Environmental Engineering Reference
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after inhalation of the offending substance and usually last for several days. In the subacute form,
dyspnea and cough are manifested gradually over several weeks or months, and the condition can
progress to severe respiratory impairment. The chronic form of HP is often afebrile and associated
with dyspnea, malaise, weakness, weight loss, and cough. Pulmonary function abnormalities range
from diffusion defects with restrictive dysfunction to varying degrees of obstructive dysfunction.
Very severe disease can result in ibrosis and even death. 99
HP is a rare condition, generally only described in case reports, particularly in relation to expo-
sure to thermophilic microorganisms. The most well known is farmer's lung disease, which occurs
most often in farmers exposed to one or more of four thermophilic, mycelial bacteria growing in hay
or straw: Saccharopolyspora rectivirgula , Saccharomonospora viridis , Thermoactinomyces sac-
chari , or Thermoactinomyces vulgaris . Evidence from Finland and France suggests that fungi may
play a role in farmer's lung disease in these regions. 101,102 HP also has been described for grain work-
ers, mushroom growers, bird breeders, sawmill workers, and compost workers. Other examples
include buildings with heavily contaminated humidiiers, but this is very rare.
HP case reports were noticed in the early 1990s among machinists exposed to water-based metal-
working luids (MWFs) treated with biocides (Section 12.3.3). These outbreaks often were associ-
ated with species of non-tuberculous Mycobacterium. Mycobacterium immunogenum is believed to
be infectious and a cause of “hot tub lung” in immunocompromised persons. 103 “Hot tub lung” has
been described as an HP-like, granulomatous, lung disease. Characteristics of this condition suggest
an immunologic mechanism similar to HP, but other evidence suggests an infectious response. 103
Reports of HP-like symptoms in lifeguards and pool workers have suggested HP or an HP-like
condition, but it is unclear if these symptoms are the result of irritant effects from pool chemicals
(trichloramines), bacterial growth and aerosolization due to poor facility design and maintenance,
elevated endotoxin levels, or a combination of these or other factors. 104,105
12.2.2.5  Chronic Bronchitis
Chronic bronchitis is most often deined as a nonallergic condition characterized by cough with
phlegm most days for at least 3 months of the year for a consecutive period of at least 2 years.
Chronic bronchitis may present with or without airway obstruction and symptoms such as dyspnea,
chest tightness, and wheezing. The underlying mechanism is an increase in mucus-secreting glands
and alterations in the characteristics of the mucus itself. Smoking is one of the most important
causes of chronic bronchitis. However, bioaerosol exposure may play a role as well, as has been
demonstrated in several occupational environments such as farming, the cotton and compost indus-
try, and other occupations where workers are exposed to high dust levels. Whether nonoccupational
indoor exposures play a role is not clear. 86
12.2.2.6  Airlow Obstruction
Several studies have shown associations between chronic airlow obstruction—measured by spi-
rometry—and bioaerosol exposures in industrial and agricultural workers. Associations were par-
ticularly strong for endotoxin exposure. 106 A decline in forced expiratory volume in 1 s (FEV 1 ),
which is indicative of airway obstruction, also has been shown in occupants of damp and moldy
homes, 107 although indings have not been consistent. 78 Indoor (1 → 3)-β-d-glucan and endotoxin
levels as well as loor dampness also have been shown to be associated with greater variability in
peak expiratory low (PEF; reduced PEF is another marker of airway obstruction). Airlow obstruc-
tion is associated with both allergic and nonallergic disease.
12.2.2.7  Pulmonary Hemorrhage
Pulmonary hemorrhage is a condition characterized by elevated levels of hemosiderin, an iron-
containing pigment, in lung tissues. The condition can be fatal and is caused by diffuse bleeding or
hemorrhage in the alveoli. Idiopathic pulmonary hemorrhage (IPH) describes this condition when
the cause is unknown. A U.S. Centers for Disease Control and Prevention (CDC) report suggested
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