Friday, 9 September 2011

Hurricane Irene causes Explosion in Mould Counts

Hurricanes are of course associated with high winds and a lot of rain and flooding. Measurements of airborne mould levels in the outside air before and after Irene struck show mold at 100-fold normal levels, peaking at up to 10 000 spores per cubic metre.
The air indoors is also vulnerable to increases in mould as the hurricane pushes humidity levels up and of course causes physical damage allowing rain to enter many properties along with large scale flooding. Some water ingress is obvious and can be dealt with but other leaks could be hidden e.g. in wall spaces and under the floor and these can cause just as much damage. It is important to dry, clean and remediate as soon as possible.

Symptoms of problems caused by increases in airborne moulds are those of respiratory discomfort especially for those with pre-existing breathing problems such as asthma and bronchitis and of course allergies to moulds. After Hurricane Katrina had blown itself out and destroyed many thousands of homes in New Orleans in 2005 some people seemed to develop 'Katrina Cough' which was almost certainly caused by irritation caused by the large amount of airborne dust including moulds.
NB It follows that any people with a compromised immune system should take more care than most, avoiding the worse effected areas and using HEPA grade facemasks to avoid breathing in microrganisms.

There is also some evidence that exposed people's sensitivity to moulds was not hugely effected by Hurricane Katrina. Rabito et.al. tested the sensitivity of hundreds of residents of New Orleans for sensitivity to moulds in the months and years after Katrina. One third reported mould damage to their homes and continued to live there during remediation work so we would expect them to have been quite heavily exposed to airborne moulds - figures reported in this paper mention levels up to 500 000 spores per cubic metre of indoor air. However only 10% showed any sensitivity to moulds and this did not differ greatly from the sensitivity levels found in residents of undamaged homes. Mold sensitivity did not correlate with damage to homes or the level of mould in those homes.

Consequently: Are we imagining Katrina Cough?

The authors go on to admit that their study does not capture several groups of ill people e.g. those who are not responsive to mould will also probably have symptoms of respiratory irritation - these symptoms are might still be caused by moulds using a mechanism other than allergy.
They also admit that they could not check if the patients they tested were resident in New Orleans at the time the hurricane struck - so this study lacks precision. Likewise the study depended on people being able to afford to be tested and thus missed the least well off part of the population.
This was a rather 'rough & ready' study that did not show gross effects caused by high mould counts in indoor air, but its limitations do not allow it to rule out all health problems caused by moulds and other airborne irritants in contaminated homes, especially those of the poorest people in New Orleans.

We can probably expect similarities in the health problems experienced by people living in New Orleans  and those effected by Hurricane Irene and moulds may well play their part in causing them.

CDC recommendations for cleaning up in the aftermath of a Hurricane

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