Document M4NrMJzmnbrwKDXOb1kQZDG57

V- Report on INDUSTRIAL HYGIENE SURVEY OF SELECTED PLANT OPERATIONS PPG INDUSTRIES Pittsburgh-Corninc Corporation Port AlleganyPennsylvania August 27-28, 1963 By Morton Corn, Ph.D. ^rlbuJ' & ^ --r. * . TAELE OF CONTENTS I. II. III. IV. V. INTRODUCTION ' SUMMARY AND RECOMMENDATIONS THRESHOLD LIMIT VALUES OF SUBSTANCESMEASURED IN THIS SURVEY DESCRIPTION OF SAMPLING ANDANALYTICAL METHODS RESULTS AND DISCUSSION 1 1 2 2 4 I* I. INTRODUCTION A survey of airborne dust concentrations was performed in the Unibestos area of the Pittsburgh-Ccrning Port Allegany plant on August 27-28 by Dr. Morton Corn. The survey was performed at the request of Lee Grant, M.D., Medical Director, PPG Industries. The survey was aimed specifically at assessing the degree of dust control achieved ih the Unibestos facility with the improvements made since the former survey by the author in April, 1966. Also, because a nev assessment technique for asbestos fibers (Membrane filter} is now beir.c used, the present survey was performed by simultaneously sampling at the same location with the traditional sampling instrument (midget irr.pincer) and the new instrument. During the period of the survey outdoor weather conditions were clear, c:ii, and sunny, with outdoor temperatures m the range 6C-75CF. It should be noted that the dust collection system in the 'Jnioestos facility was thoroughly cleaned during t.-.e veer, prior to this survey. Therefore, it car. be reasonably assumed that.dust concentrations measured in this survey are representative of the lowest ccr.ce: orations wnich can be achieved with the present dust control system. II. SUMMARY AND RECOMMENDATIONS This survey was performed by simultaneously sampling airborne dust in the Unibestos plant by' two different techniques. Results of both methods of assessment suggest that dust concentrations in the plant are high when judged by the present U. S. Threshold Limit Value for asbestos dust, or by the recently proposed British guidelines for asbestos dust. Because the dust collection syrtem was operating at, or close to the maximum efficiency achievable with present facilities, modifications and additions to the present system would appear to be in order. It is beyond the scope of tV.is report to present detailed recommendations for system modification, but certain obvious major sources of dust emission in the plant as cited in Section V of this report. ~ It is recommended that attention be focussed on major redesign of the present system. It is obvious that additional air capacity for new local exhaust hoods will be necessary, and that this capacity probably' cannot be found in the present system, which was not adequately handling existing ho% ods. III. THRESHOLD LIMIT VALUE OF ASEESTOS DUST "The threshold limit values refer to airborne concentrations of substances and represent conditions under which it is believed that nearly all workers may be repeatedly exposed, day after day, without adverse effect. Because of wide variation in individual susceptibility exposures o: an occasional individual at or even below the threshold limit may not prevent, discomfort, aggravation of a pre-existing condition, ;r occupational illness. "Threshold limits sr.ould be used as guides in the control of health hazards and should nut be regarded as fin* lines between safe and dangerous conditions."* The American Conference of Governmental Industrial Hygienists had, in 1967, a T.L.V. for asbestos of 5 million particles per cubic foot, as determined by impinger sampling and counting by light-field technics-~s. In a considered revision (IStS), the Conference endorsed the retention c this T.L.V. for "most forms of asbestos". However, for crccicolite, because cf the production of mesotheliomas, it was recommenced that workers be equipped with air-supplied helmets because "no safe limit can be established fcr this form cf asbestos at this time." The Entish Occupational Hyciene society recently issued hygienic standards for chrysctile usoestcs dust.