Rationale and Considerations for Chlorine Use in Infection Control for Non- U.S. General Healthcare Settings

Environmental cleaning is only one of several recommended methods to reduce transmission of deadly germs among patients and healthcare personnel. Cleaning and disinfection, along with other infection control measures like hand hygiene and isolation precautions, are important ways to help stop the spread of ebolaviruses.1-8 This guidance primarily aims to address infection prevention and control practices in areas where chlorine solutions are primarily used for disinfection and antisepsis but are not standardized and can vary widely in concentration and source.

Description of Chlorine Use as a Disinfectant

Rationale for use

Chlorine solutions (Cl2, NaOCL, Ca[OCl]2, ClO) have been used extensively as disinfectants and antiseptics since the 1800s.11 Guidance documents on use of these compounds for environmental and healthcare infection control in the context of the Ebola preparedness and response in the United States have recently been published.9 Chlorine solutions are oxidative chemicals and have broad-spectrum activity against a wide variety of microorganisms, from viruses to protozoa.11-31

During Ebola responses, chlorine solutions of 0.5% (in the United States, this would generally be equivalent to a 1:10 dilution of household bleach) have been used for environmental surface disinfection, while a 0.05% solution has been used for hand hygiene. Nongovernmental organizations (NGOs) have typically provided hospitals and safe water programs with sodium dichloroisocyanurate (NaDCC), an EPA-approved pool chemical in the United States, for use in preparing disinfectant solutions as well as other chlorine-based products for disinfection use. There have also been some projects in Africa that have involved creating sodium hypochlorite electrolytically from brine solutions (primarily to disinfect drinking water, for example, CDC Safe Water, UNICEF Safe Water).

Bleach (sodium hypochlorite) solutions are produced in different concentrations in different parts of the world, and solution strength can vary between 2% and 12% NaOCl. (In comparison, most U.S. bleach products are currently 6%-6.15%, but can range from 2.5%-8.25%, depending on their intended use). Since there is such a wide variation in the strength of products available in some countries, it is strongly recommend that concentration of the chlorine product be evaluated prior to use.

Validation of chlorine products

When in doubt about a product, it is recommended that the chlorine concentration be determined using chemical analysis (for example, DPD [N,N-diethyl-p-phenylenediamine] color-change test kits, amperometric titration for chlorine residuals, commercially available test strips, or dip sticks). Reagent-grade water will also be needed to make 1:100 and 1:1000 dilutions of the prepared solution in order to conduct the testing.

Considerations for Chlorine Use

  • There are no published or manufacturer-based studies that have tested the effectiveness of chlorine products against ebolaviruses. However, chlorine solutions are known to be effective against a broad range of viruses.11-31
  • Wet contact time is the amount of time that a surface being disinfected should remain wet with disinfectant. Wet contact times for chlorine range from 2 minutes to 10 minutes depending on the microbe/virus. For wet contact times more than 10 minutes, chlorine solution or other acceptable disinfectant may have to be reapplied. When treating surfaces that are potentially contaminated with ebolaviruses and other bloodborne pathogens, allow a wet contact time of 10 minutes with a chlorine solution of 0.5% to 0.6%.
  • Chlorine solutions and other disinfectants are inactivated by the presence of organic matter (blood, other proteinaceous material, dirt), heavy metal ions, low temperature, or ultraviolet irradiation. Both WHO and CDC recommend cleaning with detergent and water before applying disinfectant. This will help prevent inactivation of the disinfectant by organic matter.8, 17, 32-33
  • Chlorine solutions should not be used for routine hand hygiene, as they will eventually damage the skin. Soap and water or alcohol-based hand rubs are preferred (see WHO Guideline on Hand Hygiene in Health Care, 2009 [PDF – 270 pages] and the Healthcare Infection Control Practices Advisory Committee’s Hand Hygiene in Healthcare Settings, 2002). Alcohol-based hand rubs (ABHR) offer benefits when compared with using soap and water in skin tolerance, compliance, and, especially when combined with glove use, overall effectiveness for a wide variety of healthcare pathogens. However, if hands become visibly soiled, use soap and water, not alcohol-based hand rubs3, 4.
  • Strong or mild chlorine solutions can be prepared from a number of different types of available products. To be effective, a solution with concentration that contains either 0.5%-0.6% (5000-6000 ppm) or 0.05-0.06% (500-600 ppm) of available chlorine, depending on its intended use, is required for infection control. Household bleach, which in the United States would be considered NaOCl (Pure bright, Clorox bleach, Clorox germicidal bleach, Ultra Clorox germicidal bleach, CCCP), is different from either Ca(OCl)2 (for example, HTH, chlorinated lime) or the locally prepared “bleach” products that are commonly found in some countries. Understanding which product is being used to make a solution is very important, as the amount of dilution needed for a product to be effective will vary.
  • Other considerations:
    • Chlorine solutions should be prepared fresh daily, as they are light sensitive.
    • Most chlorine products require the removal of organic soil prior to their use (removing bulk spill matter, cleaning prior to disinfecting).
    • Disinfection requires a wet contact time (amount of time the disinfectant is required to be left on the surface to be effective).
    • Chlorine odor does not necessarily indicate appropriate solution strength, since chlorine odor can be detected even at extremely low concentrations.
    • Chlorine solutions are corrosive and can pit metal and damage skin.

Preparing Bleach Solutions for Infection Control

  • When preparing chlorine-based solutions, remember that there is no one simple dilution that can be used to arrive at the working concentration. How much dilution is needed depends on what type of product is available. The following guidance can be used in the preparation of chlorine solutions.
    • Before use, consult the Safety Data Sheet (SDS) for the specific product being used, and refer to section 8 of its SDS for appropriate Personal Protective Equipment (PPE) to avoid chlorine exposure.
    • Make a 0.05% (approximately 500 ppm) chlorine solution by adding one tablespoon of HTH granules to 20 liters of clean water and stir for 10 seconds.
    • Make a 0.5% (5,250 ppm) hypochlorite solution by adding 10 heaping tablespoons of HTH granules to 20 liters of clean water. After mixing, wait 30 minutes to allow all of the Ca(OCl)2 granules to dissolve.
  • As an alternative, the following can be used to prepare chlorine solutions from either sodium hypochlorite (liquid) or calcium hypochlorite.
    • [% hypochlorite in liquid bleach as indicated on the label/% hypochlorite in the use solution] – 1 = total parts of water for each part of liquid bleach.
    • [% hypochlorite in use solution/% hypochlorite in the granules or powder as indicated on product label] x 1000 = amount in grams of granules to add to each liter of water.


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