Peracetic acid (CAS No. 79-21-0), also known as peroxyacetic acid or PAA, is an organic chemical compound used in numerous applications, including chemical disinfectant in healthcare, sanitizer in the food industry, and disinfectant during water treatment. Peracetic acid has also previously been used during the manufacture of chemical intermediates for pharmaceuticals. Produced by reacting acetic acid and hydrogen peroxide with an acid catalyst, peracetic acid is always sold in stabilized solutions containing acetic acid, hydrogen peroxide, and water. For the food and healthcare industries, peracetic acid is typically sold in concentrates of 1 to 5 percent and is diluted before use. Many users know peracetic acid to be versatile and effective, and professionals with environmental responsibilities consider it to be environmentally friendly due to its decomposition products, which include acetic acid, oxygen, and water. However, industrial hygienists recognize that it is also highly corrosive and a strong oxidizer, and exposure to peracetic acid can severely irritate the eyes, skin, and respiratory system.

“I’ve never seen a chemical whose applications cross over from food and beverage to wastewater,” says Debbie Dietrich, CIH, senior vice president of sales and marketing and corporate industrial hygienist at SKC Inc. “From an industrial standpoint, there are so many advantages to peracetic acid: it’s easy to apply and it doesn’t leave any toxic residues.”

Dietrich, who first learned about peracetic acid from the AIHA Healthcare Working Group, was surprised to find that the use of the compound extends far beyond the healthcare industry, where it’s primarily used as a chemical disinfectant. Outside of hospitals, peracetic acid has a wide variety of applications, including as a preventive additive to control bacteria such as in cooling towers and as a biocide to inhibit microbes in wastewater treatment. It’s even used for bleaching and wastewater treatment in the pulp and paper industry. In the food industry, peracetic acid is an effective antimicrobial used during poultry processing, to wash fresh produce, to sanitize surfaces, and more.

Christine R. Knezevich, CIH, an industrial hygienist for the U.S. Air Force who has previous experience working in the food industry and for a manufacturer/distributor of peracetic acid, agrees that the compound has many advantages.

“What’s so wonderful is it’s no-rinse,” Knezevich, a former Safe Quality Food (SQF) practitioner, explains. She adds that because peracetic acid functions well at cold temperatures it can be used effectively in freezers and coolers where meat processing occurs. And some peracetic acid products can be used for more than one task.

“The great thing about peracetic acid is that depending on the product registration and instructions for use, you can use it for multiple purposes: as a sanitizer, a disinfectant, or a sterilizer,” she explains. “Many times, it’s just a matter of the contact time and the concentration.”

According to Knezevich, peracetic acid doesn’t pose an issue for facilities with water discharge permits under EPA’s National Pollutant Discharge Elimination System (NPDES) permit program. The chemical compound is found on the agency’s as an antimicrobial active that EPA has “verified to be of low concern based on experimental and modeled data.” Peracetic acid is especially attractive to companies who are under pressure to use greener chemicals—particularly those that are certified under the ISO 14001 . Knezevich explains that large companies evaluate suppliers based on these “green” requirements. The International Chemical Safety Card (ICSC) for stabilized peracetic acid warns of short-term exposure effects, noting that “the substance is corrosive to the eyes, the skin and the respiratory tract.” Symptoms of acute exposure may include cough, labored breathing, and shortness of breath; skin redness, pain, and blisters; and “severe deep burns” in the eyes, according to the ICSC, which is available on NIOSH’s . While peracetic acid is highly irritating to those who work with it—manufacturing workers are most at risk, along with chemists studying the compound—Knezevich maintains that the primary concern associated with peracetic acid is that it’s a strong oxidizer.

“Our major concerns were actually the fire and explosion hazards and reactivity issues,” she says, explaining that peracetic acid reacts violently with soft metals such as brass, copper, iron, and zinc. And at concentrations of 15 percent or higher, a major chemical manufacturer, FMC Corporation, recommends explosion-proof equipment.

But for products containing concentrations of peracetic acid of five percent or less, which is what the majority of industries are dealing with, the biggest worry is that the compound will come into contact with the wrong type of metal, says Knezevich. She describes a mishap in which a galvanized steel dip tube was installed through the bung of a 55-gallon drum of a solution containing peracetic acid. The drum was laid horizontally in its cradle over the weekend so it would be ready for use the following week. The soft metals of the dip tube reacted with the peracetic acid, resulting in a buildup of oxygen gas. Sometime over the weekend, the drum ruptured from the heat and pressure of the reaction, releasing its contents onto the floor. Had staff been in the facility during that time, they likely would have noticed something was wrong.

“They would have noticed that it was starting to bulge or foam,” Knezevich says. “I’ve worked for chemical companies that made products with peroxide, and, believe me—you’ll know when something has gone wrong.”

Workplaces using peracetic acid at lower concentrations will preferably have some type of chemical metering pump system in place to minimize exposures to workers. During a roundtable on surface disinfectants at AIHce 2013, Knezevich described how such a system can be set up in a space such as a janitor’s closet and be used to add water to concentrated peracetic acid products. Figure 1 depicts an example of a dispensing system. Some companies that sell peracetic acid products will also help set up and train workers on chemical dispensing equipment.