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* < Industrial hygiene news report Volume 15 May, 1972 Reporting on new developments in industrial hygiene, air pollu tion control and environmental health. Annual subscription: $15X0. Published monthly by Flournoy & Associates, 1845 W. Morse. Chicago. 111. 60626. I: (Editorial Consultants:; . ;i ^ .. William T. McCormick Herbert T. Walworth Number.:5;; NEW METHOD FOR IDENTIFYING ASBESTOS FIBERS'IN THE "LUNGS r - ' A newly developed, rapid screening method for determining whether inhaled fibers are asbestos or nonasbestos has proved to be practical and economical in studies described by Paul Gross, M. D., Director of the Industrial Health Foundation's Research Labora tories (5231 Centre Ave., Pittsburgh, Pa. 15232), at the Industrial Medical Association's 57th annual meeting in Philadelphia, April 17-20. The method described is based on the fact that asbestos fibers are composed of bun dles of finer fibers which tend to break at different levels when stressed. The end of such a bundle of fibers accordingly shows a series of step-like elevations and depres sions, each having different dimensions. Non-asbestos fibers, in contrast, consist ing of a single unit, tend to break without the steps and show a conchoidal type of fracture. This screening procedure requires the use of an electron microscope at a magnification of about 25, 000 to 30, 000 or higher, and is not free of error. The non' asbestos fibers found inhuman lungs include man-made fibers such as glass, rock ^ wool, cerami c aluminum silicate, or silicon carbide, and mineral fibers which are released when plants or their products (leaves, wood, paper, or coal) are burned and the ashes disseminated by winds. Other fibers found in lung sediments have been identified electron microscopically as derived from fragmented diatoms. A recent adaptation of a method of quantitating dust in the lungs which makes use of elec tron microscopy has made it possible to enumerate submicronic fibers. This was ac complished by adding a known concentration of latex spheres to the suspension of lung sediment and then transferring a tiny droplet of this mixture to an electron microscope grid. All fibers longer than, and shorter than, 5 p were counted along with the number of latex spheres on the grid. From these numbers it was possible to calculate the total number of fibers, the number of fibers less than 5 p, and those more than 5 p in length --all on a per-gram-of-dry-lung basis. A count of chrysotile fibrils was also made. In general, the counts were lowest in lungs of persons who had lived all their lives near the Atlantic coast in non-industrialized regions. The most significant features of this tabulation are that the optical fiber count may represent as little as 9. 04% of the total fiber count; that identifiable chrysotile fibers may constitute 1 to 6jr% of all fibers present, or 11% on the average; in terms of fibers less than 5 p long'? the range of percentages of chrysotile is 1.4 to 79%, with an average of 14%; and that/ based on the total number of fibers, the fibers less than 5 p long ranged from 46 to'95%, with an average value of 75%. Preliminary results of an experiment in which'relatively large doses of short-fibered chrysotile (less than 5 p long) were injected intratracheally into rats have confirmed the conclusion that asbestos fibers less than^Z u in length are not fibrogenic. / ( 409680 0144 CONVERSION OF STACK GAS SC>2 TO ELEMENTAL SULFUR A process is being developed at Westvaco Corporation's Research Center (Charleston, S. C. 29406) for desulfurizing power plant flue gas with recovery of sulfur values in the form of elemental sulfur. This "dry" process which uses activated carbon in fluidized carbon beds can be attached to a power plant without interfering with the power genera tion cycle, according to information given in a paper by G. N. Brown, S. L. Torrence, A. J. Repik, J. L. Stryker and F. J. Ball of Westvaco, and Leon Stankus, of the En vironmental Protection Agency, Durham, N. C., which was presented at the American Institute of Chemical Engineers meeting Feb. 20-23 in Dallas. The basic concept of the process described is to use activated carbon to recover sul fur dioxide in a salable form. In the sulfur dioxide removal step, the carbon first catalyzes the reaction of the sulfur dioxide with oxygen in the flue gas at 200-300 F to form sulfur trioxide. This SO3 is then hydrolyzed to sulfuric acid and remains sorbed on the carbon. The acid loaded carbon is fed to the first step of regeneration, the sulfur generator, in which the sulfuric acid on the carbon reacts with hydrogen sulfide at about 300 F to form elemental sulfur. The sulfur loaded carbon then passes to the sulfur stripper where one-fourth of the elemental sulfur is recovered by direct vaporization at about 1000 F. The carbon containing the remaining elemen tal sulfur goes to the hydrogen sulfide generator where it is reacted