Document pe4Z71JKp0qGGKkkZy58975vj

FILE NAME: Phenolic Resins (PHR) DATE: 1977 DOC#: PHR002 DOCUMENT DESCRIPTION: Unpublished Report from Conference - Monitored Asbestos Concentrations in Connecticut f -MONITORED ASBESTOS CONCENTRATIONS IN CONNECTICUT By L. Bruckman1 and R.A. Rubino2 (paper #77-48.5) To be Dresented at the 70th annual meetinq of the Air Pollution Control Association', to be held in Toronto, Ontario, June 20-24, 1977 Principal Air Pollution Control Engineer Air Compliance Unit, Monitoring Section Connecticut Department of Environmental Protection Hartford, Connecticut 06115 Assistant Director Air Compliance Unit, Engineering Section Connecticut Department of Environmental Protection Hartford, Connecticut 06115 # 77-48.5 Abstract S ---------------* * ------------------- - .An ambient air asbestos survey' was conducted during late 1975 and early 1976 to define the magnitude of the health hazard posed by airborne asbestos fibers in Connecticut prior to the promulgation of the Staters propose asbes tos air quality standard (i.e.3 30 T\g/m3 or 30,000 total asbestos fibers/m3, 50-day average). A newly developed low volume particulate sampler3 which oper ates continuously for 30-aays at an air sampling flow rate of 4 cfm3 equipped with special membrane filters was used to collect ambient TSP samples for sub- seauent chrysotile asbestos electron microscopic determination by the Batelle- Columbus Laboratories. Approximately 30 monitoring sites were selected; locations included "ty pical" urban sites removed from known sources of asbestos emissions3 rural background sites and stations contiguous to 4 industrial users of asbestos (i.e.3 manufacturers of friction products3 insulated wire and cable, ammuni tion and molding compounds)- and 3 toll plazas situated at various points along Interstate-95. Ambient chrysotile asbestos levels removed from asbestos emis sion sources in both urban and rural locations were below 10 x\g/m3. However3 asbestos concentrations above 30 x\g/m3 were measured near each of the indus trial users of asbestos. Furthermore3 asbestos levels adjacent to the toll plazas were also elevated (in the 10 r\g/m3 to 25 ng/m3 range), implicating asbestos emissions from vehicle braking lining decomposition as a significant source of airborne asbestos fibers. ' 1 Introduction #77-48.5 . Asbestos, the general term used to describe a class of fibrous silicate minerals, is widely used in industry and construction. The principal variety of asbestos used in industry is the serpentine form known as chrysotile (great er than 95") with the amphibole forms of asbestos being of lesser significance. Occupational asbestos fiber exposure has been known for some time to cause se vere respiratory problems, including lung cancer and a relatively rare form of cancer of the lining of the lung and stomach, known as "mesothelioma". Recent ly, the previously rare mesothelial malignancy has been linked to non-occupa tional asbestos fiber exposure.1-9 In 1973 the Federal EPA, recognizing the need to control the emissions of asbestos fibers into the ambient air,- promulgated National Emission Standards For Hazardous Air Pollutants (asbestos, beryllium, and mercury).10 After an extensive review, the Connecticut DEP found EPA's asbestos regulation to be in adequate for the purposes of protecting public health in Connecticut and, con sequently, developed its own.asbestos regulation.11,12 While EPA's asbestos regulation was written in rather general terms (i.e., "no visible emissions or apnlication of best available control technology"), Connecticut proposed a nu merical ambient air quality standard of 30 ng/m3 or 30,000 total asbestos fi bers per cubic meter of air sampled, 30-day average, and a compatible mass emission standard of 24 g/day. In the judgement of the Connecticut DEP a "no visible emission" asbestos air quality standard does not provide the State's residents with an adequate degree of protection from this carcinogenic sub stance. ' In order to define the magnitude of the hazard posed by airborne asbestos fibers in Connecticut