Household mould, a type of filamentous
fungi, is a problem that most of us have had to deal with at some time or
another. It thrives in damp, humid spaces such as base-ments, bathrooms, air
conditioners, windowsills and wall cavities and, once it takes hold, can cause
serious damage to your home.
However, indoor mould can cause serious
damage to your health, too. There’s growing evidence that living in a damp and
mouldy environment can lead to all manner of medical problems—from respiratory
prob-lems such as wheezing to more serious conditions like depression.
Mould and asthma
A condition that’s been consistently linked
to household mould is asthma—particularly in children. While several studies
have shown that mould can exacerbate its symptoms, new evidence suggests that
it can even cause asthma to develop if children are exposed to it early on in
life.
Using the Asthma Predictive Index (API),
researchers from the University of Cincinnati in Ohio, USA, evaluated the risk
of future asthma among 483 children with and without visible mould growing in
their homes. They discovered that three-year-old children living with high
levels of visible mould in the home during early infancy were seven times more
likely to have a positive API, suggesting an increased risk of asthma, than
those living with no visible mould (Ann Allergy Asthma Immunol, 2009; 102:
131–7).
Other studies have also reported similar
findings. In one involving nearly 2000 UK children, the presence of a mouldy
smell in the home was a greater determinant than heredity in predicting the
develop-ment of childhood asthma (Environ Health Perspect, 2005; 113: 357–61).
In yet another study in school-age
children, those exposed to either mould or “dampness” during the first year of
life were at least twice as likely to suffer from asthma and respiratory
symptoms such as cough, wheezing or phlegm as those free of such exposure. As
the researchers concluded, “The results strengthen the evidence for a causal
association between ‘dampness’ and respiratory health, pointing to its possible
independent role in causing asthma” (Environ Res, 2009; 109: 59–65).
Indoor mould has been linked to asthma in
adults, too (Environ Health Perspect, 2002; 110: 543–7). Indeed, looking at the
facts and figures for children and adults together, it can be estimated that 21
per cent of all current asthma cases in the US may well be attributable to
dampness and mould in the home, as well as in schools, offices and
institutional buildings. This means that, of the approximately 22 million
people with asthma in the US, nearly five million cases may be due to damp and
mould exposure indoors (Indoor Air, 2007; 17: 226–35).
Conventional medicine’s answer to asthma is
hazardous drugs such as steroids and long-acting beta-2 agonists. Yet, looking
at the evidence, it appears that simply tackling mould and mildew (mould
growing on fabric) in the home will ease or even cure the problem for millions
of asthma sufferers.
Other health effects
Besides asthma and respiratory symptoms,
indoor mould has also been associated with a range of other health problems,
including headache, fever, excessive fatigue, cognitive and neuropsychological
effects, gastro-intestinal symptoms and joint pain—although the evidence still
requires further investigation (Can Fam Physician, 2002; 48: 298–302).
Perhaps one of the most intriguing
connections is that between house-hold mould and depression. Using survey data
from eight European cities compiled by the World Health Organization (WHO) in
2002 and 2003, researchers from Brown University in Providence, RI, found that
people living in damp, mouldy households were 34- to 44-per-cent more likely to
have a diagnosis of depression than the residents of mould-free homes (Am J
Public Health, 2007; 97: 1893–9).
Interestingly, the increased risk of
depression was also associated with the resident’s perception that such a damp,
mouldy environment cannot be controlled as well as with docu-mented physical
health problems linked to mould exposure. As lead researcher Edmond Shenassa
explained, “If you are sick from mould and feel you can’t get rid of it, it may
affect your mental health.”
However, it cannot be ruled out that
exposure to mould may also somehow alter the behavioural and biochemical brain
pathways involved in depression. Shenassa and his team are currently conducting
animal studies to investigate whether this is the case (Environ Health
Perspect, 2007; 115: A536).
Yet another concern is that mould exposure
could lead to cancer. At present, clear evidence is lacking, although one study
found that women exposed to moulds at work—of agricultural and industrial
origins—were two to three times more likely to have cervical and lip cancers
(Occup Environ Med, 2008; 65: 489–93). Whether the moulds found in homes have a
similar effect remains to be seen.
Mould and its toxic effects
Although it looks as if mould clings to the
surfaces it grows on, in fact, as it multiplies, tiny spores are released into
the air, where they are easily inhaled. According to Canadian researchers
Norman King and Pierre Auger, mould can then affect the body in a number of
ways (Can Fam Physician, 2002; 48: 298–302).
First, mould can trigger allergic reactions
such as asthma or a runny nose. Heavy and repeated exposures can lead to
hypersensitivity pneumo-nitis, an inflammation of the alveoli (air sacs) within
the lungs.
