Document GKpGNg1J2j12bjNjO0MnRenRv

FILE NAME Painters and Allied Trades PAINT DATE 2006 July DOC PAINT106 DOCUMENT DESCRIPTION UK Government Report on Chrysotile in Textured Coatings Harpur Hill Buxton Derbyshire SK17 9JN T +44 1298 218000 F +44 1298 218590 W www.hsl.gov.uk . HEALTH & SAFETY LABORATORY Summary report on additional work carried out on the monitoring of chrysotile containing textured decorative coatings 2006 . Project Leader Garry Burdett Author Garry Burdett and Graham Revell Science Group Science Group 5 Ms. R. Russell Dr K.Walkin K.Walkin Mr. T. Johnson Dr. M.J. Gibson Mrs. S Peace Mr. D. Dean Mr. R. Cooper Dr. N. West Mr. B. Tylee HSL Library IF Section DISTRIBUTION HSE DR4 Customer Project Officer : HSE DR4 Customer Authorising Officer HSE BHAW7 HSE SSGOCC HSE FOD Nottingham HSE FOD Leeds HSE FOD Sheffield HSL Operations Director HSL IFS HSL HSL PRIVACY MARKING Available to the public HSL report approval Date of issue Job number - Registry file Electronic file name B.Tylee February 2006 JS20004675 024691 TDC 2 FINALREPORT 'Crown copyright 2006 ACKNOWLEDGEMENTS We would like to acknowledge the help of the asbestos licensing principle inspectors and their support staff and colleagues at HSE's area offices at Leeds Sheffield Nottingham and Manchester who made the site selection possible We are also indebted to the site owners main contractors and asbestos removal contractors at the sites visited and in particular the help we received from the asbestos removal operatives We would also like to thank the asbestos removal contractors association for their helpful comments and recognise the efforts made by Mr Richard Houlihan and Alison Clarke of the Inorganics and Fibres section and Mr Peter Baldwin of the FSSU of HSL for their part in the collection and analysis of the samples which made this report possible iii CONTENTS 1 1.1 1.2 INTRODUCTION ......... 1 Background ... ee ceeccsssseseescsececsecscscsusassssassceesaesassusatsuvacsesacsavsceesenees 1 Objectives of the work .......cccccccsscscssssescssssssstsssceseasessessssstacsesatsecsseseesens 3 2 2.1 2.2 SITE SELECTION AND STRATEGY 555 Site selection and arrangements ..... 555 Site selection and sampling Biases 0.00... seccescccccsccesscssecesssceceececeeceseees 555 3 3.1 3.2 3.3 3.4 SAMPLING AND ANALYSIS METHOD AND ISSUES ......... 6 Sampling method ........... 6 Analytical method ..... cccccsccccssscsscscessessecsssceacsesecscsassessssssavscereecueceesess 6 PCM Sampling and analysis .......... 7 Determination of the Asbestos concentration 9 ......0...ccccccccccsccsessssesececcecesee 4 RESULTS AND DISCUSSION .......ssssscssssssssssscssssccaseceatsecsrsnsecsueessauesenees 10 4.1 The airborne releases from the removal of TDC from a wider range of surfaces .... ecsssccsscsseecseseesesssssecsesesevscscssseveesevsevssausaussessausesaesssassuvssessecterseseses 10 4.2 change in the personal airborne asbestos fibre concentrations inside the enclosed area if no air extraction is used to keep a reduced pressure inside the enclosure eee ccs seseesseceseessSdececesecuucecsseeseuueceucceccecessueusaesesasesees .... 13 4.3 effectiveness of site clearance based on a visual assessment alone 14 4.4 4.5 used The likely airborne releases from poorly controlled removal 16 The airborne concentration outside the enclosure if no air extraction is 18 4.6 the the airborne building ..... exposures that will be experienced by persons reoccupying cee ccccsesssscseeesscsevecasseseesavassacseessesuessssssaseesanentectecesceccce 19 ASSESSMENT .. 5 IMPLICATIONS FOR RISK sesssanenenneneas 20 5.1 The airborne releases from the removal of TDCs 20 5.2 Theoretical Maximum Number of person exposed at the High estimate of the exposure concentration 0.0... cc cceccssscscseessecsesesesesesessssesssevsserseseveveceececeesce. 20 5.3 validity of the average exposure for risk assessment ..........000-0000000000-... 20 5.4 Measured concentrations from the additional sites 21 6 APPENDICESseetsuessssansseers 22 6.1 Proposed Project to monitor personal fibre concentrations of workers involved in the removal and renovation of textured decorative coatings PHASE 2 22 6.2 Response from ARCA .........cceccccecccsesssesscstsscsesceutsseeseseesseeececcescesecceccccee. 25 7 REFERENCES ........... 27 sessssssereessssssesacsrcasseserassererssveususersusecsesassessssecseeses iv EXECUTIVE SUMMARY Objectives The objectives of the research were to carry out further site monitoring to determine 1. Airborne fibre concentrations releases during the removal of textured decorative coatings TDCs from a wider range of surfaces to those reported in an earlier survey see IF2005 2. Change in the personal airborne asbestos fibre concentrations inside the enclosed area during the removal of TDCs if no air extraction is used to keep a reduced pressure inside the enclosure and 3. Effectiveness of the clearance following removal of TDCs based on a visual assessment alone In addition as the work progressed sampling was also carried out to address three additional questions raised by the Asbestos Removal Contractors Association ARCA 4. What are the likely airborne releases from poorly controlled removal of TDCs 5. What is the airborne concentration outside the enclosure during removal of TDCs if no air extraction is used 6. What are the airborne exposures that will be experienced by persons reoccupying a building following the removal of TDCs Method Notifications for licensed removal of TDCs from four Health and Safety Executive HSE regional offices were used to select sites where TDCs were being scraped or removed from resistant surfaces The asbestos removal contractors at the candidate sites were contacted by staff from the Health and Safety Laboratories HSL and the proposed sampling work discussed If agreement for sampling was given HSL then arranged for the appropriate waivers and contacted the main contractor and owners HSL sampling personnel in liaison with the contractors attend sites during the removal to sample the following personal . * personal fibre concentrations of operatives during peak removal and cleaning activities cleaning ' personal gravimetric dust exposure of operatives during peak removal and activities static fibre concentration in the airlock during removal and e static fibre concentration inside the enclosure during disturbance sampling of dust and debris The high airborne dust concentrations encountered meant that the collection filters would become overloaded and unusable for microscopy analysis if personal samples of 240 litres of air over a hour period were collected as required for compliance monitoring In most cases it V was only possible to sample for some 10 - 30 minutes at flow rates of the filters became too overloaded for microscopy analysis /l1itre per minute before The filters collected during the site sampling were analysed by HSL using UKAS accredited procedures for fibre counting and analysis Fibre count analysis was carried out on a portion of the filter using light microscopy at X500 magnification with phase contrast optics PCM to count the number of visible fibres particles that were > ...mlong < 3...mwide and had a length breadth ratio > Variable amounts of calcium sulphate fibres can be released from the TDC and from underlying plasterboard or plaster These fibres cannot be distinguished from asbestos fibres when samples are counted by using a light microscope The number of calcium sulphate fibres which are released may be many times greater than the number of asbestos fibres released To remove this interference part of the filters were water wicked to dissolve the calcium sulphate fibres Only PCM counts on wicked samples have been included in this summary of the site sampling data Similarly only results using the World Health Organisation WHO counting rules have been used in this summary report unless it is expressly stated otherwise Although the PCM concentration of soluble fibres will not give a direct measure of the asbestos fibres as other asbestos fibres will still remain it gives an initial upper estimate of what the asbestos fibre concentration could be A limited number of samples were also analysed by analytical transmission electron microscopy TEM which uses electron diffraction and energy dispersive ray analysis to identify individual fibres to determine whether they are asbestos or asbestos Fibres of a size which would have been visible and met the PCM counting criteria fibres 5 ...mlong > 0.23 0.23 0.23 ...m wide and with an aspect ratio > were analysed This allowed PCM equivalent PCME airborne asbestos fibre concentrations to be calculated as detailed in the International Standards Organisation method ISO 10312 for asbestos in ambient air Total and respirable dust concentrations were determined in accordance with MDHS14 by weighing filters from inhalable and cyclone personal samplers which were collected in addition to the asbestos samples As it was only possible to sample small volumes of air to avoid overloading the filters this meant that fewer fibres were counted which reduced the precision of the result and few individual samples exceeded the limit of quantification LOQ Results and Main Findings Airborne releases from the removal of TDCs from a wider range of surfaces Five sites containing TDCs were monitored four of which textured decorative plaster and one that contained an asbestos type present was chrysotile white asbestos The removal substrates included contained asbestos containing containing paint The asbestos methods and the underlying e Hand scraping TDC from concrete one site and hard finishing plaster two sites e Removing plaster and TDC from brickwork with a hammer and chisel one site vi * Removing a chrysotile containing paint on pebbledash from brickwork with a Kango powered chisel Demolition and removal of TDC and the under laying