OSHA Significantly Reduces Silica Dust Exposure Limits

Construction Site silica dust

When workers in construction, mining, or other industries cut, crush, grind, or process silica-bearing material, a substance called respirable crystalline silica (silica dust) releases into the air. If inhaled, this can cause serious health problems for your workers, such as silicosis, lung cancer, and kidney disease.

Cal/OSHA has recently adopted two Federal OSHA regulations to reduce the risk of diseases associated with breathing silica dust. One standard applies to the construction industry, and the other to general industry and maritime.

The new standards are OSHA’s latest effort to reduce silica dust exposure. Between 1968 and 2005, the mortality rate from silicosis alone dropped from nearly 1,200 deaths per year to about 170. This is a result of occupational health standards adopted since OSHA’s inception, as well as a decline in certain heavy industries. By reducing permissible exposures even more this year, OSHA’s objective is to further cut the rate of silicosis and other diseases caused by inhaling silica dust.

Employee Training should include...

Setting new standards

Under both new regulations, the eight-hour permissible exposure limit (PEL) for all types of respirable crystalline silica is now 50 micrograms per cubic meter of air (μg/m3). That’s half the prior limit just for respirable quartz. Exposures that exceed the new PEL require respiratory protection. You must also post warning signs and restrict access to these regulated areas.

Even at the 50 μg/m3 permissible limit, OSHA still considers there to be significant disease and mortality risk, but the agency says the new PEL is appropriate because it is the lowest level feasible for all affected industries.

Therefore, the agency has established a 25 μg/m3 action level. When exposures exceed this level, additional safeguards are required.

These include:

  • Developing and implementing an exposure control plan, and validating its effectiveness through air monitoring.
  • Conducting employee medical evaluations as part of ongoing medical surveillance of exposed workers.
  • Developing a silica housekeeping program, placing emphasis on high efficiency vacuum and wet cleaning methods.
  • Employee training.

Wet mopping, wiping, and HEPA vacuuming are effective measures for cleaning process areas and reducing surface contamination that may accumulate and further contribute to exposure. Compressed air and dry sweeping should be avoided, as these contribute to airborne silica exposures.

For the construction industry only, OSHA specifies process and tool specific control measures that – once fully implemented – would eliminate the need for air monitoring. These measures rely on dust collection, air filtration, and water feed systems for dust control. It also identifies processes that will require respiratory protection to supplement dust control measures. General industry and maritime operations must always conduct air monitoring.

Less risk of serious illness

While OSHA’s new standard means employers must implement additional control measures, it comes as good news for the estimated 2.3 million people who work in industries where silica dust exposure is a daily occurrence, as they will breathe in less of the substance.

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