Control Banding Methode Comparasion With Measurement

J Occup Health 2007; 49: 482–492Journal of

Occupational Health

Received Jun 28, 2007; Accepted Aug 13, 2007Correspondence to: H. Hashimoto, Medicine and OccupationalHealth, ExxonMobil Yugen Kaisha, 1–8–15 Kohnan, Minato-Ku,Tokyo 108-8005, Japan(e-mail: [email protected])

Evaluation of the Control Banding Method—Comparison withMeasurement-based Comprehensive Risk Assessment

Haruo HASHIMOTO1, Toshiaki GOTO1, Nobutoyo NAKACHI1, Hidetaka SUZUKI1,Toru TAKEBAYASHI2, Shigeyuki KAJIKI3 and Koji MORI3

1Medicine and Occupational Health, ExxonMobil Yugen Kaisha, 2Department of Preventive Medicine and PublicHealth, School of Medicine, Keio University and 3Occupational Health Training Center, University of Occupationaland Environmental Health, Japan

Abstract: Evaluation of the Control BandingMethod—Comparison with Measurement-basedComprehensive Risk Assessment: HaruoHASHIMOTO, et al. Medicine and Occupational Health,ExxonMobil Yugen Kaisha—The control bandingmethod, or “control banding”, is a simplified riskassessment system for chemical handling tasks. Thissystem is supposed to provide assessment results ofreasonable quality without expert involvement. Theobject ive of th is study was to evaluate theappropriateness of control banding judgment on thebasis of workplace safety. A common approach forassess ing workp lace r i sk , wh ich is ca l led“comprehensive risk assessment” in this study, is tomeasure workers’ exposure and compare it withrelevant occupational exposure l imits. Riskassessment was performed with control banding(COSHH Essentials, UK) at 12 workplaces of apetroleum company in Japan, where health risks hadal ready been assessed separate ly throughcomprehensive risk assessment by experts and controltechnologies implemented accordingly. The obtainedcontrol banding judgments were then examined withregard to their adequacy by comparing them withexisting control technologies. There was majority ofcases (seven) where judgments by control bandingwere identified as “over-controlled”; there was nojudgments identified as “under-controlled”. Controlbanding also requested the seeking of expert advicein the majority of cases (eight). Thus, it wasdemonstrated that control banding tends to providesafe-sided judgment. A possible interpretation of thisis that control banding is inherently designed to secure

workplace safety by compensating for its insufficientexposure information with safe-sided judgment criteriaand by requiring experts’ intervention in high-risk cases.Control banding could be widely and effectively utilizedin Japan, especially by employers in small enterprises,provided that the above characteristics are pre-acknowledged and health experts are made available.To this aim, it is essential to develop new local healthexperts and establish institutional mechanisms forfacilitating employers’ access to expert advice. It shouldhowever be noted that the number of workplacesevaluated in this study was small.(J Occup Health 2007; 49: 482–492)

Key words: Control banding, COSHH Essentials, Riskassessment, Exposure, Chemicals, Hazard, Control,Small enterprises, Expert

It has been reported that the number of chemicalscurrently used in Japan is more than fifty thousand. Thismakes the appropriate control of the health risks of thesechemicals a current occupational health issue1). Whileoccupational health control of chemicals in Japan has beenperformed according to the Industrial Safety and HealthLaw, which defines specific requirements for workplaces,employers are supposed to autonomously perform riskassessment and management of chemicals that are notspecified in regulatory clauses, since the number ofchemicals regulated by the law is limited. With thisbackground, the Ministry of Health, Labour and Welfare,Japan, promulgated the “Guideline for risk assessmentof chemicals and other hazards” in March 2006, whichrecommends employers to perform risk assessments forall chemicals used by them and to take risk mitigationmeasures as needed2).

In order to perform an accurate risk assessment of aworkplace, collection of detailed hazard information andmeasurements of workers’exposure are commonly

483Haruo HASHIMOTO, et al.: Evaluation of the Control Banding Method

required, and a health expert who has sufficientknowledge of chemicals management is usually neededto perform them. However, there are often cases wherean expert is not readily available, especially among smalland medium enterprises. Thus, a simple risk assessmentmethod is required which does not require expertinvolvement.

