Environmental Engineering Reference
In-Depth Information
Apart from its direct role in improving IAQ, biotechnology has also been used to
indicate poor indoor environmental conditions. As noted previously, the high
degree of environmental sealing of modern buildings has led to the proliferation of
conditions that favour poor IAQ. As well as increasing levels of some air pollutants,
the reduction in airflow and increase in humidity from poorly designed building
ventilation systems may lead to increased fungal growth, and a community shift in
the types of fungi present. Both increased fungal spore loads indoors, and a shift
from 'normal' fungal communities to ones strongly dominated by single species
such as Aspergillus and Stachybotrys spp. High concentrations of spores of these
species are known to lead to symptoms of 'sick building syndrome' (Cooley et al.
1998
; Cabral
2010
), thus indoor assessment of these organisms can act as an
indicator of poor IAQ in general. Fungi may also produce their own range of VOCs
(Douwes
2009
). There is a strong correlation between high indoor humidity, fungal
growth and human respiratory pathology (Cabral
2010
). Thus an assessment of the
fungal community composition in a building can be a useful indicator of whether
moisture accumulation is at a level where poor health outcomes may result. Fungal
sampling may be performed on precipitated dust or air samples, and the community
may be described by culture or molecular methods (Pitkäranta et al.
2008
).
8.10 Do Biological Air Filtration Methods Lead
to Microbial Biopollution?
As both botanical and exclusively microbial biofiltration systems, whether active or
passive, are primarily dependent on microorganisms for their function, as well as
presenting excellent conditions for general microbial growth, valid concerns arise
over whether the air cleaning benefits of these systems may be negated by the
emission of viable or non-viable bioparticles into the indoor environment (e.g. Lu
et al.
2012b
). Of the microorganisms likely to lead to any significant health prob-
lems, fungi are of primary concern (Torpy et al. 2013b). A primary cause of fungal
amplification indoors is relative humidity, with levels over 80 % leading to potential
problems (Adan and Samson
2011
). All current biological air filtration systems thus
provide possible point sources of the ideal conditions for fungal proliferation.
It has been proposed that indoor plants could indeed act as a significant source
of pathogenic fungal inocula (Staib et al.
1978
; Summerbell et al.
1989
; Hedayati
et al.
2004
; Engelhart et al.
2009
). These studies have generally been conjectural or
correlative, where the pathogenic fungal species implicated in a particular disease
case has been isolated from or associated with a potted plant, with no direct testing
of aetiology performed. A number of more recent studies, however, have more
directly investigated the potential for potted plants to support and release signif-
icant fungal material.
Darlington et al. (
2000
) assessed the effect of his biofiltration system on the
indoor airborne microbiota. The two-stage Anderson sampler was used to assess
both bacteria and viable fungi from the room in which his system was operating,
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