New article from IAQ (Indoor Air Quality) on the serious affects of inhalation of toxic mold
Tamara R Pearlman
niehs.nih.gov
The issue of mold contamination has drawn the national and
international spotlight on the heels of publicity about prominent
situations, such as a hotly contended link between mold and severe
illness--and one death--in 10 Ohio infants in 1993 and 1994; a major
2001 insurance battle over the moldy Dripping Springs, Texas, house of
Melinda Ballard and her family; the mushrooming mold infestations
indoors and out along the Gulf Coast after Hurricanes Katrina and Rita
slammed ashore in 2005; and the mold infestation that helped spur the
February 2007 outcry over the treatment given to recuperating soldiers
at Walter Reed Army Medical Center. As recently as 25 years ago,
inhaled mold was considered primarily a nuisance, not a serious health
threat. But the growing scientific and medical evidence suggests the
threat is widespread and, for some people, quite serious.
In the 9 June 2006 report Mold Prevention Strategies and Possible
Health Effects in the Aftermath of Hurricanes and Major Floods, the
CDC concluded that "excessive exposure to mold-contaminated materials
can cause adverse health effects in susceptible persons regardless of
the type of mold or the extent of contamination." The CDC based some
of its findings on a landmark 2004 report, Damp Indoor Spaces and
Health, by the Institute of Medicine (IOM) of the National Academies.
Relying on the IOM report, and dozens of studies and reports that have
been published since, many organizations and individuals that must
deal regularly with mold problems have begun to take steps to reduce
the threat.
Mold on the move. Recent high-profile news reports have raised
awareness of the possible threats posed by indoor molds such as
Stachybotrys chartarum, also known as S. atra.
But many of the puzzle pieces--exactly who is vulnerable, to what
extent, and under what conditions--are still missing. The vast
information gaps that remain continue to feed significant controversy
in the legal, insurance, political, scientific, medical, public
health, and building design, construction, management, and maintenance
arenas.
Growing Suspicion
Of the 100,000 or so known fungal species found on the planet, about
500 species are currently thought to be harmful to people, according
to the CDC. Some of those that pose ingestion threats (such as
Aspergillus, via contaminated grains and nuts) or skin infection
threats (such as Trichophyton, which causes athlete's foot) have been
either well-recognized or strongly suspected for years, even
centuries. As for inhalational threats, although molds such as
Stachybotrys and Aspergillus have received perhaps the most popular
attention, scientists are not yet sure which species may be the worst
for human health.
A few threats from inhaled molds have been perceived for a long time.
Since the 1890s, outdoor settings in the U.S. Southwest have been
linked with coccidioidomycosis, caused by a fungus in the soil. At
least 50 years ago, there were some indications of mold-related health
problems in agricultural and certain occupational settings, causing
illnesses such as pneumomycotoxicosis. In areas near rivers in the
central United States, a fungus has been known for at least 30 years
to cause blastomycosis. By about 25 years ago, there was some initial
evidence that damp indoor spaces were linked with health problems such
as bronchitis, asthma, cough, wheeze, and shortness of breath. But
there has been little specific knowledge until recently.
Wherever they grow, molds must have some source of water and food. The
accumulating evidence has shown that problems with mold can surface
anywhere in the world after just one or two days of moisture exposure,
in settings wet or dry, hot or cold, north or south. The same
conditions that give rise to mold growth also support many bacteria.
Many components and emissions from these fungi and bacteria are known
or suspected to harm human health. Mycotoxins, which are secondary
fungal metabolites, have been one primary focus, and more than 180
have already been identified. Other components of fungi or bacteria in
damp spaces that are known or suspected to pose a threat include
volatile organic compounds, live or dead spores, fragments such as
beta glucans, and numerous allergens.
Indoor Mycotoxins have often been the main point of contention in
recent insurance claims and lawsuits over suspected harm from moldy
buildings. In the 2004 EPA-funded report Guidance for Clinicians on
the Recognition and Management of Health Effects Related to Mold
Exposure and Moisture Indoors, researchers at the Center for Indoor
Environments and Health at the University of Connecticut Health Center
wrote that mycotoxins can elicit responses in almost anyone they come
in contact with, that the health effects are worrisome, and that
infants, at least, should be removed from suspect settings.
After reviewing the evidence available by 2004, the IOM concluded
there are moderately strong or at least limited links between damp
indoor spaces and a handful of health problems, such as asthma, cough,
wheeze, hypersensitivity pneumonitis, and a range of other upper and
lower respiratory problems. For other health problems under suspicion
based on many anecdotal accounts and limited scientific and medical
evidence, such as headache, memory loss, nausea, diarrhea, diabetes,
fatigue, and fever, the lack of incontrovertible evidence was
typically due to a lack of rigorous research, not because of studies
that conclusively disproved a connection.
Among the weaknesses the IOM notes in many current studies is a
tendency to use self-reported visual or odor presence of mold, instead
of actual measurments of some kind, and little consideration of
multiple exposures, including additive or synergistic effects. In
addition, the committee noted that its findings did not address people
with compromised immune systems.