The control banding method, or “control banding”, isa risk assessment system for chemical handling taskswhich was originally developed by the HSE (Health andSafety Executive, UK) and is now being globallypromoted by the ILO (International Labour Organization).Control banding recommends necessary controltechnologies based on only three characteristics of achemical handled: these are “hazard of the chemical”,“scale of use”, and “ability to become airborne”3). Sincecontrol banding is designed to follow a standardizedprocess without direct exposure monitoring, this methodis supposed to provide assessment results with reasonablequality under circumstances in which an expert is notavailable. Several published studies have investigatedthe appropriateness of risk assessment judgments ofcontrol banding. These studies have attempted to validatethe two exposure models on which the risk decisionscheme of control banding is grounded3–5). It was partiallydemonstrated that control banding tends to provideappropriate or safe-sided (over-controlled) judgment ingeneral. However, the results of these studies areinsufficient to draw an overall conclusion regarding theappropriateness of control banding for workplace safety,because the actual exposures of workplaces controlled inaccordance with control banding judgment were notdirectly compared with the relevant occupationalexposure limits.

Occupational exposure limits have been commonjudgment criteria for workplace safety. In order toaccomplish accurate risk assessment of chemical handlingtasks, it is usually considered as a standard approach toevaluate the exposure level and to compare it withoccupational exposure limit of the chemical; this approachwill hereafter be called “comprehensive risk assessment”in this study. In this study, risk assessment was performedwith control banding at workplaces where health risk hadalready been assessed separately by experienced expertsthrough comprehensive exposure assessment and controltechnologies had been implemented, as needed,accordingly. Then, the appropriateness of control bandingwas examined by comparing the obtained control bandingjudgment with the already existing controls.

Methods

Control bandingThe risk levels of 12 chemical handling tasks, which

are performed in refineries, a petrochemical plant, oilterminals and a research laboratory of a petroleum

company in Japan, were assessed with control banding(COSHH Essentials) available on the HSE website6). Thedetails of each task, its process, duration, the chemicalhandled and its amount, are shown in Table 1.Characteristics of each task relevant to control bandingassessment, such as the chemical species assessed, itsRisk-phrases (R-phrases) and hazard group, scale of use,and ability to become airborne, are shown in Table 2. R-phrases corresponding to a chemical were identifiedthrough the chemicals database carried on the homepageof the European Chemicals Bureau7). When the handledchemical was a mixture of multiple chemical species, R-phrases assigned to that mixture (example: gasoline) wereused for assessment, and R-phrases assigned tocomponents of the mixture (example: benzene) were notused. This is because it was assumed that it would notnecessarily be easy for small and medium enterprises,the chief target employers of control banding, to obtainspecific information regarding components of a chemicalmixture. However, the chemical species assessed for task# 4 was selected as benzene, and not petroleum products,since it was well known by workers that the petroleumproducts handled in this task contained appreciableamounts of benzene (1 to 5%). For respective tasks, theset of above information was input into control bandingonline interface, and then one of the four risk levels—the “control approach criteria” which range from level 1(lowest risk) to level 4 (highest risk)—was judged andpresented (Table 2).

Comprehensive risk assessmentThe following risk assessments and managements were

performed by workplace health experts (a CertifiedIndustrial Hygienist of U.S.A. or equivalent) with morethan several years of experience. A series of assessmentsteps was used for this risk assessment. First, personalexposure monitoring was performed regarding the mosthazardous or most representative component of thechemical handled. The monitored chemical species werebenzene, lubricating oil (monitored as total hydrocarbons)and n-heptane (Table 1). The exposure monitoring wascarried out with passive samplers (Traceair OVM-1 fromK&M Environmental Co.) which were then analyzed atthe ExxonMobil Biomedical Sciences Inc. (New Jersey,U.S.A.) which is an AIHA (American Industrial HygieneAssociation) accredited industrial hygiene laboratory8).

Second, a set of “exposure rating” was defined, in orderto classify the degree of exposure for workers. This isshown in Table 3: there are five levels of exposure ratingfrom A (highest exposure) to E (lowest exposure) whichare based on the relative relationship between themagnitude of exposure and the correspondingoccupational exposure limit of the chemical monitored.For a task with a duration of more than 15 min (i.e. withmonitoring time more than 15 min), the 8-h time-weighted

484 J Occup Health, Vol. 49, 2007

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average (TWA) exposure was calculated from theanalyzed airborne concentration; the average 8-h TWAwas then obtained by averaging the relevant sample data.Then, the exposure rating of this task was assigned basedon that average TWA. For a task with a duration of equalto or less than 15 min, the average 15-min TWA wascalculated similarly, and the exposure rating of the taskwas then assigned.

