OSHA Instruction CPL 2-2.7 October 30, 1972

OSHA PROGRAM DIRECTIVE #300-3

TO: Field and National Offices/OSH

SUBJECT: Crystalline Silica

1. PURPOSE

This directive provides guidelines to be followed in inspections,and where necessary, the issuance of citations, regarding exposure to silicain the workplace.

2. DOCUMENTATION AFFECTED

This directive cancels the Silica Sampling Data Sheet of January 3,1972.

3. DOCUMENTATION REFERENCED

a. Field operations Manual, Chapter XIII.

b. OSHA Standard Method for Respirable Gravimetric DustSampling.

c. Guidelines for Control of Occupational Exposure to CrystallineSilica and Abrasive Blasting.

4. BACKGROUND

a. Chemical Data. Crystalline silica, also called alpha silica orgenerally free silica, is silicon dioxide (SiO2). In pure, natural form, SiO2crystals are minute, very hard, translucent, and colorless. The physicalproperties are: molecular weight, 60.09; melting point, 1710 C; boilingpoint, 2230 C; and vapor pressure, 10 mm Hg at 1732 C. Most mined mineralscontain some Si02. "Crystalline" refers to the orientation of SiO2 moleculesin a fixed pattern as opposed to a nonperiodic, random molecular arrangementdefined as amorphous (such as diatomaceous earth). The three most commoncrystalline forms of silica encountered in industry are: quartz, tridymite,and cristobalite. Quartz is a silicon dioxide polymorph with a compositionof 46.7% Si and 53.3% 0 crystallized in the hexagonal system. Tridymite is asilicon dioxide polymorph with a composition like quartz, but containingsodium aluminum silicate. It is crystallized in the ortho-rhombic system. Cristobalite is also similar to quartz but with various impurities. Structurally cristobalite is in the cubic or tetragonal system.

unit, are also sources of crystalline silica (usually less than1%). The silicates include: mica, soapstone, talc (non-asbestos andfibrous). tremolite, and Portland Cement.

OSHA Instruction CPL 2-2.7 October 30, 1972

b. Fire, Explosion Potential, and Reactivity. Under extremelyunusual circumstances. fine airborne dust can propagate an explosion: usuallya strong source of ignition is required (welders' torch, boiler furnace). Ina closed container in the laboratory, dust explosion can be initiated with aspark due to static electricity. The lower explosive limit will depend onparticle size. particle distribution in air, particle velocity, and themixture of dust (organic content, presence of gases, etc.).

c. Other Relevant Information. This section is for informationpurposes only, not for compliance action.

(1) Common Processes. Silica is present in almost everyprocess where natural minerals are handled. It is prevalent in foundrieswhere it has several uses, in the manufacture and use of abrasives, in theconstruction industry as an ingredient of materials or byproduct ofactivities, and in the manufacture of glass and Pottery. Some of theprocesses in which occupational exposures are to be expected are describedbelow.

(a) Glass Manufacture. The four main divisions of theglass manufacturing industry are flat glass. container glass, specialty (ortechnical) glass, and fiber glass. The end products in fiber glass aresilicates. Fibers should not be confused with crystalline silica as theyrepresent a different health problem. The major portion of all glass batchesis silica sand. Washed sand is commonly used. The amount of fineparticulates has been reduced by washing.

either by power scoop or by shovel and wheelbarrow, mayproduce large quantities of fine silica dust.

(i) Processes. The various types of glass manufacturedin the modern glass industry are made by two processes: the older pot processand the more common tank method. Heat stress may be associated with bothprocesses.

(A) Pot process. The pot process is used primarilyfor the manufacture of high-quality glass and for small quantity specialtyglass. The pots vary in size up to those capable of holding two tons ofingredients, for the silicosis cases reported in the glass industry. Thepots are made of different types of clay combined with flint or silica flour. Pot glass is manufactured in furnaces. waste heat causes considerableconvective air currents, therefore, breathing zone silica levels may be highthroughout the furnace areas. Pot melting of glass may necessitate handshoveling and hand filling of the pots. Optical and specialty glasses alsofrequently contain heavy metals, such as lead, barium, etc. During thehand-filling process, multiple exposures to dust of other ingredients, suchas heavy metals, may occur.

(B) Tank process. The tank method is used for highvolume production requirements, such as window glass, television tubes,container glass, etc. Glass tanks of current design provide for enclosedcontinuous feeding of batch ingredients. This system reduces if functioningproperly.

(ii) Repairs. The blocks and bricks used in theconstruction of the furnaces and tanks contain silica in significant amounts. Silica brick contains tridymite as its principal constituent. Dustconcentrations may be a problem to maintenance employees working on tanks. The hazard is caused by cutting and chipping of blocks and bricks to befitted into furnace structures. Introduction of prefabricated furnace blocksand parts has reduced the need to cut at the site ofinstallation.

(b) Portland Cement. Another major use of silica is in themanufacture of Portland Cement. In this process, the raw materials used maybe divided into four categories. These are: those supplying the limecomponent (calcaneous), the silica component (siliceous), the aluminacomponent (argillaceous), and the iron component(ferriferous).

(i) Size reduction to obtain fineness and increasedsurface area to allow the chemical reactions tooccur.

(ii) Blending, correction, and homogenization of raw mixto obtain desired composition and uniformity.

                         (iii)Burning to form new compounds, which                              liberates carbon dioxide.

(iv) Heat pulverization of kiln product with addition ofgypsum.

from raw material storage by overhead crane anddeposited in roughly the desired proportions which can be controlled. someof the sources of dust are quarrying, crushing, grinding, the rotary kiln.screens, bagging operations, and the loading and unloading fromtransportation vehicles. Heat stress may be associated with theseprocesses.

cement block and brick making, in brick kilns, and inkiln repair. The possibility of dual jurisdiction with MESA mayexist.

(c) Pottery Industry. The silica in the pottery industryis present as flint. In the production of pottery there are six basicprocesses: preparation of the body ingredients, forming and shaping, biscuitfiring, application of glaze. gloss firing, anddecoration.

