Document e5BoDq9GnXdEg3RrxeDeG4KZE

PLAINTIFFS EXHIBIT AL-1514 Odktf&z. Jol+Jz,q Am. Ind. Hyg. Assoc. J. 48(5):478-4S6 (1987) Asbestos Exposure During Renovation and Demolition of Asbestos-Cement Clad Buildings STEPHEN K. BROWN CS1RO Division of Building Research, P.O. Box 56, Highett, Victoria 3190, Australia External asbestos cement (AC) claddings become weathered after many years by the gradual loss ofcement from exposed surfaces; as a i loosely bound layers enriched with asbestos fibers are formed. This effect usually appears pronounced with roof cladding but slight with cladding. Asbestos fibers on such weathered surfaces may be mixtures of chrysolite with amosite or crocidolite. Renovation and den of old AC clad buildings could cause asbestos fiber emission, but this has not been investigated in the past. The exposure of worka asbestos dust during these operations and precautions to minimize exposure now have been investigated at several building sites. Asi dust concentrations during waterjet cleaning or painting of weathered AC roofing were approxiinately 0.1 to 0.2 fibers per milliliter(f/i Limited results suggest that concentrations may be reduced substantially by avoiding abrasion of surfaces. Concentrations during AC replacement averaged approximately 0.1 f/mL and were reduced markedly by employing more careful work procedures (e.g., by < handling of sheets or by wet stacking of sheets). Asbestos dust concentrations during demolition by removal of whole sheets averaged IJ 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 ek Suppression of asbestos emissions from roof sheets by wetting or sealing of weathered surfaces was not predictable because of the occu of asbestos 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 or abraded; 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 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 investigau to adequately provide a rational basis for decisions fl precautionary measures. This study aims to provide sue information by examining and analyzing weathered AC sM faces, by determining the exposure of workers to asbestt dust during typical work operations with weathered A products, and by investigating methods of suppressii asbestos emissions. Background . X $ Asbestos cement sheeting has been manufactured since 1901 when the first patents were granted,'3' 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 asbestc* plus lesser quantities of amosite or crocidolite (old cladding) to improve processability and product strength.'41 for which low hygiene standards are operative. The effect of weathering has been recognized in the United Kingdom with the Department of the Environment'2' 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 It was noted many years ago that a thin layer of asbesto* fibers becomes exposed with weathering on the surfaces d AC roofing, although this has little effect on mechanic*! properties.'3' A more recent study described a "fleece d fibers being laid bare on AC surfaces after natural weather ing for 8 to 12 years or alter artificial weathering with w** jets.'3' Another study found that a proportion of exposd jL chrysotile fibers had undergone degradation by surface re*tions associated with their high affinity for calcium hydro* Copyugm 19B7 Af***i*C inoustr.#* Hva-#n* Avv<v.itiu*> ALCOAO 000010155 ule ana cement nydration products. " Little is known of the behavior of amphlbole fibers during weathering. Amphibole fibers, however, d.o not form good bonds with cement particles'4' and are more chemically resistant than chrysolite 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.'7 91 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.'710 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.'13141 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 painting.`1516) 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 j|Df 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."'1 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 0.5 M 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 w here 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 S 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 SO 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 1 TABLE I Sltn Involved In Work Trials Sits Sits Dsscriptlon No. Building Age Extant of Surface Weathering 1 Garags. corrugated root 39 Severe 2 Private dwelling, corrugated root 30 Severe 3 Hall, corrugated roof 38 Severe 4 - Warehouse, corrugated root, part-painted 40 Moderate 5 Factory, corrugated roof 40 Very severe 6 Hail, corrugated roof, painted 29 - 7 Low-cost dwellings, corrugated roof 32 Severe 8 Warehouses: 8.1 Building A -- corrugated roof 40 Severe 8.2 Building B -- corrugated roof 40 Severe -- flat wall 40 Low 8.3 Building C -- corrugated roof 40 Severe -- flat wall 40 Low 84 Building 0 -- corrugated roof 40 Severe -- flat wall 40 Low 47) ALCOAO 000010156 tv'****** i .iiB roofing. Sheets were removed whole and carried indi vidually to the edge of roofs where they were either stacked (Sites 3, 5, 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,119' 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/m2. 