HETA #2000-0226-2890 Foeste Masonry Cape Giarardeau ... · HETA #2000-0226-2890 Foeste Masonry Cape...

NIOSH HEALTH HAZARD EVALUATION REPORT:

DEPARTMENT OF HEALTH AND HUMAN SERVICESCenters for Disease Control and Prevention

National Institute for Occupational Safety and Health

HETA #2000-0226-2890Foeste MasonryCape Giarardeau, Missouri

July 2001

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved. Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports



applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved. Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

http://www.cdc.gov/niosh/hhe/reports

ii

PREFACE

Under the authority of Section 20(a)(6) of the Occupational Safety and Health Act of 1970, 29 U.S.C.669(a)(6), the National Institute for Occupational Safety and Health (NIOSH) conducts fieldinvestigations of possible health hazards in the workplace upon request. These investigations, which require a written request from any employer or authorized representative of employees, are undertaken todetermine whether any substance normally found in the place of employment has potentially toxic effectsin such concentrations as used or found. NIOSH also provides, upon request, technical and consultativeassistance to Federal, State, and local agencies; labor; industry; and other groups or individuals to controloccupational health hazards and to prevent related trauma and disease. Mention of company names orproducts does not constitute endorsement by NIOSH.

ACKNOWLEDGMENTS AND AVAILABILITY OF REPORT

This report was prepared by Daniel Yereb and Paul Hewett, of the Respiratory Disease HazardEvaluation and Technical Assistance Program, Field Studies Branch (FSB), Division of RespiratoryDisease Studies (DRDS). Other DRDS staff were involved. Analytical support was provided by DataChem Laboratories. Desktop publishing was performed by Terry Rooney.

Copies of this report have been sent to employee and management representatives and the OSHARegional Office. This report is not copyrighted and may be freely reproduced. Single copies of thisreport will be available for a period of three years from the date of this report. To expedite your request,include a self-addressed mailing label along with your written request to:

NIOSH Publications Office4676 Columbia ParkwayCincinnati, Ohio 45226

800-356-4674

After this time, copies may be purchased from the National Technical Information Service (NTIS) at5825 Port Royal Road, Springfield, Virginia 22161. Information regarding the NTIS stock number maybe obtained from the NIOSH Publications Office at the Cincinnati address.

For the purpose of informing affected employees, copies of this report shall beposted by the employer in a prominent place accessible to the employees for aperiod of 30 calendar days.

iii

Health Hazard Evaluation Report 2000-0226Foeste Masonry

Cape Girardeau, MissouriJuly 2001

Daniel YerebPaul Hewett

SUMMARY

Foeste masonry recently received an OSHA citation for overexposure of workers to crystalline silica during thedry cutting of brick. Foeste subsequently purchased several brick/block cutoff saws equipped with water dustsuppression. Until Foeste could show that exposures were adequately controlled, Foeste was required byOSHA to enroll the operators in a respiratory protection program (fit testing and use of half mask, cartridgerespirators). On April 3, 2000, Foeste Masonry requested a Health Hazard Evaluation (HHE) to assess theeffectiveness of wet dust suppression during the cutting of brick and block. On May 8, 2000, NIOSHinvestigators met with Foeste representatives to discuss sampling procedures for collecting airborne dustsamples. Environmental measurements of airborne particulate were obtained on May 9 - 10, 2000.

NIOSH investigators determined that dry cutting can lead to intense exposures to silica dust. Suchexposures are likely to be very hazardous to workers operating the saws and working in their vicinity.NIOSH recommends that wet cutting be used when ever possible. The sampling undertaken in thisstudy indicates that wet cutting, undertaken using the manufacturer’s guidelines, generally leads toexposures to silica dust below the OSHA PEL. It is recommended that saw operators continue to wearat least a NIOSH-approved, disposable respirator, especially when wet cutting for two hours or more. If dry cutting brick or block is necessitated by the building design a Powered Air Purifying Respirator(PAPR) should be worn and the cutting time should be limited. Routine evaluation of dust exposuresis desirable to ensure that the workers are adequately protected , especially for brick or block of highsilica content.

