The Toxic Indoor Mold

[Guest guest]

200 hundred yrs.later The clock is still ticking!!Still no answers...

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Stachybotrys chartarum:

The Toxic Indoor Mold

Berlin D. , Professor, Department of Plant Pathology,

North Dakota State University, Fargo

(Berlin.@...)

Introduction

Stachybotrys chartarum is a fungus that has become

notorious as a mycotoxin producer that can cause animal and

human mycotoxicosis. Indeed, over the past 15 years in

North America, evidence has accumulated implicating this

fungus as a serious problem in homes and buildings and one

of the causes of the " sick building syndrome. " In 1993-

1994, there was an unusual outbreak of pulmonary hemorrhage

in infants in Cleveland, Ohio, where researchers found S.

chartarum growing in the homes of the sick infants. This

incident increased the awareness of home/building molds and

brought this fungus to the immediate attention of the

medical community. In recent years there has been a cascade

of reports about toxic molds in the national media. The New

York Times Magazine, August 12, 2001, ran a front page

story on toxic mold. Newspaper articles (Fig. 1) such

as " Fungus in 'Sick' Building " (New York Times, May 5,

1996) or " Mold in schools forces removal of Forks kids "

(Fargo Forum, June 1997) are eye-catching news items. The

nationally syndicated comic strip Rex ran a series

on Stachybotrys, and television news shows have run entire

programs on Stachybotrys contamination of homes. The fungus

has resulted in multimillion dollar litigations and caused

serious problems for homeowners and building managers who

must deal with the human issues and remediation.

As a mycologist, I have been advising public officials and

the general public on the issues concerning indoor molds.

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. There was an enormous need for information on the

effects of the flood on human health in the Red River

Valley. Because of the increasing awareness of molds in

indoor air quality, a coordinated effort by city, state and

federal officials to provide information on mold prevention

was undertaken. In my observations following the flood and

in subsequent years of dealing with indoor mold issues, I

have been impressed with the common occurrence and

extensive growth of S. chartarum in homes and buildings

damaged by flood waters or other types of water incursions

and the lack of knowledge by the general public and public

and private institutions about this fungus. This review

provides information on the fungus, its biologically active

compounds, the history of the problem, the controversy

about this fungus, and briefly comments on detection and

remediation.

The Fungus

Stachybotrys chartarum (Ehrenb. ex Link) (synonyms=

S. atra, S. alternans) was first described as S. atra by

Corda in 1837 (5) from wallpaper collected in a home in

Prague. It is a member of the Deuteromycetes, order

Moniliales, family Dematiaceae, and is common on plant

debris and in soil. The taxonomic treatment of the genus by

Jong and (38) is a good reference on identification

while Hintikka (27) provides general information on

biology. The fungus grows well on common mycological media

such as potato dextrose, V-8 or cornmeal agar, and

sporulates profusely forming dark masses of conidia (Fig.

2). The fungus is relatively easy to identify because of

the unique phialides of the genus and conidial morphology

of the species. Conidiophores are determinate,

macronematous, solitary or in groups, erect, irregularly

branched or simple, septate, dark olivaceous, and often

rough walled on the upper part. The phialides are large, 9-

14 µm in length, in whorls, ellipsoid, olivaceous, and

often with conspicuous collarettes. Conidia are

ellipsoidal, unicellular, 7 to 12 by 4 to 6 µm, dark brown

to black and often showing a ridged topography when mature.

The ridged nature is readily apparent with scanning

electron microscopy (Figs. 3 and 4), but can also be

observed with an oil immersion lens at 1000x. On lower

power the spores appear verrucose. Young spores and some

mature spores may be smooth. The phialides produce conidia

singly and successively into a slime droplet that covers

the phialides. Eventually the slime dries and the conidia

are covered with the slime residue and remain on the

conidiophore as a mass or ball of spores (Fig. 3). The

spores are therefore not readily disseminated in the air

compared to other fungi such as Aspergillus. However, when

the fungus and substrate dries and is disturbed by

mechanical means or air movement, conidia can become

bioaerosols. A genus similar to Stachybotrys, but with

spores in chains is Memnoniella (38); it also has species

that produces trichothecenes (35). Haugland et al. (21)

have proposed relegation of Memnoniella to synonymy with

Stachybotrys based on morphological characteristics and

comparative sequence analysis of the nuclear ribosomal RNA

operon.