with hydrogen from a gas producer to provide the hydrogen sulfide needed in the first step of regene ration. The clean regenerated carbon is then recycled to the sulfur dioxide sorption stage. A rate expression for SO2 sorption was developed as a function of SOg, H2O, O 2 and NO concentrations, carbon acid loading, and temperature which successfully tested in a 20, 000 cfh multistage fluidized bed pilot unit using real flue gas. Similarly, rates for the reaction of hydrogen sulfide with the carbon-sorbed sulfuric acid have been investi gated as a function of acid loading, temperature and H2S concentration. The elemental sulfur on the carbon is recovered either by thermal or solvent stripping. A PORTABLE ELECTRON CAPTURE GC FOR TRACING AIR POLLUTANTS A portable electron capture gas chromatograph which has been developed for real-time determination of sulfur hexafluoride in meteorological tracer studies appears to make feasible the tracing of air masses for 100 kilometers or more during unstable meteoro logical conditions. The instrument, which has been used in aircraft and land vehicles, can continuously measure the SF^ tracer gas down to a sensitivity of 4x10"^ cc/cc for a duration of 40 to 60 seconds with a response time of about three seconds for a 10-fold concentration change. It was described in a paper by Russell N. Dietz, Edgar A. Cote, and Robert M. Brown of the Brookhaven National Laboratory (Upton, Long Island, N. Y. 11973) at the American Chemical Society's 163rd national meeting in Boston, April 10-13: The portable gas chromatograph used in this study was an Analytical Instrument De velopment model 510 equipped with a Keithley operational amplifier and a 200 mCi tritium foil parallel plate type electron capture detector designed to operate under pulsed mode with a 5% methane in argon carrier gas. The only major modifications to the original instrument were the replacement of the Teflon cylinder within the de tector with one of glass (Teflon absorbs SF^ ), the removal of the needle injection port, and conversion of the detector to D. C. operation by installing an adjustable potentio meter on an internally available +15 VDC terminal. 2- - 409680 0146 The mode of operation is frontal chromatography instead of the usual finite injection sam pling. With this method, the carrier gas is replaced with the air to be analyzed and the recorder output is in the form of step waves in place of the usual peaks. In the backflash position, pure argon is sent to the detector while the molecular sieve column is backflushed. The argon is regulated at 20 psig producing a 70 to 80 cc/min backflush and the needle valve is adjusted for a detector purge of 40 cc/min. The molecular sieve is treated with nitric oxide as is the molecular sieve dryer ahead of the detector. About 20 seconds before sampling, the air sampling pump is activated and the back-pressure regu lator is set to 11 psig to purge the pump and sampling valve. After energizing the sole noid switching valve, approximately 40 cc/min of the air to be analyzed is passed through the column. Both the column and the detector are at 25 C. About 39 seconds after sam pling is commenced, the SF^ frontal reaches the detector followed by the O frontal 46 seconds later. At this point the solenoid switching valve is de-energized to backflush the remaining components of the atmospheric sample through the main vent. Tracing the SFg with this instrument extends by a factor of 10 or more the distance to which air masses have previously been traced by monitoring SF^ , SO2, particulates, or fluorescent particles; the SF^ sensitivity is nearly four orders of magnitude greater than that of other "continuous sniff" instruments. REGULATION OF NEW AND EXISTING COMMERCIAL CHEMICALS COMING At the present time, there are no legislative constraints on the use of new chemicals ex cepting for those used in pesticides, food additives, drugs and some consumer or house hold products, it was pointed out by Horace W. Gerarde, M. D. , Corporate Medical Di rector for Occupational Health, Becton, Dickinson & Company (Rutherford, N. J. 07070), who added that before the year is over this probably will no longer be true. Speaking at the Industrial Medical Association's 57th annual meeting in Philadelphia, April 17-20, Dr. Gerarde said that hearings are being held in Washington to regulate new and even existing commercial chemicals. The original bill called for mandatory premarketing certification of all new chemicals, comparable to Federal approval of new drugs, food additives and pesticides, with the regulation of these chemicals com ing under the jurisdiction of the Environmental Protection Agency. Under the new draft of this bill, toxicity data would have to be submitted to the EPA at least 90 days before commercialization, Dr. Gerarde said, and test data would include information on carcinogenesis, teratogenesis, mutagenesis, persistence, cumulative or synergis tic effects with other chemicals, other