Why Now?
It is likely that building dampness and mold have caused widespread
but largely unrecognized adverse respiratory health effects for
centuries, says William Fisk, acting division director for the
Environmental Energy Technology Division at the Lawrence Berkeley
National Laboratory. But the increasing immune-compromised population
around the world may be one reason why health problems from inhaled
mold and bacteria appear to be on the rise recently. Population
growth, higher percentage of elderly, emerging diseases such as HIV,
and increases in smoking and in many chronic illnesses (often for
unknown reasons) are only a few of the reasons that, compared to just
a century ago, there are hundreds of millions more peoplewith weak or
stressed immune systems. The CDC has identified many immunocompromised
subpopulations, as well as pregnant women, as being potentially more
vulnerable to exposures in damp indoor spaces.
In addition, the dramatic increase in the percentage of people living
in urban areas may be playing a part. Researchers at Hospital General
Universitario Gregorio Maranon in Spain reported in the June 2006
issue of Medical Mycology that Aspergillus spores in outdoor air are
more common in urban than rural settings in the province of Madrid.
Worldwide population increases have also pushed more people into
wetter settings, such as coastal and riparian floodplains, other
bottomlands, and hurricane-prone areas.
Other risk factors arise from modern building practices, conveniences,
and shortcuts. Poorly built flat roofs cannot shed rainwater, while
venting clothes dryers indoors can direct moist air to vulnerable
interior surfaces. Tighter building envelopes in modern homes slow the
escape of water vapor associated with bathing, cooking, and even
breathing; newer homes also have insulation-filled cavities that dry
slowly after the inevitable small leaks. Further, the tight seal on
newer housing may exacerbate problems during the heating of buildings,
when humid indoor air contacts cold walls or windows (although the
reverse is true for an air-conditioned building when it is hot
outdoors). Also, there are many anecdotal reports that molds grow more
readily on the paper-coated surfaces of modern wallboard than on older
plaster walls. A few companies have introduced wallboard products they
say are more resistant to mold growth, but some critics say these
products still may support mold in settings that routinely get wet,
such as kitchens, bathrooms, or areas with leaks of some type.
The substantial increase in air conditioning all over the world is
another potential culprit, with more than fifteen studies consistently
indicating a strong link with numerous respiratory symptoms, says
Fisk. Microbes thriving in air conditioning systems, including fungi
and bacteria, likely contribute to that link, he says.
Buildings have often been constructed without sufficient attention
paid to indoor water problems. In an assessment of health and economic
impacts of dampness and mold published in the June 2007 issue of
Indoor Air, Fisk and EPA indoor environment specialist David Mudarri
found that approximately 47% of U.S. homes have dampness or mold
problems. Their review of other studies led them to conclude that
schools, offices, and institutional buildings have similar problems.
The EPA Building Assessment Survey and Evaluation Study of 100
randomly selected U.S. office buildings supports that conclusion, with
its finding, reported at the 2002 9th International Conference on
Indoor Air Quality and Climate, that 45% had ongoing water damage
problems. University of Cincinnati environmental health professor
Tiina Reponen and her colleagues noted in a May 2006 study in the
Journal of Occupational and Environmental Hygiene that the percentage
of buildings of all types that have mold contamination is likely much
higher in tropical and subtropical settings.
Cracking the Mold Code
Many new studies have provided additional evidence that mold likely
deserves serious attention. Fisk and Mudarri demonstrated in their
June 2007 assessment that 21% of current U.S. asthma cases may be
attributable to dampness and mold in homes, with schools, offices, and
institutional buildings playing a similar unhealthy role. In a
companion meta-analysis of 33 studies also published in the June 2007
issue of Indoor Air, Fisk and Berkeley Laboratory colleagues found
that dampness and mold exposures increase the occurrence of a range of
respiratory problems by 30-50%.
Inner workings. Light micrograph shows a section of a human lung tisse
(blue) embedded with Aspergillus (dark brown). Aspergillosis is caused
by the inhalation of fungal spores, which are usually present in the
air. In healthy people, the immune system destroys the spores before
they cause any harm. In those with a weakened immune system, however,
the infection is potentially fatal.
Many other examples of potentially significant findings have been
published in the past three years. In the May 2004 issue of EHP, Kati
Huttunen ofthe Finnish National Public Health Institute and colleagues
demonstrated synergism between various indoor fungi and the bacterium
Streptomyces californicus, includingincreases in production of tumor
necrosis factor-α and interleukin-6 in various circumstances. In the
February 2006 issue of Toxicology and Applied Pharmacology, a Michigan
State University team described exacerbated damage when exposure to a
mycotoxin was preceded by exposure to a bacterial fragment, in this
case the endotoxin component lipopolysaccharide. More detailed
knowledge of the wide-ranging olfactory system damage that a mycotoxin
can wreak appeared in the July 2006 issue of EHP, and in the following
month's issue, Case Western Reserve University researchers described
how they identified potential biomarkers of mycotoxin exposure. An
article in the 3 June 2007 issue of Toxicology addresses elucidation
by a second Finnish team of specific accelerated genotoxic and
cytotoxic damage by a cultivated fungus-bacterium mixture.