plasterboard using a hammer and crowbar . The average individual personal PCM fibre exposures for the asbestos removal operatives at the five sites are summarised in table S1 The calculated limits of detection LOD and limit of quantifications LOQ for the average volumes of air sampled are also shown The high concentrations of airborne dust release made sampling problematical and compromised the sensitivity of the analysis and only short peak concentrations are presented Although the average PCM fibre concentration was above 0.08 ml at three of the sites B Y the high concentrations of dust produced at these sites limited the sampled volumes so that at only one site D of these three sites exceeded the LOQ It is important to recognise that these averages include samples taken when there was no extraction from the enclosure and dry scraping with no dust suppression was taking place also at site Y power tools were used Note For PCM analysis LOD is defined in Annex 1 of HSG 248 as a count of 6.5 fibres in 200 fields of view and the LOQ as a count of 20 fibres in 200 fields of view based on background counts on blank filter samples and statistical confidence limits The gravimetric data showed that the average personal dust concentrations were nearly three times higher than the COSHH exposure limit at sites B and Y and at site D it was close to the exposure limit The sites giving the higher PCM fibre concentrations were also the sites which had poor control of dust emissions and the high PCM counts were more to do with the low volume of air sampled and the resultant LODs and LOQs than high fibre counts It was a surprise that site D gave significant PCM fibre concentrations as this type of site involving the careful removal of plasterboard with the TDC attached was monitored specifically because in the previous survey this removal method gave no detectable release of asbestos It should be noted that the TEM analysis did not find any PCME asbestos fibres in the two samples with the highest PCM fibre concentration from this site Samples from site D contained a large number of calcium sulphate fibres and other types of asbestos fibres that did not dissolve during wicking It was noted that a few samples from other sites retained significant numbers of calcium sulphate fibres after water wicking In general the individual samples with high PCM counts were from samples where the calcium sulphate may not have been efficiently dissolved during the wet wicking Table S1 Summary of the site average of the personal PCM fibre concentration for non- . soluble fibres and the calculated average LOD and LOQ Site Site N of | Average volume concentration conetraion for samplessamples sampled soluble fibres ml B 14 23.00 0.13 D 11 18.00 0.29 R 8 84.25 0.065 S 24 38.60 0.057 Y 16 8.76 0.26 LOD 0.07 0.09 0.02 0.04 0.19 LOQ 0.22 0.28 0.06 0.13 0.57 At least two samples with the highest PCM fibre counts were selected from each site for TEM analysis Although the limited volume of air sampled made it difficult to achieve the desired vii analytical sensitivity the TEM count was continued until the analytical sensitivity was at least below 0.08 ml The TEM results were divided into two groups those that used some control at source and those that used uncontrolled dry removal see table S2 Nearly all the TEM samples analysed were collected with no air extraction from the enclosure None of the selected individual personal samples which used some method to control the release at source were found to have PCME asbestos concentrations above 0.08 ml when analysed using TEM This result is in line with previous site sampling results of TDC removal IF2005 and IF2005 and supports the use of 0.08 ml as an upper estimate of the average exposure for the risk assessment in the consultative document CD 205 Table S2 Summary of the TEM analysis of personal samples Site Site Sample Number PCM fibre concentration ml Removal with controls PCME chrysotile fibres ml [| N B 00458/06 00474/06 00156/06 00164/06 R 11671 11675 0.58 0.34 0.41 0.46 0.06 0.07 0.07 0.08 0.07 0.07 0.01 0.02 ND ND ND ND ND 2 S 00326/06 0.05 0.06 3 Removal with no controls S 00321 0.05 0.21 7 R 11641 0.03 0.02 3 11643 11656 0.04 0.06 0.01 0.01 ND 11 11661 0.05 0.02 2 11667 11668 0.11 0.09 0.18 8 0.12 5 Y 00360/06 0.34 00368/06 0.54 ND = non detected NPU off dry 0.05 0.08 ND ND The highest personal PCM samples collected during uncontrolled dry removal gave short term peak exposures ranging from not detected to 0.21 ml Given the type of activities involved and the difficulty in dry scraping surfaces it was unlikely that the four hour control limit would be exceeded Also this type of activity was not compliant with the control of asbestos at work CAW regulations All the TEM samples had low asbestos fibre counts and hence poor precision if The change in the personal airborne asbestos fibre concentrations inside the enclosed area no air extraction is used It was found that on average when doing similar work the personal PCM fibre concentrations at these sites were increased by some % when the extraction was switched off This was in line with the result from a simulation in a HSL test chamber see IF2005 viii The effectiveness of the clearance based on a visual assessment alone . The low amounts of fibres released from TDCs means that visual clearance of dust and debris is more than adequate to ensure that PCM fibre concentrations will remain below the clearance indicator The likely airborne releases from poorly controlled removal The PCM results showed no clear pattern of reduction between dry and wet removal of TDCs at the two sites sampled This is in complete contrast to effective wet removal of other licensed ACMs where uncontrolled dry removal produces a two to three order of magnitude increase in airborne fibre exposures The airborne concentration outside the enclosure ifno air extraction is used As most of the sites had one or more rooms as the enclosure it was not possible to sample outside the enclosure in a meaningful way The only place where escape of airborne dust was likely was at the airlock exit from the enclosure but as these were generally situated outside the building it was again thought to be of little use to sample around the exit in ambient air It is a current requirement that licensed removal sites use at least a three stage entry and exit airlock for person entering and exiting the enclosure with an inward flow of air In the guidance a two stage airlock without any inward airflow has been suggested as sufficientdrTafot test the effectiveness of the two arrangements air monitoring was carried out inside the airlock two flaps away from the source in the enclosure which is equivalent to the second airlock chamber The results showed that although the PCM airborne fibre concentrations inside the airlocks lower with the negative pressure unit NPU on and drawing air into the were switched off the increased concentration was still relatively low Site was seanmcplloesdurweitwhhtehne NPU off when the removal activity was directly over the entrance of the airlock and ssiutruraotuinondianngdatrheeamaenadswurheednvoanlluye ownaesfaltapthweaLs OinQposition This might be considered a worst Although it is hard to draw a conclusion from only two sites and when low wind present outside of the airlock it would appear that airborne fibre speeds were airlock would be low and readily diluted any concentrations outside the The airlock flap system at these sites was designed to allow the ingress of air with a NPU running and there are more effective ways of producing a much more airtight seal to produce a true airlock entry if no NPU was in use Taking into account that measurements were made inside the airlock it is unlikely that PCM fibre releases from the enclosure would exceed 0.01 ml in the entry area surrounding the airlock The airborne exposures that will be experienced by persons reoccupying the building The airborne asbestos fibre concentrations inside enclosures therefore there is unlikely to be a significant during active removal were low been exposure to airborne fibres if the enclosure has downthoroughly cleaned and the area inspected for visible debris before the enclosure is taken Measurements made inside enclosures demonstrated that a PCM fibre the LOQ 0.01 ml was produced from disturbance clearance concentration of around type sampling when sweeping ix several grams of visible debris and dust with a broom for at least 5 minutes and sampling for a period of 1 hour This would be a one off peak i.e. a poor clean up had been carried out by a contractor in breach of CAW and where and the occupier or maintenance personnel had to sweep up the majority of the TDC debris left behind After the first clean up it is unlikely that the small amount of TDC dust and debris remaining would act as a significant future source of airborne asbestos fibre emission In order to investigate with greater precision the potential airborne release from the disturbance of debris remaining following removal of TDC a simulation was carried out in the HSL 9 m dust chamber see 2006 This used about 100g of dry friable dust and debris recovered from the dry removal of the TDC at site R. With an air exchange rate of 2.4 room volumes per hour 30 minutes walking over the debris produced personal PCM airborne fibre concentrations of 0.014 ml for all fibres no wicking was used Given that the amount of debris was more than two orders of magnitude higher than what would be easily seen in a visually clean area and the likelihood of disturbance of such a small amount of remaining debris is much lower it is unlikely that any remaining dust and debris following removal of TDCs would contribute significantly measurable airborne fibre concentrations to the indoor environment The contribution to the airborne asbestos fibre