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WORKPLACE SOLUTIONSFrom the National Institute for Occupational Safety and Health

SummaryConstruction workers are ex-posed to hazardous dust whenusing handheld electric grind-ers to smooth poured con-crete suraces ater orms arestripped. The National Insti-tute or Occupational Saetyand Health (NIOSH) oundthat exposures could be re-duced i a local exhaust ven-

tilation (LEV) shroud was at-tached to the grinder.

DEPARTMENT OF HEALTH AND HUMAN SERVICESCenters for Disease Control and Prevention

National Institute for Occupational Safety and Health

Control of Hazardous Dust WhenGrinding Concrete

disease, reduced lung unction, andother disorders [NIOSH 2002a].

Workers in the construction industrymay breathe dust that contains silicaduring various tasks including cuttingbrick and block, tuckpointing ma-sonry, using a jackhammer to breakconcrete or rock, or grinding con-crete. A NIOSH [2001] study oundthat workers grinding concrete tosmooth poured concrete suraces a-ter orms are stripped were exposedrom 35 to 55 times the NIOSH rec-ommended exposure limit (REL) orairborne dust containing crystallinesilica. NIOSH evaluated the use oLEV shrouds on handheld concretegrinders to see whether they reduceworker exposure to dust [Echt andSeiber 2002; NIOSH 2002b].

NIOSH StudyThe concrete nishers in the NIOSHstudies were responsible or smooth-

ing poured concrete walls and col-umns. The LEV system consist-ed o a grinder that was equippedwith a ventilation shroud, a lengtho fexible corrugated hose, and aportable electric vacuum cleaner that

acted as the an and dust collectoror the ventilation system (Figures 1

and 2). The concrete suraces werefat and allowed the shroud to makea good seal with the concrete. Fourcommercially available shrouds wereused in the NIOSH study. All grinder/shroud combinations reduced dust ex-posure by at least 90%.

Description of

ExposureBreathing dust that contains crystal-

line silica can lead to the develop-

ment o silicosis, a deadly lung dis-

ease. No eective treatment existsor silicosis, but it can be prevented

by controlling workers exposure to

dust containing crystalline silica. Ex-

posure to crystalline silica has also

been linked to lung cancer, kidney

Figure 1. Grinder in use with the con-

trol in place.


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GrindersThe grinders used were rated at either 10,000 or 11,000rpm: Metabo model W7-115 Quick 10,000-rpm grind-er and Metabo model 11025 grinder (MetabowerkeGmbH; Nrtingen, Germany); Bosch model 1347Agrinder (Robert Bosch GmbH; Stuttgart, Germany); andMilwaukee model 615320 grinder (Milwaukee Elec-tric Tool Corp.; Brookeld, WI). The grinders were t-ted with 4-inch diameter diamond cup wheels (PW se-ries, Pearl Abrasive Co.; Commerce, CA).

LEV shroudsFour LEV shrouds were used in the study. The shroudswere selected based on their rugged appearance, howeasily they could be mounted on the grinders, and theiravailability or purchase. The shrouds used were Vacu-guard (Pearl Abrasive Co.; Commerce, CA), Dustcon-

trol (Transmatic Inc; Wilmington, NC); and ull-dustshroud and cut (edging) shroud (Sawtec; OklahomaCity, OK).

Vacuum cleaners and hosesThe grinder/shroud pairs were connected via 1.5-inch(inside diameter) corrugated fexible hose to two typeso industrial vacuum cleaners (DC 2700 and DC 3700;Dustcontrol AB, Norsborg, Sweden). The manuactur-er reports that the DC 2700 vacuum has a maximumfow capacity o 112 cubic eet per minute (190 cubic

meters per hour), and a maximum negative pressure o84 inches w.g. (21 kPa). The DC 3700 has a maximumfow capacity o 188 cubic eet per minute (320 cubicmeters per hour) and a negative pressure o 96.5 inch-es w.g. (24 kPa).

