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FILE NAME Brakes BRK DATE 1977 June DOC BRK064 DOCUMENT DESCRIPTION Unpublished Conference Report - Monitored Asbestos Concentrations in CT av MONITORED ASBESTOS CONCENTRATIONS IN CONNECTICUT By L. Bruckman and R.A. Rubino paper 77-48.5 To be presented at the 70th annual meeting 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 a? 77-48.5 Abstract An ambient air asbestos survey was conducted during late 1975 and early promulgation 1976 to define the magnitude of the health hazard posed by airborne asbestos fibers in Connecticut prior to the of the State's propose asbes- tos air quality standard i.e. 30 mor 30,000 total asbestos fibers , average developed day A newly low volume particulate sampler which oper- ates continuously for days at an air sampling flow rate of 4 cfm equipped with special membrane filters was used to collect ambient TSP samples for sub- sequent chrysotile asbestos electron microscopic determination by the Batelle- Columbus Laboratories emissions Approximately 30 monitoring sites were selected locations included ty- pical monitoring urban sites removed from known sources of asbestos rural- background sites and stations contiguous to 4 industrial users of asbestos i.e. manufacturers of friction products insulated wire and cable ammmi- tion and molding compounds and 3 toll plazas situated at various points along Interstate Ambient chrysotile asbestos levels removed from asbestos sion sources in both urban and rural locations were below 10 ng asbestos concentrations above 30 mwere measured near each of emis. However the indus- asbestos trial users of asbestos Furthermore levels adjacent to the toll plazas were also elevated in the 10 mto 25 mrange implicating asbestos emissions from vehicle braking lining decomposition as a significant source of airborne asbestos fibers _i at 77-48.5 Introduction 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 greater than 95 with the amphibole forms of asbestos being of lesser significance Occupational asbestos fiber exposure has been known for some time to cause severe respiratory problems including lung cancer and a relatively rare form of cancer of the lining of the lung and stomach known as mesothelioma Recently the previously rare mesothelial malignancy has been linked to occupa- tional asbestos fiber exposur1-e9 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 After an extensive review the Connecticut DEP found EPA's asbestos regulation to be inadequate for the purposes of protecting public health in Connecticut and consequently developed its own asbestos regulation While EPA's asbestos regulation was written in rather general terms i.e. no visible emissions or application of best available control technology Connecticut proposed a numerical ambient air quality standard of 30 mor 30,000 total asbestos fibers per cubic meter of air sampled day average and a compatible mass emission standard of 24 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 standard the DEP conducted an ambient air asbestos survey along with a study of as- induced mesothelioma incidence in Connecticut The results of the health study indicated that Connecticut's mesothelioma incidence rate has exhibited a fold increase since 1940. This rapid rise in the State's mesothelioma incidence rate closely parallels Connecticut's rate of increase in cumulative asbestos 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 rural locales urban areas and stations situated contiguous to known sources of asbestos emissions e.g. industrial users of asbestos and toll plazas A newly developed low volume particulate sampler was used to collect samples for subsequent chrysotile asbestos determination by the Batelle bus 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 products which contain asbestos such as asbestos cement floor tile paper friction materials and textiles are the major sources of ambient airborne asbestos fibers in Connecticut accounting for approximately 10 tons of asbestos emissions each 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 77-48.5 under stress Chrysotile asbestos constitutes approximately 50 by weight of mos vehicle brake linings manufactured in the United States 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 fibrous substances however a significant percentage remain in the asbestos form Consequently it is possible that ambient asbestos levels contiguous to areas of extensive vehicle _ braking such as toll plazas may be significantly higher than background locations In Connecticut the erosion of vehicle brake linings and clutch facings is estimated to contribute an additional 2 tons of asbestos fibers into the ambient air annually Perhaps the largest potential future source of asbestos emissions in Connecticut will be the demolition of structures containing asbestos floor and ceiling tiles and which have been insulated and fire- proofed with