A Spreading Concern: Inhalational Health Effects of Mold

[Guest guest]

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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.

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Environmental Health Perspectives

http://www.ehponline.org/members/2007/115-6/focus.html

A Spreading Concern: Inhalational Health Effects of Mold

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 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.

closeup of mold

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.

image: American Phytopathological Society

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.

moldy walls at Walter Army Medical Center

Bad scene. A section of wallpaper is pulled back to reveal mold in

Building 18 of the Walter Army Medical Center. Indoor mold and

the bacteria that often grow with it are believed to pose a greater

threat to immunocompromised people.

image: AP Photo/ Dharapak

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 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 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%.

lung tissue

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.

image: Photo Researchers, Inc.

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–? 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 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.

moldy home from Gulf Coast

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.

image: Ginger Chew/Mailman School of Public Health

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 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 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 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 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 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.