OSHA Instruction CPL 2-2.7 October 30, 1972

transfer of raw materials from boxcars to storage bins. The dust hazard may also exist in the preparatory stages that follow such as:calcining, crushing, and grinding of flint, stone. etc. These preparatoryprocesses may be carried out in another plant. The possibility of dualjurisdiction with MESA may exist.

In the slip house the body ingredients are blended inwater, and:

(i) Plastic clay is produced by filtering andpugging.

(iii) Dust for pressing is produced by drying, grinding,and disintegrating.

Dust may arise from dry pressing, grinding, orevaporated blend. The plastic clay, dust. or casting slip then enters theforming and shaping phases. Plastic clay shaping is now primarily amechanical operation. Dust-pressed articles are produced by compactingpre-dried body-dust by hand or mechanical pressing.

finished and is then ready for biscuit firing. Outsidethe slip house. flatware brushing is one of the dustiest occupations andrequires control measures. The other finishing steps have less potential fordust hazard; however, multiple hazards should be expected in the glazingprocess. Rubber bands holding together drying forms are a source of finedust when dry.

(d) Foundries. The foundry environment varies primarilywith the kind of material poured. The exposure to silica dust in the foundryenvironment can be described by following the process from melting tocleaning.

(i) In the melting process the metals or alloys aremelted in a furnace of the cupola, electric arc, electric induction, oropen-hearth type. Silica exposure in the melting process, however, may beminimal. The primary hazard is exposure to metal fumes anddust.

The production of iron castings is accomplished byre-melting scrap along with pig iron in a furnace called a cupola. Thecupola may be a source of carbon monoxide, metal fumes anddust.

In an electric arc furnace, melting is achieved byheat transfer from the arcs that are sprung from the electrodes to the metalcharge. Electric furnaces may give rise to large amounts of iron oxide andvarious other fumes depending on the composition of the steel beingformed.

In an electric induction furnace a high frequencycurrent is passed through the primary coil, thus inducing a much heaviersecondary current in the charge (metal), which results in heating it byresistance to the desired

OSHA Instruction CPL 2-2.7 October 30,1972

temperature. In this process, melting is quiterapid, so that there is only a slight loss of the easily oxidizedelements.

In the open-hearth furnace, both the hearth and thecharge resting on it are exposed to the direct action of the flame employedin converting the solid charge into the liquid state. If a large tonnage iscontinually required, the open-hearth furnace isused.

(ii) Mold and core making presents multiple hazards dueto the use of silica and the great variety of binders and mold makingprocesses. Molds may be coated with flint or silica flour. After theinitial forming, molds may be preheated and cooled, and the surface may beretreated to prevent metal adhesion. Cooled molds may be called chills. Resinbinders and solvents (primarily alcohols) may be used, therefore multipleexposures are possible.

                         (iii)Pouring operations generate gases and                              vapors from the destructive                              distillation of sea coal mixed into the                              molding sand and synthetic gates.  When                              sea coal is used in mold making,                              evaluation for coal tar pitch volatiles                              may be indicated.  Multiple air                              contaminants are generated in the                              pouring operation. CO2 and CO may be                              generated when organic materials in the                              mold are heated.  Numerous organic                              components have been identified in                              foundry fumes.  The temperature of the                              metal to be cast in the mold.  Where                              pouring is done on the floor, the                              general practice has been to minimize                              these hazards by providing high                              ceilings with air outlets as high as                              possible and inlets near floor level.

(iv) After pouring, the molds are allowed to cool, withtime depending on size of the cast and the metal.

(v) After cooling, the external molds are opened orbroken in an operation called shakeout. Dust concentrations are high duringshakeout and cleanup operations. An effective control for the shakeoutoperation is the relatively complete enclosure with sufficient exhaustvolume, removed at the top of the enclosure to maintain an inflow of at least200 FPM at all openings.

(vi) Core knockout is a process in which the moldportion from the inside of the cast is removed resulting in the dispersion ofsilica dust. The use of compressed air jets to blow out the last of the coresand produces excessive airborne dust concentrations. A side hood arrangementmay be effective in controlling exposures depending on the size of the cast.Vacuum may be used to control dust in the core knockoutprocess.

OSHA Instruction CPL 2-2.7 October 30, 1972

Other operations generating dust are the transfer toreturn conveyer. transfer to elevator, transfer to and from belt conveyers.sand screens. tailing pipes, sand mixers and receiving points on sand bins. Since core sand is reused several times. it may become progressively finer. This may increase the number of respirable size particles in theair.

shaken out and the core mold removed, the casthas.to be rough ground to remove mold defects. The cast may still have a lotof fine particles embedded in or adhering to its surface, which becomeairborne upon grinding. Noise may be a major problem in this operation. Several engineering controls are proven and available. depending on the sizeof the cast, to control this problem.

(e) Abrasive Blasting. This process is used to clean,smooth, or prepare surfaces for additional treatment or appearance (such asbuildings, bridges. ships, etc.). Abrasive blasting is the high velocitybombardment of a surface by an abrasive material (wet or dry) propelled byprimarily pneumatic pressure. Three basic techniques may be encountered:dry, wet. and airless (centrifugal). A vacuum can be used to control dustwhen a pneumatic blast nozzle is used. Noise is a major hazard in additionto dust. The dust generated in any blasting process is a combination of thefragmented blasting media and the material dislodged from the surfacetreated. Where a fragmentable abrasive, such as sand, shells, cobs, glassbeads, metal shots or slag, is used, or where a fragmentable surface, such asa sand casting, a painted or scaly surface, or masonry, is blasted, the dustgenerated varies in particle size and chemical composition. The particlesize of the blasting agent decreases upon rehandling or reuse: liberation ofmore silica sand in the respirable size is possible if silica is present ineither the agent or surface. Due to the volume of sand used for somestationary operations, complete respiratory protection is necessary not onlyfor the sand blaster, but also for the entire work area if the blasting isnot done inside an effective enclosure (i.e., buildings, ships,etc.).