hazards and epidemiological studies of the ef fects of existing chemicals. Then, subject to confidentiality restrictions, the chemi cal's identity, intended uses and test data availability would be published in the Fed eral Register. FUME INCINERATION EQUIPMENT FOR SPECIFIC APPLICATIONS DESCRIBED Some relatively new equipment for fume incineration which will meet today's regulations as well as those five years hence was described by Dr. Klaus H. Hemsath of Midland Ross Corporation, Surface Combustion Division (P. O. Box 907, Toledo, Ohio 43601) at the American Institute of Chemical Engineers meeting in Dallas, Feb. 20-23. A Multifuel incinerator has been designed to provide multifuel capability. It can be fired with almost any conceivable fuel. Higher flexibility in the auxiliary fuels re quires higher pressure drops on the fume stream and requires additional equipment for oil handling and control. This incinerator is also capable of incinerating fume -3- 409680 0146 streams that contain less than 15% oxygen, and it has already proven its capabilities by incinerating black smoke to Ringelmann 0. The Rich Fume incinerator has been designed to incinerate a gas stream that does not contain any oxygen. Because rather-large amounts of combustion air are required for incineration, this air is being used to provide a pumping action. Gases containing small concentrations of hydrocarbons, CO or soot, can be as easily incinerated as well as sudden bursts of gases with high heating values. Controls automatically maintain incin eration temperature, hold the input of auxiliary fuel to the absolute minimum and provide the proper amount of combustion air. The Jet incinerator and the Injection incinerator are examples of specific solutions necessitated by unusual process conditions. The Jet incinerator not only incinerates but is also a pumping device -- off gases that readily condense and form coatings are often advantageously incinerated with this device. The Injection incinerator allows incineration of a high pressure off gas that sublimates at very high temperatures. In all the designs described, conversion efficiency depends solely on temperature or residence time, thus fume conversion efficiencies in excess of 99% can be achieved by either adding reaction volume or by adjusting the incineration temperature control set point. RADIATION DAMAGE FOR PLASTIC WASTE DISPOSAL In view of increasing use of plastic materials, particularly in packaging, and the prob lems involved in the disposal of wastes, experiments have been conducted investigating the feasibility of irradiating the plastic wastes, causing them to become brittle and thus easy to consolidate by subsequent mechanical treatment. Results of the studies were reported at the American Chemical Society's 163rd national meeting in Boston, April 10-13 by Masaru Tanaka, Assistant Professor of Civil Engineering, Wayne State Uni versity (Detroit, Mich. 48202) and Tsuyoshi Mifune, formerly of Wayne State Univer sity, now associated with Sumitomo Electric, Inc. , Osaka, Japan. Some details follow; Sheets of polyvinyl chloride and polyethylene were machined to form tensile speci mens which were mounted on tensile jigs and placed immediately behind a 0. 00508 cm stainless steel sheet which closed the end of the drift tube of a Van de Graaff accelerator. The incident electron energy was kept at 1. 3^0. 02 MeV for all mate rials examined. The number of electrons which passed through the collimator was measured by a current integrator. The current was kept at 5 pA which is equivalent to 2. 4 x 1013 e/cm^/sec. Tensile tests on the irradiated specimens were performed at room temperature (24 C) with a nominal strain rate of 3. 5 x 10 7sec. Results showed that the strength of the plastic materials was substantially reduced by the irradiation with 1. 3 MeV electrons, and the ductility was completely eliminated upon irradiation of approximately 3 x 10^ e/cm^ in polyvinyl chloride and 1 x 10*^ e/cm^ in high-density polyethylene. In examining the applicability of such radiation embrittle ment to plastic waste disposal, it was found that even with quite a large radiation source, it takes extended irradiation to make plastic materials brittle enough for subsequent mechanical consolidation and from the standpoints of economics and operational safety, it was concluded that the method cannot be recommended for commercial use. The treat ment has, however, two areas of potential use: (1) it may be suitable for very special wastes of small quantity such as extremely toxic hospital wastes; and (2) it may be eco nomically feasible as an application for the radiation wastes from nuclear reactors. Annua! subtcrot*on rate in U.S.A. and Canada, $15.00: in other countries $16.00. Reproduction of complete issue prohibited. Up to 20% of the conterts of an $sue may be reproduced without permission providing credit is given to the person quoted and to Industrial Hygiene News Report. 409680 0147