The Fragility of Hydrogen Peroxide Vapor

In April 2018, the Medicines and Healthcare Products Regulatory Agency issued a statement regarding the sterilization of direct and indirect product contact items within isolators*.  Specifically, the organization addressed the use of hydrogen peroxide vapor (VPHP) for the sterilization of direct and indirect parts and process’ overall fragility.  The agency mentioned how VPHP can fail due to very minor occlusions, with even the fatty acids from a fingerprint are able to shield organisms from VPHP.  The position paper built on this by considering that some product contact parts (both direct and indirect) are designed in such a way that makes it difficult for hydrogen peroxide vapor to penetrate them thoroughly.  They conclude that their stance is such that hydrogen peroxide vapor cannot be used to sterilize critical items.  The MHRA then states that their expectation is that contact parts are sterilized using a robust sterilization method that meets the current requirements of Annex 1 of the EU and PIC/X GMPS for the manufacture of sterile medicinal products.  They describe a robust sterilization method as one that “reaches all of the critical surfaces in a consistent and repeatable manner.”

To read the full post,  click here.

To learn more about how chlorine dioxide gas can help accommodate this application, sign up for our upcoming webinars on Isolator Decontamination and Comparing CD Gas vs. Hydrogen Peroxide Vapor taking place over the next few weeks.

*They define indirect product contact parts as those that come into contact with items and components which do contact the product (i.e stoppers). Direct contact parts are those that the product passes through, such as pumps and filling needles.

Decontamination Services & Applications: Life Science Industry

Chlorine dioxide (CD) gas can be utilized for a multitude of applications in the lab animal and life science industry. It is non-carcinogenic, residue-free, and safer on materials than bleach, ozone, hydrogen peroxide, and common liquid chlorine dioxide solutions. CD is not affected by environmental factors such as temperature, and is not subject to dew-point or condensation issues making it a versatile decontamination agent and allowing it to stay effective in all types of environments, including both ambient and vacuum pressure. Gaseous systems provide the ability to achieve a complete distribution and thorough penetration to each and every surface, including visible and invisible cracks and crevices. Some of the more common industry applications include animal holding rooms, BSL-3 and BSL-4 labs, biological safety cabinets, passthroughs, isolators, air handling units/ductwork, micro labs, and necropsy rooms.

Entire Facility Case Study:

ClorDiSys' chlorine dioxide gas technology allows for a complete decontamination of your facility, with minimal equipment and minimal downtime. A 170,000 ft3 new university research facility was decontaminated upon completion of construction and prior to the commencement of operations. Equipment and supplies were brought into the space as well, so that they would be exposed and decontaminated concurrently. ClorDiSys was able to fumigate the facility and eliminate any organisms present while providing sporicidal kill of Biological Indicators (comprised of 1 million Bacillus atrophaeus spores) to ensure the process was successful. The entire process took two days, one day for setup and one day for decontamination and clean-up.

BSL-3 Lab Case Study:

A BSL-3 influenza laboratory undergoes a yearly decontamination using chlorine dioxide gas during a facility shutdown. All equipment is left within the space during the process, as the gas is safe on materials and will reach all surfaces within the lab. This provided a large time savings as each piece of equipment did not need to be treated individually in an autoclave or other pass-through system. Results are shown through the placement of 40 biological indicators as various locations throughout the lab. Some locations include closed drawers, inside and behind biological safety cabinets, underneath tabletop equipment, as well as easy locations such as floors, ceilings and walls.

To learn more, attend our “Life Science and Pharmaceutical Facility Decontamination Services” webinar on Thursday, October 25th, visit Booth #1903 at the AALAS National Meeting in Baltimore, or visit our website’s Applications page.

