Protons for Breakfast
Are Mobile Phones Safe?
Week 5
March 2013
In the event of
of…
a new ice age…
This evening…
0. The Media!
1. How do mobile phones work?
What is the hazard?
2. How do electromagnetic waves interact
with matter?
3. SAR
• Microwave Ovens
• Mobile Phone
4. Are mobile phones safe?
The word ‘radiation’
• The word ‘radiation’ means
Anything which ‘radiates’ on ray-like paths
• Could be
Sound
Radio
Light
Infra-red light
Particles or waves emitted from the nuclei of atoms
Nuclear Radiation
Media
Media
Sunday, 20 January 2008
It also complements other recent research.
A massive study, following 1,656 Belgian
teenagers for a year, found most of them
used their phones after going to bed. It
concluded that those who did this once a
week were more than three times – and
those who used them more often more than
five times – as likely to be "very tired".
1. How do mobile phones work?
Magic?
Any sufficiently advanced technology
is indistinguishable from magic
Arthur C. Clarke
Not magic
• Mobile Phones are ‘radio’
phones
• Operating at microwave
frequencies
• Handset power minimised
by having a network of
local transmitters and
receivers
• Each colour represents a
base station operating at a
slightly different frequency
Roughly
hexagonal cells
• 52,500 base stations in UK
Mast
Mobile Phones (3)
Recognise the masts?
• Each cell has a transmitter and receiver mast
• Notice the typical three way structure
3G Masts
Photo Credit Brighton and Hove Green Party
Linking to base stations
• Mast power between
60 watts and 120 watts
• Handset power
less than 1 watt
• Handset sends signals
every few minutes to
establish which is the
nearest mast
• A central computer
• keeps track of all the telephones that are switched on
• remembers which cell they are in
Making a mobile-to-mobile call
Network Control
Its complicated!
Originating
Telephone
Knows in which cell
every telephone is
Receiving
Telephone
2G or GSM phone
Global System for
Mobile Communications
Sound
Hello!
How
are
you?
Encoding to Radio Signal
Hello!
How are you?
Peak Power
2 W Maximum
Average power is
0.25 W Maximum
No sound: No signal
217 pulses of encoded sound every second
2G or GSM phone
Base station
Transmitter
Frequencies
(MHz)
Handset
Transmitter
Frequencies
(MHz)
Peak
Handset
Power
(Watts)
Originally
licensed to
GSM900
935 - 960
890-915
2
O2 (Tesco)
Vodafone (Asda)
GSM1800
1805-1880
1710-1785
1
Orange
T Mobile (Virgin)
Anatomy of a GSM Signal
2G or GSM phone
217 Pulses per second per telephone call
Each frequency channel can carry 7 calls
217 Pulses per second
Safety
• The safety issues surrounding mobile phones
concern…
• the interactions of the microwaves emitted by
mobile phones
base stations
with human tissue
6 degrees
50 m to 200 m
And its not just mobile phones!
•
•
•
•
•
•
‘WiFi’ Wireless Networking
Bluetooth devices
Wireless keyboards and mice
DECT cordless phones
Baby Monitors
‘Walkie Talkie’
• All involve electromagnetic
waves in the radio and
microwave part of the
spectrum
2. How do electromagnetic waves
interact with matter?
?
Electromagnetic spectrum
Infra Red
Radio & TV
Microwaves
Microwaves
0.8 GHz
to
1000 GHz
Non-ionising
Radiation
(generally not so bad)
Ultra
Violet
GammaRays
X-Rays
Ionising
Radiation
(generally bad)
1 101 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022
Frequency (Hertz)
Waves & Matter
• When an electromagnetic wave interacts with matter…
Some absorption
Some reflection
Some transmission
Summary
• Electromagnetic waves interacting with matter can be
Reflected, absorbed or transmitted
• What happens depends on
the frequency of the electric field
the natural frequencies of the atoms and molecules
• Microwaves emitted by mobile phone systems
Are absorbed by human tissue
Waves
Radio & TV
Infra Red
Ultra
Violet
Microwaves
Gamma
Rays
X-rays
What vibrates?