S. chartarum growing on natural or man made substrates can

often be identified by a person familiar with its growth

pattern. However, there are some very dark dematiaceous

Hyphomycetes which look similar, therefore microscopic

examination of the fungus is needed to confirm

identification. When the fungus is actively growing, the

characteristic phialides and conidia are easy to observe,

but when dry, the phialides collapse, are more difficult to

observe, and emphasis must be placed on morphology of

conidia. Although the traditional method of identification

is based on morphology of the sporulating structures, PCR

primers specific for S. chartarum are reported and may now

be used in commercial microbiological laboratories to

identify this fungus (7,20,58). A PCR product analysis

using a fluorogenic probe has also been developed to

quantify conidia of S. chartarum and can be used in the

analysis of samples from mold contaminated indoor

environments (22,52,58).

The fungus is strongly cellulolytic and will grow under

conditions of low nitrogen. A simple way to grow the fungus

is to streak some conidia onto wet Whatman filter paper in

a petri dish and within a week spores are produced. If

spores are placed on a small ridge made in the paper, the

conidiophores will grow at an angle and allow a side view

of conidial formation with a stereoscope. This is a

convenient method to determine if spores are in chains to

distinguish Stachybotrys from Memnoniella. Also, the filter

paper method will allow isolation of S. chartarum away from

many other fast-growing, but non cellulolytic fungi that

would out-compete S. chartarum on rich media.

Mycotoxins and Other Biologically Active Metabolites

The mycotoxins and other biologically active compounds

produced by S. chartarum are of concern to human health

(23,32,33,57). Mycotoxin poisoning by this fungus is

referred to as stachybotryotoxicosis.

S. chartarum produces a variety of macrocylic

trichothecenes and related trichoverroids: roridin E and L-

2; satratoxins F, G, and H; isosatratoxins F, G, and H;

verrucarins B and J; and the trichoverroids, trichoverrols

A and B and trichoverrins A and B. The satratoxins are

generally produced in greater amounts than the other

trichothecenes, but all compounds are produced in low

quantities. They apparently occur in all parts of the

fungus (53). The difficulty in obtaining, identifying, and

purifying these toxins has slowed extensive studies on

their biological activity. Hinkley and Jarvis (23) recently

published analytical methods for the identification and

quantification of bioactive compounds produced by this

fungus. These methods were designed to quantitate

individual compounds in culture extracts and detect low

levels of trichothecenes in samples.

Macrocyclic trichothecenes are highly toxic compounds with

a potent ability to inhibit protein synthesis (32).

Numerous studies have demonstrated the toxicity of toxins

from S. chartarum on animals and animal and human cells

(42,45,49,51). Yang et al. (62) reported that satratoxin G

was the most cytotoxic of eight trichothecenes tested on

mammalian cells, even more toxic than the well known T-2

toxin associated with alimentary toxic aleukia. Other

researchers have also reported the high toxicity of

satratoxins compared to other trichothecenes (18). The LD50

in mice for satratoxins is ~1 mg/kg (32).

In addition, the fungus produces nine phenylspirodrimanes

(spirolactones and spirolactams) and cyclosporin, which are

potent immunosuppressive agents (33). Jarvis et al. (33)

suggested that the combination of trichothecenes and these

immunosuppressive agents may be responsible for the

observed high toxicity of this fungus. New biologically

active compounds are still being discovered in cultures of

S. chartarum. Hinkley et al. (24,25) recently described the

metabolites atranones A-G and two dolabellane diterpenes,

but the complete biological activity of these compounds is

unknown. Vesper and colleagues (57,59,60) reported some

isolates produce Stachylysin, a hemolysin (compounds that

lyse erythrocytes), and a hydroxamate siderophore. They

suggest these compounds could be pathogenicity factors

involved in pulmonary hemorrhage in infants exposed to S.

chartarum.

There is considerable variation among isolates of S.

chartarum in the production of mycotoxins and other

metabolites (2,24,27,34,40). Indeed, Hinkley et al. (25)

suggest there are two chemotypes of the fungus: the

atranone and the macrocyclic trichothecene producers.

History of the Problem

In the Ukraine and other parts of eastern Europe during the

1930s, there were outbreaks of a new disease in horses and

other animals that was characterized by symptoms such as

irritation of the mouth, throat, and nose; shock; dermal

necrosis; a decrease in leukocytes; hemorrhage; nervous

disorder; and death (Fig. 5) (10,14,17,26,28). In 1938,

Russian scientists determined the disease was associated

with S. chartarum (then known as S. alternans) growing on

the straw (Fig. 6) and grain fed to the animals. Intensive

studies were then conducted resulting in the first

demonstrated toxicity of S. chartarum in animals. Horses

were actually fed cultures of the fungus. Contents from 30

petri plates containing the fungus were fed to horses and

resulted in death, while even the contents of one plate

resulted in sickness. Horses seem to be especially

susceptible to these toxins; 1 mg of pure toxin is reported

to cause death (14). Most outbreaks were associated with

hay or feed that became infested during storage under wet

conditions. The Russians coined the term

stachybotryotoxicosis for this new disease. Since then,

stachybotryotoxicosis has been reported on numerous farm

animals from various parts of the world, especially in

eastern Europe, but apparently has not been reported on

animals in North America (26,55,61).

