Document 5krpkeargwZaj8LV2kMmV8x04

t REFERENCE SHELL OIL CO MPA N \ PRIVATE & CONFIDENTIAL -io_ REFINERY MANAGERS r-----ANACOHTE3 CDESSA/CINIZ; -- : ... - - HOUSTON-^ - - -- MARTINEZ -------W--O--O--D----R--I-V- mER 1 ~NORCO DATE MARCH 10, 1972 from GENERAL MANAGER - REFINERIES - HEAD OFFICE subject INDUSTRIAL HYGIENE Har.Jlo _ I/J ' On January k of this year, the Occupational Safety and Health LStration (OSHA) announced a "Target Health Hazards Program" aimed limproving workplace conditions where potential may exist for exposure -------of workmen to five toxic substances - asbestos, cotton dust, silica, lead ------ and carbon monoxide. The program will no doubt result in increased atten-------tion by Department of Labor Compliance Officers to these substances when they perform facility inspections. Informational sheets (Attachment 1) have already been prepared by OSHA describing these materials, the hazards associated with them, and control of same. Specific instructions (Attach ment 2) have been issued to compliance officers regarding sampling of atmospheres to determine if workmen are being exposed to concentrations in excess of that specified in the OSHA Safety and Health Standards. In view of the foregoing, it is likely that any inspection of a Shell refinery will include a review of potential employee exposure to asbestos, silica and carbon monoxide. We have not included lead since the "Target Health Hazards Program" is concerned only with inorganic lead and exposure of employees to dust or fumes from this material is considered minimal. IiT addition to asbestos, silica and carbon monoxide, there are certain other substances which also appear to warrant special attention, since they are commonly encountered in our refineries and were among those covered by the safety and health standards issued on May 29, 1971. These standards specify the maximum level at which continuous exposure (eight hours per day) to each of some 1*80 air contaminants is permissible without using protective equipment. Examination of the list indicates some 60 of the U80 contaminants could he encountered in a typical refinery (excluding laboratory facilities). Out of these 60, 12 substances have been selected (see Attachment 3) which we believe are most likely to be involved in any inquiry into how effective our safety programs are in protecting employees from excessive exposure. In designating these specific contaminants, consideration was given to factors' such as threshold limit values, how extensive a material is either used in tb.e refinery or in a process, potential for release to the atmosphere, and whether the substance possesses characteristics where its presence in the air would be readily detected at levels below the threshold limit value. Although in cur opinion the exposure levels to refinery employees from airborne contaminants are either well on the safe side or else adequate precautions are being followed involving use of protective equipment, we believe it would be prudent to initiate a program to provide for monitoring DPMC-00969 LAM 007483 ttL'JV-LriJJKY MANAGERS Page 2 the atmosphere periodically at locations where the substances listed on the attachment may occur. With the exception of asbestos and silica, sampling for the other materials can be accomplished with conventional detector tubes or other techniques commonly utilized by refinery safety staffs. The analysis for asbestos and silica is somewhat more complicated and we plan to solicit the assistance of industrial hygienists from the Head Office Occupational Safety and Health Department in evaluating exposure of employees to these substances. Initially, such a study will probably be limited to a single location to gain general insight into the severity of exposure. With regard to the other ten substances, we are thinking in terms of all refineries per forming' measurements quarterly until meaningful trends are established. This initial effort to document existing levels of hazardous substances and thereby demonstrate that typical refinery exposures are below the allowable TLV's is in anticipation of what we believe will be an accelerating program of monitoring by the Department of Labor. Even tually, industrial hygiene programs may have to be expanded somewhat since the Department of Labor has plans for developing detailed standards for many of the toxic substances and harmful physical agents. Presumably, these will be similar to the one presently proposed for asbestos, which was forwarded to refineries by Manufacturing Engineering with their memorandum of February 1, 1972. It is expected that in some cases the standards will require development of considerable detailed information on exposure of employees to health hazards. As an adjunct to the