Fallacy of Inferring Lack of Peracetic Acid Vapor from Measurement of Hydrogen Peroxide and Acetic Acid Vapor

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4. Page 4 of 5 SL-117-A-0.00 ChemDAQ Inc. • 300 Business Center Drive • Pittsburgh, PA • 15205 phone 412.787.0202 • fax 412.788.2526 Measurement of Peracetic Acid Concentrations There are presently no standard methods for the measurement of PAA vapor; though the OSHA Salt Lake City Technical Center is planning to address the issue. At the moment there are two commercial methods for monitoring peracetic acid. ChemDAQ’s Steri-Trac ® Monitor Continuous monitor for PAA, minimum detection limit 0.04 ppm, range 0 to 6 ppm. 12 Two user adjustable alarms, and the Steri-Trac monitors can interface with a ChemDAQ DAQ ® computer (data logging, TWA calculations, reports, graphing etc), to interface with external systems. Data output formats from the DAQ include 485 modbus, 13 SQL database, various Ethernet formats. Stainless steel enclosures available for wet environments. Customization available. SKC SKC offer diffusion tubes for measurement of PAA in which a sample is collected over time and the tube is then sent away for laboratory analysis. 14 Obviously this method requires a significant time between sampling and result and so this method is unable to provide any warning in the event that the PAA concentration exceeds safe levels. The SKC diffusion tube is based on the paper by Hecht et al. 15 According to the method, the tube is composed of: (i) a cassette with quartz fiber filters impregnated with titanium oxysulfate hydrate for the sampling of hydrogen peroxide followed by; (ii) a tube filled with silica gel soaked with methyl p-tolylsulfoxide for the sampling of PAA. The analysis 12 http://www.chemdaq.com/products/steri-trac-area-monitors/steri-trac-peracetic-acid-area-monitor/ 13 Modbus® is a registered trademark of Modicon Inc. 14 http://www.skcinc.com/instructions/40056.pdf 15 Peroxyacetic Acid/Hydrogen Peroxide; G. Hecht, M. Héry, G. Hubert And I. Subra, Annals of Occupational Hygiene , Vol. 48, No. 8 (2004), pp. 715-721. Full text available from http://annhyg.oxfordjournals.org/content/48/8/715.full

5. Page 5 of 5 SL-117-A-0.00 ChemDAQ Inc. • 300 Business Center Drive • Pittsburgh, PA • 15205 phone 412.787.0202 • fax 412.788.2526 of this silica gel was performed by liquid chromatography with UV detection of the methyl p-sulfone generated by the sampling of PAA. Other There are several other methods that have been published for detection of PAA, but none of them are yet commercial. 16 Conclusions  Peracetic acid is widely used as a biocide in healthcare, food and beverage and water treatment because it is a strong oxidizing agent with no harmful residues.  The biocidal properties of PAA make it potentially hazardous to operators exposed to and the ACGIH has issued a STEL TLV of 0.4 ppm, compared to the ACGIH TLV for acetic acid (10 ppm, 8 hr TWA) and hydrogen peroxide (1 ppm, 8 hr TWA)  There are no OSHA or NIOSH standard methods for detecting PAA and so some industrial hygienists have monitored for hydrogen peroxide and acetic acid, if these are below their respective OSHA PELs, have concluded that the PAA levels must also be below safe levels.  This assumption is false since the PAA concentration can be well above the TLV even if the vapor concentrations of H 2 O 2 and AcOH are below their respective TLVs.  It is important therefore to measure PAA directly. Two commercial methods exist, one a diffusion tube that requires subsequent laboratory analysis from SKC and the other a continuous PAA vapor monitor from ChemDAQ that not only provides instantaneous readings, but also provides alarms data collection, reports etc. 16 https://www.jniosh.go.jp/en/indu_hel/pdf/IH_48_2_217.pdf ; http://www.sciencedirect.com/science/article/pii/S1010603003000674 ; http://www.ncbi.nlm.nih.gov/pubmed/20424354

