EPA Children's Health Initiative: Toxic Mold

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Outbreaks of the fungi Stachybotrys chartarum (S. chartarum) are

under investigation for an association with the deaths of infants in

Cleveland, Ohio, and serious health problems in other areas of the

U.S. Although not widely found, Stachybotrys chartarum has been

studied for the last 20 years. The following is documented.

Chartarum produces toxigenic spores that are potentially hazardous,

especially when the air-conveyance system is involved.

Furthermore, it is now appreciated that the principal biology

responsible for the health problems in such building are fungi

rather than bacteria or viruses.

Although fungi in this context have been traditionally viewed as

allergens (and, in unusual circumstances, pathogens), data have

accumulated to show that the adverse health effects resulting from

inhalation of fungal spores are due to multiple factors. One factor

associated with certain fungi is small molecular toxins (mycotoxins)

produced by these fungi.

However, mycotoxins tend to concentrate in fungal spores, and thus

present a potential hazard to those inhaling airborne spores.

Toxigenic spores strongly affect alveolar macrophage function and

pose a threat to those exposed. Reports have indicated that

Stachybotrys chartarum, Aspergillus versicolor, and several

toxigenic species of Penicillium are potentially hazardous,

especially when the air-handling systems have become heavily

contaminated.

Perhaps the most hazardous of the toxigenic fungi found in wet

buildings is S. chartarum, a fungus known to produce the very potent

cytotoxic macrocyclic trichothenes along with a variety of

immunosuppressants and endothelin receptor antagonists mycotoxins.

Antimicrobial Treatment

Biological agents do not have to be alive to cause allergic, toxic,

or inflammatory responses; however, the organisms that are sources

of indoor biological contamination are living, multiplying

organisms.

Concentration profiles and exposure levels will be calculated for an

infant, child, and adult. Once the emission rates are known, the

RISK Model is a useful tool in predicting exposure.

Children's Health Initiative: Toxic Mold

http://www.epa.gov/appcdwww/iemb/child.htm

Outbreaks of the fungi Stachybotrys chartarum (S. chartarum) are

under investigation for an association with the deaths of infants in

Cleveland, Ohio, and serious health problems in other areas of the

U.S. Although not widely found, Stachybotrys chartarum has been

studied for the last 20 years. The following is documented.

Chartarum produces toxigenic spores that are potentially hazardous,

especially when the air-conveyance system is involved.

Currently there are no EPA regulations or guidelines for evaluating

potential health risks of chartarum contamination and remediation.

Chartarum is a greenish-black fungus that can grow on materials with

a high cellulose and low nitrogen content (such as fiberboard,

gypsum board, dust and lint).

The prevalence of chartarum contamination in indoor environments is

unknown.

Sample collection of chartarum may be difficult due to the presence

of other species of less toxic fungi.

Remediation of chartarum must be performed with much care to isolate

and contain the spread of contamination and maintain the safety of

the trained remediator.

Visit the General Clinical Research Center, Cleveland, OH, site for

additional information about Stachybotrys.

The following is background information, current research, and

research needs.

Background

The past twenty years have brought the recognition that an important

factor in the health of people in indoor environments is the

dampness of the buildings in which they live and work. Furthermore,

it is now appreciated that the principal biology responsible for the

health problems in such building are fungi rather than bacteria or

viruses. Although fungi in this context have been traditionally

viewed as allergens (and, in unusual circumstances, pathogens), data

have accumulated to show that the adverse health effects resulting

from inhalation of fungal spores are due to multiple factors. One

factor associated with certain fungi is small molecular toxins

(mycotoxins) produced by these fungi. Traditionally, mycotoxins are

held to be important in human and animal health because of their

production by toxigenic-fungi-associated food and feed. However,

mycotoxins tend to concentrate in fungal spores, and thus present a

potential hazard to those inhaling airborne spores. Toxigenic spores

strongly affect alveolar macrophage function and pose a threat to

those exposed. Reports have indicated that Stachybotrys chartarum,

Aspergillus versicolor, and several toxigenic species of Penicillium

are potentially hazardous, especially when the air-handling systems

have become heavily contaminated.

Perhaps the most hazardous of the toxigenic fungi found in wet

buildings is S. chartarum, a fungus known to produce the very potent

cytotoxic macrocyclic trichothenes along with a variety of

immunosuppressants and endothelin receptor antagonists mycotoxins.

This fungus was investigated for its association with the serious

health problems of a family living in a water-damaged home in

Chicago and has been implicated in several cases of building-related

illness. A cluster of cases of acute pulmonary

hemorrhage/hemosiderosis was reported in Cleveland, Ohio, where 27

infants from homes that suffered flood damage became sick (nine

deaths) with the illness starting in January 1993.

Current Research

Although a great deal of literature describes fungi growing on a

variety of building and structural materials that resulted in

contamination of buildings and sick individuals, information on what

environmental conditions permitted their growth has been limited.

Starting in 1991, EPA has conducted research into the environmental

conditions that permit building material colonization by fungi and

the subsequent development of contamination sources. The focus has

been on evaluating material properties, climate conditions, and

microorganism interactions that contribute to materials serving as

microecological habitats fostering fungal colonization,

amplification, and dissemination. To better understand when fungal

growth occurs, we developed a static chamber method for evaluating

the various environmental conditions. These chambers were designed

to provide controlled environments that can simulate differing

conditions of temperature and relative humidity that the materials

might be exposed to in a building. Over the last five years, a

variety of building materials and fungi have been evaluated using

this static chamber method and it is in the process of being

transitioned to a Standard Guide for ASTM International.

