monitoring strategies for toxic substances · 22 measuring your employees’ personal exposure, by...
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Health and Safety Executive
Monitoring strategies for toxic substances
This is a free-to-download, web-friendly version of HSG173 (Second edition, published 2006). This version has been adapted for online use from HSE’s current printed version.
Youcanbuythebookatwww.hsebooks.co.ukandmostgoodbookshops.
ISBN 978 0 7176 6188 6Price £6.95
Thisguidancehighlightsproceduresinhowtoinvestigateemployeeexposuretotoxicsubstancesthroughinhalationthatmaybehazardoustohealthandhowtocontrolthenatureofandextenttothisexposure.
Itisaimedatallemployersingeneralandatallhealthandsafetyprofessionalswhereitcanbeausefulintroductiontothesubjectaswellasensuringthatyouaredoingenoughtocomplywiththelaw.
Italsotargetsnon-specialistsinordertohelpwithgaininganinitialunderstandinginordertobeabletoaskquestionsandseekadvicefromconsultantsandothers.
HSE Books
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Health and Safety Executive
© Crown copyright 2006
Firstpublished1997Secondedition2006
ISBN9780717661886
Allrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans(electronic,mechanical,photocopying,recordingorotherwise)withoutthepriorwrittenpermissionofthecopyrightowner.
Applicationsforreproductionshouldbemadeinwritingto:TheOfficeofPublicSectorInformation,InformationPolicyTeam,Kew,Richmond,SurreyTW94DUore-mail:[email protected]
ThisCodehasbeenapprovedbytheHealthandSafetyExecutive,withtheconsentoftheSecretaryofState.Itgivespracticaladviceonhowtocomplywiththelaw.IfyoufollowtheadviceyouwillbedoingenoughtocomplywiththelawinrespectofthosespecificmattersonwhichtheCodegivesadvice.YoumayusealternativemethodstothosesetoutintheCodeinordertocomplywiththelaw.
However,theCodehasaspeciallegalstatus.Ifyouareprosecutedforbreachofhealthandsafetylaw,anditisprovedthatyoudidnotfollowtherelevantprovisionsoftheCode,youwillneedtoshowthatyouhavecompliedwiththelawinsomeotherwayoraCourtwillfindyouatfault.
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ContentsIntroduction 4
Legislative requirements 5
Exposure limits 5
Inhalation exposure monitoring 6Whyyoushoulddevelopamonitoringstrategy6Personalmonitoring6Fixedplacemonitoring7
Approaches to inhalation exposure assessment and monitoring 7Initialappraisal 10Basicsurvey11Detailedsurvey12Reappraisal13Routinemonitoring13Interpretationofresults14Compliancetesting15
Appendix 1: Factors influencing airborne contaminant concentrations 16
Appendix 2: Variables influencing the design of monitoring strategies 17
Appendix 3: Core information 20
References 21
Further information 23
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Monitoring strategies for toxic substancesThisguidanceisissuedbytheHealthandSafetyExecutive.Followingtheguidanceisnotcompulsoryandyouarefreetotakeotheraction.Butifyoudofollowtheguidanceyouwillnormallybedoingenoughtocomplywiththelaw.Healthandsafetyinspectorsseektosecurecompliancewiththelawandmayrefertothisguidanceasillustratinggoodpractice.
Introduction1 Thisguidanceisaddressedprimarilytoemployers.FirstpublishedasEH42,itwasthenrevisedtomakeitmoreaccessibletonon-specialistssothattheycanuseitasanintroductiontothedesignofinhalationexposuremonitoringstrategies.
2 Youcanusetheseprocedurestoinvestigateemployeeexposure,byinhalation,tosubstanceshazardoustohealth.Theywillhelpyouinvestigatethenature,extentandcontrolofemployeeexposure.
3 Theguidancewillalsohelpyoutounderstandandaskquestionsaboutanyinformationoradvicethatyoumayreceivefromconsultantsandothers.
4 Healthandsafetyprofessionalsmayalsousethisguidanceasanintroductiontothesubject.Formoredetailedinformationonspecificissues,seeReferences.
5 TheControlofSubstancesHazardoustoHealthRegulations2002(asamended)(COSHH),1regulation2,statesthatsubstancesandpreparations(mixturesoftwoormoresubstances)hazardoustohealthinclude:
n substancesinPart1oftheApproved supply list2asdangerousforsupplywithinthemeaningoftheChemicals(HazardInformationandPackagingforSupply)Regulations2002(CHIP)3andforwhichanindicationofdangerspecifiedforthesubstanceisverytoxic,toxic,harmful,corrosiveorirritant;
n substanceswithaworkplaceexposurelimit(WEL);n biologicalagents;n dustsofanykindinsubstantialconcentrations;andn anysubstancethatcreatesarisktohealthbecauseofchemicalortoxicological
properties.
6 Theinformationinthisguidanceisnotsuitablefor:
n assessingexposuretomicro-organisms;n assessingexposurefromnon-inhalationroutes(ieskinabsorptionand
ingestion);n assessingsafetyissuessuchasflammability,explosivehazardsand
asphyxiants;andn measuringemissionsofvolatileorganiccompounds(VOCs)underthe
EnvironmentalProtectionAct1990.
7 Youneedtobeawarethatsubstanceshazardoustohealthcanenterthebodybyingestion(ieswallowingthesubstance)andskinabsorption(iethroughtheskin)aswellasbyinhalation.Thismeansthatinsomesituationsyoumayalsoneedtomeasurethetotalamountofasubstancethathasenteredanemployee’sbody.
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Thisisdoneusingatechniquecalledbiologicalmonitoring.
