Document Ev5Lk2w51bbj3oRo6vDknVqQN

'2V.A, PL__ AINTIFF'S EXHIBIT ^AL-iSl4, OdksJrti Am. Ind. Hyg. Assoc. J. 48<}):47*-86 <1987) Asbestos Exposure During Renovation and Demolition of Asbestos-Cement Clad Buildings STEPHEN K. BROWN CS1RO Division of Building Research, P.0. Box 56. Highelt. Victoria JI90, Australia External asbestos cement (AC) claddings become weathered after many yean by the gradual ioaa of cement from exposed surfaces; as a i loosely bound layen enriched with asbestos flbenare formed. This effect usually appean pronounced with roof cladding but slight with a cladding. Asbestos fibers on such weathered surfaces may be mixtures of chrysotile with amosite or crocidolite. Renovation and den of old AC clad buildings could cause asbestos fiber emission, hut this has not been investigated in the past. The exposure of worts asbestos dust during these operations and precautions to minimise exposure now have been investigated at several building sites, i dust concentrations during waterjet cleaning or painting of weathered AC roofing were approximately 0.1 to 0.2 fibers per milliliter (f/1 Limited results suggest that concentrations may be reduced substantially by avoiding abrasion of surfaces. Concentrations during ACi replacement averaged approximately 0.1 f/mL and were reduced markedly by employing more cartful work procedures (<.{., by< handling of sheets or by wet stacking of sheets). Asbestos dust concentrations during demolition by removal of whole sheets averaged 0J 0.6 f/mL for roofs and less than 0.1 f/mL for walls, reflecting the significant differences in extent of weathering between these eh Suppression ofasbestos emissions from roofsheets by wetting or sealing of weathered surfaces was not predictable because of the occu ofasbestos fibers in dust trapped under sheet laps. Precautions such as respiratory protection and clothing decontamination are con be essential for the demolition of roofing containing amosite or crocidolite by the procedures investigated. Introduction Inhalation of asbestos fibers has been established as leading to specific physical disorders in workers -- notably asbestosis, lung cancer and mesothelioma. Accordingly, regulations have been laid down with the aim of reducing and control* ling worker exposure to asbestos dust to below specific exposure guides (hygiene standards). Also, Codes of Prac tice have been developed for work with asbestos products to minimize asbestos emissions and to specify worker protec tion where appropriate. Work with new asbestos cement (AC) products normally does not lead to unacceptable exposure to asbestos dust unless the products are cut. machined orabraded; such work operations should be carried out with guidance from accepted Codes of Practice.'1' It is usually considered that negligible asbestos concentrations evolve from typical han dling of AC products because the asbestos is bound securely into a cement matrix. The AC products that are exposed to weathering for long periods, however, undergo surface deg radation involving the loss of cement and the laying bare of asbestos fibers. This degradation may be significant for var ious work operations associated with AC clad buildings -- ' particularly where the products contain crocidolite or amosite for which low hygiene standards are operative. The effect of weathering has been recognized in the U nited Kingdom with the Department of the Environment12' noting that demolition and removal of old AC products could fall within asbestos regulations and have to be carried out by licensed asbestos removal professionals. Also, in recent years, such work in Australia often has been carried out using many of the precautions employed for removal of asbestos insulation, an operation that is well established as being hazardous and associated with asbestos concentn tions grossly exceeding hygiene standards unless stringei work precautions are maintained. The asbestos concentn tions evolved during removal and demolition of old A products, however, do not appear to have been investigaii to adequately provide a rational basis for decisions 8 precautionary measures. This study aims to provide sui information by examining and analyzing weathered AC * faces, by determining the exposure of workers to asbesti dust during typical work operations with weathered A products, and by investigating methods of suppressii asbestos emissions. ~ Background f Asbestos cement sheeting has been manufactured since 1901 when the first patents were granted,111 and it has been used extensively in Australia as roof and wall cladding und recently with the emergence of asbestos-free products. Asbestos cement claddings used mainly chrysotile asbesta* plus lesser quantities of