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| ORIGINAL
COMMUNICATION |
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| Year :
2005 | Volume : 11 |
Issue : 2 | Page : 99-104 |
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Genetic damage in mobile phone users: some
preliminary findings
Gandhi
Gursatej, Anita
Department of Human
Genetics, Guru Nanak Dev University, Amritsar 143 005,
India
Correspondence Address:
Gandhi
Gursatej
Dept. of Human Genetics, Guru Nanak Dev University,
Amritsar 143 005
India
jrgandhi@sancharnet.in
BACKGROUND: The impact of microwave (MW)/radio frequency
radiation (RFR) on important biological parameters is probably more
than a simply thermal one. Exposure to radio frequency (RF) signals
generated by the use of cellular telephones have increased
dramatically and reported to affect physiological, neurological,
cognitive and behavioural changes and to induce, initiate and
promote carcinogenesis. Genotoxicity of RFR has also been reported
in various test systems after in vitro and/or in vivo
exposure but none in mobile phone users. AIMS: In the present
study, DNA and chromosomal damage investigations were carried out on
the peripheral blood lymphocytes of individuals using mobile phones,
being exposed to MW frequency ranging from 800 to 2000 MHz.
METHODS: DNA damage was assessed using the single cell gel
electrophoresis assay and aneugenic and clastogenic damage by the
in vivo capillary blood micronucleus test (MNT) in a total of
24 mobile phone users. RESULTS: Mean comet tail length (26.76
± 0.054 mm; 39.75% of cells damaged) in mobile phone users was
highly significant from that in the control group. The in
vivo capillary blood MNT also revealed highly significant (0.25)
frequency of micronucleated (MNd) cells. CONCLUSIONS: These
results highlight a correlation between mobile phone use (exposure
to RFR) and genetic damage and require interim public health actions
in the wake of widespread use of mobile telephony.
Keywords: DNA damage; micronuclei; microwaves;
peripheral blood lymphocytes
How to cite this article:
Gandhi G,
A. Genetic damage in mobile phone users: some preliminary
findings. Indian J Hum Genet
2005;11:99-104 |
The
continued spread of mobile telephony is of serious concerns since a
relationship between electromagnetic fields radio frequency (RF) and
microwave (MW) radiation and adverse health effects at low intensity
exposures exists. The cell (mobile) phone is an appliance that
requires that it be held close to or touching the head, which is the
most sensitive organ of the body. This has initiated a spate of
studies to enquire for effects on user health and explore mechanisms
of interaction responsible for reported biological sequel on humans,
animals and organic cells from acute and chronic exposures from
mobile phone frequencies. Generally, the higher the frequency the
less able electromagnetic radiation is to penetrate materials.
However, even millimetre waves penetrate irradiated skin to a depth
of 1 mm, while the microcirculatory system of the skin functions at
150 mm and so is fully accessible to EHF exposure. Lower frequencies
can however penetrate further. The mode of interaction between
nonionising electromagnetic radiation and tissue is also highly
dependent on the dielectric behaviour of water and dissolved ions at
RF and MW frequencies.
Wireless communication systems operate
in the 400-2000 MHz range, differing in respect to frequency usage
in different countries and on different continents. In fact, the use
of the digital communication system that transmits radio frequency
radiations (RFR) at higher frequencies in this range has increased
dramatically. The Indian mobile phone market has also shown dramatic
ascent and has 40.6 million users with the global system of mobile
communication (GSM) service having 32.02 million registered users
and the code division multiple access (CDMA) subscribers with 8.6
million (www.Indianews.com, October 2004). The potential for health
effects from low intensity RF/MW radiation from the 'weight of the
scientific evidence' points to a relationship between RF/MW and
illness.
Some of the biological effects associated with RF
radiation include RF sickness, electroencephalographic changes, cell
proliferation[1] and blood pressure changes, blood-brain barrier
leakage,[2] altered EEG patterns[3] and decreased fertility in mice.[4] Cancer risks and genotoxicity from exposure to RF
fields in vivo and in vitro have rather been points of
cynosure since equivocal evidences exist.[5],[6],[7],[8] Apparently no studies have documented genotoxicity
in mobile phone users. The present investigation reports DNA and
chromosomal damage in peripheral blood lymphocytes of mobile phone
users by the single cell gel electrophoresis (SCGE/Comet) assay and
the capillary blood in vivo micronucleus test (MNT). The
study was cleared by the institutional ethical
committee.
| » Methods |
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The subjects were
selected on the basis of period of mobile phone use. Voluntary
written informed consent was obtained and details on their diet,
life style and health status were recorded. Age- and sex-matched
healthy individuals who had never used the mobile phone formed the
control group. Finger-prick blood samples were collected in
heparinised eppendorf tubes, transported in an ice-box to the
laboratory and processed for the comet assay[9],[10] and the MNT[11] within 3-4 h of collection. Peripheral blood
cells were embedded in agarose on agar-coated slides, lysed under
alkaline conditions to partially unwind DNA, electrophorosed
followed by silver staining. Both the normal cells and comets
(100/sample) were scored and DNA migration lengths were measured
less than under 40x using an ocular micrometer calibrated with the
help of a stage micrometer.