Fig. 5. Hyperplastic dermatitis on a horse four days after

feeding on straw infested with S. chartarum. Notice the

scaly appearance of the upper lip area. Photograph

reprinted from Sarkisov, A. Kh. 1954. Mikotoksikozi

(Gribkovye otravleniia). Moscow. 216 pp. (click image for

larger view).

http://www.apsnet.org/online/view.asp?ID=81

In the late 1930s, stachybotryotoxicosis was reported in

humans working on collective farms in Russia (10,14,17,29).

People affected were those who handled hay or feed grain

infested with S. chartarum or were exposed to the aerosols

of dust and debris from the contaminated materials. Some of

these individuals had burned the straw or even slept on

straw-filled mattresses. The infested straw was often black

from growth of the fungus. Common symptoms in humans were

rash, especially in areas subject to perspiration,

dermatitis, pain and inflammation of the mucous membranes

of the mouth and throat, conjunctivitis, a burning

sensation of the eyes and nasal passages, tightness of the

chest, cough, bloody rhinitis, fever, headache, and

fatigue. Workers developed symptoms within two to three

days of exposure to the fungus. Some members of the Russian

teams investigating this disease rubbed the fungus onto

their skin to determine its direct toxicity. The fungus

induced local and systemic symptoms similar to those

observed in naturally occurring cases. The article by

Drobotko (10) is a good source of information on the

Russian experience with this problem.

As recently as 1977 there was an outbreak of

stachybotryotoxicosis among farm workers handling infested

straw in Hungary (1). The symptoms were similar to those

described in Russia and began appearing about 24 hours

after exposure to the fungus. One interesting result of the

investigation was that S. chartarum was cultured from

scraping made from symptomatic areas of the skin and from

samples taken from the nose and throat. Most workers

recuperated when they stopped handing the infested straw.

In 1996 workers at a horticultural facility in Germany

developed very painful, inflamed lesions on their

fingertips followed by scaling off of the skin when they

handled decomposable pots infested with S. chartartum (Fig.

7) (9). The pots were made of recycled paper.

Between the 1950s and the 1980s there were continued

publications on S. chartarum but none that indicated a

potential problem with S. chartarum in homes and buildings.

In 1986, Croft et al. (6) reported an outbreak of

trichothecene toxicosis in a Chicago home. Over a 5-year

period, the family complained of headaches, sore throats,

flue symptoms, recurring colds, diarrhea, fatigue,

dermatitis, and general malaise. Air sampling of this home

revealed spores of S. chartarum. The fungus was found

growing on moist organic debris in an uninsulated cold air

duct and on some wood fiber ceiling material. The home had

a chronic moisture problem that favored mold growth.

Extracts from the duct debris and contaminated building

materials were toxic to test animals and several

macrocyclic trichothecenes were identified in the extracts.

When the mold problem was corrected, these symptoms

associated with trichothecene toxicosis disappeared.

Since the paper by Croft et al. (6), there have been

numerous reports of S. chartarum in homes/buildings in

North America, but few definitive studies implicating the

fungus as the primary cause of mycotoxicosis in indoor

environments. One important paper by Johanning et al. (37)

reported on the health of office workers in a flooded New

York office building with high concentrations of S.

chartarum on gypsum wall board (i.e., sheetrock). The study

concluded " . . . self-reported health status indicator

changes and lower T-lymphocyte proportions and dysfunction

as well as some other immunochemistry alterations were

associated with onset, intensity and duration of

occupational exposure to toxigenic S. chartarum combined

with other atypical fungi. " Another intensive study by

Hodgson et al. (31) described an outbreak of disease in a

mold contaminated courthouse and office building. The

occupants developed fatigue, headaches, chest tightness,

mucous membrane irritation and pulmonary disease. The

building had serious moisture problems due to various

factors. Interior surfaces were heavily contaminated with

S. chartarum, Aspergillus versicolor and Penicillium

species, and mycotoxins were identified in moldy ceiling

tiles and vinyl wall coverings. These researchers concluded

that a mycotoxin-induced effect was a likely cause of

disease. The primary fungus involved, however, could not be

determined. Cooley et al. (4) reported on the correlation

between prevalence of fungi and sick building syndrome

after a long study in schools where there were concerns

about indoor air quality. They concluded that Penicillium

and Stachybotrys species may be associated with sick

building syndrome.

In 1993-1994 a cluster of cases of pulmonary hemorrhage and

hemosiderosis in infants occurred in Cleveland, Ohio.

