National Physical Laboratory National Physical Laboratory –– OTM networkOTM network 2525th/th/2626th th June 2008 June 2008

NonNon--coherent light sources in hospitals coherent light sources in hospitals and the implications for risk managementand the implications for risk management

under EPAD(Opt).under EPAD(Opt).

David TaylorDavid TaylorMedical Physics Dept., Gloucestershire Royal HospitalMedical Physics Dept., Gloucestershire Royal Hospital

David.Taylor@David.Taylor@glosglos.nhs.uk.nhs.uk

NonNon--coherent lightcoherent light

Broadly follows EPAD scope:Broadly follows EPAD scope:UVUV--C, UVC, UV--B, UVB, UV--A (100 A (100 –– 400 nm)400 nm)Blue and other visible light (400 Blue and other visible light (400 –– 780nm)780nm)Near infraNear infra--red (780 red (780 -- 1400nm or IRA)1400nm or IRA)Far infraFar infra--red (1400nm red (1400nm -- 1mm, IRB & beyond)1mm, IRB & beyond)

Most hazards photochemicalMost hazards photochemical

Unlike higherUnlike higher--powered (class 3B and 4) lasers, optical powered (class 3B and 4) lasers, optical hazards are almost always photochemical to skin, hazards are almost always photochemical to skin, cornea or retinacornea or retinaGenerally, no significant tissue heating occursGenerally, no significant tissue heating occursEffects on skin and cornea usually reversibleEffects on skin and cornea usually reversibleEffects on retina may be irreversibleEffects on retina may be irreversible

Data sourcesData sources

Most hazard data derives from animal models or Most hazard data derives from animal models or actual accidents to humans:actual accidents to humans:ICNIRPICNIRPACGIHACGIHHPAHPA--RPD (previously NRPB)RPD (previously NRPB)European Physical Agents Directive (optical) of European Physical Agents Directive (optical) of 27 April 200627 April 2006EU Member States’ legislation (by 2010)EU Member States’ legislation (by 2010)

Aims of EPAD 2006Aims of EPAD 2006

… to introduce measures protecting workers from the risks … to introduce measures protecting workers from the risks associated with optical radiation, owing to its effects on the associated with optical radiation, owing to its effects on the health and safety of workers, in particular damage to the eyes health and safety of workers, in particular damage to the eyes and to the skin. These measures are intended not only to and to the skin. These measures are intended not only to ensure the health and safety of each worker on an individual ensure the health and safety of each worker on an individual basis, but also to create a minimum basis of protection for all basis, but also to create a minimum basis of protection for all Community workers, in order to avoid possible distortions of Community workers, in order to avoid possible distortions of competition.competition.

… the timely detection of adverse health effects resulting from … the timely detection of adverse health effects resulting from exposure to optical radiation.exposure to optical radiation.

Obligations of EU member statesObligations of EU member states

… a system of protection against the hazards of optical … a system of protection against the hazards of optical radiation should limit itself to a definition, free of radiation should limit itself to a definition, free of excessive detail, of the objectives to be attained, the excessive detail, of the objectives to be attained, the principles to be observed and the basic values to be principles to be observed and the basic values to be applied, in order to enable Member States to apply the applied, in order to enable Member States to apply the minimum requirements in an equivalent manner.minimum requirements in an equivalent manner.

(Member states can set lower limits if they choose, but if the (Member states can set lower limits if they choose, but if the limits set in the Directive are looser than already exist in limits set in the Directive are looser than already exist in the Member State, it’s not an excuse to slacken off)the Member State, it’s not an excuse to slacken off)

Hazard wavelength dependencyHazard wavelength dependency

Interactions with tissues are heavily dependent on Interactions with tissues are heavily dependent on wavelength:wavelength:A few A few nanometresnanometres either way can change the effect by either way can change the effect by orders of magnitudeorders of magnitudeShorter wavelengths are generally more hazardousShorter wavelengths are generally more hazardousHazards may be difficult to predict without spectral Hazards may be difficult to predict without spectral informationinformation

Hazard action spectrumHazard action spectrum

“Table 1.2 spectral weighting taking into account the wavelength dependence of the health effects of UV radiation on eye and skin” - S(λ) (dimensionless)

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Practical implications in HealthcarePractical implications in Healthcare

It doesn’t apply to patientsIt doesn’t apply to patientsIt doesn’t apply to nonIt doesn’t apply to non--occupational exposure (such as sun occupational exposure (such as sun beds) or solar exposure, even if occupational (though employers beds) or solar exposure, even if occupational (though employers should not ignore solar exposure)should not ignore solar exposure)Most of our sources don’t figure on the scale anywhere.Most of our sources don’t figure on the scale anywhere.The most hazardous will be the photochemical reactions from The most hazardous will be the photochemical reactions from 400 400 –– 500 nm on the retina, and long term exposures to UVB, 500 nm on the retina, and long term exposures to UVB, principally, on the skin.principally, on the skin.In order to do the Risk Assessments after the legislation is In order to do the Risk Assessments after the legislation is introduced, we shall have to measure a lot of kit!introduced, we shall have to measure a lot of kit!