ControlsNIOSH and its partners have developed recommenda-tions to protect workers rom exposure to crystalline sil-ica dust during construction activities [NIOSH 1996;Echt and Seiber 2002; NIOSH 2002a; Heitbrink and

Collingwood 2005]. Some o the benets o using thedust control noted in this report include reducing work-er exposure to hazardous dust and potentially allowingor use o less protective respiratory protection, reducedcleanup time, and reduced cleanup exposures.

Vacuum cleanersThe choice o a vacuum cleaner depends on the task. Itmust be careully selected to include eatures such as theollowing:

Sucient fow rate to capture the dust and transportit to the vacuum source

Uses a high-eciency particulate air (HEPA) lter toreduce the chance o releasing dust containing crys-talline silica rom the vacuum into the worksite

Uses pre-lter or cyclone to increase the length oservice o the HEPA lter

Uses lter replacement indicator

Filters can be cleaned and replaced or ull collectionbowls or bags can be replaced without exposing theoperators to dust

The vacuum cleaner should draw at least 10 amps i it isused as part o a ventilated grinder system, so it can over-come lter loading. Some vacuum cleaners are equippedwith a pressure gauge that indicates when the air fowrate is too low to be eective. I the vacuum cleaner doesnot have a pressure gauge, workers can monitor the airfow by looking at the dust plume. I dust is escaping un-der the shroud, the dust collected on the pre-lter needsto be dislodged or the vacuum cleaner bags or lters needto be changed.

HoseA 1.5- or 2-inch diameter hose with a relatively smoothinterior and a length o no more than 15 eet should pro-vide adequate air fow. The hose should have as ew el-bows or turns as possible. A study on tuckpoint grinders[Heitbrink and Collingwood 2005] reported that 2-inchdiameter hoses provided better air fow than smaller(e.g., 1.5 inch) diameter hoses. Dust has a greater ten-dency to settle in larger diameter hoses and should becleared beore and ater each use.Figure 2. Diagram of grinder showing main parts.


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ShroudThe shroud can be purchased with the grinder, sepa-rately, or as a unit with the vacuum cleaner and hose.The shroud should totally enclose the spaces around theexhaust entry point or the hose. The exhaust shroudshould have an entry point or the hose matching the di-ameter o the hose.

Work practicesKeep the shroud fat against the surace o the con-crete while grinding.

Shake the hose as needed to loosen the settled dustand prevent the hose rom clogging.

When using the grinder, look to make sure no dust isescaping rom the shroud.

I dust is escaping, turn o the unit and clean orchange the lter as recommended by the manuac-

turer. Sometimes the build-up on the lter can bedislodged by simply moving or shaking the cleaner, orturning the motor o and on a ew times. Build-up onthe lters slows down the air fow through the systemand reduces dust capture.

Change vacuum cleaner bags beore they leak.

When changing lters, bags, or sel-contained collec-tion bowls, use proper disposal practices and use res-pirators i appropriate.

Since NIOSH last investigated concrete grinders in 2002,several grinder manuacturers have introduced tools withdust controls. Studies since the NIOSH investigation show

the eectiveness o LEV controls in reducing respirabledust when using concrete grinders [Croteau et al. 2004;Akbar-Khanzadeh et al. 2007].

RespiratorsWorkers and employers should be aware o the high risko dust exposure in poorly ventilated areas (such as incorners or inside buildings). This may result in increasedexposure to hazardous dust.

The dust control cited in this report may greatly reduceworker exposure to hazardous dust; however, respirators

are still necessary to reduce exposure to crystalline sili-ca below the NIOSH REL o 50g/m3. Follow the Oc-cupational Saety and Health Administration (OSHA)Respiratory Protection Standard (29 CFR* 1910.134)(www.osha.gov/SLTC/etools/respiratory/index.html).The provisions o the program include procedures or se-lection, medical evaluation, t testing, training, use, andcare o respirators.

* Code o Federal Regulations. See CFR in reerences.

AcknowledgmentsThe principal contributors to this publication were Alan

Echt o the Division o Applied Research and Technolo-gy, NIOSH and John J. Whalen under contract with theU.S. Public Health Service, Division o Federal Occupa-

tional Health.

