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Gaseous decontamination using chlorine dioxide can scrub facilities of pathogens better than vaporized hydrogen peroxide
by Tyler Mattson
Food processing has existed for centuries, but in the 19th and 20th centuries, largely due to military supply demands, more modern food processing technologies were developed. As food processing needs have grown, so have problems with food contamination and foodborne illness.
Concerns about food contamination are increasing because of the large costs involved with the foodborne illnesses it causes. Health-related expenses brought about by foodborne illnesses cost an estimated $152 billion each year.1 The U.S. Centers for Disease Control and Prevention estimates that each year roughly one out of six Americans (48 million people) is affected, 128,000 are hospitalized, and 3,000 die from foodborne diseases.2 One factor contributing to the large number of cases of foodborne illness each year is the increased consumption of minimally processed foods and fresh foods.
As food travels from the environment to the consumer, it can become contaminated by many factors along the way, including irrigation water, wash water, food preparation environment, infected seed, production, harvesting, post-harvest handling, transport, distribution, storage, preparation, humans, and animals. A major issue is the number and diversity of pathogens involved in foodborne illnesses and food recalls. Of the 76 million cases that occur annually, only 14 million of these cases can be attributed to known pathogens.3
CD and VHP are oxidizers, but CD is not as aggressive an oxidizer as chlorine, ozone, peracetic acid, hydrogen peroxide, or bleach. Additionally, it is noncorrosive to common construction materials; VHP is 1.9 times more corrosive.
Some of the major pathogens that are known to be involved in the contaminations, foodborne illness outbreaks, and food recalls are Escherichia coli 0157:H7, Salmonella spp., Shigella spp., Listeria monocytogenes, Clostridium botulinum, Crytosporidium spp., Cyclospora spp., hepatitis A virus, and Norwalk-like viruses.
In recent years, detection methods and product tracking methods have improved, resulting in the recall of products that are or have the potential of being contaminated. The U.S. Food and Drug Administration (FDA) has begun an aggressive sampling program due to the development of the Food and Drug Administration Amendments Act of 2007.4
This act requires food manufacturers to report any instance when it occurs and to prove that their product is safe in the event that a recall is necessary. These recalls can be extremely costly for food industries. Recent years have seen some highly publicized and costly food contamination recalls. For example, during the summer of 2010, a massive egg contamination in a factory in Iowa resulted in 550 million eggs recalled, affecting 13 retail brands packaged by the egg factory.
The egg shells were contaminated with Salmonella, and more than 1,000 people were sickened. Not only did this cost the factory a lot of money, it also caused egg prices to increase dramatically.
Another devastating recall, involving ground beef in California, occurred last year when one million pounds of ground beef were pulled back due to an E. coli 0157:H7 contamination. It was the 12th recall of the year, totaling 1,786,859 pounds of meat recalled by the end of summer 2010. A recall near Thanksgiving 2010 involved New Braunfels Smokehouse in Texas; the firm recalled nearly 3,000 pounds of turkey that was likely contaminated with Listeria. In 2009, one recall involved at least 70 companies and more than 3,900 products.
The economic impact of this outbreak, caused by Salmonella-contaminated peanuts at a Georgia manufacturing plant, is estimated to be more than $1 billion. In 2008, a very large outbreak of what was thought to be Salmonella-contaminated tomatoes turned out to have originated in Mexican jalapeño and serrano peppers. By that point, the tomato industry had lost an estimated $100 million.5
In addition to the recalled product values, the direct hit to a facility will include, on average, a full quarter of profits for the recalled product, marketing to repair long-term brand damage, spillover negativity that reduces sales of other products, product liability claims, and the cost of restoring status within distribution channels.6
CD to the Rescue
Knowing the effect a food recall could have, many facilities have been increasing their sampling tactics to better detect contamination occurrences. Once contamination is detected, however, actions must be taken and might include a product recall. Because of the potentially catastrophic consequences, many facilities are improving their contamination prevention activities.
More washdowns and surface cleanings can help, but only a gaseous decontamination can really get into all the tight locations in a facility such as an egg-processing plant, meat-packing plant, or produce-handling facility, allowing for a complete kill of any contaminating pathogens. All decontamination methods function efficiently because of three important steps:
- Complete distribution;
- Thorough penetration, and;
- Sufficient contact time at a specified concentration with a sterilant.
The only two effective gaseous decontamination methods available are formaldehyde and chlorine dioxide (CD), but only CD is registered with the U.S. Environmental Protection Agency (EPA) as a sterilant process (EPA registration 80802-1). The formaldehyde process requires the heating of paraformaldehyde to release the gas, long contact times (usually six to 12 hours), and high concentrations to achieve a sporicidal outcome (10,000 ppm).
Gaseous CD has none of the drawbacks associated with the other decontamination methods. It can handle large areas and is compatible with the components, equipment, and finishings most commonly associated with food production facilities.