HazardHazard--weighted UV sourcesweighted UV sources

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Weighting factors PUVA 0.0003 TL-01 0.02

Weighting factors UV6 0.13 UV21 0.25

Simplified hazard assessmentSimplified hazard assessment

Measure exposure with calibrated meter (UVA, TLMeasure exposure with calibrated meter (UVA, TL--01, 01, UV6 or UV21)UV6 or UV21)Apply weighting factor to irradianceApply weighting factor to irradianceCalculate maximum exposure time to limit the Calculate maximum exposure time to limit the weighted weighted irradiantirradiant dose to less than 40 J mdose to less than 40 J m--22 UVB or UVB or 10,000 J m10,000 J m--22 (UVA) [from Table 1.1 EPAD](UVA) [from Table 1.1 EPAD]

e.g. exposure to UV21 source measured at 1 e.g. exposure to UV21 source measured at 1 mWmW cmcm--22 gives weighted gives weighted irradiance of 0.25 irradiance of 0.25 mWmW cmcm--22, or 2.5 W/m, or 2.5 W/m22, so maximum permissible , so maximum permissible

exposure time in a working day is 40/2.5 or 16 secondsexposure time in a working day is 40/2.5 or 16 seconds

Typical hospital sourcesTypical hospital sources

Lasers are included in EPAD, but ours are mostly class 4, and Lasers are included in EPAD, but ours are mostly class 4, and the existing laser guidelines cover the hazards, exposure limitsthe existing laser guidelines cover the hazards, exposure limitsand protection and protection –– effectively no changes neededeffectively no changes neededUVB sources are the most hazardous photoUVB sources are the most hazardous photo--chemical reaction chemical reaction sources, and can turn up in strange placessources, and can turn up in strange placesVisible sources are easily avoided by blink and aversion, but Visible sources are easily avoided by blink and aversion, but special consideration must be given to unconscious or special consideration must be given to unconscious or ananææsthetisedsthetised patientspatientsMost IR sources (with the exception of the Most IR sources (with the exception of the NatusNatus HydrosunHydrosunbaby warmer) are benign. We are not iron foundry workers.baby warmer) are benign. We are not iron foundry workers.

Shortcomings of EPADShortcomings of EPAD

Exposure values are set for a typical 8 h shiftExposure values are set for a typical 8 h shiftUV exposure is cumulative, and legal exposures can easily UV exposure is cumulative, and legal exposures can easily accumulate to damaging levels over long periodsaccumulate to damaging levels over long periodsSolar exposure is not specifically included (or roofers and Solar exposure is not specifically included (or roofers and gardeners could go home at coffee time) but it is usually the gardeners could go home at coffee time) but it is usually the biggest contributor to personal UV / VIS exposurebiggest contributor to personal UV / VIS exposureLots of sources are essentially untested, and data is scantyLots of sources are essentially untested, and data is scanty

Sources we might find (1)Sources we might find (1)

UV SOURCESUV SOURCES-- mostly fluorescent tube technology falling into one of four or mostly fluorescent tube technology falling into one of four or five five

main spectra:main spectra:254 nm, TL12 (UV21), UV6 (B6), TL01, UVA.254 nm, TL12 (UV21), UV6 (B6), TL01, UVA.

Phototherapy Phototherapy –– UVA (& Wood’s Light), TL01 (& UV6, UV21) UVA (& Wood’s Light), TL01 (& UV6, UV21) CSSD steriliser, pathology transCSSD steriliser, pathology trans--illuminator illuminator –– (254nm, TL12, (254nm, TL12, UV6) UV6) Infection control training (UVA or UVA1)Infection control training (UVA or UVA1)

UV source spectraUV source spectra

The great majority of UV sources are one of these four: The great majority of UV sources are one of these four: UV21UV21, , UV6UV6, , TL01TL01 and and UVAUVA

Mercury arc lampsMercury arc lamps

Filtered mercury arc lamps ( UV-A, UV-B, UV-everything ) are occasionally found – note the intense blue, green & yellow spectral components. These are a greater hazard than the UV since they penetrate to the retina. Tinted eye protection MUST be worn.

Phototherapy unitPhototherapy unit

Enclosed cabins are less hazardous than ‘open’ hand/foot units, and PUVA lamps are less hazardous than UV21, UV6 or TL01 (in that order)

CSSD and pathologyCSSD and pathology

UV transilluminators are like hand/foot units, with 254nm, TL12 or TL01 fluorescent tubes, for examining specimen slides for fluorescence. Water sterilisers use 254 nm tubes inside a water casing to destroy bacteria as water flows through.