prior to the promulgation of the State's proposed stand ard the DEP conducted an ambient air asbestos survey along with a study of as bestos-induced mesothelioma incidence in Connecticut. The results of the health study indicated that Connecticut's mesothelioma incidence rate has exhibited a 10-fold increase since 1940. This rapid rise in the State's mesothelioma inci dence rate closely parallels Connecticut's rate of increase in cumulative asbes tos consumption. Approximately 90% of these mesothelioma cases did not have a trade where exposure to asbestos was a common feature. The results of this study are described elsewhere.13 The ambient air asbestos survey was conducted during 1975 at approximately 30 monitoring sites; locations included rural and semi-rural locales, urban areas, and stations situated contiguous to known sources of asbestos emissions (e.g., industrial users of asbestos and toll pla zas). A newly developed low volume particulate sampler was used to collect samples for subsequent chrysotile asbestos determination by the Bate!le-Colurnbus Laboratories. The following discussion presents the results of Connecti cut's ambient air asbestos survey. Sources of Airborne Asbestos Fibers in Connecticut The manufacture of nroducts which contain asbestos, such as asbestos ce ment, floor tile, paper, friction materials and textiles, are the major sources of ambient airborne asbestos fibers in Connecticut,- accounting for apDroximately 10 tons of asbestos emissions each year.12,13 Another-potentially significant source of airborne asbestos fibers is the erosion of vehicle brake linings and clutch facings and subsequent release of asbestos. Asbestos is used in vehicle brake linings to provide strength, heat resistance, and selective decomposition / under stress. Chrysotile asbestos constitutes approximately 50% (by weight) of mos*- vehicle brake linings manufactured in the United States.14 During braking the application of energy is so intense and the heat created so great that most of the asbestos fibers are converted to other non-fibrous substances, however, a significant percentage remain in the asbestos form. Consequently, it is pos sible that ambient asbestos levels contiguous to areas of extensive vehicle braking, such as toll plazas, may be significantly higher than background lo cations. In Connecticut, the erosion of vehicle brake linings and clutch fac ings is estimated to contribute an additional 2 tons of asbestos fibers into the ambient air annually.12 Perhaps the largest potential future source of as bestos emissions in Connecticut will be the demolition of structures containing asbestos floor and ceiling tiles and which have been insulated and/or fire proofed with asbestos materials.13 The health risk posed to the general population by asbestos fibers is not limited to either the indoor occupational environment or the outdoor ambient air. Many do-it-yourself home Drojects create asbestos dust due to the mixing of dry, loose asbestos with water and subsequent application of such mixtures for the purposes of insulating and/or fireproofing boilers, pipes, etci.., the cutting and sawing of asbestos-containing wallboard, ceiling and floor tile and the sanding of spackling compounds containing asbestos. Perhaps the more seri ous public health hazard posed at this time by excessive asbestos fiber exposure has been created b.y the release of asbestos fibers from asbestos-containing sur face coatings, which were applied indoors to walls, ceilings, exposed structural steel, air ducts, plenums, return air spaces for insulating (thermal and acous tic) decorating and fireproofing purposes indoors. As a result of such applica tions appreciable amounts of asbestos fibers may be released into the air in doors during the application, again as the surface coating deteriorates, and . finally, when the building is demolished. The asbestos fibers resulting from the spraying operation itself, as well as those released from the coating over a period of time due to its friable nature, are of primary public health con cern. At