Atoms in
solids or
molecules
Electrons in Atoms
Entire molecules or
parts of molecules
Protons in
nucleus
Lighter particles
Stronger forces
1 101 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022
Frequency (Hertz)
Absorption demo
•Well below the natural frequency
•Not much absorption
•Near the natural frequency
•Absorption
•Well above the natural frequency
•Not much absorption
Frequency
Waves & Matter
• When electromagnetic waves are ‘absorbed’ …
• Atoms jiggle faster:
i.e. increase their temperature.
Electricity
Atoms
Heat
Electromagnetic waves
3. How much energy gets absorbed?
S.A.R.
Specific Energy Absorption Rate
Terminology
• Power
watts
• Intensity
watts per square metre
• Specific energy Absorption Rate (SAR)
watts per kilogram
Example
using light
• 1 cm SAR:
from 20
W source
20 W absorbed
in hand
rather than
microwaves
Intensity 8000 watts per square metre
SAR 200 watts per kilogram
• 10 cm from 20 W source
2 W absorbed in hand
Intensity 200 watts per square metre
SAR 20 watts per kilogram
• 1 metre from 20 W source
0.02 W absorbed in hand
Intensity 5 watts per square metre
SAR 0.2 watts per kilogram
Microwave Hazard
The potential hazard from mobile phones and other
wireless devices arises from
the absorption of microwave radiation
Mobile phones
• only emit a watt or two
• so little power it makes
experiments difficult
Microwave ovens
• emit a few hundred watts
• makes experiments easy
Microwave Ovens
3a. Microwave ovens
Electromagnetic spectrum
Infra Red
Radio & TV
Ultra
Violet
GammaRays
Microwaves
X-Rays
Microwave Oven
2.45 GHz
Conventional Oven
200 °C
1 101 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022
Absorption of microwaves by liquid water
0.4
•
0.35
•
•
Near the natural
frequency
Absorption
•
Absorbtion
0.3
Well above the
natural frequency
Not much
absorption
0.25
0.2
0.15
•
•
Well below the natural
frequency
Not much absorption
0.1
2.45 GHz
0.05
0
0.01
0.1
1
Frequency
10
100
Absorption (1)
Too strong
• If power were absorbed too strongly,
Microwaves would only penetrate a short distance
Surface would be heated
Inside would remain uncooked
0.4
0.35
0.3
0.25
Microwave ovens
operate at
2.45 GHz
0.2
0.15
0.1
0.05
0
0.01
0.1
1
Frequency (GHz)
10
100
Absorption (2)
Too weak
• If power were absorbed too weakly,
Microwaves would go right through
No cooking
0.4
0.35
0.3
0.25
Microwave ovens
operate at
2.45 GHz
0.2
0.15
0.1
0.05
0
0.01
0.1
1
Frequency (GHz)
10
100
Absorption (3)
• If power is absorbed just right,
Microwaves penetrate about 5 cm (2 inches)
Cooks the outer 5 cm of the food
Good enough for most cases
0.4
0.35
0.3
0.25
Microwave ovens
operate at
2.45 GHz
0.2
0.15
0.1
0.05
0
0.01
0.1
1
Frequency (GHz)
10
100
Microwave Ovens
Summary
• A microwave oven cooks food by heating it
• The heating comes from
• intense waves at 2.45 GHz
• (Instead of a wide spectrum of waves at infra red frequencies)
Frequency chosen because of absorption properties of water
molecules at that frequency.
Microwave Ovens
Inside a microwave oven
Microwave Power
• Power
– This is a 700 watt oven
– Think of 7 x 100 watt light bulbs
Microwave Electric field
• 700 watts
– Around 140 000 volts per metre
– Look what happens to a CD
Microwave Intensity
– Between 104 to 105 watts per square metre
– (Most intense sunlight around 103 watts per square metre)
– Very Dangerous
Could I have a
stupid volunteer
please?
Microwave Oven
SAR inside oven
• 700 watts absorbed in 1 kg of water:
– SAR = 700 watts per kg
• Question: After 1 minute, how hot would your
brain become if subject to an SAR of 700 watts
per kg?
