Ulltrafine particles include particles smaller than 0.1 μm sizes, which can penetrate deep into our lungs. Exposure to high concentrations of airborne ultrafine particles in construction jobsites including silica nanoparticles may play an important role in the adverse health effects among construction workers, therefore adequate respiratory protection is required. The performance of NIOSH-approved N95 masks has never been evaluated in field conditions against ultrafine particles on construction jobsites.
A recent Georgia Southern field study, led by Dr. Atin Adhikari, has evaluated performance of N95 masks against ultrafine particles of different size ranges during three common construction related jobs using a manikin-based set-up at 85 L/min air flow rate. The researchers used two NanoScan SMPS (Scanning Mobility Particle Sizer Spectrometer) nanoparticle counters for measuring ultrafine particles in two sampling lines of the test filtering facepiece respirator — one from inside the respirator and one from outside the respirator. Particle size distributions were characterized using the NanoScan data collected from outside of the respirator. Two models of N95 respirators were tested — foldable and pleated. Collected data indicate that penetration of all categories of ultrafine particles can exceed 5 percent and smaller ultrafine particles of <36.5 nm size generally penetrated least. Foldable N95 filtering facepiece respirators were found to be less efficient than pleated N95 respirators in filtering nanoparticles mostly at the soil moving site and the wooden building frameworks construction site. Upon charge neutralization by isopropanol treatment, the ultrafine particles of larger sizes penetrated more compared to particles of smaller sizes. The findings from the field experiments, therefore, indicate that N95 filtering facepiece respirators may not provide desirable 95 percent protection for most categories of ultrafine particles and generally, 95 percent protection is achievable for smaller particles of 11.5 to 20.5 nm sizes. The study also provides evidence showing that foldable N95 respirators are less efficient than pleated N95 respirators in filtering ultrafine particles, mostly in the soil moving site and the wooden building framework construction site. This work has been financially supported by the CPWR (The Center for Construction Research and Training) through NIOSH (National Institute for Occupational Safety and Health) cooperative agreement OH009762 (PI: Dr. Adhikari).
“Field Evaluation of N95 Filtering Facepiece Respirators on Construction Jobsites for Protection against Airborne Ultrafine Particles” was recently published in The Journal of Environmental Research and Public Health.
Authors are Dr. Atin Adhikari, Jiann-Ping Hsu Georgia Southern University (GSU) College of Public Health (JPHCOPH), Dr. Aniruddha Mitra, Department of Mechanical Engineering, GSU, Dr. Abbas Rashidi, Department of Civil and Environmental Engineering, University of Utah, and GSU graduate and undergraduate students Ms. Imaobong Ekpo, JPHCOPH, Jacob Schwartz, Department of Manufacturing Engineering, Mr. Jefferson Doehling, Department of Mechanical Engineering.