Decontamination of Biohazards and Infectious Agents

Decontamination is any process that reduces biohazardous material (infectious agents, recombinant or synthetic nucleic acid molecules, human material, biological toxins, etc.) to an acceptable level, or one that is below the level necessary to cause infection. Acceptable levels will depend on the biohazardous material in question and the type of work being done. To select the proper decontamination procedure one must consider many factors including the biohazard's concentration and resistance to disinfectants, chemical compatibility with other materials present, surface being decontaminated, and hazards to humans, animals, and the environment associated with the disinfectant. Ineffective decontamination can provide a false sense of security and spread contamination. Acceptable decontamination procedures must be determined before work begins and must be included in the lab's Standard Operating Procedures (SOPs).

Note: All recombinant or synthetic nucleic acid molecule-containing waste, including Biosafety Level 1 material, must be decontaminated prior to disposal or disposed of as biohazard waste before being released from the laboratory. See attached Decontamination and Spill Clean-Up template. This template must be customized for each lab.

Chemical Disinfection

Chemical disinfection is highly effective when done correctly. Some biohazardous agents are more or less susceptible to certain disinfectants.

More Resistant Microorganisms Examples
Prions BSE, vCJD, scrapie
Bacterial Spores Bacillus, Geobacillus, Clostridium sp.
Protozoan Oocytes Cryptosporidium
Helminth Eggs Ascaris, Enterobius
Mycobacteria M. tuberculosis
Small non-enveloped viruses  Poliovirus, Parvoviruses, Papillomaviruses
Protozoan Cysts Giardia, Acathomoeba
Fungal Spores Aspergillus, Penicillium
Gram-negative Bacteria E. coli, Salmonella spp.
Vegetative Fungi & Algae Candida, Chlamydomonas
Vegetative Helminths & Protozoa Ascaris, Cryptosporidium, Giardia
Large non-enveloped viruses Adenoviruses, Rotaviruses
Gram-positive Bacteria Staphylococcus, Streptococcus, Enterococcus
Less Resistant Enveloped viruses HIV, Hepatitis B, Herpes Simplex Virus

Choosing a Chemical Disinfectant

The effectiveness of chemical disinfectants will depend on the type of biohazardous material involved. Some chemical disinfectants can pose health hazardous and cause corrosion to surfaces. The goal is to choose a disinfectant that is highly effective for the biohazardous agent yet poses minimal risks to human health and of damage to surfaces and equipment.   

Advantages/Disadvantages of Common Disinfectants

Type Tips for Use Advantages Disadvantages
Chlorine Compounds -Dilute household bleach 1:9 (v/v) with water (10% bleach solution); make fresh monthly.
-Store diluted solutions in sealed container that is protected from light. 
-For spill cleanup and to wipe down work surfaces.
-FINAL concentration of 10% bleach used for liquid infectious waste. 
-Fisher Scientific supplies Fisherbrand* Bleach Solution Dispenser. It is a unique, two-bottle design and fixed-ratio trigger sprayer automatically mixes concentrated bleach with tap water. Cat. No. 23-640-127.
-Relatively nontoxic 
-Low cost 
-Effective with detergents 
-Fast acting 
-Broad spectrum effectiveness

-Inactivated by organic material such as blood
-Do not use at less than 1:9 (v/v) dilution 
-Strong oxidizer; corrosive 
-Irritates mucus membranes, eyes, skin 
-No residual activity on surfaces
-Can damage clothing
-Incompatible with quats 
-Produces toxic chlorine gas if mixed with acids or ammonia compounds
-Can't be used to disinfect radioactive iodine.

Alcohols -Dilute to 70% in water, (loses effectiveness at concentrations above 90%)
-Use to clean instruments and wipe down interior of Biological Safety Cabinets
-Use as topical antiseptic on intact skin
-Non-corrosive 
-Effective with detergent

-Can have reduced effectiveness in organic material; does not penetrate organic material
-Flammable
-No residual activity and limited effective exposure time due to high rate of evaporation

Phenolics -Dilute according to manufacturer's instructions
-Commonly used to clean walls, floors, etc. 
-Useful in areas where organic matter cannot always be removed; such as animal areas
-Good effectiveness with organic material 
-Effective with detergent 
-Has some residual effectiveness
-Toxicity varies with specific compound; can be absorbed through skin
-May cause chemical sensitization 
-Some formulations may have unpleasant odor 
-Corrosive 
-Skin irritant 
-Not effective against spores
Quanternary Ammonium Compounds—QUATS (cationic detergents) -Dilute according to manufacturer's instructions 
-Surfaces must be rinsed free of anionic soap or detergents before use 
-Commonly used to clean walls, floors, etc.
-Strong surface activity 
-Low toxicity 
-Non-corrosive 
-Effective over wide pH range
-Easily inactivated by organic materials, anionic detergents, and salts of metals in water (hard water) 
-Skin irritant

Effectiveness of Chemical Disinfectants on Biohazardous Agents

Chlorine Compounds Alcohols Phenolics Quats
Bacteria Very good Good Good Good for gram positive
Enveloped Viruses Very good Good Good  Good
Non-Enveloped Virusus Very good Fair** Fair** Not effective
Fungi Good Fair Good Fair
Bacterial Spores Good with high concentration Not Effective Not Effective Not Effective
Protozoal Parasites* Moderate with high concentration and long contact time (hours) Not Effective Not Effective Fair (some quats at high concentration)
***Biologically-Derived Toxins Concentration dependent Not Effective Not Effective Not Effective

*hydrogen peroxide most effective
**check disinfectant susceptibility for individual virus
***For information, see the Biologically-Derived Toxins web page.

Gas or Vapor Decontamination

Is useful when contamination issues are persistent or when there is a need to decontaminate an entire space. More information on the types of chemicals used in this process can be found in Appendix B of the BMBL. If you are experiencing contamination issues, please contact BOHD for further guidance at (612) 626-6002.

Biosafety cabinets must be professionally gas and vapor decontaminated prior to removal from use or being sent to ReUse. For more information, please see the BSC Certification and Maintenance web page.