The exposure rating of tasks #4, 5, 9 and 10 wereassigned based on qualitative judgment: the expertscarefully observed the respective tasks and estimatedexposure levels with knowledge of past exposuremonitoring results for similar tasks within the worksite.This type of qualitative judgment has been acknowledgedas an effective screening method before quantitativemeasurements in the Occupational Exposure SamplingStrategy Manual by NIOSH9). Specifically, the exposurelevels were estimated to be relatively high for tasks #4, 5and 10, since the amount of chemical handled was

relatively large, more than 0.5 l. On the other hand, theexposure level was estimated to be low for task #9, sincethe amount of chemical handled was low, 0.05 l, andACGIH-TLV-STEL of acetone is exceptionally high, 750ppm. Consequently, the exposure rating of the 12 taskswas respectively assigned to one of the levels from A toE, as shown in Table 1.

Third, according to the scheme utilized by Booher etal.10), hazard levels of handled chemicals were classified,based on the EU labeling classification11), into fourlevels—from I (most hazardous) to IV (least hazardous)—hereafter called “health effect rating” (HER). Thelabeling classification of each chemical was assigned inaccordance with R-phrases of the chemical. Specifically,benzene was assigned to HER I since it is a “category 1carcinogen”; lubricating oil was assigned to HER II sinceit is a “category 2 carcinogen”; and n-heptane, tolueneand acetone were assigned to HER III since they are“irritant”(Table 1).

Finally, a matrix was constructed as shown in Table 4.This matrix defines three risk levels from 1 (highest) to 3(lowest) for a chemical handling task, based on acombination of the exposure rating and the health effectrating of the task. The risk levels of the 12 tasks wereindividually determined by adopting the exposure ratingand the health effect rating of each task in this matrix;the result is shown in Table 1. For tasks with a determinedrisk level of 1 (highest), a new exposure controltechnology, such as engineering or administrative control,was executed. The actual design or content of the controlwas determined by the experts. For tasks with risk levelsof 2 or 3, no exposure control technology was newlyimplemented.

Table 2. Risk assessment results by control banding

Task Chemical evaluated Scale of use Ability to Become Control Approach# Name R-phrase Assigned Hazard Group *1 *2 Airborne *3 Criterion *4

1 Gasoline 45, 65 E M M 42 Naphtha 45, 65 E L M 43 Crude Oil 45 E L M 44 Benzene 45, 46, 36/38, 48/23/24/25, 65 E M M 4, S5 Toluene 38, 48/20, 63, 65, 67 D S M 3, S6 Lubricating oils 45 E M L 47 n-Heptane 38, 50/53, 65, 67 A M M 1, S8 Gasoline 45, 65 E S M 49 Acetone 36, 66, 67 A S M 1, S

10 Toluene 38, 48/20, 63, 65, 67 D S M 3, S11 Gasoline 45, 65 E L M 412 Naphtha 45, 65 E M M 4

*1: A=Least hazardous, E=Most hazardous, *2: S=Small, M=Medium, L=Large, *3: L=Low, M=Medium, H=High, *4:Corresponding control recommendation: 1=General ventilation, 2=Local exhaust ventilation, 3=Enclosure, 4=Seek expert advice,S=Skin and eye precautions.

Table 3. Definition of “exposure rating”

Exposure rating Definition

A >RV*B 50–100 % of RVC 10–50 % of RVD 1–10% of RVE No exposure

*Reference value: ACGIH-TLV-TWA for tasks >15 min,or ACGIH-TLV-STEL for tasks ≤15 min.


The comprehensive risk assessment utilized here,which represents a series of risk assessment stepsdescribed above, is a way of quantifying magnitude ofrisk from a two-dimensional matrix. These twodimensions are the hazard and exposure levels of achemical, the latter being determined by the relativerelationship between the observed exposure and theoccupational exposure limit of the chemical. These twodimensions respectively represent “magnitude of ahazard” and “probability of occurrence of that hazard”which are key components of “risk” by definition.