least one state (i.e., New Jersey) has already drafted regulations for the purooses of controlling and/or prohibiting the future use of spray-on asbestos surface coatings. NESHAPS prohibits the use of such asbestos-contain ing spray-on insulation and fireproofing materials outdoors;10a recent ammendment to NESHAPS proposes to prohibit the future use of any type of soray-on asbestos coatings indoors.15 ' /' Sampling Methodology Connecticut's proposed asbestos ambient air quality standard is based on a 30-day average sampling period instead of the usual 24-hour duration because a one-month averaging time is more manageable from a monitoring standpoint, is also not sensitive to short-term pertubations in asbestos emissions, yet still provides the public with a high degree of protection from the adverse health ef fects caused by excessive asbestos fiber exposure. In order to determine com pliance with such a standard a new type of low volume ambient particulate samp ler, which operates continuously for 30 days, was developed. 1G'>17 This low volume particulate sampler (lo-vol) was designed around the straints that it must use an air sampling flow rate low enough to prevent ter overloading and subsequent biasing of the sample toward the beginning 30-day sampling interval. The lo-vol produced measurement- is essentially arithmetic average for the entire 30-day sampling period. ' con fil of the an #77-48.5 The lo-vol is essentially a combination of parts taken from a conventional hi-vol sampler and a stack sampling train (see Figure 1)._ The lo-vol consists of a-modified hi-vol shelter, filter holder, transition piece, a temperature compensating dry gas meter and a vacuum pump. The hi-vol transition piece is .Used as the lo-vol's filter holder. The transition piece has been fitted witha specially designed stainless steel adapter plate and is connected to the dry gas meter with thick-walled (i.e., 0.5 inch inside diameter, 0.7b inch outside diameter) tygon tubing. The dry gas meter is an American Meter #AL250, which is temperature compensating at 50F and rated at 250 cubic feet per hour (CFH). The meter has been fitted with standard gas pipe connections sized to fit the tygon tubing. This meter provides an air sampling flow rate.measurement accur acy of 0.01 cubic feet per minute. The power for the lo-vol is supplied by an oil ess Gast Rotary Vane Pump Model #0522, which delivers 200 CFH at a pressure of 5 inches of mercury. The lo-vol operates at an air sampling flow rate of 4 cfm or 1/10 of that used by a conventional hi-vol sampler. Therefore, a lo-vol filter collects approximately 2 to 3 times as much sample, by weight,'as com pared to that amount collected by a standard 24-hour hi-vol. thus the lo-vol should provide a more accurate chemical characterization of the TSP, especially for those substances which are usually present in very low concentrations, such as asbestos. As a quality control check on the performance of the lo-vol the Connecticut Department of Environmental Protection co-located a lo-vol and a hi-vol on the roof of the State Office Building, located in Hartford, Connecticut. Continuous 1% TSP data were collected for a 1-year period. Monthly mean TSP concentrations obtained using the lo-vol were, on the average, greater than the arithmetic mean of 30 consecutive non-overlapping daily hi-vol measurements for the 12 30- day intervals. -A detailed description of this test program is reported else where.1617 - . Membrane collection filters (8" x 10", Gelman* Metricel GN-6, 0.45p pore size, non-nylon reinforced) were used since the glass fibers in conventional fi ber glass filters interfere with the analytical technique used to ascertain the asbestos content of air samples. The chrysotile asbestos analysis was performed by the Batelle-Columbus Laboratories using electron microscopy;18 the accuracy of the method used to determine the asbestos content of the air samples was es timated- to be 50%, based, on the analysis of activated chrysotile asbestos sam ples.15 Analytical results are expressed in terms of mass of chrysotile