Where an employee is inside the enclosure, together withthe production parts to be sand (or shot) blasted, full protective clothingmust be considered. The contamination of the clothing with secondarycontaminants and blasting agents may occur.

(2) Signs and Symptoms of Disease. Upon repeated exposure todust containing crystalline silica, a fibrous lung condition called silicosismay develop. Signs such as labored breathing and early fatigue may indicatesilicosis; however, they can arise from many other causes. Diagnosis ofsilicosis can be made by a physician only and is difficult to make without awork history. The progress of silicosis

OSHA Instruction CPL 2-2.7 October 30,1972

can only be stopped; the lung condition cannot be cured. The incidence of tuberculosis is high among silicosispatients.

5. INSPECTION PROCEDURES

a. Pre-Inspection Preparation

(1) The inspection team or the assigned CSHO shall:

(a) Review any previous case files on the plant to beinspected, noting the size of the plant area, number of employees, and volumeof expected activities.

(b) Search applicable standard industry classification codein the state directory of industries (usually a Chamber of Commercepublication) for similar plants. Review the case files of similar plants tobecome familiar with problems to be expected.

(c) Use other technical information or literature toincrease the understanding of expected activities.

(d) Review all information obtained by the requestingofficer if the plant inspection is a referral visit.

(2) The team or the assigned CSHO shall also:

(a) Estimate the time to be spent at the plant. (b) Estimate the number and type of airborne contaminant samples to be taken.Review "OSHA Standard Method for Respirable Gravimetric Dust Sampling."Determine weights of all filters to be used in sampling which will requiregravimetric analysis.

(c) Establish availability of all supplies necessary beforethe planned sampling.

(d) A respirable dust (crystalline silica) sampling trainshall consist of a nylon cyclone, cassette, tubing and a personal airsampling pump.

(e) Check air sampling pumps for calibration or calibratefor 1.7 liters per minute with sampling train. Log calibrations of samplingtrains, including component numbers and calibrationresults.

(f) Obtain or prepare the necessary number of cassettesplus 10% spares.

(g) Prepare field log book and/or sampling work sheets torecord the following information for each intended sample to substantiateentries required for OSHA Form 1 and others:

(i) Employer's name;

(ii) Substance sampled and sampling procedureused;

(iii) Work activity and location sampled;

(iv) work load in area (above, below, or atnormal);

(v) Number of employees in area:

(A) Name, address. and telephone number;

(B) Social Security number, if possible

OSHA Instruction CPL 2-2.7 October 30, 1972

(C) Time spent per day at that activity;

(D) Type of respiratory protection and otherprotective equipment.

(vii) Instruments or pump used (and serialnumber);

(viii) Sample identification and cassette number (ornumbers);

(ix) Sample starting time and ending time;

(x) Starting flow rate and ending flow rate. ifapplicable;

(xi) Weather conditions;

(h) As other contaminants besides dust may be in theatmosphere, consider and prepare other sampling trains or capture media ifcombination of anticipated contaminants warrants it. Consult available OSHAstandard methods.

(i) Check, calibrate and log calibration of direct readinginstruments to be used in the survey (such as sound level meter, COanalyzer).

(j) Check camera and verify film and cameraoperation.

(k) Obtain and check personal protective equipment. Whenpreparing for an inspection of a plant with dusty conditions, in addition tothe normal protective equipment, obtain a respirator equipped with cartridgesor filters appropriate for anticipated exposures.

(l) Suggested list of sampling supplies should includestrong tape, Tygon tubing, scissors, sampling pump belts, plastic bags(Whirl-pack), and a clipboard.

(m) Review other applicable sub-parts of OSHA Health andSafety Standards anticipated during the inspection.

(n) Obtain and become familiar with copies of referencedocuments.

(o) Discuss the preparation for the plant visit withappropriate supervisor.

b. Inspection

(1) Upon entering the workplace, the CSHO shall contact plantmanagement, identify himself, and state the purpose of thevisit.

(2) Opening Conference. The CSHO shall obtain a process flowchart and plant layout, and determine production volume and activity cycles. If the plant facilities layout chart is not available, the CSHO shall sketcha plant layout subsequently during the inspection, identifying majoroperation areas, distribution of major equipment, building identification,existing and planned engineering controls, and approximate dimensions of theplant property.

or unusual due to maintenance shutdowns, acceleratedproduction, etc. If the production is down, proceed with inspection, but donot perform full scale sampling until normal production isresumed.

OSHA Instruction CPL 2-2.7 October 30,1972

(a) The opening conference shall be continued with adiscussion of specific health hazard-related information.

(i) Determine the form(s) in which silica arrives at theplant and the approximate sequence of the process in which it is used;request the Safety Data Sheets, if available.

(ii) Obtain plant management statement regardingsafeguards, precautions, protective equipment, and routine procedures usedfor protection of employees in plant operations. Ask about any knownexperience of employee illness or symptoms exhibited or complaints withregard to health matters.

(iii) Obtain complete labeling and placarding information ofchemicals used in the operation,.if any.

(b) The CSHO shall obtain the following additionalinformation either by direct interview, or partial interview, or recordreview. Plant management shall be requested to provide the information notreadily available in a letter to the Area Director.

(i) Monitoring Program. If the plant has an airsampling program or spot samples have been taken at the plant, the-CSHO shallnote:

(A) Collection equipment used, and calibrationrecord if any:

(B) Sampling and analytical methodsemployed;

(C) Frequency of sampling, if performedregularly;

(D) Specified locations of sampling in the plant.if used;

(E) Names of persons who have performed sampling,including names of outside consultants; and

(F) Date of most recent sampling run.Obtain:

((1)) Time of sampling, with respect to workcycle;

((2)) Duration of individual samplingruns;

((3)) Specific sampling locations with respect toprocess and work stations; and

((4)) The sampling results.

