Aerosolized sodium hypochlorite inhibits viability and allergenicity of mold on building materials.

Background: Commercial and residential buildings can become contaminated with molds, which may trigger allergic disorders. Mold remediation efforts may require costly replacement of mold-contaminated building materials. Disinfectants that contain dilute sodium hypochlorite can kill mold and are practical to use. Whether they also inhibit mold allergy symptoms is unknown.

Objective: We tested the hypothesis that sodium hypochlorite-containing spray products kill Aspergillus fumigatus and inhibit A fumigatus allergens.

Methods: A fumigatus was grown on 3 common building construction materials, as well as in solution by conventional laboratory methods. Two sodium hypochlorite-containing household products (diluted bleach and Tilex) were sprayed on the mold-contaminated materials or added to mold in solution and compared with untreated controls. Surface mold and associated debris were mechanically removed from treated and untreated boards. Conidia in the extracted board materials were quantified by light microscopy, examined for morphologic changes by scanning electron microscopy, and cultured for viable mold. Extracts were tested for A fumigatus antigen by ELISA, and for A fumigatus allergen by skin prick testing using extracts prepared from both the boards and the cultured solutions.

Results: Both sodium hypochlorite disinfectants killed A fumigatus in solution and on mold-contaminated building materials. Light microscopy and scanning electron microscopy demonstrated changes to the conidial surface. Both dilute bleach and Tilex inhibited A fumigatus recognition by ELISA. Skin testing supported the results of the ELISAs and demonstrated loss of skin test reactivity to the sodium hypochlorite-treated mold solutions in most of the subjects. Of the 4 individuals who had a positive skin test result to mold grown on oriented strand board building material, 3 no longer reacted to extracts from bleach-treated boards.

Conclusion: Spray application of sodium hypochlorite-containing disinfectants onto mold-contaminated building material kills A fumigatus, modifies the surface characteristics of A fumigatus conidia, reduces recognition of A fumigatus mold by ELISA, and results in loss of skin test reactivity to the treated mold in individuals allergic to A fumigatus.