Chemical Disinfectants

Following is a list of commonly used disinfectants. If a chemical disinfectant is required, please be sure to choose a compound which is active against the agent you are using. This list is not complete and you are urged to contact Environmental Health and Safety should additional information be required.

I. Chlorine

This halogen is a universal decontaminant active against all microorganisms, including bacterial spores. Chlorine combines with protein and rapidly decreases in concentration in its presence. Free, available chlorine is the active element. It is a strong oxidizing agent, corrosive to metals. Chlorine solutions will gradually lose strength so that fresh solutions must be prepared frequently. Sodium hypochlorite is usually used as a base for chlorine decontaminants. An excellent decontaminant can be prepared from household or laundry bleach. These bleaches, usually contain 5.25% available chlorine or 52,500 ppm. If diluted 1:100, the solution will contain 525 ppm of available chlorine and if a nonionic detergent such as Naccanol is added in a concentration of about 0.7% a very good decontaminant is created. These are recommended for certain disinfecting procedures provided the available chlorine needed is considered. Low concentrations of available chlorine (50 to 500 ppm) are active against vegetative bacteria and most viruses. For bacterial spores, concentrations of approximately 2500 ppm are needed.

II. Iodine

The characteristics of chlorine and iodine are similar. One of the most popular groups of decontaminants used in the oncologic laboratory is the iodophors and Wescodyne is perhaps the most popular. The range of dilution of Wescodyne recommended by the manufacturer is 1 oz. in 5 gal. (28.35gr. in 18.9 L) of water giving 75 ppm of available iodine, to 3 oz. in 5 gal. (85 gr. in 18.9 L) giving 75 ppm. At 75 ppm, the concentration of free iodine is 0.0075%. This small amount can be rapidly taken up by any extraneous protein present. Clean surfaces or clear water can be effectively treated by 75 ppm available iodine, but difficulties may be experienced if any appreciable amount of protein is present. For bacterial spores, a dilution of 1:40 is recommended by the manufacturer giving 750 ppm.

For washing the hands, it is recommended that Wescodyne be diluted 1:10 or 10% in 50% ethyl alcohol (a reasonably good decontaminant itself) which will give 1600 ppm of available iodine, at which concentrations relatively rapid inactivation of any and all microorganisms will occur. Iodophors have a built-in indicator. If the solution is brown or yellow, it is still active. Iodophors are relatively harmless to man. They can be readily inactivated and their stains can be removed easily with solutions of Na2S2O3 (sodium thiosulfate).

III. Formaldehyde-Alcohol

Solutions of 8% formalin in 70% alcohol are considered very good for disinfection purposes because of their effectiveness against vegetative bacteria, spores and viruses. For many applications this is the disinfectant of choice. However, it should be stressed that formaldehyde is a known irritant, sensitizer and suspect carcinogen. Therefore, its use should be restricted to those applications which minimize exposure potential.

IV. Alcohols

In concentrations of 70 to 95% alcoholic solutions are good general-use disinfectants, but they exhibit no activity against bacterial spores.