Environmental Engineering Reference
In-Depth Information
chapter six
Biological contaminants —
mold
Biological contaminants were described in Chapter 5 in the context of illness
syndromes and disease risks associated with exposure to airborne organisms
and products of biological origin. Discussion of airborne bacteria and viruses
was in the context of their role in causing infectious disease and potentially
contributing to other problems; mites, insects and animal allergens, in the
context of causing chronic allergic rhinitis and asthma. Because mold is such
a significant indoor environment concern, this chapter is devoted to mold-
related health concerns and risk factors for mold infestation.
I. Biology of mold
The terms mold and mildew are commonly used to describe the visible
manifestations of the growth of a large number of organisms that are scien-
tifically classified as fungi. Terms such as
are used to
describe, respectively, single-celled fungi (widely used for baking and brew-
ing) and the large reproductive structures of a major class of fungi that are
used for food or are known for their high toxicity.
Fungi form true nuclei, which distinguishes them from lower organisms
such as bacteria. They differ from plants in that they do not produce chlo-
rophyll and thus cannot manufacture their own food; from animals in that
(except for reproductive cells in some species) they are not motile.
Structurally, fungi exist as masses of threadlike filaments or hyphae. The
collective mass of hyphal filaments is described as mycelium, the vegetative
part of the organism that infests a substrate and extracts food for the organ-
ism's growth. Though hyphal filaments are microscopic, the mycelium is
typically visible to the naked eye. Masses of mycelia can be distinguished
as fungal colonies (
Figure 6.1
)
. In many species, the hyphae are colorless; in
other species they contain pigments.
yeast
and
mushrooms
