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Scientific Principles Underlying Decontamination


Water is an important and remarkable substance that makes all forms of life possible. Speculation about possible past or present life on other planets within our solar system, or any other extraterrestrial body somewhere within the universe, is conditioned on the evidence for or against the existence of past or present water or ice. Humans can and did survive and evolve without petroleum products, but cannot survive and evolve without water. Water is the most important natural resource. Human beings use water in virtually all spheres of their life. The use of water is conditioned by its peculiar properties. This paper examines the role water plays in the decontamination process with special reference to its physical and chemical properties.

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Decontamination is the physical or chemical method that makes an innate object that may be infected with harmful microbial life secure for further usage. The merits and problems associated with decontamination processes have been long-standing concerns within health care facilities (Block, 1991). Many of these concerns stem from the inability to control or identify all factors that make an item safe to handle. This is not surprising when one considers the variabilities in diseases and disease-causing processes and hundreds of soiled items reprocessed in health care facilities. Whether an item is safe to handle depends on parameters such as type and number of organisms on the device; susceptibility of individual employees to disease; and route of transmission.

Chemical and physical properties of water and their relevance in the decontamination process

Having gotten a hint on what decontamination is; this paper intends to turn focus into the role that water plays in this process? As mentioned earlier, the physical and chemical properties of water will be very instrumental in arriving at the contributions of water in the decontamination process. Water is the most abundant molecule on earth. Despite being so common, water is quite unusual –from its high melting and boiling points to its tremendous solvating power, high surface tension, and the largest dielectric constant of any liquid (Likens, 2010).

Knowledge of the structure of water is the basis for understanding its unique chemical and physical properties. Unique physical properties dictate how water acts as a solvent and how its density responds to temperature. These physical properties have strong biological implications. One of the many unusual properties of water is that it exists in liquid form at the normal temperature, and pressures encountered on the surface of the earth. Contrary to this, most compounds and elements, take the form of gas or solid in our biosphere except mercury and organic compounds (Bergethon, 2010).

The polarity of the water molecule and hydrogen bonding dictates the range of pressures and temperatures at which water occurs in a liquid state as well as additional, vital distinguishing characteristics. Since oxygen atoms attract electrons, the probability is greater than electrons will be nearer to the oxygen atom than the hydrogen atoms. The angle of attachment between the two covalent bonds, one for each of the hydrogen atoms attached to the atom, means a slight positive charge near the hydrogen atoms, to one side of the molecule (Bergethon, 2010). This unequal distribution of charge leads to each water molecule exhibiting polarity. The negative ion near the oxygen attracts positive regions near the hydrogen atoms of nearby water molecules resulting in hydrogen bonding. Hydrogen bonding becomes more prevalent as water freezes but also occurs in the liquid phase (Bennet & Morrell, 2006).

Without hydrogen bonding, water would exist as a gas at room temperature. In the decontamination process, water is used mostly in liquid or gaseous form. As such, the polarity of the water molecules enhances the formation of hydrogen bonding. This bond is responsible for maintaining the liquid state of water. The different detergents used in decontamination, especially in the cleaning phase need to be diluted. The liquid form of water becomes very useful at this stage. This is because as it shall be discussed later, water is a very good solvent. If there were no hydrogen bonds, water would have remained in the gaseous state, hence inhibiting its use as a solvent of the many detergents used in the decontamination process (Damani & Emmerson, 2003).

As hinted earlier, water is one of the best solvents known and can dissolve both gases and ions. The solvent properties of water have greatly influenced the decontamination process. Most solids dissolve in water readily as temperature increases. For instance, this effect on dissolved ions causes sugar to dissolve more quickly in hot than iced tea. Most compounds, but not all, have higher solubility at greater temperatures, as well. Conversely, the solubility of gases in water tends to decrease when temperature increases. This anomalous solubility of water has adverse effects on the decontamination process (Likens, 2010). For instance, due to the fact solubility of water in gases decreases with the increase in temperature, this implies that any increase in temperature does not lead to an increase in solubility. As such, steam used in the decontamination should remain at an ideal temperature if optimum decontamination is to be realized.

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Another stunning property of water is its ability to absorb high temperatures without a major temperature increase. This trend is witnessed in the summer sun at the beach where the scorching sun causes the sand on the beach to become so hot, yet the water temperature remains relatively cool. Both the water and the sand absorb the same amount of heat energy, however, the sand temperature is higher than the water temperature (Bergethon, 2010). This phenomenon is important in decontamination as it enables makes water to absorb the great heat energy needed to disinfect devices, but without destroying them due to high temperatures.