8 Biologicalmonitoringisoutsidethescopeofthisguidance.Forfurtherinformationaboutbiologicalmonitoring,seeBiological monitoring in the workplace: A guide to its practical application to chemical exposure.4
9 Therearespecificlegislativerequirementsforlead,asbestosandrespirabledustinmines.Theprinciplesdescribedinthisguidanceapplyequallytomonitoringinhalationexposuretothesesubstances.
Legislative requirements 10 TheprincipalregulationsgoverningsubstanceshazardoustohealtharetheCOSHHRegulations.Thecentralrequirementsare:
n regulation6(1)-youshouldcarryoutasuitableandsufficientassessmentoftheriskstothehealthofyouremployeesandanyotherpersonwhomaybeaffectedbyyourwork,iftheyareexposedtosubstanceshazardoustohealth;
n regulation7(1)-youshouldensurethatexposureispreventedor,whenthisisnotreasonablypracticable,adequatelycontrolled.
11 IfyoucomplywithCOSHHregulation6(1)youhavefulfilledyourdutiesunderregulation3oftheManagementofHealthandSafetyatWorkRegulations1999.5Remember,thisonlyappliestosubstanceshazardoustohealth,egnotphysicalhazardssuchasnoise,radiationandmachineryguarding.Youwillneedtoassessandcontrolanyphysicalhazardsandrisksseparately.
12 Thelegalrequirementformonitoringinhalationexposureisgiveninregulation10oftheCOSHHRegulations.Itrequiresyoutocarryoutmonitoringif:
n itisnotimmediatelyobvioustoyouwhetherthereisarisktothehealthofyouremployees;and
n thereisasuitableprocedurewhichyoucanusetomeasureexposure.
13 Regulation10isclarifiedindetailintheCOSHHApproved Code of Practice.6Thisstatesthatmonitoringisrequiredwhen:
n failureordeteriorationofthecontrolmeasurescouldresultinaserioushealtheffect;
n whenmeasurementisneededtoensureaWELoranyself-imposed(in-house)workingstandardisnotexceeded;or
n asanadditionalcheckontheeffectivenessofanycontrolmeasuresprovidedinaccordancewithregulation7,andalwaysinthecaseofthesubstancesorprocessesspecifiedinSchedule5totheRegulations;
n whenanychangeoccursintheconditionsaffectingemployees’exposurewhichcouldmeanthatadequatecontrolisnolongerbeingmaintained.
Exposure limits 14 AnumberofsubstanceshazardoustohealthintheworkplacehavebeenassignedWorkplaceExposureLimits(WELs).Theseareaveragedovereight-houror15-minutereferenceperiods.
15 AWEListhemaximumconcentrationofanairbornesubstanceaveragedover
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areferenceperiod,towhichemployeesmaybeexposedbyinhalation.
16 WELsshouldnotbeconsideredahardandfastlinebetweensafeandunsafe.Theprinciplesofgoodcontrolpractice(COSHH2002,Schedule2A),ifappliedcorrectly,shouldensureexposuresarebelowanyrelevantWEL.
17 TocomplywiththerequirementsinCOSHHregulation7(7)(c)(exposuretoasthmagensandcarcinogens)toreduceexposuresofarasisreasonablypracticable,employersmayneedtocarryoutaprogrammeofairmonitoringinaccordancewithregulation10.ThiswillbegenerallynecessaryunlesstheriskassessmentshowstheexposureisunlikelytoeverexceedtheWEL.
18 ThemajorityofsubstancesusedinindustryhavenotbeengivenWELs,butthisdoesnotmeanthattheyaresafe.Inthesecircumstancesyouneedtoensurethatexposureiscontrolledtoaleveltowhichnearlyalltheworkingpopulationcouldbeexposeddayafterday,withoutadverseeffectsontheirhealth.
19 Tojudgewhetherthereisarisktothehealthofyouremployeesinthesecircumstances,youmaybeabletouselimitsproducedbyotherbodies,suchasGuide to occupational exposure values 20058fromtheAmericanConferenceofGovernmentalIndustrialHygienists.Inallcases,theprinciplesofgoodcontrolpracticeshouldbeappliedinthefirstinstance.
20 Youcanalsousetheinformationprovidedbyyourmanufacturerorsupplier,undertheChemicals(HazardInformationandPackagingforSupply)Regulations2002,3tosetin-housestandards.Forfurtherinformationaboutsettingin-housestandards,seeReferences.
Inhalation exposure monitoring Why you should develop a monitoring strategy
21 Asanemployer,youmaywishtodevelopamonitoringstrategy.Thereareanumberofgoodreasonstodothis,including:
n healthriskassessment;n compliancewithWELs;n tohelptowardsthedesignofexposurecontrolmeasures;n checkingtheeffectivenessofyourcontrolmeasures;n informingyouremployeesofthepatternofexposureandlevelofrisk;n toindicatetheneedforhealthsurveillance;n establishingin-houseexposurestandards,wherenecessary;n forinsurancepurposes;andn tocontributetoepidemiologicalstudies.
Personal monitoring
22 Measuringyouremployees’personalexposure,byinhalation,tosubstanceshazardoustohealthisnotthesameasmeasuringtheamountataparticularfixedsiteintheworkplace.Fixedsitescanbeeither:
n atthesourceofemissionofasubstancehazardoustohealth;orn atanotherareaintheworkplace,awayfromthesource.
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23 Personalmonitoringisusedtoestablishtheconcentrationofanairbornesubstancewithintheemployee’sbreathingzone.ThisisexplainedinmoredetailinAppendix2,paragraphs10-13.Withtheexceptionofvinylchloride,WELsrelatetopersonalexposure.
24 Youwillneedtoconsiderwhetherpersonalexposuremonitoringwillbeusefulwhenassessingtheriskstoyouremployeesfromworkingwithsubstanceshazardoustohealth.