Also, formaldehyde is not capable of penetrating water to decontaminate either the water or the surface that any standing water may be in contact with. Furthermore, the residues left by formaldehyde, as well as its carcinogenic properties, make it an unattractive choice for areas where food is processed.
Vaporized hydrogen peroxide (VHP), applied as either a dry or wet process, is another fumigant commonly used for decontamination purposes. Like CD, VHP is registered with the EPA as a sterilant process—but only for small rooms and chambers. There are many issues involved with the VHP process within a facility. VHP is not a true gas at room temperature; therefore, it condenses as it cools, resulting in a temperature gradient. The point at which VHP is injected into an area is the hottest, and the vapor cools as it spreads farther away.
As VHP cools and condenses, it stops spreading and prevents full distribution throughout an area, altering the effectiveness of the decontamination process. Another problem with VHP is that the concentration increases from 35% to 78% as it condenses, resulting in a higher chance for corrosion and surface damage because of its oxidizing properties.7
CD and VHP are oxidizers, but CD is not as aggressive an oxidizer (oxidation potential data) as chlorine, ozone, peracetic acid, hydrogen peroxide, or bleach. Additionally, it is noncorrosive to common construction materials. In fact, VHP is 1.9 times more corrosive than chlorine dioxide, making it a potential health and cost risk for many of the materials in a production facility. VHP requires lengthier cycle times for the facility to be completely decontaminated and ready for use. Table 2 shows that chlorine dioxide gas is capable of decontaminating a much larger area in significantly less time.
Gaseous CD has none of the drawbacks associated with the other decontamination methods. It can handle large areas and is compatible with the components, equipment, and finishings most commonly associated with food production facilities. Like formaldehyde, it is a true gas at room temperature and is thus evenly distributed throughout the area being decontaminated by gaseous diffusion.
Gaseous CD saves time and, therefore, money. Often, washing procedures take place before a decontamination procedure. CD gas can penetrate through water, allowing for decontamination of the water and the surface the water is on without the need to physically dry the area. Furthermore, CD gas has very quick cycle and aeration times, allowing processing facilities to become decontaminated and fully functional in a shorter period of time.
Decontamination of a facility can be completed in one to three days depending on a facility’s size and complexity. Setup consists of sealing all of the possible leaks in an area such as windows, doors, vents, outlets, drains, and holes. Also, the building’s exhaust or HVAC system must be controlled in order to stop the CD gas from escaping and/or to exhaust the CD gas at the end of the decontamination cycle. If biological indicators (BIs) are required to further document the gas’s effectiveness, they are placed throughout the area by customer request. Then, quarter-inch sample and injection lines are run to many different points throughout the area so there is even sampling and dispersion of the gas during the decontamination cycle. Once the cycle is done and everything is cleaned up, the BIs are collected and properly evaluated, and the area can be turned back over to production.
Some facilities are implementing procedures to fumigate facilities on a yearly, semiannual, quarterly, or more frequent basis. These programs supplement the regular washdown procedures most commonly used.
With a washdown, the goal is to attempt to kill contaminating microorganisms. Regardless of the temperatures and/or types of chemical washes or sprays used, it is tough to completely rid an area of microorganisms. Several microorganisms are capable of surviving various challenging conditions due to mechanisms that they have developed to cope with some sanitizers, cleaning agents, and temperatures.
Ultimately, when microorganisms are not being completely removed, they can slowly build up their population and spread over larger areas, making the chances of a contamination—and, ultimately, a recall—much higher. Frequent use of CD for facility decontamination drastically reduces the chances of a contamination and/or a recall, because CD completely eradicates microorganisms from areas where potential contamination may occur.
Tyler E. Mattson is a decontamination specialist with Clordisys Solutions in Lebanon, N.J. Reach him at email@example.com.
- Scharff RL. Health-related costs from foodborne illness in the United States. Produce safety project at Georgetown University. March 3, 2010. Available 0at: www.producesafetyproject.org/admin/assets/files/Health-Related-Foodborne-Illness-Costs-Report.pdf-1.pdf. Accessed July 11, 2011.
- Centers for Disease Control and Prevention. CDC estimates of foodborne illness in the United States. CDC 2011 estimates: findings. Available at: www.cdc.gov/foodborneburden/ 2011-foodborne-estimates.html. Accessed July 11, 2011.
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- U.S. Food and Drug Administration. Guidance for Industry: Questions and answers regarding the reportable food registry as established by the Food and Drug Administration Amendments Act of 2007. FDA. September 2009. Available at: www.fda.gov/Food/GuidanceComplianceRegulatoryInformation/GuidanceDocuments/FoodSafety/ucm180761.htm. Accessed July 11, 2011.
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- Steris Corporation. Steris Case Study M1456, VHP Case Study 1. Hydrogen peroxide gas decontamination of material pass-through (MPT) room. LaboratoryNetwork.com. August 1999. Available at: www.laboratorynetwork.com/download.mvc/Hydrogen-Peroxide-Gas-Decontamination-Of-0001. Accessed July 11, 2011.
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