One of the most significant technical results from this project is

that the effect of relative humidity is indirect and that very small

amounts of moisture, well below those commonly cited, will permit

growth. The amount of moisture required for fungal growth can vary

depending upon the material and the organism. S. chartarum requires

high levels of moisture (effective relative humidity required for S.

chartarum growth would be 94%) and cellulose-containing materials

for growth.

Antimicrobial Treatment

Biological agents do not have to be alive to cause allergic, toxic,

or inflammatory responses; however, the organisms that are sources

of indoor biological contamination are living, multiplying

organisms. One approach to limiting exposure is to reduce the levels

of biological contamination. Antimicrobial agents, called fungicides

or biocides, have long been used to control, prevent, and remediate

microbial growth for many different applications in the environment.

The potential for antimicrobials and antimicrobial treatments

including encapsulants to reduce exposure to S. chartarum will be

investigated by EPA. Both static and dynamic chamber experiments

will be run using new and used building materials with and without

antimicrobial treatment and encapsulants/sealants.

Aerosolization/Emission of Fungal Spores

Although it is known that fungi growing on surfaces are capable of

generating particulate (spore) and gas phase (VOC) emissions, the

actual impact on the indoor environment has not been determined

quantitatively for most organisms because there is little

information on the dynamics of fungal spore release from the

contaminated surfaces. For example, what is the significance of 10

m2 of Stachybotrys chartarum growing on ceiling tile? That fungi

growing or deposited on surfaces become aerosolized is well known.

Indeed, sporulating fungi depend on aerosol emission for

propagation. Recent experiments with A. versicolor and P.

chrysogenum have started to elucidate some of the relationships

between commonly measured indoor environmental parameters and fungal

emissions. Documenting the production of spores and mycotoxins by S.

chartarum will assist in determining the magnitude of the health

threat in the indoor environment that is posed by these emissions.

Many factors affect the emission and dissemination of fungi into the

indoor air from the contaminated source. A clear understanding of

the factors, such as activity (translational energy), air flow, and

relative humidity, that enable and/or promote emission is required.

High humidity is important for those active release mechanisms that

depend on rupture of turgid cells, while tissue desiccation in low

humidity is important to another class of release mechanisms. The

reported experiments have generally been conducted under equilibrium

conditions in simple systems, however, and the impact of the indoor

microenvironment has not been considered.

The objective of this work will be the measurement of emission

factors for fungi growing on common building materials. To that end,

we will investigate the emissions and dissemination characteristics

of a variety of S. chartarum on different materials under differing

conditions (i.e., humidity, temperature, air-flow, mechanical

factors). The experiments will be performed using the Dynamic

Microbial Test Chamber. Tests will be conducted under known,

favorable growth conditions and under known flow conditions.

Environmental conditions (temperature, relative humidity, and air

flow rate) will be controlled, and experiments will be conducted at

a range of conditions. Air samples will be collected using real-time

instruments (optical particle counters, or OPCs) or integrated

samples such as filter mass samples, microbial filters, or microbial

impactors. The measurements will be made periodically, depending on

the organism's growth rate, emission rate, and type of measurement.

Surface microbial samples will also be collected directly or through

the glove wall. Contact plates may be appropriate for some

materials, while others may be better sampled by pre-cutting

portions of the material to allow extraction. Amounts appropriate to

the emission will be selected. Particle measurements will be

conducted at multiple locations within the chamber to quantitate

dispersion.

Model to Predict Indoor Air Quality (IAQ) Impact

Chamber studies at specified environmental conditions will yield

emission rates unique for S. chartarum. However, to relate the

emission rates to actual exposure, an IAQ model will be used which

can estimate concentration and potential exposure, as is done with

other indoor air contaminants. The model to be used will be the RISK

IAQ Model for Windows, a completely mixed room model incorporating

source/sink behavior that can generate concentration and exposure

estimates as a function of time. The ventilation flows (none or

limited outdoor air up to 5%) and pollutant emission rates can be

set as desired for each modeled room. A variety of building types

will be modeled, from a home completely sealed or with average air

exchange rates to a centralized HVAC system in an apartment

environment.

Concentration profiles and exposure levels will be calculated for an

infant, child, and adult. Once the emission rates are known, the

RISK Model is a useful tool in predicting exposure.

Expected Milestones

Determination of whether a contaminated porous or non-porous surface

can be cleaned and free from S. chartarum contamination using

antimicrobials.

Determination of effectiveness in containing S. chartarum

contamination, by use of antimicrobial encapsulation.

Determination of the environmental conditions required for

sporulation, emission, aerosolization, dissemination and transport

of S. chartarum into the indoor air.

Determination of the use of antimicrobials, encapsulants, and

filtration in the mitigation and prevention of S. chartarum under

conditions found to exist in problem buildings.

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Research Laboratory

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Last updated on Tuesday, May 2nd, 2006

URL: http://www.epa.gov/appcdwww/iemb/child.htm