Wednesday, March 6, 2013

Update on ACGIH STEL for Peracetic Acid

Peracetic acid (PAA) is a strong oxidizing agent and an effective biocide that upon reaction degrades to safe byproducts (acetic acid, oxygen and water) and so PAA has found widespread use from disinfection in food production, sterilization in healthcare, aseptic packaging in food processing among others. As with any broadly biocidal disinfectant, exposure to workers poses health risks. There is increasing awareness of the inhalation risks of PAA vapor and recently the EPA issued Acute Exposure Guidelines for PAA. The AEGL 1 for PAA is about 0.17 ppm for a ten minute to 8 hour exposure. The AEGLs are not workplace exposure limits since 'AEGLs represent threshold exposure limits for the general public and are applicable to emergency exposure periods ranging from 10 minutes to 8 hours.'

A workplace exposure level is typically lower than the AEGL because a workplace exposure limit refers to the exposure a worker may receive on a repetitive basis. There are currently no workplace exposure limits for PAA, but the ACGIH, one of the pre-eminent workplace safety organizations in the world is considering a 15 minute short term exposure limit threshold limit value (STEL TLV) for PAA. The ACGIH had previously issued a notice for change (NIC) for a STEL of 0.2 ppm, but the NIC has been revised to a STEL of 0.4 ppm (15 min). The ACGIH is currently accepting comments on this proposed STEL. The full documentation for the NIC is available for purchase for $60. ChemDAQ encourages all interested parties to submit their comments directly to the ACGIH.

A workplace exposure limit is only useful if there is a way to measure the gas or vapor concentration. Fortunately, ChemDAQ now offers a continuous monitor for PAA designed for workplace safety. The range is 0 to 3 ppm, with a minimum detection limit of 0.04 ppm.

Until recently there were few practical methods to measure PAA and many industrial hygienists would settle for measuring hydrogen peroxide and acetic acid, which are equilibrium components with PAA in solution and for which both analytical methods and workplace exposure limits are readily available (OSHA, NIOSH and ACGIH) This approach has its limitations since PAA is a more irritating agent that hydrogen peroxide, and means optimized to detect hydrogen peroxide may not detect PAA very well. It is likely therefore that the workplace exposure to PAA has been greatly underestimated.

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