Specific functions of water in decontamination

The previous section of this paper discussed the safety measures that must be followed in the process of decontamination. Before examining the function of water in decontamination, it would be prudent to explore the different steps of the decontamination process. The first step is sorting. Sorting starts at the point of use. The amount of sorting that should occur depends on the setting. Handling of infected objects should be avoided unless whoever is using the device is incomplete personal protective clothing.

When workers at the point of use are wearing appropriate protective attire, sorting can include such activities as placing heavily soiled devices into a basin or container and covering them with a moist towel. It is crucial to keep blood or body fluids from drying on devices. Dried soil is more difficult to remove. The longer the soil is on the device, the difficult the cleaning process will be (Graham, 1988). Some facilities choose to begin the cleaning process for instrumentation during the transfer from the point of use by adding an enzyme presoak or detergent to the water in the container and making sure that the instruments are fully submerged. One should ascertain that devices can be submerged and that they are compatible with any detergents added to the water (Reichert & Young, 1997).

After the devices are sorted and soaked, the next step of the decontamination process is cleaning. Cleaning is the most crucial of all the steps in the decontamination process because, if sufficient cleaning is not done, the other steps will be rendered ineffective. Wiping with a detergent-dampened cloth is all that is required for safe reprocessing for patient care equipment including walkers, wheelchairs, intravenous fluid pumps, and sphygmomanometers. These items are not usually contaminated with blood or body fluids, hence; there is no need for them to be sterilized or disinfected for their intended use (Perkins, 1999).

For devices that have been contaminated by more intimate patient contact and that bear the biohazard label on arrival in the decontamination area, cleaning can be accomplished manually or by use of machines. Whenever feasible, cleaning by machines is preferable to hand-cleaning because it offers greater protection for the worker. Hand-cleaning requires manipulation of the device, and that offers an opportunity for glove and skin punctures and the possibility of disease transmission. Nevertheless, some devices cannot tolerate cleaning in automated machines, and many facilities do not yet have mechanical processes available in all areas where devices are reprocessed (Reichert & Young, 1997).

The process of washing in the decontamination procedure undoubtedly requires water. Regardless of whether one is hand-washing or using the machine, some basic principles should be followed. The first step should be a cool water rinse to get rid of gross debris. If the device is heavily solid with organic soil, or the soil is dried on, an enzyme detergent may be helpful as the step after the cool water rinse. When cleaning devices are soiled with organic matter, one should keep the temperature of the cleaning solutions below 140 degrees Fahrenheit. At higher temperatures, protein in the debris will coagulate, making it difficult to remove (Reichert & Young, 1997).

After rinsing the devices to get rid of gross debris, the next step is choosing a detergent compatible with the materials and suited for the soil. The device manufacturer should be consulted as to the recommendations as to the detergent. Detergents with pHs less than 7 are suitable for inorganic contaminants such as urine scales. Alkaline detergents with pHs greater than 7 are best suited for organic solutions such as blood, fat, and feces (Reichert & Young, 1997). Detergents should be low sousing and should freely rinse off without leaving a residue (Perkins, 1999). Manual cleansing, allows one to see the devices in the water. In mechanical washers, low-sousing detergents are needed to avoid fooling the pumps. In addition, the bursting bubbles of high-sousing detergents create more aerosol droplets that can carry microorganisms. Detergent residues can lead to staining and might hamper the action of some chemical disinfectants. Hand-cleansing should be performed in a sink with a drain stopper or a basin within a sink. Mechanical cleaning can be performed using ultrasonic cleaners, washer-decontaminators, washer sterilizers, pasteurizers, and automated endoscope processors. To conclude this section, it has been established that water is used in the decontamination process to rinse out deices with gross debris (Association of Operating Room Nurses (AORN), 1996).

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The selection of an appropriate decontamination procedure requires knowledge of available processes as well as knowledge of the material compatibility of the individual devices with selected processes (Wenzel, Brewer, & Butzler, 2002). Further, the selection is complex because of the hardships in identifying or controlling all the factors that make something safe to handle. There is no recognized standard for determining what constitutes safe to handle’. Therefore, the decision regarding appropriate decontamination processes becomes a risk/benefit analysis that must be made by the individual health care facility (Perkins, 1999). An object can be rendered ‘safe to handle’ by the physical removal of all contaminants. Unfortunately, no quantitative standards exist for cleaning procedures, and it is very difficult to assess the effectiveness in removing microscopic contamination. For manual cleaning procedures, the efficacy will be affected by the techniques and care used by the individual performing the cleaning operation (Reichert & Young, 1997).