concentration of small amounts of dust and debris after the site was visually cleared are expected to be below 0.0005 ml Implications for the risk assessment For epidemiology and risk assessment the statistic used to represent exposure and dose is the arithmetic average of the annual exposure which is used to derive the cumulative dose in years As nearly all measurements are based on short peak concentrations it is extremely unlikely that removal of TDC could give rise to cumulative exposures for PCME chrysotile fibres above 0.08 ml per year Furthermore it is not expected that PCME chrysotile fibre concentrations would proposed control limit of 0.1 ml over a hour measurement period exceed the Using HSE figures of the current rate of licensed removal of TDCs it is only theoretically possible for 83 workers per annum to disturb TDCs in a way that could approach the level of activity needed to generate the 0.08 ml average exposure for an entire year as assumed in the risk assessment The small increase in airborne concentration when comparing licensed controlled removal with uncontrolled dry removal shows that unlike other licensed ACMs there is a limited amount of additional release that poor practice will generate when compared to the existing regimes used by licensed asbestos removal contractors The difficulty in releasing fibres from TDCs mean that if any debris is left behind as a result of poor clean up the contribution to the exposure of the occupants will be small Once the initial clean up of debris and dust has been carried out it is unlikely to be measurably higher than the ambient background in buildings containing ACMs The additional work in this report supports the risk assessments in CD205 that if CAW regulations and control procedures are applied there will be no predicted premature deaths from asbestos related diseases arising from work with TDCs Conclusions For risk assessment purposes 0.08 ml provides a high upper estimate for the average annual PCM airborne asbestos fibre exposure of asbestos workers removing TDCs It is important to note that a very conservative risk estimate would be obtained based on this figure particularly as it does not take account of any respiratory protective equipment worn by those undertaking TDC removal work The upper estimate of 0.08 ml is applicable to all TDC removal work meeting the CAW regulations Abbreviations and units um ACMs AIB ALPIS micrometer asbestos containing materials asbestos insulation board Asbestos Licensing Principal Inspectors HSE ARCA Asbestos Removal Contractors Association ASLIC AWPD Asbestos Licensing Regulations Asbestos Worker Protection Directive CAW Control of Asbestos at Work regulations CD ERM EU consultative document European Regulatory Method European Union ml FOD FSSU HEPA HSE HSE HSG HSL ISO IF Fibre / millilitre Field Operations Directorate HSE Field Scientific Support Unit HSL High efficiency particulate air refers to high efficiency air filters Health and Safety Executive Health and Safety Executive / Insurance Companies Health and Safety Guidance Health and Safety Laboratory International Standards Organisation Inorganics and Fibres HSL Section name xi LfiO-DLOD litre limit of detection limit of quantification metre Methods of Determination of Hazardous Materials HSE milligramme millimetre not detected number negative pressure unit phase contrast microscopy phase contrast microscopy equivalent quality assurance Regular laboratory Counting Exchange textured decorative coating textured decorative plaster transmission electron microscope time weighted average United Kingdom United Kingdom Accreditation Service World Health Organisation 1 INTRODUCTION 1.1 BACKGROUND The implementation of the amended EU asbestos worker protection directive AWPD 2003 means that changes have to be made to the existing control of asbestos at work CAW regulations 2002 The Health and Safety Commission is also taking this opportunity to propose changes to asbestos licensing and prohibition regulations The current asbestos a licensing regulations ASLIC as amended in 1999 prescribe that work with certain of types of asbestos containing products must be undertaken by licensed asbestos removal if more than a total of two hours work is to be carried out It is proposed that thicsonitsratoctboer amended in revised CAW r^'gulations2006 as amendments to the EU AWPD directive have introduced a new concept of Sporadic and low intensity exposure to determine whether the work is notified to the responsible authority In Great Britain notification is normally required for licensed asbestos containing materials ACMs and it is proposed in future to fully align notification and licensing using the Sporadic and low intensity exposure cut off The amended EU AWPD specifically allows member states along with their social partners to lay down practical guidelines for Sporadic and low intensity exposure The practical approach proposed in the consultation document CD205 to define sporadic and low intensity exposure would mean that there will be a further reduction in the time currently 2 hours that high risk materials such as thermal insulation spray coatings and lagging can be worked on In general these materials contain both a high proportion of asbestos and the higher risk crocidolite and amosite blue and brown asbestos Also these materials can readily release airborne asbestos fibres especially if worked on without the use of controlled removal methods a However one group of currently licensed material known as textured decorative coatings TDC only contain the lower risk chrysotile white asbestos see figure ) and it is present in a much lower percentage than in other licensed see figure 2 materials As the chrysotile in TDCs is more tightly bound in resistant matrix compared to other licensed asbestos it does not readily release airborne asbestos fibres when worked on These characptreordisutcitcss separate TDC from other licensed asbestos materials in that it represents a much lower level of asbestos exposure and risk to workers compared with other licensed materials see figure 3 As part of the consultation it was proposed that TDCs are removed from the licensing regime but will continue to come under the same set of stringent control requirements detailed in the CAW regulations and which apply to work with all asbestos containing materials ACMs A number of changes to the practical control measures for removal of TDCs included in the approved Code of Practice and guidance have also been proposed * use of stage instead of a 3 stage entry airlock e decontamination in the airlock e use of visual inspection without air sampling to ensure that the site is ready for re- occupation HSE in response to early comments received during the consultation commissioned HSL to carry out further measurements of airborne fibre concentrations during the removal of TDCs to further assess the effects of the proposed changes in the control regime risk Relative Crocidolite blue Amosite brown Chrysotile white and Figure 1 Relative risk Logarithmic scale by asbestos type as assessed by Hodgson Darnton 2000 TDC : TDC 6 Plastics aa Floor tiles f Bitumen a Cement @ T T T T J 0 20 40 60 80 percentage of asbestos | 100 Figure 2 Typical weight percentages of asbestos in licensed and licensed asbestos products air conc ml 0.1- 0.01 Spray & lagging AIB Product type TDC dry Iwet Figure 3 Typical airborne personal exposure concentrations monitored at licensed asbestos removal sites for wet and dry removal of various licensed asbestos products Logarithmic scale with the axis adjusted to the proposed 0.1 ml control limit 1.2 OBJECTIVES The objectives of the work were to determine the 1. Airborne fibre concentrations releases during the removal of textured decorative coatings TDCs from a wider range of surfaces to those reported in an earlier survey see IF2005 2. Change in the personal airborne asbestos fibre concentrations inside the enclosed area during the removal of TDCs if no air extraction is used to keep a reduced pressure inside the enclosure and 3. Effectiveness of the clearance following removal of TDCs based on a visual assessment alone A draft sampling and analysis protocol was developed and sent to HSE for comment The draft protocol was also distributed to the Asbestos Removal Contractors Association ARCA for comment and operation in carrying out this additional work some of which they had , requested The protocol is given in annex 1 and the response from ARCA is given in annex 2 ARCA's response and further points raised by HSE lead to some additional questions being addressed by the research These included 4. What are the likely airborne releases from poorly controlled removal of TDCs 5. What is the airborne concentration outside the enclosure during removal of TDCs if no air extraction is used 6. What are the airborne exposures that will be experienced by persons reoccupying a building following the removal of TDCs This report summarises the results from the additional work carried out to meet the objectives and answer the questions listed above The more detailed individual site reports are referenced 2 SITE SELECTION AND STRATEGY 2.1 SITE SELECTION AND ARRANGEMENTS HSL contacted HSE Asbestos Licensing Principle Inspectors ALPI's in three of the HSE's Field Operations Directorate FOD regions The request was first to locate sites at which TDCs had been notified for removal and secondly to establish the way in which an appropriate waiver could be issued so that variations from normal licensing conditions could take place HSE personnel at several regional offices were then asked to send any notification for TDC removal to HSL who assessed the site for its relevance to the objectives of the work Possible sites were then discussed with the supervising HSE Inspector and ALPI and if agreed the asbestos