amosite or crocidolite (old claddinpi to improve processability and product strength.14' It was noted many years ago that a thin layer of asbestos fibers becomes exposed with weathering on the surfaces* AC roofing, although this has little effect on mechanic*! properties.'3' A more recent study described a "fleece" * fibers being laid bare on AC surfaces after natural weather* ing for 8 to 12 years or after artificial weathering with wat jets.lSl Another study found that a proportion of expos** g. chrysotile fibers had undergone degradation by surface reac tions associated with their high affinity for calcium h>dro* Coflyngm 19B7 Am***cn iftduM'i*1 Hvq<a* Awyv.WMiun ALCOA0000010155 ide ana cement iteration products. Little is known of the behastor of amphibole fibers during weathering. Amphi' bole fibers, however. d.o not form good bonds with cement particles'*' and are more chemically resistant than chrysotile and might be expected to be more readily laid bare on weathered surfaces. It has been shown that asbestos fibers can be emitted from the weathered surfaces of AC claddings under the action of environmental forces, although only at very small ambient concentrations typical of those encountered in industrial cities.17'9' Asbestos concentrations during cutting or machin ing of weathered claddings are likely to be similar to those encountered with new products, generally exceeding hygiene standard concentrations unless precautions are taken.'71011' Other work operations, however, now arc encountered with weathered AC claddings and little is known of asbestos emissions arising from them. For example, weathering also is associated with the growth of dark lichens"2' that adhere tenaciously to weathered surfaces and usually require con siderable force to be removed; e.g. toxic washes, sweeping with stiff brooms, wet wire brushing and high-pressure water jet cleaning have been considered.'1314' Water jet cleaning has been found the most effective, and it is in use locally and in the United Kingdom to clean AC roofing prior to paint ing.113'19' Also, since vast quantities of AC cladding have been used over several decades with Australian buildings, there is increasing activity in cladding replacement andbuilding demolition operations. Work Operations A series of work trials was conducted for each of the work operations: sheet cleaning, sheet painting, roof replacement and building demolition. These operations involved build ings clad in AC sheeting with up to 40 years weathering jfrom several Melbourne suburbs, as described in Table I. For each building, sheeting surfaces were assessed for the extent ^of weathering and fiber exposure by close visual examina- lion; exposed fibers were sampled and identified by infrared spectroscopy in which procedures described by Coates were used."" In some cases surface layers were scraped from measured areas and weighed to determine surface layer den sity. Also the fibrous contents of the layers were determined by weight after extraction with 0.5M hydrochloric acid (brought to boil, then cooled), capture on a 750 jim screen and ashing for 10 min at 400C. Acid treatment of different asbestos types by this method has been found to yield 90% or more recovery."8' Since work trials were conducted outdoors under ambient conditions and with limited control on procedures employed, detailed measurements of ambient climate and observations of work procedures were made for each trial. 1) Sheet cleaning: roofs at Sites I and 2 with areas 30 and 45 m2, respectively, were cleaned with high-pressure water jets in trials taking several hours. These were commercial contracts where operators stood in upright positions on roofing and used water jet guns with extension lances to strip the weathered layer from sheeting. 2) Sheet painting: these were simulated trials in which badly weathered roofing (Sites 5 and 8) and lightly weathered walls (Site 8) were painted with a diluted acrylic coating(28% by weight solids content) by either roller or airless spray. Generally, areas of 50 to 400 m2 were coated in 1.5 to 4 hr. Operators worked from timber supports laid on roofing surfaces that were moved (sometimes by dragging) as work proceeded. 3) Roof replacement: old and badly weathered AC roof ing was replaced by steel roofing on large commercial buildings (Sites 3 to 5,7) or housing (Site 6) as normal building maintenance procedures. Roof replacement usually was carried out by two to six men, according to a sequence whereby small sections (20 to 40 m2) were repetitively unfastened, removed and replaced by new TABLE I SUM Involved In Work Trial* Sit* Site Description No. Building Age 1 Garage, corrugated root 2 Private dwelling, corrugated root 3 Hall, corrugated root 4 - Warehouse, corrugated root, part-painted 5 Factory, corrugated roof 6 Hall, corrugated roof, painted 7 Low-cost dwellings, corrugated roof a Warehouses: 8.1 Building A -- corrugated roof 8.2 Building B -- corrugated roof -- flat wall 8.3 Building C -- corrugated roof -- flat wall 8.4 Building D -- corrugated roof -- flat wall 39 30 38 40 40 29 32 40 40 40 40 40 40 . 