Keywords: Silica, Quartz, Silicosis

TABLE OF CONTENTS

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Acknowledgments and Availability of Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Tables and Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Health Hazard Evaluation Report No. 2000-0226 Page 1

INTRODUCTION

On March 13, 2000, the safety manager of FoesteMasonry contacted NIOSH by telephone to discussa dust control problem. Foeste Masonry hadreceived an OSHA citation for overexposure ofworkers to crystalline silica during the dry cutting ofbrick. Foeste had purchased several brick/blockcutoff saws equipped with water dust suppression,but was required by OSHA to enroll the operators ina respiratory protection program (fit testing and useof half mask, cartridge respirators) until Foeste couldshow that exposures were adequately controlled. OnApril 3, 2000, NIOSH received a formal requestfrom Foeste masonry to conduct a Health HazardEvaluation (HHE) to assess the effectiveness of wetdust suppression during the cutting of brick andblock. On May 8, 2000, NIOSH investigators met withFoeste representatives and discussed the scope of theinvestigation, reviewed existing environmental andadministrative controls, conducted a walk-through ofthe facilities, and examined the equipment. Airbornerespirable dust samples using wet and dry cuttingmethods were collected on May 9 - 10, 2000.

This report presents the results from the industrialhygiene survey conducted May 9 - 10, 2000. Theeffectiveness of using wet dust suppression whilecutting brick and block is addressed. In addition,recommendations for preventing exposure tocrystalline silica are presented.

BACKGROUND

Foeste Masonry undertakes masonry work forcommercial construction sites. The site of concern inthis report is owned by the county of CapeGirardeau, Missouri. The county had contractedwith Foeste Masonry to build a 21,000 square feetaddition to the Cape Girardeau Justice Center. Theinterior walls and building envelope wereconstructed of block while the building facade wascovered with brick. In addition to the masonry work,electricians, pipe-fitters, plumbers, and HVACcontractors were on site. As a common practice inthe construction industry, plumbers, electricians,HVAC contractors, and others perform “rough-in

work” prior to the masonry work. As a result, thereis considerable cutting of block and brick in order tocover up the rough-in work. Some constructioncontracts either forbid wet cutting (wet brick, blockor tile may not set up properly with some adhesives)or require the brick/block to be dried several hoursprior to use. Brick or block drying prior to use is notalways practical given the nature of masonry work.

Foeste Masonry was cited under the OSHAPermissible Exposure Limit (PEL) for dustscontaining crystalline silica. This PEL (see theappendix) is calculated using a formula that reflectsthe combination of two components: (a) level ofrespirable dust (i.e., dust small enough to penetrate tothe air exchange regions of the lung where clearanceand detoxification are difficult), and (b) thepercentage of crystalline silica in the dust.

METHODS

On May 9-10, 2000, NIOSH investigators collectedboth personal breathing zone and area airborne dustsamples during dry cutting (Figure 1) and wet cutting(Figure 2) of brick and block at the Foeste Masonryconstruction site in Cape Girardeau, Missouri.

Thirty-three area and personal airborne dust sampleswere collected. Sampling was done using two tofour industrial hygiene sampling arrays that wereplaced around the cutting stations, at approximatelychest height and 4 to 5 feet from the saw. Eachsampling array contained two cyclones, oneimpactor, and two direct reading instruments (forrespirable dust). Three video cameras werepositioned around the cutting stations to videotapethe cutting cycle. Sample times ranged from 10 to 76minutes.

Respirable Dust Containing Crystalline Silica

Area and personal samples of respirable dust werecollected and analyzed using NIOSH Method 7500:Silica, Crystalline by X-ray Diffraction (XRD).1

Each dust sample was collected with a battery-powered sampling pump calibrated at 1.7 liters perminute (L/min), 10 mm nylon cyclone followed by a37-mm diameter polyvinyl chloride (PVC) filter.

Health Hazard Evaluation Report No. 2000-0226

The nylon cyclone removed the larger, non-respirable particles from the air stream prior topassing through the filter. The filters were weighedprior to the survey. After sampling, each filter wasagain weighed so that the mass and concentration ofcollected dust could be determined. If the weightgain of the filter exceeded 0.03 mg (the limit ofdetection for silica in NIOSH method 7500), thefilter was analyzed for crystalline silica (quartz).