Comparison of control banding and the comprehensiverisk assessment

Let us make an assumption that the comprehensiverisk assessment method utilized in this study is capableof assessing magnitude of risk with reasonable accuracyand that the control measures actually implemented werejust enough in regard to their scale and quality; the basisof this assumption is that this assessment method is basedon direct or indirect exposure measurements, and thatexperts are involved throughout the process. Theappropriateness of the control banding judgment wasexamined for 12 tasks, on the basis that risk judgment by

the comprehensive risk assessment is a standard. Theresults were classified into four criteria—“over-controlled”, “appropriate”, “under-controlled” and “notcomparable”, as shown in Table 5. Namely, the controlapproach criterion given by control banding wascompared with the judgment of the comprehensive riskassessment whether new control technology wasrequested or not (i.e. whether the judged risk level was“1” or “2 or 3”). In cases where the control approachcriterion was level 1, 2 or 3, and also control technologywas requested by the comprehensive risk assessment (i.e.judged risk level was 1), the actual control ececuted wascompared with the specific type of the controlrecommended by the control approach criterion.

Results

Risk assessment results by means of control bandingare shown in Table 2. The judged control approachcriteria of 12 tasks ranged from 1 to 4. Each controlapproach criterion, from 1 to 4, represents a specificcontrol recommendation. These are “general ventilation”,“local exhaust ventilation”, “enclosure”, and “seekingexpert advice”, respectively. Five tasks which involvedchemicals hazardous to the skin and eyes were

Table 4. Matrix for “Risk level*” assignment in comprehensive exposure assessment

HER** Exposure ratingA B C D E

I 1 1 2 2 3II 1 1 2 3 3III 1 2 2 3 3IV 2 2 3 3 3

*Risk level: 1=Highest risk, 3=Lowest risk, **Health effect rating: I=Most hazardous,IV=Least hazardous

Table 5. Comparison scheme of risk assessment results

Control banding: Comprehensive exp. “Appropriateness” of judgmentControl approach criteriona assessment: Risk levelb by control banding

1, 2, or 3 1 Over-controlled c

Appropriate c

Under-controlled c

1, 2, or 3 2 or 3 Over-controlled4 1 Not comparable4 2 or 3 Over-controlled

a1=General ventilation, 2=Local exhaust ventilation, 3=Enclosure, 4=Seek expert advice,b1=Control requested, 2=Control not requested, 3=Control not requested,cThe actual control executed through comprehensive exposure assessment was compared with the controlrecommended by the control approach criterion.


additionally classified “S” criterion. The control approachcriterion having the largest number of tasks (eight tasks)is criterion 4. This represents the highest risk level andrequests expert advice.

Risk assessment results by means of comprehensiverisk assessment are shown in Table 1. The exposure ratingand the health effect rating of the 12 tasks ranged from Ato E, and I to III respectively. The risk levels determinedfrom the combination of these two dimensions rangedfrom 1 to 3. Among them, there were five tasks with risklevel 1, to which engineering or administrative controlswere then executed: local exhaust ventilation (laboratoryenclosing hoods) was installed for tasks #4, 5 and 10,and respiratory protective equipment was provided fortasks #2 and 3.

In order to evaluate the effectiveness of the controlsexecuted, a repeat risk assessment was performed for thetasks after implementation of the controls; the results areshown in Table 6. For tasks #2 and 3, exposure levels atbreathing zones were estimated based on an assumptionthat a half-face or full-face air-purifying mask yields a 1/10 or 1/50 decrease in exposure, respectively, comparedwith the original exposures previously measured (shownin Table 1), since the assigned protection factors definedby NIOSH for half-face and full-face masks are 10 and50, respectively12). For tasks #4 and 5, exposuremonitoring was carried out. For task #10, the expertcarefully observed the task and qualitatively assessed theexposure level. Consequently, the risk levels of thesetasks went down to either level 2 or 3 after implementation

Table 7. Comparison of risk assessment results and appropriateness of control banding judgment

Task # Control banding: Comprehensive exp. assessment:Control approach Risk level Appropriateness of control

criterion Risk level Control done? banding judgment

1 4 2 N Over-Controlled2 4 1 Y Not Comparable3 4 1 Y Not Comparable4 4 1 Y Not Comparable5 3 1 Y, Ventilation hood Over-Controlled6 4 3 N Over-Controlled7 1 3 N* Appropriate8 4 2 N Over-Controlled9 1 2 N* Appropriate

10 3 1 Y, Ventilation hood Over-Controlled11 4 2 N Over-Controlled12 4 2 N Over-Controlled

*General exhaust ventilation was originally equipped.

