Environmental Engineering Reference
In-Depth Information
12.2   HEALTH EFFECTS OF BIOAEROSOLS IN INDOOR 
AND OUTDOOR ENVIRONMENTS
Microorganisms and other bioaerosols are ubiquitous in the ambient environment and their concen-
trations may be elevated in damp and poorly ventilated buildings as well as in industrial settings
where microbial, plant, or animal products are handled. Respiratory diseases and symptoms are
the most common health effects associated with infectious aerosols (Section 12.2.1). Noninfectious
bioaerosols may cause asthma, hay fever (rhinitis), organic dust toxic syndrome (ODTS), hypersen-
sitivity pneumonitis (HP), chronic bronchitis, and airlow obstruction (Section 12.2.2). Bioaerosol
exposure also may contribute to building-related symptoms (BRS, sick building syndrome, SBS),
and cancer (Section 12.2.3.2).
Interest in bioaerosol exposures has grown, in particular due to a global increase in allergies and
asthma as well as concerns about damp indoor environments. In addition to changes in building
design and operation to increase energy eficiency, several new industrial activities have emerged
that elevate bioaerosol exposures. Examples include waste recycling, waste sorting, and organic
waste collection and composting as well as the production of puriied biological substances such
as microbial enzymes for food processing (e.g., α-amylase in commercial bakeries) and detergents.
Many of these enzymes are potent allergens that can cause asthma and rhinitis. Furthermore, the
widespread nontherapeutic use of antibiotics as growth promotants in livestock has accelerated the
development of antibiotic resistant pathogens that may increase the risk of severe infectious diseases
in workers who handle and process these animals. 2
There is also heightened awareness of the potential use of bioaerosols for bioterrorism, in par-
ticular viruses, bacteria, rickettsia, and fungi. 3 For instance outside well-deined geographical areas
and some occupations, anthrax was a relatively unknown disease until 2001 when spores were
spread by mail causing ive deaths in the United States. Also, the global transmission of inluenza
is a re-emerging concern and many experts wonder not if, but when, the next serious pandemic will
occur. The inluenza pandemic of 1918-1919 that killed nearly 50 million people worldwide and the
2009 pandemic inluenza A (H1N1) outbreak underscore this concern.
Despite the recognition of the importance of bioaerosols, and with the exception of some infec-
tious diseases, the precise role of biological agents in the induction, aggravation, and progression
of symptoms and diseases is only poorly understood. Paradoxically, indoor exposure to moderate
bioaerosol concentrations has been suggested to reduce the risk of developing hypersensitivity and
allergic asthma in early life (Section 12.2.4). This protective effect is consistent with the “hygiene
hypothesis,” which postulates that growing up in a less microbiologically hygienic environment
may decrease the risk of developing respiratory allergies (Section 12.2.4). 4-12 However, the evidence
for a protective effect from microbial exposure has not been consistent (Section 12.2.4). 13-19 In the
next sections we present an overview of the health effects associated with bioaerosol exposures.
12.2.1  i nFectious  d iseases
Most of the agents responsible for respiratory infections are spread through the air, primarily from
person to person (anthroponoses) but also from living animals (zoonoses) and the abiotic environ-
ment (e.g., soil and water) or decaying plant or animal matter (sapronoses). 20 Viruses are responsible
for most childhood respiratory tract infections, although bacteria (e.g., Mycoplasma and Chlamydia
species) also infect children at particular ages (Table 12.1). A World Health Organization (WHO)
study estimated that lower respiratory tract infections accounted for over 6% of the total, world-
wide burden of disease and that tuberculosis alone represented 2% of the burden. 21 Tuberculosis
exceeds all other chronic infections in incidence and prevalence, and Mycobacterium tuberculosis
ranks seventh among all causes of death. 22 Globally, tuberculosis incidence peaked in 2004, with
the most cases in Asia (55%) and Africa (30%) and small proportions in the Eastern Mediterranean
Region (7%), the European Region (5%), and the Region of the Americas (3%). 22
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