(A) What types of medical examination are provided(such as preplacement, annual or special tests for silica exposure) and bywhom, in-house or contract physician? (B) What are the medical protocols orreasons for providing other physical examinations? (C) Where are thephysical examinations conducted?

(A) What types of records are being maintained? (B) When was the particular record keepingstarted?

OSHA Instruction CPL 2-2.7 October 30, 1972 (C) How and where records arekept (such as medical records with employee's personnel record. protectiveequipment records in the warehouse, training program record with the safetyengineer, etc.)? (D) Are heath-related records reviewed and correlated withother available records (air monitoring, training, and maintenance records)?

(iv) Employee Training and Information Program(including new employees).

(A) Who informs the employee about the potentialhealth hazards associated with silica exposure? (B) How often does employeetraining take place, specifically on health hazards of silica? (C) Whatwritten training materials are provided? Include acopy.

(D) Is the employee able to review his or herindividual health-related records? (E) Are emergency procedures taught andpracticed in the plant? Include copies ofprocedures.

(F) Is the function and use of protective equipmentand engineering controls taught? written instructions for the selection anduse of respirators shall be established according to 29 CFR 1910.134(b)(1). Obtain a copy.

(G) Obtain copies of minutes of recent safetymeetings.

(A) What type of locker and lunch facilities areprovided? (B) What type of shower facilities are provided? (C) Whatprocedures are used for encouraging good personal hygiene practices? (vi)Personal Protective Equipment Program.

(A) Are respiratory protective devices provided? Ifso, what type? (B) For abrasive blasting is the type C supplied air, positivepressure, demand type abrasive blasting respirator worn according to 29 CFR1910.94(a) and 30 CFR Part 11? (C) What is the program for repair andmaintenance of all respiratory protective devices? (D) what are the policiesand procedures for issuing personal protective equipment? (E) How is dirtyprotective clothing or equipment cleaned, decontaminated and/or disposed?(vii) Engineering Controls and Related Preventive Maintenance Program.Provide for each system:

OSHA Instruction CPL 2-2.7 October 30,1972

(A) Control system identification andtype;

(B) Design capacity;

(C) Approximate date installed:

(D) Collection system;

(E) Preventive maintenance plan;

(F) System performance measurementprogram.

(A) What is the method used for floor cleaning andthe frequency of it? (B) What is the method of removal of dust from worksurfaces in the plant? (C) What equipment is used in the housekeepingprocess, such as vacuum cleaners, mops, flooding, sweeping, etc.? (D) Isrefuse picked up regularly? (E) Is there an in-plant disposal site ofproduction wastes?

(3) Walk Through Inspection

(a) Prior to the start of the in-plant inspection, the CSHOshall have or wear appropriate protective equipment. The use of personalprotective equipment shall not be less than that required in the plantarea.

(b) Start at the production material receiving point andfollow the production flow. Observe conditions, processes, physical andchemical agents used, worker activities, and existing engineering (c) TheCSHO shall identify and record on plant layout or on a separate sketch thefollowing:

(A) Note the temperature, noise. and dust conditions ineach area.

(B) Note areas adjacent to the silicaprocess.

(C) Record other materials used in the process. Theiruse rate, brand names, preferably the chemical names, and storage areas shallbe noted.

(D) Observe all silica dust accumulations on ceiling,walls, floors and equipment. Note possible sources.

(A) Note number of employees in each area. Note thenumber of workers potentially exposed to silica or other health hazards andobtain their job titles and/or job descriptions.

OSHA Instruction CPL 2-2.7 October 30, 1972

(B) Provide opportunity for conversations with employeesduring inspection concerning knowledge of the hazards, reason for and methodsof protective equipment and engineering controls.

(C) Note permanent work stations with respect to plantprocesses.

(D) Note the use of protective devices. (E) Note theappearance of work clothing (as an indication of potentialexposure).

(A) Note openings (in tunnels or buildings) to externalenvironment and the plant air flow patterns.

(B) Identify all ventilation systems. (C) Notemaintenance work practices on process equipment if there is anopportunity.

(A) Enter sanitary facilities and observe theconditions.

(B) Note adequacy of general housekeepingprocedures.

(C) Note the availability of cleaning equipment andsupplies.

(v) Other.

(A) Photograph potential health hazard areas, equipment,engineering controls and safety hazards and situations which should be a partof the inspection report.

(B) The CSHO shall arrive at conclusions and opinionsdeliberately and slowly. Appearances can be deceiving with respect toairborne concentrations of silica.

(4) Sampling. For sampling purposes, select employees who haveapparent maximum potential exposure and also employees representative ofother work operations. The CSHO shall:

(a) Attach sampling devices to the selected employees.Follow OSHA Standard Methods.

(b) Set the sampling rate at 1.7 liters per minute. (c)Check flow meter setting and sample collection frequently throughout thesampling period.

(d) Minimum total sampling time is 7 hours, unless theoperation time is shorter.

(e) Replace the cartridge with a new one as deemednecessary; do not overload! (f) Perform area sampling to determineeffectiveness of engineering controls (this result shall not be used forcitation).

(g) Keep at least one cassette as a blank, per day ofsampling, expose it to the plant environment and immediately reseal. Airshall not be drawn through the blank.

OSHA Instruction CPL 2-2.7 October 30,1972

(h) dust concentrations shall be determined by gravimetricanalysis in the area office and crystalline silica determinations shall beperformed on the same samples by the laboratory.

(i) In case of potential multiple contaminants (silica,lead, arsenic etc.), samples shall be collected for each suspectedcontaminant separately, according to appropriate OSHA StandardMethod.

(j) Perform measurements and as many noise engineeringcontrol checks as feasible.

(k) Complete other engineering control survey before leavingplant.

(l) Interview employees, and observe for symptoms of healthimpairment.

(m) Arrive at conclusions and opinions slowly. Samplingresults will not be returned instantaneously. Appearances can be deceivingwith respect to airborne concentrations of silica.