asbes tos per cubic meter of ain sampled. Sampling Locations ' Approximately 30 monitoring sites were selected (see Figure 2); locations included "typical" urban and rural background areas and stations contiguous to 4 manufacturing sources of asbestos emissions (i.e., a manufacturer of friction products, a manufacturer of insulating wire and cable, a manufacturer of ammun ition and a manufacturer of molding compounds) and 3 toll plazas situated at various points along the Connecticut Turnpike (1-95). Source #1 ses approximately 500 tons of'asbestos per month in the manu facturer of asbestos containing friction and gaskets materials. This source has over 1,000 point ventilation streams at mixing (i.e., raw materials includ- *Mention of commercial products or company name does not constitute endorsement by the Connecticut Department of Environmental Protection. 3 #77-48.5 Figure 1. High Volume (Hi-Vol) and Low Volume (Lo-Voi) Ambient TSP Samplers 4 ( sFaigmuprelersI.. High volume (hi--voi) and Low-Volume <Sampler low volume (lo-vol) ambient TSP "77-48.5 Figure 2. Map Depicting Location of Asbestos Monitoring Sites 5 MA Fmigounriteor2in.g Msaitpes.depicting location of asbestos #77-48.5 ing. .asbestos and other inert materials are compounded on various types of mixing devices), forming (i.e., compounds are formed into pads and various friction and gasket products) grinding and machining operations. These streams are combined into 20 final streams, each exhausting to the atmosphere through an air mover and a control device (i.e., 10 baghouses and 10 wet cyclone-venturi scrubber combinations;.estimated asbestos control efficiency 98-99%+). Source #2 uses approximately 3-6 tons of asbestos per month in the manu facturer of insulated wire and cable. Asbestos is applied to wire and cable using cardinq, taping and braiding machines. The carding machines vent to baghouses, each collecting exhaust from 2 machines. There are 3 sizes of braiders at this plant, sized according to the number of spindles in the braids. The small braider exhausts to a baghouse, then vents to the outside. The medium and large braiders are exhausted to a separate piece of control equipment and are vented inside the plant. The taping machine is controlled by a cyclone-baghouse combination' and also vents inside. All control equipment used here are esti mated to be 99%+ efficient in removing asbestos from waste streams. Source #3, which is located about 1/2 mile from source #2, uses approxi mately 40 tons of asbestos per month in the manufacturer of ammunition. Here, chrysotile asbestos is blended with wood flour and parrafin wax. This blended material is then mixed in a steam heated ribbon blender and stored in a silo for feeding into a Colton Tablet machine where the "wads" are formed into their fi nal shape. The blending operation is vented to a wet cyclone which'has an esti mated asbestos control efficiency of approximately 95%. Source #4 uses approximately 150 tons of asbestos per month in the manufac turer of molding compounds. One process involves the mixing of dry powdered phenolic resins with glass, asbestos and other additives. This mixture is then transferred to a shaping line where the dry resin mixture with added plasticizer is milled and compounded to a desired thickness. Then the sheet is pre-ground and carried by a vacuum line back to the area where it was originally mixed. There it is processed by sizing screens to a desired mesh size. Then a large batch is blended to maintain consistency and packaged for sale. Another process combines formaldehyde-phenol liquid resins with dry resins and various grades of asbestos. This mixture is kneaded, extruded, dried and sized. Large amounts are blended and packaged. The last process involves blending pulp, dry resins, asbestos and fillers and then forming a sheet on a cylinder paper machine. As bestos is added to the beater just before the pulp is dumped to the stock chest. The sheet can be of varying thickness up to 3/8". It is oven dried after form ing, then sized to sheets 4 ` x 5' and sold. In the first process the mixing tank, sizing screens and blender are exhausted to a baghouse. The sizine line has exhaust from the fluxing mill and the pre-grinder which is also collected in a baghouse. The 3 extrusion lines have sizers and driers exhausting to 3 separate baghouses. The 2 beaters where asbestos is added are hooded and also exhaust to a baghouse, which collects dust from the 3 loading chutes and kneaders used in the extrusion lines. All the baghouses are rated at a 99%+ asbestos removal efficiency.' 