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 stacked in the tray of the scissor lift. Again, comparative trials were made after pretreatment of sheet 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 25 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.122' The counting procedure generally used a Walton-Beckett eyepiece graticule (100 fields of 100 ^im diameter) but. when necessary, the full-viewing field (20 or 50 fields of 348 qm diameter) was employed to ensure a minimum count of 25 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.12" Counting by lull fields has been shown to lead to different counts from graticule fields.*23' 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 asbestc fibers -- a length to width ratio of 3 or greater, a lengt greater than 5 nm and a width less than 3 urn -- wer counted as required by standard methods.*20 211 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 1 and square ends (unless split): and 3" 2) amphibole-like: fibers from Classification I that were a 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.*25' In the present study, fibers were approximately sized during counting by visual comparison to graticule dimensions and later divided into suggested size classifications.*26' 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 ftm).*27' Results Charactaiiatlc* of Woaiharad Surfacaa 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 inTable 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 chrysotile and amosite. except for one surface where only chrysotile was present (Site I) and for two where chrysotile, amosite and crocidolite were all present (Sites 5 and 6). In compari- TABLE II Characteristics of Surface Layers From Weathered Roof Sheets Sample Surface Layer Fiber Content of Density (g/m') Layer (% w/w) A 240 B 340 C 110 D 190 32 25 22 24 ALCOA0000010157 jted luile deterioration with no significant surface layer but j isolated clumps of fibers usually identified as chrysolite, j Infrared spectra of bulk fibers extracted from wall sheets at I Site 8 showed that they contained predominantly chrysolite 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 lor chrysotile is 1.0 ij mL.'2*' For any mixture of these types of 1 asbestos the hygiene standard is 0.1 f/ mL; exposures deter1 mined in this investigation will be assessed relative to such a standard. Flbor 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.'21' Pickford'2*' suggests that I the lowest reliable detection limit (LR DL) 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 | 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 a/.'23' found that fiber counts can be increased by a factor of 1.5 for amosite and 2.5 for chrysotile by counting small graticule fields compared to full fields. This t 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 ai 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.12*' In the present work, ' both counting practices were employed for several samples - and the results are presented in Table HI. The ratios of concentrations derived from the two procedures have an . average value of 1.37 1 0.64 that -- while significantly differ ent from unity at the 5% level -- is similar to the ratio found 1 by Beckett et ai 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. | *hoot Cloonlng *" Asbestos concentrations during waterjet cleaning of roofing for several hours at two sites are presented in Table IV. The Comparative Counts for Walton-Beckett (WB) and Full (F) Fields Sample No. Count Reault* Flban Field* Ratio of Atbeitot Concentration* (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 305 30 F 6 14.0 100 WB 28.5 20 F 7 145 100 WB 39.5 20 F 8 16.5 100 WB 41.5 20 F 9 17 0 100 WB 48.0 80 F 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 1 91 0.97 0.76 1 53 1.20 0.90 0.97 3.36 1.15 0.77 1.83 098 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. Shoot 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 (approximately 0.01 f/ m L) 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 the job progressed while, at