Particle Size Distributions

The particle size distribution for dust was measuredusing Andersen Personal Cascade Impactors, Model298. Prior to sampling, 34-mm diameter Mylar®

substrates were silicone-coated and pre-weighed byNIOSH. Each sample was collected using a battery-powered sampling pump calibrated at 2.0 liters perminute (L/min). Thirty-four-mm diameter polyvinylchloride (PVC) filters were used as a backup to theMylar® substrate to prevent leaching of the siliconeto the stages of the impactor. Substrates were post-weighed to measure the amount of particulatecollected. The impactor data were collected as partof ongoing NIOSH research in aerosol particulateand will be reported when that research is complete.

Real-time Dust Measurements and VideoRecordings

Respirable dust real-time measurements were madeusing the Personal DataRAM (MIE) with data-logging capabilities. The DataRAM was calibratedto 1-second sampling intervals. Simultaneous videorecordings of each cutting cycle were collected andmerged with real-time dust measurements. Video-overlays were produced to access peak exposuresduring cutting. Internal clocks in the DataRAM andvideo cameras were synchronized to the second.Video tape recordings with real-time overlay of theairborne dust concentration were prepared for twoone minute segments illustrating dry and wet sawingoperations. This was done to access peak exposuresduring the sawing process and to provide informationon other variables such as wind direction that canaffect the concentration of airborne dust in the workarea.

RESULTS

The results obtained in this study illustrate thatexposures to airborne dust can occur during dry andwet cutting of block and brick. They provide apowerful demonstration of the potential risks ofundertaking dry cutting, and a clear indication of themerits of wet cutting. Note, however, that the dataare snap shots in time and may not represent the fullrange of exposures that may be experienced duringdry and wet cutting of all types of block and brickunder all conditions.

Respirable Dust Containing Silica

Table 1 summarizes the airborne dust concentrationsand silica concentrations measured in the work areasand in the breathing zone of the workers. Table 1also provides the value of the OSHA PEL that wascalculated based on the measured silica content ofthe dust. The silica percentage in the area samplesduring dry cutting ranged from 5.7% to 14.3 % forthe brick and 4.7% to 7.9% for the block. The massof respirable dust collected in the general work areaduring wet sampling was too low to permit anevaluation of the silica content of the dust.

The silica percentage in the personal samples was13.3% for the sample taken during dry cutting ofbrick, 4.2% and 12.7% for the two samples takenduring dry cutting of block, and were below the limitof detection and 12.5% for the two samples takenduring wet cutting of block.

Dry Cutting Brick and Block

The eleven area respirable dust concentrations fordry cutting brick and block ranged from 3.4 to 150mg/m³, with a mean of 56 mg/m³. The five personalrespirable dust samples concentrations ranged from27 to 125 mg/m³, with a mean 53 mg/m3 .

Wet Cutting Brick and Block

During wet cutting, fifteen of the seventeen arearespirable dust concentrations were non-detectable,and two samples had a concentration of 0.3 mg/m³.The respirable dust concentrations measured on thetwo personal air samples were 0.3 mg/m³ and 0.7

mg/m³.


Real Time Dust Measurement and VideoMonitoring

Figures 3 and 4 illustrate the temporal change in airconcentration during wet and dry cutting. Asexpected, the concentration were high while cuttingwas underway and lower during the interval betweencuts. Similar temporal variations were seen duringboth dry and wet operations. However, on average,the respirable dust concentration during wet cuttingwas 154 times lower than during dry cutting (Figure5).

Figures 6 - 9 show the position of the worker, theaverage wind direction (if outdoors), and the dustconcentrations at the worker location and the areasampling locations. Dust exposures were generallylow when the worker was wet cutting, even whileinside the building with minimal wind to disperse thedust (Figure 6). Outdoors, the concentration of dustat the worker’s location was strongly influenced bythe relative position of the worker and the sawrelative to the direction of the wind, as would beexpected. Locating the worker downwind of thesaw (Figure 7) caused a four to five fold higherrespirable dust exposure compared to locating theworker upwind of the saw (Figure 8). Anintermediate concentration was observed when thewind was blowing from the side (Figure 9).

