Researchers Find Leakage Problems with Hydrogen Peroxide Sterilizers
An investigation of hydrogen peroxide vapor leakage from hydrogen peroxide sterilizers was recently conducted in Japan in response to reports of eye and throat irritation from workers and even chemical indicator color changes before sterilization. The sterilizers included several models of Sterrad® sterilizer from Advanced Sterilization Products, and the V-Pro1 from Steris.
The investigators measured the hydrogen peroxide concentration inside a sterilizer immediately after the end of the cycle, when people would be reaching in to remove the load, and found very high concentrations (34 ppm Sterrad 100S; 60 ppm Sterrad 200; and 13 ppm V-Pro1) far above the OSHA PEL or 1 ppm (8 Hr TWA).1 They also found that the sterilizers sometimes emit high concentrations of hydrogen peroxide when they exhaust, even though it passes through a catalytic converter. For the Sterrad 200 the researchers measured over 100 ppm, much higher even than the NIOSH Immediately Dangerous to Life and Health level for hydrogen peroxide of 75 ppm.2 The cause of this high reading was found to be a broken demister cap, a fault that would not normally be detected during routine periodic inspection, but high readings continued even after repair.
They also found that sterilized products continued to off-gas hydrogen peroxide after they had been removed from the sterilizer. Off gassing of sterilant gas is well known for ethylene oxide, but this study concluded that the same issue occurs with hydrogen peroxide as well. The investigation found that some plastic devices continued to emit hydrogen peroxide vapor for many days after sterilization in a Sterrad NX, the amount and duration of emission varying with the plastic used. For example, a polyetherimide stapler initially emitted over 300 ppm hydrogen peroxide; and it took six days to fall to 10 ppm, and 24 days before the concentration fell below 1ppm (the OSHA PEL). Even flexible scopes continued to out gas hydrogen peroxide above 10 ppm for 18 to 40 hours.
These results explain the eye and throat irritation that led to this investigation and in a questionnaire to healthcare facilities, the investigators found that 28% of those using hydrogen peroxide sterilizers reported an adverse event. Similar reports of similar irritation of workers near hydrogen peroxide sterilizers can be found in the FDA MAUDE database. 3 As a result of this study, the researchers recommended that hydrogen peroxide be monitored in the same manner as ethylene oxide. Full details of the study may be found at www.wfhss.com/html/conf/wfhss-conference-2012/lectures/wfhss_conf20121121_lecture_sp_s702_en.pdf 4
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1 OSHA Air Contaminants Standard, 29 CFR 1910.1000 Tbl Z-1
3 http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfmaude/search.cfm “Problems on Hydrogen
4 Peroxide Sterilisation － New Proposal for Safety and Effective Use”;Annual WFHSS and JSMI Conference 2012 13th World Sterilization Congress; 23 Nov,2012; Rika Yoshida, Hiroyoshi Kobayashi; Division of Infection Prevention and Control, Tokyo Healthcare University Postgraduate School.