Biocidal processes in decontamination

Even, though, the cleaning process could be categorized as almost completely efficient, there may still be many surviving organisms on the device after cleaning if high levels of bioburden were initially present. To minimize risks associated with potential microbiological contamination after cleaning, a biocidal process should also be sued. Biocidal processes used in health care facilities for decontamination can be classified as sterilization, disinfection, and sanitization. Sterilization enables the destruction of all forms of microbial life on objects (Damani & Emmerson, 2003). Sterilization processes are designed to kill large populations of highly resistant bacterial spores. These processes, therefore, provide a significant margin of safety because naturally occurring microbial populations have not been shown to provide the same challenge as the highly resistant spores (AORN, 1996).

Disinfection enables the destruction of pathogenic microorganisms. Generally, most people regard a disinfectant as a chemical agent, but some thermal processes should also be considered as disinfecting rather than sterilizing. Disinfection processes are intended to be effective agents representing groups of vegetative bacterial, pathogenic fungi, and specifically tested viruses. Disinfection does not afford the same mathematical assurance of efficacy as sterilization does and; consequently, does not give a similar safety margin (Association for the Advancement of Medical Instrumentation (AAMI), 1996).

Sanitization is a procedure able to rescue the number of microbial contaminants to a considerably safe level. Compared with sterilization and disinfection, sanitization provides the lowest margin of safety because it is not aimed at the complete destruction of any specific microorganisms. In general, sanitization is used for noncritical surfaces or for applications in which stronger microbial agents may cause device materials to deteriorate.

The best decontamination procedure is the use of heat, in steam form or hot water. Thus, Steam can be used to sterilize and provide significant margins of safety. Hot water at the right temperature and for adequate time has a very broad disinfecting effect. Both hot water and steam are inexpensive as compared with most chemical disinfectants. Steam and hot water are non-toxic if they are not applied to living tissue, and cause harm to the environment, as do many chemical agents. Unless the items to be decontaminated cannot withstand the temperatures associated with hot water disinfection or steam sterilization, thermal processing should always be used for decontamination purposes (AORN, 1996).

Items to be processed by thermal decontamination should first be subjected to a thorough cleaning process. This is best accomplished through the use of automatic equipment such as washer-sanitizers and washer-disinfectors, Washer sanitizers using saturated steam typically sterilize in the temperature range 121 degrees to 140 degrees Celsius (Booth, 1998). They are designed to wash, rinse, and sterilize efficiently most re-processable materials in the hospital such as surgical instruments, basins, trays, miscellaneous metalware, flasks, utensils, and other heat-and moisture-stable products. Washer-sanitizers use hot water in the temperature range of 60 degrees to 95 degrees Celsius. They are designed to efficiently wash, rinse, and thermally disinfect the same range of items as water-sterilizer, but because of the lower temperatures used, water-disinfectors are able to process a wider variety of items that may otherwise be deteriorated by the high temperatures of steam sterilization (Graham, 1988).

To make an appropriate choice of thermal decontamination equipment, one needs to consider the thermal resistance of the naturally occurring bioburden needs. If the object has a high bioburden level of high heat resistant organisms, there is a need for a high-level decontamination process such as sterilization. If the bioburden consists of relatively heat-sensitive organisms, a lower-level decontamination process such as disinfection is adequate. In most cases, the contaminating bioburden associated with hospital devices will be sensitive to hot water in the temperature range of 80 degrees to 100 degrees Celsius (Association for the Advancement of Medical Instrumentation (AAMI), 1996)

However, the big question lies in the action to be taken if the population level or heat resistance of the bioburden is unknown. The sterile medical device and drug industries have effectively dealt with this issue by using two distinctly different processing techniques. If the bioburden is not well characterized and controlled, an overkill process is used. In this process, an extreme amount of microbial lethality is delivered. However, if the manufacturer has sufficiently quantified the bioburden level and actively controls and monitors the bioburden’s level, a process known as bioburden methodology may be used. This process delivers less microbial lethality than the overkill process because the degree of lethality that provides the minimum safety level of microbial survival has been accurately determined (Morrissey, 1993).

