New Study Proves Chlorine Bleach Kills Household Mold, Neutralizes Mold Allergen

UA News Services
March 24, 2004

Today at the American Academy of Allergy Asthma & Immunology's (AAAAI) 60th Annual meeting, Kelly Reynolds, a research scientist at the University of Arizona, announced the results of a new study that proves, for the first time, a chlorine bleach solution not only effectively kills mold but also neutralizes the indoor mold allergen. The study, funded by a grant from The Clorox Company, also found mold spores, a common trigger for allergies in America, to be present in 100 percent of the homes surveyed.

When sensitive individuals are exposed to allergens, such as mold spores, by either direct contact or inhalation, allergy and asthma symptoms may result. Some of these symptoms may include sinus congestion, coughing, upper respiratory distress, chronic headaches and flu-like symptoms. In fact, mold spores are suspected in the tripling of the asthma rate in the past 20 years and have been blamed by a 1999 Mayo Clinic Study for nearly all of the chronic sinus infections afflicting 37 million Americans.

The primary cause of allergic responses from exposure to mold can be attributed to surface allergens. These allergens become a problem when they become airborne and contaminate indoor air quality. The study found that low concentrations of chlorine bleach, such as those common to commercial household products certified to kill mold and mildew, were proven to be effective at not only killing the mold spores, but also denaturing, or neutralizing, the surface allergen, making it essentially unable to produce an immune response in sensitive individuals.

"Remaining fragments of dead mold can linger indoors long after the mold spores have been inactivated, and can be as harmful as live mold," said Kelly Reynolds, lead investigator for the study from the University of Arizona. "The study results confirm that denaturing the mold spores with a dilute chlorine bleach solution appears to be the most effective and efficient way to reduce mold allergen on hard surfaces."

Molds can be classified as either the mycotoxin producing molds such as Penicillium and Stachybotrys and the non-toxic molds such as Trichophyton. While the toxicities differ, all mold spores contain allergens, which according to the Asthma and Allergy Foundation of America (AAFA), can aggravate symptoms of both allergies and asthma.

The University of Arizona study yielded 1,330 mold samples and evaluated the growth rate and distribution of household mold on indoor surfaces in 160 homes in seven geographical regions. The regions where sites were frequently positive for fungal counts include the far west (San Francisco), Southwest (Tucson, Dallas), Midwest (Chicago), Southeast (Atlanta, Tampa, Fla.), and Northeast (New York) regions of the United States.

The study, which also looked at consumer perceptions towards mold, demonstrated that mold is far more pervasive in the home than people believe. While consumers understand that mold is a health concern, they are confused with the extent of the problem in their homes, with just 17 percent believing mold is an issue inside their own homes. Significant confusion also exists with the best way to effectively treat the issue.

The abstract for this study, "Efficacy of Sodium Hypochlorite Disinfectant on the Viability and Allergenic Properties of Household Mold," (abstract 617) was published in the February issue of the Journal of Allergy & Clinical Immunology.


Resources for the media

Kelly Reynolds
University of Arizona
(520) 626-2309
Adrienne Hymes
CLOROX Company
(310) 566-2292