(5) Closing Conference

(a) After completing the sampling, surveying all engineeringcontrol systems, and reviewing available plant records, the CSNO shalldiscuss the findings with management and labor representatives together or inseparate meetings.

(b) Management and labor shall be advised of possibleviolations pending results of laboratory analysis ofsamples.

(c) CSHO shall be prepared to discuss the Crystalline Silicaand Abrasive Blasting Guidelines with the employer. Guidelines shall beconsidered as good practice recommendations, notregulations.

6. REPORT

a. The CSHO shall calculate the permissible exposure limit (PEL)of silica samples collected according to the following procedure:

(1) Obtain material identification and per cent silica analysisfrom the laboratory.

(2) Use the formula for gravimetric method provided forrespirable quartz in Table Z-3, 1910.1000, to calculate the PEL. Forcristobalite and tridymite, one half of the value calculated shall be used todetermine PEL.

(3) Example: A respirable dust sample is weighed and thetime-weighted average is calculated to be 3.6 mg/M3. The laboratory reportsthe composition of the dust to be 13% quartz, 8% tridymite and 10%czistobalite. Calculate the permissible exposure limit of eachcomponent.

Quartz: 10 mf/M3 0.66 mg/M3 (PEL) -------- = (13 %+ 2)

-------- (PEL) (8% +2)

OSHA Instruction CPL 2-2.7 October 30, 1972 Cristobalite:

10 mg/M3 X 1/2 = 0.83 mg/M~ X 1/2 = 0.42 mg/M --------- (PEL) (10% + 2)

components exceeds the permissible exposure limits.

b. A complete technical report shall be compiled using allinformation, observations, photographs, and other data collected inaccordance with this program directive. The report shall be concluded withrecommendations, if any, for citations under OSHA standards or general dutyclause and for proposed penalties.

c. The report shall include descriptions of unusual sources orconditions of airborne contaminations.

d. The report shall also include descriptions of exceptional orwell-designed engineering controls observed and surveyed.

7. CITATIONS

Consult Chapter XIII, Section G, of the Field Operations Manual forspecific instructions on the issuance of citations where violations involvingexposure to silica are concerned.

8. EFFECTIVE DATE

This directive is effective immediately and shall be retained untilfurther notice.

Morton Corn Assistant Secretary of Labor

Distribution: A-1 E-1 B-2 HEW-1 C-2 NIOSH Regional ProgramDirectors-1 D-4&5 NACOSH-1 Training Inatitute-4

Office of the Assistant Secretary

Dear Sir:

The nature of work at your establishment in and Health Administration (OSHA)that crystalline silica may be used in your manufacturing process. As youknow, the present permissible exposure limit to weighted averageconcentration for an 8-hour period. If the employee exposure is found to bein excess of the permissible limits, you must implement feasible engineeringor administrative controls or maintain an effective respiratory protectionprogram should such controls be found infeasible. The National Institute forOccupational Safety and Health has recommended that the permissible exposurelimit for silica be lowered to .05 mg/M3, as determined by a full-shiftsample up to a 10-hour working day, 40-hour work week. This recommendationis currently being considered by OSHA.

As an interim measure until such time as a complete standard is promulgatedwe are forwarding herewith recommended guidelines for protection of youremployees against the risk of disease resulting from exposure to silica. These recommendations involve preventive steps of good housekeeping, personalhygiene, medical surveillance, monitoring and measuring of exposure levels,employee training, respirator information and abrasive blasting workpractices which should ensure a reduced health risk for those of youremployees who are involved in such manufacturing processes. The issuance ofthese guidelines does not alter our intention to continue our complianceactivities.

The wide use and multiple applications of silica in our nation's industriescombine to make silica a major occupational health hazard. Therefore,voluntary compliance with the enclosed nonmandatory guidelines would furtherthe overall objective of the Occupational Safety and Health Act - to assureso far as possible, safe and healthful working conditions.

Your cooperation in this matter is greatly appreciated. Protection of youremployees from overexposure to silica is, I am confident, our common goal.

Bert M. Concklin Deputy Assistant Secretary

OSHA Instruction CPL 2-2.7 October 30, 1972

           Guidelines for Control of Occupational Exposure             to Crystalline Silica and Abrasive Blasting

In accordance with the Occupational Safety and Health Administration's(OSHA) standard for air contaminants (29 CFR 1910.1000), employee exposure toairborne crystalline silica shall not exceed an 8-hour time-weighted averagelimit (variable) as stated in 29 CFR 1910.1000, Table Z-3. or a limit set bya state agency whenever a state-administered Occupational Safety and HealthPlan is in effect.

The first mandatory requirement is that employee exposure be eliminatedthrough the implementation of feasible engineering controls. After all suchcontrols are implemented and they do not control to the permissible exposurelimit, each employer must rotate its employees to the extent possible inorder to reduce exposure. Only when all engineering or administrativecontrols have been implemented, and the level of respirable silica stillexceeds permissible exposure limits, may an employer rely on a respiratorprogram pursuant to the mandatory requirements of 1910.134. Generally whereworking conditions or other practices constitute recognized hazards likely tocause death or serious physical harm, they must be corrected pursuant toSection 5(a)(1) of the Occupational Safety and Health Act.

In addition to these mandatory requirements, the National Institute ofOccupational Safety and Health has recommended that the limit be lowered to0.05 mg/M3, as determined by a full-shift sample up to a 10-hour working day,40-hour work week. This recommendation is currently being considered byOSHA. Pending such consideration, the following recommendations are made toensure that employee exposure to respirable silica is controlled to thepermissible exposure limit. For these guidelines. silica means crystallinesilica.