Table 6. Repeat risk assessment by comprehensive exposure assessment after implementation of control technologies

# Monitoring TWA *1 RV *2 Exp. HER Risk Note

Chemical n Av. TWA Assumed (ppm) rating *3 level

(ppm) (ppm)*1 (ppm)

2 (Benzene) – – – <0.14 2.5 D I 2 Assumption based on APF (*4)

of a half face mask (10)

3 (Benzene) – – – <0.14 0.5 C I 2 Assumption based on APF (*4)

of a full face mask (50)

4 Benzene 9 0.07 0.07 – 0.5 C I 2

5 Toluene 2 6.10 6.10 – 50 C III 2

10 (Toluene) – – – – 50 D III 3 Judged by observation

*1: 8 h time weighted average exposure, *2: Reference value: ACGIH-TLV-STEL for task duration >15 min, ACGIH-TLV-TWA for task

duration >15 min, *3: Health effect rating, *4: Assigned protection factor (NIOSH, yielding 1/10 or 1/50 decrease in exposure for a half or

full face mask respectively.)


of controls: effectiveness of the controls was thus verified.The comparison of the results of the risk assessments

performed with control banding and those with thecomprehensive risk assessment are shown in Table 7. Fortasks #2, 3 and 4, while control banding assigned themto control approach criterion 4 (requesting expert advice),the comprehensive risk assessment determined their riskas level 1 and controls were executed, accordingly.Control banding judgment was classified as “notcomparable” for these tasks, since it was impossible toforecast the actual control advice to be provided by theexpert requested by control banding. For tasks #1, 6, 8,11 and 12, while control banding assigned them to controlapproach criterion 4 (requesting expert advice), thecomprehensive risk assessment determined their risks aslevels 2 or 3, and therefore did not request controls.Control banding judgment was classified as “over-controlled” for these tasks, since intervention of an expertwas deemed to be unnecessary. For tasks #5 and 10,control banding assigned them to control approachcriterion 3, and requested “enclosure” of workplaces.Local exhaust ventilation had actually been installed atthese workplaces according to the comprehensive riskassessment results, and it was later confirmed thatexposure risk had been successfully mitigated. Thus,control banding judgment was classified as “over-controlled” for these tasks, since “enclosure” was notnecessarily needed. For tasks #7 and 9, control bandingassigned them to control approach criterion 1, andrequested general ventilation. The comprehensive riskassessment had not requested control technologies.However, both workplaces were already equipped withgeneral ventilation systems for these tasks, and thecomprehensive risk assessment was performed withgeneral ventilation functioning; tasks #7 and 9 werecarried out in a research and testing laboratory room,respectively. Thus, control banding judgment wasclassified as “appropriate” for these tasks, since theexposure risk was appropriately controlled with generalventilation. In summary, judgments by control bandingwere “over-controlled” for the majority of tasks, seven;three tasks were “not comparable”, and two were“appropriate”; no task was “under-controlled”.

Discussion

Characteristics of control bandingThe following characteristics of control banding can

be pointed out based on the results obtained.(a) There is an enhanced tendency to provide safe-sided

judgment.(b)There is an enhanced tendency to recommend seeking

expert advice; these cases are represented by controlapproach criterion 4.The following characteristics were also identified.

(c) It is valuable in practice that the need for skin/eye

protection is explicitly recommended for skin/eyehazardous chemicals without omission.

(d)It should be cautioned that the risk assessment outcomecan be different depending on what species ofchemicals is selected as assessment objects for achemical mixture. For example, the risk assessmentof task #1 was performed for gasoline, a commonname of the mixture. If it were performed for toluene,a gasoline component with typical concentration ofseveral percent, a risk phrase of R-38 would beadditionally identified (in the same way as task #5 inTable 2) and control approach criteria “S” would besupplemented accordingly. Control banding requiresthat all components of a chemical mixture should beevaluated and the highest (most demanding) controlapproach criterion among all criteria presented shouldbe followed. However, such a comprehensiveapproach is often not realizable, a typical obstaclebeing that there are MSDS’s with insufficientcomponent information. There is also an issue of cut-off criterion of mixture components, the percentcomposition above which a chemical species is definedas a component. For example, the handling of achemical species with a concentration in the range of0.1% to 1.0% in a mixture may be controversial.While this issue can also be problematic forcomprehensive risk assessment, extra caution shouldbe taken in case of control banding assessments whenexperts are not involed.

(e) The risk of a task can not be re-assessed after theimplementation of control technology since facilityinformation is not incorporated into control bandingassessment steps. In contrast, re-assessment can bereadily performed by means of the comprehensive riskassessment.