removal contractor was contacted by HSL staff The purpose of the research was then discussed with the asbestos removal contractor and a copy of the protocol was sent Following further discussion HSL asked the contractor whether they could sample and then secured the operation of the main contractor and site owner Sites of interest were those where asbestos was being scraped or removed in some other way from a resistant surface e.g. from concrete hard finishing plaster pebbledash and brickwork One site was also visited where it was reported that careful removal of plasterboard from a ceiling was taking place In the previous survey funded jointly by the HSE and some insurance companies referred to as HSE study IF2005 it was found that at the three sites that had reported careful removal of the TDC no measurable chrysotile asbestos was found in the samples analysed by TEM and further confirmation of this was sought Only one removal from concrete was present in the notifications received and conversations with removal contractors confirmed that removal of TDC from this type of substrate was relatively rare 2.2 SITE SELECTION AND SAMPLING BIASES The previous HSE survey of TDC removal had been arranged so that no involvement of HSE or HSL was apparent to the asbestos contractor only three of the 35 sites were monitored by HSL's FSSU staff for QA purposes The only difference from normal was that instead of the laboratory representative arriving near the end of the job to clear the site and issue a certificate of occupation they arrived earlier in order to conduct personal monitoring of the workers carrying out the removal inside the enclosure Personal monitoring is a requirement of the assessment process and would be a familiar occurrence to asbestos operatives The absence of HSE and HSL staff was intended to ensure that workers carried out their work in an unbiased way whilst personal sampling was being carried out In this study it was necessary for HSL staff to go onto site to sample and to make detailed _ arrangements with both HSE and the contractor to arrange a waiver Although no HSE personnel visited the site or contacted the site supervisor and operatives directly the purpose of the sampling and involvement of HSL was known to all site operatives This might be expected to promote the use of best practice but at all the sites sampled for various reasons the operatives were up against tight deadlines and the pace of the work observed was usually fast with additional operatives being used It could equally be argued that the knowledge that the sampling was being carried out specifically to investigate a proposal to remove TDCs from licensing could provide an incentive for the licensed asbestos removal contractor to ensure high concentrations of asbestos fibres Although some of the HSL requests for sampling were refused by asbestos removal contractors a number of suitable sites were found and sampled It is not verifiable whether the participation at some sites produced a biased sample set but as intended the sites selected covered a range of different substrates 5 3 SAMPLING AND ANALYSIS METHOD AND ISSUES 3.1 SAMPLING METHOD The sampling method is outlined in Annex 1 and more detailed information is given in the individual site reports see reference section The main purpose of the sampling was to collect the airborne dust on mm diameter membrane filters 0.8 ...mpore size mixed esters of cellulose to determine airborne fibre concentrations Fibre sampling was carried out using conductive cassettes with flow rates set at between 0.5 - 10 minute based on field 1 conditions The sampling was carried out in accordance with MDHS 39/4 and also HSG 248 annex the new revised method the current method Additional sampling of the mass concentration of airborne particulates inhalable and respirable was also carried out using a mm entry diameter inhalable sampler and / or respirable selecting cyclone operating at 2.0 and 2.2 minute respectively 3.2 ANALYTICAL METHOD Airborne fibre concentrations were determined in accordance with MDHS 39/4 and HSG248 using both the current European Reference Method ERM and the WHO counting rules The WHO counting rules are scheduled to replace the ERM counting rules in 2006. Quarter filters were prepared in the normal way and counted using both sets of counting rules The counting rules were applied to the same fields of view so the poor precision associated with fibre counting did not mask differences A second set of quarter filters was also prepared and placed on wet blotting paper in a Petri dish to remove any soluble particles / fibres After wicking for approximately one hour and then leaving to dry the filters were prepared and counted by PCM using both sets of counting rules All four of the PCM analyses on each filter were carried out using light microscopy at X500 magnification with phase contrast optics PCM to count the number of visible fibres i.e. particles that are > mlong < 3...mwide and with a length to breadth ratio > There are two main differences between the ERM and WHO counting rules One is the in which fibres that attached to or covered by particles are counted The way 1 of the AWPD 1983 only counts a fibres or a fibre bundles meceutrrienngt tmheetshiozde arelqsuoirseemeeanntsneixf they are not attached to other greater than 3 ...min diameter i.e. respirable fibres only The newer World Health Organisation WHO method counts all fibres meeting the size criteria regardless of other particles The second major change introduced by the WHO method is to allow for fibre identification / discrimination to take place once the initial PCM count has been made Previously for regulatory determination of the control limit it was required to accept the PCM count as a sampling measure of the actual asbestos fibre concentration While this was broadly correct for exposure during manufacturing of ACMs it has been recognised that there are many sources of asbestos fibres which can be released during maintenance and removal work Previous experience has shown that many of the particles released from the disturbance and removal of TDCs are calcium sulphate In particular texture decorative plaster such as Artex contains 2-4 chrysotile asbestos with calcium sulphate as filler Plastered surfaces plasterboard onto which TDCs are and commonly applied are also largely made from calcium sulphate Unfortunately calcium sulphate gypsum particles regularly occur in a fibrous form with dimensions that meet the PCM fibre counting criteria 6 This means that most of the PCM fibre counts for TDC removal work are calcium sulphate fibres and asbestos fibres usually represent only a small and variable percentage of the fibres counted The variability will also depend on the amount of the underlying plaster that is disturbed HSL has pioneered two methods of discrimination e A method based on dissolving the calcium sulphate fibres and particle before analysis to remove them from the count The PCM count is then one for soluble fibres For selected samples the use of an additional analysis based on analytical transmission electron microscopy with water dissolution if necessary Both methods have been applied to a selection of the samples to help determine the asbestos fibre concentration The units of measurement are directly relevant for the risk estimation and are based on historical counting conventions for asbestos in industrial manufacture going back to the 1960s The additional analysis by analytical transmission electron microscopy TEM uses electron diffraction and energy dispersive ray analysis to identify the individual fibres and the type of asbestos A third quarter filter was prepared for the TEM counting sizing and identification Fibres of a size which would have been visible and counted by PCM fibres > ...mlong > 0.2 3 ...mwide and with an aspect ratio > were analysed This allowed PCM equivalent PCME airborne asbestos fibre concentrations to be calculated as detailed in the international standards Organisation method ISO 10312 for asbestos in ambient air The United Kingdom Accreditation Service UKAS accredits HSL for all the fibre analyses mentioned above except the wicking preparation concentrations The total and respirable dust were determined by weighing the filters in accordance with MDHS14 The cyclones were fitted with membrane filters suitable for PCM analysis and these filters were also analysed for their PCM fibre count 3.3 PCM SAMPLING AND ANALYSIS ISSUES Previous experience has shown that sampling of TDCs is extremely difficult as many sites produce high concentrations of airborne dust This is partly the result of poor dust control at source and the difficulty to effectively wetting both the TDC and the underlying substrate e.g. plaster or plaster board The effect of high airborne dust release is to readily overload the membrane filters with particles in relatively short sampling times This means that not only must multiple sequential samples be collected to try and measure the hour exposures required for comparison to the control limit but also each individual filter has a low sample volume usually between 5L and 100 L during work activity and consequently a reduced analytical sensitivity This problem is illustrated using the results from the previous survey shown in figure 4 see 2005 The limit of detection LOD and limit of quantification LOQ used was derived from several thousand filter blank counts carried out for the UK RICE PCM fibre counting proficiency testing scheme See Annex 2 of HSG248 mlLTMNLTTMNT LTMNConcLTMNLTTMNT LTMNT fibre LTMNT NS LTMNT LTMNT PCM 0 0 : 1 PCMConc ml = LOD ii i 50 100 150 200 Volume of air sampled ) 250 Figure 4 PCM fibre concentrations of treated samples from the HSE against the calculated limit of detection study superimposed LOD v volume of air sampled ml Conc fibre NS