Last data update: May 13, 2024. (Total: 46773 publications since 2009)
Records 1-5 (of 5 Records) |
Query Trace: Pearce TA[original query] |
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Assessment of two portable real-time particle monitors used in nanomaterial workplace exposure evaluations
Liu Y , Beaucham CC , Pearce TA , Zhuang Z . PLoS One 2014 9 (8) e105769 BACKGROUND: Nanoparticle emission assessment technique was developed to semi-quantitatively evaluate nanomaterial exposures and employs a combination of filter based samples and portable real-time particle monitors, including a condensation particle counter (CPC) and an optical particle counter (OPC), to detect nanomaterial releases. This laboratory study evaluated the results from CPC and OPC simultaneously measuring a polydisperse aerosol to assess their variability and accuracy. METHODS AND RESULTS: Two CPCs and two OPCs were used to evaluate a polydisperse sodium chloride aerosol within an enclosed chamber. The measurement results for number concentration versus time were compared between paired particle monitors of the same type, and to results from the Scanning Mobility Particle Spectrometer (SMPS) which was widely used to measure concentration of size-specific particles. According to analyses by using the Bland-Altman method, the CPCs displayed a constant mean percent difference of -3.8% (95% agreement limits: -9.1 to 1.6%; range of 95% agreement limit: 10.7%) with the chamber particle concentration below its dynamic upper limit (100,000 particles per cubic centimeter). The mean percent difference increased from -3.4% to -12.0% (range of 95% agreement limits: 7.1%) with increasing particle concentrations that were above the dynamic upper limit. The OPC results showed the percent difference within 15% for measurements in particles with size ranges of 300 to 500 and 500 to 1000 regardless of the particle concentration. Compared with SMPS measurements, the CPC gave a mean percent difference of 22.9% (95% agreement limits: 10.5% to 35.2%); whereas the measurements from OPC were not comparable. CONCLUSIONS: This study demonstrated that CPC and OPC are useful for measuring nanoparticle exposures but the results from an individual monitor should be interpreted based upon the instrument's technical parameters. Future research should challenge these monitors with particles of different sizes, shapes, or composition, to determine measurement comparability and accuracy across various workplace nanomaterials. |
Quantity and size distribution of cough-generated aerosol particles produced by influenza patients during and after illness
Lindsley WG , Pearce TA , Hudnall JB , Davis KA , Davis SM , Fisher MA , Khakoo R , Palmer JE , Clark KE , Celik I , Coffey CC , Blachere FM , Beezhold DH . J Occup Environ Hyg 2012 9 (7) 443-9 The question of whether influenza is transmitted to a significant degree by aerosols remains controversial, in part, because little is known about the quantity and size of potentially infectious airborne particles produced by people with influenza. In this study, the size and amount of aerosol particles produced by nine subjects during coughing were measured while they had influenza and after they had recovered, using a laser aerosol particle spectrometer with a size range of 0.35 to 10 mcm. Individuals with influenza produce a significantly greater volume of aerosol when ill compared with afterward (p = 0.0143). When the patients had influenza, their average cough aerosol volume was 38.3 picoliters (pL) of particles per cough (SD 43.7); after patients recovered, the average volume was 26.4 pL per cough (SD 45.6). The number of particles produced per cough was also higher when subjects had influenza (average 75,400 particles/cough, SD 97,300) compared with afterward (average 52,200, SD 98,600), although the difference did not reach statistical significance (p = 0.1042). The average number of particles expelled per cough varied widely from patient to patient, ranging from 900 to 302,200 particles/cough while subjects had influenza and 1100 to 308,600 particles/cough after recovery. When the subjects had influenza, an average of 63% of each subject's cough aerosol particle volume in the detection range was in the respirable size fraction (SD 22%), indicating that these particles could reach the alveolar region of the lungs if inhaled by another person. This enhancement in aerosol generation during illness may play an important role in influenza transmission and suggests that a better understanding of this phenomenon is needed to predict the production and dissemination of influenza-laden aerosols by people infected with this virus. [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 resources: a PDF file of demographic information, influenza test results, and volume and peak flow rate during each cough and a PDF file containing number and size of aerosol particles produced.] |
