Solution Summary: Hand-held Grinders with Wet Dust Suppression
A hand-held grinder with wet dust suppression delivers water to the surface to reduce airborne contaminants while smoothing masonry surfaces.
Description:
Hand-held surface grinders are often used to smooth poured concrete surfaces after the forms have been removed. Hand-held grinders are also used to smooth granite, marble and other natural stone. Grinding concrete and natural stone generates a large amount of dust which is likely to contain high levels of crystalline silica and creates a hazard for everyone in the vicinity. Increasingly, nano-enabled masonry products are being used in construction that can also expose workers to inhaling engineered nanomaterials when the products are being cut or ground. Concrete roofing tiles that contain nano-size titanium dioxide are an example.
Intertool DS 175 7-inch planetary polisher with wet dust suppression
- Used to grind, hone, polisher or clean steps, counter tops, floor edges, under toe kicks or other small areas
- Polisher can be driven by any 5/8-11 (or 14-2 mm) tool
- Power requirements: depend on drive tool
- Polishing diameter: 7 inches, achieved with three 3-inch planetary discs
- Maximum disc speed (provided by drive tool): 5,000 RPM
- Weight: 5 pounds
- Alternative dust control methods: port is provided for use with a vacuum
- Sound pressure level: Not available but likely to exceed 90 dBA (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average)
Intertool DS 301 12-inch planetary polisher with wet dust suppression
- Used to grind, hone, polish or clean concrete, terrazzo, marble or granite surfaces using coated abrasives, diamond polishing systems, light weight diamond wheels or brushes
- Power requirements: 115 volts, 10.5 amps (220 volt model is available)
- Polishing diameter: 12 inches, achieved with three 5-inch planetary discs
- Disc speed: 2,700 RPM (variable speed option available upon request)
- Weight: 30 pounds
- Alternative dust control methods: dust cowl is available for use with a vacuum
- Sound pressure level: Not available but likely to exceed 90 dBA (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average)
FLEX LW 1509 Wet Grinder
- Used on concrete or natural stone for bulk material removal, edge breaking, coarse grinding and polish preparation work
- Power requirements: 120 volts, 7.8 amps
- Maximum disc diameter: 4-1/2 inches
- Blade speed (no load): 8,300 RPM
- Weight: 4.8 pounds
- Sound pressure level: Not available but likely to exceed 90 dBA (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average)
MK Diamond Products, Inc. MK-1503-Air pneumatic polisher with wet dust suppression
- Used for grinding and polishing gemstones, rock materials, marble and granite
- Compressed air supply requirements: 16 cubic feet per minute at 90 pounds per square inch
- Polishing disc diameter: 3, 4 or 5 inches
- Blade speed (no load): 5,500 RPM
- Weight: 2.7 pounds
- Sound level: 92.3 to 104.9 decibels (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA)
MK Diamond Products, Inc. MK-1503SS electric polisher with wet dust suppression
- Used for grinding and polishing gemstones, rock materials, marble and granite
- Power requirements: 120 volts, 7.9 amps
- Polishing disc diameter: 3, 4 or 5 inches
- Blade speed: 2,000 to 4,000 RPM
- Weight: 6 pounds
- Sound pressure level: Not available but likely to exceed 90 dBA (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average)
Risks Addressed:
Grinding concrete, stone and masonry materials containing crystalline silica is a high dust activity that in the absence of controls would place workers at risk of lung disease, cancer, chronic obstructive pulmonary disease (COPD), lung scarring and silicosis with prolonged exposure. Silicosis is an incurable, sometimes fatal disease. Such disease is well documented in the Vermont granite quarries and stone cutting sheds, and in construction operations. The NIOSH-recommended exposure limit (REL) is 0.05 mg/m3 as a time-weighted average concentration for up to a 10-hour workday during a 40-hour workweek. OSHA has a new construction permissible exposure limit (PEL) for respirable crystalline silica of 0.05 mg/m3 as an 8-hour time weighted average (TWA).