PCM 0 50 100 150 200 Volume of air sampled ) 250 Figure 5 PCM fibre concentrations of treated samples from the HSE study superimposed against the calculated limit of quantification LOQ v volume of air sampled 8 222 samples 25 SF samples 222 samples 15 E of 10 #1 /h = No eye 10--19 20-29 11010-0---119920-2390-3930-39 5400-49-5960-660-699 70-7790-79 90-99 80-89 90-99 100-2 149 01500 -199 -22 00-249 49 300 30-39 30-39 40-49 40-49 50-59 50-59 60-69 60-69 70-79 70-79 80-89 80-89 90-99 100-149 150-199 250-299 250-299 100-149 150-199 200-249 250-299 90-99 > Volume of air sampled Figure 6 Distribution of sampled air volumes used for PCM counting in the HSE study requiring treatment before counting was possible Clearly with poor control at source and hence high dust concentrations and simplistic assessment of the results of short term low volume samples can lead to biased averages and seemingly high airborne fibre concentrations at or above the control limit However the statistical relevance and precision of the results renders such interpretations suspect especially when the control limit is defined over a hour time weighted average TWA N.B. it is an 8hour TWA in the AWPD directive In short peak short results based on low volumes of sampled air are likely to produce much higher results than those which would be obtained during the regulatory hour control limit Both the ERM and WHO PCM methods recommend that 240 litres of air is filtered to measure personal exposure Site conditions meant that this was only possible for ~ % of samples in the previous TDC survey usually when low dust activities were being carried out e.g. final clean up 3.4 DETERMINATION OF THE ASBESTOS CONCENTRATION At best wet wicking PCM samples before analysis will remove most of the readily soluble fibres and particles e.g. calcium sulphate but there is no certainty that the remaining non- soluble fibres will be asbestos To assess the asbestos concentration it is necessary to use analytical electron microscopy to count size and identify fibres of the equivalent size These are referred to as PCM equivalent PCME asbestos fibres TEM analysis as set out in ISO 10312 takes a lot longer than simple PCM counting as higher magnification are used X5 000 - 11,500 In practice at the magnifications used by HSL the area of the filter scanned the PCM 200 fields of view is equivalent to 20,000 fields of view in the TEM at tbhye magnification 11,500X used for sizing Therefore the TEM identification of the asbestos is used selectively and does not achieve the same analytical sensitivity as the PCM Due to the high dust concentrations at some of the sites and the very low volumes of air that the TEM analysis was extended at most sites until sampled meant an analytical sensitivity of < 0.1 ml was achieved This means the results have poor precision 4 RESULTS AND DISCUSSION Variable amounts of calcium sulphate fibres can be produced depending on how much the plasterboard or plaster is being scraped As this may change over time only the water wicked samples giving counts excluding easily soluble fibres have been included in this report Similarly only results using the WHO counting rules which will be summary onwards have been given unless expressly stated otherwise Although the PCuMsecdonfcrenotmra2t0i0o6n of soluble fibres will not give a direct measure of the asbestos fibres it gives an upper estimate of what the asbestos fibre concentration could be a A limited number of TEM analysis of PCME asbestos fibres have also been site As can be seen in figure 7 it was only possible to low reported for each filter became overloaded Few individual sample volumes of air before the samples exceeded the LOQ and these results should be reported as the calculated LOQ However it was felt that reporting many of the results as less than the LOQ based on statistical expectations would be unhelpful and would mask trends in the data Therefore even though the statistical precision was the actual any of fibres seen was used to calculate the fibre poor number above the LOQ or LOD concentration regardless as to whether this was 4.1 THE AIRBORNE RELEASES FROM THE REMOVAL OF TDC FROM A WIDER RANGE OF SURFACES a HSL report IF2005 summarised the exposure information known to HSL for TDCs from a variety of surfaces and substrates removal of However the study was criticised for using a number of different removal methods having a limited sample set especially with respect to the lack of sites where removal by scraping from resilient under layer e.g. concrete plaster and brickwork had taken place as it was considered that hard surfaces have the generating significantly higher airborne asbestos fibre potential for summarised in this concentrations The additional sites report are described in table 1. Site Y offered a rare powered chisels removal of textured decorative paint from the outside subsotprpaotretuonfiatybutiolmdoinngito- r Table 1 Description of activity at the additional sites monitored Site reference Description and controls Scraping painted TDC from finishing plaster on walls and the use of a hammer B and bolster to remove painted TDC and plaster from a chimneybreast Tex was used to soften the TDC being applied on the previous day and at the gel work start of A hammer was used to punch holes in TDC on crowbar was used to a plasterboard ceiling and a remove plasterboard in large pieces Occasional hand spraying of the plasterboard to reduce dust concentration TDC R Scraping from underside of a ceiling both dry and using steam removal S DScaryap1inWgeTtDaCndfrdroym sccornacprietneg ceilings sprayed with remover Day 2 Wet scraping only Y Use of a Kango powered chisel to remove TDC paint on the pebbledash on the outside of a building no controls 10 4.1.1 PCM results PCM personal airborne fibre concentrations are given in table 2 which includes the calculated LOD and LOQ for the average volume sampled The high concentration of airborne dust at some of the sites meant that the sampled air volumes were of necessity very low to prevent overloading the filter see figure 7 At site Y where powered chisels were used the maximum air volume that could be sampled was 10 litres some 24 times lower than recommended in HSG248 Consequently the average airborne fibre concentration was barely above the LOD at this site as defined from blank filter counts and the seemingly high concentration have no statistical significance Sites B and S also gave average PCM fibre concentrations between the LOD and LOQ and the statistical relevance of these results are also questionable Only at sites D and R were the average site PCM concentrations marginally above LOQs based on the average volume of air sampled Site D had the highest PCM fibre concentration and contained much higher concentrations of calcium sulphate and other asbestos fibres than those from the other sites sampled This was surprising in that this was meant to be gentle removal of the TDC and substrate using a method which had previously given low PCM counts and no detectable asbestos fibres by TEM At site B one relatively high PCM fibre concentration 0.58 ml had a large influence on the PCM average Table 2 Summary of the site average of the personal PCM soluble fibres and the calculated average LOD and LOQ N of | Average volume Concentration of Site personal sampled soluble PCM samples B 14 L 23.00 WHO fibres ml 0.13 11 18.00 0.29 R 8 84.25 0.065 S 24 38.60 0.057 Y 16 8.76 0.26 fibre concentration for non- LOD 0.07 0.09 0.02 0.04 0.19 LOQ 0.22 0.28 0.06 0.13 0.57 25 samples of 1b] No No 5+ 0 i ; Hel ES Hb Blo of 7 Volume of air sampled L Figure 7 Distribution of sampled air volumes for personal samples counted by PCM 11 4.1.2 TEM results divided into samples where some uncontrolled dry removal The attempt to control dust releases were taken and into TEM analysis of site D which gave the highest PCM fibre sought effective removal method was hour control limit would be exceeded Therefore it is considered unlikely than the proposed 4- Table 3 Results of TEM analysis of PCME asbestos samples with high PCM fibre fibres on selected personal counts from each site Site B R S S R Y ND = non Sample Number PCM fibre concentration ml Removal with controls PCME ml 00458/06 00474/06 00156/06 00164/06 11671 11675 00326/06 0.58 0.34 0.41 0.46 0.06 0.07 0.05 0.07 0.08 0.07 0.07 0.01 0.02 0.06 Removal with no controls 00321 0.05 11641 0.03 11643 0.04 11656 0.06 11661 0.05 11667 0.11 11668 0.09 00360/06 0.34 00368/06 0.54 detected NPU off dry 0.21 0.02 0.01 0.01 0.02 0.18 0.12 0.05 0.08 chrysotile fibres N. ND ND ND ND ND 23 23 7 3 ND 11 2 8 5 ND ND 12 4.1.3 Gravimetric dust concentrations The average airborne dust concentrations at the sites are summarised in table 4. Usually at a given site either the inhalable or respirable dust concentrations were monitored It can be seen that there was a direct relationship between dust concentration and the average time of sampling for the fibre concentration with sites B and Y exceeding the COSHH exposure level 4 mg for respirable dust and 10 mg for inhalable dust Table 4 Summary of average gravimetric airborne dust concentrations Site Average inhalable dust Average respirable dust concentration mg concentration mg B 28.2 - D3.1 R 2.24 0.45 S 2.66 - Y11.4 4.1.4 Summary of site data Overall only two of the five sites gave statistically relevant LOQ average PCM fibre counts for insoluble fibres Only one of these was higher than the overall for individual personal samples from the HSE survey 0.09 ml The samples average from this site D contained many asbestos fibres and TEM counts to date show that low numbers of a chrysotile fibres were present in them It should be noted that the data includes periods of dry removal and periods where the NPU was switched off Site Y which used Kango chisels to remove chrysotile containing paint