October 20, 2005

Bleach treatment neutralizes mold allergens

NEW YORK (Reuters Health) - Treatment with household bleach
reduces the allergy-inducing ability of mold spores, a new
study shows.

Current efforts to remediate mold-contaminated buildings
require replacement of contaminated materials, Dr. John W.
Martyny of the National Jewish Medical and Research Center in
Denver and colleagues note in the Journal of Allergy and
Clinical immunology.

Also, the Environmental Protection Agency and many
investigators argue that killing mold is not enough to reduce
its allergenicity. Dilute sodium hypochlorite is known to kill
mold, but it is not clear if it reduces mold's ability to
produce allergic reactions.

Martyny and his team conducted the current study, funded by
the Clorox Co., to determine if diluted bleach would destroy
the ability of mold to produce an allergic response as well as
kill the organism. Several studies, they point out, have found
bleach can neutralize other types of household allergens, such
as dust mite and cockroach proteins.

The researchers grew Aspergillus fumigatus on samples of
three types of construction materials, as well as in solution.
The samples and cultures were then treated with dilute bleach;
Tilex, a cleaning product containing detergent and bleach; or
water only.

The researchers then evaluated the number of spores using
scanning electron microscopy and tested for viable mold. They
also checked treated samples for antigens using ELISA and skin
prick testing.

While bleach or Tilex treatment did not reduce the number
of spores, surface allergens were no longer detectable in the
treated samples. The surface of the spores treated with bleach
or Tilex also showed changes in appearance. After adding bleach
to the mold in aqueous solution, A. fumigatus allergens were no
longer detectable by ELISA.

Skin prick tests found bleach treatment eliminated a
response in five of eight mold-allergic individuals, while
Tilex treatment inhibited response in seven of eight.

Some authorities on mold contamination, as well as some
government agencies, recommend against treating fungi
contaminated surfaces with bleach solutions, given the concern
that substantial amounts of organic material may neutralize
their disinfectant capacities, Martyny and colleagues note.

"On the basis of the results of our study, sodium
hypochlorite-containing products should be reconsidered as one
of the tools in the remediation of mold-contaminated
buildings," the researchers conclude.

SOURCE: Journal of Allergy and Clinical Immunology,
September 2005.