Mycotoxins and Bleach

When dealing with mold, mold contamination and clean up, inevitably a couple of terms will enter the conversation: mycotoxin and bleach.  Consultants probably deal with this situation just as much if not more than we do at the lab.  But any IAQ professional who has presented a client a lab report with positive mold results, has had this same conversation over and over.   How many times have you heard  “well, I’m just going to  … or can’t I just pour some bleach on it?”    Too many times to count right?     

First we want to make it clear that we are not saying that all mold produces toxins, just because a mold report is issued with mold detected, one can not assume there are mold toxins present.  This tid bit is nothing new for the mold professionals however, it needs to be said just in case a non mold professional reads our blog(if this is you, hello, and thank you for reading!)     

I thought it might be interesting to compare the MSDS sheets for a mycotoxin and bleach.  Then next time the subject comes up, maybe you will have taken away a factoid or two to pepper your answer with.     

Let’s refresh our vocabularies with a couple basic definitions.   Mycotoxin is a toxin or poison that is produced by fungi.  While, mycotoxin is broad term encompassing many individual toxins produced by fungi, for comparison sake we have selected one of the more common types, aflatoxin. The topic of mycotoxins is discussed in greater detail in a separate blog post called Mycotoxins: a closer look     

Factoid: At least 13 different types of aflatoxin are produced in nature with aflatoxin B1 considered as the most toxic(6).     

I think we all are familiar with bleach, most of us have the common cleaning agent in our homes, but by definition according to Encarta, bleach is a chemical that removes or whitens color or staining and also cleans and disinfects.     






Below I created a chart that shows the health effects of both Mycotoxin (Aflatoxin) and Bleach, and placed them side by side for ease of comparison. 


                                                   Mycotoxin (aflatoxin)                                                                     Bleach    

Danger May be fatal if inhaled, absorbed through the skin or swallowed. Very toxic by inhalation, in contactwith skin and if swallowed. Cancer hazard.  Corrosive. Causes eye and skin burns. Causes digestive tract burns. Harmful if inhaled. Causesrespiratory tract irritation. May cause methemoglobinemia. 
Target organ Liver. Blood.
Eye May cause eye irritation. May cause irreversible eye injury. Contact with liquid is corrosive to the eyes and causes severe burns.
Skin May cause skin irritation. May be fatal if absorbed through the skin. Toxic in contact with skin. Causes skin burns.
Ingestion May be fatal if swallowed. May cause irritation of the digestive tract. Toxic if swallowed May cause methemoglobinemia, cyanosis (bluish discoloration of skin due to deficient oxygenation ofthe blood), convulsions, and death. Causes severe digestive tract burns with abdominal pain, vomiting, and  possible death. Methemoglobinemia is characterized by dizziness, drowsiness, headache, shortness of breath, cyanosis (bluish discoloration of skin due to deficient oxygenation of the blood), rapid heart rate and chocolatebrown colored blood.
Inhalation May be fatal if inhaled. May cause respiratory tract irritation. Toxic if inhaled. Harmful if inhaled. Causes severe irritation of upper respiratory tract with coughing, burns, breathingdifficulty, and possible coma. May cause pulmonary edema and severe respiratory disturbances. 
Chronic May cause cancer in humans. Chronic inhalation and ingestion may cause effects similar to those of acute inhalation and ingestion

Clearly both are serious chemicals and should be  treated as such.  In case you haven’t read what OSHA or the EPA suggests continue reading:     

OHSA(3): Use of Biocides    



The use of a biocide, such as chlorine bleach, is not recommended as a routine practice during mold remediation, although there may be instances where professional judgment may indicate its use (for example, when immuno-compromised individuals are present). In most cases, it is not possible or desirable to sterilize an area, as a background level of mold spores comparable to the level in outside air will persist. However, the spores in the ambient air will not cause further problems if the moisture level in the building has been corrected. (3) 


Biocides are toxic to animals and humans, as well as to mold. If you choose to use disinfectants or biocides, always ventilate the area, using outside air if possible, and exhaust the air to the outdoors. When using fans, take care not to extend the zone of contamination by distributing mold spores to a previously unaffected area. Never mix chlorine bleach solution with other cleaning solutions or detergents that contain ammonia because this may produce highly toxic vapors and create a hazard to workers. (3)  


 Some biocides are considered pesticides, and some states require that only registered pesticide applicators apply these products in schools, commercial buildings, and homes. Make sure anyone applying a biocide is properly licensed where required. (3)   


 Fungicides are commonly applied to outdoor plants, soil, and grains as a powder or spray. Examples of fungicides include hexachlorobenzene, organomercurials, pentachlorophenol, phthalimides, and dithiocarbamates. (3)    
 Do not use fungicides developed for outdoor use in any indoor application, as they can be extremely toxic to animals and humans in an enclosed environment. (3)    
 When you use biocides as a disinfectant or a pesticide, or as a fungicide, you should use appropriate PPE, including respirators. Always, read and follow product label precautions. It is a violation of Federal (EPA) law to use a biocide in any manner inconsistent with its label direction.(3)    
Hard surface, porous flooring§ (Linoleum, ceramic tile, vinyl)
  • Vacuum or damp wipe with water and mild detergent and allow to dry; scrub if necessary.(4)
  • Check to make sure underflooring is dry; dry underflooring if necessary.(4)
Non-porous, hard surfaces
(Plastics, metals)
  • Vacuum or damp wipe with water and mild detergent and allow to dry; scrub if necessary.(4)



Notice how neither the EPA nor OSHA endorses the use of bleach.    


Please share or comment.  Thank you,   


 the moldlab staff    


5). Aldrich Catalog Handbook of Fine Chemicals, 1988-1989, pg.40     




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