and substrate was particularly difficult to monitor as was site B where a hammer and bolster was used to remove both the TDC and the underlying material from the chimneybreast Although the analytical sensitivity of the TEM analysis was very limited by the low volume of air sampled analysis of selected samples with high PCM fibre counts showed that low concentrations of PCME asbestos fibres were present and these were below 0.08 ml 4.2 CHANGE IN THE PERSONAL AIRBORNE ASBESTOS FIBRE CONCENTRATIONS INSIDE THE ENCLOSED AREA IF NO AIR EXTRACTION IS USED TO KEEP A REDUCED PRESSURE INSIDE THE ENCLOSURE The use of air extraction is primarily to prevent spread of airborne fibres from the enclosure to adjoining areas Its effectiveness in lowering personal exposures will be both limited and variable Personal exposures are usually multiple times higher than static the airborne fibres and dust is generated by the actions of the removal operativeexupsousaullryesinasclose proximity to their respiratory region The sampling protocol called for measurements to take place with the filtered air extraction also referred to as negative pressure units NPU both on and off As far as possible this was done for similar work and levels of disturbance during both regimes to allow direct comparison between the two The average for the five sites listed in table 5 show that overall the personal concentrations were some 23 greater with the NPU switched off This was similar to that reported for laboratory simulations see IF2005 Although the increase is well within the 95 confidence interval this was a consistent trend for 4 of the 5 sites and was an average for many 13 samples so this is taken to be broadly representative of the personal exposure expected average increase in soluble Table 5 PCM WHO fibre concentration ml for on and off at the 5 sites sampled fibres with air extraction Site B D R S Y Average NPU on ml 0.14 0.67 0.04 0.05 0.26 0.232 NPU off ml 0.1 0.96 0.06 0.05 0.26 0.286 Difference % 71 143 150 100 100 123 4.3 EFFECTIVENESS OF SITE CLEARANCE BASED ON A VISUAL ASSESSMENT ALONE The PCM results from the site clearance tests were all carried out with visible monitoring are given in table 6. The disturbance air debris and dust on the floor with the aim to likely maximum concentrations that could be replicate the performed and the generated if a partial or improper clean up was occupants were left to clean up the mess The disturbance method used was sites a second disturbance was carried out around the minutes and the debris was swept into small point of the sampling after about 30 piles photographed and collected for weighing collected froma floor area of about 14 m Some clearance samples were also analysed by TEM and the in table 7. The results were similar to the PCM asbestos concentrations are given concentrations around the clearance level results and showed that PCME asbestos fibre 0.01 ml can be generated when significant visible debris and dust remain and are vigorously disturbed All the sites where HSL staff carried out disturbance air form of visual assessment as debris monitoring would have failed any was readily visible on the floor All three sites where HSL staff was still present failed the visual inspection and required further assessment during the formal certificate of reoccupation sometimes extensive cleaning It was also noted that the degree of disturbance used air monitoring was far greater than that by HSL staff to carry out the disturbance analyst simulated disturbance used by the commercial laboratories In one case the area Only marginal contact activity using a nail brush small scrubbing brush to disturb the with the surface was being made during some of the time The will result in low fibre and dust concentrations in the air and renders the clearance air testing of little value ' a Overall there was no doubt that a reasonable clean up which leaves no easily visible dust and debris will not give rise to airborne chrysotile concentrations above the clearance indicator even when valid disturbance air test is carried out The low amounts of fibres released from TDCs means that visual clearance of dust and debris is more than adequate to ensure that fibre concentrations will remain below the clearance indicator One analysts stated that he had not had to fail a TDC removal site on the initial clearance air test concentration for some 50 sites Ultimately the low fibre release from this material means that removal sites are unlikely to exceed the clearance indicator unless a very poor clean up has been done The requirement in the CAW regulations is for the area to be thoroughly cleaned before taking down the enclosure If after the enclosure is removed small amounts of dust and debris remain these will rise to high concentration of airborne fibres and can be cleaned up by the contractornuostinggivea HEPA vacuum or wet wiping with minimal exposure Table 6 Summary of PCM results for clearance samples using different preparation methods and counting rules . Description of clearance and activity Site B Room swept for 5 minutes with broom on walls and floor visible debris easily swept into small piles The external laboratory carrying out certificate of re- occupation monitoring swept the room a small scrubbing brush for a further 5 minutes after about 40 minutes of sampling Samples with many particles Site D Two separate rooms swept with broom for 5 minutes at the start of the sampling period visible debris was visible on the floor during Additional clean up ordered by independent analyst attending site later sweeping Site S Four individual rooms swept for 5 minutes from ceiling downwards at start of sampling and for a further 2.5 minute after 30 minutes of sampling samples with many particles All four rooms had significant visible debris Site Y Inside enclosure outside building visible debris PCM 0.004 0.005 0.005 0.011 0.011 0.005 0.010 0.010 0.010 0.010 0.013 0.013 0.014 0.014 0.004 Table 7 TEM results from disturbance air sampling PCM fibre Site Sample Number concentration ml D 00167 0.01 S 00355 | 0.009 NPU off dry sweeping 00356 0.010 PCME chrysotile fibres # ml N 0.002 1 0.0099 5 0.012 6 15 4.4 TRHEEMOLVIKAELLY AIRBORNE RELEASES FROM POORLY CONTROLLED The control of emission at source is a key requirement of all reducing personal exposure Effective health and safety legislation in method to reducing dust emission wetting the material being worked upon is the key Other secondary containment methods such as local exhaust collection and barrier methods such as wrap and cut and glove bags are also used 4.4.1 PCM results from site monitoring The effectiveness of the control measures in was taking place and by carrying out ofutshee was tested at two of the sites where scraping part removal with no attempt at dust suppression e.g. dry The PCM results are given in table 8 Table 8 Comparison of PCM WHO airborne and dry removal concentrations of soluble fibres for wet Site suppression method S sprayed solvent R Steam removal Dry PCM WHO with NPU off 0.05 0.12 0.06 0.06 airborne concentrations of soluble Wet with NPU Dry with NPU off on 0.03 0.05 0.06 0.07 0.04 0.03 0.04 fibres ml Wet with NPU on 0.05 0.07 Not done Not done It can be seen that the PCM results showed no clear removal of TDCs at these two sites This is in pattern of reduction between dry and wet other licensed ACMs where complete contrast to effective wet removal of wetting produces a two to three orders of magnitude reduction in airborne fibre exposures where the dry layer begins Although the build up of softened may have some effect in material on the end of the scraper suppressed removal for both suppressing airborne release the difference between dry and scraping and demolition of TDC seems to be small weaker layer demolition However completely dry scraping is particularly difficult do attached to a substrate has a to unless the TDC is removal is needed for that easily detaches see site R Therefore some aid to scraping which softens the TDC and release from the dry surface along which the partially suppresses the airborne scraper runs As the control at source during scraping appears treatment only to be partially effective and some removal localised steam softening and removal While it is possible that more energetic methods such as powered tools powered sanders and dry grit blasting could be used their use will almost certainly result in a breach of the CACW AW regulations 4.4.2 TEM results from site R during uncontrolled dry removal and steam removal Site R gave an opportunity to monitor in detail the airborne fibre concentrations produced by uncontrolled dry scraping The TDC had been applied to a distempered plaster ceiling and the friability of the paint layer meant that the TDC layer was poorly adhered and could readily be scraped away even when dry The PCM and TEM results for personal samples are given in table 9. The activity carried out was intended to be an example of poor practice where uncontrolled dry removal took place with no extract air inside the enclosure It can be seen that chrysotile asbestos PCME fibre concentrations were above 0.1 ml during the peak removal and sweeping activity Although the airborne fibre concentrations were calculated from the CAW small numbers of PCME chrysotile fibres that were found 0 - 11 this gives poor precision but shows that short term peak concentrations of around 0.1 ml can be produced by uncontrolled dry removal or sweeping of friable material These activities which are not allowed under the CAW regulations and did not exceed the proposed minute limit 0.6 ml The airborne PCME asbestos concentrations for controlled removal using steam to soften and wet the coating were lower than the uncontrolled dry removal but the low numbers of fibres counted make it difficult to show whether this was statistically