Silicosis is an incurable, occupational lung disease that effects nearly everyone in the construction industry. Silicosis is caused by inhalation of crystalline silica dust (also known as crystalline forms of Silicon dioxide) . Silica is the basic component of sand and gravel.
“An estimated 95% of silicon dioxide produced is consumed in the construction industry, e.g. for the production of Portland cement.”
– Otto W. Flörke, et al. “Silica” in Ullmann’s Encyclopedia of Industrial Chemistry
Our policy at Titus Restoration is to do everything is required to protect our employees, customers, buildings and their patrons from being exposed to crystalline silica dust. Crystalline Silica Dust is a possibility on most construction projects and it is impossible to see with the naked eye. We have trained all our employees and we will take every precaution to prevent respirable silica dust. However, we constantly review this policy with our employees to insure that all their questions are answered. The proper documentation of this training is retained by Titus Restoration Services for future reference. Silicosis must be prevented!
Dry Grinding vs Wet Grinding
Every contractor is free to choose the preferred method to cut, grind or polish the concrete. Grinding without any kind of dust control should never happen as it is very dangerous to everyone’s heath.
The other 2 methods you can choose are vacuum dust collection ( used in dry grinding) or water dust collection ( used in wet grinding).
There is an on-going dispute in the concrete polishing business whether dry or wet grinding/polishing is better. Regardless of the position taken by others, Titus Restoration has taken the position that safety overrides all other considerations. It is our opinion that DRY grinding exposes our employees, the other building occupants at the time of grinding, and the entire building itself in a long term, to respirable silica dust (which puts future occupants at risk). Silicosis is usually associated with the breathing of invisible respirable crystalline silica over a period of many years. These tiny invisible particles can enter the mucus membrane of the lungs causing silicosis. However, with some people, its onset is a much shorter time. In concrete grinding and polishing, this dust is mostly generated by DRY grinding or DRY polishing concrete.
Vacuum dust collection can significantly reduce silica levels but the results are far away from the results obtained using wet system. Vacuum dust collection may not reliably keep the presence of silica in the air below 0,1 mg/m3 as an 8-hour TWA. It is up to the contractor to change and maintain filters on a regular basis to keep these particles out of the air.
There is no compelling reason to put human lives at risk by dry grinding and polishing.
Silicosis Preventive Measure
Below is an excerpt of an articles published by OSHA that can help us to understand better the issues about dry grinding dry cutting or dry polishing. Also thanks to this online documentation we were able to choose the right way to follow and we can repeat with conviction that our preferred method is wet grinding and wet polishing because dust that is wet is less able to become or remain airborne.
Wet cutting is the most effective method for controlling silica dust generated during sawing because it controls the exposure at its source. Dust that is wet is less able to become or remain airborne. Results obtained by OSHA and the National Institute for Occupational Safety and Health (NIOSH) at five construction sites indicate that wet masonry saw operators’ exposures were routinely below 0.1 mg/m, and usually below 0.05 mg/m3, not only when averaged over an 8-hour shift, but also during just the period evaluated. At one jobsite, for example, NIOSH recorded a respirable silica exposure level of 0.04 mg/m3 in the breathing zone of an employee cutting concrete blocks using a water-fed bench saw. The employee operated the saw for approximately 5 of the 8 hours sampled (NIOSH, 1999a). Even if the employee had cut block for a full 8-hour shift, his estimated exposure would have been 0.05 mg/m3.
In comparison, OSHA reported a significantly higher exposure at another site on a day when wet methods were not used due to cold weather. The employee dry cut concrete block outdoors for a similar period of time (nearly 6 hours), but in this case experienced an 8-hour average exposure of 2 mg/m3 (OSHA Case Files).
Employee exposures associated with uncontrolled dry cutting tend to be lower for employees operating saws for a smaller percentage of their shift, as well as for jobs involving materials with lower silica content. However, among the nine results obtained by OSHA and NIOSH, the average exposure or dry cutting outdoors was 0.56 mg/m3 (with a median of 0.25 mg/m3) for the periods sampled. These values exceed OSHA limits, and were associated with employees dry cutting for 10 to 60 percent of the time sampled. At three construction sites, employee exposures exceeded 2 mg/m3, presumably during periods of intensive cutting lasting from 2 minutes to 6 hours.
— Osha – Silica Exposures
Wet Grinding and Polishing Concrete
The best prevention is simply not creating silica dust. This is accomplished by grinding and polishing with water. The use of enough water will allow the process to be performed without any dust generated.
The Titus silicosis policy is simple…wet grind and wet polish at all times possible to prevent silicosis.
These are the EPA preferred methods for eliminating silica dust in the air and contamination of the building.
When Dry Grinding Concrete is Neccesary
In the event dry grinding is unavoidable, dust collection with powerful vacuum system to avoid the highest level of silica in the air is an absolute. Those who must be involved in working in and around the crystaline silica dusty operation must wear the N-100 (99.7 dust filtration) NIOSH approved dust masks for silica dust. These NIOSH approved dust masks provide protection to 10 times the PEL (Personal Exposure Limit) for silica dust. Dust masks must be changed at least daily or when the inside becomes visibly dirty. They are not adequate for very dusty areas where a cartridge type (negative air) respirator must be worn. People not necessary to the operation should remain in a dust-free area.
Dust Mask Fit Test
Even when wearing an approved dust mask such as the NIOSH N-100, the employee must pass a fit test such as a the bitrex / hood fit test which is administered in the Titus Restoration home office. Anyone who has not passed a fit test or is not wearing an approved mask may be asked to leave while dry grinding is taking place.
Warning About Dust Masks
Legally and from a SAFETY standpoint, anyone who needs to wear a cartridge type respirator (negative air respirator) MUST be medically approved to do so. People who were not medically approved have died wearing negative air respirators. If negative air respirators are required, they shall only be worn AFTER the employee has have been medically approved and trained, in accordance with a Respirator Training Program in their use, cleaning and storage.