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Friday, November 2, 2012

Disinfectant #9: Peracetic acid: Weak acid, Strong Disinfectant?

Peracetic acid (PAA) was first registered as a disinfectant in 1985 by the EPA. PAA is produced by combining acetic acid (vinegar) and hydrogen peroxide.  The result is a peroxide version of acetic acid (vinegar) that has a very distinctive and a pungent vinegary smell.  It is a weak acid compared to acetic acid but can be highly corrosive if not used at the appropriate dilutions. Peracetic acid is a versatile chemical that can be used in a variety of applications with its main use as a disinfectant product in food and beverage processing/producing plants due to the fact that it leaves no harmful residues and decomposes into harmless by-products.

As a cleaner, peracetic performs poorly as it lacks detergency properties.  As alluded to in previous blogs, you may wonder whether increasing the concentration of this acid would benefit its cleaning. The answer in short is: No. A higher concentration would not increase its cleaning abilities and in fact would lead to an increase in corrosiveness.
As a germicide, peracetic acid shows fairly strong efficacy against a broad spectrum of pathogens. Like many disinfectants, the temperature, pH and concentration all play a significant role in determining the antimicrobial properties. It is bactericidal at 10ppm, fungicidal at 30 ppm and virucidal at 400 ppm in a 5 minute contact time. Furthermore, it is sporicidal at concentrations of 3000 ppm. It is more effective at slightly higher temperatures and its germicidal activity increases at higher pH ranges. Combinations of PAA and hydrogen peroxide further boost the efficacy profile, as this blend can prevent the formation of biofilms on hard surfaces. The method by which PAA attacks pathogens is through the reaction with the cellular walls. This leads to breakdown of cell membranes and cellular death due to cell content leakage. An issue regarding PAA usage is its stability. In the presence of water, it breaks down quickly. This would have a direct affect on the viability of the product over time.

Peracetic acid’s safety profile can also be closely correlated to its concentration. The higher the concentration, the worse the safety profile is. For example, an in use solution of PAA of 5% has relatively low oral toxicity at this dilution. However, respiratory issues, including occupational asthma development associated with PAA have been reported. Further, it can strongly sensitize respiratory organs and cause mucus membrane inflammation. Furthermore it is important to be weary of skin and eye exposure as it can cause irritation. Overall, peracetic acid proper care needs to be taken in its use.

The environmental profile of peracetic acid once again depends on the concentrations encountered. At high concentrations, it can be toxic. However, in use concentrations do not pose major threats to the environment. Furthermore, PAA is a readily decomposable substance and breaks down to products that are not considered harmful to the environment.

This is how we would rate peracetic acid disinfectants based on the key decision making criteria:

• Speed of Disinfection – B to C

o At a 5 minute contact time for killing bacteria and viruses, peracetic acid is fairly rapid in killing. However it carries a 30 minute sporicidal contact time, which is unrealistic unless used for soaking applications.

• Spectrum of Kill – A to C

o Certain temperatures, pH, and concentrations affect the efficacy of peracetic acid.

o At 3000 ppm, peracetic acid can kill all microbial life whereas at 10 ppm, it only kills bacteria.

• Cleaning Effectiveness – C to D

o Peracetic acid has poor cleaning capabilities.

• Safety Profile – B to C

o Peracetic acid has a safe oral toxicity, however, it is sensitizing to the respiratory tract and irritating to skin and the eyes.

• Environmental Profile – A to B

o Peracetic acid readily decomposes and its primary and secondary products are all deemed non-harmful to the environment.

• Cost Effectiveness – B

o Peracetic acid is readily available from various manufacturers and can be found in both concentrated and ready-to-use formats.

Bugging Off!



  1. Wow that is great ! it is safe to use in home and hospitals because it is less acid but good disinfect, It heard it is use for processing in dairy and cheeses.

  2. We're thrilled you've found the blog of use. PAA certainly does have a number of uses and one of the non-halogen based oxidizing chemstries that can be considered when looking for an effective and more environmentally friendly disinfectant or sanitizer.

  3. what is the concentration of acetic acid, propionic acid, lactc acid and citric acid when they used as disinfectants

  4. Thanks for this post, after my weeks of disinfection study, peracetic acid and high concentrated versions of h202 are my new favorite DOC (disinfectants of choice)
    Can you confirm that the 400ppm virucidal is indeed effective against both enveloped and non enveloped viruses at a 5 minute contact time? And at what dillution?

    Also, any instructions on mixing concentrations of h202 and acetic acid (vinegar) to produce a good peracetic acid that meets the levels of ppm you stated in this article?

  5. I'm trying to find out if the disinfecting properties are maintained when combining the two items outside a closed container. I have asthma and I don't want the risk to my lungs (one reason I use these items over bleach). My method has been to wet down the countertop with white vinegar and follow with a thorough spray of peroxide. I have read that the mix is good for washing produce, too, but I'm confused as to how rapidly the created peracetic acid breaks down in the hot water. A lot of people do 1/2c vinegar and 1/2c peroxide in 1/2 gallon warm water as their produce wash. Are they even doing themselves any good, do you suppose ?