Chemical interactions
Hypochlorite and chlorine are in equilibrium in water; the position of the equilibrium is pH dependent and low pH (acidic) favors chlorine,[3]
Cl2 + H2O H+ + Cl- + HClO
Chlorine is a respiratory irritant that attacks mucous membranes and burns the skin. As little as 3.53 ppm can be detected as an odor, and 1000 ppm is likely to be fatal after a few deep breaths. Exposure to chlorine has been limited to 0.5 ppm (8-hour time-weighted average—38 hour week) by OSHA in the U.S.[4]
Sodium hypochlorite and ammonia react to form a number of products, depending on the temperature, concentration, and how they are mixed. [5]. The main reaction is chlorination of ammonia, first giving chloramine (NH2Cl), then dichloramine (NHCl2) and finally nitrogen trichloride (NCl3). These materials are very irritating to eyes and lungs and are toxic above certain concentrations. Lastly there is bleach containing sodium perchlorate.
NH3 + NaOCl --> NaOH + NH2Cl
NH2Cl + NaOCl --> NaOH + NHCl2
NHCl2 + NaOCl --> NaOH + NCl3
Additional reactions produce hydrazine, in a variation of the Olin Raschig process.
NH3 + NH2Cl + NaOH --> N2H4 + NaCl + H2O
The hydrazine generated can further react with the monochloramine in an exothermic reaction:[3]
2 NH2Cl + N2H4 --> 2 NH4Cl + N2
Industrial bleaching agents can also be sources of concern. For example, the use of elemental chlorine in the bleaching of wood pulp produces organochlorines, persistent organic pollutants, including dioxins. According to an industry group, the use of chlorine dioxide in these processes has reduced the dioxin generation to under detectable levels.[6] However, respiratory risk from chlorine and highly toxic chlorinated byproducts still exists.
A recent European study indicated that sodium hypochlorite and organic chemicals (e.g., surfactants, fragrances) contained in several household cleaning products can react to generate chlorinated volatile organic compounds (VOCs).[7] These chlorinated compounds are emitted during cleaning applications, some of which are toxic and probable human carcinogens. The study showed that indoor air concentrations significantly increase (8-52 times for chloroform and 1-1170 times for carbon tetrachloride, respectively, above baseline quantities in the household) during the use of bleach containing products. The increase in chlorinated volatile organic compound concentrations was the lowest for plain bleach and the highest for the products in the form of “thick liquid and gel”. The significant increases observed in indoor air concentrations of several chlorinated VOCs (especially carbon tetrachloride and chloroform) indicate that the bleach use may be a source that could be important in terms of inhalation exposure to these compounds. While the authors suggested that using these cleaning products may significantly increase the cancer risk [8], this conclusion appears to be hypothetical:
The highest level cited for concentration of carbon tetrachloride (seemingly of highest concern) is 459 micrograms per cubic meter, translating to 0.073 ppm (part per million), or 73 ppb (part per billion). The OSHA-allowable time-weighted average concentration over an eight-hour period is 10 ppm [9], almost 140 times higher;
The OSHA highest allowable peak concentration (5 minute exposure for five minutes in a 4-hour period) is 200 ppm[9], twice as high as the reported highest peak level (from the headspace of a bottle of a sample of bleach plus detergent).
Further studies of the use of these products and other possible exposure routes (i.e., dermal) may reveal other risks. Though the author further cited ozone depletion greenhouse effects for these gases, the very low amount of such gases, generated as prescribed, should minimize their contribution relative to other sources.
Hypochlorite and chlorine are in equilibrium in water; the position of the equilibrium is pH dependent and low pH (acidic) favors chlorine,[3]
Cl2 + H2O H+ + Cl- + HClO
Chlorine is a respiratory irritant that attacks mucous membranes and burns the skin. As little as 3.53 ppm can be detected as an odor, and 1000 ppm is likely to be fatal after a few deep breaths. Exposure to chlorine has been limited to 0.5 ppm (8-hour time-weighted average—38 hour week) by OSHA in the U.S.[4]
Sodium hypochlorite and ammonia react to form a number of products, depending on the temperature, concentration, and how they are mixed. [5]. The main reaction is chlorination of ammonia, first giving chloramine (NH2Cl), then dichloramine (NHCl2) and finally nitrogen trichloride (NCl3). These materials are very irritating to eyes and lungs and are toxic above certain concentrations. Lastly there is bleach containing sodium perchlorate.
NH3 + NaOCl --> NaOH + NH2Cl
NH2Cl + NaOCl --> NaOH + NHCl2
NHCl2 + NaOCl --> NaOH + NCl3
Additional reactions produce hydrazine, in a variation of the Olin Raschig process.
NH3 + NH2Cl + NaOH --> N2H4 + NaCl + H2O
The hydrazine generated can further react with the monochloramine in an exothermic reaction:[3]
2 NH2Cl + N2H4 --> 2 NH4Cl + N2
Industrial bleaching agents can also be sources of concern. For example, the use of elemental chlorine in the bleaching of wood pulp produces organochlorines, persistent organic pollutants, including dioxins. According to an industry group, the use of chlorine dioxide in these processes has reduced the dioxin generation to under detectable levels.[6] However, respiratory risk from chlorine and highly toxic chlorinated byproducts still exists.
A recent European study indicated that sodium hypochlorite and organic chemicals (e.g., surfactants, fragrances) contained in several household cleaning products can react to generate chlorinated volatile organic compounds (VOCs).[7] These chlorinated compounds are emitted during cleaning applications, some of which are toxic and probable human carcinogens. The study showed that indoor air concentrations significantly increase (8-52 times for chloroform and 1-1170 times for carbon tetrachloride, respectively, above baseline quantities in the household) during the use of bleach containing products. The increase in chlorinated volatile organic compound concentrations was the lowest for plain bleach and the highest for the products in the form of “thick liquid and gel”. The significant increases observed in indoor air concentrations of several chlorinated VOCs (especially carbon tetrachloride and chloroform) indicate that the bleach use may be a source that could be important in terms of inhalation exposure to these compounds. While the authors suggested that using these cleaning products may significantly increase the cancer risk [8], this conclusion appears to be hypothetical:
The highest level cited for concentration of carbon tetrachloride (seemingly of highest concern) is 459 micrograms per cubic meter, translating to 0.073 ppm (part per million), or 73 ppb (part per billion). The OSHA-allowable time-weighted average concentration over an eight-hour period is 10 ppm [9], almost 140 times higher;
The OSHA highest allowable peak concentration (5 minute exposure for five minutes in a 4-hour period) is 200 ppm[9], twice as high as the reported highest peak level (from the headspace of a bottle of a sample of bleach plus detergent).
Further studies of the use of these products and other possible exposure routes (i.e., dermal) may reveal other risks. Though the author further cited ozone depletion greenhouse effects for these gases, the very low amount of such gases, generated as prescribed, should minimize their contribution relative to other sources.
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