Bioaerosol

A bioaerosol (short for biological aerosol) 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.

Air often contains tiny organisms such as fungi, bacteria, 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.

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.

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.

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