Molds need moisture to grow so that keeping materials and buildings dry is
the best method of control. Filtration of incoming air and a regular
program of maintenance and cleaning of ventilation ducts can reduce the levels
of molds that may enter and multiply in indoor environments. Damp areas in the
home such as basements and attic areas where water seepage or condensation may
occur are prime growing areas for molds. Molds will reproduce quickly if the
temperature and humidity conditions are right. Water damaged buildings tend to
develop long term mold problems unless all structural materials and insulation
are dried or replaced.
Nelson stated: "Our region experienced one of the
greatest natural disasters of modern times when the Red River flooded in 1997.
In Grand Forks, ND, alone, there were 9,000 flooded homes. I have been impressed
with the common occurrence and extensive growth of Stachybotrys in buildings
damaged by flood waters and the lack of knowledge by the general public and
public and private institutions about this fungus."
Kodama and McGee found sixteen types of indoor airborne fungi. The main
species belong to the families: Aspergillus, Penicillium, Cladosporium, Mucor,
Stachybotrys, Absidia, Alternaria, Fusarium and Cryptostroma. The greatest
health risks are Candida, Aspergillus, Histoplasma and Penicillium.
An ambitious US study assessed air from 1,717 buildings; the most common
airborne fungi, both indoors and outdoors and in all seasons and regions, were
Cladosporium, Penicillium, nonsporulating fungi, and Aspergillus. Stachybotrys
chartarum was identified in the indoor air in 6% of the buildings studied and in
the outdoor air around 1% of the buildings studied. Water distribution systems
can host molds that are spread through aerosolization of fungal spores from
shower heads and other faucets.
Park et al demonstrated that mold levels in dust were associated with
new-onset asthma in in a damp office building. They used measures of
hydrophilic fungi and ergosterol to assess fungal biomass. Asthma,
hypersensitivity pneumonitis (HP), and sarcoidosis had been diagnosed in
employees who worked in the building.
Yeasts in floor and chair dust samples increased the odds of respiratory
illnesses. Rhodotorula genus of yeasts were prevalent and have been implicated
in IgE-mediated allergy and HP. In bakeries, breweries, and distilleries, the
yeast Saccharomyces cerevisiae is a major allergen. Other hydrophilic fungi
identified were Phoma herbarum, Chaetomium globosum, Mucor plumbeus, Rhizopus
stolonifer, and Stachybotrys chartarum.
They noted the limitations of fungal culture. Culture media only grow a
small proportion of the viable spores and do not detect nonviable spores and
fungal fragments. In contrast ergosterol found in fungal membranes is a good
measure of fungal biomass that measures viable and nonviable spores and fungal
While mold density can be measured and some mold species are identified by
culture and microscopy, the significance of this data is seldom obvious. There
are too many fungi in every sample to understand what is really going on.
Fungal spore concentrations vary a great deal with the time of day, seasons and
weather. Spore release is sporadic. Lee et al compared the performance of four
bioaerosol samplers, the Reuter Centrifugal Air Sampler, the Andersen N6 single
stage, the Surface Air System 90, and the Air-o-Cell, in measurements for
airborne fungi in 75 public buildings. The samplers had differences in detection
limits, reproducibility, and overall yield. Fungal concentrations correlated,
but varied by orders of magnitude.
Air samples are cultured for mold growth; the density of mold spores is
described as the number of colony forming units (CFU) per cubic meter of air.
Values between 400 and 1000 in homes are common. In agricultural and industrial
locations, mold density can be in the millions of CFU per cubic meter of air.
For example, the concentration of airborne fungi was monitored for 6 months in a
special-care unit of a hospital; 98 fungal species were identified; 48
species were potential pathogens. The average fungal density ranged from 124 to
485 CFU per cubic meter. In another hospital survey, Aspergillus fumigatus
represented 77.0% of total fungal strains. Concentrations of airborne fungi
showed greater variation than bacteria and ranged from 9.9-96.1 CFU per cubic
meter. The concentrations of airborne microorganisms were greater in the morning
compared with the afternoon.
Measurements of two fungal cell components, glucan and ergosterol, can be
used to assess the “fungal load.” Foto et al reported that most airborne
glucan found in damp houses was fungal in origin, coming from yeasts,
intact spores, as well as hyphal and spore fragments. Correlations between
airborne glucan were strong for ergosterol and visible mold. Rabine et al used
liquid phase chromatography to measure ergosterol, a component of the cell
membrane of microscopic fungi. They suggested that air sampling with a rotating
cup collection apparatus and ergosterol measurement could be used to assess
exposure to airborne fungal flora.
The two most prevalent fungal infections in hospitals are caused by Candida
and Aspergillus species. These organisms can occur naturally in the exterior
environment and enter as spores or active fungi attached to dust particles.
Toxic black mold
Stachybotyrs or “toxic black mold" is found everywhere. Half of all blood
donors have antibodies to it.Evidence implicates this fungus as a problem in
homes and one of the causes of the "sick building syndrome." Stachybotyrs
produces macrocyclic trichothecenes, toxic compounds with a potent ability to
inhibit protein synthesis and phenylspirodrimanes, immunosuppressive agents.
Jarvis et al suggested that these immunosuppressive agents may be responsible
for the observed high toxicity of this fungus.
Hodgson et al reported that occupants of a mold contaminated courthouse
office building developed fatigue, headaches, chest tightness, mucous membrane
irritation and lung disease. Stachybotyrs , Aspergillus and Penicillium species
grew on interior walls; mycotoxins were identified in moldy ceiling tiles and
vinyl wall coverings. Farm exposure to stachybotryotoxicosis has been reported
for several decades in humans and animals. Damp hay, straw and feed grain
supports fungal growth. Common symptoms in humans were skin rashes pain and
inflammation in the eyes, nose mouth and throat, chest pain, cough, fever,
headache, and fatigue.
comparison of four samplers for enumerating fungal aerosols I. Sampling
characteristics. Indoor Air. 2004; 14(5):360-6(ISSN: 0905-6947)
FotoM; VrijmoedLL; MillerJD; RuestK; LawtonM; DalesREA comparison of
airborne ergosterol, glucan and Air-O-Cell data in relation to physical
assessments of mold damage and some other parameters. Indoor Air. 2005;
Jarvis, B., Sorenson, W. G., Hintikka, E., Nikulin, M., Zhou, Y., jiang, J.,
Wang, S., Hinkley, S., Etzel, R., and Dearborn, D. 1998. Study of toxin
production by isolates of Stachybotrys chartarum and Memnoniella echinata
isolated during a study of pulmonary hemosiderosis in infants. Appl. Environ.
Hodgson, M. J., Morey, P., Leung, W., Morrow, L., Miller, D., Jarvis, B. B.,
Robbins, H., Halsey, J. F., and Storey, E. 1998. Building-associated pulomonary
disease from exposure to Stachybotrys chartarum and Aspergillus versicolor. J
Occup. Environ. Med. 40:241-249.
Nelson BD. Stachybotrys chartarum: The Toxic Indoor Mold. See his
excellent review article online at American Phytopathologcial Society website.
Accessed May 2007.Nelson is A Professor of Plant Pathology, North Dakota State
Ju-Hyeong Park; Jean M. Cox-Ganser; Kathleen Kreiss; Sandra
K. White; Carol Y. Rao.Hydrophilic Fungi and Ergosterol Associated with
Respiratory Illness in a Water-Damaged Building. Environ Health Perspect.
2008;116(1):45-50. ©2008 National Institute of Environmental Health
Sciences. Accessed online 02/12/2008.