Wood floor decay

Jessie Micales jmicales at facstaff.wisc.edu
Wed Apr 30 22:34:20 EST 1997

>   A client's family has miscellaneous allergies, asthma.  They removed a
>basement wood floor that was all rotten.  A sample of wood was shown to
>me.  It is deteriorated to the point of dust.  Very few spores present in
>the wood, a few oval brown ones and many brown hyphae.  The air in the
>house is full of amber respirable fragments of the wood.  These fragments
>are identical tothose from solid wood sample:  cell walls.  These
>fragments have no activity with polarizers, are very friable.  Is this
>lignin without cellulose?  Is it allergenic due to mold metabolites?
>Jeff May
>jmhi at cybercom.net

The flooring was probably decayed by brown-rot fungi which remove the 
cellulose and hemicellulose from the wood but leave the lignin behind.  The 
material in  the air is probably the lignin residue from the wood cell walls.  I really 
don't know whether lignin residues could cause asthma and allergies.  I imagine 
that any fine particulate matter in the air would irritate the lungs, even if allergies 
(in the strict medical definition with IgE antibodies being formed) are not induced. 

Wood decay will only occur when wood becomes moist - usually above about 
25% moisture content. The fungi that cause wood decay are ubiquitous - they just 
wait around until the moisture content of wood becomes high enough for 
themi to grow.   Molds, which do not actually degrade wood cell walls, will also 
grow on the surface of wood when it becomes moist, so the allergy problems 
may arise from mold growing on the wood that is remaining in the basement.  
When your clienst replace the basement flooring, they should be certain that the 
moisture problem which caused the original decay is also removed, whether it is 
due to high humidity or a more specific point source such as leaky plumbing. 

Good luck.

Jessie A. Micales
Forest Products Laboratory
Madison, WI

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