Sodium hypochlorite inhibits viability and allergenicity of mold on building materials

Abstract

RATIONALE: Mold remediation often requires costly replacement of contaminated building materials. Dilute sodium hypochlorite disinfectants kill mold and are practical to use, however whether they also inhibit the allergenicity of viable and nonviable mold is unknown. We tested the hypothesis that sodium hypochlorite-containing spray products kill Aspergillus fumigatus(Af) and inhibit in vitro antigenicity and in vivo allergenicity. METHODS:Af was grown on 3 construction materials and in solution. Two sodium hypochlorite-containing products (diluted household bleach and Tilex®) were added to mold in solution and sprayed on building materials, and compared to untreated controls. After drying the boards, surface mold and associated debris were mechanically removed. Conidia in the extracted board materials were quantified by light microscopy, examined by scanning electron microscopy (SEM), and cultured for viable mold. Extracts were tested for Af antigenicity by ELISA, and for allergenicity by prick skin testing individuals with Af allergy. The study was approved by the IRB. RESULTS: Sodium hypochlorite solutions killed Af in solution and on building materials, with loss of surface structures by SEM. Both products inhibited Af antigenicity in solution and on building materials by ELISA. Skin testing demonstrated loss of skin test reactivity to the treated Af extracts in 5/6 subjects. Skin tests to sodium hypochlorite treated mold-contaminated OSB board were also inhibited in 2/3 sensitive individuals. CONCLUSIONS: Spray application of sodium hypochlorite-containing disinfectants onto mold-contaminated building materials kills mold, modifies conidial surface characteristics, and reduces mold antigenicity by ELISA, as confirmed by loss of skin reactivity in some individuals sensitive to Aspergillus fumigatus.