Decontamination methods
Decontamination methods refer to the chemical and physical procedures used to eliminate, inactivate, or clean potentially harmful biological, chemical, or radiological agents from people, objects, surfaces, and buildings. The significance of these methods arises from the risks posed by exposure to such agents, which can occur in various environments, including homes, workplaces, and healthcare settings. Effective decontamination is essential for preventing the transmission of infectious diseases and ensuring the safety of individuals who may encounter these hazardous substances.
Decontamination strategies are categorized into two primary types: chemical and physical. Chemical methods involve the use of disinfectants, such as alcohols, bleach solutions, and aldehydes, tailored to the specific contaminants and materials being treated. Physical methods include techniques like scrubbing, ultraviolet light application, and heat sterilization, which help eliminate pathogens without the use of chemicals. Various protocols exist based on the context, such as specific practices for handling biological agents in clinical settings or addressing chemical spills in industrial environments.
Given the heightened public concern surrounding the potential use of hazardous agents as weapons, the development of effective decontamination techniques has gained increasing importance. These methods are not only crucial for military applications but also have been adapted for civilian use in response to contemporary threats. Understanding these decontamination methods is vital for professionals and the general public to mitigate the risks associated with hazardous exposures.
Decontamination methods
DEFINITION: Chemical and physical methods of eradicating, inactivating, or cleaning potentially dangerous biological, chemical, or radiological agents that are present on persons or objects, including surfaces and building structures.
SIGNIFICANCE: Exposure to certain kinds of biological, chemical, and radiological agents can be detrimental to human beings. Forensic scientists as well as members of the general public may find themselves in situations where they may be exposed to such agents, thus decontamination procedures need to be in place. Such procedures include removal of contaminants, prevention of infectious transmission from biological hazards, reduction of contaminant levels to ensure protection from harm, and provision of decontaminated objects or surfaces that are safe for use, handling, storage, or disposal.
Exposure to various hazardous agents can take place in the home, in the workplace, or in other environments. For example, workers in health care institutions and in laboratories of many kinds (forensic, clinical and research) are often exposed to bloodborne pathogens and other potentially infectious materials. Individuals who work in manufacturing industries are also often exposed to potentially toxic chemicals specific to their work environments. In addition to such everyday exposure, public concern has risen regarding the prospect of the use of chemical and biological agents as weapons. A radiological (nuclear) agent was last used as a weapon in World War II, but such agents are also present in nuclear power plants, in some weapons manufacturing plants, and in small quantities in forensic, clinical, and research laboratories when particular experiments require them. Forensic scientists may be exposed to biological, chemical, or radiological agents in the course of their work.
Because of the dangers of exposure to hazardous agents, the issue of decontamination is increasingly important. Decontamination methods include two broad categories: chemical and physical. Specific cleaning and decontamination procedures apply to different situations. For example, different methods of cleaning and decontamination would be used for a crime scene, for an operating room in a hospital, for a patient examination room in an outpatient clinic, for a blood bank, for a research laboratory, and for a facility exposed to a biological or chemical war agent, such as the anthrax-laden letters that contaminated the Hart Senate Office Building and the associated US Postal Service mail-handling and -sorting centers in the fall of 2001. Moreover, specific protocols are in place in the United States for decontaminating civilians as opposed to military personnel in military settings, where quick and efficient strategies need to be employed. The choice of decontamination methods depends also on the severity and consequences of the exposure and on the nature of the item that will be decontaminated, including the material of which it is made.
General Methods
The US Occupational Safety and Health Administration (OSHA) recommends several general measures of decontamination. Hand decontamination by completely washing hands with soap and water, rinsing, and drying with a clean towel or air-drying can help prevent transmission of disease. This method is useful in many different settings, including food-related industries, health care institutions, and forensic laboratories. Hand washing was one of the first means of stopping viral spread during the global COVID-19 pandemic in 2020.
Clothing, tools, and appropriate equipment should be washed completely using soap and clean water. A solution of chlorine bleach (sodium hypochlorite) and water (one-fourth cup of bleach per gallon of water) should be used to wipe down surfaces; gloves, eye protection, and appropriate clothing should be worn by those using bleach solutions for decontamination.
Chemical Methods
Chemical disinfectants that are often used in medical, surgical, and research facilities include alcohols (isopropyl and ethyl alcohol, usually 70 percent solutions, are used to inactivate biological hazards, including adenoviruses, murine retroviruses, and human immunodeficiency virus, or HIV); halogen-containing compounds such as iodophors (iodine combined with an organic substance); oxidizing chlorine solutions such as bleach (a 10 percent chlorine solution made fresh daily is recommended); phenolic compounds such as chlorhexidine; strong bases such as calcium, sodium, and potassium hydroxides; mild acids such as vinegar; surface-active compounds such as soaps and detergents (quaternary ammonium compounds commonly known as quats); and aldehyde compounds such as glutaraldehyde and formaldehyde.