(f) The COSHH on-line interface is very user-friendly.

Comparison of this study with preceding studiesControl banding judges control approach criteria based

on three factors: “hazard of a chemical”, “scale of use”,and “ability to become airborne”. It can be interpretedthat the judgment scheme of control banding has itsgrounds on two exposure models3). The first model is:“the exposure level is uniformly predicted, given ‘scaleof use’, ‘ability to become airborne’, and ‘controlapproach criterion’”. Here, the exposure level is calledan “exposure band”, and it represents a range of exposureand not a single value. The second model is: “the safeexposure limit of a chemical is defined in correspondenceto the respective hazard group (‘A’ to ‘D’) to which thechemical belongs, and is not directly related to eachchemical species”. This exposure limit represents a rangeof exposure and not a single value, and it actuallycoincides with the “exposure band”. When performingrisk assessment regarding a chemical handling task, one


first identifies the hazard group to which the chemicalbelongs. This then provides the target safe exposure limit(i.e. “exposure band”) of the chemical. With this“exposure band”, along with “scale of use” and “abilityto become airborne” of the chemical, one can determinethe “control approach criterion” through back-trackingthe logic of the first exposure model; this is the riskjudgment scheme of control banding. Chemicals inhazard group “E” do not have a corresponding exposureband, and they are always assigned to control approachcriterion 4.

Tischer et al. researched existing databases of 18different industry operations in Germany regarding theirwork conditions and monitored exposure levels3). Theyidentified the exposure band of each chemical handlingtask based on the first exposure model of control banding,and then compared the obtained exposure band with themeasured exposure. They found that actual exposurelevels were equivalent to or lower than correspondingexposure bands for most of the tasks, which suggestedthat the first exposure model was tuned to an appropriatelevel or a rather safe-sided level.

Jones et al. compared exposure bands to measuredexposures with regard to solvent vapor degreasing andpowder bag filling operations, utilizing monitoring dataaccumulated by the National Institute for OccupationalSafety and Health (NIOSH)4). Their study also representsa validation attempt for the first exposure model of controlbanding. They defined an “over-controlled” error as aninstance where conditions of chemical use promptedcontrol banding to recommend newly implementing acontrol technology, although the monitored airborneconcentration was within or below the chemical’sexposure band in the absence of any control technology.This error was observed for as much as 61% of relevantvapor degreasing operations. They also defined an“under-controlled” error in which the monitored airborneconcentration exceeded the upper limit of the chemical’sexposure band although there was a control technologyimplemen ted acco rd ing to con t ro l band ingrecommendation. This error was observed for as muchas 78% of the vapor degreasing operations, and for asmuch as 48% of the bag filling operations. Based onthese results, Jones et al. concluded that their analysisdid not support the view that control banding would beable to accurately identify appropriate controltechnologies and that the recommended controltechnologies were capable of adequately controllingexposures. This is a different conclusion from that ofTischer et al4). Caution should be noted for the “under-controlled” errors in Jones’ study, since the monitoredexposure levels had not been compared with theoccupational exposure limits of the chemicals concerned.Therefore, an “under-controlled” error does notnecessarily suggest a workplace condition deemed to be

unsafe for workers.Brooke compared the occupational exposure limits of

the UK with exposure bands for 111 chemicals. His studyrepresents a validation attempt for the second exposuremodel of control banding, and it identified only 2 casesout of 111 chemicals where the occupational exposurelimit was lower than the exposure band5). This meansthat the exposure bands have been designed to be moreconservative than the occupational exposure limits formost of chemicals. Thus, it was demonstrated that thejudgment scheme of control banding is tuned to providesafe-sided decisions.

The studies referred to above attempted to validate theappropriateness of the two exposure models of controlbanding. It was partially demonstrated that controlbanding tends to provide appropriate or safe-sided (over-controlled) judgment in general. However, these resultsare insufficient to draw overall conclusions regarding theappropriateness of control banding from the point of viewof workplace safety. This is because the actual workplaceexposures and occupational exposure limits werecompared only indirectly, and not directly, within thestudies. Here, let us suppose a chemical handling taskwhich is controlled under a control approach criterionprovided by control banding judgment. When we followthe general conclusion reached by Tischer and Brooke,we can assume that the exposure of this task is eitherequal to or lower than the exposure band, and that thisexposure band is lower than the occupational exposurelimit of the chemical. This results in a situation wherethe exposure is lower than the occupational exposurelimit, and hence, we can conclude that the workplace issurely safe and that control banding judgment is safe-sided. On the other hand, Jones et al. identified asignificant number of “under-controlled” cases whereworkplace exposures exceeded the relevant exposurebands. For these cases, even after taking account ofBrooke’s general conclusion, it is difficult to predictwhether or not workplace exposure is lower than theexposure band in general. Thus, it can be summarizedthat verifying the appropriateness of respective exposuremodels has limited effectiveness in evaluating controlbanding system.

