Eninger Robert M, Honda Takeshi, Reponen Tiina, McKay Roy, Grinshpun Sergey A
Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio.
J Occup Environ Hyg. 2008 May;5(5):286-95. doi: 10.1080/15459620801960153.
Recent interest in exposures to ultrafine particles (less than 100 nm) in both environmental and occupational settings led the authors to question whether the protocols used to certify respirator filters provide adequate attention to ultrafine aerosols. The authors reviewed the particle size distribution of challenge aerosols and evaluated the aerosol measurement method currently employed in the National Institute for Occupational Safety and Health (NIOSH) particulate respirator certification protocol for its ability to measure the contribution of ultrafine particles to filter penetration. Also considered were the differences between mechanical and electrically charged (electret) filters in light of the most penetrating particle size. It was found that the sodium chloride (NaCl) and dioctylphthalate (DOP) aerosols currently used in respirator certification tests contain a significant fraction of particles in the ultrafine region. However, the photometric method deployed in the certification test is not capable of adequately measuring light scatter of particles below approximately 100 nm in diameter. Specifically, 68% (by count) and 8% (by mass) of the challenge NaCl aerosol particles and 10% (by count) and 0.3% (by mass) of the DOP particles below 100 nm do not significantly contribute to the filter penetration measurement. In addition, the most penetrating particle size for electret filters likely occurs at 100 nm or less under test conditions similar to those used in filter certification. The authors conclude, therefore, that the existing NIOSH certification protocol may not represent a worst-case assessment for electret filters because it has limited ability to determine the contribution of ultrafine aerosols, which include the most penetrating particle size for electret filters. Possible strategies to assess ultrafine particle penetration in the certification protocol are discussed.
近期，环境和职业环境中对超细颗粒（小于100纳米）暴露的关注，促使作者质疑用于认证呼吸器过滤器的协议是否充分关注了超细气溶胶。作者回顾了挑战气溶胶的粒径分布，并评估了美国国家职业安全与健康研究所（NIOSH）颗粒物呼吸器认证协议中目前采用的气溶胶测量方法，以确定其测量超细颗粒对过滤器穿透率贡献的能力。还根据最易穿透粒径，考虑了机械过滤器和带电（驻极体）过滤器之间的差异。研究发现，呼吸器认证测试中目前使用的氯化钠（NaCl）和邻苯二甲酸二辛酯（DOP）气溶胶包含相当一部分超细区域的颗粒。然而，认证测试中采用的光度法无法充分测量直径约100纳米以下颗粒的光散射。具体而言，直径小于100纳米的挑战NaCl气溶胶颗粒中，按数量计68%和按质量计8%，以及DOP颗粒中按数量计10%和按质量计0.3%，对过滤器穿透率测量没有显著贡献。此外，在与过滤器认证所用条件类似的测试条件下，驻极体过滤器的最易穿透粒径可能出现在100纳米或更小。因此，作者得出结论，现有的NIOSH认证协议可能无法代表驻极体过滤器的最坏情况评估，因为它确定超细气溶胶贡献的能力有限，而超细气溶胶包括驻极体过滤器的最易穿透粒径。文中还讨论了在认证协议中评估超细颗粒穿透率的可能策略。