Sources we might find (2)Sources we might find (2)

VISIBLE SOURCESVISIBLE SOURCES

BlueBlue light in SCBU for neonatal HBR light in SCBU for neonatal HBR –– babies’ eyes MUST be babies’ eyes MUST be covered or orangecovered or orange--screenedscreenedRedRed light in Phototherapy for PDTlight in Phototherapy for PDTWhiteWhite light in theatre from endoscopes, surgical light in theatre from endoscopes, surgical luminairesluminairesand inspection lampsand inspection lamps

Blink and aversion will work for us, but not for babies or Blink and aversion will work for us, but not for babies or anaesthetised patients facing upwards on the tableanaesthetised patients facing upwards on the table

Blue and red light sourcesBlue and red light sources

PDT sources (L) come in various light source technologies, mostly LED today. Blue light for neonatal HBR (R) is only slowly turning to LEDs. The rare Crigler-Najjar cases (centre) must spend hours under blue light (usually fluorescent tube arrays) to clear bilirubin. Shorter wavelengths are more hazardous than longer (red) ones.

White light sourcesWhite light sources

Multiple incandescent sources (L) are now superseded by multi-head LEDs (centre) or distributed arrays of LEDs (R). BS EN 60601-2-41 requires a minimum of 80,000 lux output, and some examples achieve 140,000 lux or more. Surgeons look in the same direction as the light, but may be at risk during extended theatre work.

Endoscopes have highly intense Xenon sources, but have interlocks to prevent light emission when the delivery duct is disconnected.

Sources we might find (3)Sources we might find (3)

INFRAINFRA--REDRED

Mostly long wavelength for warming purposesMostly long wavelength for warming purposes

PhysiotherapyPhysiotherapyNeonatologyNeonatology

IR babyIR baby--warmerswarmers

NatusNatus 300N 300N HydrosunHydrosun > > (now withdrawn) emitted (now withdrawn) emitted mostly in IRA mostly in IRA -- shorter than shorter than 1400 nm, and was an 1400 nm, and was an invisible retinal hazard to the invisible retinal hazard to the staff working around the staff working around the neonate.neonate.

Sources you might not have thought aboutSources you might not have thought about

Ordinary domestic/office fluorescent lighting (left) emits measurable UVA (unless specified UV-free). The Da-Ro handwash training device (centre) contains a UV source, and the Rio UV Clean Light (right) is handy around the house to zap ‘any DNA-based organisms’ with its 254 nm light-sabre beam.

Rio UV Clean LightRio UV Clean Light

The answer to a housewife’s prayer:The answer to a housewife’s prayer:

“Product detail“Product detailEliminates dust mites and bacteria in mattresses or pillows in sEliminates dust mites and bacteria in mattresses or pillows in seconds!econds!Simply shine the UV light over the surface to eliminate viruses,Simply shine the UV light over the surface to eliminate viruses, bacteria, germs and dustmites. bacteria, germs and dustmites. Safe for all fabrics, furs and surface, even antiques. Safe for all fabrics, furs and surface, even antiques. Ideal for hard to clean items such as telephones, computer keyboIdeal for hard to clean items such as telephones, computer keyboards, earphones etc. ards, earphones etc. Ideal for ensuring your kitchen utensils and toothbrushes are hyIdeal for ensuring your kitchen utensils and toothbrushes are hygienically clean. gienically clean. Helps relieve allergies and conditions caused by dust mites. Helps relieve allergies and conditions caused by dust mites. No residue or odors. No residue or odors. No harsh chemicals. “No harsh chemicals. “

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This slide originally showed a promotional video for the Enputech PureLight hand-held

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ConclusionsConclusions

NonNon--coherent sources in clinical settings will fall into one of threcoherent sources in clinical settings will fall into one of three main e main groups: groups: –– a) not a problem under ordinary circumstancesa) not a problem under ordinary circumstances, , –– b) might be a problem under certain circumstancesb) might be a problem under certain circumstances, , –– c) definitely a hazard under ordinary circumstancesc) definitely a hazard under ordinary circumstances..

NonNon--coherent sources in clinical settings are mostly low risk, the wcoherent sources in clinical settings are mostly low risk, the worst orst being UVB and UVC emitters (but don’t overlook ‘’blue hazard’)being UVB and UVC emitters (but don’t overlook ‘’blue hazard’)Special consideration may need to be given to anaesthetised patiSpecial consideration may need to be given to anaesthetised patients ents or neonatesor neonatesLasers continue to be the most powerful sources, but other sourcLasers continue to be the most powerful sources, but other sources are es are not so scary and are less respectednot so scary and are less respectedPhototherapy units ought to be the most hazardous, but it’s morePhototherapy units ought to be the most hazardous, but it’s more likely likely that ‘unknown’ sources will be mishandled morethat ‘unknown’ sources will be mishandled moreWhen EPAD is translated into UK law, risk assessments will have When EPAD is translated into UK law, risk assessments will have to be to be made of many sources previously ignoredmade of many sources previously ignoredWe can reduce this workload by sharing data on hospital sources,We can reduce this workload by sharing data on hospital sources, and and building a ‘library’ of building a ‘library’ of greengreen, , amberamber, and , and red red source situationssource situations