The most appropriate approach would therefore be tocompare the measured exposure of a chemical, used in aworkplace where the risk assessment had been performedwith control banding and the control technology advisedby it implemented, with the occupational exposure limitof the chemical, in order to verify control banding systemon the basis of actual workplace safety. However, thereis a concern in terms of workers’ safety if we first assessa workplace with control banding, then implement controltechnology accordingly, and lastly monitor exposure ofthe workplace to examine its environment (i.e. aprospective study). In our study, risk assessment was


performed with control banding at workplaces where therisk had already been assessed by means of acomprehensive exposure assessment (that is, exposureswere monitored and compared with occupationalexposure limits) and control technologies had beenimplemented as needed according to experts’ professionaljudgment. Then, the appropriateness of control bandingwas evaluated by comparing the obtained control bandingjudgment with existing control technologies (i.e. aretrospective study).

The findings of this study demonstrate that controlbanding tends to make safe-sided judgments. Namely,control banding requested additional exposure protectionmeasures for workplaces where the actual exposures werelower than the relevant occupational exposure limits.Such cases were observed in more than half of the tasksevaluated. Thus, this study confirms that control bandingjudgment is safe-sided in reality on the basis of workplacesafety.

It was also observed in this study that there were anumber of cases where control banding requested expertconsultation (i.e. control approach criterion 4). This isbecause many tasks involved petroleum products suchas gasoline or naphtha which contain benzene(carcinogen, R45). In the Jones’ paper, “control approachcriterion 4” was assigned to 13 chemicals among 26chemical substances (liquid or powder) evaluated4); thefrequency of “control approach criterion 4” was notspecifically discussed in the other studies referred toearlier. In addition, all chemicals assigned to hazard groupE and some of the chemicals assigned to hazard groupsC and D are judged as “control approach criterion 4”within the decision scheme of control banding6). On thewhole, we can predict that there will be, in general,moderately frequent occurrence of control bandingjudgment requesting expert consultation.

Position and limitation of this studyIt must be noted that the scope of tasks evaluated in

this study was limited. The number of tasks was 12, andthe task processes were mainly liquid transfer andwashing within one petroleum company. More than halfof the chemicals handled in these tasks were benzene-containing petroleum materials, such as gasoline ornaphtha. In addition, most of the chemicals evaluatedare classified as “medium” for their “ability to becomeairborne”, and the number of exposure measurement datautilized was rather small—about 70.

Tischer et al. mention in their study that they wereable to validate the appropriateness of COSHH Essentialsscheme only partially, despite the fact that they evaluatedas many as 18 kinds of tasks within a wide variety ofindustries such as textile, printing, chemical and furnituremanufacturing, and that the number of exposure datautilized was substantial—about 9603). They attributed

the reason for the imperfection of their validation as beingdue to the fact that while all combinations of taskconditions amounted to a total of 54 exposure scenariosin control banding, their study covered only 8 scenariosand further tended to concentrate on “medium scale” and“medium volatility/dustiness” conditions. Jones’s studycontains a large database as well. The numbers ofworkplaces evaluated were 33 for vapor degreasing and22 for bag filling operations, and the numbers of chemicalspecies measured were 7 and 19, respectively, while thenumber of exposure measurements was about 710 4).

The above two studies suggest that substantially large-scale investigation will be necessary to evaluate controlbanding system with accuracy and objectiveness. Thus,since the scope of tasks and chemicals evaluated in ourstudy was limited, it is appropriate to acknowledge thiswork as a pilot study which compared control bandingwith actual workplace management performed by meansof comprehensive risk assessment, and it should becautioned that the generalizability of this study will belimited.

