Document Z46z03mJ8D7gK99Dga28XGGKJ

/Tiosh HAZARD ID Respirable Crystalline Silica Exposures During Tuck Pointing HID 9 Description of HAZARD Silicosis is a deadly lung disease. Construction workers may get sick with silicosis if they breathe in too much respirable crystalline silica, a fine, sandy dust. Silicosis may take 10 or more years to develop when workers are exposed daily to low concentrations of silica dust. However, when exposures to silica are very high, symptoms can occur after only a few weeks to 4-5 years. During a recent study of tuck pointing at a con struction site, NIOSH researchers measured very high concentrations of respirable crystalline silica. At this site, the workers' exposures were up to 50 times the REL (recommended exposure limit). At another construction site, investigators from OSHA (Occupational Safety and Health Administration) found high exposures--up to 100 times the REL. To prevent silicosis, researchers from NIOSH (the (National Institute for Occupational Safety and Health) urge construction workers to protect them selves from dust ex po sure when do ing con struc tion work, especially tuck pointing. In tuck pointing, the worker grinds the mortar out from be tween the bricks--the first step to fix ing up the outside of an older brick building. Mortar dust contains crystalline silica. During tuck pointing, workers hold power grinders, digging the mortar out to a depth of an inch or less. The grinders often have wheel diameters of4to6 inches and rotate at speeds as high as 12,000 rpm. The grinding process breaks up the mortar and turns it into airborne dust. The rotating wheel creates wind that carries this airborne dust throughout the work place. When work ers clean the mor tarjoints and their clothes, tools, and equip ment with com pressed air, the strong blast needlessly adds even more dust to the air (see Figures 1 and 2). Figure 1. Tuck pointing. Recommendations for Prevention Because these construction studies showed such high con cen tra tions ofre spi ra ble crys tal line sil ica, NIOSH is running more tests on commercial grinders. They want to see how much the built-in ventilation in the grinders cuts down on dust expo sures during tuck pointing. Also, NIOSH research ers want to find out which engineering controls work best during this work. In the meantime, con struction workers should follow the recommenda tions below to reduce their exposures. ventilated grind ers may not con trol the dust enough, NIOSH recommends the following respiratory protection: For less than 1,000 times the REL (50 mg/m3--milligrams per cubic meter), use a supplied-air respirator that has a half-mask. Set the respirator on pressure-demand or one of the other positive-pressure settings. For example, run a Type CE abrasive-blasting respirator on a positive-pressure setting. Contractors and workers should use good work practices and respiratory protection. Good Work Practices Use a grinder that has local exhaust ventila tion when possible. For exposures less than 50 times the REL (2.5 mg/m3), use (a) an air-purifying, full-face respirator with a high-efficiency particulate air filter ora P100 filter, or (b) a powered, air-purifying respirator with a tight-fitting facepiece and a high-efficiency particulate air filter or a P100 filter. Do not use the grinder near another worker. Restrict some work areas to cut down expo sures to other workers. For exposures less than 10 times the REL (0.5 mg/m3), use a half-mask, air-purifying respirator that has a P100 filter. Stand so that the dusty air will not blow on you and other workers. Equipment manufacturers are encouraged to do the following: In poorly ven ti lated ar eas such as a courtyard or the inside cor ners of a build ing, use fans to blow out dusty air. Develop ventilated shrouds for grinders that give a clear view and good dust control. Do not use compressed air to clean your self, your clothes, or your equip ment. Make sure the vacuum cleaners used for dust con trol and clothes clean ing cap ture at least 99 percent of the small particles that could be inhaled (0.3 micrometer diameter). Develop the minimum exhaust volume needed for ventilated shrouds. This exhaust volume must be based on experimental and field data. Respiratory Protection (Respirators) During tuck pointing, employers need to check respirable crystalline silica exposures from time to time to see how well the safeguards are working and ifwork ers need re spi ratorypro tection. Be cause For more information about the health hazards of ex po sure to crys tal line sil ica, re spi ratory pro tec tion for work ers, and the four Type CE abra sive-blasting respirators that NIOSH certifies, order the NIOSH Alert Preventing Silicosis and Deaths in Construc tion Workers, DHHS (NIOSH) Publication No. 96-112. To get your free copy, call NIOSH. For More Information To obtain more free information about this hazard or other occupational safety and health issues, Call NIOSH at 1-800-35-NIOSH (1-800-356-4674) or visit the NIOSH Web site at www.cdc.gov/niosh A cknowledgments The principal contributors to this document were William A Heitbrink, Ph.D., CIH, and Jerome P. Flesch, M.S., of NIOSH. Char lie Shields of OSHA provided much valuable information about tuck point ing ex po sures. Anne Votaw, M.A., of NIOSH, translated the text into easier-to-read prose. Desk top publishing was provided by Susan Kaelin and Kristina Wasmund. Figure 2. Air blowing. November 1999 DHHS (NIOSH) Publication No. 2000-113 U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service Centers for Disease Control and Prevention National Institute for Occupational Safety and Health CDC CENTERS FOR DISEASE CONTROL AND PREVENTION