The MNT is based on the
observation that when cells with chromatid breaks or exchanges
undergo mitosis, a sizeable portion of chromatin that is not
included in the daughter nuclei, forms a single micronucleus or
multiple micronuclei. The in vivo MNT in lymphocytes of human
capillary blood is a simpler, convenient, informative in vivo
cytogenetic technique and its precision makes it more suitable to
large-scale investigations and human biomonitoring studies. To 0.06
- 1.00 ml blood obtained through finger puncture, 0.3% methyl
cellulose was added to blood in a v/v ratio of 1: 3 and kept in a
water bath (37°C for 40-60 min).The lymphocyte suspension was then
centrifuged at 1000 rpm for 6 min and the pellet, suspended in 43 ml
of remaining supernatant, was used to make smears on glass slides.
Air-dried smears were fixed in 100% methanol for 1 min and stained
in buffered Giemsa (pH 6.4, 1:10, 20 min). Coded pre-parations were
scored (2000 cells/sample at 40x) for MN [small, spherical and
separated chromatin masses in small (T) lymphocytes]. The presence
of micronuclei (as per the given criteria)[12] in the cells was confirmed at 100 x under oil
immersion and randomly by another observer. The main nucleus and MN
show dark blue against the light blue cytoplasm.
| » Results |
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Peripheral blood
lymphocytes of individuals ( n = 24) using mobile phones were
processed in order to assess whether mobile phone usage induces
chromosomal and DNA damage. All those evaluated for the MN test (
n = 20) were also investigated for DNA damage and so are
included among those ( n = 24) for which the SCGE assay was
performed [Table - 1]. Samples from age-, sex- and
socioeconomic status-matched controls ( n = 11) were also
processed for DNA damage ( n = 10) and the MN test ( n
= 8). There were only three females among mobile phone users; very
few smokers ( n = 2) and those taking alcohol ( n =
2). None of the subjects had any family history of any genetic
anomaly or major illness nor had they undergone irradiation
examination or been exposed to organic solvents and for the last 6
months none have been on medication or on drugs and no one did any
regular exercise. The reproductive performance of married
individuals ( n = 7) was known to be normal. However, some of
the selected individuals ( n = 4) complained about
sleeplessness, memory loss, less attentivity and heart pain, which
they felt was associated with mobile phone vibrations. The usage of
phone varied from one to 5 years with most persons ( n = 20)
using it from 2 to 3 years. The specific absorption rate (SAR) gives
estimates of the radiated energy given out by the cell phone and
being absorbed into the body tissues in terms of Watts per kilogram
(W/kg) or milliWatts per gram (mW/g) of body weight. The popular
phone brands were Nokia (SAR = 0.87-1.47 W/kg) with 15 users,
Samsung (SAR = 0.59 and 1.56 W/kg) with four, and Panasonic (SAR =
0.99 W/kg) with three users. The daily use of phone ranged from 1 to
15 h, which actually contributes to the daily direct exposure in the
real sense though the mobile was kept on 'On' mode for 24 h by 22
subjects. There were 17 individuals attending phones from the right
ears whereas nine attended from left ears. None subjects used any
protective cases for mobile phones and no one among them availed of
any special offer (s).
The SCGE assay results demonstrated
DNA migration in ~40% (39.75) of mobile phone users with a mean tail
length of 26.76 ± 0.054 mm (range 16.91 ± 0.192 to 31.86 ± 0.252 mm)
which was significantly increased from the control value (8.11 ±
0.028 mm with 10.40% of cell damage). The maximum tail length was
observed in the blood sample (with 43% cell damage) of a 28-year-old
male who was dealing in automobile spare parts and was using Nokia
3310 (SAR = 1.27 W/kg) for the past 4 years. At the time of sample
collection his daily communication on mobile phone was from 1.5 to
2.0 h. The higher value of comet tail length may be due to longer
duration of mobile phone use as he is a nonsmoker, nonalcoholic, and
nonvegetarian. Similarly in peripheral blood lymphocytes of another
male aged 21 years (a two-wheeler mechanic), a long-tail length
(31.12 mm, with 32% damaged cells) was observed. He had been using
Nokia C131 (SAR = 0.87 W/kg) for 2.5 years with daily use of 1.5-2 h
and probably with some exposure at his work place also contributing
towards the genetic damage observed in his PBLs. The maximum number
of damaged cells (63%) was observed in a male (24 years) using
Samsung 220 (SAR = 0.59 W/kg) for 2 years with 1-1.5 h daily mobile
phone usage. Among the control individuals, comet tail lengths
ranged from 6.03 ± 0.130 to 10.3 ± 0.090 mm.
