Protons for Breakfast

Are Mobile Phones Safe?

Week 5

November 2011

In the event of an alarm sounding…

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’ meansAnything which ‘radiates’ on ray-like paths

• Could be SoundRadioLightInfra-red lightParticles 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

• 50,000 base stations in UK

Roughly hexagonal cells

Mast

• Each colour represents a base station operating at a slightly different frequency

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

Its complicated!

Network Control

Knows in which cell every telephone is

Originating Telephone

Receiving Telephone

2G or GSM phone

Hello! How are you?Sound

217 pulses of encoded sound every second No sound: No signal

Encoding to Radio Signal Hello! How are you?

Peak Power 2 W Maximum

Average power is 0.25 W Maximum

Global System for Mobile Communications

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 2O2 (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

217 Pulses per second

Each frequency channel can carry 7 calls

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

1 101 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022

Radio & TVInfra Red

Microwaves

Gamma-Rays

X-Rays

Ultra Violet

Microwaves0.8 GHz

to 1000 GHz

Non-ionising Radiation

(generally not so bad)

Ionising Radiation

(generally bad)

Frequency (Hertz)

Waves & Matter

• When an electromagnetic wave interacts with matter…Some absorption Some reflectionSome transmission

Summary

• Electromagnetic waves interacting with matter can beReflected, absorbed or transmitted

• What happens depends onthe frequency of the electric fieldthe natural frequencies of the atoms and molecules

• Microwaves emitted by mobile phone systemsAre absorbed by human tissue

1 101 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022

Radio & TV

Frequency (Hertz)

Microwaves

Infra Red Ultra Violet

X-rays

Gamma Rays

Electrons in Atoms

Protons in nucleus

Atoms in solids or

molecules

Entire molecules or parts of molecules

Lighter particles

Stronger forces

Waves

What vibrates?

Absorption demo

Frequency

•Well below the natural frequency•Not much absorption

•Well above the natural frequency•Not much absorption

•Near the natural frequency•Absorption

Waves & Matter

• When electromagnetic waves are ‘absorbed’ …• Atoms jiggle faster:

i.e. increase their temperature.

Heat

Electricity

Electromagnetic waves

Atoms

3. How much energy gets absorbed?

S.A.R.Specific Energy Absorption Rate

Terminology

• Powerwatts

• Intensitywatts per square metre

• Specific energy Absorption Rate (SAR)watts per kilogram

• 1 cm from 20 W source 20 W absorbed in hand Intensity 8000 watts per square metreSAR 200 watts per kilogram

• 10 cm from 20 W source 2 W absorbed in hand Intensity 200 watts per square metreSAR 20 watts per kilogram

• 1 metre from 20 W source 0.02 W absorbed in hand Intensity 5 watts per square metreSAR 0.2 watts per kilogram

SAR: Example using lightrather than microwaves

Microwave Hazard

The potential hazard from mobile phones and other wireless devices arises from

the absorption of microwave radiationMobile 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

1 101 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022

Radio & TVInfra Red

Microwaves

Gamma-Rays

X-Rays

Ultra Violet

Microwaves

Conventional Oven200 °C

Microwave Oven 2.45 GHz

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.01 0.1 1 10 100

Abs

orbt

ion

Frequency

Absorption of microwaves by liquid water

• Well below the natural frequency

• Not much absorption

• Well above the natural frequency

• Not much absorption

• Near the natural frequency

• Absorption

2.45 GHz

Absorption (1)Too strong

• If power were absorbed too strongly,Microwaves would only penetrate a short distanceSurface would be heatedInside would remain uncooked

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.01 0.1 1 10 100

Loss

of e

nerg

y in

wat

er a

t 0

C

Frequency (GHz)

Microwave ovens operate at 2.45 GHz

Absorption (2) Too weak

• If power were absorbed too weakly,Microwaves would go right through No cooking

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.01 0.1 1 10 100

Loss

of e

nerg

y in

wat

er a

t 0

C

Frequency (GHz)

Microwave ovens operate at 2.45 GHz

Absorption (3)

• If power is absorbed just right,Microwaves penetrate about 5 cm (2 inches) Cooks the outer 5 cm of the foodGood enough for most cases

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.01 0.1 1 10 100

Loss

of e

nerg

y in

wat

er a

t 0

C

Frequency (GHz)

Microwave ovens operate at 2.45 GHz

Microwave OvensSummary

• 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 OvenSAR 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 OvensComparison with handsets

SAR Wattsper kilogram

Temperature Rise in 1 kg of ‘Brain Fluid’

Microwave 700 8 ºC (ish)

Mobile Phone 1 Can’t be measured directly

Expect 1/700 of microwave temperature riseThe effects of blood flow reduce this further

0.01 °C (ish)

Back to Mobile Phones 3b. Mobile Phone SAR

New StyleOld StyleMobile Phones (14) SAR and Safety

Mobile Phones (8) Your telephone

• Look in the small print!