Utilization of control banding in JapanIt is desirable that health risk assessment of chemicals

be performed by experts having an appropriate level ofexpert knowledge, since health risk is not often readilyperceivable by workers and specialized knowledge suchas toxicology is usually required for health riskassessment and management. However, the availabilityof experts is significantly different in practice from oneenterprise to another. Therefore, an employer willimplement control technology complying with an expert’srisk assessment result, as long as an expert is availableand the quality of the collected hazard information isgood. In contrast, an employer will rather carry out safe-sided (over-controlled) control technology if an expert isunavailable or the quality of the hazard information ispoor, considering uncertainty factors within the riskassessment system employed13). An example of suchchoices between the two is the comprehensive riskassessment and control banding investigated in this study.These two methods can represent, in short, choices of a“tailored method with accuracy” or a “safe-sided methodcompensating for scarcity of information”. It can beinterpreted that control banding is inherently designed tocompensate for insufficient exposure information by asafe-sided judgment and to secure the safety of high-riskworkplaces by requesting expert intervention.

Control banding could be effectively utilized for riskassessment of chemicals in Japan, provided that its safe-sided characteristics are pre-acknowledged by users andthat channels for expert intervention are secured. Thissystem could also be utilized for screening purposesbefore performing more accurate risk assessments suchas the comprehensive risk assessment. In such cases, the


degree of safety of a workplace would be expected to bereasonably high if control banding had judged the presentstatus of the workplace as “safe”.

Money et al., as members of the COSHH Essentialsworking group of the HSE, reported that control bandingis designed as inherently conservative and that it needsto be operated in a “screening mode” which presupposesseeking access to experts as needed14). They admittedthat there have been criticisms regarding artifacts ofcontrol banding methodology and cases where controlbanding “advice” is overly protective for some tasks whencompared with recommendations derived from empiricaloccupational hygiene approaches. However, they stressedthat the most important consideration is the extent towhich reasonable risk control advice can be accessed andimplemented by users in practice. They also mentionedthat control banding has a far greater likelihood of meetingusers’ needs in a context where risk assessment expertscan not readily be accessed. Their opinion can beinterpreted as actively supporting the conclusion of thisstudy, that the control banding judgment is safe-sided,and that control banding has potential for future utilizationincluding screening use in Japan.

When control banding provides a truly safe-sided (over-controlling) judgment, the employer will bear a wastefulburden if they obediently implement control technologyaccording to the judgment. In reality, it is predictablethat there will be frequent cases where employers activelyseek expert advice after suspecting the accuracy of thejudgment in attempts to avoid potential waste ofresources. Also, there can be other cases where employersneglect seemingly over-controlling judgment at their owndiscretion because they are cautious about the excessivecost burden. Considering such situations, and alsoconsidering the fact that control banding often advisescontrol approach criteria 4, it can be concluded that thenecessity of providing health experts for control bandingis substantially high in reality, although the controlbanding system is often perceived as not requiring experts.The COSHH Essentials on-line interface actuallyrecommends users to consult certified occupationalhygienists when it assigns a case as control approachcriteria 4; on-line linkage to the British OccupationalHygiene Society is also provided6). The existence ofestablished occupational hygienists is thus one of the keyinfrastructures for smooth functioning of control bandingsystem. Therefore, in order to aim for encouragingutilization of control banding in Japan, it would beessential to establish institutional and social mechanismsfor facilitating employers’ access to expert advice withease and at low cost. It would also be indispensable todevelop new local health experts such as those availablein the U.S.A. or European countries.

Conclusion

The appropriateness of control banding system wasevaluated based on workplace safety by assessing risksof chemical handling tasks with control banding and thencomparing the results with a practical risk assessmentoutcome performed with the comprehensive riskassessment. It was demonstrated that control bandingtends to provide a safe-sided judgment. A possibleinterpretation of this is that control banding is inherentlydesigned to secure workplace safety by compensating forinsufficient exposure information with safe-sidedjudgment criteria and by requiring expert advice in high-risk cases. Control banding could be widely andeffectively utilized by employers in Japan, provided thatthe above characteristics are pre-acknowledged by users.To this aim, it will be essential to establish institutionalmechanisms which facilitate development and utilizationof new local health experts. However, it should be notedthat the scope of tasks and chemicals evaluated in thisstudy was limited.

Acknowledgments: This study was supported by theLabor Science Research Fund (the Program forComprehensive Occupational Safety and HealthResearch) under supervision of the Ministry of Health,Labour and Welfare, Japan: subject number of H16-roudou-6.

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Control Banding Methode Comparasion With Measurement

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