Journal of occupational and environmental hygiene
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J Occup Environ Hyg · Jan 2015
Occupational exposures to emissions from combustion of diesel and alternative fuels in underground mining--a simulated pilot study.
Diesel fuel is commonly used for underground mining equipment, yet diesel engine exhaust is a known human carcinogen. Alternative fuels, including biodiesel, and a natural gas/diesel blend, offer the potential to reduce engine emissions and associated health effects. For this pilot study, exposure monitoring was performed in an underground mine during operation of a load-haul-dump vehicle. ⋯ Compared to diesel, GD was associated with a 66% reduction in rDPM and a reduction in all other exposures except CO. The alternative fuels tested both resulted in reduced rDPM, which is the basis for the current Mine Safety and Health Administration (MSHA) occupational exposure standard. Although additional study is needed with a wider variety of equipment, use of alternative fuels have the promise of reducing exposures from vehicular exhaust in underground mining settings.
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J Occup Environ Hyg · Jan 2014
Comparative StudyComparison of means of two lognormal distributions based on samples with multiple detection limits.
The problem of comparing the means of two lognormal distributions based on samples with multiple detection limits is considered. Tests and confidence intervals for the ratio of the two means, based on pivotal quantities involving the maximum likelihood estimators, are proposed. ⋯ The proposed approach can also be applied to find confidence intervals for the difference between the means of the two lognormal distributions. Illustrative examples with a real data set and with a simulated data set are given.
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J Occup Environ Hyg · Jan 2014
Efficacy of face shields against cough aerosol droplets from a cough simulator.
Health care workers are exposed to potentially infectious airborne particles while providing routine care to coughing patients. However, much is not understood about the behavior of these aerosols and the risks they pose. We used a coughing patient simulator and a breathing worker simulator to investigate the exposure of health care workers to cough aerosol droplets, and to examine the efficacy of face shields in reducing this exposure. ⋯ Thus, face shields provide a useful adjunct to respiratory protection for workers caring for patients with respiratory infections. However, they cannot be used as a substitute for respiratory protection when it is needed. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: tables of the experiments performed, more detailed information about the aerosol measurement methods, photographs of the experimental setup, and summaries of the experimental data from the aerosol measurement devices, the qPCR analysis, and the VPA.].
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J Occup Environ Hyg · Jan 2014
A quantitative assessment of the total inward leakage of NaCl aerosol representing submicron-size bioaerosol through N95 filtering facepiece respirators and surgical masks.
Respiratory protection provided by a particulate respirator is a function of particle penetration through filter media and through faceseal leakage. Faceseal leakage largely contributes to the penetration of particles through a respirator and compromises protection. When faceseal leaks arise, filter penetration is assumed to be negligible. ⋯ Relatively, higher efficiency N95 and SM models showed lower TIL values. Filter efficiency of FFRs and SMs influenced the TIL at different flow rates and leak sizes. Overall, the data indicate that good fitting higher-efficiency FFRs may offer higher protection against submicron-size bioaerosols.
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J Occup Environ Hyg · Jan 2014
Comparative StudySpeech intelligibility while wearing full-facepiece air-purifying respirators.
Intelligible speech communication while wearing air-purifying respirators is critical for law enforcement officers, particularly when they are communicating with each other or the public. The National Institute for Occupational Safety and Health (NIOSH) requires a 70% overall performance rating to pass speech intelligibility certification for commercial chemical, biological, radiological, and nuclear air-purifying respirators. However, the speech intelligibility of certified respirators is not reported and the impact on operational performance is unknown. ⋯ All of the tested respirators were predicted to have little impact on simple and complex mission performance times and on simple mission success rate. However, the regression equations showed that 75% of missions that require complex communications would be completed while wearing the Millennium, FR-M40, or Ultra Elite but that only 60% would be completed successfully while wearing the FR-7800B. These results suggest that some certified respirators may have a greater impact on speech communications than others.