25 Remember,exposuremonitoringisnotanalternativetotheadequatecontrolofexposureandprogrammescanbetime-consuming,labour-intensiveandexpensive.Therefore,itisimportantthatyouestablish:
n aclearneedformonitoring;n anunderstandingofthefactorslikelytoinfluencetheexposure;andn astrategywhichisfitforthepurpose.
Fixed place monitoring
26 MostWELsrefertopersonalexposures.Youcanalsousefixedplaceorstaticmonitoringtoobtaininformationonthelikelysourcescontributingtotheexposure.However,fixedplacemonitoringdoesnotusuallyreflecttheamountthatoneofyouremployeescouldbreathein,whichdeterminestherisktohealth.
27 Youmaytakefixedplacesamples:
n tochecktheeffectivenessofyourcontrolmeasures;n toidentifyemissionsources;n todeterminebackgroundworkplacecontaminantconcentrations;n iftherearenosuitablepersonalmonitoringmethodsavailable;n whenwearingpersonalmonitoringequipmentmayintroduceadditional
hazards;n whencontinuousmonitoringalarmsystemsareinstalled;andn inthecaseofvinylchloride.
Approaches to inhalation exposure assessment and monitoring 28 Becauseofvariationsinplant,process,workandotherconditionsitisdifficulttodrawconclusionsaboutlong-termexposurepatternsonthebasisofasinglemeasurementofexposureatonepointintime(seeAppendices1and2).
29 Youwillneedtomakesurethatthemonitoringstrategyyoudeviseandthewayyouinterprettheresultsallowsyoutodrawconclusionswithconfidenceabouttherisktothehealthofyouremployees.
30 Exposuremonitoringcanbetime-consumingandexpensive.But,ifyoufollowtheadviceoutlinedinthisguidanceyouwillgetthemostoutofamonitoringexercise,atareasonablecost.
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31 Eachstageintheindustrialmanufactureanduseofsubstanceshazardoustohealthinvolvesdifferenttasks.Eachofthemcanpresentdifferentexposureconditions.Figures1a-1eshowhowexposurecanvary,oftenovershortperiodsoftime,duringashift.
Figure 1a:Anexposurepatternforaworkingshift(8hours)
Figure 1b:Variationsinexposureovera24-hourperiod
Figure 1c:Dailyvariationsinshiftaverages(8-hourtime-weightedaverages)
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Figure 1d:Continuousmonitoringtrace(egpaintsprayingshowingintermittentnatureofjob)
Figure 1e:15-minutetime-weightedaverageexposure
32 Thedesignofamonitoringstrategywillbegreatlyinfluencedbythe:
n aimsofthesurvey;andn conditionspresentedbytheprocess.
33 Thescopeoftheexposureassessmentwilldependonhowcomplicatedtheprocessis.However,inmanysituationsitmaybepossibletodeterminethelikelylevelofexposurewithouttakingmeasurements.Figure2illustratesastructuredapproachforevaluatingexposurebyinhalation.
34 Thefollowingparagraphsoutlinethisapproachtomonitoringinhalationexposuretosubstanceshazardoustohealth.
35 Noteverysituationiscomplexenoughtowarrantsuchastructuredapproach,forexamplemonitoringexposuretosolventvapoursduringhandpaintinginawell-ventilatedroom.Inthesesituationsyoucouldselectorcombinedifferentaspectsofthestructuredapproach.
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Figure 2:Astructuredapproachforassessingexposuretosubstanceshazardoustohealthbyinhalation
36 Youmayconsidercombiningaspectsofthebasicanddetailedsurveys.Thismayinvolvethesimultaneoususeofsmoketubes,airvelocitymeters,chemicalindicatortubesandpersonalsamplingequipment.
37 Standardsforgeneralperformancerequirements,forprocedurestodeterminetheconcentrationofsubstanceshazardoustohealthinworkplaceair,canbefoundinBSEN482,Workplace atmospheres - general requirements for the performance of procedures for the measurement of chemical agents.9
Initial appraisal
38 TheinitialappraisalisanimportantpartofthestrategydescribedinFigure2.Ithelpsyouestablishtheneedfor,andtheextentof,exposuremonitoring.Thiswillhelpyoutodecideon:
n thehazards;n thepotentialrisks;andn whethermoreinformationisneeded(egdoyouneedtocarryoutmonitoringto
obtainanestimateoftheexposureofyouremployeestosubstanceshazardoustohealth?).
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39 Thefirststageoftheinitialappraisalrequiresyoutofindoutinformationonavarietyoffactors,forexample:
n thesubstancethatyouremployeesareexposedto;n thehazardousandphysicalpropertiesofthesubstance;n theairborneformsofthesubstance;n theprocessesoroperationswhereexposuresarelikelytooccur;n thenumber,typeandpositionofthesourcesfromwhichthesubstancemay
bereleased;n whichgroupsofemployeesaremostlikelytobeexposed;n thepatternanddurationofexposure;n workpractices;n themeansbywhichthereleaseofthesubstanceiscontrolled;n whetherrespiratoryprotectiveequipmentand/orotherpersonalprotective
equipmentarewornandtheireffectiveness;andn whataretheWELs,limitsfromotherbodiesorin-housestandardsforthe
substanceinvolved.
40 Youcanobtainthisinformationfromanumberofsources,forexample:
n labelsoncontainersandpackages;n manufacturers’andsuppliers’safetydatasheets;n HSEpublications;n technicalliteraturefromtradeassociations;andn pastexperience.