significant in terms of 95 confidence intervals All the PCME asbestos fibres found were identified as chrysotile Table 9 TEM PCME airborne asbestos fibre concentrations at site R during uncontrolled dry removal Sample Number Activity 11641/05 11643/05 R dry scrape M dry scrape 11656/05 R dry scrape 11661/05 M dry scrape 11667/05 11668/05 11671/05 M cleaning and dry sweeping R cleaning and dry sweeping R steam scrape 11675/05 M steam scrape Total / average * NPU was on only for these samples No of asbestos fibres 3 0 11 2 8 5 0 2 31 TEM PCME | chrysotile concentration ml 0.019 PCM fibre concentration ml 0.03 0.000 0.04 0.115 0.06 0.019 0.06 0.184 0.11 0.124 0.09 0.000 0.06 0.019 0.07 0.060 0.065 17 4.5 THE AIRBORNE CONCENTRATION OUTSIDE AIR EXTRACTION IS USED THE ENCLOSURE IF NO open for prolonged periods The reasons for this with the supervisor outside the were due to operatives trying to communicate placement of equipment and enclosure bags at the waiting for further supplies and inappropriate operatives were active double entrance to the airlock It was also the area were the time a single flap was all that bagging asbestos waste etc. Therefore for some of the sampling separated the middle chamber from the enclosure The PCM results of the static sampling carried out inside the airlock with the NPU on and NPU off are summarised in table 10 the Table 10 Results of the static monitoring of the PCM WHO airborne fibre concentrations of untreated fibres inside the airlock and the enclosure at two sites Sample details Volume of PCM fibre air sampled | concentration During removal Site S During removal in 2nd bag airlock NPU on Site S in 3rd stage of airlock NPU on Site S During removal with activity very close to airlock 2nd stage of airlock with NPU off Note an operative was ostfatnhdeisngamipnltihnegfpiresrt isotadge and holding a flap open during most litre * 1124 264 90 ml 0.001 0.004 0.05 Site B During removal NPU on During removal NPU on During removal NPU off 95 188 0.018 0.001 During removal NPU off 560 0.002 Removal activity was far from airlock and low 240 0.007 airborne fibres in the vicinity of the airlock The sampling evidence available showed that PCM airlocks were low when the NPU airborne fibre concentrations inside the the removal activity was are switched off Site S was sampled with the NPU off when directly over the entrance of the airlock and only one flap was in position The measured airborne fibre surrounding area and when considered a worst situation was at the concentration in what might be LOQ Although it is hard to draw conclusion from a to produce true airlock entry if no NPU into account that measurements were made was in use Using the existing design and taking releases from the enclosure would inside the airlock it is unlikely that PCM fibre was situated exceed 0.01 ml in the area close to where the airlock entry 4.6 THE AIRBORNE EXPOSURES THAT WILL BE EXPERIENCED BY PERSONS REOCCUPYING THE BUILDING a As the airborne asbestos fibre concentrations inside enclosures during active removal are low _ then there is unlikely to be significant exposure to airborne fibres if the enclosure has been thoroughly cleaned and the area inspected for visible debris before it is taken down Measurements inside enclosures which had visible debris and dust demonstrated that a clearance level is produced 0.01 ml when sweeping with a broom for 5 minutes This would be a one off peak if poor clean up had been carried out by the contractor in breach of CAW regulations and the occupier or maintenance personnel had to sweep up the TDC debris left behind After the first clean up it is likely that little asbestos containing material will be left to act as a significant source of airborne emission Inspecting sites for the spread of debris outside the enclosure is relatively easy If operatives carrying out the work leave the enclosure and airlock still wearing contaminated footwear and overalls it is possible to spread debris outside of the work area At the sites visited there was some evidence of debris spreading inside the airlock and reducing the airlock from three to two chambers will increase the potential for debris to spread outside the airlock However as we are unable to assess the difference between the two and three stage airlocks in this current study we have INSTEAD looked at the potential effect that any debris will have on the airborne exposures In order to investigate the potential airborne release from the disturbance of debris left following a removal of TDC with greater precision a simulation was carried out in the HSL 9 m3 dust chamber see 2006 This used over 100g of dry and friable dust and debris gathered from site R where dry removal of the TDC had been carried out With an air exchange rate of 2.4 room volumes per hour 30 minutes walking over the debris gave personal PCM airborne fibre concentrations of 0.014 ml for all fibres no wicking was used Given that the amount of debris was more than two orders of magnitude higher than what would be easily seen in a visually clean area and the likelihood of disturbance of such a small amount of remaining debris is much lower it is unlikely that any remaining dust and debris would contribute significantly measurable airborne fibre concentrations to the indoor environment The contribution to the airborne concentration of small amounts of dust and debris after the site was visually cleared are expected to be below 0.0005 ml 19 5 IMPLICATIONS FOR RISK ASSESSMENT 5.2 THEORETICAL MAXIMUM NUMBER OF HIGH ESTIMATE OF THE PERSON EXPOSED AT THE EXPOSURE CONCENTRATION decontamination The data available from HSE licensed removal database showed days per year spent on TDC work is that the current number of job 20,000 with approximately 47,000 worker days per year Assuming as above a person was working on TDC for 8 hours would only be possible for a day for 240 days a year it removal is 196 people to be exposed in this way before all licensed accounted for Even then this is a substantial overestimate of the time TDC physically disturbing removing the material as spent actually also carried out e.g. travel to site site set a variety of non- or low exposure activities are wetting agents final clean up changing and application of that depending on the sizeuopf tehnecljoosbusrettheaatrodvoerwna equipment maintenance etc It is estimated one half of the time could year only something between one third and realistically be spent physically disturbing the TDC i.e. 42 if midpoint is used Therefore the actual exposure of 0.08 ml could only theoretically take place concentrations two to three times lower than the realised and a larger number of workers will be conservative average of 0.08 ml could be exposed for a shorter time normally distributed broadly representative of the substance of concern Unfortunately all of the above activities taking place and based on the do not apply to the TDC data Removal of TDCs gives rise to low airborne the LOD and LOQ even if 240 litres exposures of PCM fibres which are often close to of air can be sampled Also the filter blanks measurable background counts which contribute to the measured PCM give concentration Failure to 20 adequately control dust emissions at source makes the situation far worse in that the LOD and LOQ approach or even exceed the value of the control limit Therefore the distribution of the individual samples is constrained and biased and is no longer a normal distribution Although no corrections for the bias has been made nor for the fact that the PCM counts of soluble fibres is an overestimate of the asbestos fibre concentration it is clear that the PCM average is likely to be an overestimate of the peak short term concentrations The current and updated EU AWPD directives define the exposure limit over an hour working period UK practice has been to use a 4- hour time weighted average for the control limit which already provides a more stringent control limit of up to twice that required by the directive if work is undertaken over a hour period 5.4 MEASURED CONCENTRATIONS FROM THE ADDITIONAL SITES Taking into account the sampling and analytical limitations and the statistical precision and relevance of results below the limit of quantification there is no evidence from the additional monitoring of the short term peak concentration carried out on surfaces where the TDC is being scraped and chiselled off that the estimated average of 0.08 ml for the annual exposure will be exceeded by any worker over a period of a year engaged in TDC removal provided the CAW regulations are applied 21 6 APPENDICES 6.1 AIM PROPOSED PROJECT TO MONITOR PERSONAL FIBRE CONCENTRATIONS OF WORKERS INVOLVED IN THE RENOVATION OF TEXTURED DECORATIVE REMOVAL AND COATINGS PHASE 2 The aim of this work is to collect data on fibre emission from textured decorative coatings removed under licensed work with asbestos containing build on the experience of phase 1 and unlicensed conditions It is intended to The results will be used to inform further the consultation by HSE on whether decorative coatings should continue to be a licensed asbestos material INTRODUCTION The work in phase 1 showed that removal contractors very high dust concentrations were produced by licensed number of during the removal of chrysotile containing textured decorative countable sampling and analytical strategies were developed for and during phase coatings A 1 to samples which were not overloaded This however meant that try to get times and low volumes of air had to be very short sampling to above the proposed control limit collected that often reduced the limit of quantification characterise the fibre of 0.1 ml This required pooling of several samples to -0.5 -0.5 min it concentration Also in the later samples using much lower flow rates 0.2 was decided to monitor for longer