Dampness and Mould - WHO guidelines for indoor air quality - PRWeb

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WHO GUIDELINES FOR INDOOR AIR QUALITY: DAMPNESS AND MOULD
cubic metre of air. In a given space, concentrations of fungi are highly variable
and depend on such factors as: climate and season, type of fungus, construction,
age and use of the building, and ventilation rate. They also depend largely on the
sampling and analytical methods used, making valid comparisons between studies
difficult.
Indoor fungal fragments are not commonly measured in field studies, but a
study with an aerosolization chamber showed that submicron fungal fragments
from culture plates and mould-contaminated ceiling tiles aerosolized simultaneously
with spores but at substantially higher concentrations (320–514 times
higher) (Gorny et al., 2002; Cho et al., 2005). This suggests that indoor exposure
to fungal fragments is at least as important as exposure to fungal spores.
2.3.2 Bacteria
As mentioned above, few studies have addressed bacteria in damp indoor environments.
Some identified Streptomycetes on damp or wet indoor surfaces
(Hyvärinen et al., 2002; Rintala, Nevalainen, Suutari, 2002; Rintala et al., 2004).
Streptomycetes are Gram-positive, spore-forming actinobacteria, which are typical
soil organisms that produce a wide range of metabolites, including some toxins,
such as valinomycin (Andersson et al., 1998). The metabolites produced are
substrate-dependent (Hirvonen et al., 2001; Roponen et al., 2001; Murtoniemi et
al., 2001a, 2003). Mycobacteria have also been shown to be common in moisture
damaged buildings, their presence increasing with the degree of fungal damage
(Torvinen et al., 2006). Cell wall components of mycobacteria are known to be
highly immunogenic, and exposure to mycobacteria may cause inflammatory responses
(Huttunen et al., 2000, 2001).
The concentrations of total viable bacteria in indoor environments may range
between 10 1 and 10 3 CFU/m 3 (Gorny, Dutkiewicz, Krysinska-Traczyk, 1999),
probably representing the degree of occupancy of the building and the efficiency
of its ventilation. The literature does not provide typical airborne concentrations
in damp indoor environments as compared with non-damp environments. Also,
although the presence of Streptomycetes and mycobacteria may be an indication
of bacterial growth, normal levels have not been established.
2.3.3 Endotoxins
Endotoxins are integral components of the outer membrane of Gram-negative
bacteria and are composed of proteins, lipids and lipopolysaccharides. The term
endotoxin refers to a toxin on the bacterial cell wall, which is often liberated as a
result of cell lysis. In the environment, airborne endotoxins are usually associated
with dust particles or aqueous aerosols. They have a broad size distribution,
but the levels may be higher in the coarse fraction (Schwarze et al., 2007). Heavy
exposure to endotoxins can cause respiratory symptoms, including non-allergic
asthma, but moderate-to-low exposure may protect against allergies and asthma