the other sites, planks ALCOAO 000010158 TABLE IV Asbestos Concentrations Naar Workara Claanlng AC Roofing With Watar Jats Sit* WorX Description No. Wind Sp**d (m/t*c) Sampl* Period (hr) Aaboatoa Concentration (f/mL) 1 Cleaning 40 m' ol roofing 2 Cleaning 45 m` of roofing 1.5 6.3 5.3 5.3 0.08 0.10 | 4 TABLE V Aaboatoa Concentration* Near Worker* Painting Weathered AC Sheeting Sit* Work Description No. Wind Speed (m/sec) Sampl* Period (hr) Asbeetoa Concentration (f/mL) 5 Painting 80 m* roofing by roller; 1.9 2.0 0.22 Painting 60 mJ roofing by roller 3.3 1.5 0.20, 0.12 8.1 Painting 300 m* 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 ml 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. Roof Rap/acamanf 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 S 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 -- 0.05 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 5 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 S. 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 time-weighted average (TW A )a 11 asbestos concentration for these trials was 0.21 f mL. This was reduced to0.03 f/ mL for trials where sheets were wetted when stacked, suggesting that much of the asbestos emission arising in the roof replacement process was associated with sheet stacking. ALCOAO 000010159 Asbestos concentrations during building demolition were mcasureu _ measured only for the period of sheet handling, and they are of workers' breathing zones to sheet handling and the con presented in Table VII. Sheet handling was continuous and sistent way in which surface dust was forced back at workers much more vigorous than for roof replacement work. Gen as they stacked sheets. erally. sheeting was removed at a rate of 100 m21 man-hr in demolition work as compared to 5 to 10 m3/ 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 Sequence 8.1) were 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 0.50 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 roof removal. made with roofing collapsed to waist height and, because of The ineffectiveness of wetting or sealing of sheet surfaces site restrictions, only a limited number of measurements in reducing asbestos concentration measurements in Trial could be made. Asbestos concentrations at two workers 8.3 was further investigated by considering other sources of _ sucking sheets were approximately 0.4 f/mL; at a worker asbestos emission. Much of the visible dust evolved during passing sheets across roofing, 0.1 f/mL. When the tops of sheet handling appeared to originate from dust accumulated sheets were hosed down prior to removal (Trial 8.1.2) much under sheet laps and ridge cappings. Samples of these were lower asbestos concentrations (less than 0.1 f/mL) were taken from Building Band Building C and were analyzed by . measured, even at a worker stacking sheets. When weath the method used for surface layer analysis described earlier, ered sheet surfaces were sealed with acrylic resin (Trial with additional quantification of chrysotile and amosite g. 1.3), there did not appear to be much suppression ofasbes tos emission compared to dry sheet removal, in contradic contents of dust by infrared spectroscopy (in accordance with absorptions at 3690 cm'1 and 780 cm'1, respectively, tion to the effect found with roof replacement at Site S. with calibration against LI ICC asbestos samples). Results of In Trials 8.2 and 8.3, all roofing was removed by two men these analyses are presented inTableVHl; these results show . in a scissor lift as described earlier, such that close handling that lap and ridge dusts of Building C contain substantial t and stacking of sheets in a confined area characterized their amounts of asbestos (predominantly as free fibers by visual work operation. The TWA asbestos concentration during assessment). This is consistent with the higher asbestos emis e* dry roof removal was determined to be of 0.38 f/ mL in trial sions observed at this site and the inability of surface treat -r group 8.2, and 0.60 f/mL in trial group 8.3. In both trial ments to control such emissions. a he TABLE VI -1S- Aabostoa Concentration* Naar Worker* Replacing so Weathered AC Roofing ile Site Work Description Wind Asbestos Concentration .:d. No. Speed (f/mL) led (m/sec) nA Range TWA" nd to 3 Replacing dry roofing 0.6-1.5 8 0.03-0.24 0.10 L-d 4 Replacing part-painted IV- rooting 3.3 2 0.03 0.03 >se 5 Replacing dry roofing 1.5-4.4 6 0.04-0.27 0.10 S Replacing lignin ulphonate-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 o:s-o.7 6 0.07-0.32 0.21 6 Romoving/replacing roofing with careful handling and