But despite the significant benefits of PAA use, there are ongoing concerns about the health and safety of those exposed to PAA while working with the chemical. Numerous accounts have documented acute nasal and eye irritation, shortness of breath, and upper respiratory symptoms following exposure to PAA, such as those found in a recent Health Hazard Evaluation conducted by NIOSH (PDF). ACGIH has established a short-term exposure limit (STEL) for PAA of 0.4 ppm measured as an inhalable fraction and vapor; however, no OSHA regulatory limits exist for exposure to PAA (although Cal/OSHA has a draft rule—download a PDF from the agency's website). Accurate quantification of PAA in air remains challenging as it rapidly degrades into its constituents of acetic acid and hydrogen peroxide, and sampling methodologies are still undergoing development by both governmental agencies and private companies. Safe storage and transport of the chemical is also a priority due to the volatile nature of PAA under certain conditions, such as the presence of soft metals or high temperatures.   QUESTIONS AND ANSWERS  The goal of industrial hygienists working with plant managers and facility safety and health professionals to successfully manage exposure is to help the company conduct hazard assessments, develop training programs for employees, and evaluate the need for engineering controls, administrative controls, and personal protective equipment. Such hazard assessments often create more questions than answers depending on the environment and application of PAA. For example, the current methodology for conducting air sampling for PAA is complex, no enforceable target exposure limit exists in the absence of governmental regulation, employees across all sectors where PAA is used report symptoms of discomfort and illness, and actual exposure levels in facilities vary greatly day to day, and sometimes hour to hour, depending on application method and solution concentration—especially in the food manufacturing sector. Employers need a simple method that works with the environmental conditions consistent with PAA use (like the humid environments found in poultry processing plants) to gauge in real time what is happening on the plant floor when employees report changes in the work environment. In addition, employers need a way to quantify longer-term daily exposure to effectively address employee concerns and pending compliance levels.

Sampling specifically for PAA requires high selectivity because, when in solution with water, it degrades quickly into acetic acid and hydrogen peroxide, and so these parent compounds are always present when there is PAA present, in the water and in the air. OSHA had been sampling for hydrogen peroxide and acetic acid as a proxy for PAA until the agency published a partially validated method in November 2019. There are several reasons why sampling for hydrogen peroxide and acetic acid as a proxy for PAA is potentially problematic. First, the PEL for hydrogen peroxide is 1 ppm and the PEL for acetic acid is 10 ppm, but with PAA there is an ACGIH STEL of 0.4 ppm. PAA is potentially harmful at a concentration that is a whole order of magnitude smaller than either acetic acid or hydrogen peroxide. In health hazard evaluations conducted by NIOSH, sampling was completed where PAA was in use and symptoms persisted among employees, but exposures to acetic acid and hydrogen peroxide returned below the limits of detection or well below the exposure limits. NIOSH has begun exploring the relationship between airborne exposure to all three chemicals and the potential additive effects.

Methods have been developed to simultaneously sample hydrogen peroxide and peracetic acid, as these chemicals are thought to cause the associated irritant symptoms. For a plant manager looking to assess airborne concentrations of PAA, the “Non-Agency Method 57” (PDF) for simultaneous sampling of hydrogen peroxide and peroxyacetic acid (another name for peracetic acid) published by SKC Inc., and based on the Hecht et al. method originally published in The Annals of Occupational Hygiene (PDF), is the only method that uses commercially available equipment and traditional industrial hygiene sampling techniques. In November 2019, the Method Development Team in the Industrial Hygiene Chemistry Division at the OSHA Salt Lake Technical Center published a partially validated method (PDF) to sample for PAA using a cassette containing one 25-mm quartz fiber filter, coated with titanium oxysulfate, in-line with an impinger containing methyl p-tolyl sulfide (MTS) and 4-chlorophenyl methyl sulfone in acetonitrile (ACN). Within the document recommending the impinger method, the researchers stated that they considered the Hecht et al. method, but it did not meet OSHA’s recovery requirement of greater than 75 percent, casting doubt on the ability of the commercially available method to accurately assess exposure in environments where there is high humidity.

