MANAGING BEST PRACTICES: Getting particular about particulates
The air we breathe is filled with a variety of particles that vary in shape, size, structure, composition, solubility and other parameters. Particles are formed from solids and may be generically called dust, mist, smoke or fume. Illness or discomfort may arise if we inhale too many particles.
Some particles may be distinguished as a specific substance with known toxic effects and have their own exposure limits. Silica is an example. OSHA regulates particles that cannot be classified as a specific substance as “Particulates Not Otherwise Regulated†(PNOR) (Table Z-1) or Inert or Nuisance Dust (Table Z-3). OSHA’s permissible exposure limits for PNOR and inert or nuisance dust are based upon particle size. If particles of all sizes are included, then the PEL for “total dust†is 15 mg/m3. If only particles less than 10 micrometers (microns) in diameter are considered, then the PEL for “respirable fraction†(particles small enough to reach the lungs) is 5 mg/m3.