Second, mould produces various volatile
organic compounds (VOCs), such as alcohols and ketones, which are known
irritants—and responsible for that characteristic musty odour. Headaches,
dizziness, fatigue and other systemic effects may result from this type of
exposure.
Third, certain species of mould produce
mycotoxins, natural organic compounds that initiate a toxic response. These
mycotoxins have been linked to immunosupression, skin irritation and even
pulmonary haemorrhage in infants (see box, page 20).
Last of all, some types of mould can cause
infectious diseases in those who have weakened immune systems (for example,
bone-marrow-trans-plant patients). Such infections can affect the skin, eyes,
lungs and other organs.
Living with mould
Although mould has been around for
centuries, mould-related health problems appear to have arisen only recently.
There are various explana-tions for this trend, and one of the most compelling
is the substantial worldwide increase in the use of air conditioning.
According to the head scientist at the
indoor environment department of the Lawrence Berkeley National Laboratory—part
of the US Depart-ment of Energy—in Berkeley, CA, more than 15 studies point to
a strong link between air conditioning and numerous respiratory symptoms.
Microbes thriving in air-conditioning systems, including mould and bacteria,
are probably contributing to the relationship (Environ Health Perspect, 2007;
115: A300–5).
Other factors that might also have an
impact include poorly built homes and an increase in the numbers of individuals
who have weak or stressed immune systems. Those who suffer from chronic
illness, the elderly and even pregnant women are among the groups that have
been identified as being potentially more vulnerable to exposures to mouldy
indoor spaces.
Yet, despite the mountain of research, a
number of gaps in the evidence remain to be filled, partic-ularly as regards
systemic effects. Still, as Bob Weinhold writes in his 2007 report, A Spreading
Concern: Inhalational Effects of Mold, many organizations around the world are
reaching the same conclusion: “Don’t mess with mould. If you can see it or
smell it—and especially if health problems are occurring—clean it out, throw it
out, or get out” (Environ Health Perspect, 2007; 115: A300–5).
Joanna Evans
Murderous mould?
In the 1990s, a series of reports
associated exposure to damp and mould (especially of the species Stachybotrys
chartarum, also known as S. atra) in homes in Cleveland, Ohio, with an outbreak
of acute idiopathic pulmonary haemorrhage in infants (AIPHI). This condition,
involving the rupture of capillaries in the lungs, refers to its sudden onset
in a previously healthy infant (see www.cdc.gov/mold/AIPHIcasedef.htm for more
information).
Following the deaths of a number of infants
as a result of this condition, an investigation by the US Centers for Disease
Control and Prevention (CDC) suggested that AIPHI was associated with major
household water damage over the six months prior to the illness, along with
increased levels of household mould, including the toxin-producing S. chartarum
(Environ Health Perspect, 1999; 107 Suppl 3: 495–9; JAMA, 2000; 283: 1951–3).
Although researchers have since concluded
that there is insufficient evidence to confirm that mould exposure is a cause
of AIPHI—mainly due to study limitations such as problems with data collection
and the methods used to assess exposure—additional reports from independent
sources and studies in animals have provided further evidence of plausibility
for such a causal connection (Pediatrics, 2006; 118: 2582–6).
Indeed, as the lungs in young infants are
growing rapidly, they may be particularly sensitive to toxin-containing mould
spores, which could lead to areas of capillary fragility. Coupled with other
stresses to the developing lungs such as from tobacco smoke—also found to be
present in most of the Cleveland infants’ homes—mould exposure could eventually
trigger lung haemorrhages (Environ Health Perspect, 1999; 107 Suppl 3: 495–9).
Mould prevention tips
Mould spores are ubiquitous in the
environment and it’s impossible to maintain a completely mould-free home.
However, the following will help to prevent spores from colonizing and growing.
- Keep
all materials and surfaces as clean and dry as possible
- For surfaces where
moisture frequently collects, clean them with a baking-soda solution one day
and with vinegar the next
- Fix
plumbing leaks and other water problems as soon as possible
- Increase
ventilation (run a fan or open a window) in damp-prone spaces such as bathrooms
- If condensation is
a problem, consider installing a dehumidifier to reduce the humidity, but be
sure to clean the device regularly
- Vent appliances
that produce moisture, such as clothes dryers and stoves, to the outside
wherever possible
- Open
cupboards and drawers regularly to allow air to circulate
- Remove or replace
carpets and upholstery that have been soaked and cannot be dried quickly
- Avoid using carpet
in moisture-prone rooms or spaces such as bathrooms and basements
- Cover
cold surfaces, such as cold-water pipes, with insulation
- If flooding occurs,
clean up and dry out your home promptly and thoroughly (preferably within 24–48
hours).
Vol. 20 05 August 2009