6 #77-48.5 Results and Discussion . Ambient chrysotile asbestos concentrations removed from significant point sources of asbestos emissions in both rural and urban locations were below 10 ng/m3. For the 5 rural sites asbestos levels ranged from <1 ng/m3 to 4 n9/m3For the 17 urban sites removed from known sources, asbestos concentrations varied from <1 ng/m3 (almost half of the urban sites) to 9 ng/TM3* However, asbestos levels at the monitoring sites located contiguous to certain indus trial users of asbestos in Connecticut were elevated with at least one site near each source exceedinq the State's proposed 30 ng/m3 asbestos air quality standard (i.e., 32 ng/m3 at a Public Works building located near the friction products manufacturer; 33 ng/m3 at a Junior High School located adjacent to the insulated cable and wire and ammunition manufacturer combination; 33 ng/m3 at a private home near the' molding compounds manufacturer - see Figures 3-5). It is noteworthy that each of the subject point sources are in compli ance with NESHAPS and other existing state and federal air quality regulations. Ambient asbestos levels adjacent to the 3 toll plazas on 1-95 were also elevated (in the 10 ng/m3 to 25 ng/m3 range), implicating asbestos emissions from vehicle brake lining decomposition as a significant source of airborne asbestos fibers (see Figure 6). Asbestos concentrations at the rural toll plaza (11,000 cars/day eastbound lane; 12,000 cars/day westbound lane) were 10 ng/m3 (eastbound lane) and 14 ng/m3 (westbound lane); there are no known industrial users of asbestos near this toll station. Asbestos levels at one 'of the urban toll plazas (28,000 cars/day eastbound lane; 27,500 cars/day west bound land) were 3 ng/m3 (Administration Building, south side of highway) and 25 ng/m3 (westbound lane). The asbestos concentration at the other urban toll plaza (27,000 cars/day eastbound lane; 28,000 cars/day^westbound lane), which is also located near one of the largest industrial users of asbestos in Connec ticut, was 41 ng/m3 (Administration Building, south side of highway); this was the highest concentration measured during the subject survey. The ratio of the maximum asbestos concentration measured at the first urban toll plaza to that at the rural toll station was approximately equal to the ratio of the number of cars/day passing through each toll plaza (i.e., 1.8 versus 2.3) during the sam pling interval. All of the aforementioned measured asbestos levels were 30-day average values, except the 41 ng/m3 concentration, which was approximately a 20-day average value (due to a sampler malfunction). , ' An attempt was made to select monitoring locations near the industrial users of asbestos in such a manner that the maximum impact of each point source would be measured during a given sampling period. However, certain of the mea sured values are difficult to explain if one only considers the frequency dis tribution of the winds during the appropriate sampling interval (see Figures 3-6). This apparent sampling anomaly might have several explanations. For ex ample, local meteorological conditions near each source might differ somewhat from those measured at either of the two national weather bureau stations loca ted in Connecticut. Also, the source-oriented monitoring sites were situated 1/2 mile of each source and, thus, measured asbestos concentrations could be significantly effected by fugitive asbestos emissions. Furthermore, since monitored levels are 30-day average values it is possible that a combination of wind speed and stability conditions associated with a certain wind direction might significantly effect asbestos concentrations over a 30-day period even if they occurred relatively infrequently. In any event, the close proximity of the monitoring sites which exhibited elevated asbestos levels to a particular industrial user of asbestos clearly implicates that source as the major contri bution to the measured concentration. 