Wireless computer safetyJim Jamieson / SSERCReviews and guidelinesRisk of harmSafety standardsProduct complianceNRPB surveyLitigationConclusion

SSERC

WLAN infrastructureAccess point

(Base station)Distribution system (hard-wired link)Stations(laptops or desktop computers)Radio link

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Radio sourcesRF sourceFrequencyPowerWLAN2.4 GHz100 mWMicrowave oven2.4 GHz1 kWMobile phone base station0.9 / 1.8 GHz80 WMobile phone0.9 / 1.8 GHz250 mWUHF broadcast TV500 MHzVHF broadcast radio100 MHz

SSERC

Health and safety guidelinesNRPB guidelines (1993)safety factor of 10same restrictions for general public and occupational workersICNIRP (International Commission on Non-Ionizing Radiation Protection) Guidelines (1998)safety factor of 10 (occupational workers)safety factor of 50 (general public)European Council Recommendation House of Commons recommendation

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Recent scientific reportsIEGMP Recommendations (2000)(Independent Expert Group on Mobile Phones)(Stewart Report)NRPB Proposals (2003)Exposure guidelines built upon scientific evidenceEpidemiological studiesExperimental studies on humansExperimental studies on animalsCellular studiesComputational dosimetry

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Epidemiological evidence from RF exposuresNo indication of increase in risk of cancerbut not conclusiveNo indication of raised risks of non-cancer mortality or adverse pregnanciesMortality can result from high or low temperatures

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Biological effects of RF radiationHeat-related disordersNo direct experimental evidence of risk of cancerCaution: not possible to dismiss all possibilitiesNo significant threat to reproduction or developmentSubtle, transient effects on brain or behaviour

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Computational dosimetryTo derive RF EMF reference levels from solving Maxwells equations numerically, in fine resolution, to models of the bodyModelling can provide differential informationAdults/childrenMales/femalesEmbryo/foetusWhole body/body partsBody posture

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The Precautionary PrincipleMay be expressed asBetter safe than sorryErr on the side of cautionTake steps to avoid possible health damage, in the face of insufficient evidenceApplied byIEGMP on mobile phone use by childrenNRPB on exposure of children to power EMFsNRPB on RF mobile phone radiation

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NRPB proposal and viewThe UK should adopt the ICNIRP Guidelines (2003)There is no problem with the safety of WLAN (2003)

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Dosimetric quantitiesSymbolQuantityUnitSARSpecific energy absorptionW/kgrateSPower densityW/m2

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Basis of ICNIRP Guidelines4 W/kgEstablished biological and healthheating effect after 30 min exposure0.4 W/kgOccupational basic restriction0.08 W/kgPublic basic restriction, whole body SARSafety guidelines take into consideration the potentially higher sensitivity in certain population groups such as infants and children

SSERC

ICNIRP GuidelinesBasic restrictions:Whole body SAR0.08 W/kgLocalized SAR2 W/kg(head, trunk)Localized SAR4 W/kg(limbs)

Reference level:Power density10 W/m2

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Product compliance with standardsManu-IEEEENCEICNIRPIndependentFacturer802.300308markedcom-test report-11bpliance3ComYesYesYesYesYesAirConnectAgereYesYesYesORINOCOApple iBookYesAirPortCisco AirportYesYesYesNokiaYesYesNortelYesYes

SSERC

Independent test report on 3ComMaximum radiated power = 80 mWwithin 100 mW specified by EN 300 328The measured peak 1-g SAR lies between 0.012 and 0.015 W/kgwithin ICNIRP Guidelines of 2 W/kg (localized SAR over 10 g tissue)

SSERC

Radio wave strengths from WLANs in Scottish schools2 East Lothian primary schools surveyed in a joint investigation between NRPB and SSERCScope of investigation:to measure radio wave strengths and comment on peoples exposure in relation to accepted safety guidelines

SSERC

Hand-held Surveying ProbeICNIRP public reference level is 10 W m-2 in the frequency range 2.4 - 2.5 GHzSensitivity threshold of the probe used was around 0.5 W m-2 Probe gave no reading with its sensor held next to base stations and computer terminalsCompliance with guidelines is assured for distances greater than 10 cmProbe is unreliable at lesser distances due to its large size (sensors are around 5 cm)

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SSERC

Wireless LAN Radio Signal

SSERC

Primary School ASite: ground floor, directly in front of base station, 6 m distant

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Primary School ASite: ground floor, directly in front of base station, 6 m distant

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Primary School BSite: first floor, base station in corridor, survey in classroom

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Primary School BSite: first floor, base station in corridor, survey in classroom

SSERC

SummaryWireless LAN transmitters use very low total radiated powers ~ 10s mWRadio signal strengths range greatly inside schoolsThe WLAN signals are comparable in strength to those from distant transmitters Exposures at the locations surveyed were very much below guideline levelsThere is no problem with the safety of WLAN

SSERC

But the courts will decide!Case being heard in the circuit court of Cook County, IllinoisDefendants have installed WLAN in each of the school buildings under their jurisdictionNature of the case is that the defendants have ignored the substantial body of evidence that high frequency electromagnetic radiation poses substantial and serious health risks, particularly to growing children. The defendants have thereby breached their duties of care to the children of their school.

SSERC

Concluding commentYou get justice in the next worldIn this world, you only get the law

SSERC

SSERC/J Jamieson