asbestos material1s3 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 yourself home projects 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 fireproofing boilers pipes etc the cutting and sawing of 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 by the release of asbestos fibers from containing surface coatings which were applied indoors to walls ceilings exposed structural steel air ducts plenums return air spaces for insulating thermal and acoustic decorating and fireproofing purposes indoors As a result of such applications appreciable amounts of asbestos fibers may be released into the air indoors 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 concern. At least one state i.e. New Jersey has already drafted regulations for the purposes of controlling and prohibiting the future use of spray asbestos surface coatings NESHAPS prohibits the use of such contain- ing spray insulation and fireproofing materials outdoors recent to NESHAPS proposes to prohibit the future use of any type of spray coatings indoors ammendment asbestos Sampling Methodology Connecticut's proposed asbestos ambient air quality standard is based on a day average sampling period instead of the usual hour duration because a month averaging time is more manageable from a monitoring standpoint is also not sensitive to short pertubations in asbestos emissions yet still provides the public with a high degree of protection from the adverse health effects caused by excessive asbestos fiber exposure In order to determine com- pliance with such a standard a new type of low volume ambient particulate sampler which operates continuously for 30 days was developed 16,17 This low volume particulate sampler 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 is day sampling interval The vol produced measurement essentially arithmetic average for the entire day sampling period , con- fil- of the an 2 77-48.5 .. The vol is essentially a combination of parts taken from a conventional vol sampler and a stack sampling train see Figure ) The vol consists of modified vol shelter filter holder transition piece a temperature compensating dry gas meter and a vacuum pump The vol transition piece is used as the vol's filter holder The transition piece has been fitted with a specially designed stainless steel adapter plate and is connected to the dry gas meter with walled i.e. 0.5 inch inside diameter 0.75 inch outside diameter tygon tubing The dry gas meter is an American Meter AL250 which is temperature compensating at 60 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 measurement accuracy of 0.01 cubic feet per minute The power for the vol is supplied by an oiless Gast Rotary Vane Pump Model 0522 which delivers 200 CFH at a pressure of 5 inches of mercury The vol operates at an air sampling flow rate of 4 cfm or 1/10 of that used by a conventional vol sampler Therefore a vol filter collects approximately 2 to 3 times as much sample by weighats compared to that amount collectebdy a standard hour vol Thus the 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 vol the Connecticut Department of Environmental Protection located a vol and a vol on the roof of the State Office Building located in Hartford Connecticut Continuous TSP data were collected for a year period Monthly mean TSP concentrations obtained using the vol were on the average % greater than the arithmetic mean of 30 consecutive overlapping daily vol measurements for the 12 30- intervals day where 16,17 A detailed description of this test program is reported else- Membrane collection filters 8 x 10 Gelman Metricel GN 0.45... pore size nylon reinforced were used since the glass fibers in conventional fiber glass filters interfere with the analytical technique used to ascertain the asbestos content of air samples The chrysotile asbestos analysis was performed by the Columbus Laboratories using electron microscopy the accuracy of the method used to determine the asbestos content of the air samples was es- timated to be 50 baseodn the analysis of activated chrysotile asbestos sam- ples Analytical results are expressed in terms of mass of chrysotile asbes- , tos per cubic meter of air 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 ammunition and a manufacturer of molding compounds and 3 toll plazas situated at various points along the Connecticut Turnpike 1-95 Source 1 uses approximately 600 tons of asbestos per month in the manufacturer of asbestos containing friction and gaskets materials This source has over 1,000 point ventilation at mixing i.e. raw materials includ- a 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 Vol and Low Volume Vol Ambient TSP Samplers Tee Ce ets epee arnt aan RE re HuydwuinsAd{jaus 20414 > S| es MOL} }9fUy a 7 vol sunsy adald . dS (a J8|dw*IDS Inlet ~rhm (JOA-o}) pon swuNjJOA-Mo7} 72. 