Thursday, April 25, 2013

Simple Human Error Leads to Ethylene Oxide Release from Sterilizer

We received a call this morning that there had been an ethylene oxide release from a hospital sterilizer. Sterile processing staff at a large hospital placed a load into one of their three ethylene oxide sterilizers and started the cycle. A short while later the cycle aborted and while trying to identify the problem, one of the staff members unexpectedly opened the door.

The ChemDAQ ethylene oxide monitors immediately went into alarm and the two employees rapidly left the room. They and the rest of sterile processing evacuated the department until the monitors showed it was safe for them to return. In addition to the two women in the sterilization room, the other four workers in the department were all sent to the emergency room for evaluation. Fortunately, it appears that everyone was able to get out quickly enough that no-one suffered adverse symptoms from exposure to ethylene oxide.

The cause of the problem was later found to have been due to a simple human error. The manufacturer's service technician had been on-site earlier that day to do the regular preventative maintenance and when he was finished, he forgot to switch the sterilizer back from service mode to normal mode. In service mode the cycles times are short and the door locks are apparently disabled.

This incident shows the importance of being aware that even well designed, well maintained equipment can and sometimes does fail because of a simple human error that any of us could have made.

This blog has railed against the use of badges for ethylene oxide monitoring in healthcare as being ineffective. If these two workers had not evacuated after the sterilizer door was opened, then their exposure to ethylene oxide would have been considerably higher and it would have made no difference whether they were wearing a badge or not. Fortunately for the staff at this hospital, they were protected by a ChemDAQ monitoring system.

Exposure Limits for Peracetic Acid

As a manufacturer of gas monitors, one of the questions that we face is where to set the alarm limits. The ChemDAQ Steri-Trac® monitor has two instantaneous alarms (high and low) which respond to the current concentration of the target gas and the ChemDAQ DAQ® computer, in addition to data collection, reports etc., calculates time weighted averages and provides alarms based on these time weighted average exposure (TWA).

For a vapor such as hydrogen peroxide, which has an OSHA permissible exposure limit (PEL) of 1 ppm (8 hr TWA), the DAQ has an 8 hour TWA of 1 ppm. There is no OSHA short term exposure limit for hydrogen peroxide and so the DAQ does not have a STEL alarm.

For vapors such as peracetic acid for which there are no OSHA PELs, alternative exposure limits must be sought. The first step is look to see if there are any ACGIH threshold limit values (TLV) or other recognized exposure standard. The ACGIH does not have a TLV for peracetic acid, but it has proposed a short term exposure limit (STEL) of 0.4 ppm. In the absence of recognized exposure limits, one looks for published studies and reviews of published studies.

Recently Pechacek, Maier and Haber reviewed a range of studies of the health effects of exposure to peracetic acid and came up with several recommendations. The authors are with Ecolab, one of the largest suppliers of peracetic acid and TERA, a non-profit organization dedicated to solving problems associated with public health.

The authors' first recommendation is that neither a ceiling limit nor a STEL on its own is appropriate since

" PAA is an irritant that can cause cytotoxicity. Insufficient dose-response information is available to ensure that the absence of a sensory response also protects from accumulating subclinical cytotoxic responses." The authors go on to comment that the combination of 8 hr TWA and STEL is valuable. This conclusion may have significance to the ACGIH proposed STEL for peracetic acid.

In addition to recommending the use of both an 8 hr TWA and STEL, Pechacek et al calculated a value for the 8 hr TWA occupational exposure limit based on published reports of 0.26 to 1.56 mg/m3, which corresponds to a concentration range of 0.08 to 0.5 ppm.

The ChemDAQ DAQ calculates both the STEL and the 8 hour TWA, and the ChemDAQ alarm limits are set at 0.4 and 0.2 ppm respectively, both within the range recommended by Pechacek, Maier and Haber.

Wednesday, April 10, 2013

Honeywell Stops Taking Orders for Oxyfume Ethylene Oxide Sterilants

Honeywell announced in August 2012 that it would discontinue production of the Oxyfume ethylene oxide (EtO) sterilant gas cylinders because of Clean Air Act regulations from the EPA banning the sales and use of most HCFC based products like Oxyfume in the end of 2014.

On March 15th, Honeywell announced that they would no longer receive orders for Oxyfume after March 31st 2013 and that Oxyfume 2002 and Oxyfume 2000 cylinders should be sent to Honeywell for recycling until production ceases later this year. Cylinders of Oxyfume 12, a CFC-based product phased out in 1995, cannot be received by Honeywell and current and former customers should contact Honeywell for information on how to handle these cylinders.

