Bioaerosols - Aerosols: Measurement, Dosimetry, and Health Effects - page 304

The activated sludge systems in wastewater treatment plants can generate large amounts of bio-
aerosols. 126-128 Irrigation with reclaimed water and the soil application of solid waste materials from
water treatment processes also can aerosolize microorganisms and particles of organic matter. 128,129
The Florida red tides are an example of a growing environmental issue, that is, that of harmful algal
blooms that may adversely affect asthmatic persons exposed to organisms in onshore winds. 130 Of
related interest are studies of aerosolized brevitoxin from Karenia brevis , which can cause respi-
ratory distress, coughing, and eye irritation in humans. 131 The severity of pulmonary responses
to brevitoxin depends on the combined interaction of the total air toxin load, the speciic toxins
aerosolized, and the size of airborne toxin particles. 132 Airborne cyanobacteria (blue-green algae)
and other algae also deserve attention because of potential health risks for occupationally exposed
persons. 133,134
Ambient air is comprised of suspended solid and liquid particles with relatively stable size dis-
tributions, and particles of biological origin are part of this mixture. The fraction of the particle
number concentration of outdoor PM originating from living sources has been estimated to be
37% on a rooftop in Mainz, Germany, 135 and 4%-20% over the North Sea. 136-138 Carbon from fungi
accounted for up to 10% of the coarse (2.5-10 μm) fraction of organic carbon (OC) in samples
from the Austrian Alps. 139 Average concentrations of bacteria and fungi were 1.2 × 10 4 cells/m 3 and
7.3 × 10 2 spores/m 3 , corresponding to 0.03% and 0.9% of OC, respectively. Measurements in Vienna,
Austria, were higher, where fungal OC concentrations ranged from 22 to 677 ng/m 3 , 2%-14% of the
aerosol OC mass concentration, 1%-7% of the PM 10 concentration, and predominant contributors to
the coarse aerosol OC concentration (mean: 60%). 140
Air samples and budget calculations for actively wet-spore-discharging Ascomycota and
Basidiomycota suggested that they may account for a large proportion of coarse PM in tropical rain-
forest regions during the wet season (0.7-2.3 μg/m 3 ). 141 Using the average abundance of mannitol as
a tracer for basidiospores, these authors estimated their global average emission rate to be ∼17 Tg/
year. Global average atmospheric abundance and emission rate for total fungi were estimated to be
a factor of three higher, that is, ∼1 μg/m 3 and ∼50 Tg/year, respectively. This rate can be compared
to estimates of ∼47 Tg/year for anthropogenic primary organic aerosols and 12-70 Tg/year for sec-
ondary organic aerosols. Another model used mannitol as a fungal spore tracer and estimated that
they contribute 23% of total primary emissions of organic aerosol, or 7% of the ine-mode source. 142
These authors estimated annual, mean, simulated, surface concentrations of primary biological
aerosol particles (PBAP) over vegetated regions to be in the range of 0.1-0.7 μg m −3 (PM 2.5 ) and
0.4-3.0 μg m −3 (PM 10 ), with the highest concentrations in the tropics, where primary PBAP may be
the dominant source of organic aerosol. The source strength of biogenic material (from plants and
microorganisms) emitted as PM 2.5 has been estimated at 65 Tg/year. 143-145
Analyses at urban, rural, and high-alpine locations showed that the mass fraction of DNA in PM 2.5
was ∼0.05% (average concentration: ∼7 ng/m 3 ). 146 Bacterial sequences were from Proteobacteria
along with Actinobacteria and Firmicutes. Fungal sequences were characteristic of Ascomycota
and Basidiomycota, which actively discharge their spores. Plant sequences could be attributed to
green plants and moss spores, while animal DNA for only one unicellular eukaryote was detected
(a protist). Another study found that >99% of small-subunit rRNA sequences could be identiied as
belonging to bacteria, fungi, plants, or metazoa (multicellular animals). 147 Airborne bacteria were
diverse (367 unique taxonomic units). Bacteria assigned to the CFB (Cytophaga-Flavobacterium-
Bacteroides or Bacteroidestes group) and proteobacterial groups were the most abundant. Airborne
fungi were much less diverse, with ∼97% of sequences classiied as Ascomycota (>90% Hypocreales
order) and 3% as Basidiomycota (genera Paecilomyces , Fusarium , Acremonium , Trichoderma , and
Cordyceps ). Plants accounted for 13%-38% of rRNA sequences with 95% of them assigned to
the genus Pinus (pine trees) and 5% to the genera Poa , Abies , Alnus , and Equisetum (bluegrass,
ir, alder, and horsetail, respectively). Metazoan sequences were identiied as dipteran lies (genus
Ornithoica or Ceratitis ) or mites (genus Chortoglyphus ).