0 Extent of Surface Weathering Severe Severe Severe Moderate Very severe Severe Severe Severe Low Severe Low Severe Low 47* ALCOA0000010156 ItM l roofing. Sheets were removed whole and carried indi vidually to the edge of roofs where they were either stacked (Sites 3, S, 7), dropped directly into a bin at ground level (Site 4). or passed and stacked into the tray of a truck (Site 6). After removal of large areas of roofing, the stacked sheets either were lifted from the building by crane (Site 5) or dropped individually into a dump bin at ground level (Sites 3, 7). Trials were conducted for 2 to 6 hr during which SO to 100 m2 of roofing was replaced. Comparative trials were made at some sites after pretreatment of sheet surfaces to sup press dust emission by coating with one of the following: i) lignin sulphonate liquor/191 a 10% by weight solids solution applied at a coverage of0.3 L/ m2; or ii) diluted acrylic resin, a 28% by weight solids solution applied at 0.3 L/m*. 4) Building demolition: several large (90 m 36 m) wool storage warehouses were demolished at Site 8. The first of these (8.1) was demolished by removing wall sheets and structural bracing and then collapsing the structure with roofing sheets intact. The roofing sheets sustained little damage and subsequently were removed by several workers who formed a chain across the roof and passed and dragged the sheets to each other and finally to two men stacking them on a platform up to chest height. Other warehouses were demolished by removing all cladding from the standing structure with workers confined to platforms adjacent to wall sheets or in scissor lifts set at a height such that roofing was at chest level. Work conditions were more confined in these trials and involved closer contact with weathered sheeting. Handling of roofing sheets was visibly dusty -- particularly as they were slacked in the tray of the scissor lift. Again, comparative trials were made after pretreatment ofsheet surfaces to suppress dust emission. Measurement of Asbestos Dust Concentrations Asbestos dust concentrations were measured by personal sampling within the breathing zones of workers using the NHMRC Standard Membrane Filler Method<20'and guide lines from the A1A Reference Method121' -- except that sampling was carried out with 13 mm filters at 80 mL/ min as well as 23 mm filters at I to 2 L/ min. Fibers were counted under positive phase contrast with microscopes capable of resolving the sixth set of lines on a National Physics Labora tory Mark II test slide, a process which is acceptable perform ance by Health and Safety Executive (HSE) standards.'22' The counting procedure generally used a Walton-Beckett eyepiece graticulc( 100 fields of 100 pm diameter) but. when necessary, the full-viewing field (20 or 30 fields of 348 ym diameter) was employed to ensure a minimum count of 23 fibers. This was done to achieve a minimum level of preci sion for fiber counts and not to increase the detection limit ol the procedure. Assuming a theoretical Poisson distribution, this procedure results in a coefficient of variation for counts of less than 0.20. although in practice greater variability typically is found.'21' Counting by lull fields has been shown to lead to different counts from graticule fields.123' and it i not a procedure employed in standard methods. The impli cation of this to the present results will be discussed. All fibers that met the geometric definition for asbesu fibers -- a length to width ratio of 3 or greater, a lengt greater than 3 ym and a width less than 3 ym -- wer counted as required by standard methods.'20'2" This approach has been criticized since it is not specific for asbestos fibers and may overestimate asbestos concentrations in environ ments containing other dusts.'24' For this reason, additional information was gathered on the shapes of fibers counted according to the following classifications: 1) asbestos-like: fibers with substantially parallel sides and square ends (unless split); and ' 2) amphibole-like: fibers from Classification I that were straight and needle-like in appearance. Such classifications were not used to identify or distin guish between different types of asbestos but to provide qualitative characterization of the dusts encountered. Further, recent evidence points to the importance of fiber