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Pfb17 week5-presentation
Mobile phones emit radiofrequency electromagnetic waves that interact with human tissue. The safety of mobile phone use depends on the strength of absorption of these waves, measured by the specific absorption rate (SAR). SAR levels from mobile phones and base stations are well below thresholds considered safe by international health organizations based on extensive research. However, some studies have found biological effects from exposure levels below these thresholds, so further research is ongoing to understand any potential long-term health risks.
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Pfb17 week5-presentation
- 1. Protons for Breakfast AreMobile Phones Safe? Week 5 March 2013
- 2. In the eventof…In the event of a new ice age…
- 3. This evening… 0. TheMedia! 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?
- 4. 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
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- 7. Sunday, 20 January2008 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".
- 8. 1. How domobile phones work?
- 9. Magic? Any sufficiently advancedtechnology is indistinguishable from magic Arthur C. Clarke
- 10. Not magic • MobilePhones are ‗radio‘ phones • Operating at microwave frequencies • Handset power minimised by having a network of local transmitters and receivers • 52,500 base stations in UK Roughly hexagonal cells Mast • Each colour represents a base station operating at a slightly different frequency
- 11. Mobile Phones (3) Recognisethe masts? • Each cell has a transmitter and receiver mast • Notice the typical three way structure
- 12. 3G Masts Photo CreditBrighton and Hove Green Party
- 13. Linking to basestations • 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
- 14. Making a mobile-to-mobilecall Its complicated! Network Control Knows in which cell every telephone is Originating Telephone Receiving Telephone
- 15. 2G or GSMphone 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
- 16. 2G or GSMphone 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)
- 17. Anatomy of aGSM Signal
- 18. 2G or GSMphone 217 Pulses per second per telephone call 217 Pulses per second Each frequency channel can carry 7 calls
- 19. Safety • The safetyissues 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
- 20. And its notjust 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
- 21. 2. How doelectromagnetic waves interact with matter? ?
- 22. Electromagnetic spectrum 1 101102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 Radio & TV Infra Red Microwaves Gamma- Rays X-Rays Ultra Violet Microwaves 0.8 GHz to 1000 GHz Non-ionising Radiation (generally not so bad) Ionising Radiation (generally bad) Frequency (Hertz)
- 23. Waves & Matter •When an electromagnetic wave interacts with matter… Some absorption Some reflection Some transmission
- 24. Summary • Electromagnetic wavesinteracting 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
- 25. 1 101 102103 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?
- 26. Absorption demo Frequency •Well belowthe natural frequency •Not much absorption •Well above the natural frequency •Not much absorption •Near the natural frequency •Absorption
- 27. Waves & Matter •When electromagnetic waves are ‘absorbed’ … • Atoms jiggle faster: i.e. increase their temperature. Heat Electricity Electromagnetic waves Atoms
- 28. 3. How muchenergy gets absorbed? S.A.R. Specific Energy Absorption Rate
- 29. Terminology • Power watts • Intensity wattsper square metre • Specific energy Absorption Rate (SAR) watts per kilogram
- 30. • 1 cmfrom 20 W source 20 W absorbed in hand 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 SAR: Example using light rather than microwaves
- 31. Microwave Hazard The potentialhazard 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
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- 33. Electromagnetic spectrum 1 101102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 Radio & TV Infra Red Microwaves Gamma- Rays X-Rays Ultra Violet Microwaves Conventional Oven 200 °C Microwave Oven 2.45 GHz
- 34. 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.01 0.1 110 100 Absorbtion 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
- 35. 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 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.01 0.1 1 10 100 Lossofenergyinwaterat0C Frequency (GHz) Microwave ovens operate at 2.45 GHz
- 36. 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 Lossofenergyinwaterat0C Frequency (GHz) Microwave ovens operate at 2.45 GHz
- 37. Absorption (3) • Ifpower 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 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.01 0.1 1 10 100 Lossofenergyinwaterat0C Frequency (GHz) Microwave ovens operate at 2.45 GHz
- 38. Microwave Ovens Summary • Amicrowave 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.
