If we just stated that bleach has the ability to kill microorganisms, then why isn't it a good choice for cleaning moldy surfaces? There are at least two answers to this question.  

 

First, bleach will chemically react with both the mold and all of the other organic material that may be present. If excess debris isn't first removed from the surface, or if the material upon which the mold is growing is organic in nature, the active ingredients in a bleach solution may be consumed long before the mold is killed.  

 

Second, bleach is not a detergent - it does not effectively remove foreign material from a surface. The primary goal in any mold clean-up effort is to physically remove the mold from the surface, not just kill it.  

 

Even if a bleach solution were to kill the mold, a dead mold spore may still elicit adverse health effects. A good analogy is peanut allergies. For certain persons, peanuts can be severely allergenic - in fact, life-threatening - even after the killing (roasting) process. Although a recent study by a recognized industry expert suggests that bleach can diminish the allergenic properties of certain molds, independent confirming studies are lacking.

It is important to remember that chlorine bleach is a strong skin, eye and respiratory irritant. Bleach should never be applied with a spray bottle or other type of aerosolizing device without adequate eye and respiratory protection. Also, the potentially toxic properties of bleach solutions cannot be overlooked. The use of bleach in combination with certain household cleaners can cause the release of chlorine gas, and recent research suggests that carcinogenic chlorinated compounds (chloroform, carbon tetrachloride) are commonly released.

When dealing with a mold problem, cleaning and removing the fungal growth is far more important than trying to kill it. For most non-porous and semi-porous materials, the most effective method of cleaning up mold is to use a detergent solution, followed by a clear water rinse. If desired, bleach may be used afterwards to decolorize some of the enzyme staining caused by the mold.

Finally, it's important to note that some well-known household bleaches, like Clorox® and Hi-Lex®, are registered with the U.S. EPA as pesticides. Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), it is a violation of Federal law to use these products in a manner inconsistent with their labeling. The "labeling" submitted to the EPA as well as the label on the bottle clearly state that these products should be used only after cleaning the affected surface. While the FIFRA regulations do not apply to the use of pesticides by homeowners in their own residences, they do apply to cleaning contractors. 

 

In our experience, for cleaning limited areas of mold on non-porous and semi-porous surfaces, it is best to use a detergent solution and a generous helping of elbow grease. And, if the area of surfaces impacted by mold growth exceeds the EPA's designation of a "small project" (i.e., >10 square feet) we recommend that you call an experienced environmental consultant for appropriate guidance. **This copyrighted information originally appeared in the 2008 issue of the "IAQ Brief" series published by Michaels Engineering Inc.., and is reproduced herein with the permission of the authors ** Thank You