Typical SAR with phone near the head

• SAR Averaged over 10 grams• By law must be less than 2 watts per kilogram

Power Intensity MaximumSAR

Watts Watts per square metre

Wattsper kilogram

1 200 1

• Typical figures

Base Station SAR

Base Stations

• Power

6 degrees

50 m to 200 m

Base Station Informationhttp://www.sitefinder.ofcom.org.uk/

EIRO

Equivalent isotropic RadiatedOutput

Actual Pattern of Emitted Radiation

60 W

How this is specified

Mast near my children’s old schoolPower• 30 dBW • 1000 W • Equivalent isotropic

Radiated Output• 60 W to 120 W in

actual power

1000 W EiRO

Actual Pattern of Emitted Radiation

0.3Watts per square metre

0.01Watts per square metre

SAR 0.001Watts per kilogram

Comparison of handsetsand base stations

• Base station SAR is extremely lowbut you can’t choose whether you want it or not!

Power Intensity MaximumSAR

Watts Watts per square metre

Wattsper kilogram

Handset 1 200 About 1

Base Station 60 0.01 About 0.001

Wireless Networking

• WiFi802.11(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

Wattsper kilogram

0.1 Less than 0.01 About 0.0001

Comparison of handsetsand base stations and wi-fi

Power Intensity MaximumSAR

Watts Watts per square metre

Wattsper 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 Protectiondetermines 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 experimentExperiments are very hard

Are mobile phones safe?

Stewart Report • A group of non-industry related experts

Gave rise to MTHRMobile 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’

Precautionary Approach: More research

please

Children 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 ScanThis device can see you think!

Glucose metabolism in this area appears to have been affected

What could we do?What should we do?

In smaller groups

• Please come up with some

questions, and suggestions

• We will gather these together and

then ask the experts

You decide!

On-line Resources

• www.protonsforbreakfast.org This PowerPoint ™ presentation.Handouts as a pdf file

• blog.protonsforbreakfast.org Links to other sites & resourcesMe going on about things

See you next week to discuss Nuclear Power

Goodnight

Mobile Phones

Unused Slides

Perception of risk

Risk is expressed mathematically, but our judgement of risk is not mathematical

More willing to take risk

Less willing to take risk

Example

Benefits Direct Indirect Base Stations/Mobile Phones

Technology Familiar Unfamiliar Cars/Mobile Phones

Exposure Voluntary Involuntary Base Stations/Mobile Phones

Exposure Fair Unfair Poverty/Wealth

Exposure Personal Control No Personal Control

Driver/Pedestrian

Consequence Not Dreaded Dreaded Cancer/ Broken bone

Electromagnetic waves

Electricity

Heat

How it all fits together…

Atoms

A Cautionary Tale

Don’t try this at home!

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 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?

R Luria, I Eliyahu, R Hareuveny, M Margaliot, N, MeiranCognitive Effects of Radiation Emitted by Cellular Phones:

The influence of exposure side and timeBiolectromagnetics 30: 198-204 (2009)

Possibility#1

No MatchClick with Left Hand

MatchClick with Right Hand

Task Completed with PhoneOn LEFTOn RIGHTOFF

RESULTS

700

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1000

1050

1100

1 2 3 4 5 6 7 8 9 10 11 12

SHAMLEFT EXPOSURERIGHT EXPOSURE

Res

pons

e Ti

me:

mill

isec

onds

Block

LEFT HAND RESPONSE

'No Match' RESPONSE

1 hour 1 hour

RESULTSWith Uncertainty

700

750

800

850

900

950

1000

1050

1100

1 2 3 4 5 6 7 8 9 10 11 12

SHAMLEFT EXPOSURERIGHT EXPOSURE

Res

pons

e Ti

me:

mill

isec

onds

Block

LEFT HAND RESPONSE

'No Match' RESPONSE

Only these two points have statistical significance

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 powerIncrease the number of masts

• Ban mobile phone use while driving ?Done: has it been effective?

• Nothing ?