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Based on Wiki-

http://en.wikipedia.org/wiki/Bleach

Excellent sources from governmental agencys and U of M's Department of Molecular.

Environmental impact

A Risk Assessment Report (RAR) conducted by the European Union on sodium hypochlorite conducted under Regulation EEC 793/93 concluded that this substance is safe for the environment in all its current, normal uses.[5] This is owed to its high reactivity and instability. Disappearance of hypochlorite is practically immediate in the natural aquatic environment, reaching in a short time concentration as low as 10-22 μg/L or less in all emission scenarios. In addition, it was found that while volatile chlorine species may be relevant in some indoor scenarios, they have negligible impact in open environmental conditions. Further, the role of hypochlorite pollution is assumed as negligible in soils.

Under conditions where sodium hypochlorite is improperly introduced to confined bodies of water (e.g., ponds, aquaria), bleach is toxic to fish and invertebrates. In confined spaces, fish will attempt to swim away from the source; in unconfined spaces, fish will readily escape the hazard.

http://ecb.jrc.ec.europa.eu/documents/Existing-Chemicals/RISK_ASSESSMENT/REPORT/sodiumhypochloritereport045.pdf

Antimicrobial efficacy

The broad-spectrum effectiveness of bleach, particularly sodium hypochlorite, owes to the nature of its chemical reactivity with microbes. Rather than acting in an inhibitory or toxic fashion in the manner of antibiotics, bleach quickly reacts with microbial cells to irreversibly denature and destroy many pathogens. Bleach, particularly sodium hypochlorite has been shown to react with a microbe's heat shock proteins, stimulating their role as intra-cellular chaperone and causing the bacteria to form into clumps (much like an egg that has been boiled) that will eventually die off.^[18] In some cases, bleach's base acidity compromises a bacterium's lipid membrane, a reaction similar to popping a balloon. The range of micro-organisms effectively killed by bleach (particularly sodium hypochlorite) is extensive, making it an extremely versatile disinfectant. The authors found that at low (micromolar) sodium hypochlorite levels, E. coli appear to be able to develop a defense mechanism that helps protect the bacterium, though the implications of this defense mechanism have not been fully investigated.^[18]

In response to infection, the human immune system will produce a strong oxidizer, hypochlorous acid, which is generated in activated neutrophils by myeloperoxidase-mediated peroxidation of chloride ions, and contributes to the destruction of bacteria.^[20][21][22]