of Analytical Methods NMAM 5th Edition

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Sampling and Characterization of Bioaerosols,1 Introduction. Bioaerosols are airborne particles that originate from biological sources including animals. plants fungi bacteria protozoa and viruses Examples of bioaerosols encountered in. occupational environments include plant pollen algae fungal spores bacteria such as. actinomycetes droplets produced during coughing and sneezing that may contain bacteria. and viruses dust containing insect excreta animal dander and fragments derived from each. of these sources Bioaerosols are ubiquitous and can be isolated from indoor outdoor and. occupational environments using a variety of methods that either enumerate viable or a. collection of viable and non viable bioaerosols Photomicrographs of example viral bacterial. fungal and plant bioaerosols are presented in Figure 1. Bioaerosol monitoring is a rapidly emerging area of industrial hygiene due to the improved. analysis methods such as polymerase chain reaction PCR and the impact that occupational. exposures may have on worker respiratory health particularly in microbial contaminated. environments Eduard et al 2012 Environment Agency 2009 Haig et al 2016 Hung et al. 2005 Macher 1999 Morey 2007 Nazaroff 2016 Some human diseases encountered in. healthcare settings such as measles and tuberculosis can be spread by bioaerosols containing. infectious microorganisms Ijaz et al 2016 Jones and Brosseau 2015 Soil saprophytic fungi. such as Coccidioides immitis can be aerosolized during occupational disturbance activities. and if inhaled can result in an acute pulmonary infection Das et al 2012 Wilken et al 2014. Wilken et al 2015 The measurement of these bioaerosols in industrial hygiene includes the. measurement of viable culturable and non culturable and nonviable bioaerosols in indoor. settings e g industrial office education and residential buildings industrial facilities e g. biotechnology composting waste disposal manufacturing textile and food processing and. outdoor environments e g farms feed lots and general air quality Monitoring for. bioaerosols in the occupational environment is one of the many tools the industrial hygienist. uses in the assessment of indoor air quality infectious disease outbreaks agricultural. exposures and industrial health, Bioaerosol monitoring may be appropriate during workplace health and exposure. assessments epidemiological investigations research studies or in situations deemed. appropriate by an occupational physician or immunologist Sampling can also be used to. evaluate occupational environments before and after mitigation of microbial contaminants. When investigating bioaerosols as a possible source of workplace exposures and health issues. bioaerosol sampling should be part of an integrated assessment of work conditions This. should also include examining heating ventilation and air conditioning HVAC systems. checking for water infiltration and moisture control evaluating microbial contamination in. evaporative cooling systems metal working fluids and waste water evaluating possible. NIOSH Manual of Analytical Methods 5th Edition Chapter BA March 2017 Page BA 2 of BA 115. Sampling and Characterization of Bioaerosols, internal and external sources of bioaerosols and other measures Macher 1999 In general if. visible growth or contamination microbial growth on floors walls or ceilings or in the. HVAC system is observed this normally should be mitigated first before indoor bioaerosol. sampling is conducted If personnel remain symptomatic after remediation air sampling may. be appropriate but the industrial hygienist should be aware that false negative results are. possible and should be interpreted with caution, The industrial hygienist has a variety of tools and methodologies available to conduct an. environmental survey ASTM 2014a Flannigan et al 2011 Hung et al 2005 However many. of these approaches have lacked standardization and this has made the interpretation and. comparison between studies challenging Flannigan et al 2011 In 2005 the American. Industrial Hygiene Association AIHA published the second edition of the Field Guide for. the Determination of Biological Contaminants in Environmental Samples Hung et al 2005. This reference provides the industrial hygienist access to the most up to date methods to. detect and quantify bioaerosols in the environment and covers methods of how to conduct a. survey sample bioaerosols and interpret the collected data Hung et al 2005 Similarly other. reference sources have been published by Flannigan et al 2011 and the American. Conference of Governmental Industrial Hygienists ACGIH Macher 1999 that extensively. outline available methods to analyze collected bioaerosols as well as strategies to conduct an. environmental survey ASTM International has issued a wide range of standards on indoor air. quality including assessment of fungal growth and collection of bioaerosols and a guide to. developing an air sampling strategy ASTM 2009 ASTM 2014a ASTM 2014b ASTM 2014d. The European Committee for Standardization has also published standards on sampling for. bioaerosols and related topics CEN 2000 CEN 2003 CEN 2004 The sections presented. below provide a very broad overview of the viable and non viable methods available to detect. bioaerosol sources that are described in the references listed above. NIOSH Manual of Analytical Methods 5th Edition Chapter BA March 2017 Page BA 3 of BA 115. Sampling and Characterization of Bioaerosols, Figure 1 Photomicrographs of acellular prokaryotic and eukaryotic microorganisms that can.