wetting as stacked 0.9-1.5 8 ND' -0.07 0.03 7 Removing acrylic-sealed rooting 1.1-1.9 6 0.04-0.26 0.15 ALCOAO 000010160 TABLE VII Asbootoa Concentrations Nsar Worker* Demolishing AC Warshousos Trial Work Description No. Wind Speed (m/sec) Aabeatoa Concentration* (f/mL) nA Rang* TWA" 8.1 8.1.1 8.1.2 8.1.3 Building A demolished attar 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 trom lift: -- dry roof removal 1.3-3.5 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 2.5-35 4 0.04-0.12 0.07 8.3 -- acrylic-sealed wall removal 4.2 2 NDc-0.05 0.02 An - number of meesurements. "TWA * time-weighted average. CND - not detectable. TABLE VIII Analysis of Dusts Accumulated on AC Booting at Site S Sample Description Fiber Content Asbestos Content Alter Ashing (% w/w) of Root Dust (S w/w) Chrysotfl* Amoeite Building B, ridge dust Building B, lap dust Building C. ridge dust Building C, tap 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. Flbor Shape and S/za Dftfribuflon Fibers counted on sample filters 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 thanO.S pm diameter and 3 to 10 pm or 10 to 20 p long. Usually 40% to 60% of fibers counted were less than 0.5 pm diameter, and of these, 60% to 90% were long fibers with aspect ratios (ratio of length to diameter) of 40 or greater. Discuasion 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 Madieal 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 Materials in Buildings. London: Her Majesty's Stationery Office, 1983. pp. 1-33. 3. Department ot Scientific and Industrial Research: Weather ing Tests ot Asbestos-Cement Roofing 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. Hefde and R. Konig: Asbestos Emission from Asbestos-Cement and Floor Coverings. Staub-Reinhalt. Lutt 39:417-422 (1979). 5. Opocsky, 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. Weiss and H. Opiela: Asbestos Fiber Emis sions From Asbestos Cement Sheets. Staub-Reinhalt. Lutt 39:422-427 (1979). 9. Felbermayer, W. and M.B. Uaaar Environmental Pollution by Weathering of Asbestos Cement Sheets [Research Reportj. 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 of 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. 11:198212 (1976). 12. Building Research Establlahment "Control of Lichens, Moulds snd Similar Growths. Building Research Estab lishment Digest No. 139." Paper prepared at Princes 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. Chem. Assoc. 65:25-27 (1982). 14. Lohrer, W. and H.J. Pletrznink: Sources of Fibrous Dust -- A Survey. TIZ-Fachber. 107(2): 111-118(1983). 15. New Asbestos Sealing Process. Insul. 25(4):9 (1981). 16. Brown, S.K.: Fiber Release from Corrugated Asbestos Cement Cladding Due to Weathering and Cleaning. Highett, Victoria, Australia: CSIRO Division 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. Sa1.: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 19:21-30 (1981). 19. Armstrong, P.J- Evaluation ofLignon Sulphonate Liquor as a Dust Suppressant [Internal Report AIR 806/5 (unpub lished)]. Melbourne, Australia: Australian Road Research Board, 1961. 20. National Health and Medical Research Council: ' Mem brane Filter Method for Estimating Airborne Asbestos Dus: [Appendix 36).'' Paper approved by Eighty-Second Session of Council. Australian Department of Health, Canberra Australia. 1976. pp. 259-281. 21. Aabeetos International Association: "Reference Method fo: the Determination of Airborne Asbestos Fiber Concentra tions at Workplaces by Light Microscopy (Membrane Filte Method). 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-Taylor 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. 19:69-76 (1976). 24. Wylie, A.G.: Membrana Filter Method for Estimating Asbes tos Fiber Exposure. Definitions tor Asbestos and Othe Health Related Silicates jadited by B. Levadie (ASTM STf 834). Am. Soc. Test. Mater.: 105-117 (1984). 25. McDonald, A.D., J.S. Fry, A.J. Woolley and J.C. McOonalc Dust Exposure and Mortality in an American Chrysotii Asbestos Friction Products Plant. Brit. J. Ind. Med. 41:151 157(1984). 26. Pott, F,, W. Slober and K. Spumey: Properties of Asbestc and Other Fibrous Dusts With Regard to Their Carcinc genicity. In Aerosols in the Mining and Industrial Work Env ronments. Vol. 2. Characterization, edited by V.A. Marp and B.Y.H. Liu. Ann Arbor, Mich.: Ann Arbor Science Pul lishers, 1983. 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 ol Counc Commonwealth Department of Health, Canberra, Australia 1983. pp. 1-41. 29. Plcktord, G.: Private communication by phone and lette November 1985. 4 Oecembcr 1985; Revised 8 Nmcmbci I9Mi ALCOA0000010162