ReferencesAkbar-Khanzadeh F, Milz S, Ames A, Susi PP, Bisesi M, Khud-

er SA, Akbar-Khanzadeh A [2007]. Crystalline silica dust and

respirable particulate matter during indoor concrete grind-ingwet grinding and ventilated grinding compared withuncontrolled conventional grinding. Occup. Environ. Hyg

4:770779.CFR. Code o Federal regulations. Washington, DC: U.S. Gov-ern-

ment Printing Oce. Oce o the Federal Register.Croteau GA, Flanagan ME, Camp JE, Seixas NS [2004]. The

ecacy o local exhaust ventilation or controlling dust ex-

posures during concrete surace grinding. Ann. Occup. Hyg48(6):509518.

Echt A, Seiber K [2002]. Control o silica exposure rom handtools in construction: grinding concrete. Appl Occup Environ

Hyg 17(7):457461.Heitbrink WA, Collingwood S [2005]. Protecting tuck-

pointing workers rom silica dust: drat recommen-dations or a ventilated grinder. The Center to Pro-

tect Workers Rights, Silver Spring, MD [www.cdc.gov/elcosh/docs/d0600/d000683/d000683.html].

NIOSH [1996]. NIOSH Alert: Request or assistance in pre-venting silicosis and deaths in construction workers. Cin-cinnati, OH: U.S. Department o Health and Human Ser-

vices, Centers or Disease Control and Prevention, DHHS(NIOSH) Publication No. 96112.

NIOSH [2001]. In-depth survey report o our sites: exposureto silica rom hand tools in construction chipping, grinding,

and hand demolition at Frank Messer and Sons ConstructionCompany, Lexington and Newport KY; Columbus and Spring-

eld, OH. Cincinnati, OH: U.S. Department o Health andHuman Services, Centers or Disease Control and Preven-

tion, National Institute or Occupational Saety and Health,Survey Report No. EPHB 24715.

NIOSH [2002a]. NIOSH hazard review: Health e-

ects o occupational exposure to respirable crystallinesilica. Cincinnati, OH: U.S. Department o Health and Hu-

man Services, Centers or Disease Control and Preven-

tion, National Institute or Occupational Saety and Health,DHHS (NIOSH) Publication No. 2002129.

NIOSH [2002b]. In-depth survey report o control o

respirable dust and crystalline silica rom grindingconcrete at Messer Construction, Newport, Kentucky andBaker Concrete Construction, Dayton, Ohio. Cincinna-

ti, OH: U.S. Department o Health and Human Services,Centers or Disease Control and Prevention, National In-

stitute or Occupational Saety and Health, Survey ReportNo. EPHB 24721.


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DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

4676 Columbia Parkway

Cincinnati, OH 452261998

safer healthier peopletm

April 2009

For More Information

The inormation in this document is based on NIOSH eldstudies. More inormation about silica hazards and controlsis available on the NIOSH Web site at www.cdc.gov/niosh/topics/silica/deault.html.

To receive copies o the NIOSH eld study reports thatormed the basis o this document or to obtain inormationabout other occupational saety and health topics, contactNIOSH at

Telephone: 1800CDCINFO (18002324636)TTY: 18882326348 E-mail: [email protected]

or visit the NIOSH Web site at www.cdc.gov/niosh

For a monthly update on news at NIOSH, subscribe toNIOSH eNews by visiting www.cdc.gov/niosh/eNews.

Mention o any company or product does not constitute en-dorsement by NIOSH. In addition, citations to Web sites ex-ternal to NIOSH do not constitute NIOSH endorsement othe sponsoring organizations or their programs or products.

Furthermore, NIOSH is not responsible or the content othese Web sites. All Web sites addressess reerenced in this

document were accessible as the publication date.

This document is in the public domain and may be

freely copied or reprinted. NIOSH encourages all

readers of the Workplace Solutions to make them

available to all interested employers and workers.

As part o the Centers or Disease Control and Prevention,NIOSH is the Federal agency responsible or conducting re-search and making recommendations to prevent work-relatedillness and injuries. All Workplace Solutions are based on re-search studies that show how worker exposures to hazardousagents or activities can be signicantly reduced.

Control of Hazardous Dust When Grinding Concrete

DHHS (NIOSH) Publication No. 2009115

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