DISCUSSION

Most masonry materials contain crystalline silica.Crystalline silica can cause a disabling and oftenfatal lung disease known as silicosis. Chronicsilicosis develops after prolonged exposure torelatively low concentrations of silica-containingdusts. Accelerated silicosis can occur after just fiveor ten years exposure to higher concentrations.Acute silicosis can develop after exposure to extremeconcentrations for periods of years, or only weeks.Silicosis is irreversible. Cessation of exposureneither leads to remission, nor halts the diseaseprocess. Typically, the disease is neither clinicallynor functionally apparent until years after theexposures. For these reasons, it is criticallyimportant that a control system or program be inplace to prevent recurring high exposures. Thissystem can consist of engineering controls (e.g., wetcutting, or cutoff saws equipped with local exhaust

ventilation), work practices (e.g., positioning thecutoff process to take advantage of wind and naturaldilution ventilation), and personal protectiveequipment. The order of preference is: engineeringcontrols, work practices, and last, personal protectiveequipment.

It is clear from the results presented above that drycutting should be avoided because of the risk it posesto both the operator and nearby workers. At dry-cutting dust levels, it takes only minutes to exceedthe OSHA crystalline silica (quartz) PermissibleExposure Limit (PEL). In contrast, wet cuttingresults in a drastic reduction in exposures to dust. Asa result, it may be possible to perform wet cutting forhours without exceeding the OSHA PEL.

Of the two personal samples taken during wetcutting, the amount of silica on one was less than thelimit of detection, while on the other the amountdetected was at the limit of detection (LOD) of0.01mg. The calculated concentration for the latterwas 0.1 mg/m³. The sample duration was64 minutes. If cutting had continued at this rate fora full work shift, this concentration would have beenabove the NIOSH REL (recommended exposurelimit) for silica dust (although it would have fallenbelow the OSHA PEL).4 If, however, cutting waslimited to four hours out of the work shift, and ifthere were zero exposures throughout the remainderof the shift, the estimated full-shift, respirable silica(quartz) concentration would have been 0.05 mg/m³.This predicted concentration is equal to the NIOSHrecommended exposure limit (0.05 mg/m³) forcrystalline silica. Hence, based on theseassumptions, wet cutting would protect workers fromover-exposure if they cut for less than four hours.However, as noted above, additional data would beneeded to draw definitive conclusions for the safetyof wet cutting under all conditions.

The results in this HHE are consistent with theconclusions of other published reports. For example,information on the effectiveness of dust controls forcut-off saws was recently published in a UnitedKingdom professional journal.2 The authors foundthat masonry cutting without controls can generateextremely high exposures of airborne dust. Theyalso showed that reductions in exposure of upwardsof 95% can be achieved with either wet cutting orcutting with local exhaust ventilation. Note,


however, that a U.S. study of silica exposures inconcrete workers and masons reported that “the useof water should not be relied upon as a complete

method of control in all instances.”3

The results in this HHE apply specifically to thebrick and block used at that site. Different types orsources of brick or block may have greaterpercentages of silica, resulting in greater exposuresto crystalline silica when cutting for similar lengthsof time. Routine measurements should be made toassure that workers are being protected.

CONCLUSIONS

Based on the results of this survey the followingconclusions are made.

• Workers in close proximity to dry cuttingoperations are exposed to extremely highconcentrations of airborne dust, of which asubstantial proportion is silica dust.

• These levels are potentially hazardous toworkers’ health.

• When dry cutting, the cutting time forwhich exposure limits are exceeded may beas short as minutes as compared to hoursfor wet cutting.

• Wet cutting substantially reduces workerexposures to silica dust but does not entirelyeliminate them.

RECOMMENDATIONS

The data collected by NIOSH suggest that, if themanufacturer’s guidelines for using water whileoperating the saws are followed, Foeste masonry willlikely be in compliance with OSHA standards andtherefore no longer required to wear the half-maskrespirator. However, there is an indication that long-term (full-shift) wet cutting may lead to the NIOSHREL being exceeded. Given this, and consideringthat this evaluation is limited in scope, NIOSHrecommends that cutoff saw operators continue

wearing at least a NIOSH-approved, disposablerespirator, especially when cutting for two hours ormore. The company should strive to reduceexposures below the NIOSH RecommendedExposure Limits (REL).5

NIOSH recommends the following:

• Avoid dry cutting.

• Use engineered controls such as wet cuttingand/or saws with local dust captureattachments.

• Use administrative controls such aspositioning the worker upwind of the saw orlimiting the cutting time, as needed.

• Clean saws to prevent dust from being re-suspended from saw surfaces.

• Replace worn saw blades to prevent thegeneration of finer airborne dust.