Eradication of Pinworm Eggs with Chlorine Dioxide

Pinworms are common contaminants of laboratory animal facilities. Pinworm infections can have adverse effects on behavior, growth, intestinal physiology, and immunology of experimental rodents, making effective pinworm surveillance and eradication important for many facilities. However, eradication of such infections is complicated by the ova’s ability to aerosolize and remain viable in the environment for lengthy periods. Pinworm eggs are microscopic and have been found on equipment, shelving, in dust, and in ventilation air intake ducts. The University of Tennessee at Knoxville performed a study on chlorine dioxide gas’ effect on pinworm eggs to see if it was a viable option for treating contaminated spaces.

Prior to this study, only ethylene oxide gas and dry heat had been proven to eliminate pinworm eggs.  Ethylene oxide is not used for space fumigation due to its carcinogenic and explosive properties, and it is very difficult to uniformly establish and maintain the high temperatures needed for dry heat (212° F held for 30 minutes) to be effective. In a controlled study, Syphacia spp. ova were affixed to a slide and exposed to a set concentration of chlorine dioxide gas for varying amounts of time. After being exposed to chlorine dioxide gas, the ova were placed in petri dishes, covered with a hatching medium, and incubated at 37° C for six hours. Positive control ova not exposed to chlorine dioxide gas were also processed and incubated.

The parameters to achieve a 6 log level kill of viruses, bacteria, fungi, and spores are normally 1 mg/L chlorine dioxide gas (360 parts per million or ppm) for 2 hours of exposure contact time.  This equates to a 720 ppm-hours (360 ppm x 2 hours) chlorine dioxide gas dosage.  It was found that a dosage twice as long (1440 ppm-hour) was needed in order to eliminate all viable ova from hatching. All ClO2 treatment times significantly decreased the hatching rates of the ova. Below is a table showing the results of the study: 

Exposure time	Chlorine DioxideGas Dosage	% of Syphacia, spp. ova hatched
		Treated with CD Gas	Untreated(Positive Control)
1 hour	360 ppm-hour	14%	71%
2 hours	720 ppm-hour	12%	82.5%
3 hours	1080 ppm-hour	2%	80.5%
4 hours	1440 ppm-hour	0%	83%

To learn more about gaseous chlorine dioxide's effectiveness against pinworm eggs, visit Booth #1903 at this month's AALAS National Meeting or read the complete Journal of the American Association for Laboratory Animal Science article here.

Case Study: Electron Microscope Decontamination

An electron microscope can be used to study dangerous biological organisms. Occasionally, the organism can be sucked into the internals of the microscope making it hazardous to repair with concern for the maintenance technician’s health. To mitigate these concerns, decontaminating the inside components of the microscope can be accomplished using gaseous chlorine dioxide with no adverse effect on the equipment.

The normal sterilization process is automated and consists of 5 steps:
1. Precondition: Raising of humidity to make spores susceptible to gas
2. Condition: Holding of raised humidity level for spore softening
3. Charge: Injection of gas into chamber
4. Exposure: Holding of gas concentration for the set amount of time
5. Aeration: Expulsion of gas and humidity

Some microscope manufacturers add a sixth step which is a pre-purge of the system with nitrogen. If a Pre-Purge step is used, the valves are opened and nitrogen is passed through the system.

In 2009, ClorDiSys was approached by JEOL USA as they set forth to find a suitable decontamination method for their electron microscopes. They wanted a method to decontaminate the interior chambers to protect their service workers from the pathogens being studied within. Identical sets of parts were sent for material testing against chlorine dioxide and hydrogen peroxide vapor. According to “Construction and Organization of a BSL-3 Cryo-Electron Microscopy Laboratory at UTMB” in the December 2012 Journal of Structural Biology, their early attempts to use VHP with JEOL microscopes were not successful because of unacceptable level of corrosion of some parts inside the microscope column. Some showed visible discoloration and corrosion after the level of exposure necessary for a single decontamination cycle. Chlorine dioxide gas has a lower oxidation potential than ozone, peracetic acid, bleach and hydrogen peroxide, making it scientifically less corrosive than those other decontaminating agents. Our chlorine dioxide gas was selected due to its success in the material compatibility trials and is used with the $3 million TEM.

Read more about the process and benefits of using chlorine dioxide for Electron Microscope decontamination in our application note.