Because this is rarely observed in infants, an intensive

study into the cause of the problem was initiated. There

were several factors associated with this outbreak, but an

important finding was that all homes of these infants had

high levels of total fungi and S. chartarum (based on air

and surface sampling) (8,12). Furthermore, isolates of S.

chartarum from the homes were shown to produce

trichothecenes (34). The homes had previously sustained

water damage which resulted in the mold contamination. It

was this Cleveland event that initiated the headline news

of Stachybotrys. Additional evidence of the association of

S. chartarum with pulmonary hemorrhage in infants has since

been published (13,39,56,58). An important contribution to

understanding the role of S. chartarum in this disease was

the isolation of the fungus from fluid washed from the

lungs of a 7 year old boy (11). The child had chronic cough

and fatigue, intermittent low grade fever, and recurrent

pneumonia. His home was damaged from a flood and in an area

near the bedroom S. chartarum and other fungi were growing

on wallpaper. The child became symptom-free when removed

from the contaminated environment. This is apparently the

first isolation of the fungus from human body fluids.

There is considerable controversy, however, about the role

of S. chartarum in pulmonary hemorrhage in the Cleveland

incident and in human health in the indoor environment

(15,16,19,30,36,50,54). Some members of the scientific-

medical community believe there is insufficient evidence to

prove a solid causal relationship between S. chartarum and

these health problems. Indeed, in 2000 the Centers for

Disease Control and Prevention in Atlanta (3) published two

reports critical of the study conducted in Cleveland and

concluded that the association between S. chartarum and

acute pulmonary hemorrhage/hemosiderosis was not proven.

One of the most important areas where we lack information

is the relationship between exposure to bioaerosols of S.

chartartum (both in time and amount of the fungus) and

effects on human health.

The possibility exists that there are multiple modes of

action for S. chartarum to affect human health.

Mycotoxicosis is clearly important but the

immunosuppressant compounds may also have a role, although

it is not clearly understood. The bioactive compounds may

lead to lung dysfunction through various mechanisms

(44,46). In addition, hemolytic compounds may be important,

especially in infants (57). The presence of a hemolysin may

lead medical investigators to view this fungus as a

potential pathogen and not strictly as a mycotoxin

producer. Also, the fungus could be an allergen (41). Plus,

two or more of these modes may act together as suggested by

Jarvis et al. (33).

Although there are many unanswered questions about the

effects of S. chartarum on human health, the accumulation

of data (from observations and research) over the past 65

years tells us that one should not handle materials

contaminated with S. chartarum (without proper safety

procedures) and strongly indicates that indoor environments

contaminated with S. chartarum are not healthy, especially

for children, and may result in serious illness.

Where S. Chartarum Occurs Indoors

The spores of S. chartarum are in the soil and are

introduced along with flood waters or the dust and dirt

entering with the water incursion. Also, building materials

at the time of construction can have a coating of dust or

dirt that contains S. chartarum. The fungus is most

commonly found in homes or buildings which have sustained

flooding or water damage from broken pipes, roof, wall or

floor leaks, condensation, etc. Wet conditions are required

to initiate and maintain growth. It is most common on the

paper covering of gypsum wall board, but can be found on

wallpaper, cellulose based ceiling tiles, paper products,

carpets with natural fibers, paper covering on insulated

pipes, in insulation material, on wood and wood paneling,

and on general organic debris (Figs. 8 to 10). The paper

covering on fiberglass insulation is another area for

growth (Fig. 11). The fungus can be hidden in the ceiling,

walls or floors with no or little visible evidence within

the interior of the room. The spores, however, can

contaminate the interior of the room through holes and

cracks in the building materials (aided by negative

pressure) or be transported via the air handling system. It

can also be found growing in ducts if there is organic

debris. Condensation due to poor design or faulty heating,

ventilation, and air conditioning systems can promote

growth of the fungus. The fungus will usually produce large

amounts of conidiophores and conidia giving the substrate a

black appearance that can be slightly shiny when fresh and

powdery when dry. I have observed the fungus growing

profusely on the paper covering of gypsum wall board within

a week after flood water was drained from a building.

Detection and Remediation

Detection of S. chartarum is usually by visual inspection

and/or air and surface sampling. Because this fungus is not

readily airborne compared to other fungi, air sampling in a

contaminated indoor environment may show low levels of

spores in the air. Also, some media used for mold

evaluation of indoor air are not adequate for growth of S.

chartarum. Inspection of potential sites of contamination,

especially in covered and protected places, is a necessity

to determine where the fungus occurs and the level of

contamination. If areas contaminated with S. chartarum are

discovered, do not attempt to solve the problem without

following recommended safety procedures for working with

toxic molds, especially if heavily contaminated. Get advice

if there is a serious problem.

These are some general comments about remediation. Refer to

the guidelines in the New York web site in the Author's

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