Indoor moulds and human health
Erica Weir
CMAJ

Epidemiology

Stachybotrys atra (also called S. chartarum and S. alternans) is a
dark-coloured fungus that grows well on damp materials that have a
high cellulose concentration, such as straw, grass, sawdust and
lumber. Its toxin can produce skin and mucous membrane irritation,
lymphocytic depletion and hemorrhagic syndrome in farm animals.1 The
question of whether it also produces hemorrhagic effects in humans
was raised in 1994 when a cluster of 8 cases involving infants in
Cleveland who developed idiopathic pulmonary hemosiderosis was
noted.2 Preliminary results of a case-control study indicated that
hemorrhage was associated with major household water damage during
the 6 months before illness and increased levels of measurable
household fungi, including the mould Stachybotrys (odds ratio 1.6,
95% confidence interval 1.0-30.8).3

Despite the researchers' caution that further study was needed to
determine causality, the alarming suggestion that exposure to this
fungus might be fatal led to the rapid closure and cleanup of
contaminated buildings, including portable classrooms in Ontario.4

It now appears that the health risks posed by Stachybotrys may not
be as hazardous as initially perceived. In March 2000 the Centers
for Disease Control and Prevention (CDC) in Atlanta released the
results of 2 separate reviews of the Cleveland investigation.5 The
reviewers concluded that the association between cases of pulmonary
hemorrhage in infants in Cleveland and household water damage or
exposure to S. atra was not adequately substantiated by scientific
evidence. The cause of acute idiopathic pulmonary hemorrhage is
unresolved; the CDC recommends further surveillance and improved
assessment of environmental exposure to moulds and fungi.

These shortcomings demonstrate the methodologic difficulties
involved in assessing the health effects of indoor moulds. Fungi and
actinomycetes cause a variety of illnesses because of their direct
infection of human tissue. These conditions are well known. The
indirect nonspecific illnesses caused by these organisms are less
clear and more difficult to demonstrate. Possible pathologic
mechanisms for the indirect (noninfectious) causes include immune-
mediated (hyper-sensitivity pneumonitis), toxic (mucosal irritation)
and carcinogenic (aflatoxin) mechanisms. An expert panel has
recently reviewed the evidence supporting causal relationships
between certain fungi and a variety of these types of health
effects.6 People with diabetes, immunosuppression or atopy are
apparently susceptible populations, as well as infants.

Clinical management

In this case an indirect effect (pulmonary hemosiderosis) was
suspected to have been caused by S. atra. What should a physician do
when confronted with a case of hemoptysis in a child with no known
source of bleeding? Idiopathic pulmonary hemosiderosis is similar to
Goodpasture's syndrome. It is characterized by bouts of clinical or
subclinical pulmonary hemorrhage, but without the renal involvement
typical of Goodpasture's. Children are mainly affected; most have
iron-deficiency anemia and during bleeding episodes may have fever,
hyperbilirubinemia and reticulocytosis.7 To facilitate diagnosis and
reporting, the CDC is developing a standard case definition. In the
interim, such cases might be reported directly to the CDC and its
assistance sought regarding further investigations.

Recognizing patients in the office whose nonspecific respiratory and
systemic symptoms might be related to indoor mould exposure can be
challenging. Knowing which populations are at risk and knowing how
to take an environmental exposure history can be helpful.

Prevention

The best way to prevent mould growth is to keep all material in
homes as clean and dry as possible using adequate ventilation.
Surfaces where moisture collects frequently can be cleaned with a
baking soda solution one day and vinegar the next to keep moulds at
bay. In areas where flooding has occurred, prompt cleaning of walls
with water mixed with chlorine bleach, diluted 4 parts water to 1
part bleach, can prevent mould growth.8

Further information is available from the Canadian Mortgage and
Housing Corporation. It offers a wide range of housing-related
information, including clean-up procedures for mould in houses (800
668-2642; www.cmhc-schl.gc.ca). In addition, the College of Family
Physicians of Ontario has developed an Environment and Health Peer
Presenter Program (www.cfpc.ca/ocfp/cme/ehcpeer.html).

References


Elidemir O, Colasurdo G, Rossmann S. Fan L. Isolation of
Stachybotrys from the lung of a child with pulmonary hemosiderosis.
Pediatrics 1999;104:964-6.[Abstract/Full Text]
Acute pulmonary hemorrhage/hemosiderosis among infants - Cleveland,
January 1993-November 1994. MMWR 1994;43:881-3.
Update: pulmonary hemorrhage/hemosiderosis among infants -
Cleveland, Ohio, 1993-1996. MMWR 1997;46:33-5.
Region of Peel to hold news conference about Stachybotrys atra mould
[press release]. Available: www.toxicmold.org/documents/0321.htinl
(accessed 2000 Apr 17).
Update: Pulmonary hemorrhage/hemosiderosis among infants -
Cleveland, Ohio, 1993-1996. MMWR 2000;49:180-4. Available:
www.cdc.gov/epo/mmwr/preview/mmwrhunl/mm4909a3.htm (accessed 2000
Apr 17).
McMaster Institute of Environment and Health. Report of an expert
panel on fungal contamination indoors, 1999. Available:
www.mcmaster.ca/mich/furpt.htm (accessed 2000 Apr 17).
Stein J, editor. Internal medicine. Toronto: Mosby; 1998.
Canadian Mortgage and Housing Corporation. Clean-up procedures for
mold in houses. Ottawa: The Corporation; 1993. Available:
www.cmhcschl.gc.ca/publications/aboutyourhouse/ce08.html (accessed
2000 Apr 17).