Silica-Based Respiratory Programs?
Some of SCM’s clients’ work includes exposure to silica. They perform a variety of tasks where there may be an inhalation exposure to the known respiratory hazard (silica). These tasks include drilling into, breaking, or mixing concrete, cutting certain tiles, and sandblasting. At times, these clients are asked by other companies whether they have a respiratory protection program. Some of them have a respiratory protection program, but not all clients need one. Why don’t all these clients that work with silica have a respiratory protection program if they have a potential for exposure to a harmful substance?
That’s a good question. On the surface, a respiratory protection program sounds like a good idea. But let’s dig a little deeper by looking at the respiratory protection regulation, 29 CFR, Part 1910.134(a)(1), that says: “In the control of those occupational diseases caused by breathing air contaminated with harmful dusts, fogs, fumes, mists, gases, smokes, sprays, or vapors, the primary objective shall be to prevent atmospheric contamination. This shall be accomplished as far as feasible by accepted engineering control measures (for example, enclosure or confinement of the operation, general and local ventilation, and substitution of less toxic materials).”
From the above quote, we see that we need to first know whether silica is an inhalation hazard. Most experts agree that silica is just that. The workplace safety topic page for silica on the NIOSH website tells us that, “Silicosis, an irreversible but preventable lung disease, is caused by inhalation of respirable silica dust. Work exposures to silica dust also cause other serious diseases, including lung cancer.”
Next, SCM asks our clients what their level of exposure to silica is. According to the regulation on silica, 29 CFR, Part 1910.1053(b), the action level for exposures to respirable crystalline silica is 25 μg/m3, calculated as an 8-hour time-weighted average or TWA. Silica exposure is measured in micrograms which are 1000 times smaller than milligrams. That means it does not take very much silica dust in the air to create an exposure that would be considered a hazard. But that does not mean everyone is exposed to silica at or over the action level.
One method to determine whether respiratory protection may be required is to do an industrial hygiene study, measuring the level of potential contaminants in the atmosphere where work is being done. You can also look at the regulation, where OSHA provides a helpful table that lists common tasks that have the potential for exposure to silica and gives the minimum respiratory protection that should be used while performing those tasks. The table can be found in 29 CFR 1926.1153(c).
Table 1- Specified Exposure Control Methods When
Working with Materials Containing Crystalline Silica
For example, a worker must use a handheld saw to cut a material that is known to contain silica. The saw has an integrated water delivery system that continuously feeds water to the blade. According to the table, when the saw is used outdoors and according to manufacturer’s instructions, no respiratory protection is needed, indicating the level of exposure is lower. When the saw is used indoors or in an enclosed area, the table says that the user must wear respiratory protection with an assigned protection factor (APF) of at least 10, indicating a higher level of exposure. To give you some perspective, an N95 filtering facepiece or mask usually has an APF of 10.
SCM recommends, for the example provided, when possible, use the saw outdoors to reduce and control the exposure. It would be the simpler solution. Other options might be to increase the ventilation in the area where the saw is being used or have a filtration system that could reduce the contaminants in the area, as stated in the respiratory protection regulation. These might be better options rather than to default to the use of respiratory protection that depends upon the wearer to use the mask correctly. If you remember our discussions on the hierarchy of controls, PPE is always the lowest and least effective control method.
The safety tip this week is that it is better to determine the level of exposure than to assume that respiratory protection is required, which, in turn, would necessitate a respiratory protection written program.
Speaking of written programs, we must mention that, just because a respiratory protection program is not required, our clients still may need to have a silica exposure control plan. The exposure control plan is required by the regulation for the protection of workers (20 CFR 1926.1153(g)).