1. MONITORING

a. Each employer who has a place of employment in which silica isoccupationally produced, reacted, released, packaged, repackaged,transported, stored, handled, or used should inspect each workplace and workoperation to determine if any employee may be exposed to silica at or abovethe permissible exposure limits. Indicators that an evaluation of employeeexposure should be undertaken would include:

(i) Any information or observations which would indicateemployee exposure to silica or other substances;

(ii) Any measurement of airborne silica:

(iii) Any employee complaints of symptoms which may beattributable to exposure to silica or other substances;

(iv) Any production, process, or control change which may resultin an increase in the airborne concentration of silica, or whenever theemployer has any other reason to suspect an increase in the airborneconcentrations of silica.

b. Air Monitoring

(i) Employee exposure measurements should represent the actualbreathing zone exposure conditions for each employee. Anyappropriate

OSHA Instruction CPL 2-2.7 October 30,1972

combination of long-term or short-term respirable samples wouldbe acceptable, but total sampling time may not be less than 7 hours. In caseof abrasive blasting operations, substances other than silica should besampled and analyzed.

(ii) Accuracy of Measurement. The method of monitoring and analysisshould have an accuracy of not less than plus or minus 25% for concentrationsof airborne silica equal to or greater than the permissible exposure limit. (One method meeting this accuracy requirement is available in the "NIOSHManual of Analytical Methods," Government Printing Office Stock No.1733-00041) (iii) Frequency of Monitoring. Where the employer has determinedthat employees are exposed to silica or other substances in excess of thepermissible exposure limit, monitoring should be-repeatedquarterly.

2. MEDICAL SURVEILLANCE

Each employer should institute a medical surveillance program forall employees who are or will be exposed to airborne concentrations of silicaor other substances above the permissible exposure limit. The employershould provide each employee with an opportunity for a medical examinationperformed by or under the supervision of a licensed physician and should beprovided during the employee's normal working hours:without cost to theemployee.

a. Medical Examination

(i) Each employer should provide a medical examination whichincludes a complete medical history and physical examination, an annual chestroentgenogram (x-ray) and pulmonary function tests to each employee exposedto silica in excess of the permissible exposure limits. In the abrasiveblasting trade, attention should be paid to potential scarring ofcornea.

(a) A chest roentgenogram (posteroanterior 14" by 17" or 14"by 14") classified according to the 1971 ILO International Classification ofRadiographs of Pneumoconioses. [ILO U/C International Classification ofRadiographs of Pneumoconioses 1971, Occupational Safety and Health Series 22(rev) Geneva, International Labor Office, 19721.

(b) Pulmonary function tests including forced vital capacity(FVC) and forced expiratory volume at one second (FEV 1) to provide abaseline for evaluation of pulmonary function and to help determine theadvisability of the workers using negative- or positive-pressure respirators. It is recognized that providing such medical examination and record keepingof medical data may be difficult for those abrasive blasting establishmentsemploying transient workers.

OSHA Instruction CPL 2-2.7 October 30, 1972

(ii) Medical examinations should also be made available: (a) Toemployees prior to their assignment to areas in which airborne concentrationsof silica are above the permissible exposure limit;

(b) At least.annually for each employee exposed to airborneconcentrations of silica above the permissible exposure limit at any timeduring the preceding six months;

(c) Immediately, upon notification by the employee that theemployee has developed signs or symptoms commonly associated with chronicexposure to silica.

(iii) Where medical examinations are performed, the employershould provide the examining physician with the followinginformation:

(a) The reason for the medical examination requested;

(b) A description of the affected employee's duties as theyrelate to the employee's exposure;

(c) A description of any personal protective equipment usedor to be used;

(d) The results of the employee's exposure measurements, ifavailable;

(e) The employee's anticipated or estimated exposurelevel;

(f) Upon request of the physician, information concerningprevious medical examination of the affected employee.

b. Physician's Written Opinion

(i) The employer should obtain and furnish the employ with awritten opinion from the examining physician containing thefollowing:

(a) The signs or symptoms of silica exposure manifested by theemployee, if any;

(b) A report on the findings of the chest roentgenogram andpulmonary function tests;

(c) The physician's opinion as to whether the employee has anydetected medical condition which would place the employee at increased riskof material impairment to the employee's health from exposure to silica orother substances or would directly or indirectly aggravate any detectedmedical condition;

(d) Any recommended limitation upon the employee's exposure tosilica or other substances or upon the use of personal protective equipmentand respirators; and (e) A statement that the employee has been informed bythe physician of any medical condition which requires further examination ortreatment.

(ii) The written opinion obtained by the employer should not revealspecific findings or diagnoses unrelated to occupational exposure to silicaor other substances.

(iii) If the employer determines, on the basis of the physician'swritten opinion, that any employee's health would be materially impaired bymaintaining the existing exposure to silica or other substances,

OSHA Instruction CPL 2-2.7 October 30,1972

the employer should place specific limitations, based on thephysician's written opinion, on the employee's continued exposure to silicaor other substances.

3. TRAINING

a. Each employee who may be potentially exposed to silica or othersubstances should be apprised at the beginning of his or her employment orassignment to such an exposure area of the hazards, relevant symptoms.appropriate emergency procedures, and proper conditions and precautions forsafe use or exposure.

b. Instruct affected employees to advise the employer of thedevelopment of the signs and symptoms of prolonged exposure to silica andother substances.

c. Inform employees of the specific nature of operations which couldresult in exposure to silica or other substances above the permissibleexposure limits, as well as safe work practices for the handling, use, orrelease of the silica and the types and function of engineeringcontrols.

d. Instruct employees in proper housekeeping practices. e. Instructemployees as to the purpose, proper use, and limitations ofrespirators.

f. Provide employees with a description of, and explain the purposesfor, the medical surveillance program.

g. Inform employees where written procedures and health informationare available on the premises.

h. Advise employees of the increased risk of impaired health due tothe combination of smoking and silica dust exposure.

4. PERSONAL PROTECTIVE DEVICES

a. Personal Protective Devices Program. Engineering controls shallbe used to maintain silica dust exposures below the prescribed limit. Whenthe limits of exposure to silica cannot be met by limiting the concentrationsof silica in the work environment by engineering and administrative controls,an employer must utilize a program of respiratory protection to protect everyemployee exposed.

b. Respirator Selection and Usage

(i) The employer should select and provide an appropriaterespirator from the table on the next page. When abrasive blasting is done,the type C supplied-air, positive pressure, demand type abrasive blastingrespirator shall be worn according to 29 CFR 1910.94(a) and 30 CFR Part11.

