Evaluation of Respirators for Engineered Nanoparticles

Details

• Personal Author:
  Cheng YS
• Description:
  As more engineered nanomaterials are being incorporated into products or devices, concerns about potential environmental and occupational health implications also increase. NIOSH-certified respirators, including N95 and P100 respirators, are recommended when engineering and administrative controls do not adequately prevent exposures to airborne nanomaterials. There is no information on penetration of engineered nanoparticles for the N95 and P100 filtering facepieces. The overall objective of the proposed study is to evaluate the performance of N95 and P100 respirators for respiratory protection of engineered nanoparticles and to investigate the filtration processes of nanoparticles. Commercial N95 and P100 respirators were challenged with engineered nanoparticle aerosols containing metal oxides (such as TiO2) and carbon (such as fullerenes and nanotubes) in contrast with a sodium chloride (NaCl) aerosol at flow rates of 30, 85, and 130 L/min. For new N95 respirators in general, NaCl aerosol penetration was less than 5% and the most penetrating particle size occurred at around 40 nm. Overall penetration of the engineered nanoparticle aerosols was higher for engineered nanoparticle and was often greater than 5% at and near the most penetrating particle size (MPPS), which occurred at a larger particle size range (91-154 nm). For respirators treated with isopropanol in which the electrostatic force was removed, penetration of NaCl and engineered nanoparticles increased substantially and the MPPS increased to 150 nm for both types of aerosols. Similarly, for P100 filtering facepieces (FFPs), experimental NaCl penetrations were below 0.03% for all flow rates for the untreated FFPs; whereas maximum penetrations in the ranges of 10 to 20% were obtained after the charges were removed from the respirators. Maximum penetrations of TiO2 carbon nanotube (CNT), and fullerene were higher than those measured for NaCl aerosol for two NIOSH-approved P100 FFP respirators. Theoretical calculations for the mechanical processes were first performed and compared with experimental penetration data obtained in N95 and P100 respirators treated to remove charges for NaCl particles. The measured solid volume fraction for all respirators and the adjusted solid volume fraction for polydisperse fibrous filter were used. The theoretical penetration based on the measured value of the solid volume fraction underestimated the penetration, whereas the calculated penetration values with the adjusted solid volume fraction were in reasonable agreement with the experimental data in the particle size near the maximum penetration for a filter with the electrical charges removed. Theoretical calculations of penetration considered both the mechanical and electrical single fiber efficiencies for respirators without removing charges. The estimated values of charge density were 2.4x10-5 and 1.6x10-5 C/cm2 for N95 A and N95 B respirators respectively, based on the NaCl penetration date. Theoretical calculations indicated lower penetration below 5% and a shift of the MPPS from 200 to 80 nm. Theoretical calculation of penetration using the same single fiber model equations with the measured filter characteristics also showed that, with the adjusted measured solid volume fraction, the calculation for mechanical filtration agreed reasonably well with the experimental data for treated P100 C and P100 D respirators. Detailed characterization of TiO2 and CNT particles were performed. The measured maximum lengths and aerodynamic diameter were used in the theoretical calculation of filtration. The calculations were in general agreement with the experimental data in that both respirators showing the shift of the MPPS and penetration level for the treated and untreated respirators. It also showed that for the untreated respirator, TiO2 and CNT penetrations were higher than those of NaCl, and at 130 L/min the maximum TiO2 penetration was over 5% level for the N95 respirators. The theoretical investigation showed that the lower value of dielectric constant for TiO2 and CNT as compared to 6.1 for NaCl was the main reason for higher penetration. To evaluate the respirators with leakage, a new respirator was punched with two holes on each side of the respirator with diameter of 1.0 mm, 2.0 mm, and 3.2 mm, respectively. Penetrations were often greater than 5% for leak holes of 2.0 and 3.2 mm and could go as high as 20%. Our results indicated that the penetration leaks were in general a function of ratio of the leak to total flow rates. Even though the P100 respirators had much lower penetration when sealed, when subjected to a similar leak size, the aerosol penetrations were similar to N95 respirators. [Description provided by NIOSH]
• Subjects:
  Aerosols Air Pollutants, Occupational Filtration Occupational Health Personal Protective Equipment Respiratory Protective Devices Safety
• Keywords:
  Airborne Particles Carbon Nanotubes CNT Filters Metal Oxides N95 Filtering Facepiece Respirators Nanomaterials Nanoparticles Particulate Filtering Facepiece Respirators Respirators Respirator Testing

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• Series:
  Grant Final Reports
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Final Grant Report
• Place as Subject:
  New Mexico ; OSHA Region 6
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  OEP - Office of Extramural Programs
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-74
• NIOSHTIC Number:
  nn:20053237
• NTIS Accession Number:
  PB2019-100194
• Citation:
  Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, R01-OH-010062, 2016 Nov; :1-74
• Contact Point Address:
  Yung Sung Cheng, Ph.D., Lovelace Respiratory Research Institute, 2425 Ridgecrest Dr. SE, Albuquerque, NM 87108
• Email:
  ycheng@LRRI.org
• CAS Registry Number:
  Carbon nanotubes (CAS RN 308068-56-6)
• Federal Fiscal Year:
  2017
• NORA Priority Area:
  Manufacturing
• Performing Organization:
  Lovelace Biomedical & Environmental Research Institute, Albuquerque, New Mexico
• Peer Reviewed:
  False
• Start Date:
  20120901
• Source Full Name:
  National Institute for Occupational Safety and Health
• End Date:
  20160831
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:ea76d38321346201413ef6ae114792f7e3b7ffb578e6b499b69882e639227b6f5675de69a39e07fcae6a267d7c44c4e889cfdce73eeaec5312765ef505135bce
• Download URL:
  https://stacks.cdc.gov/view/cdc/218757/cdc_218757_DS1.pdf
• File Type:
  [PDF - 7.96 MB ]