EPA research biologist Stephen Vesper and colleagues have performed a
series of experiments to develop better methodology for predicting
mold exposure risk. After almost a decade and a half of work, they
have created a Relative Moldiness Index that uses quantitative
polymerase chain reaction to measure concentrations of 36 indicator
mold species present in floor dust samples taken inside a building.
This standardized analysis, described in the January 2007 issue of the
Journal of Exposure Science and Environmental Epidemiology, is used to
indicate the amount of water damage in a home, providing more accurate
exposure information that may help to predict health problems. They
expect to soon publish information about its successor, the
Environmental Relative Moldiness Index, which covers more buildings in
more geographic settings, and benefits from improved sampling
protocols and analysis of information.
As researchers explore the potential contributions of damp conditions
to human health problems, they'll need to be careful about exactly
which test animals they use. Several reports, such as a Harvard study
in the October 2006 American Journal of Respiratory Cell and Molecular
Biology, have shown that different mouse strains vary significantly in
their biological responses to a tested fungus. In addition, scientists
face the usual uncertainties inherent in extrapolating results from
any animal testing to humans.
Not Messing Around
Until very recently, building design was not widely acknowledged as an
important factor in preventing water problems. As recently as 2005,
the American Institute of Architects (AIA) emphasized in an issue
brief to its members that mold problems are tied to maintenance of a
building's plumbing and ventilation systems, not the initial building
design. Just a year later, however, an article in the 29 September
2006 edition of the AIA publication AIArchitect emphasized that design
details are critical in preventing mold problems. Some of the points
of vulnerability highlighted included roof underlayments, concrete
foundation sealants, flashing around windows and doors, and grading
around the building.
Home-based health threat. A University of Cinncinnati researcher
prepares to sample air inside a moldy Gulf Coast home that was flooded
in the 2005 hurricane season.
Many contractors also are paying more attention. "We've told builders
to be vigilant about moisture issues in all stages and to treat it
seriously," says David Jaffe, vice president of construction liability
and legal research with the National Association of Home Builders. But
problems still occur, he acknowledges, citing the continuing stream of
insurance claims and lawsuits over mold concerns in both residential
and nonresidential buildings: "It's an ongoing issue. We're always
looking for ways to improve."Other organizations, such as the American
College of Occupational and Environmental Medicine and the American
College of Medical Toxicology, remain skeptical that mold poses a
serious threat to more than a small number of people.
Doubts about mold threats, uncertainty over who should be responsible
for problems that may arise, and variable guidance on appropriate
remediation continue to play a role in political responses to mold
concerns. At least 46 states and the District of Columbia have
approved some type of insurance coverage limitation for residential
policies, and such exclusions are becoming more common for commercial
properties, says Michael Barry, director of media relations for the
U.S. Insurance Information Institute. According to the National
Conference of State Legislatures, since 2001 at least 31 states have
approved, have rejected, or continue to consider laws that address
mold problems in some way, such as contractor liability, real estate
agent or landlord liability for disclosure, or licensing of mold
inspectors, testers, and remediators.
Given the evidence at hand, Health Canada has determined that mold may
pose a health hazard, and on 31 March 2007 released brief
recommendations for cleaning up mold in residences.The EPA is
developing guidelines for moisture control "best practices" in all
phases of design, construction, and maintenance, and may finalize the
guidelines in 2008, says Laura Kolb, an environmental health scientist
with the agency's Indoor Environments Division.
Much more information continues to surface through research and public
health efforts around the world, and there is some communication among
various groups. But "not much has been done to move the science
forward that's applicable to broad populations," says Allison Stock, a
toxicologist with the CDC's National Center for Environmental Health.
One roadblock may be that there is no concerted, coordinated national
or international effort to address the dozens of information gaps
identified in the IOM report.
Given such shortcomings, "We're still quite some way from being able
to set [exposure and remediation] standards," says Marsha Ward, a
principal investigator in the EPA Immunotoxicology Branch. In the
interim, groups such as the Restoration Industry Association are
giving it their best shot and updating remediation guidelines for
their members, targeting completion by 2008, says communications
director Patricia Harman.
Another critical area requiring attention is the very limited
repertoire of effective medical treatments to prevent illness or treat
people experiencing certain ill effects such as allergic
bronchopulmonary aspergillosis and acute idiopathic pulmonary
hemorrhage, says Lynnette Mazur, a professor of pediatrics at the
University of Texas Medical School at Houston and coauthor of a 6
December 2006 Pediatrics policy statement on noninfectious health
effects from molds. Mazur points out that with respect to allergic
rhinitis and asthma, however, there are very effective environmental
and pharmacological treatments available.
Regardless of all the remaining uncertainties, the overall
recommendations of many organizations and agencies worldwide are
reaching a common conclusion: Don't mess with mold. If you can see or
smell it--and especially if health problems are occurring--clean it out,
throw it out, or get out.