1 7 #77-48.5 Figure 3. Ambient Air Asbestos Survey, 10/17/75-11/14/75: Asbestos Levels Near A Manufacturer of Friction Products, 30-Day Average 8 N i Frequency Distribution Of Wind Direction At Sikorsky Memorial Airport Figure 3. Ambient air asbestos survey, 10/17/75-11/14/75= asbestos levels near a manufacturer of friction products, 30-day average. |i (D ro #77-48.5 Figure 4. Ambient Air Asbestos Survey, 10/17/75-11/14/75: Asbestos Levels Near A Manufacturer of Ammunition and a Manufactur of Insulated Wire and Cable, 30-Day Averag 9 Frequency Distribution Of Wind Direction At Sikorsky Memorial Airport NA 8 rjg /m3 A Scaie:l" =0.76mi!es Figure 4. Ambient air asbestos survey, 10/17/75-11/14/755 asbestos levels near a manufacturer of ammunition and a manufacturer of ' insulated wire and cable, 30-day average. #77-48.5 Figure 5. Ambient Air Asbestos Survey, 1/26/75-2/27/76: Asbestos Levels Near A Manufacturer of Molding Compounds, 30-Day Average 10 : l 'Me ,.rM Frequency Distribution Of Wind Direction At Bradley (\1 International Airport Source # 4 (mfg. molding compounds) 3 <1g g /m ' <} Arg/m3 4 /?g/m' p g /m: A14 og/m",, LEGEND $$ Source A Sampling Site '<1^r)g/m3 Scale: l" =0.76miles Figure 5. Ambient air asbestos survey,'1/26/76-2/27/76: asbestos ieveis near a manufacturer of molding compounds, 30-day average. Figure 6. Ambient Air Asbestos Survey, 10/17/75-11/14/75: Asbestos Levels Near 3 Toll Plazas Along 1-95, 30-Day Average 11 Rural Toil Plaza (2 3 ,0 0 0 -cars/day) S(moufgrc. efric#t1ion products) 1" a . lOrg/rn5 41 ng/m U(5rb5a,0n00TocllarsP/ldaazay) 3 rg/rrf U(5rb5a,n50T0ocllarPsl/adzaay) LEGEND i Source A Sampling Site Scale! 11,= I3.7miles Frequency Distribution Of Wind Direction At Sikorsky Memorial Airport Figure 6. Ambient air asbestos survey, I0 /I7 /7 5 -II/I4 /7 5 1 asbestos levels near 3 toll plazas along 1-95, 30-day average. #77-48.5 Conclusions and Recommendations ' Ambient asbestos levels in both rural and urban areas (removed from in dustrial users of asbestos) were relatively low (i.e., less than 10 qg/m3) indicating that the "ambient asbestos problem" is limited to populations re siding in close proximity to point sources of asbestos emissions. Ambient as bestos concentrations adjacent to several different industrial users of asbes tos exceeded Connecticut's proposed asbestos air quality standard of 30 qq/m3, 30-day average (i.e., 32 no/m3 - manufacturer of friction products; 33 qg/m3 manufacturer of insulated wire and cable and manufacturer of ammunitionlocat ed approximately 1/2 mile apart; 33 qg/m3 - manufacturer of molding compounds) in spite of the fact that each source was in compliance with NESHAPS and other current applicable state and federal air quality regulations. Additional mon itoring should be conducted to define month-to-month variations in ambient as bestos levels near these subject industrial users of asbestos,as well as other sources of asbestos emissions. Ambient asbestos levels at 3 toll plazas situ ated at various locations along 1-95 were all relatively elevated (i.e., con centrations varied between 10 qg/m3 and 25 qg/m3) implicating vehicle brake lining decomposition as a significant source of airborne asbestos fibers. The highest measured asbestos concentration (i.e., 41 qg/m3) for the entire survey was recorded at the monitoring site located adjacent to an urban toll station and one of the largest industrial users of asbestos in the State. Additional monitoring should be conducted near other toll plazas to better define the re lationship between the number of vehicles/day passing through a toll station and ambient asbestos levels; data collected during the subject survey supqest a linear