809 Aapjoyduing OUINJOA AugJ3{0/V Piece Transiton HujposadwyRecorde MO] , PUD Pump OutletFlow Pump2 MN aa JO|GWIDS (jOA Il) oN Volume OWINjOA | 1. hihi and Volume Volume -) ambient volume UOISUDIpa98Id BUINjoA-UBIHdwingd oinb) 4 77-48.5 Figure 2. Map Depicting Location of Asbestos Monitoring Sites > : CAMBAN pane NORFOLK femsmone | HARTLAND f i Bradley International Airport Tard fi" fl fi"fl fi"LANflD j caertae {nawrens -Sikorsky Memorial | Airport "A#Asbestos Monitoring Site number inside ellipse indicates num- ber of sites Figure 2. Map depicting location of asbestos monitoring sites . we. 77-48.5 ingasbestos 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 scrubber combinations estimated asbestos control efficiency 98-99 Source 2 uses approximately 3-6 tons of asbestos per month in the manufacturer of insulated wire and cable Asbestos is applied to wire and cable using carding 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 baghouse combinatiaonnd 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 chrysotile asbestos is blended with wood flour and parrafin material is then mixed in a steam heated ribbon blender and ammunition Here wax This blended 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 manufacturer 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 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 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 Asbestos 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 forming 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 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 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 mFor the 5 rural sites asbestos levels ranged from 1 mto 4 m For the 17 urban sites removed from known sources asbestos concentrations varied from 1 malmost half of the urban sites to 9 mHowever 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 exceeding the State's proposed 30 masbestos air quality standard i.e. 32 mat a Public Works building located near the friction products manufacturer 33 mat a Junior High School located adjacent to the insulated cable and wire and ammunition manufacturer combination 33 m 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 compliance with NESHAPS and other existing state and federal air quality regulations Ambient elevated in from vehicle asbestos levels adjacent to the 3 toll plazas on 95 the 10 mto 25 mrange implicating asbestos brake lining decomposition as a significant source of were also emissions airborne ' asbestos fibers see Figure 6 Asbestos concentrations at the rural toll plaza 11,000 cars eastbound lane 12,000 cars westbound lane were 10 meastbound lane and 14 mwestbound 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 eastbound lane 27,500 cars westbound land were 3 mAdministration Building south side of highway and 25 mwestbound lane The asbestos concentration at the other urban toll plaza 27,000 cars eastbound lane 28,000 cars westbound lane which is also located near one of the largest industrial users of asbestos in Connec- ticut was 41 mAdministration 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 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 day average values except the 41 mconcentration which was approximately a ; 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 measured values are difficult to explain if one only considers the frequency distribution of the winds during the appropriate sampling interval see Figures 3-6 This apparent sampling anomaly might have several explanations For example 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 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 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 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 77-48.5 Figure 3. Ambient Air Asbestos Survey 75-11 Asbestos Levels Near A Manufacturer of Friction Products Day Average | 0 87 oll %oO% SjaAa| AysoNS fy SOJEqSD PL OPA! UOHIG p4Od PULA aly eBpaep50 02. JO 20 | UOLNG4ysiq , spon id O62 092 ; Aouanbety Aeans w/BuVv ng g w/Bu % uoljoy 260 aHS* Jo DZDid JID 230 Buyduing904NOS [lO GN391 f- -fi: ov bu gf Ib Of jualquy 140 [+-UOpPOl4y Sikorsky Frequncy 2 AOuNOS Bjtu) / w/Bu Memorial At asbestos 17 asbestos | 77-48.5 Figure 4. Ambient Air Asbestos Survey 75-11 Asbestos Levels Near A Manufacturer of Ammunition and a Manufacturer of Insulated Wire and Cable Day Average N ys. cy AYS4OUIS HY UOHBIG 00d PUI Hlodary JO jouwaly| o0GE 2 cable JDOU Q1qD 008 oA ll SjOAS| PUD : Sikorsky oO Sikorsky PeJDINSU! . JO } 0 62 0 9d 002 a 50 80 D A@ANSPUD . 