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High Flow, Extended-Wear Respirators for Ambient Particulate Matter Protection


OBJECTIVE: Develop a rugged, novel particulate respirator or dust mask that is suitable for extended wear in military operational environments with high particulate matter levels during aerobic activity. DESCRIPTION: Adverse health effects, including cardiovascular and pulmonary disease, are well-documented consequences of exposure to high levels of PM with aerodynamic diameter of less than 10 m (PM10) and especially less than 2.5 m (PM2.5). In many deployed environments, including regions of Southwest Asia (SWA), military personnel are continually exposed under normal conditions to levels of PM that exceed the military exposure guidelines (MEG) (1). These levels can be greatly exaggerated by anthropogenic activity or dust storms. There is a growing concern among pulmonologistsbased primarily on anecdotal evidencethat exposures in SWA are leading to degraded respiratory function in a large number of service members (2). While operations in SWA have highlighted the risk, many military operations worldwide suffer the same burden. Unfortunately, current dust mask and respirator technologies are not suitable for extended wear during military operations (3,4), which require high levels of aerobic activity over sustained periods. The primary complaint which limits use of masks and respirators is discomfort caused by breathing resistance (5). Further, due to the extreme levels of PM in some deployed settings, there is the recurring issue of clogging, which adds an additional logistics burden when masks need to be continually replaced. The objective of this project is to develop a rugged, novel particulate respirator or dust mask that is suitable for extended wear and significantly reduces the amount of dust respired in operational environments with high particulate matter levels, such as Southwest Asia. The ideal respirator shall allow high flow volumes with a minimal breathing resistance (sometimes called airflow resistance or pressure drop) and shall be suitable for wear during aerobic activity. It must also be resistant to clogging. Any technology capable of meeting the performance criteria will be considered. Priority shall be given to innovative or novel designs with minimal size and weight that are fully self-contained and have minimal to no power requirements. PHASE I: Develop and demonstrate a filtration technology that significantly reduces PM10 and PM2.5 levels and is suitable for integration into a wearable device. The technology must be tested in a high PM environment (using polydispersed aerosol particles from 0.1-10 m and concentrations of>150 g/m3 PM10 and>40 g/m3 PM2.5). Minimum operating characteristics for the Phase I demonstration include a low breathing resistance (<5 mm of water inhale and<3 mm of water exhale) at a moderate flow rate (85 L/min), a reduction of respirable particulate concentrations by greater than 90%, and a resistance to clogging for 12 hours (<2x increase in breathing resistance in high PM environment challenge). The technical feasibility of improving the performance characteristics to levels indicated in Phase II should also be determined. PHASE II: Develop and demonstrate a prototype particulate respirator or dust mask using the filtration technology develop in Phase I that meets or exceeds the following characteristics when tested in a high PM environment (using polydispersed aerosol particles from 0.1-10 m and concentrations of>150 g/m3 PM10 and>40 g/m3 PM2.5) at a flow rate of 150 L/min: 1) Breathing resistance<3 mm of water inhale and<2 mm of water exhale 2) Respirable particle penetration of<5 % 3) Resistance to clogging for 24 hours (<2x increase in breathing resistance in high PM environment challenge) Any reduction in exposure provided by a dust mask or respirator is dependent upon having a product that fits closely to the face and is correctly donned and worn. In order to address the need for proper fit, a fit assessment must demonstrate fit and the ability to easily don and doff the device. The fit characteristics of the device should be tested using a quantitative fit testing against a panel of human test subjects that adequately represent the intended users of the device. Examples of test panels include the Bivariate Panel, recently described by NIOSH"s National Personal Protective Technology Laboratory (NPPTL), and the older Los Alamos National Laboratory Panel (6). The product should have a fit factor of at least 10 for 95% of the subjects. To further accommodate the recurring daily use of the device, the prototype should be designed to ensure comfortable fitting with minimal facial abrasions due to extended wear under conditions with high levels of dirt, grit, or sand. The weight of the face mask should be less than 4 oz. The design must be user serviceable and any replaceable parts must be reusable for at least 30 days. In addition, a plan must be proposed on how to create a rugged design that is suitable for military operational use. PHASE III: The overall goal of the project is to develop a NIOSH N95 compliant particulate respirator that has extreme performance characteristics for low breathing resistance and resistance to clogging. A ruggedized, military model suitable for field use has the potential to become standard issue to all troops deployed in dusty environments, including SWA. A commercial version will find a market across the hundreds of industries that require respirator use due to high dust levels (e.g. agriculture, construction, mining), but where compliance with use is limited due to poor performance characteristics. REFERENCES: 1) Weese, CB and JH Abraham"Potential Health Implications Associated with Particulate Matter Exposure in Deployed Settings in Southwest Asia"INHAL TOXICOL: Mar 2009, Vol. 21, No. 4: 291296. 2) Szema, AM, et al."Respiratory Symptoms Necessitating Spirometry Among Soldiers With Iraq/Afghanistan War Lung Injury"JOEM: Sep 2011, Vol. 53, No. 9, 961-965. 3) Heus, R, et al."Influence of inspiratory resistance on performance during graded exercise tests on a cycle ergometer"APPL ERGON: Nov 2004, Vol. 35, No. 6, 583-590. 4) Caretti, DM."Performance Decrements in Constant Load Work for Specific Inspiratory and Expiratory Breathing Resistances"Final rept. Aug 94-Mar 95, 5) Chia, SE."A Study on the Usage of Respirators Among Grannite Quarry Workers in Singapore"SING MED J: 1989, Vol. 30, 269-272. 6) Zhuang, Z, et al."New Respirator Fit Test Panels Representing the Current U.S. Civilian Work Force"JOEH: Sep 2007, Vol. 4, 647-659.
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