Ethylene oxide used to be the dominant low temperature sterilant in healthcare and ethylene oxide blends were the primary means of delivering EtO. The blends were used because ethylene oxide is a flammable/explosive gas with a lower explosive limit of 3% v/v with mixtures being explosive up to 100%. Ethylene oxide explosions can cause major damage, as happened to Sterigenics in 2004; and so the ethylene oxide is diluted with an inert gas to make the mixture non flammable. Both carbon dioxide and chloroflorocarbons (CFCs) were used as the inert gas. Honeywell's Oxyfume 12 contained 12% EtO and 88% CFC-12, (Dichlorodifluoromethane) which was banned under the Montreal Protocol, its manufacture was banned in the United States along with many other countries in 1996 due to concerns about damage to the ozone layer.

CFCs were replaced with hydrochloroflurocarbons (HCFCs) and Honeywell introduced the oxyfume 2000 which contained 8.6% EtO in 91.4% HCFC-124 (Chlorotetrafluoroethane) and the Oxyfume 2002 which contained 10% EtO, 27% HCFC-22 (Chlorodifluoromethane) and 63% HCFC-124. The switch to the HCFCs was a temporary measure and they in turn are being phased out under the revised Montreal Agreement.

Market forces are also acting against the EtO blends which held a dominant market position before the 1990s. Honeywell estimates that more than 70 percent of hospitals in the United States have used Oxyfume in their sterilization facilities over the last 40 years. In 1993 Advanced Sterilization Products (ASP) launched its Sterrad hydrogen peroxide sterilizer which offered much shorter cycle times compared to the ~ 15 hours required for EtO sterilization and aeration and ASP's marketing emphasized the carcinogenic properties of EtO (even though the OSHA permissible exposure limits for EtO and hydrogen peroxide vapor are the same 1 ppm time weighted average over 8 hours).

The Sterrad system offered significant safety features, particularly by operating under reduced pressure (leaks will be in not out) and newer EtO sterilizers were introduced by 3M and Steris Corporation that also operated at reduced pressure and used single use cartridges. Both of these measures served to reduce employee exposure to EtO compared to the older pressurized systems. The single use cartridges uses a small quantity (100 - 170g) of 100% EtO and so do not use the HCFC blends and avoid the need to run gas lines and change EtO gas cylinders.

There has been a lot of confusion over the years about whether EtO was being phased out. It is not! It is the CFC and HCFC blend gases that are being phased our to protect the stratospheric ozone layer. EtO is still the major gas sterilant used by medical device manufacturers because it can be used for sterilization of almost all medical devices including plastic and heat sensitive materials.

EtO is not going away; the world production of EtO was 19 million tonnes in 2008 and 18 million tonnes in 2007 which places EtO as the 14th most produced organic chemical; and the amount of EtO used for sterilization is a minuscule fraction of this production. Even though EtO use in healthcare has dropped in the last two decades, there are still many hospitals that use EtO as for low temperature sterilization and it is likely that EtO will continue to be an important low temperature sterilant gas for the foreseeable future.

Monday, April 8, 2013

The Dangers of Formaldehyde Exposure in Beauty Salons and Healthcare

Formaldehyde is one the most widely used 'bad boys' of the chemical world, to use an expression favored by ChemDAQ's CFO. Formaldehyde is used, across many different industries, ranging from the production of amino (e.g. urea-formaldehyde polymers (glues & adhesives), melamine-formaldehyde (thermosetting rigid plastics), phenolic, and polyacetyl resins (engineering plastics), wood products, plastics, fertilizers and foam insulation; as a textile finish, preservative, stabilizer, and a disinfectant" [Merck Index, 12th Ed] to name just a few.

Formaldehyde is useful because of the wide range of chemical reactions in which it can participate. It is a strong reducing agent, it water soluble (formalin solution) and most importantly it is an alkylating agent and binds amine groups, and aromatic rings. These last properties are what makes formaldehyde useful in healthcare. Formaldehyde solution (formalin) is used as a fixative because it can cross link proteins and so fix tissue samples. It does the same thing in living organisms and so formaldehyde is strongly antimicrobial finding use as a disinfectant and sterilant (e.g. low temperature steam formaldehyde sterilization)

As with any chemical sterilant, formaldehyde poses significant risks to anyone exposed to it. Formaldehyde is a known carcinogen and causes cancer of the nasopharynx & sinonasal cancer and leukaemia. (IARC) and National Toxicology Program). It is also a sensitizer and a primary irritant [ATSDR].

These dangers are well known and OSHA has promulgated a standard for formaldehyde (29 CFR 1910.1048) and has set permissible exposure limits of 0.75 ppm (8 Hour time weighted average (TWA), and 2 ppm as a 15 minute TWA short term exposure level (STEL).

Formaldehyde is a very useful chemical, but it is often used in environments that are not set-up to handle chemical exposures. For example formaldehyde is often used in hair straightening formulations (similar chemical mechanism to the tissue fixative) and in the last couple years OSHA has targetted beauty salons, issued a press release a hazard alert and even created a website dedicated to the dangers of formaldehyde exposure in addition to citing them for violations of OSHA standards. However, most beauty salons have neither the equipment nor the training to protect their workers to the levels required by the OSHA standard.

