease in
  micronucleated cells after RF exposure.

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Genotoxicity (In Vitro) Studies

• In vitro studies in general have failed to show
  evidence of DNA damage (Malyapa 1997 Vijayalaxmi
  2000, 2001, 2006 Gos, 2000 Roti Roti, 2001
  Maes, 2001, Lagroye, 2004, Hook, 2004, Zeni,
  2005, Sakuma, 2006, Stronati, 2006).
• It is possible that certain cellular constituents
  altered by exposure to RF radiation, such as free
  radicals, indirectly affect DNA.
• Much of the in-vitro work focused on genotoxic
  effects. Few studies indicated genotoxic effects
  from RF radiation. Those studies should be
  followed up.
• In most studies, the genetoxic effect have been
  investigated after short-term exposure (Moulder
  et al., 1999, Vijayalaxmi and Obe, 2004).

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Reviews

• In a review, Verschaeve and Maes 1998 concluded
  that According to a great majority of papers,
  RF fields, and mobile telephone frequencies in
  particular, are not genotoxic they do not induce
  genetic effects in vitro and in vivo, at least
  under nonthermal conditions, and do not seem to
  be teratogenic (cause birth defects) or to induce
  cancer.
• The Royal Society of Canada Expert Panel Report
  1999, 2001, 2007 reviewed the subject and
  concluded that A large number of laboratory
  studies of the potential health effects of RF
  fields have focused on genotoxicity, including
  studies of tumorigenesis, promotion, progression,
  altered cell proliferation, and DNA damage. The
  great majority of these studies have failed to
  demonstrate genotoxic effects due to exposure to
  RF fields.

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• The UK Independent Expert Group on Mobile Phones
  (IEGMP) 2000 summarized the situation as
  follows The balance of evidence, from both in
  vitro and in vivo experiments, indicates that
  neither acute nor chronic exposure to RF fields
  increased mutation or chromosomal aberration
  frequencies when temperatures are maintained
  within physiological limits. This suggests that
  RF exposure is unlikely to act as a tumor
  initiator.
• Meltz 2003 reviewed the in vitro literature
  pertinent to the issue of the possible induction
  of toxicity, genotoxicity, and transformation of
  mammalian cells due to RF exposure. The author
  concludes The weight of evidence available
  indicates that, for a variety of frequencies and
  modulations with both short and long exposure
  times, at exposure levels that do not (or in some
  instances do) heat the biological sample such
  that there is a measurable increase in
  temperature, RF exposure does not induce (a) DNA
  strand breaks, (b) chromosome aberrations, (c)
  sister chromatid exchanges (SCEs), (d) DNA repair
  synthesis, (e) phenotypic mutation, or (f)
  transformation (cancer?like changes). The author
  further conclude While there is limited
  experimental evidence that RF exposure induces
  micronuclei formation, there is abundant evidence
  that it does not. There is some evidence that RF
  exposure does not induce DNA excision repair,
  suggesting the absence of base damage.

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Cell Proliferation

• The Independent Expert Group on Mobile Phones
  comments "Changes in the kinetics of cell
  division and in the proliferation of cells play a
  crucial role in the generation of cancer".
  Several studies have examined the relationship
  between RF radiation, in the mobile phone
  frequencies, and cell proliferation.
• Cleary et al. (1990a, 1990b, 1995) have reported
  increased cell proliferation in experiments using
  brain glioma cells, human lymphocytes, and
  hamster ovary cells. The SARs were high in these
  studies, but temperature levels were well
  controlled.
• Donnellan (1997) also found changes in cell
  proliferation when mast cells were exposed to 835
  MHz under athermal conditions.

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• Kwee and Raskmark (1998), found a decrease in
  cell growth of human epithelial amnion cells
  exposed to 960 MHz microwave fields.
• Capri (2004) also found a slight decrease in cell
  proliferation after exposure to 900 MHz RF
  radiation.
• On the other hand Stagg (1997) and Vijayalaxmi
  (1997) found no increase in cell proliferation in
  their studies using 836.55 MHz and 2450 MHz
  respectively.
• Zeni (2003) found no change in cell cycle
  kinetics when lymphocytes were exposed to various
  signals at 900 MHz frequency.
• Scarfi (2006), in a two-laboratory study, found
  no changes in cell proliferation in lymphocytes
  exposed to RF radiation at 900 MHz.
• Byus (1984) and Paulraj (2002) have reported
  decreased protein kinase activity in rats
  following exposure to RF radiation. Byus used
  modulated fields, while Paulraj used continuous
  wave radiation.
• Pacini (2002) reported that exposure of skin
  fibroblasts to 900 MHz RF radiation for 1 hour
  altered gene expression, proliferation, and
  morphology.

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Ornithine Decarboxylase (ODC)

• ODC is the initial enzyme involved in the
  production of polyamines, which in turn are
  involved in the growth of normal and cancer
  cells.
• The report by the Expert Panel of the Royal
  Society of Canada (1999) extensively reviewed the
  relationship between relationship between ODC
  activity and cancer. It pointed out that ODC
  activity may be increased in pre-malignant
  conditions, or following exposure to chemical
  carcinogens, and that ODC may function as an
  oncogenic protein at high levels of activity.
• Several studies have shown increased ODC levels
  after RF exposure (Byus, 1997, Paulraj, 2002).
  Desta (2003), however, showed a decrease in ODC
  levels with exposure to RF radiation at 835 MHz,
  but only at SAR levels above 5 W/kg. These levels
  were associated with temperature increase in the
  medium used. Höytö (2006) also showed decreased
  ODC levels after RF radiation, but only in
  primary astrocytes and not in secondary neural
  cell lines. The same group (Höytö, 2007) found no
  increase in ODC activity on murine fibroblasts
  exposed at 835 or 872 MHz at SARs of 2.5 and 6.0
  W/kg.