10 20 (uo}UNDEsk 1 0 BdunosUL)BY Qns9371 @fd4Nt0S Buyduos JO juaIquiy near surveysurvey , manufacture SOW asbestos levels wire levls cable and a us) e41M insulated wire and D 77-48.5 Figure 5. Ambient Air Asbestos Survey 76-2 Asbestos Levels Near A Manufacturer of Molding Compounds Day Average 10 -Afi| Aaiposg Ud!l}OaIG) Wind Direction piodsjy Airport PUIN JO 20 UOLINGfOUuo}IdU] oOSE SIG /2-9L/Z| spunodwo Aguanbs4 ASans Bbulpjow S2UWQL'O=,1 sojeqsp ou{B>u m o/bu so cere ng 9109S uu yt. 1> up M bl + lw aS jueiquy sounjosynupw Bu 0.76miles E survey BuryjduosBdunoS air survey asbestossurvey 26 asbestos survey asbestosmanufcture manufacture . p 170 : day average 77-48.5 Figure 6. Ambient Air Asbestos Survey 75-11 Asbestos Levels Near 3 Toll Plazas Along 95 Day Average 11 008 IoIO WO? AYSJONIS sjene| FY 00 UOHSNG 20 SOlseqD PUI sy [DJ 20SE JO LOWS] UOolNquysi :G2/bI-GZ/LIO] abpuap Adusenbl4 7 } % Ap -og __,oyu day pw/}BU ye Ol DZDid sOjoqsp Source (Avp/sip9QO'GS) Source [OL Sampling udqi SO PWD g6-| ES] =f . s8{D9S a11S 140 4D DZDid 13.7miles 13.7miles Sampling ou 13.7miles 20 {DINY BU {OL Sikorsky BOInNOS We Distrbuion Distribution Frequency At asbestos Frequncy air , Jo; asbestos levels asbestos asbestos alongalong survey 30- day along 30 speu 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 m indicating that the ambient asbestos problem is limited to populations residing 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 m day average i.e. 32 m- manufacturer of friction products 33 m- manufacturer of insulated wire and cable and manufacturer of ammunition ed approximately 1/2 mile apart 33 m- 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 variations in ambient as- bestos levels near these subject industrial users of asbestos well as other sources of asbestos emissions Ambient asbestos levels at 3 toll plazas situ- ated at various locations along 95 were all relatively elevated i.e. con- centrations varied between 10 mand 25 mimplicating vehicle brake lining decomposition as a significant source of airborne asbestos fibers The highest measured asbestos concentration i.e. 41 mfor 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 passing through a toll station and ambient asbestos levels data collected during the subject survey suggest a linear relationship The quantity of asbestos fiber the demolition of structures containing asbestos floor which have been insulated or fireproofed with asbestos dust released during and ceiling tile and materials should be - quantified as soon as possible Furthermore asbestos levels indoors should also be quantifieidn 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 decorating purposes Acknowledgements Bill Torrey and John Courcier Federal EPA - Region I for suppling NESHAP inspection reports Philip Menchel and Arthur Fitzgibbons Connecticut Department of Transportation for suppling traffic counts at the toll plazas along 95 Paul Norton Connecticut DEP Air Compliance Monitoring for preparing the necessary technical drawings Rosanna Veilleux Connecticut DEP Air Com- pliance Monitoring for her preparation of the manuscript Ed Hyne Connecticut DEP Air Compliance Monitoring for his expert assistance in conducting the subject survey 12 77-48.5 . References References 1. Biological Effects of Asbestos Proceedings of a Working Conference held at the International Agency for Research on Cancer Lyon France Oct. 1972 . M.L. Newhouse and H. Thompson following exposure to asbestos 261 1965 Mesothelioma in the London of pleura and peritoneum area Brit J. Ind Med I.J. Selikoff and E.C. Hammond Environmental epidemiology III Community effects of occupational environmental asbestos exposure Amer J. Publ Health 1658 1968 I.J. Selikoff E.C. Hammond and H. Heimann Critical Evaluation of Dis- ease Hazards Associated with Community Asbestos Air Pollution in H.M. Englund and W.T. Beery eds Proceedings of the Second International Clean Air Congress Academic Press New York 1971 I.J. Selikoff Arch Environ W.J. Nicholson and A.M. Health 25 1972 Langer Asbestos air pollution J. Lieben and H. Pistawka Mesothelioma and asbestos exposure Environ Health 559 1967 M.L. Newhouse and H. Thompson Epidemiology of mesothelial London area Ann N.Y. Acad Sci 579 1965 tumors in the J.C. Wagner C.A. Sleggs and asbestos exposure in Med 260 1960 and the P. Marchand Diffuse pleural north western Cape Province mesothelioma Brit J. Ind P. Champion Two cases of malignant mesothelioma after exposure to asbes- tos Am Rev. Resp Dis 821 1971 10 National emission standards for hazardous air pollutants asbestos beryllium and mercury Federal Register 38 66 April 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 1207 1975 13 L. Bruckman R.A. Rubino and B. Christine Asbestos and Mesothelioma In- cidence in Connecticut J. Air Cntr Assoc 121 1977 14 A.N. Rohl A.M. Langer M.S. Wolf and I. Weisman Asbestos Exposure During Brake Lining Maintenance and Repair Environ Res 110 1976 15 National Emission Standards for Hazardous Air Pollutants Proposed Amendments to Asbestos Standard Federal Register 42 March 2 1977. 13 77-48.5 16 L. Bruckman E. Hyne and P. Norton A Low Particulate Ambient Air Sampler paper presented at the Specialty Confernece Measurement Accuracy As it Relates to Regulation Compliance New Orleans LA Oct. 1975 27 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 TA Or TR SET E*I OREN aSaRCTOORSR- RES = Soma atin* gegen em Ho na emncme ee a INOS REN mR Cer : : ee