The necessary length of exposure to these chemical decontaminating agents depends on the level of disinfection required (low, medium, or high) as well as the limitations of each situation (for example, the nature of the item being disinfected is a factor, whether it is a sample containing bloodborne pathogens or other potentially infectious materials, the surface of a laboratory workbench, or a soft surface such as a carpeted area). One type of chemical decontamination used in involves dichloromethane. Forensic investigators often obtain samples of (deoxyribonucleic acid) from hair, teeth, body fluids, and fingernails. Hair is usually decontaminated with dichloromethane for two minutes before extraction of DNA. In addition to the chemical decontamination, most of these objects are placed in specially designed biohazard bags or containers for disposal; these are then sterilized using an autoclave, a device that employs heat, steam, and pressure to destroy biological pathogens.
Chemical disinfectants that may be used for decontamination of building structures in cases of toxic industrial events or biological or chemical attacks include three broad categories: liquid-based topical agents (such as bleach and aqueous chlorine dioxide), foams and gels (such as the L-Gel System and a decontamination foam created by Sandia National Laboratories), and gaseous and vapor technologies, or fumigants (such as chlorine dioxide gas, vapor-phase hydrogen peroxide, and paraformaldehyde).
The L-Gel System is an innovative decontaminant of biological hazards as well as of chemical and biological warfare agents, such as the spores of Bacillus anthracis, the bacterium that causes anthrax. L-Gel, which was developed at the Lawrence Livermore National Laboratory in California, is based on a Du Pont Corporation product called Oxone, a commercial oxidizer that uses potassium peroxymonosulfate as its active ingredient. L-Gel incorporates Oxone solution and a silica gelling agent, which allows it to cling to walls, ceilings, and other surfaces.
The decontamination foam developed at the Sandia National Laboratories in New Mexico, known as Sandia foam, uses aqueous-based hydrogen peroxide as its active ingredient. Sandia foam can also eradicate bacterial spores through its surfactant and oxidizer properties.
Radioactive material contaminants, especially from water-cooled nuclear reactors, are decontaminated with chemical reagents. For example, alkaline permanganate is used for pretreatment, citrate-oxalate solution for treatment, acidified hydrogen peroxide solution for posttreatment, and demineralized water for rinsing in between steps.
Radioactive contamination from spills that occur in laboratories is usually minor and easily contained. Exposed personnel are decontaminated using the protocols in place for such events. Chemical decontamination methods include using soaps or detergents with chelating compounds and special decontaminants for radioactivity, such as Decon90, Count-Off, and Radiacwash. For personnel decontamination, hydrogen peroxide, potassium permanganate, and sodium metabisulfite can be used for decontamination of exposed skin, provided there are no wounds and the skin does not become inflamed or irritated. If radioactive material is ingested, vomiting is induced and copious amounts of water are given to dilute the radioactivity. Most institutions where radioactive materials are present have environmental health and safety officers and radiation safety officers who are responsible for reporting radioactive contamination incidents and for more extensive decontamination per institutional protocols.
Most of the decontamination technologies developed in the United States for use in case of biological, chemical, and radiological attacks have been developed for military purposes, but these technologies and their potential uses have been expanded to include civilian purposes since the events of September 2001, when the United States experienced on a scale that it had never before seen.
Physical Methods
Physical methods of decontamination range from simply scrubbing off microbes with an antimicrobial to more sophisticated methods, such as the use of ultraviolet (UV) light, ionizing radiation, microwave irradiation, absorbents, filtration, dry heat, and moist heat (steam). UV light is often used to cause mutation experimentally; its main application as a decontaminant is in laboratories that use hazardous microbes and in irradiation of air near important surgical sites. Ionizing radiation includes electron beams, X rays, cathode rays, and gamma rays; these have greater energy than UV light. Ionizing radiation is often used in industrial processes such as the sterilization of disposable medical and surgical supplies. Microwave irradiation has been used to sterilize items such as sponges and scrub pads.
Absorbents are natural materials, such as fuller’s earth, that can take up liquid contaminants or impurities. An absorbent used by the military is M291, a dried resin used for rapid decontamination of the skin. Research has found that immediate dry decontamination can be effective as a first response to chemical contamination until wet decontamination can be performed. Filtration is a method of sterilizing large volumes of liquid to remove contaminants by passing the liquid through one or more filters. Dry-heat sterilizers are often used to disinfect instruments that can withstand high temperatures. Moist heat (steam) is used in autoclaves to sterilize equipment, liquids, and other objects. Some bacteria that form spores (such as those that belong to the genera Bacillus and Clostridium) cannot be completely eradicated by autoclaving because the spores can survive extremely high pressures and temperatures.
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