Experiment
Microwave Ovens
Comparison with handsets
SAR Watts
per kilogram
Temperature
Rise in 1 kg of
‘Brain Fluid’
Microwave
700
8 ºC (ish)
Mobile Phone
1
Can’t be measured directly
0.01 °C (ish)
Expect 1/700 of microwave temperature rise
The effects of blood flow reduce this further
Back to Mobile Phones
3b. Mobile Phone SAR
Mobile Phones (14)
SAR and Safety
Old Style
New
Style
Mobile Phones (8)
Your telephone
• Look in the small print!
Typical SAR with phone near the head
• Typical figures
Power
Intensity
Maximum
SAR
Watts
Watts per
square metre
Watts
per kilogram
1
200
1
• SAR Averaged over 10 grams
• By law must be less than 2 watts per kilogram
Base Station SAR
Base Stations
• Power
6 degrees
50 m to 200 m
Base Station Information
http://www.sitefinder.ofcom.org.uk/
EIRO
How this is specified
Equivalent
isotropic
Radiated
Output
60 W
Actual Pattern of
Emitted Radiation
Mast near my children’s old school
1000 W
EiRO
Power
• 30 dBW
• 1000 W
• Equivalent isotropic
Radiated Output
• 60 W to 120 W in
actual power
Actual Pattern of
Emitted Radiation
SAR 0.001
Watts per kilogram
0.3
0.01
Watts per square metre
Watts per square metre
Comparison of handsets
and base stations
Power
Intensity
Maximum
SAR
Watts
Watts per
square metre
Watts
per kilogram
Handset
1
200
About 1
Base Station
60
0.01
About 0.001
• Base station SAR is extremely low
but you can’t choose whether you want it or not!
Wireless Networking
• WiFi
802.11(b), 802.11(g), 802.11(n)
• Operates at 2.4 GHz
Power
Intensity
(at 1 metre)
SAR
(at 1 metre)
Watts
Watts per square
metre
Watts
per kilogram
0.1
Less than 0.01
About 0.0001
Comparison of handsets
and base stations and wi-fi
Power
Intensity
Maximum
SAR
Watts
Watts per
square metre
Watts
per kilogram
Handset
1
200
About 1
Base Station
60
0.01
About 0.001
Wi Fi
0.1
< 0.01
About 0.0001
4. Are Mobile Phones Safe?
SAR and Safety
Health Protection Agency
• Based on ICNIRP guidelines
http://www.icnirp.de/documents/emfgdl.pdf
International Commission on Non-Ionising Radiation Protection
determines what we believe is safe
• How do they do that?
• They determine a borderline safe level
• Divide by 10 for occupational exposure
• Divide by another factor 5 for general public exposure
What are the risks?
• Basic safety assumption is that the main effect of
exposure to microwaves is thermal
• Are there ‘non-thermal’ effects?
If so are they harmful?
Normal thermal vibrations are much larger than
vibrations induced by microwaves emitted by
mobile phones.
• Question of safety must be resolved by experiment
Experiments are very hard
Are mobile phones safe?
Stewart Report
• A group of non-industry related experts
Gave rise to MTHR
Mobile Telecommunications and Health Research
• ONGOING Research Program
• Funded 50:50 government & industry
Stewart Report
Mobile Phones and their
networks are ‘pretty’ safe
There may
be ‘effects’
Children
Precautionary
Approach:
More research
please
Driving
Mobile Phones
Suppose we discovered ‘an effect’:
What might it look like?
Nora D. Volkow, Dardo Tomasi, Gene-Jack Wang, Paul Vaska, Joanna S.
Fowler, Frank Telang, Dave Alexoff, Jean Logan, Christopher Wong,
Effects of Cell Phone Radiofrequency Signal Exposure
on Brain Glucose Metabolism
Journal of the American Medical Association, February 23, 2011—Vol 305, No. 8
PET Scan
This device can see you think!
Glucose metabolism in this area appears
to have been affected
What could we do?
What should we do?
You decide!
In smaller groups
• Please come up with some
questions, and suggestions
• We will gather these together and
then ask the experts
On-line
Resources
• www.protonsforbreakfast.org
This PowerPoint ™ presentation.
