Monitoring strategies for toxic substances...use it as an introduction to the design of inhalation...

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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:licensing@opsi.gov.uk

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:admin@bohs.orgWebsite:www.bohs.org

Further informationForinformationabouthealthandsafetyringHSE’sInfolineTel:08453450055Fax:08454089566Textphone:08454089577e-mail:hse.infoline@natbrit.comorwritetoHSEInformationServices,CaerphillyBusinessPark,CaerphillyCF833GG.

HSEpricedandfreepublicationscanbeviewedonlineororderedfromwww.hse.gov.ukorcontactHSEBooks,POBox1999,Sudbury,SuffolkCO102WATel:01787881165Fax:01787313995.HSEpricedpublicationsarealsoavailablefrombookshops.

BritishStandardscanbeobtainedinPDForhardcopyformatsfromtheBSIonlineshop:www.bsigroup.com/ShoporbycontactingBSICustomerServicesforhardcopiesonlyTel:02089969001e-mail:cservices@bsigroup.com.

TheStationeryOfficepublicationsareavailablefromTheStationeryOffice,POBox29,NorwichNR31GNTel:08706005522Fax:08706005533e-mail:customer.services@tso.co.ukWebsite:www.tso.co.uk(Theyarealsoavailablefrombookshops.)StatutoryInstrumentscanbeviewedfreeofchargeatwww.opsi.gov.uk.

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