Another less understood, but emerging hazard is engineered nanomaterials. Incredibly small particles are being added to a broad range of construction products to improve performance, but animal toxicity tests indicate a need for closer scrutiny. There is no evidence yet that engineered nanomaterials have caused harm in exposed workers. However, it is most important that exposures be limited and that precautionary approaches be used to reduce exposure and protect construction workers from the potential hazards of engineered nanomaterials. Nano-size ultrafine titanium dioxide, which can be present in nano-enabled masonry products, has been found to cause inflammation of the lungs and lung cancer in lab animals. The National Institute for Occupational Safety and Health (NIOSH) has determined that ultrafine titanium dioxide should be considered a potential occupational carcinogen. Other engineered nanomaterials that may be present in products used in masonry work could also potentially cause harm when inhaled by construction workers. Cutting nano-enabled concrete roofing tiles without engineering controls can generate excessive amounts of airborne dust that if inhaled by workers could increase the risk of developing respiratory disease (West GH, et al. 2016). It is likely that grinding nano-enabled masonry products will generate high levels of airborne dust and possibly engineered nanomaterials in the absence of any control measures designed to reduce exposures.
OSHA has no specific regulation or Permissible Exposure Limit (PEL) for any engineered nanomaterial. However, NIOSH has a recommended exposure limit (REL) for ultrafine titanium dioxide of 0.3 mg/m3 as a time-weighted average (TWA) concentration for up to 10 hours/day during a 40-hour week. The intent of the REL is to lower the risk to workers of the potential for developing lung cancer.
How Risks are Reduced:
Water is delivered to the grinding disc where it combines with particles created by grinding of stone, concrete and masonry materials and the now larger particles settle. Silica in the concrete and masonry materials is only hazardous if it is inhaled and is not hazardous for skin contact. As long as the dust does not become airborne, the hazard is reduced. The extent to which these tools are effective in meeting recommended exposure limits has not been evaluated. For nano-enabled masonry products, wet dust suppression is also likely to be effective in reducing concentrations of airborne engineered nanomaterials in a worker’s breathing zone.
Using water will visibly suppress dust, but the extent that it reduces the small, respirable particles is unclear, without additional testing. Although exposure is not reduced to zero, substantial reduction is expected. This is dependent on the amount of water used, how effectively it prevents suspension of particles in the air, rotational speed of the grinder and the extent to which workers are exposed to resuspended dust after it dries. While there is no published sampling data on these specific tools, evidence indicates exposure to respirable silica can be significantly reduced through the use of wet methods.
There are no reported studies specifically evaluating the effectiveness of wet dust suppression methods in controlling construction worker exposure to engineered nanomaterials in masonry products when using grinders. However, because wet dust suppression methods with water-fed grinders has been demonstrated to significantly reduce worker exposure to silica, it is likely that wet dust suppression will reduce worker exposure to engineered nanomaterials when used for grinding on nano-enabled masonry products.
Effects on Productivity:
Wet dust suppression systems can have either positive or negative effects on productivity, but definitely improve the quality of the work by suppressing large amounts of airborne dust, which allows a cleaner, more efficient means of grinding.
Additional Considerations:
Grinding of concrete or masonry performed in the state of California must employ engineering controls, either wet methods or local exhaust ventilation, unless the employer can show that exposures are below the permissible exposure limit (subchapter 4, article 4, section 1530.1). New Jersey has a similar prohibition of dry cutting or grinding of masonry (Chapter 172).
Contributors:
Bruce Lippy, PhD, CIH - CPWR - The Center for Construction Research and Training
Michael R. Cooper - Aria Environmental, Inc.
Bill Kojola, MS
Hazards Addressed:
- Paints & Coatings
- Perform abrasive blasting
- Prepare surfaces with mechanical devices
Availability
Intertool: DS 175 7-inch and Intertool DS3011 12-inch planetary polisher with wet dust suppression
To obtain information, visit DS 175 7-inch and DS 3011 12-inch
or contact 1-800-926-9244 mm@leitchco.com
MK Diamond Products, Inc. MK-1503-Air pneumatic polisher and MK-1503SS polisher with wet dust suppression
To obtain information, visit MK-1503
or contact 1-800-421-5830 customerservice@mkdiamond.com
Flex North America, Inc.: LW 1509 wet grinder
To obtain information, visit LW 1509
or contact 1-877-331-6103 http://flexnorthamerica.com/contact.php