2. Page 2 of 5 SL-117-A-0.00 ChemDAQ Inc. • 300 Business Center Drive • Pittsburgh, PA • 15205 phone 412.787.0202 • fax 412.788.2526 Hydrogen peroxide 5 and acetic acid 6 also have standard OSHA methods for detection, but again PAA does not. Where less accuracy is necessary, there are also gas detection tubes from Draeger, Gastec and others for acetic acid and hydrogen peroxide, but not for PAA. Employers who use PAA generally want to keep their people safe and have a legal duty to do so, 7 and know that PAA vapor is hazardous (based on ACGIH STEL TLV) and so need to measure the concentration of PAA in the air. However, the lack of standard methods to detect PAA has led several industrial hygienists to measure hydrogen peroxide vapor and acetic acid vapor; and from these measurements infer that if these concentrations are below the respective OSHA PELs/ACGIH TLVs, then the PAA must also be below within safe limits. This argument is however flawed. Fallacy of Inferring Safe PAA Concentrations Different Chemicals PAA, hydrogen peroxide and acetic acid are separate chemicals with different hazard levels as expressed by the OSHA PELs /ACGIH TLVs and so the measurement of two of them does not automatically equate measurement of the third and particularly determination that the vapors of hydrogen peroxide and acetic acid are below safe levels does not mean that the concentration of PAA is below safe levels. Complex Equilibrium At equilibrium, it is possible to get solutions which are high in PAA and high in hydrogen peroxide or low in hydrogen peroxide depending on the concentration of acetic acid. The equilibrium between AcOH, H 2 O 2 and PAA adds complexity which the assumption that if AcOH and H 2 O 2 vapor levels are within safe limits, so must PAA vapor, does not take in to account. Equilibrium Calculations Show Safe Assumption Invalid The following example illustrates that even at equilibrium the PAA concentration can be high enough to be hazardous even when the hydrogen peroxide and acetic acid concentrations are not. There are many different blends available with differing concentrations and ratios peracetic acid to hydrogen peroxide and acetic acid, the example below uses a common commercial blend. The equilibrium vapor concentration of a component of a liquid can be modeled by Raoult’s law, which says that the vapor pressure of an ideal mixture is proportional to the mole fraction. 8 5 Method VI-6, https://www.osha.gov/dts/sltc/methods/inorganic/id006/hydrogen_peroxide.html 6 Method PV2119, https://www.osha.gov/dts/sltc/methods/partial/pv2119/pv2119.html 7 Occupational Safety and Health Act (1970), section 5. 8 http://en.wikipedia.org/wiki/Raoult's_law

1. Page 1 of 5 SL-117-A-0.00 ChemDAQ Inc. • 300 Business Center Drive • Pittsburgh, PA • 15205 phone 412.787.0202 • fax 412.788.2526 Fallacy of Inferring Lack of Peracetic Acid Vapor from Measurement of Hydrogen Peroxide and Acetic Acid Vapor Richard Warburton 1 April 2015 Summary Some industrial hygienists, lacking a standard method for peracetic acid vapor (PAA) measurement have relied on measuring only acetic acid and hydrogen peroxide and concluding that if the latter two are below their respective OSHA PELs/ACGIH TLVs, then the PAA concentration must also be within safe limits. This report shows that that assumption is false and therefore it is necessary to measure the PAA vapor concentration directly. Two commercial methods exist to measure PAA vapor, a continuous vapor monitor from ChemDAQ Inc. 2 and a diffusion tube from SKC. 3 Introduction Peracetic acid, (aka peroxyacetic acid) is finding widespread use in healthcare, food and beverage and water treatment as a biocide. PAA is a strong oxidizing agent, that is little affected by the catalase enzyme which all cells have to remove hydrogen peroxide and so is a more effective biocide than hydrogen peroxide. Both hydrogen peroxide and PAA have the advantage that they degrade into harmless products, oxygen, water; and additionally for PAA, acetic acid (AcOH). PAA is formed as an equilibrium mixture in aqueous solution between acetic acid and hydrogen peroxide CH 3 COOH + H 2 O 2  CH 3 COOOH + H 2 O Hydrogen peroxide and acetic acid both have OSHA permissible exposure limits (PELs) but PAA does not. Compound OSHA PEL 4 ACGIH TLV AcOH 10 ppm 8 Hr TWA 10 ppm 8 Hr TWA H 2 O 2 1 ppm 8 Hr TWA 1 ppm 8 Hr TWA PAA n/a 0.4 ppm 15 min. TWA (STEL) 1 Richard Warburton, Ph.D., J.D. is the Chief Technology Officer and General Counsel of ChemDAQ Inc. 2 http://www.chemdaq.com/products/steri-trac-area-monitors/steri-trac-peracetic-acid-area-monitor/ 3 http://www.skcinc.com/ 4 29 CFR 1910.1000 Tbl Z-1

