Bioaerosol
Encyclopedia
A bioaerosol is a suspension of airborne particles that contain living organisms or were released from living organisms. These particles are very small and range in size from less than one micrometer (0.00004") to one hundred micrometers (0.004"). Bioaerosols react to air currents and move quickly or slowly depending on the environment. Bioaerosols are impacted by gravity but due to their size air density and air currents play a large role in their movement. The intact cellular component has been given the name, primary biological aerosol (PBA), which consists of virus particles, bacteria, fungal spores and plant pollen. PBA can range in size from 10 nanometers (small virus particles) to 100 micrometers (pollen grains). The atmospheric lifetime of PBA particles can range from a near indefinite time frame for some of the smallest virus particles to a few hours for the larger pollen particles.
, mycotoxins and viruses. It is currently thought that the majority of these airborne microorganisms are not in a viable state while in the atmosphere. However, current research has shown that certain groups of bacteria are capable of performing basic metabolic activity within cloud water. Groups of the small organisms clump up and enhance survival while airborne. Due to evaporation of water, bacterial cells usually die when they become airborne but under high humidity
conditions bioaerosol levels are increased. Fungal cells such as spores, molds and yeast
can be active at low humidity levels and high or low temperatures.
Single-stage Impactors
To collect aerosols falling within a specific size range, impactors can be designed for a variety of size cuts, depositing material onto slides, agar plates, or tape. The Hirst spore trap samples at 10 LPM, has a wind vane to always sample in the direction of wind flow. Collected particles are impacted onto a vertical glass slide greased with petroleum. Variations such as the 7-day recording volumetric spore trap (Burkard Air Sampling CO.) have been designed for continuous sampling using a slowly rotating drum that deposits impacted material onto a coated plastic tape. The airborne bacteria sampler (ABS) can sample at rates up to 700 LPM, allowing for large samples to be collected in a short sampling time. Biological material is impacted and deposited onto an agar lined Petri dish, allowing cultures to develop.
Cascade Impactors
Similar to single-stage impactors in collection methods, cascade impactors have multiple size cuts, allowing size resolution of sampled bioaerosols. Separating biological material by aerodynamic diameter is useful due to size ranges being dominated by specific types of organisms (bacteria exist range from 1 um to 20 um, and pollen from 10 um to 100 um). The Andersen line of cascade impactors (Thermo Electron Corporation) are most widely used, available in two and size-stage versions.
Impingers
Instead of collecting onto a greased substrate or agar plate, impingers have been developed to impact bioaerosols into a liquid, such as deionized water or phosphate buffer solution (PBS). Collection efficiencies of impingers are shown by Ehrlich et al. (1966) to be generally higher than similar single stage impactor designs. Commercially available impingers include the AGI-30 (Ace Glass Inc.) and Biosampler (SKC, Inc).
, water, sewage
,
Stachybotrys
atra is a well known toxic mold which releases mycotoxins and has been blamed for numerous deaths, particularly several in Cleveland, Ohio. Bioaerosols can be a source of microbial pathogens, endotoxins, and other allergens.
Background
Air often contains tiny organisms such as fungi, bacteriaBacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
, mycotoxins and viruses. It is currently thought that the majority of these airborne microorganisms are not in a viable state while in the atmosphere. However, current research has shown that certain groups of bacteria are capable of performing basic metabolic activity within cloud water. Groups of the small organisms clump up and enhance survival while airborne. Due to evaporation of water, bacterial cells usually die when they become airborne but under high humidity
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
conditions bioaerosol levels are increased. Fungal cells such as spores, molds and yeast
Yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...
can be active at low humidity levels and high or low temperatures.