dimensions to carcinogenic risk,'2*' and it has been suggested that size classification be undertaken during measurement of asbestos concentration.120' In the present study, fibers were approximately sized during counting by visual comparison to graticule dimensions and later divided into suggested size classifications.'20' This analysis can only be considered a limited characterization for each fiber population since the sizing is approximate and restricted to the range of fiber diameters visible by phase contrast microscopy (greater than approximately 0.2 ym).'27' Results Characteristic* of Woothond Surfaces Because of the ages of the buildings involved, the extent of surface deterioration of roofing usually was severe: each sheet presented a loose surface layer enriched in asbestos compared with the original product. Characterization of the surface layers from some roofing sheets by techniques de scribed earlier is presented in Table II. Fiber clumps sampled from roof surfaces provided infrared spectra that were free from interference by cement, which allowed ready identifica tion. Surface layers generally contained mixtures of chryso lite and amosite. except for one surface where only chrysolite was present (Site I) and for two where chrysotile. amosite and crocidolite were all present (Sites 3 and 6). In compari- TABLE II Characteristica ol Surface Layara From Weathered Root Sheets Sample Surface Layer Fiber Content ol Density (g/m') Layer (H w/w) A 240 8 340 C no D 190 32 25 22 24 ALCOA0000010157 lied liille deterioration with no significant surface layer but isolated clumps of fibers usually identified as chrysotile. infrared spectra of bulk fibers extracted from wall sheets at I Site 8 showed that they contained predominantly chrysotile and possibly a very small amount of amphibole asbestos. In general, the work operations described earlier involved con* tact with mixtures of chrysotile, amosite and crocidolite. The hygiene standard in Australia for the latter two types is 0.1 f/ mL averaged over a 4-hr sampling period while that for chrysotile is 1.0 f/mL/2*' For any mixture of these types of I asbestos the hygiene standard is 0.1 f/mL; exposures deter* 1 mined in this investigation will be assessed relative to such a . standard. Fiber Counting Practice As described earlier, this investigation employed counting of 100 Walton-Beckett graticule fields where possible, but changed to counting of 20 or SO full-fields so that at least 25 fibers were counted where fiber densities were low. Back ground counts for several unexposed filters were determined . also. These averaged 2,4 and 6 fibers, respectively, for the above procedures -- the first value being within the limit accepted in standard methods/2" Pickford(2s> suggests that the lowest reliable detection limit (LRDL) for sample count ing should be estimated from the upper confidence limit of the background count based on a lognormal distribution and assuming a coefficient of variation (cv) appropriate to the procedures employed. By assuming a cv of 0.4 for the j present case, it is estimated that the LRDLs at the 5% level ' are 7,14 and 21 fibers, respectively, for the above counting procedures. It can be seen that since a minimum count of 25 fibers was sought, the LRDL usually was exceeded; when a sample count was below the LRDL, the measurement was recorded as non-detectable. . Beckett et al.iW> found that fiber counts can be increased ' by a factor of I.S for amosite and 2.5 for chrysotile by counting small graticule fields compared to full fields. This i effect was attributed to human error in full-field counting, and with the employment of a more rigorous counting tech * nique (careful, prolonged scanning of whole field area), the factor for chrysotile counting was reduced to 1.14. Beckett et al. concluded that the two practices were comparable pro ' vided that full-field counts were carried out carefully and .. meticulously. It is believed that other laboratories have not ; been able to reproduce these findings/2*' In the present work, t both counting practices were employed for several samples and the results are presented in Table III. The ratios of concentrations derived from the two procedures have an . average value of 1.37 0.64 that -- while significantly differ ent from unity at the 5% level -- is similar to the ratio found ` by Beckett et al. when rigorous full-field counting was * employed. The above ratio was used to correct results based , on full-field counts to enable comparison with graticule field ' results. i Shoot Cleaning * Asbestos concentrations during waterjet cleaning of roofing for several hours at two sites are presented in Table IV. The Comparative Counts tor Walton-Beckett (WB) and Full (F) Fields Sample No. Count Results Fibers Fields Ratio ot Asbestos Concentrations (WB/F) 1 10.0 100 WB 52 0 50 F 2 11.5 100 WB 36.0 50 F 3 11 5 100 WB 28.0 20 F 4 12.5 100 WB 39.5 20 F s 13.0 100 WB 30.5 30 F 6 14.0 100 WB 28.5 20 F 1.15 1 91 0.97 0.76 1.53 1.20 7 14.5 100 WB 39.5 20 F S 16.5 100 WB 41.5 20 F 9 170 100 WB 48.0 80 F 0.90 0.97 3.36 10 23.0 160 WB 30.0 20 F 11 24.5 100 WB 38.0 10 F 12 25.5 110 WB 31.0 20 F 13 27.0 100 WB 93.5 28 F 14 28.5 100 WB 35.5 10 F 15 42.5 100 WB 52.5 20 F 16 84.0 100 WB 80.0 10 F 17 92.0 100 WB 129.5 20 F 1.15 0.77 1.83 0.98 1.00 1.95 1.23 1.71 Average 1.37 t 0.64 concentrations measured were 0.1 f/ mL or less for both cases. A notable problem with the procedure was observed to be containment of the removed layer that usually was propelled several meters from the building perimeter. This could comprise several kilograms of asbestos-rich material at the sites investigated (Table 1), and its dispersal around the grounds of a building could contribute to greater envi ronmental concentrations of asbestos at these sites. Shoal Pointing Limited measurements were made for this operation (Table V) since it involved only simulated trials. Results, however, do indicate the asbestos concentrations that may arise, and tentative suggestions will be made on procedures to reduce such emissions. In initial trials at Sites 5 and 8.1, asbestos concentrations were between 0.11 to 0.22 f/mL whether painting was by roller or airless spray. Considerably lower asbestos concentrations (approximately0.01 f/ mL) occurred at Site 8.3. The main difference in the work procedure at the latter site was that timber walk planks were lifted across roofing as thejob progressed while, at the other sites, planks ALCOA0000010158 TABLE IV Asbestos Concentrations Naar Workers Cleaning AC Booling With Water Jets Sit* Work Description No. Wind Speed (m/tec) Sample Period (hr) Asbeetoe Concentration (f/mL) 1 Cleaning 40 m' of roofing 2 Cleaning 45 ma of roofing 1.5 6.3 5.3 5.3 0.08 0.10 i TABLE V Asbestos Concentrations Near Workers Painting Weathered AC Sheeting She Work Description No. Wind Speed (m/sec) Sample Period (hr) Asbestos Concentration (f/mL) 5 Painting 80 mJ roofing by .roller; 1.9 2.0 0.22 Painting 60 m* roofing by roller 3.3 1.5 0.20. 0.12 6.1 Painting 300 ma roofing by airless spray; Painting 250 m' roofing by airless spray 2.8 4.3 3.4 3.1 0.14 0.11 8.3 Painting 400 ma roofing by airless spray; 1.7 2.3 0.01.0.01 Painting 110 m* wall by airless spray 2.0 0.4 0.09.0.12 were slid across roof surfaces. The lower mechanical distur bance of weathered surfaces may have contributed to lower emission of asbestos dust. At Site 8.3 where wall sheets were painted, there was no mechanical disturbance of the surfaces but concentrations of 0.09 and 0.12 f/mL were recorded, possibly because of the proximity of the workers* breathing zones to the surfaces as the surfaces were coated. Bool Bep/acemenf Asbestos concentrations near workers during replacement of weathered AC roofing at several sites are presented in Table VI. At Sites 3 to 5, these measurements were made during the full roof replacement process of unfastening, removal and disposal of old sheets and installation of new roofing. It is estimated that AC sheeting was handled for approximately one-third of this operation. At Sites 6 and 7, the measurements were restricted to the period of sheet handling to assess the effectiveness of control measures. Concentrations measured at Sites 3 and 5 ranged from 0.03 to 0.27 f/ mL and showed no correlation to sheet han dling rate or ambient wind speed. Limited measurements at Site 4 were considerably lower at 0.03 f/mL, possibly because the roofing was partly coated with deteriorated paint or because sheets were dropped from the building without stacking. The effect of coating weathered roof sur faces to suppress asbestos emission was investigated at Sites 5 and 7. In trials where the roofing had been pretreated with lignin sulphonate an asbestos concentration of 0.23 f/mL was measured during roof replacement. Another measure ment was 0.08 f/ mL, but it was rejected because the worker had relocated the sampler to the back of his neck. In a previous case, rain washed much of the treatment from the roof prior to the trial and the asbestos concentrations meas ured during roof replacement -- 0.03 and 0.11 f/ mL -- also were rejected. The treatment was considered neither suitable nor successful for dust suppression and thus was abandoned. In further trials at Site 3 roofing surfaces had been sealed with acrylic resin, effectively rebonding the surface layer, and asbestos concentrations were reduced markedly to 0.03 to 0.08 f/mL. Further measurements