proposed program of monitoring outlined above, we have made plans for industrial hygienists from Head Office to survey Wood River Refinery in the near future to determine if some additional action would be warranted at this time in regard to our industrial hygiene programs. While awaiting the outcome of that survey, we would appreciate your reviewing the attached list and transmitting to this office any comments you have pertaining to sampling for contaminants, plus any additional views which you believe should be considered in regard to further action in the area of industrial, hygiene. [ G. Holzman Attachment cc: General Manager - Technical Departments Assistant to the General Manager - Refineries Occupational Safety and Health - Manager Manufacturing Engineering - Manager OPMC-00970 LAM 007484 Attachment i TARGET HEALTH HAZARD FACT SHEETS PREPARED BY THE OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION ASBESTOS What is it? Asbestos is a goner::! term used to describe cevcial fibrous mineral silicates that occur as white, grayish o; greenish masses, either compact or of long silky fibers. The most important types are: Chrysolite - a simple magnesium silicate; amosite -- a complex magne sium iron silicate, eiocidoiite - a complex sodium iron silicate. Some 95 per cent of world asbestos production comes from chrysolite. Where is it? The heat-resistant properties of asbestos have led to many uses -- for example, as piolcction against fire, as insulation, brake and clutch linings, build ing materials, as a filter and in plastics. The raw material arid end-products are found nearly everywhere. What is the- hazard? More than 200.000 employees face risks from asbestos. The principal danger is caused by inhaling asbestos fibers. Recent studies have shown the presence of asbestos fibers in the lungs of persons having no industrial exposure -- probably due to their presence in the atmosphere near construction sites. Prolonged inhalation of asbestos fibers between 5 and 50 microns (one-millionth of a meter) long can produce a lung disease known as ashestosis. The lungs cannot eliminate asbestos fibers, so the fibers coat the tissues. If this process combines over a period of 10 to 20 years, with significant quantities of asbestos present, lire tissue reaction prog resses until a generalized, diffuse fibrosis occurs, causing severe respiratory disability. There have been reports of increased incidence of lung cancer in persons with asbeslosis. How it is controlled? Enclosure and local exhaust ventilation applied to equipment and/or operations arc the principal means of preventing employee exposure to dangerously high concentrations. U.S. Bureau of Mines-approved dust respirators may be worn by employees as protection for some operations. What arc approved levels? CSHA's permissible level is 5 fibers per miliiliter greater than 5 microns in length for an eight-hour, time-weighted, average airborne concentration. Tins may be increased to 10 such fibers per milliliter for no more than 15 minutes per hour, up to five hours per eight-hour day. Imminent danger situations are generally not applicable. Any exposure greater than permissible levels for unprotected or improperly protected workers is considered a serious violation. How is it measured? Asbestos dust will be collected with a personal sampling pump. Fibers will be counted microscopically at 400-450 magnification using phase con trast illumination. COTTON DUST WTierc is it? Cotton dust occurs throughout the textile industry and attects cotton, flax and soft hemp winkers. The greatest exposure to cotton dust generally occurs during the carding ot cotton -- an operation that combs out cotton fibers and sets them parallel by drawing them between toothed cylinders. However, machinery through out the cotton mill must be cleaned frequently, arid much exposure to cotton dust occurs then. What is the hazard? More than 800.000 employees in cotton processing operations of ail types are exposed to cotton dust. While the exact effects of cotton dust are not known, prolonged exposure to heavy air concentra tions can cause a disabling lung disease known as byssinosis. Materials adhering to cotton fibers, such as unwanted leaf, stem and boll trash, when inhaled, elicit an allergic reaction or response. Byssinosis generally ad vances through three recognizable stages. The first is commonly called "Monday fever" and begins only after exposure of more than 10 years. Workers develop an irritating cough, tightness of the chest and breathlessness. The attacks usually come on Monday, or after a period of absence from the plant and last only a day or so; lienee the name "Monday fever." In the second stage, she.se symptoms extend over more days in the week and finally become