Sometime ago, ChemDAQ had a customer who installed four new Hydrogen Peroxide sterilizers. The customer wisely decided to place a ChemDAQ Steri-Trac® monitor with a remote sensor on each one. The customer found that at the end of every cycle when the door was opened, a cloud of Hydrogen Peroxide in the 20 to 40 ppm range was emitted for a short while before falling back to low levels again. Hydrogen Peroxide vapor has essentially no smell, and the first perception is usually the irritation the vapor induces.

The customer asked the sterilizer manufacturer to correct the problem but without success. The customer managed the situation by telling employees to open the door at the end of a cycle and step away until the monitor readings fell down to safe levels before removing the load. The customer later relocated the sterilizers to a custom built room with exhaust ventilation directly above each sterilizer.

The manufacturer (who shall remain nameless) pointed out to our customer that the OSHA permissible exposure limit ( PEL ) and ACGIH Threshold Limit Value (TLV) [1] are 1 ppm, calculated as a time weighted average and was not exceeded. They also noted that the NIOSH Immediately Dangerous to Life and Health value (IDLH) for Hydrogen Peroxide of 75 ppm was not exceeded and so there was no over exposure and so no problem.

In terms of just the PELs and IDLH’s, the manufacturer was correct, however they missed the key point of the General Duty Clause in the Occupational Safety and Health Act of 1970: “Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees;…”

If the OSHA PEL and ACGIH TLV are both 1 ppm, then it is reasonable to assume that repeated inhaling 25 to 40 ppm is probably not a good thing to do to one’s lungs, especially for a technician in a busy department who is sequentially loading and unloading four sterilizers every hour.

The ACGIH states the following:
Excursions in worker exposure levels may exceed 3 times the TLV-TWA for no more that a total of 30 minutes during a workday, and under no circumstances should they exceed 5 times the TLV-TWA, provided that the TLV-TWA is not exceeded. [1]

The ACGIG TLV for Hydrogen Peroxide is 1 ppm, 8 hour TWA, and so according to the ACGIH the maximum exposure to Hydrogen Peroxide should be no more than 5 ppm. Clearly some of the exposures recorded here exceed this value. The current PEL for Hydrogen Peroxide does not reflect this risk but a short term exposure limit (STEL) would provide much better protection.

A couple of states, Washington and Hawaii already have STELs for Hydrogen Peroxide, of 3 ppm as do some other countries such as the UK (STEL = 2 ppm). Is it time that OSHA set a STEL for Hydrogen Peroxide as well as its current 8 hour TWA PEL?

[1] 2014 TLVs and BEIs Based on the Documentation of the Threshold Limit Values for Chemical Substances and Physical Agents & biological Exposure Indices. ACGIH. p5