were made for sealed roofing at Site 7 but only during the process of sheet remov al; these results were considered comparable to those determined for sealed roofing at Site 3. At all of the above sites except Site 4, sheets were stacked during removal. Stacking was observed to create a surge of dust-laden air back across a worker as he dropped sheets. The effect of this on asbestos emission was investigated at Site 6 by stacking sheets with and without wetting. Without wetting, asbestos concentrations of 0.07 to 0.32 f, mL were observed, comparable to the range exhibited at other sites, with the higher concentrations having been measured for workers sucking sheets. The lime-weighted average (TWAf11 asbestos concentration for these trials was 0.21 (, mL. This was reduced to0.03 f/ mL for trials where sheets were welted when stacked, suggesting that much of the asbestos emission arising in the roof replacement process was associated with sheet stacking. ALCOA0000010159 Asbestos concentrations during building demolition were * measured only for the period of sheet handling, and they are presented in Table VII. Sheet handling was continuous and much more vigorous than for roof replacement work. Gen erally. sheeting was removed at a rate of 100 m2/ man-hr in demolition work as compared to 5 to 10 m2/ man-hr for the roof replacement process. Building demolition appeared to create considerably more visible dust emission and short sampling periods (30 to 60 min), were employed to limit particulate contamination on filters and to allow compara tive trials on the same day. The first series of measurements (Trial Sequence8.1) were made with roofing collapsed to waist height and, because of site restrictions, only a limited number of measurements could be made. Asbestos concentrations at two workers _ stacking sheets were approximately 0.4 f/mL; at a worker passing sheets across roofing, 0.1 f/mL. When the tops of sheets were hosed down prior to removal (Trial 8.1.2) much lower asbestos concentrations (less than 0.1 f/mL) were _ measured, even at a worker stacking sheets. When weatht ered sheet surfaces were sealed with acrylic resin (Trial 8.1.3), there did not appear to be much suppression ofasbes tos emission compared to dry sheet removal, in contradic tion to the effect found with roof replacement at Site 3. In Trials 8.2 and 8.3, all roofing was removed by two men . in a scissor lift as described earlier, such that close handling $ and stacking of sheets in a confined area characterized their - work operation. The TWA asbestos concentration during e- dry roof removal was determined to be of 0.38 f/ mL in trial ^r group 8.2, and 0.60 f/mL in trial group 8.3. In both trial measureu luiiluiumuous, of workers' breathing zones to sheet handling and me con sistent way in which surface dust was forced back at workers as they stacked sheets. When roof sheets were hosed prior to removal, lower asbestos concentration measurements were found at one site (Trial 8.2) but not the other (Trial 8.3, TWA concentration 0.30 f/ mL). Also concentrations measured when removing roof sheets that had been sealed with acrylic resin were comparable (Trial 8.3, TWA concentration 0.55 f/mL) to concentrations measured during dry root removal. The ineffectiveness of wetting or sealing of sheet surfaces in reducing asbestos concentration measurements in Trial 8.3 was further investigated by considering other sources of asbestos emission. Much of the visible dust evolved during sheet handling appeared to originate from dust accumulated under sheet laps and ridge cappings. Samples of these were taken from Building B and Building C and were analyzed by the method used for surface layer analysis described earlier, with additional quantification of chrysolite and amosite contents of dust by infrared spectroscopy (in accordance with absorptions at 3690 cm'1 and 780 cm1, respectively, with calibration against l) ICC asbestos samples). Results of these analyses are presented in Table V111; these results show that lap and ridge dusts of Building C contain substantial amounts of asbestos (predominantly as free fibers by visual assessment). This is consistent with the higher asbestos emis sions observed at this site and the inability of surface treat ments to control such emissions. TABLE VI AsbMtoe Concentrations Near Workers Replacing Weathered AC Rooting Site Work Description No. Wind Speed (m/eec) Asbestos Concentration (f/mL) nA Range TWA* 3 Replacing dry roofing 0.6-1.5 8 0.03-0.24 0.10 4 Replacing part-painted rooting 3.3 Z 0.03 0.03 S Replacing dry roofing 1.5-4.4 8 0.04-0.27 0.10 5 Replacing lignin sulphonate-treated roofing 1.1 1 0.23 . . 