Bioaerosols - Aerosols: Measurement, Dosimetry, and Health Effects - page 312

and in industrial food-processing facilities. 264 Exposure levels and bioaerosol composition can vary
widely in occupational environments. Very little is known about exposures to airborne mycotoxins
and respiratory health effects in occupational settings. Mycotoxins of Fusarium , Aspergillus , and
Penicillium species are known to be present in the inhalable fraction of airborne corn, cotton, and
grain dust. However, it is not clear whether these components contribute to respiratory symptoms in
these industries. Serum albumin adducts of alatoxin B 1 have been detected in animal feed workers
who had handled alatoxin B 1 -containing raw material. 265 These indings may explain the elevated
risk of liver and biliary cancer observed in a study of animal feed workers in Denmark. 266 Also,
warnings of climatic conditions favorable for fungal crop infections have been found to correlate
with hormone dependent cancers (as well as reproductive effects) in Norwegian farmers, and similar
associations have been found for lip cancer. 267,268 Other studies have shown that fungal warnings
were correlated with the trichothecene mycotoxin concentration in ine grain dust and with DNA of
toxigenic Fusarium species in personal air samples. 269,270
Potent IgE-binding allergens are found in biotechnology facilities that produce enzymes
derived from fungi and bacteria for use in washing powders and both human and animal foods.
Populations at risk are workers in the enzyme-producing industries and in detergent-manufacture
and food-processing establishments where enzyme preparations are used or incorporated into con-
sumer products. Another well-known IgE-binding allergen is plant pollen, which may cause aller-
gies in green house workers. Latex allergens have received extensive attention during the last decade
with high numbers of healthcare and hospital workers becoming sensitized to latex gloves produced
from the sap of the rubber tree Hevea brasiliensis .
Several animal proteins (e.g., dust mite, cat, mouse, and rat allergens) also are known to have
strong allergenic properties (Section 12.3.2). In particular, it is well established that laboratory ani-
mal workers are at risk of developing occupational IgE-mediated allergy to mouse and rat allergens.
In addition to IgE-binding allergens, workers may be exposed to IgG-binding allergens. These fun-
gal and actinomycetes allergens are assumed to be involved in the pathogenesis of HP or farmer's
lung (Section 12.2.2.4). Airborne animal proteins from crustacean processing and exposure to aero-
solized ish proteins can result in “crab asthma” and other allergic asthma in the commercial ishing
and processing industries. 271
12.4 BIOAEROSOL SIZE DISTRIBUTIONS
Bioaerosols vary greatly in diameter from nanometer-sized viruses and cell fragments to single
cells, cell agglomerates, and aeroallergen particles in the micrometer range. Viruses are generally
20-300 nm in physical diameter, intact bacteria 0.3-10 μm, fungal spores 1-100 μm, and pollen
grains 5-200 μm (Table 12.1). However, information is incomplete on the aerodynamic size of air-
borne viruses, bacteria, pollen, fungi, and allergens, and very little information is available on the
size distributions of cell fragments (Section 12.4.1.3). The concentration and distribution of bioaero-
sols vary considerably with atmospheric and indoor conditions and between and within sites. The
dynamic properties of all airborne particles depend on their physical characteristics such as physi-
cal size, shape, surface features, density, hygroscopicity, and electrostatic charge (Section 12.5).
Electrostatic charges on particles may enhance their deposition on oppositely charged surfaces or
through image charging (induction of an opposite charge on a surface by a charged particle). The
amount of charge that particles carry depends on the aerosol generation mechanism, environmental
conditions, and the time that has elapsed between aerosolization and measurement. For example,
a net negative charge has been observed on laboratory-generated bacterial aerosols. 272,273 However,
few studies have measured naturally occurring charges on biological particles.
Most airborne particles have a thin layer of water molecules on their surface and can absorb or
lose water. Substantial changes in the particle size of hygroscopic cells can alter their deposition
behavior. Hygroscopic particle growth that is rapid enough to occur during passage through the
respiratory tract will increase deposition in the regions where settling and impaction are important