Chromosomal
damage (aneugenic/clastogenic) was also scored for in 20 individuals
and in eight controls. There was a marked difference in the
frequencies of micronucleated (MNd) cells among subjects (av. 0.25
MNd cells) and the control group (av. 0.05 MNd cells; only 3.8% had
MN). The maximum MNd cell frequency of 0.50 was observed in a male
(24 years) who had been using Nokia 3310 (SAR = 1.24 W/kg) for 2
years with a daily use of 8-9 h and working in the customer-care
department of a mobile phone company. The minimum frequency of MNd
cells (0.10 each) was observed in two males aged 24 and 28 years, a
businessman and software analyst, respectively. Both were using
mobile phones for 2 years with SAR of 0.59 and 1.47 W/kg and with a
daily use of 1-1.5 and 3-4 h, respectively.
| » Discussion |
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Both the MNT and SCGE
assay were employed for assessing any genetic damage in mobile phone
users being exposed to mobile phone MW frequency ranging from 800 to
2000 MHz. Significant increases in DNA tail lengths, of cells with
DNA damage and in MNd cells of mobile phone users were observed.
Data for DNA and chromosomal damage of female subjects were clubbed
with that of male subjects, as there were no differences in the
values. No significant influence of sex on MN frequency has been
also reported in the in vivo capillary blood MN test.[11] More DNA damage than micronuclei induction in the
same PBL samples was noted. This is because the MN test detects
injuries that survive at least one mitotic cycle, while the comet
assay identifies repairable injuries or alkali-labile sites, which
cause an increased intensity of comet tail length but do not cause
MN induction. It has been reported that when the exposure to
genotoxic agents is small, even though there may be positive results
in the comet assay, correspondingly positive results in the MN test
may not occur.[13]
The presence of MNd cells was observed in
only ~4% of control individuals. This low frequency may be due to
good dietary patterns in the absence of smoking and drinking habits.
Punjabi people have a fairly good intake of fruits and vegetables,
which are associated with reduced risks for cancers. The carotenoids
and carotenoid-rich foods can influence DNA damage and repair by
modulating discrete stages in the DNA repair mechanisms.[14] The effects of mobile use can be curbed depending
upon the availability of dietary antioxidants,[15] consumption of ethanol,[16] conditions like psychological stress[17] and strenuous physical exercise.[18] This emphasizes the speculation that some
individuals may be more susceptible to the effects of RFR
exposure.[19]
The results of the present study are in
tune with some reports in the literature. Chromosome aberrations and
micronuclei were significantly higher than the controls, in a group
of workers exposed to 10 to 50 mW/cm2 of radar producing MWs and/or
also exposed to about 5 ppm of vinyl chloride monomer, a known
carcinogen.[20] Human lymphocytes exposed to MW radiation
produced a dose response increase in chromosome aberrations.[21]
Occupational exposure to MWs in 12 workers
had significantly increased chromosome damage as well as
disturbances in the distribution of cells over the first-, second-
and third-mitotic divisions.[22] In rat brain cells exposure of both continuous
wave (CW) and pulsed microwaves (PW) caused significant increase in
single- and double-strand DNA breakage with PW causing more damage
than CW.[6] Neither direct chromosomal damage (chromosome
aberrations and SCEs) nor tail moment and tail lengths increased in
comet assay when human whole blood cells were exposed to continuous
935.2 MHz (SAR 0.3-0.4 W/kg) but a synergistic effect after RFR
exposure followed by mitomycin-C was reported in the form of an
increase in SCEs.[23] In vitro exposure of human peripheral
blood lymphocytes to continuous 830 MHz EMF (SAR 1.65-8.8 W/kg) for
72 h caused losses and gains of chromosomes. A linear increase in
Chr # 17 aneuploidy was observed as a function of SAR value at
34.5-37.5°C indicating that the genotoxic effect of the EMF is
elicited via a nonthermal pathway.[24]
Some contrary reports include: absence of
primary DNA damage in human glioblastoma and mouse fibroblast cells
exposed to 835.62 MHz (FDMA) and 847.74 MHz (CDMA) RFR,
respectively, at SAR 0.6 W/kg.[8] Equal number of DNA breaks in rat lymphocytes were
reported in both controls and animals exposed to 945 MHz RFR for 1-5
weeks.[25]Human blood lymphocytes exposed to 837 MHz (TDMA),
837 MHz (CDMA) and 1900 MHz (PCS) showed no increase in primary DNA
damage or of MNd binucleated human blood lymphocytes.[26] PBL cultures of 20 healthy donors exposed to CW
intermittent exposure and GSM signals did not increase MN frequency
in the cytokinesis - block MN assay.[27] PBL cultures exposed to both CW and PW 1.9 GHz
RFR at SAR 0-10 W/kg for 24 h revealed no significant increase in
DNA damage or MN frequency.[28] No statistically significant differences in the
level of DNA damage or apoptosis by SCGE assay and annexin V
affinity assay, respectively were observed between sham-treated and
RF- exposed Molt-4T lymphoblastoid cells.[29]
In the light of this literature it can be
observed that the studies documenting positive genotoxicity are
those where there is mostly in vivo occupational exposure to
RFR of mobile phone range. The present study clearly demonstrates
the same, albeit the exposure is directly through mobile phone use.
There is a potential for a very large worldwide public health impact
in the wake of the results of this study and calls for interim
public health protective measures.
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Tables [Table - 1]
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