be encountered in occupational or industrial environments A Transmission electron. micrograph of Influenza flu H1N1 virus particles Photo courtesy of National Institute of. Allergy and Infectious Diseases CDC Public Health Image Library PHIL ID 18156 B. Scanning electron micrograph of bacilli derived from the Gram negative bacteria Legionella. pneumophila Photo courtesy of National Institute of Allergy and Infectious Diseases CDC. Public Health Image Library PHIL ID 11150 C Scanning electron micrograph of. Aspergillus species reproductive structures including chains of asexual spores Photo courtesy. of CDC Robert Simmons CDC Public Health Image Library PHIL ID 13367 and D. Scanning electron micrograph of tricolpate pollen derived from the angiosperm plant species. Oenothera fruticosa Photo courtesy of CDC Janice Carr Betsy Crane CDC Public Health. Image Library PHIL ID 8729 The CDC Public Health Image Library at. http phil cdc gov Phil home asp has thousands of health related images available to the. public free of charge, NIOSH Manual of Analytical Methods 5th Edition Chapter BA March 2017 Page BA 4 of BA 115. Sampling and Characterization of Bioaerosols,2 Principles of bioaerosol collection. a Aerodynamic diameter, The aerodynamic diameter of an airborne particle usually written as da or dae is the. single most important parameter that determines how the particle will behave in the air. including how long it will stay airborne and where it will deposit in the respiratory system. if inhaled If a particle is falling in still air it will reach an equilibrium velocity where the. gravitational force pulling it downward is balanced by the drag force on its surface This. velocity is called the terminal settling velocity and it depends upon the size shape and. density of the particle The aerodynamic diameter of a particle is defined as the diameter of. a sphere with unit density that is a density of 1 g cm3 that has the same terminal settling. velocity as the particle Consider for example the irregularly shaped fungal fragment. shown in Figure 2 Suppose this particle has a terminal settling velocity of 0 05 cm sec. This is the same settling velocity as that of a spherical particle with a unit density that has a. diameter of 4 m Thus the fungal fragment is said to have an aerodynamic diameter of 4. m Similarly a different particle with a terminal settling velocity of 1 21 cm sec has an. aerodynamic diameter of 20 m since a 20 m unit density sphere settles at that rate It is. important to note that the aerodynamic diameter may be very different from the physical. size of a particle A very dense and compact particle may have an aerodynamic diameter. much larger than its actual dimensions while a very light particle or one with fibrous. branches may have an aerodynamic diameter that is much smaller than its physical size It. is possible for two particles to have very different shapes and physical sizes but have the. same aerodynamic diameter Conversely two particles may have similar physical sizes but. have very different aerodynamic diameters A more detailed discussion of the. aerodynamic diameter can be found in Hinds 1999 and Vincent 2007. NIOSH Manual of Analytical Methods 5th Edition Chapter BA March 2017 Page BA 5 of BA 115. Sampling and Characterization of Bioaerosols, Figure 2 Aerodynamic diameter of an aerosol particle In this case the fungal fragment on. the left is said to have an aerodynamic diameter of 4 m since it falls at the same terminal. settling velocity as a 4 m sphere with a unit density. Aerodynamic diameter is used in aerosol science because particles with the same. aerodynamic diameter tend to move and be collected in the same ways For example two. particles with the same aerodynamic diameter will have the same likelihood of being. collected by an impaction aerosol sampler even if they have different physical and. morphological characteristics For this reason the performance of aerosol collection. devices is usually described by giving the aerodynamic diameter of the particles that will be. b Collection efficiency and cut off diameter, The collection efficiency of an aerosol sampler is the fraction of the aerosol particles of a.