5 Replacing acrylic-sealed roofing 1.1-4.0 8 0.03-0.08 0.05 6 Removing dry roofing 0:5-0.7 6 0.07-0.32 0.21 6 Removing/replacing roofing with careful handling and wetting aa stacked 0.9-1.5 8 NO1-0.07 0.03 7 Removing acrylic-sealed rooting 1.1-1.9 6 0.04-0.26 0.15 ALCOA0000010160 TABLE VII Asbestos Concentration! Nnr Worker* Demolishing AC Warehouses Trial Work Description No. Wind Speed (m/sec) Asbestos Concentrations (f/mL) nA Range TWA" 8.1 8.1.1 8.1.2 8.1.3 Building A demolished alter collapse: -- dry roof removal -- wet root removal -- acrylic-sealed root removal 6.4 3.7 5.2 3 0.10-0.47 0.32 2 0.05-0.06 0.06 3 0.11-0.32 0.16 8.2 Building B demolished from lift: -- dry roof removal 1.3-3.S 6 0.30-0.53 0.38 -- wet roof removal 1.6 2 0.10-0.13 0.12 8.3 Building C demolished from lift: -- dry roof removal 1.6-4.9 10 0.34-1.1 0.60 -- wet roof removal 1.6-2.7 4 0.29-0.68 0.50 -- acrylic-sealed roof removal 3.1 4 0.41-0.76 0.55 83/8.4 -- dry wall removal 2.S-3.5 4 0.04-0.12 0.07 8.3 -- acrylic-sealed wall removal 4.2 2 NDc-0.05 0.02 *n = number of meaaurementt. "TWA * time-weighted average. CND 1 not detectable. TABLE VIII Analyeis of Duate Accumulated on AC Roofing at Site > Sample Description Fiber Content Asbestos Content Alter Ashing (W w/w) of Roof Dust (* w/w) Chrysolite Amoeite Building B, ridge dust Building B, lap dust Building C, ridge dust Building C, lap dust 1 Building C, lap dust 2 <0.03 <0.3 0.6 7.4 1.8 0.006 0.03 0.2 3.7 0.7 0.003 0.008 0.2 0.9 0.4 Asbestos concentrations near workers removing untreated AC wall sheets (Trials 8.3 and 8.4) were considerably lower than found with removal of roof sheets -- even during sheet stacking -- with a TWA concentration of0.07 f/mL. Asbes tos concentrations at workers removing wall sheets sealed with acrylic resin (Trial 8.3) were also low. These limited results suggest that asbestos emissions during work with the wall sheets will be small, possibly because of the low extent of surface weathering and dust accumulation that occur on such sheets. Fiber Shape and Sire attribution Fibers counted on sample niters were classified by shape in accordance with the criteria described earlier. For most work operations, 60% to 90% of fibers counted were classi fied as asbestos-like and 30% to 60% as amphibole-like. It is considered that these proportions are consistent with the emission of asbestos fibers from the weathered sheeting rather than emission of other material meeting the fiber counting criteria'of the Membrane Filter Method. Classification of counted fibers into approximate size categories also was carried out as described earlier. For nearly all counts, the most prevalent size classifications were fibers less than 0.5 pm diameter and 5 to 10 pm or 10 to 20 p long. Usually 40% to 60% offibers counted were less than0.5 pm diameter, and ofthese, 60% to 90% were long fibers with aspect ratios (ratio of length to diameter) of 40 or greater. Discussion Measurements made in this investigation indicate that sev eral work operations with weathered AC claddings are asso ciated with measurable concentrations of asbestos near workers, even though the operations are conducted out doors. Asbestos emissions appear to be higher for those operations associated with physical disturbance of surfaces and trapped dust, suggesting that work modifications to minimize such disturbance should reduce exposure to asbes tos dust markedly. Stacking of sheets without wetting appears to be the most severe process causing asbestos dust ALCOA0000010161 should be effective for AC roof demolition but, if inappro priate, it will be essential to employ respiratory protection for workers. Roof demolition work also caused marked con tamination of clothing with asbestos, and it is considered that appropriate protective clothing and decontamination prac tice will be necessary for such work. References 1. National Health and Medical Research Council: "Report on the Health Hazards of Asbestos. Appendix 8. Code of Prac tice -- Working With Asbestos Cement (Fibrocement) Building Materials." Paper prepared by the Asbestos Adhoc Subcommittee, adopted at the Ninety-First Session of the Council. Australian Government .Publishing Service, Canberra. Australia. 1982. pp. 51-55. 2. Department of the Environment Asbestos Maferisls in Buildings. London: Her Majesty's Stationery Office. 1983. pp. 1-33. 3. Department of Scientific and Industrial Research: Weather ing Tests of Asbestos-Cement Rooting Materials by F.E. Jones (Building Research Technical Paper No. 29). London: His Majesty's Stationery Office, 1947. pp. 5-39. 4. Lohrer, W., H. Helde and R. Konig: Asbestos Emission from Asbestos-Cement and Floor Coverings. Staub-Reinhait. Luft 39:417-422 (1979). 