41 Whenyouhavethisinformation,youcanusesimplequalitativeteststohelpyoudecidewhethertheremaybearisktothehealthofyouremployees,forexample:
n smoketubescanillustratethemovementofairundertheinfluenceofdraughts,generalandlocalexhaustventilationsystems,andshowwhattheeffectsare;
n adustlampallowsyoutoseeveryfineairborneparticleswhichareinvisibleundernormallight.Thishelpsyouidentifyemissionsourcesandwatchthemovementofairbornedust.FurtherhelpontheuseofdustlampscanbefoundinHSE’sThe dust lamp: A simple tool for observing the presence of airborne particles;10
n smellcanalsobeusedasanindicatorofcontamination.Butrememberthisisanunreliablemethod.
42 Basedontheinformationcollectedduringtheinitialappraisalyoumayconcludethatthelevelofexposure,byinhalation,isacceptable.Ifthisisthecase,itmightnotbenecessarytocarryoutexposuremonitoring.
43 Remember,thelevelofexposureofyouremployeestoasubstancehazardoustohealthcanchange.Thismeansthatyourinitialassessmentmaynolongerbevalid.Youshouldalwaysbeawareoftheneedforexposuremonitoring.
Basic survey
44 Youwillneedtoproceedtoabasicsurveywhentheinitialappraisalsuggests:
n thereisanexposureriskbuttheextentoftheriskisuncertain;n majorchangeshavebeenmadetotheprocess,proceduresorcontrol
measuressincethelastassessment;n unusualorperiodicoperationsareplanned;n anewprocessisbeingcommissioned;or
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n anewWELorin-housestandardhasbeenset.
45 Thebasicsurveyestimatesyouremployees’personalexposureandprovidesanindicationoftheefficiencyofprocessandengineeringcontrols.
46 Inthecaseofabasicsurveyitisbesttolookatworst-casesituations,suchasthe‘dirtiest’,orsituationsyouremployeesmakethemostcomplaintsabout.
47 Beforemonitoringyouneedtoidentifythoseemployeeslikelytobeatsignificantriskofexposurealongwiththeconditionsgivingrisetothem.Appendix1setsoutthefactorsthatinfluenceairborneconcentrationsandAppendix2outlinesthevariableswhichinfluencethedesignofmonitoringstrategies.Thisinformationwillhelpyoudecidewhatneedstobedone.
48 Youcanusesemi-quantitativemethodstoestimatepersonalexposure.Thesegiveyouaroughnumericalestimateofexposure.Somesemi-quantitativemethodsarecomparativelyinexpensiveandeasytouse.
49 Semi-quantitativemethodsrangefromsimpletechniques,suchaschemicalindicatortubes(wheretheabsorbentgranulesinthetubechangecolourwhenaknownamountofair,containingachemical,isdrawnthrough)tomorecomplexmethodswhichrequirespecialistknowledge,including:
n computerexposuremodelling;andn organicvapouranalyserssuchasphotoionisationdetectors,portablegas
chromatographsandinfra-redanalysers.
50 Alternatively,validatedlaboratory-basedsamplingandanalyticaltechniquescanbeused(seeAppendix2).Ifyouareunsurehowtousesuchtechniques,youcouldconsultahealthandsafetyprofessionalsuchasanoccupationalhygienist.
51 Airvelocitymeterscanbeusedtoassesslocalexhaustventilationsystemstoensurethattheyareperforminginaccordancewiththedesignspecification.Also,thequalitativemethodsusedintheinitialappraisalcanbeusedhere.
52 Thebasicsurveymayhighlightdefectsanddeficienciesincontrolstrategies.Basedonthisandinformationgatheredduringtheinitialappraisalyoumayconcludethatthecontrolofinhalationexposureisacceptable.Iftheconclusionisnotcertain,youhavetwochoices:
n carryoutadetailedsurveyandtakeremedialactionasnecessary;orn takedirectactiontocontrolexposure.
Detailed survey
53 Youcanusethisapproachwhen:
n theextentandpatternofexposurecannotbeconfidentlyassessedbyabasicsurvey;
n exposureishighlyvariablebetweenemployeesdoingsimilartasks;n carcinogenicsubstances(riskphraseR45andR49),respiratorysensitisers(risk
phraseR42andR42/43)ormutagens(riskphraseR46)areinvolved;n theinitialappraisalandbasicsurveysuggestthat:
- thetime-weightedpersonalexposuremaybeveryclosetotheWEL,limitsfromanotherbodyorin-housestandard;and
- thecostofadditionalcontrolmeasurescannotbejustifiedwithoutevidenceoftheextentofexposurevariability;and
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n undertakingmajormaintenanceandone-offjobssuchasplantdecommissioning.
54 Adetailedsurveyislikelytoinvolvetechniquesalreadymentionedfortheinitialappraisalandbasicsurvey.Thiswillbeinconjunctionwithmoredetailedmonitoringofyouremployees’potentialexposuretosubstanceshazardoustohealth.
55 Adetailedsurveyismostsuitedtocomplexprocessesandwillrequireanin-depthinvestigationoftheprocessanditsenvironment,forexample:
n proceduresinvolvedintheprocess;n workpractices;n maintenanceproceduresincludingthetypeandfrequency;n controlmeasuresinuseandtheirsuitability;n protectiveequipmentprovidedtoyouremployeesanditssuitability;n previousmonitoringresults;n resultsofhealthsurveillanceprogrammes;n informationandinstructionprovidedtoyouremployeesforcarryingoutthe
tasksinvolved;andn theextentofthetrainingprovidedtoyouremployees.
56 Adetailedsurveyusuallyrequiresmorespecialistknowledgethananinitialappraisalorbasicsurvey.Itisbeyondthescopeofthisguidancetodescribesuchaprocedureinfull,especiallyasdetailedsurveysvarywiththesituationineachworkplace.
57 Forfurtherinformation,seeReferences.AdditionalinformationcanalsobefoundinotherHSEpublicationsorpublicationsfromyourtradeassociation.Inaddition,youcouldconsultahealthandsafetyprofessional.TheBritishInstituteofOccupationalHygienistsholdsaDirectoryofConsultancies.