permanent. If exposme to cotton dust is ended at this stage, recovery can occur. In the thitd stage, the tightness of the chest and labored breathing become so distressing the worker must leave the industry. The dis ease can progress then to chronic bronchitis and emphyse ma. How is it controlled? Enclosure of machinery in all operations and local exhaust ventilation are the principal means of preventing employee exposure. Pretreatment of the cotton in early processing stages may also be helpful. What are approved levels? OSH's permissible level is 1 milligram per cubic meter of air for an eight-hour, time-weighted, average airborne concentration. Imminent danger situations are generally not applicable. Concentra tions of 3 milligrams per cubic meter, are considered serious violations: concentrations between 1 and 3 milli grams per cubic meter for' an eight-hour, time-weighted, average, are considered regular or nonserious violations. How is it measured? A personal sampler is attached to a workman's clothing with the uncovered filter facing down, usually for a six-hour sample. SILICA What is it? Silica is an oxide of silicon and is the characteristic ingredient of a great variety of minerals, including quartz, cristobalite. tridymite, amethyst and sand. It is widely used in cores for metal casting opera tions, ceramics, decorative materials, insulation, building materials and glass. Where is it? Silica is found throughout industry in various manufacturing processes, such as iron and mineral processing plants, mining, abrasive sojp production, glass manufacturing, potteries, foundries, abrasives use and mariufaciurine. in stone cutting and finishing industries. Occopotionet Safely & Heolrli Reporter DPMC-00971 LAM 007485 What is liv.' hazard? More m 1.1 million employees are expose-.! lo the hazard crc.-.tcd by inhalation of silica dust, inhalation of these panicles can produce rapidly-de veloping, (acute) or chronic silicosis - a disabling lung disease. Typically, the kina tissue reacts to the presence of silica particles by forming fibrous matter around the particle, Evidence suggests that pat tides below one micron (one-millionth of a meter) in size may be the most dangerous since they may penetrate deeper into the lungs - in high concentrations. In rapidly-developing silicosis, symptoms appear eight to IS months alter the first exposure. Chronic silicosis, tire type usually en countered in industry, generally, is produced only after years of silica inhalation. Trie symptoms for either type are the same - slowly increasing difficulty in breathing, under exertion. In some workers, large masses of dense fibrous tissue develop in lite upper portion of the lungs, leading to severe respiratory crippling. Tuberculosis is a frequent complication of silicosis. How is it controlled? The best method is substitution of another material; for example, use of steel shot or alumina grit in place of sand-blasting operations. Oilier methods include enclosure of operations, local exhaust ventilation, segregation of operations, wetting, and ordi nary' good-housekeeping practices. What arc approved levels? For icspirablc quartz particles, OSHA's permissible level is 10 milligrams per cubic meter of air, divided by the per cent of free silica plus 2, as shown in this formula: lOmg/m*. %Si03+2 For respirable cristobalile and tridvmitc, the limits are one-haif the value for quartz. Imminent danger situations generally arc not applicable. Any'" eight-hour, timeweiglited average greater than four times the limit is considered a serious violation. Exposure lo concentrations between the limit and four times the limit are considered a regular or nonserious violation. How is it measured? Personal sampling pumps with filters are used to collect dust samples for worker ex posure. The collected dust then is weighed for a given volume of air. Similar procedures are used to determine the percentage of silica in the air. LEAD What is it? Lead is a soft, dense, malleable, heavy metal with a low melting point. It is gray in color and, because of its characteristics, has a wide application of uses. Where is it? Lead is used to make printing type and plumbing, shield telephone and power cables and to protect against radiation liazards. As an alloy, lead mixed with steel makes excellent bearings. As solder, lead alloy is vital in the electrical and electronic industries. Lead compounds are used to make paints and ammunition, and lead oxides are used in car batteries. What is the hazard? More than 1.6 million employees in nearly every industrial manufacturing process and in many' service industries ate exposed to the poisoning effect of lead. Lead can enter the body by inhalation, absorption through the skin or by ingestion. In sufficient