Some companies also offer single-point, stationary continuous monitoring systems for PAA, similar to an ammonia or carbon monoxide detector. These systems can be tracked remotely and have alarms to alert personnel to a concern. However, safety and health managers should take into consideration that PAA is highly reactive and breaks down over time and distance from the source of exposure. Therefore, a sensor positioned on a wall ten feet from the source may not accurately report what employees are experiencing while working closer to the application of the PAA solution, which in many cases is within 1–2 feet.

The lack of reliability of the sampling methods indicates a need for additional research into a more stable, robust method that gives consistent results.

WORKER EXPOSURE IN THE POULTRY INDUSTRY  The poultry industry relies heavily on the use of peracetic acid. It is applied in a variety of ways during processing to control bacterial pathogen contamination on the equipment and birds themselves. Peracetic acid is typically delivered in a concentrated form to the facilities either in a tanker to be pumped into a containment silo or in industrial totes. From there, PAA is diluted into an aqueous solution, usually supplemented by a synthetic stabilizer to slow the rate of decomposition or oxidation of the chemical, and pumped throughout the plant at the U.S. Department of Agriculture’s allowable concentration of 50 to 2,000 ppm of PAA. The solution is applied to the poultry in chiller baths, by high pressure nozzles in spray cabinets, or in dip baths along the conveyor belts. Due to the diversity of application techniques, PAA is present in workplace air as both a vapor and aerosol at varying concentrations depending on application type, concentration of PAA in aqueous solution, ventilation characteristics at the point of application, and the location of employees’ workstations with respect to the point of application.

The challenge for evaluating and controlling PAA exposure and the potential health effects specifically within the poultry industry is the variability of the PAA concentration and the wide range of environmental conditions on the processing floor (temperature, humidity, and the presence of other disinfection chemicals). One chemical commonly found on production floors with PAA is chlorine, which may potentially interact with PAA and can interfere with the detection capabilities of PAA sensors. This presents a challenge for field application in poultry/food processing settings where the use of chlorine is prominent, frequent, and concurrent with the use of PAA. Another complication is the possibility that the presence of chlorine affects the chemistry of PAA, especially when the chemicals mix in the drain lines on the production floor. Conflicting results from air sampling in areas of poultry processing plants with established employee complaints and reported symptoms of eye and respiratory irritation could further complicate the resolution of these employees’ concerns, casting doubt on both the sampling results and the complaints.   UNCERTAINTY SHOULD NOT PREVENT ACTION In the absence of certainty around the accuracy of the commercial methodologies available to our research team at the time of our studies in 2017–2019 to sample for airborne peracetic acid, the employer still has a responsibility by law to address the potential exposure by following the established hierarchy of controls. The food production industry, whose line employees include a large population of refugees and non-native English speakers, make up a large percentage of employees exposed on the job to this chemical. This vulnerable workforce faces a variety of barriers to reporting concerns to their employers, including language, different cultural norms, literacy, and a clear understanding of their rights and protections through OSHA.

Employers should not wait until there is a more perfect air sampling method before providing information to employees about the potential hazards associated with PAA—and this information, per OSHA’s hazard communication standard (29 Code of Federal Regulations 1910.1200), must be provided in a language and manner that employees can understand. This includes informing affected employees how to report health and safety concerns—including symptoms potentially related to chemical exposure—to their employer without fear of retaliation. This obligation stands regardless of whether an employer has quantified the level of chemical exposure (including peracetic acid, for example) in the workplace, as some individuals may have higher sensitivities than others.

