How much mould is in your home?

Surely your bathroom is fungus-free once you've wiped the mould off the tiles? Not according to a study by French scientists in the Royal Society of Chemistry's Journal of Environmental Monitoring. They report that almost one in five rooms studied with no visible mould was in fact "highly contaminated" by fungus which could aggravate conditions such as asthma.

The study also found that bedrooms and living rooms were no less contaminated than bathrooms and kitchens - "hidden" fungus was not only airborne but found in carpets and soft furnishings, and behind wallpaper, and was often colourless and odourless.

When assessing a building's level of contamination, many authorities rely on trained investigators to see or smell the fungus - Sandrine Roussel, lead author of the article, and collaborators say this is not enough. By completing questionnaires and sampling the air in hundreds of homes in France, they found that what you see is not always what you get.

"Nowadays, no one would agree to live in housing which presents any risks towards lead or carbon monoxide. Tomorrow, moulds and other chemical substances will probably follow," says Roussel.

Mould in the home is not just unsightly and indicative of poor hygiene standards; it is known to aggravate a range of medical conditions, such as asthma, rhinitis and hypersensitivity pneumonitis. This study set out to establish if more could be done to identify fungus as exacerbating these complaints.

Surprisingly, the study found that factors commonly held to increase mould contamination had relatively little effect. The age of the building, presence of pets and even outdoor and indoor temperature had little bearing on fungus concentration.

As for airborne fungi, it made little or no difference if the room was regularly used to dry clothes, or contained indoor plants - factors that public health inspectors had previously highlighted as key issues.

The researchers found that significant factors in levels of contamination were structure, such as lack of ventilation or a ground floor apartment, or accidental damage, such as water damage.

References

Roussel et al., J. Environ. Monit., 2008, DOI: 10.1039/b718909e