quantities, result is the same -- severe gastrointestinal, blood and central nervous system disorders. Inhalation of lead tlusi or fumes is the most frequent means of entry and lesults in most of the industrial health problems involving, this metal. Lead is a cumulative poison. A part of a small daily dose is not eliminated, but is stored ir. the. body. Eventually, a point is readied where symptoms and disability - even death - occur. How is it controlled? Since the primary route cf industrial lead poisoning is inhalation, enclosure and local exhaust ventilation are trie principal means of control. Daily wet or vacuum cleaning of all lead dust, personal hygiene, prohibition of food and beverages in the work area and use of LkS. Bureau of Minss-apptoved respirators are other means that can help control exposure. What are approved levels? OSlIA's permissible level is 0.2 milligrams per cubic meter of air for an eight-hour, time-weighted, average airborne concentration. Imminent danger situations are not generally applicable. Any ex posure above. 0.6 milligrams per cubic meter of air to: art eight-hour, timc-weigliieu average is considered a serious violation. Levels above 0.2 and less than 0.6 are con sidered regular or nonserious violations. How is it measured? The atmosphere is sampled with personal sampling pumps and filters for a minimum of 63 minutes. Filters then are weighed to determine concentra tions. CARBON MONOXIDE What is it? Carbon monoxide is a colorless, almost odorless, tasteless, nonirritating gas. It is produced by the incomplete combustion of fuels, such as wood, gas. coal oil and gasoline. Miners refer to it as "white camp''. It also is commonly called "coal gas". What is it? Carbon monoxide is found anywhere car bonaceous fuels arc used. It can be found in everyday activities as well as in industrial situations -- near in correctly vented gas heaters, near g3so!;ne-pov>ered .ma chinery and around automobiles run indoors: blast fur naces; and catalytic reduction operations. What is the hazard? Because it is found so widely, nearly everyone, at' cue time or another, is exposed to carbon monoxide. The danger lies in inhalation of gas. Carbon monoxide enters the blood stream through the lungs in tire same manner as oxygen, but it displaces oxygen in the blood because it has approximately 210 times greater affinity for hemoglobin in the blood than oxygen. As a result, the blood cannot transport oxygen, causing suffocation even in an atmosphere containing ample oxygen. Over a period of time, as little as 700 parts per million of carbon monoxide will saturate 50 percent of the blood hemoglobin - while a few breaths at concentrations of 10.000 parts per million may cause 60 to 80 percent saturation and death. Fortunately, regard-, less of how high the percentage of saturation of the blood has been, practically all carbon monoxide is eliminated by the body within. 8 to 10 hours after exposure ends. How is it controlled? In general, aclecuate ventilation will prevent carbon monoxide poisoning. Enclosure, gen eral or dilution ventilation and local exhaust ver.ttlamm. Copyright 1972 by The 1 ifeou of Nolionol Aftoirs, trie. DPMC-00972 LAM 007486 is* mu ion 4,.i trat'.ardou'". operations ate the 'jir.r rrj..:!' means <*f preventing employ' xposuie to dan gerous concentrations. Automated detection ahum sys tems j'io me useful control nteasu'-cs. Vi'hst -arc approved levels; GSilA's permissible level is 50 parts per million parts of air for an eight-hour, tiii'iC-w-.ieliicd, average airborne concentration. Concentra tion above 500 parts per million for any leant It of time ate considered to l>e imminent danger situations. Con centrations above 150 nnrts per million for a total of one hour or more arc sidcied to he serious violations. Concentrations above 50 parts per million, but below 150 parts per million for an eight-hour, time-weighted average are considered regular or nonseriotis violations. How is it measured? The primary method is a carbon monoxide portable. Hopcnlite-icagenl type meter. 11 ic secondary method is certified detector tubes. DPMC-00973 LAM 007487 SAMPLSN DATA SHEETS FOR HEALTH ' 7ARDS PREPARED BY THE OCCUPATIONAL SArETY AND HEALTH ADMINISTRATION /i U O /i. OSHA SAMPLING DATA SHEET NO. 1 Subsiar.ee: Carbon monoxide. Standard: 29 CFR ]9J0.93{b) Table G-I, of August 13, 1971 S-hour lime-weighted average: 50 pprn (55 mg/mJ). Sampling Equipment: (1) CO meter. (Tollable. Hopcalite -- reagent type) -- Folio*- directions. (Plenary Method) (2) Certified or KIOSH approved detector tubes and a Brand opetated pump (not squeeze bulb) may be used for compliance purposes. (Secondary Method) A nalytical Procedure: (1) Direct rending instrument based on measurement of heat of reaction produced by oxidation