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Particulates Not Otherwise Regulated (Respirable Fraction)

General Description

  • Synonyms: Dust (respirable nuisance); "Inert" dusts; Nuisance dusts; PNOR (Note: includes all inert or nuisance dusts, whether mineral, inorganic, not listed specifically in 1910.1000)
  • OSHA IMIS Code Number: 9130 (IMIS Name History: Dust [respirable nuisance] prior to 9/1/89)
  • NIOSH Pocket Guide to Chemical Hazards - Particulates Not Otherwise Regulated: Physical description, chemical properties, potentially hazardous incompatibilities, and more

Exposure Limits and Health Effects

Exposure Limit Limit Values HE Codes Health Factors and Target Organs
  • 5 mg/m3
  • (15 mppcf*)
  • TWA


Lung disease

Not established



Not established



  • National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL)
  • See Appendix D

Not established



  • American Conference of Governmental Industrial Hygienists (ACGIH) Guideline
  • 3 mg/m3
  • (respirable particles)


Lung disease, with compromised airway clearance


  • 5 mg/m3
  • TWA



*mppcf = Millions of particles per cubic foot of air

  • National Toxicology Program (NTP) carcinogenic classification: Not listed
  • International Agency for Research on Cancer (IARC) carcinogenic classification: Not listed
  • U.S. Environmental Protection Agency (EPA) carcinogenic classification: Not listed
  • EPA Inhalation Reference Concentration (RfC): Not established
  • Agency for Toxic Substances and Disease Registry (ATSDR) Inhalation Minimal Risk Level (MRL): Not established
  • NIOSH Immediately Dangerous to Life or Health (IDLH) concentration: Not established
  • Notes on Other Potential Health Effects and Hazards
    1. Exposure to dusts may to decrease pulmonary function (Shieh et al. 2012).
  • Date Last Revised: 9/6/2012
  • Literature Basis:
    • ACGIH: Documentation of the Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) - Particulates (Insoluble) Not Otherwise Specified (PNOS). 2001.
    • Shieh, T.S., Chung, J.J., Wang, C.J., Tsai, P.J., Kuo, Y.C., Guo, H.R.: Pulmonary function, respiratory symptoms, and dust exposure among workers engaged in early manufacturing processes of tea: a cohort study. BMC Public Health. 12:121, Feb 13, 2012.

Monitoring Methods used by OSHA

Laboratory Sampling/Analytical Method:
  • tared (pre-weighed) 37-mm diameter low-ash polyvinyl chloride filter preceded by 10 mm Nylon Cyclone
  • maximum volume: 816 Liters
  • minimum volume: 408 Liters
  • maximum flow rate: 1.7 L/min
  • current analytical method: Gravimetric
  • method reference: OSHA Analytical Method (OSHA PV2121)
  • method classification: Partially Validated
  • note: OSHA personnel can obtain tared sampling media from SLTC.
  • note: If the filter is not overloaded, samples can be collected up to an 8-hour period.

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