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Hormonal Secretion

• An area attracting attention, as a likely
  potential mechanism for RF radiation intervention
  in living organisms is consideration of a cancer
  promoting effect of RF radiation by altered
  circadian rhythms of pineal activity and
  melatonin release. Several investigations
  examined to what extent hormonal secretion is
  influenced by RF radiation.
• Exposure at up to 0.3 W/kg did not disturb the
  normal circadian profile of melatonin of the
  hypothalamo-pituitary-adrenal axis de Seze et
  al. 1998, 1999.
• However, Stark et al. 1997 conducted a pilot
  study to investigate the influence of RF
  radiation at 3-30 MHz on salivary melatonin
  concentration in dairy cattle.

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In-Vitro Studies of Non-genotoxic Effects?

• Several studies investigated the effect of RF
  radiation on cell cycle kinetics, however, the
  majority of these studies found no effect
  (Vijayalaxmi et al., 2001, Zeni et al., 2003,
  Lantow et al., 2006).
• Several studies investigated whether RF radiation
  can induce apoptosis in human peripheral blood
  mononuclear cells, lymphoblastoid cells,
  epidermis cancer cells. No difference in
  apoptosis induction was detected. Apoptosis is a
  physiological mode of cell death occurring in
  development and cell differentiation. It is an
  important protection mechanism against cancer.
• Some investigators have described increased heat
  shock protein level after RF radiation, however,
  there are other negative findings (for review see
  Cotgreave, 2005). This research area would
  benefit from independent replication.
• Influence of RF radiation on immune system cells
  were investigated in a few studies. No
  significant effects were observed.

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Nervous System What is Already Known about
Nervous System Effects?

• Due to the proximity of mobile phones to the
  head, public concerns are raised regarding a
  potentially toxic effect of RF radiation on the
  nervous system. The following aspects are usually
  considered in toxicology regarding this effect
• Morphology
• Brain Function
• Electrophysiology
• Behavior
• Development
• Several investigations have been published
  regarding the potential neurotoxic effects of RF
  from mobile phones. Minor effects were observed
  on the electroencephalogram (EEG), sleep
  structure, and cognitive processes in human
  objects.

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In Animals

• In animals, few previous studies did show
  disturbance of work memory in rats exposed to RF
  (Lai et al., 1994, Wang and Lai, 2000).
• Surprisingly, low SAR values caused increased
  permeability of the blood-brain barrier (BBB) in
  rats (Salford et al., 1994, 2003, Fritz, 1997
  Persson et al., 1997). Recent animal studies
  failed to detect any changes in the BBB (Tsurita,
  2000 Finnie, 2002 Nylund, 2004 Kuribayashi,
  2005 Cosquer, 2005 Finnie, 2006 Kumlin, 2007).
• The BBB isolates the CNS from the rest of the
  organism, controls molecules fluxes, and protects
  the brain. Increased permeability of BBB can
  allow unwanted substances to reach the CNS, with
  possible pathological consequences (inflammation,
  neurone death)

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Review

• For more details, see the review on this subject
  by DAndrea et al. 2003. The authors concluded
  
• Effects of RF exposure on the BBB have been
  generally accepted for exposures that are
  thermalizing.
• Low level exposures that report alterations of
  the BBB remain controversial.
• Exposure to high levels of RF energy can damage
  the structure and function of the nervous system.
  
• Much research has focused on the neurochemistry
  of the brain and the reported effects of RF
  exposure. Research with isolated brain tissue has
  provided new results that do not seem to rely on
  thermal mechanisms.

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Developmental Effects

• Various studies have evaluated developmental
  effects of RF radiation on mamals, birds, and
  other non-mamalian species. These studies
  reviewed by Heynick and Merritt (2003) and
  Juutilainen (2005), have shown that
• RF radiation are tertogenic at exposure levels
  that are sufficiently high to cause significant
  increase of temperature and exceed reference
  levels from exposure guidelines.
• There is no consistent effects at non-thermal
  exposure levels.
• Only few studies have evaluated possible effects
  on postnatal development using sensitive
  endpoints, such as behavioral effects.

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Conclusion

• There is no reliable indication from the in vitro
  research that RF fields affects cells at
  non-thermal effects. However, results of few
  results suggest genotoxic effects need to be
  better understood.
• Animal cancer studies have not provided evidence
  that RF radiation could induce cancer, enhance
  the effects of known carcinogens, or accelerate
  the development of transplanted tumors.
• Technology is advancing very fast and sources of
  RF exposure become increasingly common. Yet,
  there is a lack of understanding for interaction
  mechanisms below the guidelines and the
  information on individual RF exposure and
  contribution of various sources to the overall
  exposure.
• An important area of research could be the effect
  of modulated or pulsed RF radiation especially on
  brain function, when compared with CW RF
  radiation of the same characteristics.
• Another important area of research that might
  need further investigation is health risk
  associated with childrens use of mobile phones.

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Strength of Evidence for Biological Effects from
Exposure to RF fields
Carcinogenicity RF exposure alone Lack of effect RF fields with a known genotoxic agents Inadequate evidence Genetically especially tumor-prone animals to RF fields Inadequate evidence Development of transplanted tumors Lack of effect
Genotoxicity Gene mutations Lack of effect DNA damage Limited evidence Structural changes Limited evidence
Cancer Related Ornithine Decarboxylase (ODC) Inadequate evidence Gene expression Limited evidence