Environmental Engineering Reference
In-Depth Information
12.3.3  b ioaerosols in  o ccuPational  e nvironMents
Occupations in the public and private service sectors can place workers in close proximity to cli-
ents in shared spaces, resulting in a greater risk for communicable disease transmission. 236 This
is especially true for diseases with annual outbreaks, such as inluenza, acute viral gastroenteri-
tis, and colds. As a consequence of treating patients with these diseases, health care workers are
at increased risk of exposure to viral and bacterial bioaerosols. Zoonotic diseases with airborne
transmission such as Q-fever, psittacosis, histoplasmosis, and multidrug-resistant Staphylococcus
aureus (MRSA) may affect farmers, animal handlers, pet store clerks, veterinarians, zookeepers,
and abattoir workers. 236 The inluenza virus can be transmitted to humans from birds or swine or
from avian species via swine. Some infectious diseases are associated with episodic exposures aris-
ing from engineering errors, maintenance failures, or unusual exposures. For example, outbreaks
and individual cases of pneumonia caused by Legionella pneumophila have occurred in connection
with contaminated cooling towers and evaporative condensers, untreated whirlpool spas, dental
ofice apparatus, and produce misters in grocery stores, but often the source is not identiied. 237,238
Anthrax, although of current concern as a biological weapon, may be one of the irst infec-
tious, respiratory diseases to be associated with certain occupations. Inhalation anthrax has been
associated with exposure to B. anthracis spores in contaminated animal products, such as during
the industrial processing of wool (woolsorters' disease). 239 The intentional distribution of spores
through mail established a new and unusual route of occupational exposure from contaminated
letter-sorting machines. 240 In October 2001, four cases of inhalation anthrax occurred in employ-
ees at a Washington, DC, postal processing and distribution center. These cases were part of a
multistate outbreak of inhalation and cutaneous anthrax associated with intentional distribution of
envelopes containing B. anthracis spores to media and federal government ofices. Together, these
represent the irst reported cases of inhalation anthrax in postal workers and the irst outbreak of
inhalation anthrax caused by occupational exposure in the United States since 1957.
Opening letters containing a B. anthracis simulant has been observed to spread the spores
throughout a building in <4.5 min, and potential mitigation techniques, such as closing the ofice
door or shutting off the ventilation system, were not effective. 241 One concern is possible “weap-
onization” of infectious particles through the addition of surface-active materials that would cause
them to separate from each other and to maintain a uniform and inhalable particle size. Threats of
bioterrorism and biowarfare have heightened the need for accurate and sensitive methods for the
measurement of airborne infectious agents and have encouraged the development of rapid detection
methods (Section 12.6.3.4).
Microbial contamination is a persistent problem in a variety of manufacturing processes. 242-248
One setting that has been investigated extensively is the metalworking industry, for example, facili-
ties that manufacture automobile components, where rapidly moving parts can generate droplets of
contaminated cutting luid. Water-based MWFs provide an excellent medium for the growth of a
variety of bacteria and fungi to concentrations >10 6 /mL despite the expanded use of biocides and the
implementation of other control measures. 248-252 Mycobacterium species and other Gram-positive
bacteria may be pervasive MWF contaminants and cause HP in exposed workers. 248,253,254 Using an
established animal model for HP, M. immunogenum in MWFs has been shown to induce HP, and
co-exposure with endotoxin can augment the severity of this response (Section 12.2.2). 255
Exposure to organic dusts that contain microbes or microbial cell fragments is of concern in
industrial and agricultural environments. 47,256,257 Gram-negative bacteria and associated endotoxin
are among the primary biological contaminants of concern, with inhalation of endotoxin result-
ing in both reversible (asthmatic) and chronic airway obstruction, respiratory symptoms (symp-
toms of asthma, bronchitis, and byssinosis), and increased airway responsiveness. 258 Consensus
recommendations have been published for the measurement of endotoxin concentration, 259-261 and
health-based occupational exposure limits have been proposed. 262,263 Workers are also exposed to
airborne bacteria and endotoxins as well as fungi in large animal coninement buildings and sheds
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