Collection
Many techniques are used to collect bioaerosols such as collection plates, electrostatic collectors and impactors, although some methods are experimental in nature. Another way to collect or detect bioaerosols is by using a mass spectrometer.Single-stage Impactors
To collect aerosols falling within a specific size range, impactors can be designed for a variety of size cuts, depositing material onto slides, agar plates, or tape. The Hirst spore trap samples at 10 LPM, has a wind vane to always sample in the direction of wind flow. Collected particles are impacted onto a vertical glass slide greased with petroleum. Variations such as the 7-day recording volumetric spore trap (Burkard Air Sampling CO.) have been designed for continuous sampling using a slowly rotating drum that deposits impacted material onto a coated plastic tape. The airborne bacteria sampler (ABS) can sample at rates up to 700 LPM, allowing for large samples to be collected in a short sampling time. Biological material is impacted and deposited onto an agar lined Petri dish, allowing cultures to develop.
Cascade Impactors
Similar to single-stage impactors in collection methods, cascade impactors have multiple size cuts, allowing size resolution of sampled bioaerosols. Separating biological material by aerodynamic diameter is useful due to size ranges being dominated by specific types of organisms (bacteria exist range from 1 um to 20 um, and pollen from 10 um to 100 um). The Andersen line of cascade impactors (Thermo Electron Corporation) are most widely used, available in two and size-stage versions.
Impingers
Instead of collecting onto a greased substrate or agar plate, impingers have been developed to impact bioaerosols into a liquid, such as deionized water or phosphate buffer solution (PBS). Collection efficiencies of impingers are shown by Ehrlich et al. (1966) to be generally higher than similar single stage impactor designs. Commercially available impingers include the AGI-30 (Ace Glass Inc.) and Biosampler (SKC, Inc).
Methods of Analysis
Following bioaerosol collection, the total concentration and types of bioaerosol are analyzed in a number of different ways. Traditionally, bioaerosol has been analyzed by either performing plate counts or by performing direct counts using biological stains to discriminate between biological and non-biological particles. Plate counting is a very useful method to quantify the number of viable cells in the atmosphere. However, it has been well documented that plate counting methods usually miss approximately 99% of the total microbial diversity found in a given environment. With this in mind, more recent methods are being applied for the identification of bioaerosol. A couple of these methods include mass spectrometry as well as DNA based methods. This shift in methodology will allow for more quantitative studies, which will eventually lead to a more thorough understanding of the biological component of atmospheric aerosol.Sources
Common sources include soilSoil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
, water, sewage
Sewage
Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as wastewater, it is more than 99% water and is characterized by volume or rate of flow, physical condition, chemical constituents and the bacteriological organisms that it contains...
,
Stachybotrys
Stachybotrys
Stachybotrys is a genus of molds, or asexually-reproducing, filamentous fungi. Closely related to the genus Memnoniella, most Stachybotrys species inhabit materials rich in cellulose. The genus has a widespread distribution, and contains about 50 species.The most infamous species, S. chartarum and S...
atra is a well known toxic mold which releases mycotoxins and has been blamed for numerous deaths, particularly several in Cleveland, Ohio. Bioaerosols can be a source of microbial pathogens, endotoxins, and other allergens.
See also
- Mycotoxins
- Indoor air qualityIndoor air qualityIndoor air quality is a term referring to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants....
- Indoor bioaerosolIndoor bioaerosolBioaerosols are natural or artificial particles of biological origin suspended in the air. These particles are also referred to as organic dust. Bioaerosols may consist of bacteria, fungi , viruses, microbial toxins, pollen, plant fibers, etc...
- Mold growth, assessment, and remediationMold growth, assessment, and remediationMold assessment and mold remediation are techniques used in occupational health: mold assessment is the process of identifying the location and extent of the mold hazard in a structure, and mold remediation is the process of removal and/or cleanup of mold from an indoor environment.-Health...
- Mold health issues
- Sick Building SyndromeSick building syndromeSick building syndrome is a combination of ailments associated with an individual's place of work or residence. A 1984 World Health Organization report into the syndrome suggested up to 30% of new and remodeled buildings worldwide may be linked to symptoms of SBS...