• If dry cutting of brick or block is required,use appropriate respiratory protection, suchas a Powered Air Purifying Respirator

(PAPR) and limit the cutting time.

• Implement an ongoing dust measurementprogram to evaluate the effectiveness of theexposure control plan and demonstrate thatthe controls are sufficient to prevent over-exposure under all applicable conditions(i.e., types of brick and block,environmental conditions, and durations ofcutting, etc).

REFERENCES

1. NIOSH Manual of Analytical Methods(NMAM®) 4th ed. DHHS (NIOSH)Publication 94-113 (August, 1994).


2. Thorpe, A., Ritchie, A.S., Gibson, M.J., andBrown, R.C.: Measurements of theEffectiveness of Dust Control on Cut-offSaws Used in the Construction Industry.Annals of Occupational Hygiene 43:443-456 (1999).

3. Lofgren, D.J.: Silica Exposure for ConcreteWorkers and Masons. AppliedOccupational and Environmental Hygiene8:832-836 (1993).

4. CFR [1999]. 29 CFR 1910.1000. Code ofFederal Regulations. Washington, DC: U.S.Government Printing Office, Office of theFederal Register.

5. NIOSH [1992]. NIOSH recommendationsfor occupational safety and health:compendium of policy documents andstatements. Cincinnati, OH: U.S.Department of Health and Human Services,Public Health Service, Centers for DiseaseControl, National Institute for OccupationalSafety and Health, DHHS (NIOSH)Publication No. 92-100.


Figure 1. Video snapshot during dry sawing of brick. A powered air purifying respirator is being worn bythe worker. An air sampling station is located on a tripod to the left of the worker.

Figure 2. Video snapshot during wet sawing of block. A simple face shield is being worn by the worker forsplash protection. Note the personal impactor air sampler on the left lapel of the worker.


Figure 3. Typical dust concentration as a function of time during dry cutting of brick. Note the significantchange in concentration during the course of the cutting operation.

'" .

.. 400

c 300

U) 200

!: 100

500

Time (see)

100 120

Figure 4. Tyical dust concentration as a function of tie during wet cuttng of block. Smal changes in

concentrtion are seen uring the wet cuttng proes but the overall dust concentrtion is very low.

uation Report No. 2000226 Page 9

100

Dry Wet

Figure 5. Comparison of the average personal dust concentrtion during dry and wet cuttg of block. The

average concentration during wet cuttng is 154 ties lower that during dr cuttng.

Health H rd Evalu?tion Report No. 2000-0226

Arra 2

800-158104 mg/m

800-157004 mg/m

Saw Arra

800-1585(NO)

800-1.59604 mg/m

800-1586(NO)

~~~

Arra 800-1587(NO)

800-159(NO)

Figure 6. position of saw, worker, and air sampling array for wet sawing of block inde a buidig at the

worksite. Sample numbers and asocate dust concentrations are note at each sampling loction. ND is

non-dete.

lation Report No. 200-0226 Page 11

. ,

General wind direction

Arra 2 Saw Arra 3

800-1563(24.1 rnglrn 800-1582

(125.3rng/rn

800-1569(150.6 rnglrn

Arra 800-1594(100.6 rng/rn

800-1593(111.2 rnglrn

Figu 7. mustration of a tyica outside setup for meauring the concentration ofairbome dust durig dry

cuttng of brick at the workste. Note .that the wind is bring the dust diretly towar the worker.

Health H~rd Evaluation Report No. 2000226

Arra SawBOO-1564(2.9 mgtm

800-1574(22.7 mg/m

~~~


Arra800-1561(16 mgtm

800-1568(19.2 mgtm

Figure 8. IDustrtion of an alternate outside setup for measuring the concentration ofairbome dus durgdry cuttng of brick at the worksite. Note that the wind is carrng the dust away from the worker, reultingin a signcatly lower concentration of airborne dust at the worker s loction.

uation Report No. 2000-0226 Page 13

- .


