| Compared to GA, peracetic acid (PAA) has similar or better biocidal efficacy. A contact time of 5 minutes is recommended for the destruction of vegetative bacteria and viruses (HBV, HIV); the sporicidal activity requires immersion for 10 minutes (for 0.35 PAA). A contact time of 10 or 15 minutes and a concentration >0.09 %. With respect to staff safety, PAA is claimed to cause less irritation than GA, and be safer for the environment. Adverse effects are strongly linked to the pH value of the solution - minimal effects are observed at a pH between 7.5 and 10.0. It would, however, seem unwise to state that PAA can be used safely without adequate ventilation or personal protective measures, especially in manual immersion methods. PAA has the ability to remove hardened material in biopsy channels resulting from use of GA, as demonstrated by surface spectroscopy. In its long history of use in the food industry and medicine, development of microorganism resistance has not been reported; its broad spectrum of activity suggests that microorganisms are unlikely to develop resistance to itOne of the chief disadvantages of PAA is that it is less stable than GA. The shelf-life of products containing PAA is 12-18 months, depending on storage conditions. Solutions with a longer shelf-life can be prepared at the customer site by chemical reaction immediately before the first use; once prepared the solution requires replacement every 24 hours. Used solution requires replacement every 1-7 days. The PAA concentration should be checked using the appropriate test kits which detect the minimal effective concentration against the complete range of expected pathogens. If diluted solutions are used, large volumes have to be stored. This can be avoided by using concentrated products. Further disadvantages of PAA are its vinegary odor and corrosive action, depending on the formulation. Both properties are strongly linked to the pH value, temperature, PAA concentration, and composition of the disinfectant (i.e. inclusion of anticorrosive agent, etc). Damage of flexible endoscopes has been reported after disinfection with some brands of PAA. The oxidizing ability of PAA may expose leaks in internal channels of the endoscope, especially if the endoscope was previously disinfected with GA. PAA also causes discoloration of endoscopes, but without any functional damage. There is concern about the effect of some PAA solutions on disinfection machines that contain polymer-based seals and brass components within the hydraulic circuit. Endoscope damage due to the use of PAA has also been reported in the US.
It should be noted that there are various brands of PAA available with variations in effectiveness and side-effects. There are also various labeling claims, depending on the brand of PAA.
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