58 Forcertainsubstancesadetailedsurveymayneedtoincludetheuseofbiologicalmonitoring.YoucanfindoutmoreaboutbiologicalmonitoringandhowyougoaboutitinBiological monitoring in the workplace: A guide to its practical application to chemical exposure.4
Reappraisal
59 Monitoringforthebasicanddetailedsurveysmayhighlightdeficienciesincontrolmeasuresandpoorworkpractices.
60 Onceyouhavecarriedoutremedialactionyouwillneedtoseeifthechangeshavehadapositiveeffect.Youcanusuallydothisbyabriefreappraisalofthesituation.
61 Iftheriskstohealtharejudgedtobehigh,additionalexposuremonitoringmaybeadvisable.Forexample,when:
n carcinogensareused;orn thereisaveryvariablepatternofexposure.
Routine monitoring
62 Whenyoudecidethattherisktoyouremployeeshasbeenadequatelycontrolled,youmaydecidethatyouneedtosetuparoutinemonitoring
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programmetoensurethatthecontrolmeasuresstayeffective.
63 Inparticular,Schedule5oftheCOSHHRegulationsrequirescontinuousmonitoringforvinylchloridemonomerandevery14daysforspraysgivenofffromvesselsduringelectroplatingprocessesinvolvinghexavalentchromium.
64 Routinemonitoringcanbetime-consumingandexpensiveoverthelongterm.Consequently,ifyouthinkthatyoumaynotbecomplyingwithaWELitcanbemorecost-effectiveforyoutoinvestinbettercontrolmeasures.Thisreducesthe:
n needforexpensiveroutinemonitoring;andn healthrisksforyourworkforce.
65 Remember,therearesomesimpleandinexpensiveinstrumentsavailablewhichcanprovideinformationonthecontinuedperformanceofyourcontrolmethods,forexample:
n pressuresensingdevicesfittedtoventilationsystems;n smoketubes;orn dustlamps.
66 Fortheresultsofaroutinemonitoringprogrammetobeeffectiveinprotectingthehealthofyouremployeesyouneedtobeabletocomparethemwiththoseobtainedfrompreviousmonitoringexercises.Thisrequiresthattheprogrammeiswellplanned.Youneedtoconsider:
n thesimilarityoftheprocessesandtasksmonitored;n whereandatwhatstageoftheprocessthemonitoringwascarriedout;andn themethodofcollectingandanalysingthesamples.
67 Ifaprogrammeisnotwellplanneditcanproducealargevolumeofresultsandpaperworkwithoutbeingofanyactualuseinmakingsurethatyouremployees’healthisbeingprotected.
68 Thefrequencyofroutinesurveyswillvary.ThenearerthemeasuredexposureistotheWELthemorefrequentlyyouwillneedtomonitor.
69 OneschemefordeterminingthefrequencyofroutinemonitoringisgiveninBSEN689Workplace atmospheres: guidance for the assessment of exposure by inhalation to chemical agents for comparison with limit values and measurement strategy.11
Interpretation of results
70 WELsaresetdownaseight-hourtime-weightedaverages(TWAs)and/or15-minuteTWAs.ThismeansthatyouneedtoensurethateachresulthasbeenconvertedtothespecifiedTWAreferenceperiod.
71 TheapprovedmethodologyforcalculatingTWAsisgiveninEH40.7WhenyouareconvertingtheresultstoTWAs,youneedtogivecarefulconsiderationtotheaccuracyandprecisionofthesamplingandanalyticalmethods.Youcandothisbyconsultingthemanufactureroftheequipmentorbyseekingspecialistadvice,forexamplefromthelaboratorythatcarriedouttheanalysis.
72 WhencomparingtheresultswithWELs,limitsfromotherbodiesorin-housestandards,youwillneedtotakeaccountofotherrelevantworkplaceinformationyouhavecollected(seeAppendix3).
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73 Ifyouhaveusedrelativelyunsophisticatedtechniques,suchaschemicalindicatortubesduringaninitialappraisal,donotplacetoomuchconfidenceinthelevelofcompliancewhenanemployee’sexposureiswithinplusorminus50%oftheWEL.
74 Inthesecircumstancesyoushouldconcludethatthelevelofexposureisuncertainandamoredetailedinvestigationisrequired.
75 Whentheexposureisoutsidethisrangeyoucanbeconfidentthatnofurtheractionisnecessary.Asthestrategiesandtechniquesthatyouusebecomemorerefined,youcanplacegreaterconfidenceintheresults.
76 Inmostsituationsyouwillnotneedtocarryoutastatisticaltreatmentoftheresults.However,youmaydecidetoapplyasimpleanalysissuchasagroupaverageandrange.
77 Ifyouhavetakenalargenumberofsamples,forexampleduringrepresentative(seeAppendix2)androutinemonitoring,amoredetailedstatisticalanalysismaybecarriedout.Thiswillrequireaknowledgeofstatistics.
78 UsingstatisticstoanalysetheresultswillgiveyouabetterindicationofthevariabilityinexposureandextentofcompliancewithWELs.FurtherinformationonstatisticsisgiveninReferencesattheendofthisguidance.
79 Fromtheexposuremonitoringresultsyoumayconcludethat:
n thedataare/arenotadequateand/orrepresentativeofallthoseexposed;n compliancewithWELs,limitsfromotherbodiesorin-housestandardshas/has
notbeenachieved;n furtheractionsare/arenotnecessarytopreventorreduceexposure;orn moremonitoringis/isnotneeded.
Compliance testing
80 CompliancetestingmeanscomparingyourmonitoringresultswithWELs,limitsfromotherbodiesorin-housestandardstoensurethatyourcontrolstrategywillenableyoutocomplywithCOSHHregulation7.