Arra Saw800-1576(69.4 mg/m

800-1577(65.3 mg/m BOO-1567

(80.6 mgtm")

~~~

Arra 2

800-1565(25.3 mgtm

BOO-1575(22.4 mgtm

Figure 9. mustrtion of a tyica outside setup for measuring the dust concentration of airborne dustduring dry cuttg of brick at the workste. Note the change in wind diretion from the previous twofigure. The wind diretion is from the side, reulting in an intermedate concentration of airborne dust

at the worker s loction.

Health Hazrd Evaluation Report No. 200-0226

- .

APPENIX .

EVALUATION CRIRI

As a gude to the evaluation of the hazds posed by workplace exposurs, NIOSH field sta employ

envio nta evaluation criteria for the assessment of a number of chemical and physical agents. Thescriteria ar intended to suggest levels of exposu to which most workers may be exposed up to 10 hour per

day, 40 hours per week for a workig lieti without experiencing adverse health effec. Note, however,

not al workers wil be protecte from adverse health effec even though their exposurs ar mataed below

these levels. A sma percentage may experience adverse heath effects beaus of individua susptibilty, a

pre-existig mecal condition, and/or a hyprsensitivity (allergy). In addition, some hazous substaces may

act in combination with other workplace exposurs, the genera envionment, or with meications or personal

habits of tie worker to produce health effects even if the occupational exposurs ar controlled at the level set

by the criterion. These combined effects ar often not considere in the evaluation criteria. Also, some

substaces ar absorbe by dirt contact with the ski and mucous membranes, and thus potentialy increassthe overal exposure. Finaly, evaluation criteria may change over the year as new inormon on the toxic

effects of an agent beome avaiable.

The prima sours of envionmnta evaluation criteria for the workplace ar: (1) NIOSH Recmmended

Exposure Limits (RS),(Al) (2) the U.S. Deparment of Labor, Occupational Safety and Health Admstrtion(OSHA) Permssible Exposure Limts (pEL)/A2) and(3) the Amrican Conference of Governnta Industral

Hygienists' (ACG Thshold Limt Values (TVs 5A3) Employers ar encourged to follow the NIOSH

RE, the OSHA PEL' s, the ACGrn 1LV s, or whichever are the more protective criterion. OSHA reuis

employer to fuish employees a place of employment that is free from recognze hazds tht ar causing or

ar lily to cause death or serious physical han (Occupatonal Safety and Health Act of 1970, Public Law

95-596, sec. 5.(a)(1)). Thus, employers should understad that not all hazdous chemicals have speifcOSHA exposurlits such as PELs and short-term exposur limits (STEs). An employer is sti reui OSHA to protet their employees from haz, even in the absence of a speifc OSHA PEL.

A time-weighte average (TA) exposur refers to the average aiorne concentrtion of a substace durg.norm 8-t0-10-hour workday. Some substaces have reommnded S1EL or ceilg values which

intended to supplement the TWA where there ar reognze toxic effects from higher exposurs over the

short-term

NIOSH and ACGrn reommend that exposur to respirable crystaline silca (as quar or cristobalite) be

controlled so that no worker is exposed toa TWA concentrtion grter than 0.05 mg/m . The OSHA

permssible exposur limit (pEL) for respirable dust contag crystaline silca is bas on the ty of silca

. (e.

g.,

qua or cristobalte) and the percentage of silca found in respirable airne samles. With thsinormtion the PEL is calculate for eah samle using the following formula:

------------ -----

1O mwmQu + 2

For respirbl 1st contag cristobalte, the PEL is the value calculated from the qua form

rth H~rd uation Report No. 2000226 Page 15

APPENDIX REFERENCES

At. NIOSH (1992). NIOSH reommndations for occupational safety and heath: compendium of policydocumnts and statements. Cincinati, OH: US. Deparnt of Heath and Huma Servce, PublicHeath Servce, Centers for Disee Control, National Institute for Occupational Safety and Health,DHHS (NOSH) Publication No. 92-100.

. A2. CP (1999). 29 CP 1910.100. Code of Federa Regulations. Washington, DC: U.S. GovernntPrtig Ofce, Ofce of.theFederal Register.

A3. ACGm (200). 20 TIVst' and BEI(8 : Thshold limit values for chemical substaces and physicalagents and biological exposur indices. Cincinati, OH: Amrican Conference of GovernmentaIndustral Hygienists.

Health Hazrd Evaluation Report No. 20000226

For Information on OtherOccupational Safety and Health Concerns

Call NIOSH at:1–800–35–NIOSH (356–4676)

or visit the NIOSH Homepage at:http://www.cdc.gov/niosh/homepage.html

!Delivering on the Nation’s promise:

Safety and health at work for all peoplethrough research and prevention

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