Environmental Engineering Reference
In-Depth Information
A consensus has recently developed that endotoxins produced by Gram-
negative bacteria such as
Pseudomonas
spp
., Flavobacterium
spp
., Klebsiella
spp
species cause humid-
ifier fever, a respiratory disease reported in European office buildings using
cool-mist humidification systems. Unlike hypersensitivity pneumonitis,
chronic exposures to endotoxin do not appear to cause chronic lung damage,
although some animal and epidemiological studies suggest that very high-
level exposures can cause lung changes similar to emphysema.
Endotoxin exposures have been reported to be the causative agent in
what has been described as toxic pneumonitis, inhalation fever, and organic
dust syndrome (associated with dusty work). Symptoms, which include
fever, chills, myalgia, and other influenza-like symptoms, are short-lived
(disappear in a few days). The number of cases as a function of populations
exposed may be close to 100%. A guideline value of 200 EU/m
.,
and
Enterobacter aerogenes
and other
Enterobacter
for endotoxin
3
exposure has been recommended.
Endotoxin exposures appear to be the cause of reactive airway disease
syndrome (RADS), a form of nonallergenic asthma. Reported symptoms
include respiratory airway irritation; stuffy, swollen nose; dry cough; increased
airway responsiveness; and, in advanced cases, pulmonary impairment. Reac-
tive airway disease syndrome is often accompanied by symptoms of headache,
fatigue, and joint pain. A guideline value of 10 EU/m
has been proposed to
reduce the incidence of RADS symptoms among those potentially exposed.
Endotoxin exposure has been reported to potentiate allergic and asth-
matic symptoms associated with exposure to dust mite allergens in dust
mite-sensitive individuals. Dust endotoxin levels >1.1 EU/m
3
have been
associated with severe shortness of breath, increased medication use, and
pulmonary function changes.
Endotoxin may also contribute to sick building symptoms. Studies con-
ducted in the Netherlands report significantly higher prevalence rates of
mucous membrane symptoms among occupants of buildings with dust
endotoxin levels >100 EU/m
3
. Consistent with these are studies of Danish
municipal buildings wherein symptoms of fatigue, headache, heavy head-
edness, hoarseness, and sore throat were closely associated with airborne
concentrations of both Gram-negative bacteria and endotoxin.
3
B.
Viruses
Viruses, the smallest living things, are best known for their ability to cause
human disease. They consist of single or double strands of DNA or RNA
covered by a protein coat. Since viruses have no cytoplasm, they must infect
host cells in order to replicate. As such, they are obligate parasites.
Viruses vary in size from about 20 nm, with a few genes, to 200 to 300 nm,
with hundreds of genes. They may appear as highly complex structures with
unique geometries or crystalline-like character.
A number of viral diseases are transmitted in aerosols derived from
infected individuals. Selected viral diseases and associated causal viruses