81 WheninterpretingtheresultsandreachingyourconclusionyouneedtorememberthattheCOSHHRegulationsrequirethatprotectionisgiventoallemployees.Ifyouhavecarriedoutgroup-based,similarlyexposedgroup(SEG)monitoringyouneedtoshowthattheconclusiondrawnforoneemployeeisequallyapplicabletoothersinthesameexposedgroup(seeAppendix2,Paragraph5).
82 Anumberofschemeshavebeenproposedforcompliancetesting.BSEN68911describessomeoftheseschemes.
83 Reducingexposure‘sofarasreasonablypracticable’meansthat:
‘youmustreduceexposuretothepointwherethereisabigdifferencebetween,ontheonehand,thesacrifice(inmoney,timeortrouble)thatwouldbeinvolvedinfurthermeasuresand,ontheotherhand,therisksfromexposure(whichshouldbeinsignificant)’.
84 Ifyouarecomparingyourresultswithlimitsfromotherbodiesorin-housestandardsyouneedtoconsiderthebasisbehindthenumberinordertodecidewhetherthereisarisktothehealthofyouremployees.
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Appendix 1: Factors influencing airborne contaminant concentrations 1 Itisimportanttounderstandthevariabilityoftheworkplaceenvironmentbeforedesigningamonitoringstrategy.Factorswhichinfluencethereleaseandairborneconcentrationofsubstancesinclude:
n physicalandchemicalpropertiesofthesubstancesuchasthevapourpressure,boilingpointandparticlesize;
n thenumberofsourcesfromwhichthesubstanceisreleased;n rate,durationandspeedofreleasefromeachsource;n arrangementoftheprocess,temperatureanddesignofthecontrolmeasures;n variationsintheprocess,jobandtasksbeingcarriedout.Thesecanbebythe
hour,dayorevenweek;n dispersionormixingofthesubstanceintheworkplaceairduetogeneralor
localventilation;andn ambientconditions(temperature,pressureandhumidity).
2 Thesefactorsmayproducerapidfluctuationsintheconcentrationsofthesubstanceoververysmalldistances.Figure3showsaworkplacewhereplantandprocessconditions,andlocalandgeneralventilationcharacteristicsmayvaryfromdaytodayordisplayaseasonalpattern.
Figure 3:Factorsinfluencingairbornecontaminantconcentrations
3 Aswellasthefactorsoutlinedinparagraph1,youremployeescanalsoinfluencethelevelandpatternofexposure,forexample:
n thetypeandpositionofeachsourcerelativetotheemployee;n thelengthoftimetheemployeespendsinthevicinityofthesource;n whethertheemployeehas:
- directcontroloverthetaskorprocess;and- apoorappreciationoftherisksinvolvedleadingtopoorworkpractices.
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Appendix 2: Variables influencing the design of monitoring strategies 1 Thisappendixoutlinesanumberofvariableswhichyouwillneedtoconsiderwhendesigningamonitoringstrategy.FurtherinformationcanbefoundinReferences.
Health effect
2 Thetypeofhealtheffectthatcouldbeinducedbythesubstancewillinfluencethemonitoringprocedure.Forasubstancewithacuteeffectssuchaseyeirritation,themonitoringtechniquesneedtobesensitiveenoughsothatpeakandshort-term(15-minuteTWA)measurementscanbetaken.
3 Inthecaseofchroniceffectsthemonitoringstrategywillmainlyfocusonlong-term(eight-hourTWA)exposures.Thisisbecause,ingeneral,thedevelopmentofhealtheffectsdependsonexposureoveraprolongedperiodoftime.
4 Youmayneedtoconsidersubstanceswhichhavethepotentialtoinducebothacuteandchroniceffects.Themonitoringstrategywillneedtotakethisintoaccount.
Grouping of individuals
5 TheCOSHHRegulationsrequirethatyouprotectthehealthofallyouremployees.Whileyoumaywishtohaveinformationontheexposurepatternofallyouremployees,inmanyworkplacesthenumbersinvolvedmaymakethemonitoringexerciseprohibitivelyexpensive.Somonitoringstrategiesusuallyfocusongroupsofemployeeswhodosimilarjobsinsimilarways.Thesegroupsaredescribedassimilarlyexposedgroups(SEGs).Thegroupingofpotentiallyexposedemployeescanbemadebycarefulobservationofsuchcommonfactorsas:
n similarityofthetasksperformed(notnecessarilythesamejob);n exposuretothesamerangeofairbornecontaminants;andn similarityofenvironment(process,exposuresourceandcontrolmeasures).
6 Ifyouhavecarriedoutgroupsampling,theresultsneedtobecarefullyanalysedtomakecertainthattheyareequallyvalidforallemployeesintheSEG.AwidedifferenceintheresultsfromdifferentindividualsindicatesconsiderablevariationwithintheSEG.
7 Inthesecircumstancesyouneedtofurthersub-dividethegrouporreassignemployeestoamoreappropriateSEG.RepeatedmeasurementsfromthesameemployeecanhelpyoudecidewhetherthatemployeeneedstobereassignedoraSEGfurthersub-divided.
8 Asausefulguide:when an individual’s exposure is less than half or greater than twice the group average, then the individual needs to be reassigned to a more appropriate SEG.
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9 Youcanthenfocusyourriskcontrolstrategiesandfurthermonitoringonthoseemployeesmostatriskfromexcessiveexposure.
Types of exposure measurement
10 Asindicatedinparagraphs22to27inthemaintext,therearetwomaintypesofmonitoring,personalandfixedplace(static).Thepurposeofpersonalmonitoringistoestablishtheconcentrationoftheairbornesubstancewithinthebreathingzoneoftheemployee.