The product manufacturers have been of marginal help, sometimes inadvertently leaving the formaldehyde off the product label ingredients, claiming that the levels are so low as to be safe or using one of the other chemical names for formaldehyde such as methylene glycol that is less easily recognized by those with limited chemical training. A much safer approach for both the salon workers and of course their customers would be to eliminate all formaldehyde from these applications.

Formaldehyde solution was widely used as a disinfectant and sterilant in healthcare, but in the US it has largely been replaced by glutaraldehyde as a liquid sterilant/high level disinfectant. Low temperature steam formaldehyde is still widely used in European and other countries in dedicated LTSF sterilizers. In the US formaldehyde is primarily used in health care as a tissue preservative and as a major component of embalming fluids.

Formaldehyde can be used safely provided that adequate safety precautions are taken. Employers using formaldehyde must provide the OSHA required Hazard Communication training for all workers using hazardous chemicals (29 CFR 1910.1200) as well as training on the formaldehyde specific standard.

Employers must ensure that their people are not exposed to formaldehyde concentrations over the OSHA PELs. Employers who use formaldehyde can do this by use of adequate engineering controls to prevent exposure, continuous gas monitors for formaldehyde to ensure that the other safety devices are sufficiently protective and provide warning to workers in something fails, suitable personal protective equipment and training on how to handle formaldehyde safety and what to do it things go wrong. These are similar to the requirements as for other sterilant and high level disinfectant chemicals such as ethylene oxide, hydrogen peroxide, peracetic acid, o-phthalaldehyde and glutaraldehyde.

Friday, April 5, 2013

ChemDAQ Steri-Trac® Monitors Saves Workers from Leaking EtO Sterilizer

We received a call from a hospital customer who said that over this past weekend, they had an ethylene oxide leak from one of their sterilizers and without the ChemDAQ Steri-Trac monitors no one would have known.

The leak arose because of an electrical fault in the scrubber and the entire exhaust system shut down, but there was no indication of this happening on any of their screens. The sterilizer was completing the cycle and when they opened the door, the ChemDAQ monitor alarms sounded and they were getting readings up to 50 ppm.

They immediately evacuated the department and were relieved they could see what was happening on the remote video display (RVD) outside the department.

If there had been no monitor they would have not known about the EtO leak and their people may well have been exposed to high concentrations of EtO.

Calls like this show the value of the ChemDAQ system and reminds us at ChemDAQ that our products are designed to save lives.

It also shows that even the best designed sterilization equipment can sometimes fail and that it is important to have a continuous gas monitoring system installed that will provide an immediate alert if there is a leak.

An automated alert is essential with ethylene oxide since EtO has no odor below about 400 ppm far above the OSHA permissible exposure limit of 1 ppm (8 hr time weighted average (TWA)) and the OSHA Excursion limit/15 minute TWA short term exposure limit of 5 ppm [29 CFR 1910.1047].

If anyone would like to share their story about sterilant gas leaks and/or detection of sterilant gases with continuous monitors, please fill out the comment box below.

Tuesday, April 2, 2013

Industry News - Recall of Sterrad 200 Sterilizers

The FDA published an announcement on March 30th that Advanced Sterilization Products (ASP) was recalling its Sterrad® 200 sterilizer. The recall was initiated because Advanced Sterilization Products (ASP) has determined that the STERRAD 100NX and STERRAD 200 Sterilization Systems may emit an odor or smell into the surrounding environment that is not typical to normal operating conditions.

While oil mists can be irritating, a major concern is that there may be hydrogen peroxide vapor in with the oil mists since the OSHA permissible exposure limit for hydrogen peroxide vapor is only 1 ppm (8 hr time weighted average).

A recent letter dated January 23, 2013 from ASP to a customer said that "the vacuum pump in the Sterrad 200 system may cause the emission of a slightly increased level of hydrogen peroxide (H2O2) vapor into the surrounding environment if not regularly serviced or replaced." The letter goes on to describe one incident where a healthcare worker experienced temporary eye discomfort and throat irritation while in close proximity to the sterilizer, due to emissions caused by failure of an internal filter.
There have been other reports of workers being exposed to hydrogen peroxide vapor and/or oil mist vapor from not only sterrad sterilizers but other brands and models of hydrogen peroxide sterilizer (see for example the FDA's MAUDE database.)

If you suspect that your sterilizer is emitting hydrogen peroxide vapor, then ensure that all personnel clear the area until the hydrogen peroxide concentrations are within safe limits as indicated by a hydrogen peroxide monitor; and follow the sterilizer manufacturer's instructions to get the problem corrected. If a hydrogen peroxide monitor is not available, use appropriate PPE and other measures to ensure that workers are not exposed.

If you have had any first hand experience of oil mists, smokes or hydrogen peroxide emissions from sterilizers (any make and model), we invite you to add a comment to this blog and describe your experience.