健康安全环保管理体系-高压环境下的工作暴露极限(英文)

OccupationalexposurelimitsforhyperbaricconditionsPage3of23HealthandSafetyExecutiveContentsIntroduction4Summary51Background72Generalinformationonexposure82.1Occupationalactivitiesinvolvinghyperbaricexposure83ExtrapolationofOELstotakeaccountofincreasedabsolutepressure103.1Basicprinciples103.1.1Partialpressure103.1.2Pressurechanges113.2Toxicologicalresponsetochemicalsunderhyperbaricconditions113.2.1Experimentaldataonthetoxicokineticbehaviourofsubstancesunderhyperbaricconditions123.2.2Theoreticalconsiderations143.2.2.1Systemictoxicity143.2.2.2Localtoxicity143.3Summaryandconclusions154ExtrapolationofOELstotakeaccountofincreasedexposureduration164.1Introduction164.2Adjustmentof8-hourTWAOEL164.2.1Mathematicalmodels164.2.2Linearadjustment174.3AdjustmentofIS-minuteSTELOEL185Overallsummaryandconclusions196References21Appendix22Furtherinformation23OccupationalexposurelimitsforhyperbaricconditionsPage4of23HealthandSafetyExecutiveIntroductionThisHazardAssessmentDocumenthasbeenpublishedbytheUKHealthandSafetyExecutive(HSE)andisaimedatatechnicalaudience.InGreatBritain,substanceswhichmaycauseharmtohealtharesubjecttotheControlofSubstancesHazardoustoHealthRegulations(COSHH)1999.TheseRegulationsrequireemployerstoprevent,orifthisisnotreasonablypractical,adequatelycontrolemployees’exposuretohazardoussubstances.HazardAssessmentDocumentsareproducedtofacilitatethedevelopmentofHSE’sregulatorypositiononaspecifichealthrelatedissue,whichmayrelatetoanindividualhazardoussubstanceormayinvolveconsiderationofmoregeneralissuesrelatedtochemicalsandillhealth.Thedocumentsinthisseriescoverissuesrelatingonlytotoxicologicalhazard;otherdocumentseriesaddressissueswhichinvolveconsiderationofoccupationalexposureandrisk:ExposureAssessmentDocument-EH74series;n RiskAssessmentDocument-EH72seriesn ThedatainHazardAssessmentDocumentsareassessedandendorsedbytheWorkingGroupontheAssessmentofToxicChemicals(WATCH).WATCHmakesrecommendationstotheAdvisoryCommitteeonToxicSubstances(ACTS)onallaspectsofchemicalshazardandriskassessmentandriskmanagementissues,includingrecommendationsforOccupationalExposureLimitsandotheraspectsofoccupationalhealthriskmanagement,aspartofitsassessmentofthesubstanceunderdiscussion.HazardAssessmentDocumentsarepublishedaftertheirendorsementbyWATCH.DetailsofhowtoobtainHSEpublicationsareonthebackcover.OccupationalexposurelimitsforhyperbaricconditionsPage5of23HealthandSafetyExecutiveSummaryExposuretoairbornecontaminantsunderhyperbaricconditionsarisesinoccupationssuchasdivingandcompressedairtunnellingwork.OccupationalExposureLimits(OELs)establishedinGreatBritainareapotentiallyimportantelementoftheregulatoryapproachtothecontrolofchemicalexposureintheseoccupationalsettings.However,OELsaredevelopedforexposuresatnormalpressureinair,andonthebasisofanexposurepatternof8hoursperday,5daysperweek.Inthehyperbaricsetting,OELsmustapplytoconditionsofelevatedpressureand,inthecaseofsaturationdiving,toperiodsofcontinuousexposure(24-hoursperdayforaperiodofdaysorweeks)breathinghelium-oxygenmixtures.ThereforeOELswhichrepresentadequatecontrolofexposureforconventionaloccupationalscenariosatnormalpressurewillnotnecessarilyrepresentadequatecontrolunderhyperbaricconditions.Therearenoexperimentaldata,inhumansoranimals,whichexplorethetoxicityarisingfromexposuretoindustrialchemicalsunderhyperbaricexposureconditions.Limiteddataareavailableonthetoxicokineticbehaviourofsubstancesunderhyperbaricconditions.Thus,thereisnoreliableexperimentaldatabasefromwhichtoderiveOELsforindividualsubstancesofconcerninthehyperbaricsetting.Intheabsenceofdata,itisconsideredappropriatetoadoptagenericapproachtoextrapolateOELsderivedforstandardoccupationalexposureconditionstothehyperbaricenvironment.However,inadoptingagenericapproach,theresultanthyperbaricOELs(referredtoasHOELs)should,asfaraspossible,provideatleastthesamelevelofassuranceofhealthprotectionasdotheequivalentOELsunderconventionaloccupationalexposureconditions.ThisapplieswhethertheOELisaMaximumExposureLimit(MEL)oranOccupationalExposureStandard(OES).DefinitionsofthesetwotypesoflimitsaregivenintheHSEpublication,EH40.ThekeyissuesinvolvedinextrapolationofOELstoHOELsaretheeffectsoftheincreaseintheabsolutepressureand,specificallyinthecaseofsaturationdiving,thepotentialforextendedcontinuousexposuretobackgroundlevelsofcontaminantsinthedivinghabitat.InrelationtotheextrapolationofOELstotakeaccountoftheincreaseinabsolutepressure,basedontheoreticalconsiderationsandthelimitedexperimentalevidenceavailable,itisconcludedthatadjustmentonthebasisofpartialpressureisappropriate.Theneedforthisextrapolationappliesonlytosubstancesingaseousorvapourform.TheOEL(expressedinppmunits)shouldbelinearlyadjustedtoensurethatthesamepartialpressureismaintainedunderallhyperbaricconditions.ThiscanalsobeachievedbyadherencetotheOELexpressedinmg.m-3units.Inrelationtoadjustmentof8-hourtime-weightedaverage(TWA)OELsforcontinuousexposureduringsaturationdiving,linearextrapolationonthebasisofaconcentrationxtimerelationshipisproposed.Thus,theOELshouldbeadjusteddownwardstotakeaccountof16