OTHER CONSIDERATIONS  Other considerations when using PAA include storage, ventilation, and possible inclusion under OSHA’s process safety management standard (29 CFR 1910.119). Industrial hygienists should ask how plants store their PAA and if the storage location is temperature controlled. The concentrated form of PAA has a flashpoint of 105 F or 40.5 C. Commercially available disinfection products contain varying concentrations of PAA, typically not to exceed 40 percent due to the mixture becoming unstable at higher concentrations. These storage areas should be equipped with sensors to detect leaks and a system to notify employees of the failure. Totes, forklift tines, and other equipment and tools used to store, move, and handle the concentrated form of PAA should be checked for the presence of any soft metals, such as copper, zinc, iron, or brass, which react violently with PAA, causing the buildup of oxygen and heat.

As the concentrated form of the chemical is diluted and introduced into a plant, the ventilation in a facility becomes a critical mechanism to control airborne concentrations of PAA. Determining the ventilation rates in areas of the facility that use PAA, the direction employees face in relation to the PAA, and the presence of any “dead spaces” created by the building layout, cross ventilation, or the placement of machinery will help safety and health professionals develop a strategy to reduce employee exposure. Lastly, if the facility uses concentrated PAA in a 60 percent or higher concentration and has more than 1,000 pounds onsite (approximately 115 gallons), the company would also need to comply with the process safety management standard.

BEST PRACTICES AND STRATEGIES FOR MANAGING PAA  Industrial hygienists should work with facilities that use PAA to develop best practices and policies to minimize risk to employees and protect the facilities from physical damage. Standard procedures to assess employee exposure to PAA, including a PAA monitoring program for daily production, should be established to get a baseline of exposures. OHS professionals should conduct walkthroughs to observe the use of PAA throughout the plant and monitor for fluctuations in exposure when there are employee complaints. Fluctuations in exposure might be caused by spray nozzles having been adjusted or blocked, standing water in pans or on the floor, the addition of PAA application sites, and changes to the concentration of the aqueous solution of PAA. Safety and health professionals should conduct regular walk-throughs of the production floor to assess the ventilation in the facility, paying careful attention to the sources of PAA exposure in relation to employees’ workstations. Management of exposures should be a collaborative effort between facility safety and health professionals and those responsible for quality assurance. If the concentration of PAA used or the number of application sites is increased, the quality assurance team may see an improvement in the final product from the standpoint of consumers or users; however, employees exposed to these changing amounts of PAA during production may notice new or more severe symptoms from exposure. This underscores the importance of clear communication between persons responsible for managing the use of the chemical and how changes in operations can impact the health of employees.

Industrial hygienists should also review the company’s hazard communication program and injury and illness reporting program. All parties (frontline employees, managers, wastewater treatment employees, maintenance workers, and so on) associated with the application of PAA must not only receive but also be able to understand the training on the health effects of exposure to PAA. To help employers provide training about PAA and other chemicals used in food disinfection and sanitation, the Safety, Health, and Environmental Services group at Georgia Tech developed a series of hazard communication training videos in six different languages. Beyond that, employees need a mechanism to report adverse health effects from exposure, and employers need to be prepared to respond, including by monitoring for exposure, adjusting the ventilation, adjusting the concentration of PAA, rotating employees from certain positions, and sending the employee for medical treatment if necessary.

Finally, every facility should establish a risk management plan for the use of PAA in the facility. The plan should identify risks, estimate impacts, define responses to risks, and develop planned responses. Each step of the process from the delivery of the product through the impact PAA has on wastewater treatment should be included in the plan. For assistance in the development of a risk management plan, we recommended using the template from the U.S. Department of Health and Human Services’ Public Health Emergency website (PDF).

To get started with assessing PAA exposure at a job site, refer to two documents available from the Georgia Tech OSHA Consultation website: “Peracetic Acid Exposure Assessment and Control Strategies for PAA: Planning Checklist” and “Peracetic Acid Safety and Health Guide for Poultry Processing Facilities.”

Send feedback to The Synergist.