11 Thebreathingzoneisthespacewithin20-30cmoftheperson’snoseandmouth.Thisconventionpermitstheplacingofpersonalsamplersontheemployee’slapel.However,airflowsandactivitiesarevariable.Thismeansthatthepositioningofthesampler(rightlapel,leftlapelorhelmet)maycauseanoverorunderestimateoftheaverageconcentrationinhaledbytheemployee.Forexample,thefumegeneratedduringsolderingoperationswillrisestraightupwardsbecauseofthermalcurrents.Thismaymissasamplerplacedontheemployee’slapel.
12 Therefore,youneedtogivecarefulconsiderationtotheprocess,taskandworkpracticesbeforeplacingthesamplerandduringthemonitoringexercisesothattheresultscanbecorrectlyinterpreted.
13 Therearetwodistincttypesofpersonalmeasurement;representativeandworst-case:
n representative measurements takeintoaccountallpossibleworkplaceinfluencesincludingthevariablesdescribedinAppendices1and2.
n worst-case measurementscanbetakenwhereyoucanclearlyidentifyemployeeswhoaresubjecttoperiodsofhighexposure.Themonitoringperiodcanthenbeselectedtocovertheseevents.Forthepurposesofdeterminingtheeight-hourTWAexposure,youcanconsidertheexposuresfoundinthesecircumstancesasapplyingtothewholeoftheworkingperiod.Thispresumptionwillerronthesideofsafetyonceactedon.
Number of samples
14 Takingoneorafewsamplesononedaywillnotprovideyouwithsufficientinformationonwhichtobaseconclusionsaboutlong-termexposures.Inrealitythenumberofsamplesthatyoucantakeisusuallyconstrainedbytheresourcesavailabletoyou.Youneedtouseyourjudgementwhendecidingonsamplesize,especiallywhensmallgroupsareconcerned.
15 Forworst-casemonitoring,asaruleofthumb,atleastoneemployeeinfiveneedstobemonitoredfromaproperlyselectedSEG,unlessasmallernumbercanbejustified.
16 Forrepresentativemeasurements:
n iftherearelessthantenemployeesintheSEGonlyfiveneedtobeincludedinthemonitoringexercise;
n forcomplexsituationsinvolvingmorethantenemployeesintheSEG,seeReferences.
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Monitoring period and duration
17 Iftheprocessiscontinuousandhasminimalvariation,thechoiceofmonitoringperiodisnotofgreatimportance.However,iftheprocessiscyclicitiscriticalthatyoucarryoutthemonitoringatthetimeyouremployeesarebeingexposed.
18 Thechoiceofthemonitoringperiodisalsocloselylinkedtothetypeofhealtheffectassociatedwiththesubstance(seeAppendix2,paragraph2).Thedurationofthemonitoringhastobesufficientto:
n giveresultswhicharerepresentativeofthewholerangeofexposures,includingpeakexposures;and
n allowtherelevantTWAexposuretobecalculated.
19 Youalsoneedtoensurethatstart-upproceduresatthebeginningofshiftsandend-of-shifttaskssuchascleandownoperationsareincluded.
20 Inthecaseofcontinuous,well-controlledprocesseswithminimalvariabilityyoucanuseamonitoringdurationoflessthanthefullshift(oreight-hourreferenceperiod).Insuchcircumstancesthemonitoringperiodmaycoveratleast25%oftheworkingshiftandincludeperiodsofhighexposure.
21 Ifthereisconsiderablevariationintheworkpatternyoumayneedtomonitoronanumberofdaystocoverallanticipatedvariations.
22 Remember,unsampledtimerepresentsaseriousweaknessinthecredibilityofanyexposuremeasurement.Consequently,duringthistime,youneedtomakecarefulobservationofworkpractices,etc.
Sampling and analysis equipment
23 Themonitoringequipmentandmethodofanalysisthatyouchoosehastofittherequirementsofthestrategyandnotviceversa.However,thepracticalitiesoftheworkplacemayrequireyoutomakeacompromise.
24 Thesamplingtechniqueyouchooseneedstobeappropriateforthegivenworksituationandnotsignificantlyinfluencetheemployee’sbehaviourbybeing:
n tooheavy;n obstructive;orn noisy.
25 Theequipmentneedsto:
n berobustenoughtocopewiththedemandsoftheworkenvironment;n havesufficientbatterylife;andn becertifiedforuseinflammableatmospheres,ifnecessary.
26 Theerrorsinthesamplingandanalysisequipmentneedtobedeterminedandsupportedwhenappropriatebyqualitycontrolprotocols.
27 Examplesofnationalqualityschemesincludethe:
n NationalMeasurementAccreditationScheme(NAMAS);n WorkplaceAnalysisSchemeforProficiency(WASP).
28 Specificinformationonsamplingandanalyticaltechniquesformany
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substancesandprocessescanbefoundinHSE’sMethods for the determination of hazardous substances (MDHS)series.Youcanalsogetinformationfromequipmentmanufacturersandanalyticallaboratories.
Appendix 3: Core information 1 Asetofmonitoringresultsinisolationisrarelysufficienttopermitconclusionstobemadewithconfidenceonthelevelofexposureandthenecessarycontrolmeasures.Otheressentialinformationisoftenreferredtoas‘coreinformation’.12Collectingcoreinformationatthetimeyoucarryoutthemonitoringwillallowyoutomakereliabledecisionsabout:
n thelevelofexposure;andn theneedoradequacyofcontrols.
2 Table1liststheinformationwhichyoumayneedtocollectwhencarryingoutexposuremonitoring.
Table 1:Coreinformation
Key categories Data element
Premises Thissectionincludesdetailsonthenameofyourpremises,addressandwhattypeofworkyoudo.
Workplace Thissectiongivesinformationonthedepartment,workareaandprocess.
