Cold Sterilant Exposure: Know the Risks

Cold sterilants, a class of non-bleach liquid sporicidal disinfectants, have been used for many years to control microbial contamination in R&D and manufacturing industries. Using these compounds in the workplace, however, introduces health and safety risks. Managers need to know these risks—and more importantly, be able to evaluate employee exposure to these disinfectants.

Industrial Disinfectants: Necessary Hazards

Cold sterilant products, such as STERIS’s Spor-Klenz^®, are a stabilized mixture of peracetic acid (PAA), hydrogen peroxide, and acetic acid. The various commercially available mixtures contain varying concentrations of each of these components in a chemical equilibrium, and come either pre-mixed or concentrated. All of the chemicals in the mixture present risk:

• PAA is a corrosive, peroxide-based oxidizer. It is highly reactive and unstable.
• Hydrogen peroxide is a strong oxidizer and irritant, often found in household products in much lower concentrations than in commercial applications.
• Acetic acid is an organic acid, present in vinegar and other household products at low concentrations.

Exposure to any of these chemicals can cause:

• Strong irritation to the eyes, skin, and mucous membranes (including stinging and tearing of the eyes)
• Coughing, difficulty breathing, or even pulmonary edema

Official Exposure Limits

Due to the abundant risk these chemicals pose, multiple regulatory bodies have established exposure limits for employees working with them. These governing organizations include the:

• Occupational Safety and Health Administration (OSHA)
• National Institute for Occupational Safety & Health (NIOSH)
• American Conference of Governmental Industrial Hygienists (ACGIH)

Exposures longer than periods outlined below can have dire health impacts.

PAA

Neither OSHA nor NIOSH has established exposure limits for PAA, but ACGIH has adopted a Threshold Limit Value (TLV) of 0.4 parts per million (ppm) as a 15-minute short-term exposure limit (STEL). This is the only published exposure limit for PAA; ACGIH does not offer an 8-hour time-weighted average (TWA) TLV.

Hydrogen Peroxide

OSHA, NIOSH, and ACGIH have set occupational exposure limits of 1 ppm as the TWA exposure limit for hydrogen peroxide.

Acetic Acid

OSHA, NIOSH, and ACGIH have set 10 ppm as the allowable TWA exposure limit; ACGIH and NIOSH have both adopted a 15-minute STEL of 15 ppm.

Sampling to Evaluate Employee Exposure

Mandated adherence to these thresholds generates the need for sampling, in order to monitor employee exposure and ensure limits are not bypassed. Successful sampling operations can be challenging, however, as managers must get accurate assessments of all three components—PAA, hydrogen peroxide, and acetic acid.

While NIOSH and OSHA both offer sampling methods for acetic acid and hydrogen peroxide, there isn’t a clearly defined PAA process; OSHA has only recently developed a partially validated method for trial use. As such, there is no industry recognized standard analytical method.

Some potential sampling methodologies and tools include:

• INRS technique: A method commonly used for sampling PAA was published in 2004 by the Institut National de Recherche et de Sécurité (INRS), a French research organization similar to our NIOSH. The INRS method uses a sampling train to filter out hydrogen peroxide and capture PAA and acetic acid together. Several American Industrial Hygiene Association (AIHA)-accredited labs provide this analysis.
• Direct reading devices: While not appropriate to accurately assess employee exposure, direct reading devices can be an extremely valuable reference point while performing other testing methods. Plus, they are commercially sold for all the hazardous components in cold sterilants like Spor-Klenz^®—PAA, hydrogen peroxide, and acetic acid.

A direct reading device can:

• Confirm and validate analytical methods
• Be used to investigate specific facility areas for local vapor buildup
• Provide an indication of levels in adjacent areas
• Be used to track area concentrations over time

Even with these and other sampling methods, the complexities of testing, and the hazards of the chemicals themselves, cause difficulty. Common challenges include:

• STELs: Typical sampling methodologies for PAA and acetic acid limit sampling time to 15 minutes at most. These STELs mean that the industrial hygienist taking samples must stay in close proximity to the monitored employee—at least for some of the process. Depending on the facility layout and employee work type, this requirement may complicate logistics.
• Chemical equilibrium maintenance: For many of the same reasons that PAA is such an effective sterilant, it is also a relatively unstable chemical; it may readily decompose into hydrogen peroxide and acetic acid. While the initial cold sterilant may be stable, the chemical equilibrium of the mixture depends on many factors, including:
  • Temperature
  • Humidity
  • Ventilation
  • pH
  These chemical mechanisms can be complex. Depending on your facility’s specific environment, the way the sterilant is mixed, handled, and applied can lead to changing air concentrations—this makes short-term sampling management and detailed observations all the more crucial.

The complexities of sampling for exposure monitoring require you to work closely with your laboratory to carefully review in detail the sampling and analytical methods you include in your sampling plan.

Cold Sterilant Controls Provide a Safeguard

Once employee exposure has been evaluated, the ideal engineering and administrative controls to limit exposure, at both the role and facility levels, can be identified. Mitigating controls include:

• Ventilation, which reduces the amount of chemicals in the air, improving air quality and preventing inhalation of PAA, hydrogen peroxide, or acetic acid. This is the primary safeguard for exposure minimization.
• Written standard operating procedures (SOPs) that detail the relevant steps that all employees who may be exposed to any cold sterilant must take to keep themselves safe.
• Proper training to ensure employees know:
  • The risks
  • How to protect themselves
  • Emergency response
  • Safe techniques for safe mixing, mixing, pouring, spraying, and mopping
  • How to avoid chemical overuse, which will prevent aerosolization and reduce danger from exposure
• Correct personal protective equipment (PPE) use to prevent eye, face, and skin exposure to liquids or vapors. The PPE level should be appropriate for the wearer’s use and job function.

All of these controls are very specific to each unique facility and process. Detailed observation of tasks will enable identification of areas for improvement and exposure minimization.

If and when these engineering and administrative controls can’t be implemented in a facility or don’t work to limit exposure to allowable limits, the use of respiratory protection, such as air purifying respirators, will likely be necessary. Of course, the deployment of respiratory protection should follow your institution's written respiratory protection and occupational medicine programs.

Partner for Industrial Hygiene

When personnel are working with a cold sterilant such as Spor-Klenz^®, accurate exposure evaluation can provide essential information; information that can then be used to recommend and provide proper worker safeguards. The challenges that cold sterilants pose can be complex—and improper precautions can be deadly.

A dedicated environmental, health, and safety (EHS) partner can make the difference between safety and disaster. Triumvirate Environmental is such a partner, with decades of experience in industrial hygiene, biosafety, and consulting. We can assist you with all aspects of recognizing and controlling worker exposure to hazardous agents. Click the button below for more information about our industrial hygiene services and to start a conversation with us.