Handouts as a pdf file
• blog.protonsforbreakfast.org
Links to other sites & resources
Me going on about things
Goodnight
See you next week to
discuss Nuclear
Power
Mobile Phones
Unused Slides
More willing
Perception of
risk
to take risk
Benefits
Less willing
to take risk
Direct Indirect
Example
Base Stations/
Mobile Phones
Risk is expressed mathematically,
Cars/
but
our
judgement
of
risk
is
not
mathematical
Technology
Familiar Unfamiliar
Mobile Phones
Exposure
Voluntary Involuntary
Exposure
Fair Unfair
Exposure
Consequence
No Personal
Personal Control
Control
Not Dreaded Dreaded
Base Stations/
Mobile Phones
Poverty/
Wealth
Driver/
Pedestrian
Cancer/
Broken bone
How it all fits together…
Electricity
Atoms
Heat
Electromagnetic
waves
A Cautionary Tale
August 14, 2002 I don't want to sound like I know everything in the world or
even like I know quite a lot. But you had a question regarding “If a microwave
oven door were to open while it was still on, what would happen? Could it hurt
you?- JP” Well ..Having the thought process that I have, kinda how should I put
it? ...Stupid? or inventive or even in-between. Well, my microwave door did
happen to come off. Magic Chef 900-watt microwave. Well, I did my best to try to
fix it but the hinge on one side did not attach properly, therefore having a gap
Don’t try this at home!
between the door and the appliance. Being me (stupid) I wondered if it would
burn fast or would it gradually warm up. I slid my finger between...You probably
dying to hear what happened... But it didn't gradually warm up at all. It was
instant heat! It didn't scar me or anything like that, but sure scared the H*** out of
me to find out it got so hot so quick. I didn't get any blisters either. But it just
burned like touching something hot on the tip of my finger being that is the only
thing I put in. Well you know the old adage, "You learn from your mistakes",
stands true. lol -
Mobile Phones
Suppose we discovered ‘an effect’:
What might it look like?
Possibility#1
R Luria, I Eliyahu, R Hareuveny, M Margaliot, N, Meiran
Cognitive Effects of Radiation Emitted by Cellular Phones:
The influence of exposure side and time
Biolectromagnetics 30: 198-204 (2009)
No Match
Click with Left Hand


 
Match
Click with Right Hand



Task Completed with
Phone
On LEFT
On RIGHT
OFF
RESULTS
1 hour
1100
1 hour
1100
950
900
850
800
700
RIGHT HAND RESPONSE
1050
'No Match' RESPONSE
1000
750
Response Time: milliseconds
Response Time: milliseconds
LEFT HAND RESPONSE
1050
SHAM
LEFT EXPOSURE
RIGHT EXPOSURE
Match RESPONSE
1000
950
900
850
800
750
700
1 2 3 4 5 6 7 8 9 10 11 12
Block
SHAM
LEFT EXPOSURE
RIGHT EXPOSURE
1
2
3
4
5
6 7
Block
8
9 10 11 12
RESULTS
With Uncertainty
Only these two points have statistical significance
1100
1100
950
900
850
800
700
RIGHT HAND RESPONSE
1050
'Match' RESPONSE
'No Match' RESPONSE
1000
750
Response Time: milliseconds
Response Time: milliseconds
LEFT HAND RESPONSE
1050
SHAM
LEFT EXPOSURE
RIGHT EXPOSURE
1000
950
900
850
800
750
700
1 2 3 4 5 6 7 8 9 10 11 12
Block
SHAM
LEFT EXPOSURE
RIGHT EXPOSURE
1
2
3
4
5
6 7
Block
8
9 10 11 12
What could we do?
• Ban mobile phones ?
The ‘Precautionary principle’
Could there be some harm caused?
How many lives are saved by mobile phones?
• Reduce mobile phone power ?
Increase the number of mobile phone masts
• Reduce mast power ?
Increase the mobile phone handset power
Increase the number of masts
• Ban mobile phone use while driving ?
Done: has it been effective?
• Nothing ?