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A recap of the role of water in decontamination and its inherent problems

Decontamination involves subjecting soiled devices to a number of processes which entail cleaning, disinfection, and sterilization. These processes will eliminate or obliterate micro-organisms and other contaminants. Water has an instrumental role in every phase of the decontamination process. After devices are sorted, cleaning is the next step before they are disinfected and sterilized. In cleaning, water is flushed on the devices to remove the gross contamination. Another function of water in the decontamination process is that it acts as a carrier for cleaning agents alongside being a suspension medium to prevent dislodged particulate contaminants from being re-deposited on clean surfaces (Perkins, 1999).

In thermal disinfection, the devices are exposed to moist heat; hence, water is also used here in the form of steam. Saturated steam provides a much greater margin of safety as a decontaminating agent when compared with hot water due to its physical and biocidal properties (AAMI, 1996). Steam is a vapor, and vapors have much greater penetrating capability than do liquids. Steam is far superior to liquid water in its ability to penetrate hinged regions or other small crevices associated with surgical instrumentation. Due to the latent heat of steam, steam has a much greater capacity for heating objects than hot water (Morrissey, 1993).

Although water is very important in virtually every step of the decontamination process, its unique properties make it sometimes problematic to be used in the process. To begin with, although it is almost considered the universal solvent, water does not dissolve all chemicals. This may a hindrance in the decontamination process. If a detergent to be used in the decontamination process is not soluble in water, then the worker has to find an alternative solvent, and this may compromise the quality of the process (Likens, 2010). In addition, as noted earlier, water has a very high heat-absorbing capacity; this implies that an increase in temperature does not translate to an increase in heat energy. This may imply that high temperatures may find use in the decontamination process yet, little heat energy is used. As such, some microorganisms may not die at this low temperature.


In conclusion, although water exhibits anomalous properties, it is very useful in the decontamination process. Decontamination is the critical step in breaking the chain of cross-infection between patient and patient and between patient and worker. Workers must be conscious of the risks involved with the handling of contaminated items and take appropriate protective steps. The myriad medical devices used in today’s health care require that processing involve the manufacturer of the devices, processing equipment, and processing supplies in making decisions about how to decontaminate particular items.

Reference List

Association for the Advancement of Medical Instrumentation (AAMI), 1996. Safe handling and biological decontamination of medical devices in health care facilities and in non-clinical settings. Arlington, Va: AAMI.

Association of Operating Room Nurses (AORN), 1996. Recommended practices for sterilization in the practice setting. Denver, Colorado: AORN.

Bennet, G., & Morrell, G., 2006. Infection control manual for hospitals. New York: HCPro.

Bergethon, P., 2010. The physical basis of chemistry: the foundations of molecular biophysics. Berlin: Springer.

Block, S. S., 1991. Disinfection, sterilization and preservation, 4th edition. Philadelphia, Pa: Lea & Febiger.

Booth, A. F., 1998. Sterilization of medical devices. London: Interpharm Press.

Damani, N. N., & Emmerson, A. M., 2003. Manual of infection control procedures. Cambridge: Cambridge University Press.

Graham, G. H., 1988. Decontamination: a microbiologist’s perspective. Journal of Healthcare Matters Management, 5(7): pp. 36-41.

Joint Commission on Accrediation of Healthcare Organizations., 2005. Infection control issues in the environment of care. New York: JCR Publications.

Likens, G., 2010. Biogeochemistry of inland waters. New York: Academic Press.

Mayhall, G., 2004. Hospital epidemology and infection control. London: Lippincott Williams & Wilkins.

Morrissey, R. F., 1993. Sterilization technology: a practical guide for manufacturers and users of health care products. Berlin: Van Nostrand Reinhold.

Perkins, J. J., 1999. Principles and methods of sterilization in health sciences, 2nd edition. Springfield: Charles Thomas.

Reichert, M., & Young, J. H., 1997. Sterilization technology for the healthcare facility, 2nd edition. New York: Jones & Barlett.

Spry, C., 2005. Essentials of peroperative nursing. New York: Jones & Barlett.

Wenzel, R., Brewer, T., & Butzler, J. P., 2002. A guide to infection control in the hospital. New York: PMPH-USA.

Wilson, J., 2006. Infection control in ambulatory care. New York: Elsevier Health Sciences.

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