of CO to CO2. Follow instructions. (2) Detector tubes are read for length of stain, strokes of pump are noted and appropriate corrections made for pressure (or altitude) above 5000 feet (1500 m). The tubes are not to be used when below 0 degree F (-18 C) or above 125 degress F (52 C). Sampling Period: (1) Hopcalite: maximum feasible number of readings should be averaged to determine average exposure. Time required dependent on variability and cyclical nature of exposures. (2) Detector tubes: direct reading, leristh-of-stain detector tubes (certified on NIOSH approved) may be used for compliance purposes, if at least one sample per hour is taken per exposed worker or dose group of workers. In an 8-hour day more frequent samplings per hour are preferred, especially for exposures over 50 ppm. Eight different samplings (one per hour is considered the minimum acceptable number). Imminent Danger Situations: Concentrations above 500 ppm (10 x TLV) for any length of time are considered to be an imminent danger. Serious Violation: Concentrations above 150 ppm (3 x TLV) for a total of I hour or more in an S-hour workday are considered serious. Nonscrious Violation: Concentrations above 50 ppm, but below 150 ppm for 2n S-hour time-weighted average are considered nonscrious violations. Dc Minimis Violation: Not applicable. Standard: 29 CFR 19J0.93a(a) of December 7, 1971 8-hour time-weighted average*: 5 fibers per milliliter greater than 5 microns in length. Excursion limit*: 10 fibers per milliliter, up to 15 minutes in an. hour for up to 5 hours pier 8-hour day. ""Unprotected or improperly protected worker ex posures.- Analytical Method: ' Fibers counted at 400-450 magnification, using phase contrast illumination, with sample mounted in high- viscosity .solution of membrane filter material. Sampling Equipment: Personal sampling pump plus Millipore type AA filter (37 mm, 0.S micron pore size). Face cap is removed and filter used open face during sampling. Sampling rate: 2 1/m. Sample Size: Minimum period of 15 minutes for evaluation of excursion limit. Several samples of up to 4 hours for evaluation of 8-hour average. Samples with a visible deposit may be too heavy to count. Compare with a clean filter. Heavy concentrations of visible dust in the air (100 to 500 fibers/ml) may require short sampling periods of only 5 minutes, or less. Blanks: With each batch of samples submit two filters which are subjected to exactly the same handling as for the samples except that no air is drawn through them. Label these as blanks. Shipping: The cassettes in which the samples are collected should be shipped in a suitable container, designed to prevent damage in transit. Imminent Danger Situations: Generally not applicable. Serious Violation: 5.1 or more fibers per ml, greater than 5 microns in length, for an unprotected or improperly protected work er, for an 8-hour time-weighted average, except for certain proven excursions as noted in the emergency standard, which may raise the S-hour time-weighted average to 5.S fibers per ml. Nonscrious Violation: Not applicable. Dc Minimis Violation: Not applicable. OSHA SAMPLING DATA SHEET NO. 2 Substance: Asbestos. OSHA SAMPLING DATA SHEET NO. 3 Substance: Crystalline silica. Occupotional Softly & Health Rcporlor DPMC-00974 f LAM 007488 Standard: 29 CFR 1910.93(h) ''able G-3 of December 7. 1971 Form 10 me/m3 Quartz (respirable): %SiCK + 7. Ciislobelitc: One half the value for quartz Tiidvmr.c: One-half the value for quartz / nalyticalletliod: Gravimetric persona! samples for worker exposure slrouk! be Fared am! reveigiied bv DOL on a Calm balance. The percent of free silica is determined by NIOSll on tire fixed location sample using a colorimetric wet chemical method, minimum detectable amount: 0.01 mg/fi!lcr. Sampling equipment: For worker exposure: Personal sampling pump plus preweighed MSA type FWS-B or Gelman type VM-1 filter, using 2-piece filter cassette and 10 mnt nylon cyclone. Two filters should be subjected to the same handling as the samples except that no air is drawn through them, and these should be used as blanks. Sampling rate: l.S 1/m. :For determining % quartz: Collect at fixed locations near workers, using NIOSH preweighed MSA type FWS-B filters in 3-picce cassettes plus Cast 1531 pump with 9 1 /m critical orifice and J/2 inch steel cyclone. The vacuum release valve should be adjusted to 10-15 in. Hg suction. Two blanks of the same filler type should be submitted with the sample. Sampling rate: 9 1/nt. Sample Size: Minimum: 4 hours. Maximum: 8 hours. Shipping: The cassettes in which the samples for determining % quartz arc collected should be shipped' to NIOSll in a suitable container, designed to prevent damage in transit. Imminent Danger Situations: Generally not applicable. Serious Viohtion: Any 8-hour time-weighted average greater than 4 x staled TLV value. Nonserious Violation: Any 8-hour time-weighted average between the stated TLV and 4 x that value. Dc Minimis Violation: Not applicable. OSHA SAMPLING DATA SHEET NO. 4 Substance: Lead and its inorganic compounds (except lead ar senate). Standard: 29 CFR 1910.93(b). Table G-2 of August 13. 