The waters that humans drink, wash and bathe in are important to human existence and survival. Dozens of common, waterborne, viral and bacterial disease agents have the potential to infect and cause disease in humans and animals. Halogen-treated waters go a long way to assure human and animal health and safety. Two halogens - chlorine and bromine contribute significantly to this goal.
Bromine, Chlorine are Oxidizers
Bromine and chlorine are in the same group (VIIA = 7A) of the periodic table of elements and these halogens share similar properties. Each element is an oxidizer which means that atoms of these elements can accept electrons or hydrogens or both. As oxidizers each element can effect changes in other molecules such as proteins and carbohydrates. Molecular changes are sometimes visible - as with bleaching or chemical oxidations of colorful fabrics. Or the oxidation may be invisible until further tested - as when a microbe is killed.
Bleach is an example of a chlorine and oxygen compound. The chemical name and formula for bleach is sodium hypochlorite, NaOCl. In contrast with bleach, salt is simply sodium chloride (NaCl). Bleach can oxidize other molecules, salt cannot. When bleach is used on cotton fibers or proteins or carbohydrates it has the ability to significantly change and alter the molecular structure of those molecules.
Chlorination compounds are available from many commercial sources and include:
- Calcium hypochlorite, Ca(OCl)2; solid
- Sodium hypochlorite, NaOCl; liquid
- Potassium hypochlorite, KOCl.
- Chlorine, Cl2; gas.
According to the CDC the hypochlorous acid is the most active chlorine compound formed from each of the agents listed above. The use of some of the chlorine compounds above, as well as some brominated compounds, is valuable for the treatment and protection of pools, spas and hot tubs.
Chlorine, Bromine, Iodine Disinfectant Comparisons
Semmelweiss recommended that handwashing with chloride of lime — Ca(OCl)2 or calcium hypochlorite — must be used routinely by physicians attending to patients. Although Semmelweiss was ridiculed by some for this suggestion, the calcium hypochlorite handwashing practice dramatically lowered the infectious disease rates in the Vienna, Austria medical-maternity clinic.
Because halogens are such excellent oxidants they are employed regularly to inactivate and kill microbes. Drinking, washing and bathing waters are halogen-treated and halogen-protected waters. Disinfectants or sanitizers such as bromine and chlorine control and destroy potentially-pathogenic microbes such as Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa and Escherichia coli to name just a few important bacterial species. These oxidants change membrane and enzyme structure by oxidation. Oxidation inactivates these cell components and they are made dysfunctional. When these changes occur, the microbe cannot metabolize, becomes inactive, is unable to multiply, and soon dies.
Chlorine disinfects more quickly and better than bromine, but both halogens are very effective disinfectants as shown by Koski et al. in halogen disinfectant comparative studies.
Chlorine in Bleach and Disinfection and Sanitization
Bleach at a concentration of 5.25 to 6.25% aqueous is one of the least expensive and most readily available disinfectants. As a routine disinfectant for the treatment of laundy, hard surfaces at home and work, and for the emergency disinfection of water with bleach promotes human health and safety. The active form of bleach is hypochlorous acid. Here are listed some useful bleach dilutions recommended for different situations:
- clothes washing and laundering – 1/8 cup for every 2 gallons of wash water
- surface disinfection – 1/100 dilution of standard bleach
- emergency drinking water – 1/8 teaspoon (8 drops) of unscented standard bleach stirred into a gallon of water and set aside for 30 min to disinfect the water
If cleanliness and disinfectants are next to Godliness, then one might believe that the halogens are indeed a heavenly help.
Sources
CDC. Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008. Cdc.gov/hicpac/Disinfection_Sterilization/6_0disinfection.html. Accessed June 14, 2010.
EPA. Emergency Disinfection of Drinking Water. EPA.gov/ogwdw000/faq/emerg.html. Accessed, June 14, 2010.
Koski TA, Stuart LS, Ortenzio LF. "Comparison of chlorine, bromine, iodine as disinfectants for swimming pool water." Appl. Microbiol. 1966 Mar;14(2):276-9.
Donald Reinhardt - Think, read, write & live well always. DJR has a PhD in Biology/Microbiology & is a Fellow & Diplomate, ASM Amer Acad Micro.
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