(ii) Employees experiencing frequent and continuous breathingdifficulty while using respirators should be evaluated by a physician todetermine the ability of the worker to wear a respirator.

(iii) A respiratory protective program meeting the requirementsof 29 CFR 1910.134 shall be established and enforced by theemployer.

(iv) A respirator specified for use in higher concentrations ofairborne silica may be used in atmospheres of lowerconcentrations.

OSHA Instruction CPL 2-2.7 October 30, 1972 Recommendations for RespiratorUsage at Airborne Silica Concentrations Above the Permissible Exposure Limit

_____________________________________________________________________

|Concentrations of | Respirator Type* ||Airborne Silica | | |inMultiples of | | |theStandard | ||____________________|______________________________________________| |Lessthan or | Single use (valveless type) dust respirator.| |Equal to 5x | ||____________________|______________________________________________| |Lessthan or | Quarter or half mask respirator with | |equal to 10x | replaceable dust filter or single use (with | | | valve) dust respirator. | | | | | | Type C,demand type (negative pressure), | | | with quarter orhalf mask facepiece. ||____________________|______________________________________________| |Lessthan or | Full faceplate respirator with replaceable | |equal to100x | dust filter. | | | | | | Type C, supplied-air respirator, demand type| | | (negative pressure), with full facepiece. ||____________________|______________________________________________| |Lessthan or | Powered air-purifying (positive pressure) | |equal to200x | respirator, with replaceable applicable | | | filter.** ||____________________|______________________________________________||Greater than 200x | Type C, supplied-air respirator, continuous | | | flow type (positive pressure), with full | | | Facepiece, hood, or helmet. ||____________________|______________________________________________|

 *Where a variance has been obtained for abrasive blasting with  silica sand use only Type C continuous flow, supplied air  respirator with hood or helmet.

**An alternative is to select the standard high efficiency filter

which must be at least 99.97% efficient against 0.3 um dioctylphthalate (DOP).

OSHA Instruction CPL 2-2.7 October 30,1978

(v) Employees shall be given instructions on the use ofrespirators assigned to them, on cleaning respirators. and on testing forleakage.

(vi) When employees are exposed to other toxic substances inaddition to silica, appropriate combinations of respiratory protection shallbe provided.

c. Only those respiratory protection devices shall be used whichhave a "Tested and Certified" number issued by the National Institute ofOccupational Safety and Health to the manufacturer of the device.

d. There should be an established in-plant procedure and means andfacilities provided to issue respiratory protective equipment, to return usedcontaminated equipment, to decontaminate and disinfect the equipment, and torepair or exchange damaged equipment. Record keeping of these activities ismandatory.

5. PROTECTIVE CLOTHING

Where exposure to airborne silica or other substances is above thepermissible exposure limit, work clothing should be vacuumed before removalunless it is wet. Clothes should not be cleaned by blowing orshaking.

6. HOUSEKEEPING

a. All exposed surfaces should be maintained free of accumulation ofsilica dust, which, if dispersed, would result in airborne concentrations inexcess of the permissible exposure limit.

b. Dry sweeping and the use of compressed air for the cleaning offloors and other surfaces should be prohibited. If vacuuming is used theexhaust air should be properly filtered to prevent generation of airbornerespirable silica concentrations. Gentle washdown of surfaces is preferableif practical.

c. Emphasis should be placed upon preventive maintenance and repairof equipment. proper storage of dust producing materials, and collection ofdusts containing silica. Sanitation shall meet the requirements of 29 CFR1910.141.

7. PERSONAL HYGIENE FACILITIES AND PRACTICES

a. All food, beverages, tobacco products, nonfood chewing products.and unapplied cosmetics should be discouraged in work areas.

b. Employers shall provide an adequate number of lavatories,maintained and provided with soap and towels.

c. Where employees wear protective clothing or equipment, or both,in-plant change rooms should be provided in accordance with1910.141(e).

OSHA Instruction CPL 2-2.7 October 30, 1978

8. ENGINEERING CONTROLS

a. Dust Suppression. Moisture, mists, fogs, etc.,should be addedwhere such addition can substantially reduce the exposure to airbornerespirable silica dust.

b. Ventilation. Where a local exhaust ventilation and collectionsystem is used in a building, it should be designed and maintained to preventthe accumulation or recirculation of airborne silica dust into the workplace.The system should be inspected periodically. Adequate measures should betaken to ensure that any discharge will not produce health hazards to theoutside environment.

c. Additional Control Measures. When mobile equipment is operatedin areas of potential silica exposure, engineering controls should beprovided to protect the operator from such exposure.

9. ITINERANT WORK

a. when employees are exposed to airborne silica at temporary worksites away from the plant, emphasis should be placed on respiratoryprotection, protective clothing, portable engineering controls, andprovisions for personal hygiene and sanitation. Training of employees shouldbe provided to protect them as well as others from airborne silica dustexposure to the extent practical.

10. ABRASIVE BLASTING

a. Introduction

(i) Consult standards listed in 29 CFR 1910.94(a). (ii) Thenature of dust generated in any abrasive blasting process is the combinationof the fragmentation of blasting media and the material dislodged from thesurface treated. Where fragmentable abrasives such as sand, shells, alumina,glass bead or metal shot is used, or where a fragmentable surface such assand casting, a painted or scaly surface, or masonry is blasted, the airbornedust generated will vary in particle size and chemical composition. Noiseassociated-with abrasive blasting operations is also a significant hazard. Heat stress may also be a potential hazard.

(iii) Engineering controls for noise and dust should beconsidered even if they cannot reduce the exposures to permissible exposurelimits but will significantly reduce noise and dust exposure to theemployees.

(iv) Maximum respiratory protection should be provided whensilica sand is used as the abrasive agent, or sand castings are cleaned byblasting.