Workeractivity Detailsoftheemployee,egname,IDnumber,male/female,profession,jobtitleandtaskscarriedoutareincludedinthissection.
Product Thisisthenameoftheproductyouremployeesareusing.
Chemicalagent Thisisthesubstancewhichyouaremonitoringfor.Chemicalidentificationnumberscanbenotedifyouknowthem(CASorEINECSnumber).ThecurrentWELorotherstandardcanbenoted.
Exposuremodifiers
Theseareimportantfactorswhichwillhelpyouinterpretthemonitoringresults.Youcannotethethingswhichaffectyouremployees’exposure,forexample:
n isexposurecontinuousthroughoutthedayordoesitoccurin occasionalperiods;n whattypeofcontrolsdoyouuse: - local/generalventilation; - maximisingthedistanceoftheemployeefromtheprocess; - minimisethetimespentattheprocess; - theuseofrespirators;n istheareawheretheemployeeworks: - indoorsoroutdoors; - anopenorenclosedspace.
Measurementstrategy
Notethestrategythatyouusedinthesurveyinthissection,egwasitaworst-caseorrepresentativesituation.
Measuringprocedure
Describetheprocedureyouusedtocarryoutthemonitoring,procedure,egtypeofsample,durationofexposureandmonitoring.
Result Detailthesampleresult,theTWAresultandunits.
References Notethereportreferencenumberandthenameofthepersonwhocarriedoutthesurveyanddate.
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References1 Control of Substances Hazardous to Health Regulations 2002SI2002/2677TheStationeryOffice2002ISBN0110429192(asamended)
2 Approved supply list. Information approved for the classification and labelling of substances and preparations dangerous for supply. Chemicals (Hazard Information and Packaging for Supply) Regulations 2002. Approved list L129(Seventhedition)HSEBooks2002ISBN0717623688
3 Chemicals (Hazard Information and Packaging for Supply) Regulations 2002SI2002/1689TheStationeryOffice2002ISBN0110424190
4 Biological monitoring in the workplace: A guide to its practical application to chemical exposureHSG167HSEBooks1997ISBN0717612791
5 Management of health and safety at work. Management of Health and Safety at Work Regulations 1999. Approved Code of Practice and guidanceL21(Secondedition)HSEBooks2000ISBN0717624889
6 Control of substances hazardous to health (Fifth edition). The Control of Substances Hazardous to Health Regulations 2002 (as amended). Approved Code of Practice and guidanceL5(Fifthedition)HSEBooks2005ISBN0717629813
7 EH40/2005 Workplace exposure limits: Containing the list of workplace exposure limits for use with the Control of Substances Hazardous to Health Regulations 2002 (as amended) EnvironmentalHygieneGuidanceNoteEH40HSEBooks2005ISBN0717629775
8 Guide to occupational exposure values 2005AmericanConferenceofGovernmentalIndustrialHygienists2005ISBN1882417593
9 BSEN482:1994Workplace atmospheres - general requirements for the performance of procedures for the measurement of chemical agentsBritishStandardsInstitution
10 The dust lamp: A simple tool for observing the presence of airborne particles MDHS82HSEBooks1997ISBN0717613623(availablefreeonlineat:http://www.hse.gov.uk/pubns/mdhs/pdfs/mdhs82.pdf)
11 BSEN689:1996Workplace atmospheres - guidance for the assessment of exposure by inhalation to chemical agents for comparison with limit values and measurement strategy BritishStandardsInstitution
12 Occupational exposure databases: a proposal for core information for workplace exposure measurements on chemical agents EuropeanFoundationfortheImprovementofLivingandWorkingConditions1996ISBN9282773558
Further reading
Sampling strategies for airborne contaminants in the workplaceBritishOccupationalHygieneSociety(BOHS)TechnicalGuideNo11HandHScientificConsultants1993ISBN0948237147
HarringtonJMandGardinerKOccupational hygiene BlackwellScience1995ISBN0632037342
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HawkinsN,NorwoodSetalA strategy for occupational exposure assessment AmericanIndustrialHygieneAssociation1991ISBN0932627463
RoachSA most rational basis for air sampling programmesAnn.Occ.Hyg.197720 1-12
DewellPSome applications of statistics in occupational hygieneBritishOccupationalHygieneSociety(BOHS)TechnicalHandbookNo1HandHScientificConsultants1989ISBN0905927184
WhylieDSetting exposure limits: what to do when there’s no standard OccupationalHealthandSafetyCanada19939(6)58-60
Useful address
BritishInstituteofOccupationalHygienists/BritishOccupationalHygieneSociety5/6MelbourneBusinessCourtMilleniumWayPrideParkDerbyDE248LZTel:01332298101Fax:01332298099E-mail:[email protected]:www.bohs.org
Further informationForinformationabouthealthandsafetyringHSE’sInfolineTel:08453450055Fax:08454089566Textphone:08454089577e-mail:[email protected],CaerphillyBusinessPark,CaerphillyCF833GG.
HSEpricedandfreepublicationscanbeviewedonlineororderedfromwww.hse.gov.ukorcontactHSEBooks,POBox1999,Sudbury,SuffolkCO102WATel:01787881165Fax:01787313995.HSEpricedpublicationsarealsoavailablefrombookshops.
BritishStandardscanbeobtainedinPDForhardcopyformatsfromtheBSIonlineshop:www.bsigroup.com/ShoporbycontactingBSICustomerServicesforhardcopiesonlyTel:02089969001e-mail:[email protected].
TheStationeryOfficepublicationsareavailablefromTheStationeryOffice,POBox29,NorwichNR31GNTel:08706005522Fax:08706005533e-mail:[email protected]:www.tso.co.uk(Theyarealsoavailablefrombookshops.)StatutoryInstrumentscanbeviewedfreeofchargeatwww.opsi.gov.uk.
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