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A new method to evaluate respiratory protection provided by N95 respirators against airborne dust and microorganisms in agricultural farms.

Lee-SA; Adhikari-A; Grinshpun-SA; Reponen-T
Proceedings of the AAAR 23rd Annual Conference, October 4-8, 2004, Atlanta, Georgia. Mount Laurel, NJ: American Association for Aerosol Research, 2004 Oct; :293
Airborne dust and microorganisms are ubiquitous in agricultural farms. Farmers are known to be at high risk of getting respiratory health problems, such as asthma, allergies, bronchitis, and decreased lung function because of high exposures to airborne particles and microorganisms. Respiratory protection is often the only feasible option to prevent farmers' exposure against these air contaminants considering of the diverse nature of the dust and bioaerosol sources in agricultural farms. Respiratory protection strategies against bioaerosols in agricultural environments remain poorly investigated. In this study, a prototype personal sampling set-up was developed for determining the protection provided by N95 respirators against non-biological and biological particles in the size range of 0.7 - 10 microm. This size range covers respirable and thoracic dust particles as well as most bacteria and fungal spores. The set-up was designed for the measurement of aerosol particles inside and outside the respirator in real-time by two optical particle counters (OPCs) and the simultaneous collection of microorganisms by two filter samplers for subsequent analysis by microscopic counting and/or cultivation. Extensive laboratory evaluation confirmed that the set-up can detect changes in the protection factors caused by variation in faceseal leaks, human activity, and breathing pattern. In the field study, the human subject donned a N95 respirator and the set-up during the farming activities: animal feeding in a swine and a dairy farm, routine investigation of facilities in a poultry farm, grain harvesting in two corn fields and in a soybean field, and soybean unloading near a silo. As expected, the protection factors provided by N95 respirators against airborne dust and microorganisms were found to be associated with the particle size. The geometric means (GM) of protection factors were 21 for 0.7 - 1 microm particles, 28 for 1 - 2 microm particles, 51 for 2 - 3 microm particles, 115 for 3 - 5 microm particles, and 270 for 5 - 10 microm particles. The difference in the protection factor for particles in the five above-indicated size ranges was statistically significant (ANOVA test; p < 0.0001). The protection factor for total culturable fungi (GM = 35) was significantly greater than for total culturable bacteria (GM = 9) (t-test; p = 0.0144). The protection factor for total fungi and Cladosporium analyzed by microscope showed a significant correlation with the protection factor for particles measured by OPCs in the size range of 2 - 10 microm (r = 0.50) and 5 - 10 microm (r = 0.61), respectively. These results can be used to provide information for establishing the regulations concerning the respiratory protection against airborne dust and microorganisms in agricultural environments. The method developed can be used for further epidemiological and intervention studies in agricultural and other environments.
Laboratory-testing; Sampling; Sampling-methods; Respirators; Respiratory-protective-equipment; Airborne-dusts; Airborne-particles; Microorganisms; Personal-protective-equipment; Inhalation-studies; Leak-prevention; Leak-detectors; Breathing; Agriculture
Department of Environmental Health, University of Cincinnati, P.O. Box 670056, Cincinnati, OH 45267-0056, USA
Publication Date
Document Type
Abstract; Conference/Symposia Proceedings
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Priority Area
Research Tools and Approaches: Control Technology and Personal Protective Equipment
Source Name
Proceedings of the AAAR 23rd Annual Conference, October 4-8, 2004, Atlanta, Georgia
Performing Organization
University of Cincinnati