Effect of an interferent on the performance of two direct-reading organic vapor monitors
LeBouf RF , Rossner A , Hudnall JB , Slaven JE , Calvert CC , Pearce TA , Coffey CC . J Emerg Manag 2010 8 (5) 72-80 Direct-reading organic vapor monitors (DROVMs) are widely used by industrial hygienists and emergency responders as survey tools for the assessment of volatile organic compounds (VOCs) in occupational or emergency response settings. Although these monitors provide real-time information for expedient decision making, their utility in determining compliance with specific exposure limits is not well established. In addition, other VOCs that may be present in the same environment can act as interferents and adversely affect performance. This study assessed the effect of an interferent (hexane) on the performance of two representative commercially available monitors when measuring cyclohexane. The instrument readings were compared with concentrations measured with sorbent tubes, a standard compliance monitoring technique. Infrared-based concentration measurements were more precise at the two middle challenge concentrations (144 and 289 ppm), indicating a shift in instrument precision at the low and high end of the recommended operating range. Both photoionization detection and infrared-based concentration measurements were affected by the presence and amount of hexane in the test atmosphere. Emergency response personnel and industrial hygienists should be aware of the limitations of DROVMs in the assessment of hazardous situations involving VOCs. |
Direct-reading methods for workplace air monitoring
Coffey CC , Pearce TA . J Chem Health Saf 2010 17 (3) 10-21 Direct-reading methods (DRMs) are valuable tools for detecting and measuring worker exposure to inhalation hazards. A DRM can be either a device or instrument capable of measuring gases and vapors and aerosols such as dusts, fumes, and mists without manipulation of the sample by the user or sending the sample to an offsite laboratory. Devices are those DRMs that are simple, single point in time measurement of exposure. Instruments are DRMs that contain a sampling system, signal-processing electronics, a display system, and a detector. This manuscript will describe the DRMs which may be used to evaluate worker exposure to gases, vapors, and aerosols. The manuscript will also discuss factors to consider when selecting a DRM and recent developments and events related to DRMs. |
Distribution of airborne influenza virus and respiratory syncytial virus in an urgent care medical clinic
Lindsley WG , Blachere FM , Davis KA , Pearce TA , Fisher MA , Khakoo R , Davis SM , Rogers ME , Thewlis RE , Posada JA , Redrow JB , Celik IB , Chen BT , Beezhold DH . Clin Infect Dis 2010 50 (5) 693-8 BACKGROUND: Considerable controversy exists with regard to whether influenza virus and respiratory syncytial virus (RSV) are spread by the inhalation of infectious airborne particles and about the importance of this route, compared with droplet or contact transmission. METHODS: Airborne particles were collected in an urgent care clinic with use of stationary and personal aerosol samplers. The amounts of airborne influenza A, influenza B, and RSV RNA were determined using real-time quantitative polymerase chain reaction. Health care workers and patients participating in the study were tested for influenza. RESULTS: Seventeen percent of the stationary samplers contained influenza A RNA, 1% contained influenza B RNA, and 32% contained RSV RNA. Nineteen percent of the personal samplers contained influenza A RNA, none contained influenza B RNA, and 38% contained RSV RNA. The number of samplers containing influenza RNA correlated well with the number and location of patients with influenza ([Formula: see text]). Forty-two percent of the influenza A RNA was in particles 4.1 mum in aerodynamic diameter, and 9% of the RSV RNA was in particles 4.1 mum. CONCLUSIONS: Airborne particles containing influenza and RSV RNA were detected throughout a health care facility. The particles were small enough to remain airborne for an extended time and to be inhaled deeply into the respiratory tract. These results support the possibility that influenza and RSV can be transmitted by the airborne route and suggest that further investigation of the potential of these particles to transmit infection is warranted. |
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