1971 & ANSI 237.11-1969 8-hour time-weighted average: 0.2 nig/m3 A nalytical Method: Atomic absorption. Detection Limit: 0.0003 ntg/filter. Sampling Equipment: Persona! sampling pump plus unweighted 37 mm Milii- porc type HA filter. Hither 2- or 3-piece filter cassette may be used mpling rate: 1.5 1/in. Sample Size: A minimum sampling period of 60 minutes is recom mended, and iouger periods, up to full shift, are prefer able. Care must be taken to prevent materia! from falling off heavily loaded filters during shipment. This may be done by placing another filler on top of the one-with the sample, exercising care not to dislodge any of tire sample in the process. Blanks: With each batch of samples, submit two filters which arc subjected to exactly the same handling as for the samples except that no air is drawn through them. Label these as blanks. Shipping: The cassettes in which the samples arc collected should be shipped in a suitable container, designed to prevent damage in transit. Imminent Danger Situations: Generally not applicable. Serious Violation: Anything above 0.6 nig/ni3 for an 8-hour time- weighted average. Nonserious Violation: Anything above 0.2 mg/m3 and less than 0.6 mg/nt3 for an 8-hour time-weighted average. Dc Minimis Violation: Not applicable. OSHA SAMPLING DATA SHEET NO. 5 Substance: Cotton dust (raw). Standard: 29 CFR 1910.93(b). Table G-l of August 13. 1971 8-hour time-weighted average: 1 mg/nV Analytical Method: Net weight of gross airborne dust, using balance with sensitivity of 0.01 mg. , Sampling Equipment - Personal Samplers: Cotton is to be determined primarily with the personal sampler attached to the workman's clothing with the lac; of the filter pointing down. The filter should not be covered. Our experience is that at least a 4- and prefer ably a 6-hour sample (at 1.5 1/m) is required in a textile plant.opening or carding area to obtain reliable results. A preweighed filter (0.01 mg) should be used and reweighed to the same accuracy. There is no ceding or any limit on excursions. Because of the nature of both the sampling method and the development of bvssinosis. it is neither desirable nor possible to get grab samples. Sampling Equipment - General Work Area: Preweighed Gelman VM-1 or MSA type FWS-B 5 micron pore size filter in 3-piece cassette, located in the general work area with the cap removed and the filter facing down. Suction provided by Cast 153! pump with a 7.4 1/nt critical orifice. The vacuum relief valve should be Copyright 1972 by The Bureau of National Affairs, Inc. DPMC-00975 . t - . LAM 007489 fl'-ij to maintain 1015 in.. Mgs' in. Sampling rale: 1A 1/m for recommended siiirriniv.,ii of 60 minutes. Longer period samples up to full sliifl are preferable. Fillers shouid mu be so heavily loaded that the saiiiple is dislodged in transit. Blanks: With each batch, of samples collected, twb additional filters should be subjected to exactly the same handling except that no air is drawn ihrough them. These should be used as blanks. Skipping: The cassettes in width samples arc collected should be shipped in a suit: damage in transit. container, designed to prevent Imminent Danger Situations: Generally not applicable. Serious Hazard: An 8-hour time-weighted average above 3 mg/m3 for identified worker. 3 x TLV. * Nonseriotts Hazard: An S-liour time-weighted average above 1 mg/m3 and below 3 mg/m3 for an identified worker. Dc Minimis Violation: Not applicable. DPMC-0G978 LAM 007490 Attachment 3 AIR CONTAMINANTS PROPOSED FOR INCLUSION nr MONITORING PROGRAM Substance Asbestos Benzene Carbon Monoxide Hydrogen Fluoride Hydrogen Sulfide Mercury Methyl Ethyl Ketone Phenol Silica Sulfur Dioxide Toluene Xylene Threshold Limit Value ppmaj mg/M3b) c) 25 80 50 55 32 10 - 0.14) 200 590 5 19 e) 5 200f) 100 13 750f) *35 a'Parts of vapor or gas per million of contaminated air by volume at 25C and 760 ram. Hg. pressure. ^Milligrams of particulate per cubic meter of air. c)covered by a special, emergency standard issued December 7, 1971, which bases threshold limit on maximum of five fibers per milli liter greater than five microns in length, rather than on ppm. A proposed permanent standard recommends same TLV level. ^Change to 0.05 mg/M^ is proposed. e) Quartz = 10 mg/M^ %ii102+2 Cristobalite or tridymite: One-half value for quartz. f) change to 100 ppm and 375 mg/M3 is proposed. DPMC-00977 LAM 007491