** The standards are based on the objective that the risk cf contracting asbestos be reduced to 1 per cent cf these who have a lifetime's exposure tc the dust. By "asbestosis" the committee meant the earliest demonstrable effects on the lur.a cue to asbestos. These standards are cited here because they are mere stringent than the U.S. guideline referred tc above. The exposure guidelines are: TABLE I EF.ITISK HYGIENIC GUIDELINES FCR ASBESTOS DUST DCS. CAi LZZ C2'* Fibers/or" AVI .'-`-vChi--*' ---w ^*Tw" Eh. --"1 .i.J^oiDwMPP'T* * * Neclicible Low Mediur. Hicr. 0 - 0.4 0.5 - 1.9 2.0 - iO ever 1C 0.C11 0.014 - C.0S4 C.C5- - C.2S ever u.2S * Extracted from tne Preface, Threshcld Limit Values for _?66. American Conference of Governmental Industrial Hygienists, IT.4 Broadway, Cincinnati, Ohio *55202 . * Ann. Occur-. Hvc. 21 , 47-69 (156) . *** Million particles"per cubic foot(as fibers). -2- The concentrations refer to fibers greater than 5 microns in length as determined by the membrane filter method. IV. DESCRIPTION OF SAMPLING AND ANALYTICAL METHODS Because of the current state of evaluation of the methods of assessing the potential hazard of asbestos dust, the standard impinger technicue and the membrane filter technique were used in this survey. A. Impinger Metr.od A midget impinger containing 10 nl of demineralized, distilled water was operated at 0.1 cfm air flow rate by means of a battery operated pump. artles were agitated prior to withdrawing drops of suspension for examination ir. a Spencer Brightline Haemocytoneter Cell. Particles were counted by viewing the sample with an objective lens of 0.25 Numerical Aperture (10x) and a ISx Ocular. Approximately 200-300 particles were counted ir. eacr. size class, except where frequency of occurrence in the viewing field was very lew, indicating concentrations in air far below the threshold limit value. The counting standard w2 deviation was estimated to be , where N is the total count for the sample. A blank count was made cn the distilled water. Dust concen tration ir. the air, expressec as millions of particles per cubic foot (MPPCF), was calculated from the sample volume, liquid collection reservoir, and sample and blank dust counts. B. Membrane Filter Metr.od A membrane filter (Type HA Millipore) was used to obtain samples for microscopic evaluation of fiber and dust particle concentrations. This paper is composed of pores 0.45 microns in size and has been shown to retain, with 1001 efficiency', particles down to 0.05 micron diameter^-. The filter was first visually examined to detect any loose dust or uneven dust deposition. In the few cases where the filter deposit did net pass this examination it was necessary to resuspend the collected dust in distilled water and refiiter this suspension cn VF grade Millipore filter to .ssure an even dust distribution over the entire filter area. A pie shaped segment of the filter was then placed cn a microscope slide and rendered completely transparent with Cargiile certified index.of~refraction liquids. Carciile liquid cf index of Kegaw, K.J. and Wiffer., R.D.: Int. 3. A.r Wat. Poll. 1_, 501 (1963). -3i refraction 1.500 was usually most suitable. The counting of the dust particles and the counting and sizing of asbestos fibers was performed with the aid of a Zeiss Photomicroscope using Phase Contrast Illumination The objective lens was a Zeiss Neofluor Ph 63x with a numerical aperture of 0.90. The eyepiece had a magnification of 20x and contained a calibrated Porton graticule. The optovar feature of the Zeiss scope contributed to the total magnification of 2016x. Resolution was approximately 0.35 microns. Particles and fibers o: size 0.30 microns could be detected. In the evaluation procedure, all particles and fibers in the Porton field of view were counted and tne fibers were grouped by fiber length into three categories (less than five microns, five to ten microns and larger than ten microns). This procedure was repeated for a number of randomly selected fields on the face of the filter. Because only a portion of the total filter area was evaluated by this method, it was necessary to correct the count by the ratio of the total filter area to the evaluated area. The resultant particle or fiber number was divided by the volume of the air sample to obtain dust or fiber concentration expressed as milliens cf particles per cubic foot (MFPCD. The statistical reliability of the