(v) All production and control systems used in a stationaryabrasive blasting process should be designed or maintained to prevent escapeof airborne dust or aerosols in the work environment and to assure control ofthe abrasive agents.

OSHA Instruction CPL 2-2.7 October 30,1978

b. General

(i) Selection and maintenance of protective equipment.

(a) Refer to the table on page 5 to select appropriaterespiratory protective equipment.

(b) Air-supplied helmets, ricochet hoods. dust respirators,ear muffs and safety glasses should be an individual issue item, identifiedwith and used by one employee only. Such equipment should be reissued toanother employee only after complete cleaning, repair anddecontamination.

(c) Means should be provided to vacuum, clean and store airsupplied respiratory equipment after each shift of use. Storage should be ina clean enclosure such as locker, footlocker, or plastic container. Theemployees should be trained to maintain the issued equipment in cleancondition for his own protection.

(d) Replacement of prescription or plane safety glassesshould be made if multiple pitting or etching is visible in the center of thelenses.

(e) Replacement of faceplates in air-supplied helmets,ricochet hoods. or full face masks should take place when a side-on lightsource produces obscuring visible reflections and glare from the etched spotsand pit holes in the faceplate. Mylar coating, or similar transparentplastic material, is recommended to protect the glass or plasticfaceplate.

(f) Length of air hose may not be altered from themanufacturer's specifications.

(g) The condition of protective equipment should be checkeddaily by the employee. Rips, tears, and openings which expose skin toabrasive agents, should be mended. Functional tests for leaks, properrespiration, and good connections should be performed on the complete airsupply system.

(ii) Air supply - portable.

(a) The breathable air supplied to the helmet or ricochethood should be drawn from an oil and carbon monoxide free air compressor. Initinerant work, it should be located upwind from the main air compressor toprevent entry of combustion gases into breathable air.

(b) Breathable air supply system should be equipped, ifpossible, with audible alarm at the helmet or hood to warn the user of lowair pressure.

(iii) Hearing protection. Suitable hearing protection,providing at least 20 dBA reduction in noise level experienced, should beworn inside the helmet or ricochet hood unless hearing protection is anintegral part of such helmet or hood.

(iv) Heat stress. Cooling of breathable air, supplied to theblasting helmets or ricochet hoods. should be considered depending on seasonand exposure of the employee to heat sources.

OSHA Instruction CPL 2-2.7 October 30, 1978

c. Work Practices

(i) Indoors blasting cabinets and glove boxes.

(a) Negative pressure should be maintained inside duringblasting.

(b) The enclosure should be as complete as practical. (c)When the inside of the blasting cabinet is cleaned, respiratory protectionshould be utilized.

(d) If blasting creates excessive noise. a change of nozzleconfiguration or application of noise control materials to the enclosureshould be considered.

(e) Cabinets should be maintained in good repair includingthe presence of gaskets.

(ii) In-plant blasting rooms.

(a) Negative pressure should be maintained inside duringblasting. The room should have exhaust capacity of one air change perminute.

(b) Minimum recommended protective equipment of an abrasiveblaster working inside a blasting room, in the open, in enclosed space, oroutdoors is: safety boots or toe guards;. durable coveralls, closeable atexists, ankles and other openings to prevent entry of abrasive dust andrubbing of such; respiratory, eye, and hearing protection; and gauntletgloves.

(c) If abrasive blasting is automated, the room should notbe entered before at least six air changes have occurred, as respirable-sizedust particles stay airborne for a considerable length oftime.

(d) In the room, a cleanup method other than broom sweepingor compressed air blowing should be used to collect the abrasive agent afterblasting (e.g. vacuum cleaning). If the blasting agent is removed manually.respiratory protection should be used.

(iii) In-plant work area.

(a) If occasional but regular abrasive blasting must beperformed inside a building without enclosures, respiratory protection shouldbe provided for all employees in the area. Portable engineering controldevices should be used at the location to collect all of the used abrasiveagent as it is applied.

(b) When airborne abrasive blasting dust becomessufficiently heavy in an area to cause a temporary safety hazard by reducedvisibility, or a marked discomfort to the unprotected employees not engagedin abrasive blasting, such operations in the affected area should bediscontinued until the airborne dust is removed by exhaust ventilation andthe settled dust has been removed from the horizontal surfaces in the area. If such operations have to continue, appropriate respiratory protectionshould be provided to those employees remaining in the area, providedvisibility is adequate.

(c) If wet blasting is employed, airborne dust hazard mayexist after evaporation of water.

OSHA Instruction CPL 2-2.7 October 30,1978

(iv) Confined space. A confined space is a compartment or tankor similar enclosed space in which abrasive blasting, or a preexistingatmosphere. may cause the employee to be overcome by conditions hazardous tolife and where egress may be difficult if normal body functions areimpaired.

(a) Before starting work, open all access hatches, trapdoors, etc., to aid natural ventilation. Mechanical ventilation should beused, picking up air at the furthest point away from the opening if naturalventilation will not cause a complete air change. Consider the otherpotentially hazardous materials present. such as solvents, crusts ofchemicals, or old paint, with regard to explosion or fire potential whenblasted.

(b) A "buddy system" should be used - for each employeeinside a confined space, another employee should be available to assist in apotential emergency.

(c) For respiratory protection, a self-contained breathingapparatus or air-supplied hood should be utilized.

(d) Adequate lighting that meets the requirements of theNational Electrical Code, article 502, should beprovided.

(e) If the space is mechanically ventilated, means should beprovided to collect dust before release to the openatmosphere.

(v) Outdoors. (a) Blaster should be protected in a mannerequivalent to that mentioned in 29 CFR 1910.94(a)(5).

(b) The pot man should wear the same protective devicesavailable to the blaster, depending on the distance and wind conditionsrelative to the blasting location.

(c) Prudent care should be taken to prevent the dust cloudfrom spreading to other work areas.

(d) Hearing protection and respiratory protection should beavailable to all other employees in the area if their presence isrequired.

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