- 39. Microwave Ovens Inside amicrowave oven
- 40. Microwave Power • Power –This is a 700 watt oven – Think of 7 x 100 watt light bulbs
- 41. Microwave Electric field •700 watts – Around 140 000 volts per metre – Look what happens to a CD
- 42. Microwave Intensity – Between104 to 105 watts per square metre – (Most intense sunlight around 103 watts per square metre) – Very Dangerous Could I have a stupid volunteer please?
- 43. Microwave Oven SAR insideoven • 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?
- 44.
- 45. Microwave Ovens Comparison withhandsets 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 Expect 1/700 of microwave temperature rise The effects of blood flow reduce this further 0.01 °C (ish)
- 46. Back to MobilePhones 3b. Mobile Phone SAR
- 47. New StyleOld StyleMobilePhones (14) SAR and Safety
- 48. Mobile Phones (8) Yourtelephone • Look in the small print!
- 49. Typical SAR withphone near the head • SAR Averaged over 10 grams • By law must be less than 2 watts per kilogram Power Intensity Maximum SAR Watts Watts per square metre Watts per kilogram 1 200 1 • Typical figures
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- 51. Base Stations • Power 6degrees 50 m to 200 m
- 52.
- 53. EIRO Equivalent isotropic Radiated Output Actual Pattern of EmittedRadiation 60 W How this is specified
- 54. Mast near mychildren’s old school Power • 30 dBW • 1000 W • Equivalent isotropic Radiated Output • 60 W to 120 W in actual power 1000 W EiRO Actual Pattern of Emitted Radiation 0.3 Watts per square metre 0.01 Watts per square metre SAR 0.001 Watts per kilogram
- 55. Comparison of handsets andbase stations • Base station SAR is extremely low but you can‘t choose whether you want it or not! 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
- 56. 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
- 57. Comparison of handsets andbase 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
- 58. 4. Are MobilePhones Safe?
- 59. SAR and Safety HealthProtection 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
- 60. What are therisks? • 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
- 61. Are mobile phonessafe? 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
- 62. Stewart Report Mobile Phonesand their networks are ‘pretty’ safe There may be ‘effects’ Precautionary Approach: More research please Children Driving
- 63. Mobile Phones Suppose wediscovered ‘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
- 64. PET Scan This devicecan see you think! Glucose metabolism in this area appears to have been affected
- 65. What could wedo? 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!
- 66. 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
- 67. See you nextweek to discuss Nuclear Power Goodnight
- 68.
- 69. Perception of risk Riskis 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
- 70. Electromagnetic waves Electricity Heat How it allfits together… Atoms
- 71. A Cautionary Tale Don’ttry 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 -
- 72. Mobile Phones Suppose wediscovered ‘an effect’: What might it look like? 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) Possibility#1
- 73. No Match Click withLeft Hand
- 74. Match Click with RightHand
- 75. Task Completed with Phone OnLEFT On RIGHT OFF
- 76. RESULTS 700 750 800 850 900 950 1000 1050 1100 1 2 34 5 6 7 8 9 10 11 12 SHAM LEFT EXPOSURE RIGHT EXPOSURE ResponseTime:milliseconds Block LEFT HAND RESPONSE 'No Match' RESPONSE 700 750 800 850 900 950 1000 1050 1100 1 2 3 4 5 6 7 8 9 10 11 12 SHAM LEFT EXPOSURE RIGHT EXPOSURE ResponseTime:milliseconds Block RIGHT HAND RESPONSE Match RESPONSE 1 hour 1 hour
- 77. RESULTS With Uncertainty 700 750 800 850 900 950 1000 1050 1100 1 23 4 5 6 7 8 9 10 11 12 SHAM LEFT EXPOSURE RIGHT EXPOSURE ResponseTime:milliseconds Block LEFT HAND RESPONSE 'No Match' RESPONSE 700 750 800 850 900 950 1000 1050 1100 1 2 3 4 5 6 7 8 9 10 11 12 SHAM LEFT EXPOSURE RIGHT EXPOSURE ResponseTime:milliseconds Block RIGHT HAND RESPONSE 'Match' RESPONSE Only these two points have statistical significance
- 78. What could wedo? • 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 ?