Inhalability and sampling of large particles

Inhaled large particles (10–150 μm) with systemic toxicity, such as, heavy metals, pesticides, radionuclides, or corrosive materials pose a health risk regardless of where they deposit in the respiratory tract. This research seeks to better define particle inhalability, the fraction of airborne particles that are inhaled as a function of particle size, for conditions found in occupational environments. This research also evaluated the performance of eight personal samplers for inhalable particles.; Measurements of inhalability and sampler performance were made for solid or liquid particles using an open-cycle, closed-jet, low-velocity wind tunnel. Wind tunnel air velocities were 0.4, 1.0, and 1.6 m/s. A modified full-size, full-torso mannequin was used to collect particles entering either the mouth or nose. Personal samplers were attached to the collar of the mannequin. Inhalation was simulated using a mechanical breathing machine at minute volumes of 14.2, 20.8, and 37.3 L. The mannequin either faced the oncoming wind or rotated slowly (0.06 rpm). Aerosol concentration in the test section was determined with three isokinetic samplers. At the test section, air velocity was uniform to within 10% and aerosol concentration was uniform to within 15%.; For particles larger than 50 μm, orientation-averaged mouth inhalability for both solid and liquid particles was significantly lower than the IPM criterion and the liquid particle results were 50% lower than the solid particle results. Facing-the-wind mouth inhalability was higher than the orientation-averaged results for both liquid and solid particles. For d_a > 50 μm, inhalability for solid particles was 4 times that of liquid particles. Wind velocity and breathing pattern had little effect on solid particle inhalabilty. Wind velocity did influence liquid particle inhalability. Nose inhalability is significantly different in trend and shape than mouth inhalabilty. Particle bounce seems to affect inhalabilty for solid particles larger than 50 μm. Two samplers showed good agreement with the IPM criterion: the IOM inhalable sampler and the 37-mm inline sampler with an 8-mm inlet positioned to face forward.