Friday, 20 June 2008

Mould and flooded homes

Image from
There have been several incidents of extensive flooding of homes throughout the world over the last few years (UK), USA & Bangladesh.
In this article Prof. H. James Wedner of Washington State University discusses a major problem that follows flooding - mould.
The consequences of mould growth in homes and other buildings have been controversial for some time now, especially in the US where there are many legal arguements ongoing as residents try to establish that 'toxic mold' growing in damp homes has effected their health.

Prof Wedner asserts facts such as all mold is not toxic and that there has never been a case proven were breathing in fungal material in the home (i.e. spores) has been shown to be harmful to human health. Those cases that have been reported are for farm workers inhaling massive quantities of fungal material after encountering agricultural scale dust clouds.
There is no doubt that fungi can produce highly toxic substances (see the toxic metabolite listings here) and will do so in the home environment, especially after flooding. The contentious issue is whether or not enough fungal material could be breathed in as dust in the home environment to cause health problems due to mycotoxicosis - toxins are cleared from our bodies at a steady rate via our livers.

The assertion that toxicity has never been proved is potentially insufficient as little work has been reported in this area. One neglected area is of the effects of chronic cumulative exposure to low levels of mycotoxins - in a damp home this could well be a realistic scenario.

Johns Hopkins Hospital recently released a set of guidelines based on a well researched review entitled 'The medical effects of mold exposure'. One assertion made was

"It is highly unlikely that you could inhale enough mold in your home or office to receive a toxic dose".

While for most cases that is probably true, the review that that assertion is based on claims that mycotoxins

"are not cumulative toxins, having half-lives ranging from hours to days depending on the specific mycotoxin."

Again this is largely true but there are papers that suggest that some mycotoxins and/or their health effects can accumulate in the body - in humans in Asia and humans in USA and in laboratory animals.

The paper referenced in that review clearly states at the bottom of page 125 that studies on cumulative exposure to toxins at a level that might be reached in human exposure have not been done. Considering that exposure might include exposure to multiple toxins which might interract it is worthwhile underlining that the statement made by Johns Hopkins and the review is that it is 'improbable' that there are no health effects arising from breathing in the air in damp homes - and not 'impossible'.

Some health effects of molds in the air are well known - allergies are well established for example and Prof Wedner talks about these at length. There is therefore plenty of reason to ensure homes are kept free of moulds and no person should be compelled to live in a mouldy environment. The debate continues in the scientific media (2006). Other causes of health problems in damp houses are also investigated.

The Aspergillus Website has several useful resources on indoor air quality here.

NOTE: it has been brought to my attention that the paper mentioned above entitled 'The medical effects of mold exposure' has been the centre of much debate centred partly around the criticisms I made above. Several doctors strongly refute several statements in that paper - I have added links to the debate to the top of the original paper.


Anonymous said...

As an Industrial Hygienist and a realist, I have inspected over 1000 properties where the occupants have complained about exacerbated allergies and increased incidents of asthma and sinusitis. The vast majority of the people I have met are reasonable, rational and educated. Where indoor fungal levels are highly elevated and the species are identifed as Aspergillus and/or Atlernaria the corrolation between symptoms and abundant fungi is clear and compelling. Most important is when the property is cleaned and the symptoms abate. Pyschsomatic? I think not.

Website Team said...

Hi There and thanks for your comment

These are exactly the kind of illnesses that seem to be well established - I don't think there can be much debate that allergies and asthma can be aggravated by air borne fungi as the floating particles are well established to be allergens.

The controversial area is mycotoxicity and that has little to do with asthma and allergy.

Peter said...

If your home has been flooded and has been closed up for several days, presume your home has been contaminated with mould which can cause health risks for your family.People with asthma, allergies, or other breathing conditions may be more sensitive to mold.

Anonymous said...

When reviewing any comments from Dr. H. James Wedner, you need to be aware that he is an insurance industry defense expert.

Contact us at