3. Page 3 of 5 SL-117-A-0.00 ChemDAQ Inc. • 300 Business Center Drive • Pittsburgh, PA • 15205 phone 412.787.0202 • fax 412.788.2526 The calculation is as follows:  A typical mixture contains 15 % PAA, 10 % H 2 O 2 , 35% AcOH, (FMC’s, now Peroxychem’s 15% PAA solution) 9 ,  The vapor pressure of PAA, H 2 O 2 , ACOH and water at 25 o C are 1.93, 0.258, 2.07, and 3.17 kPa. 10  The mole fractions can be calculated: 0.060, 0.089, 0.18 and 0.67 for PAA, H 2 O 2 , AcOH and H 2 O respectively.  Combining the vapor pressures with the mole fractions gives the vapor pressures: 0.12, 0.023, 0.37, 2.1 kPa for PAA, H 2 O 2 , AcOH and H 2 O respectively.  These numbers can be easily converted to ppm: for 1,100, 230, and 3,600 PAA, H 2 O 2 and AcOH. These concentrations are clearly over the OSHA PELs as may be expected for the concentrated solution.  Dilute the solution such that the equilibrium vapor concentration of PAA = 1 ppm, then the H 2 O 2 vapor concentration will be 0.2 ppm and the AcOH vapor concentration will be 3.2 ppm. Thus for a diluted PAA mixture, such that the hydrogen peroxide vapor is 0.2 ppm and the AcOH is 3.2 ppm (both below the OSHA PELs and ACGIH TLVs), the PAA concentration would be 1 ppm, well above the ACGIH STEL TLV of 0.4 ppm). Clearly, one cannot determine that the PAA concentration is within safe limits just because the hydrogen peroxide and acetic acid are below their respective OSHA PELs and ACGIH TLVs. Non-Equilibrium Conditions Add Additional Error In principle, if one knew the PAA solution composition, the temperature, one could predict the relative vapor concentrations of PAA, H 2 O 2 and AcOH as shown above, and if the H 2 O 2 and AcOH vapor concentrations were measured, then the PAA concentration could be estimated. However, this calculation is fraught with error. Not only is this an involved calculation, but most systems are not at true equilibrium due to ventilation, temperatures changes, and the inherent slow kinetics of the PAA equilibrium reaction, 11 as well as losses from evaporation, adsorption, absorption, reaction etc.. Since the system is not at equilibrium, equilibrium calculations will not inaccurate and so cannot be relied on to estimate the PAA concentration given the hydrogen peroxide and acetic acid concentrations. Therefore one cannot determine if the PAA concentration is above safe levels simply by determining that H 2 O 2 and AcOH levels are both below safe levels. 9 http://www.peroxychem.com/chemistries/peracetic-acid 10 CRC Handbook of Chemistry and Physics, 76 th Ed, Lange’s Handbook of Chemistry, 12 th Ed. 11 “Preparation of peracetic acid from hydrogen peroxide Part I: Kinetics for peracetic acid synthesis and hydrolysis;” Xuebing Zhaoa,, Ting Zhang, Yujie Zhoub, Dehua Liu; Journal of Molecular Catalysis A: Chemical 271 (2007) 246–252.

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