periods The release problem This caused the PCM fibre count to include calcium sulphate fibres and to The same principles are to be extended to this further been produced below As sites will be work and a generic project design has made to accommodate the different it is expected that variations will have to be types of work taking place and local conditions PROJECT DESIGN The proposed project is designed to 22 * Collect personnel exposure data fibre and mass concentration during the repair renovation or removal of damaged ceilings or walls coated with asbestos containing textured decorative coatings Compare the personal exposures from licensed and simulated unlicensed appropriate controls as required by CAWR and the proposed ACOP . * Compare the clearance levels from licensed and unlicensed removal work with To achieve this where possible the full enclosure built for licensed removal will be divided into two halves one for licensed removal and the other for unlicensed type removal with a temporary plastic barrier in between with a doorway entrance flap cut to allow persons and air to pass through but can be sealed up later to limit the dust spread see below The licensed removal type work will be carried out first in the half with the NPU with the NPU unit on and dust suppression techniques used as normal Both the removal and clean up should be completed so the Contractor is happy with the area passing a visual assessment Then turn off the NPU and tape up the entrance to the middle barrier to seal the area and carry out removal and clean up in the unlicensed area This will mean no extraction or ventilation in most cases but normally the use of water sprays gel removers and steam units etc. should be used as we would expect these control measures to be used by anybody who removes asbestos under CAWR If separation into two areas with a physical barrier is not possible the sampling with NPU on and NPU off should be arranged with a lunch break or overnight gap between Polythene barrier oo Extract <+ __|NPU < flap entrance flap 3 stage airlock LICENSED WORK NPU on wy UNLICENSED WORK NPU off <q SAMPLING STRATEGY DURING WORK Use up to 3 samplers per person 1 for mass concentration and 2 for fibre concentration depends on number of workers The sampling personnel will have to apply a judgement on what sampling rate and time of sampling to use based on the expected amount of airborne dust Sample the two main work phases removal and clean separately by 23  Use a cowled sampler head with 0.8 ...m sampling minute for entire pore size filter set at between 0.2 - 0.5 period of removal and then change head for entire period of clean up fi Use a cowled sampler with 0.8 um cowl every 10 minutes during dusty pore size filter sampling at 1 minute and change periods or if lower concentration leave for longer The sampling person will have to judge this as best they can * Measure respirable dust on at least 1 e.g. 2.2 min for removal person using a cyclone sampler at the appropriate rate be fitted with a 1.2 period and then change over for the clean up The cyclone ...mpore size membrane filter to allow for PCM can reweighing counting after Measure total dust on 1 person using IOM inhalable sampler operating at 2 min for removal period and then change over for the clean period SAMPLING STRATEGY DURING CLEARANCE personnel will carry out stage 2 and 3 of the 248 in each part of the enclosure stage clearance test as documented in HSG licensed and unlicensed individually For each separate part ' The stage 2 visual clearance will note whether dust area The Contractor will not be and debris are visible inside the work adequately cleaned in either sectioanskbeudt atodectaarirlyedounottfeuratnhder clean if not found to be the amount and location of the debris seen photographs will be made of The stage 3 disturbance detailed in HSG 248 in sampling each half using a new broom will be carried out separately as of the enclosure when dry to collect 480 litres of air static membrane filter samplers onto licensed ' The area should be cleared first with NPU off a The full stage procedure for certificate of laboratory after the HSL clearance Results to breeofcocruwpaartdieodn twoilHl SbLe carried as usual by another ANALYSIS Quarter filter should be mounted for PCM examined analysis and counted by WHO rules 200 fovs Quarter filters should be carefully wicked in water when dry left overnight mounted for to remove calcium sulphate particles and examined PCM analysis and counted by WHO rules 200 fovs 24 Quarter filters should be prepared for TEM analysis and counted by ISO method for PCME fibres asbestos and asbestos fibres identified If lots of calcium sulphate present grids can be placed in a water washer for 60 minutes to dissolve fibres see appendix H ISO 10312 95 A quarter filter should be retained and stored Mass concentration filters should be weighed before and after sampling with 3 control blank filters REPORTING Individual site reports detailing the work and results will be produced by HSL 6.2 RESPONSE FROM ARCA Dear Gary Please find below the ARCA Technical Committee comments on the proposed further trials to tdeextteurrmeidnceoatthiengasppropriateness of the proposed method of removing asbestos containing The sites should be large enough so that removal of textured coating can take place during the entire sampling period This will allow the measurement data from the study to be assessed in terms of actual airborne fibre concentrations rather than in terms of airborne fibre concentrations weighted average The range of textured coatings removed during the first study was too limited to permit a full assessment of the likely risks associated with textured coating removal Any conclusions derived from the study results can therefore only be applied to the coating types and removal techniques observed All sites during further trials should include proper removal from concrete not removal of plasterboard and plaster that happens to have Artex on it No measurements were made during the first study to determine whether there had been spread of asbestos contamination to outside the enclosures and no measurements were made of airborne asbestos fibre concentrations at the location of demolished enclosures Robin Howies method of micro vacuuming to identify fibres that have left the enclosure and settled on surfaces should be employed after completion of jobs during further trials to assess whether fibres are present any The failure to address the potential for asbestos contamination generated by the removal of textured decorative coatings to spread into areas occupied by unprotected adults and children is a critical omission from the first study and should be addressed this time All work during the first study including enclosure construction was carried out trained and licensed contractors which will bias the results towards best pbryacetxipceerienTcheed proposal is to allow the work to be carried out by unlicensed contractors therefore the trials should assess the new further proposal by using unlicensed contractors study HSL were on site during the first to manage the work which will have ensured better than normal practice This will have biased the results towards best practice 25 and this casts doubt on the validity of the representative of likely world measurement results obtained as being of tests exposures This will also apply to the second series http://www.arcaweb.org.uk/ARCA A Permission for HSL to carry out further studies permission of the client therefore on removal sites will require the directly in order to obtain we would recommend that HSL contact our members sites at which to carry out further studies list of ARCA members can be found at members1024.asp cFoinnsaullltyawtiilolnthpeerniecoedssity to carry out the further trials result in the need to extend the Regards Steve Sadley 26 7 REFERENCES IF 2005/03 An Investigation into the airborne fibre releases during the removal of textured coating from Domestic Premises G.Revell HSE project report IF2005 IF2006 Airborne fibre concentration during the removal of asbestos containing textured decorative plasters and paints and the risk to workers G.Burdett Removal of chrysotile containing textured decorative coatings additional work report 1 - Site R G. Burdett and G Revell HSE Project report IF2006 IF2006 IF2006 Removal of chrysotile containing textured decorative coatings additional work report 2 Simulation tests G. Burdett and G Revell HSE Project report Removal of chrysotile containing textured decorative coatings additional work report 3 - Site Y G. Burdett HSE Project report Removal of chrysotile containing textured decorative coatings additional work report 4 - Site S G. Burdett HSE Project report IF2006 Removal of chrysotile containing textured decorative coatings additional work report 5 - Site B G. Burdett HSE Project report IF2006 Removal of chrysotile containing textured decorative coatings additional work report 6 - Site D G. Burdett HSE Project report CD205 Amendments of the Control of asbestos of work regulations 2002 Regulatory Impact Assessment HSE 2005 CAWR 2002 Control of asbestos at work regulations 2002 SI 2002/2675 The Stationary Office ISBN 0 7176 2382 3 EU Directive 2003 Protection of workers from the risks related to exposure to asbestos at work amending Council Directive EEC OJEU L97 2003 ERM MDHS 39/4 Asbestos fibres in air Sampling and evaluation by phase contrast microscopy PCM under the Control of Asbestos at Work Regulations HSE Books 1997 ISBN 0-7176-1113-2 MDHS14 Methods of Determination of Hazardous Materials General methods for and gravimetric analysis of respirable and inhalable dust HSE books sampling 7176-1749-1 February 2000 ISBN 0- HSG248 Asbestos The analyst's guide for sampling analysis and clearance HSE 01/05 ISBN 0-7176-2875-2 procedures 22