Effectiveness of N95 respirators for nanoparticle exposure control (2000–2016): a systematic review and meta-analysis

  • Mmamolapo Getrude Lebogang Ntlailane
  • Janine Wichmann


Workers are increasingly exposed to nanoparticles, mostly via inhalation. Respiratory protection is recommended as an additional control measure. Particulate respirators are certified for protection against micro-sized particles, where a most penetrating particle size (MPPS) of 100–400 nm is assumed. Commonly used N95 respirators are certified by the National Institute for Occupational Safety and Health after passing a 95% collection efficiency test. Electret media used in respirators have been demonstrated to be shifting the MPPS to a nanosized region. Experimental studies have therefore been conducted to assess N95 respirator penetration specifically by nanoparticles. This systematic review and meta-analysis was aimed at systematically reviewing these studies and meta-analysing the mean penetration percentage (PP). The review was conducted following a Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline. Fourteen studies were selected to be reviewed qualitatively, while 13 of these with 29 data points were included in the meta-analysis. Sensitivity analysis was performed based on a respirator mounting protocol, while subgroup analysis was done for aerosol dispersity and repeated for the respirator mounting protocol. The size range of particles used across the reviewed studies was 1 nm–10 μm. The MPPS for all studies was in the nanosized particle range, with the lowest at approximately 39 nm. The estimated mean PP was between 1 and 6%, exceeding the 5% guideline threshold for four of the studies. All the meta-analysed mean PPs were however below the 5% guideline. This means that the N95 respirators may be effective for nanoparticles in workplaces, but subject to factors including respirator characteristics and particle dispersity.


Nanoparticles N95 respirator Effectiveness Penetration Exposure control Protection Environmental Health and safety issues 


Compliance with ethical standards

Approval to conduct the review was granted by the Research Ethics Committee (REC) of the Faculty of Health Sciences, University of Pretoria, reference number 234/2016.

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.School of Health Systems and Public Health, Faculty of Health SciencesUniversity of PretoriaPretoriaSouth Africa
  2. 2.Occupational Hygiene Section, National Institute for Occupational HealthNational Health Laboratory ServicesJohannesburgSouth Africa

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