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Genetic damage in mobile phone users: some
preliminary findings
Author: 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
Abstract
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.
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
Full Text
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
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
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
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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© 2006 Indian Journal of Human Genetics
