Anyone who works with cement or concrete should be aware of the potential health hazards and take precautions to avoid serious health risks. Airborne dust from mixing, cutting, and grinding concrete contains crystalline silica and poses a variety of threats.
- Eye irritation. Depending on the level of exposure, effects can range from redness to chemical burns and blindness.
- Nose and throat irritation. Over the short term, inhaling high levels of concrete dust can cause choking and difficulty breathing.
- Chronic respiratory disease. Over the long term, construction dust exposure can lead to chronic bronchitis, emphysema, or silicosis, a severely disabling and often fatal lung disease. Some studies suggest a link between crystalline silica inhalation and lung cancer.
Personal protective equipment can reduce exposure, as long as equipment is chosen, fitted, and used properly. OSHA issues standards for Respiratory Protection (29 CFR 1910.134) and Eye and Face Protection (29 CFR 1926.102). Although following these guidelines is a step toward ensuring workers' safety, current thinking and newer workplace safety codes suggest it's also necessary to use engineering controls on power tools to collect and dispose of dust. This is especially important for dust-intensive operations such as cutting and grinding.
In 2001, the National Institute for Occupational Safety and Health (NIOSH) studied workers grinding concrete surfaces and learned their exposure to airborne dust containing crystalline silica was 35 to 55 times the recommended exposure limit. In 2002, NIOSH evaluated the use of local exhaust ventilation shrouds on handheld concrete grinders to determine whether they reduce dust exposure. Four different commercially available shrouds were connected by a flexible hose to a portable vacuum cleaner and tested while smoothing concrete walls. All the grinder/shroud combinations reduced dust exposure by more than 90%.
Clearly, dust shrouds and vacuum systems play a role in promoting safety and health as well as aiding jobsite housekeeping.
Current regulatory activity
OSHA currently is developing a new proposed rule for occupational exposure to crystalline silica, designed to reduce the risk of silicosis and other serious diseases. The current permissible exposure limit for construction is based on particle counting technology, which is considered obsolete.
At this point, the Agency has prepared the crystalline silica draft health and risk analysis and submitted it for external scientific peer review. This scientific peer review was completed in January 2010, and the proposed rule is scheduled to be published in February 2011. Following publication of the proposed rule, OSHA will conduct informal public hearings and open the record for public comments. Then the final rule will be developed and published. Until OSHA publishes the final rule for crystalline silica, the existing exposure limits will remain in effect.
To be sure about your legal responsibility, you need to determine whether exposures at your jobs go beyond the allowable limits for overall dust and specific dusts. OSHA's current standard for dust that contains less than 1% silica is 15 mg per cubic meter (see 29 CFR 1926.55), but the permissible exposure limit for dust with higher silica concentrations is much lower. You can visit OSHA's e-tools site(http://www.osha.gov/SLTC/etools/silica/silicosis/silicosis.html) for help on assessing your silica exposure. The Labor Department enforces Federal OSHA standards in 28 states. The remaining 22 states and jurisdictions operate under complete state plans covering both public and private sector employees. These state plans generally are at least as stringent as federal standards.
CSDA's silica initiative
The Concrete Sawing and Drilling Association (CSDA), Clearwater, Fla., educates its members and others in the industry about reducing the risks of airborne silica exposure. In 2008, through the CSDA/OSHA Alliance program, it published “Reducing Silica Exposure” (CSDA-OBP-1002), a document outlining best practices for sawing and drilling operations. Available on the CSDA website, the document stresses wet-cutting whenever possible, training employees on the proper use of engineering controls to reduce airborne dust, and using respirators and personal protective equipment to limit exposure.
The CSDA also solicited silica exposure test data from its members and compiled a spreadsheet documenting test results from almost 100 actual jobsites. The data represents a range of projects, including indoor and outdoor wall sawing, wet and dry slab sawing, core drilling, green sawing, concrete demolition, and more.
CSDA executive director Pat O'Brien says association members grew concerned that some proposed testing protocols were not compatible with much of their work. “Test methods that require sampling over extended periods of time don't reflect the reality of many concrete sawing and drilling projects. Crews often travel to and work at several jobsites during the course of a day,” O'Brien says. “By compiling and publishing the results of these tests, some performed by NIOSH and some by consultants hired by contractors, we hope to give members a realistic picture of silica exposure under various conditions.”
O'Brien says the data will be posted on the association's website after a final review by the CSDA's Safety Committee at its meeting in September.
Workers favor vacuum use
One key benefit of dust shrouds and vacuum systems is that workers use them. These systems improve working conditions, above and beyond reducing health risks. Less dust means better visibility and a cleaner, more comfortable work environment. Although it can be difficult getting workers to use respirators and other personal protective equipment properly and consistently, vacuum systems seem to generate little resistance.
Tool manufacturers are responding to the market's acceptance of these systems by producing specialized dust shrouds and collection devices on a broad range of machines. The following product roundup offers several examples. It's wise to take advantage of this affordable, effective means of protecting crews.
Kenneth A. Hooker is a freelance writer based in Oak Park, Ill.