Bioaereosol

A bioaerosol (short for biological aerosol) is a suspension of airborne particles that contain living organisms or were released from living organisms.[1] 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.

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

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