Fungi that trigger allergies go under scrutiny

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http://www.nature.com/nsu/020408/020408-14.html

Mould monitored

Fungi that trigger allergies go under scrutiny.

15 April 2002

VIRGINIA GEWIN

Industry researchers have produced the largest study yet of airborne fungi

in US buildings. The fungal fingerprints may help scientists understand

their role in triggering allergies and other medical conditions.

Exposure to spores released by moulds is known to cause or worsen allergies

and trigger asthma episodes in sufferers. Spores enter buildings through air

ducts or open windows and can thrive in moist indoor conditions.

Shelton and his colleagues at the microbiology laboratory PathCon in

Norcross, Georgia, found Stachybotrys chartarum, a fungi thought to be

toxic, in 6% of indoor air and in 1% of the outdoor air from buildings

surveyed1.

" Finding some of these organisms is not uncommon, " says Shelton. He hopes

the study will provide baseline figures on the natural occurrence of fungi.

This could be of use in future studies on the health effects of particular

species.

" The list of identified fungal species is certainly a contribution to

science, " says , who studies allergens at Carleton University in

Canada. But he cautions against extrapolating detectable quantities of fungi

to an individual's exposure level.

Isolation of the mould does not necessarily indicate exposure to toxins that

they produce. It is not known whether spores produce toxins as the mould

does, or exactly what their health effects are, Shelton says.

Other rare health effects, such as bleeding lungs, have been attributed to

Stachybotrys chartarum - dubbed 'toxic mould'. But the link is disputed:

" There is no good evidence that mould in indoor environments is a

significant health problem other than being a potential cause of allergy and

asthma, " says Wasserman, allergist and spokesman for the American

Academy of Allergy, Asthma, and Immunology.

The controversy is, however, highlighting mould-related heath issues. " Mould

is replacing asbestos as the next issue for industrial hygiene, " says Henry

Lick, president of the American Industrial Hygiene Association.

Mould inspection

The PathCon lab received over 12,000 samples during air-quality

investigations in 1996 to 1998 - primarily from indoor samples of 1,700

buildings across the United States. This allowed it to provide detailed

lists and concentrations of fungi for individual regions, including moulds.

The survey measured culturable fungi, which are those that can be isolated

on specially designed laboratory media. Even though cultures provide the

best available measures, they are subject to limitations because not all

fungi can be grown in this way.

" The number of viable spores detected by this method is extremely low, " says

. Shelton counters that those that can't grow on culture aren't of

concern in buildings.

A National Academy of Sciences report in 2000, called Clearing the Air,

identified a need for a standardized method, other than culturable fungi, to

document exposure to fungal allergens.

The authors concede that this is primarily a descriptive study. However, it

provides profiles that would probably not come from any other source, given

the cost and logistics involved in collecting samples.

References

Shelton, B.G. Kirkland, K.H. Flanders, W.D. , G.K. Profiles of

airborne fungi in buildings and outdoor environments in the United States.

Applied and Environmental Microbiology, 68, 1743 - 1753, (2002).