evaluation was expressed as the standard deviation, calculated as where N is the particle or fiber count. The procedure outlined follows, in its essential points, that recommended by J. R. Lynch 3nd H. E. Ayer in their article "Measurement of Asbestos Exposure" which appeared in the Journal of Occupational Medicine, Volume !. January, 1968. V. RESULTS AND DISCUSSION Measured concentrations of dust and asbestos fibers are summarized in Table 2. All samples were obtained in the breathing zone of men or at breathing level in arias where men were not at work at the time samples were obtained (in aisles, for instance). Im.pincer and membrane filter samples were obtained simultaneously at the sites shown. Only at the last five sites were midget impincers used without simultaneous mentorane filters operating. It is seldom that air sampling reveals a picture as consistent as the one depicted by the data in Table 2. With the exception cf two samples obtained with the impinger, all results indicate concentrations in excess of the present U.S. Threshold Limit Value of 5 MPPCF. It should be noted that the U.S.T.L.V. is in terms of total particles and not fibers alone. This approach stems from epidemiological methods initially used in surveying the asoestos industries. According to the British classification, three membrane filter samples were in the Medium dust category (0.057-0.28 million fibers (>5 urn) per cubic foot) and the remaining six samples'were m the High dust category ( 0.28 million fibers (>5 urn) per cubic foot:. These results suggest that with tr.e present dust control facilities operating under optimum conditions of maintenance, dust concentrations are high in the Unibestos plant. The highest concentrations of dust were measured at cutting stations and in the vicinity of the. feed stations in the raw materials formulation area. The high results at the buildup static:, were due to dust from the feed area backing up to the buildup area. The high dust levels at the L'r.iciaa area are surprising, but it was noted that the men use a special abrasive spor.ce to smooth the rolls ana this may contribute to the cust. Exnaust hoc-ds are not used m this area. Possible major sources of the excessive dust are not hard to pinpoint and they will now be cited. A. Raw materials formulation area. 1. Transfer of asbestos from bags to feed bins and recovered asbestos from the collection "house" to bins are major sources of dust emission. Present efforts directed at pneumatic pick-up cf scrap will reduce the latter source. 2. Line feed bin hoods are net effective based on measured face velocities. The new bin hood design is superior to the old design, but the need to eper. asbestos bags from the tops ;cf bins results in low air velocities at the bases of bin opening faces. The problem is the sloping face cesirr. of the bin entry. 3. Low room air velocities in the feed area indicates poor ir turnover in this room. Velocities were 20-30 fpm. 4. Doers remain open in the scrap storage bir. and oust enters the room a. material drops to the base ci the bin and "pulses" the custladen air outward. 5. Floor sweeping and cleaning in this area generate a large amount of dust. B. Unibestos Cutting Area 1. Absence of hood at No. 3 Line Unloading Station. 2. Line No. 3 "push-pull" hood system at cutter is inefficient. The "push" and "pull" areas are equal and the jet merely "splashes" off the "pull" .'.cod after expansion in transit. 3. Line No. 3 exit hood ineffective. 4. Line No. 2 cutting hood is downdraft on the left side, | side draft on right side. The latter is ineffective. 5. The hood set-up for Line No. l,a canvas hood installed by the operator, appeared to work well and should be looked at for permanent design ar.c use on Lines 2 and 3. Thus, the problem ir. this area is really one of poor or non existent local exhaust hood design. It is beyond the scope of this report to present detailed hood designs. The designs required at these sites are not elaborate, but the additional a^r capacity must be in the dust collection system. Information conveyed to the author by Kr. Do!away indicates that the present system does not have this capacity. 11 I fl 4 :5 -6- (I rj IJ < < I B re a th in g Jieno.