relationship. The quantity of asbestos fiber dust'released during the demolition of structures containing asbestos floor and ceiling tile and/or which have been insulated or fireproofed with asbestos materials should be quantified as soon as possible. Furthermore, asbestos levels indoors should also be quantified in the near future, especially in buildings where asbestos surface coatings have been applied to walls, ceilings, exposed structural steel, air ducts, and plenums for insulating and/or decorating purposes. Acknowledgements Bill Torrey and John Courcier, Federal EPA - Region I for suppling NESHAP inspection reports; Philip Menchel and Arthur Fitzgibbons, "Connecticut Depart ment of Transportation for suppling traffic counts at the toll plazas along 1-95; Paul Norton, Connecticut DEP, Air Compliance, Monitoring for preparing the necessary technical drawinqs; Rosanna Veilleux, Connecticut DEP, Air Com pliance, Monitoring for her preparation of the manuscript; Ed Hyne, Connecti cut DEP, Air Compliance, Monitoring for his expert assistance in conducting the subject survey. 12 V #77-48.5 Terences _ , 1. 'Biological Effects of Asbestos at the International Agency for 1972. Proceedings Research on of a Working Conference held Cancer, Lyon, France, Oct. 2. M.L. Newhouse and H. Thompson, "Mesothelioma of pleura and peritoneum following exposure to asbestos in the London area," Brit. J. Ind. Med., 22:261 (1965). 3. I.J. Selikoff and E.C. Hammond, "Environmental epidemiology, III. Com munity effects of non-occupational environmental asbestos exposure, "Amer. J. Publ. Health 59:1658 (1968). 4. I.J. Selikoff, E.C. Hammond and H. Heimann, "Critical Evaluationof Dis ease Hazards Associated with Community Asbestos Air Pollution," in H.M. . ' Englund and W.T. Beery (eds.), Proceedings of the Second Clean Air Congress, Academic Press, New York 1971. International 5. I.J. Selikoff, W.J. Nicholson and A.M. Langer, "Asbestos air pollution," Arch, Environ. Health 25:1 (1972). 6. J. Lieben and H. Pistawka, "Mesothelioma and asbestos exposure,".Arch. . ' Environ. Health 14:559 (1967). 7. M.L. Newhouse and H. Thompson, "Epidemiology of mesothelial tumors in the London area," Ann. N.Y. Acad. Sci. 132:579 (1965). 8. J.C. Wagner, C.A. SI eggs and P. Marchand, "Diffuse pleural mesothelioma and asbestos exposure in the north western Cape Province," Brit. J. md. Med. 17:260 (1960). 9. P. Champion, "Two cases of malignant mesothelioma after exoosure to asbes tos," Am. Rev. Resp. Bis. 103:821 (1971). 10. "National emission standards for hazardous air pollutants (asbestos, beryl lium, and mercury)," Federal Register, 38 (66): (April'6, 1973). 11. L. Bruckman, The Environmental Impact of Asbestos in Connecticut, Internal report issued by the Connecticut Department of Environmental Protection, Air Compliance Unit, Engineering Section 12. L. Bruckman and R.A. Rubino, "Rationale behind a proposed asbestos air quality standard," J. Air Poll. Control Assoc. 25:1207 (1975). 13. L. Bruckman, R.A. Rubino and B. Christine, "Asbestos and Mesothelioma In cidence in Connecticut," J. Air Cntr. Assoc. 27:121 (1977). 14. A.N. Rohl, A.M. Langer, M.S. Wolf and I. Weisman, "Asbestos Exposure Dur ing Brake Lining Maintenance and Repair," Environ. Res. 12:110 (1976). 15. "National Emission Standards for Hazardous Air Pollutants; Proposed Amend ments to Asbestos Standard," Federal Register 42, (41):(March 2, 1977.) 13 #77-43.5 ^ H jTT L. Bruckman, E. Hyne and P. Norton, "A Low Particulate Ambient Air Samp ' ler," paper presented at the Specialty Confernece: Measurement Accuracy ,As it Relates to Regulation Compliance, New Orleans, LA. Oct. 1975. 17. L. Bruckman, E. Hyne and P. Norton, A Comparison of Low Volume and High Volume Sampling, Internal report issued by the Connecticut Department of Environmental Protection, Air Compliance Unit, Monitoring Section, 1976. 18. "Measurement of Asbestos in Ambient Air," Final Report, Contract #CPA70-92, U.S. Environmental Protection Agency, Research Triangle Park, N.C. 1970. 19. C.W. Melton, Personal Communication, February 13, 1975. 14