particular aerodynamic diameter that will be collected by the sampler For example if 95. of the airborne particles with a 2 m aerodynamic diameter that enter the sampler are. deposited in the collection fluid or on the collection surface then the sampler is said to. have a 95 collection efficiency for 2 m particles, Most commonly used aerosol filters have a high collection efficiency for particles of all. sizes NIOSH 2016b However impactors cyclones and impingers use the inertia of. airborne particles to separate them from the air stream and thus they have a high. collection efficiency for particles with larger aerodynamic diameters and a low collection. efficiency for smaller ones Figure 3 Hering 2001 Hinds 1999 Marple and Olson 2011. These devices are said to have a cut off diameter that is particles with an aerodynamic. NIOSH Manual of Analytical Methods 5th Edition Chapter BA March 2017 Page BA 6 of BA 115. Sampling and Characterization of Bioaerosols, diameter larger than the cut off diameter are collected while particles with an aerodynamic. diameter less than the cut off diameter are not collected and pass through the device A. perfect collection device would have a 100 collection efficiency for particles larger than. the cut off diameter and 0 for smaller particles In practice this is not the case the. collection efficiency curve for an inertia based sampler looks like the example curve shown. in Figure 3 The aerodynamic diameter at which the collection efficiency is 50 is defined. as the cut off diameter usually written as d50 A device with a more abrupt transition. from 100 to 0 collection efficiency that is closer to the ideal device is said to have a. sharp cut off, For a given inertial collection device the 50 cut off diameter depends upon the air. flowrate through the device Increasing the flowrate will decrease the d50 and shift the. collection efficiency curve to the left while decreasing the flowrate will increase the d50 and. shift the collection efficiency curve to the right For example the first stage of the NIOSH. two stage cyclone aerosol sampler has a d50 of 4 9 m at 2 liters minute of air flow 4 1 m. at 3 5 liters minute and 2 1 m at 10 liters minute Blachere et al 2009 For this reason it. is important to check the air flowrate before aerosol sampling and control it during. sampling so that the particles are correctly segregated by size. Figure 3 Example collection efficiency curve for an inertia based aerosol sampler Note. that the collection efficiency is high for particles with large aerodynamic diameters and. low for small particles In this example the 50 cut off diameter d50 for this device is 1. NIOSH Manual of Analytical Methods 5th Edition Chapter BA March 2017 Page BA 7 of BA 115. Sampling and Characterization of Bioaerosols, c Size selective bioaerosol sampling in industrial hygiene. Size selective bioaerosol sampling may be done for several reasons Since the settling. velocity of aerosol particles is determined by the aerodynamic diameter knowing the size. distribution of an aerosol helps in predicting how long the particles are likely to remain. airborne and how far they can travel In health care settings for example various medical. procedures can produce a spray of droplets containing infectious microorganisms Large. droplets tend to fall onto surfaces fairly close to the source while smaller droplets can. remain airborne and carry pathogens many feet away from a patient Davies et al 2009. Jones and Brosseau 2015 Another application of size selection is to isolate different types. of bioaerosol particles such as separating fungal fragments from intact fungal spores. of Analytical Methods NMAM 5th Edition Sampling and characterization of bioaerosols by William G Lindsley Brett J Green Francoise M Blachere Stephen B Martin Brandon F Law Paul A Jensen and Millie P Schafer NIOSH BA 2 BA 5 BA 10 BA 28 BA 36 BA 39 BA 42 BA 46 BA 49 BA 62 BA 65 BA 65 BA 66 BA 101 1 Introduction 2 Principles of bioaerosol collection 3 Devices

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