5. Opocaky, L. and L. Pentek: Investigation of the 'Corrosion' of Asbestos Fibers in Asbestos Cement Sheets Weathered for Long Times. In RILEM Symposium on Fiber Reinforced Cement and Concrete, edited by A. Neville. Lancaster, Great Britain: Construction Press, 1975. pp. 269-276. 6. Hodgson, A.A.: Fibrous Silicates (Lecture Series No. 4). London: Royal Institute of Chemistry, 1965. pp. 1-46. 7. Nicholson, W.J.: Chrysolite Asbestos in Air Samples Col lected in Puerto Rico (Report No. CPSC 77128000). New York: Environmental Sciences Laboratory/Mt. Sinai School of Medicine, 1978. pp. 1-56. 8. Spumey, K., G. Weisa and H. Opiela: Asbestos Fiber Emis sions From Asbestos Cement Sheets. Staub-Reinhalt. Lutt 39:422-427 (1979). 9. Felbermayer, W. and M.B. Uaaan Environmental Pollution by Weathanng of Asbestos Cement Sheets (Research Report]. Austria: Institute for Environmental Protection and Clean Air [A-8700 Leoben, Franz-Josef-Strabe 18). 1980. 10. Department of the Environment: Precautions on the Use oI Asbestos in the Construction Industry [A Report by the Subcommittee of the Joint Advisory Committee on Safety and Health in the Construction Industries]. London: Her Majesty's Stationery Office. 1974. 11. Bell, A^ Industrial Hygiene and Occupational Health Stud ies in Australian (NSW) Shipyards. Environ. Res. 77:198 212 (1976). 12. Budding Research Establishment "Control of Lichens, Moulds and Similar Growths. Building Research Estab lishment Digest No. 139." Paper prepared at Princas Risborough Laboratory and Building Research Station, Great Britain. London. Her Majesty's Stationery Office, 1982. 13. Whltely, P. and A.F. Bravery; Masonry Paints and Cleaning Methods for Walls Affected by Organic Growth. J. Oil Col. Cham. Assoc. 65:25-27 (1962). 14. Lohrer, W. and H.J. Ptetrsnink: Sources of Fibrous Oust -- A Survey. TlZ-Fechber. 107(2j:111-118 (1983). 15. New Asbestos Sealing Process. Insul. 25(4) 9 (1981). 16. Brown, S.X.: Fiber Release from Corrugated Asbestos Cement Cladding Dua to Weathering and Claaning. Highett. Victoria, Australia: CSIRO Oivision of Building Research Report/Division of Building Research, 1982. pp. 1-35. 17. Coates, J.P.: The Infrared Analysis of Quartz and Asbestos. Int. Environ. Sa/.:18-21 (April 1978). 18. Forbes, D.G. and G.W. White: The Identification of Bulk Asbestos and Monitoring of Airborne Fiber. Part I. Identifi cation. J. Assoc. Publ. Analysts 79:21-30 (1981). 19. Armstrong, P.J- Evaluation of Lignon Sulphonate Liquor as a Dust Suppressant (Internal Report AIR 806/5 (unpub lished)). Melbourne, Australia: Australian Road Research Board, 1981. 20. National Health and Medical Research Council: "Mem brane Filter Method for Estimating Airborne Asbestos Oust [Appendix 36).'' Paper approved by Eighty-Second Session of Council. Australian Department of Health, Canberra Australia, 1976. pp. 259-2B1. 21. Asbestos International Association: "Reference Method for the Determination of Airborne Asbestos Fiber Concentra tions at Workplaces by Light Microscopy (Membrane FilteMethod). Recommended Technical Method No. 1." Pape' prepared by the Dust Measurement Advisory Panel of the Asbestos International Association, AIA Health and Safety Publication, London, 1979. 22. La Guen, J.M.M,, T.L. Ogden, T. Shenton-Taytor and J.F Verrill: The HSE/NPL Phase Contrast Test Slide. Ann Occup. Hyg. 28:237-247 (1984). 23. Beckett, S.T., R.K. Hey, R. Hirst, R.D. Hunt, J.L. Jarvis anc A.L. Rickards: A Comparison of Airborne Asbestos Fibe Counting With and Without an Eyepiece Graticule. Ann Occup. Hyg. 79:69-76 (1976). 24. Wylie, A.G.: Membrane Filter Method lor Estimeting Asbes tos Fiber Exposure. Definitions lor Asbestos and Othe Health Related Silicatesedited by B. Levadie (ASTM STJ 834). Am. Soc. Test. Mater.: 105-117 (1984). 25. McDonald, A.D., J.S. Fry, A.J. Woolley and J.C. McOonale Dust Exposure and Mortality in an American Chrysotii Asbestos Friction Products Plant. Brit. J. Ind. Mad. 47:151 157 (1984). 26. Pott, F,, W. Stober and K. Spumey: Properties of Asbestc and Other Fibrous Dusts With Regard to Their Carcmc genieity. In Aeroaols in the Mining and Industrial Work Em, ronments. VoI. 2. Characterisation, edited by V.A. Marp and B.Y.H. Liu. Ann Arbor, Mich.: Ann Arbor Science Pul Ushers. 1963. pp. 585-592. 27. Rooker, SJ., N.P. Vaughan and J.M. Le Guen: On the Vi ibility of Fibers by Phase Contrast Microscopy. Am. Ini Hyg. Assoc. J. 43:505-515 (1982). 28. National Health and Medical Research Council: "Approve Occupational Health Guide: Threshold Limit Values (198: 84).'' Text adopted at the Ninety-Sixth Session of Counc> Commonwealth Department of Health. Canberra, Australi. 1983. pp. 1-41. 29. Plcktord, G.: Private communication by phone and lette November 1985. 4 December 1965: Revised* N'mcmhcr I9M ALCOA0000010162