Appendix E - Bioaerosols
What is a bioaerosol?
Bioaerosols are airborne particles, solid or liquid. They can be large
molecules or volatile compounds. They contain living organisms. They will
vary in size from a fraction of a micron to around 100 microns. As with inert
“dust” particles, all bioaerosols are governed by the laws of gravity and will
be affected by air movements being transported by turbulence and diffusion.
Air will often contain micro-
organisms such as viruses,
bacteria, and fungi. None of
these actually live in the air, the
atmosphere tends to kill off
most of them. However, they
are frequently transported
attached to other particles,
such as skin flakes, soil, dust,
or dried residues from water
droplets. Aggregation of cells
into clumps can enhance the
survival whilst airborne.
Bacterial cells when they become airborne normally rapidly die, within a few
seconds, due to the evaporation of water associated with the particle. Thus
with higher humidity, higher bioaerosol levels can prevail. Airborne fungal
cells (yeasts, moulds, spores) can remain viable for much longer periods,
even at low relative humidity and high or low temperature extremes. These
can pose health risks for humans and animals.
Sources of Bioaerosols
Outdoor areas:
Wind action on soil, agitation of open water and raindrop
impaction are major sources of bioaerosols. Farming of land, wastewater
and sewage treatment are also significant outdoor sources. Other farming
activities, cattle, swine animal houses will generate bioaerosols. Food
processing plants, particularly of dairy products can generate higher levels of
bioaerosols. With today’s emphasis on renewables, power station biomass
storage and industrial scale composting facilities are sources of bioaerosols.
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