Environmental Engineering Reference
In-Depth Information
, shed from human skin and
mucous membranes of the upper respiratory system, comprise 85 to 90% of
culturable/viable bacteria collected during air sampling in indoor spaces.
The reported viability of airborne bacteria is very low (<1%), so total airborne
concentrations may be two orders of magnitude higher than culturable/via-
ble concentrations.
Since bacteria require liquid water to grow and multiply, sources of
indoor airborne bacteria are relatively limited. Major sources include
humans and materials/equipment in which liquid water is present. This
includes, in the latter case, air-conditioning system cooling coil condensate
pans, central and free-standing cool-mist humidifiers, hot water heaters
(thermophilic bacteria), and outdoor sources such as cooling towers and
evaporative condensers. Cooling towers, evaporative condensers, and hot
water heaters are known sources of
Staphylococcus, Streptococcus,
and
Micrococcus
, the cause of
Legionnaires' disease infections. In residences, it is likely that moist/wet soil
under crawlspaces may be a source of actinomycete species and the odor of
geosmin in indoor spaces.
Legionella pneumophilia
4.
Health concerns
The contamination of indoor air by viable bacterial cells or substances pro-
duced by bacteria poses a variety of health concerns. These include the spread
of infectious disease by bacterial aerosols, outbreaks of hypersensitivity
pneumonitis associated with thermophilic actinomycetes, illness symptoms
and humidifier fever associated with bacterial endotoxins, infections in sur-
gical patients, and potential health effects associated with MVOCs.
A number of major diseases are spread by means
of bacterial aerosols. Selected diseases and their causal organisms are sum-
naires' disease (in both the greater public health and IE contexts). Tubercu-
losis and Legionnaires' disease are discussed in detail below.
Of note are spinal meningitis outbreaks in high-population-density
buildings, such as army barracks, and the specter of exposure to anthrax
a.
Infectious disease.
Table 5.1
Major Infectious Diseases Associated with
Bacterial Aerosols
Disease
Causal organism
Tuberculosis
Mycobacterium tuberculosis
Pneumonia
Mycoplasma pneumoniae
Diphtheria
Corynebacterium diphtheriae
Anthrax
Bacillus anthracis
Legionnaires' disease
Legionella pneumophila
Meningococcal meningitis
Neisseria meningitides
Respiratory infections
Pseudomonas aeruginosa
Wound infections
Staphylococcus aureus
