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BIOLOGICAL HAZARD (BIOHAZARDZ)
Transcript of BIOLOGICAL HAZARD (BIOHAZARDZ)
Biological hazards, also known as biohazards, refer to biological substances that pose a threat to the health of living organisms, primarily that of humans. This can include medical waste or samples of a microorganism, virus or toxin (from a biological source) that can affect human health. It can also include substances harmful to animals.
AGENTS AND SOURCES
Bacteria are simple, one-celled organisms, They are not visible to the eye and they multiply by simple division. Not all bacteria are harmful; many are useful. Bacteria are charaterized by their shape: cylindrical or rod shaped (bacilli), shaped like a string of beads (cocci), and spiral or corkscrew shaped (sprilla).
A virus is an organism that depends on a host cell for development and reproduction. Viruses are parasitic and are so small that they are not visible with an optical microscope. Viruses are transmitted in many ways, including contact with infected people, from animals and insects, om contact with equipment and diseased specimen, and other means.
There are many species of fungi. They are parasitic and grow in a living host or on dead plant or animal matter. Fungi may be microscopic in size or large (mushrooms are an example).
Rickettsia are microorganism that are rod shaped and smaller than bacteria. They depend on a host for development and reproduction and they must live within a host cell. Fleas, ticks, and lice transmit them, although they are sometimes airborne.
A variety of protozoa, helminths, and arthropods are parasites. They are different from other organisms that are parasitic because they live in or on other plants or animals. Some well-known parasites are tapeworms, liver flukes, and hookworms.
Bloodborne pathogens are microorganisms that are present in human blood and can cause disease in humans. Examples are the hepatitis B virus and the human immunodeficiency virus. OSHA established a standard addressing safety and health of workers subject to potential bloodborne pathogen exposures.
Sources of Biohazards
Diseases transmitted from animals to humans, zoonoses, are a major source of biohazards.People who work with animals, animal products, or animal waste have a greater risk of infection from biohazards. Another source of biohazards is work in hospitals, other medical facilities, or medical-related research laboratories. It may include any situation in which someone can contact the blood or body fluids of someone else, such as in an accident, first
aid situation, or work with patients or hotel guests, cleaning of waste receptacles or washrooms and so forth. Exposure can be from equipment and materials contaminated with blood, such as needle sticks, handling of linens during laundry, or waste.
The main danger from biohazards is infection, and there are different symptoms for different infections. There is considerable knowledge about infections from some biohazards. However, it must be assumed that a biohazard exists for work with biological agents or related materials for which disease is not known or not understood. Biohazard agents may enter the body or skin by ingestion, skin contact, puncture wounds, or inhalation of aerosols. Infections from some biohazards can be cured or at least treated. For some infections, there is no treatment or cure.
1 Agents of no hazard or minimal hazard under ordinary handling conditions that can be
handled safely without special apparatus or equipment, using techniques generally
acceptable for nonpathogenic materials.
2 Agents of ordinary potential hazard that may produce disease of varying degrees of severity
through accidental inoculation, injection, or other means of cutaneous penetration, but
which can usually be adequately and safely contained by ordinary laboratory techniques.
3 Agents involving special hazard that require special conditions for containment or require a
USDA permit for importation and are not in a higher class.
4 Agents that are extremely hazardous to personnel or can cause serious epidemic disease and
require the most stringent conditions for containment. Included are certain types of class 3
agents imported into the United States.
5 Foreign animal pathogens that are excluded from the United States by law or whose entry is
restricted by the USDA.
TABLE 26-2 Classification of Biohazards
One can prevent many occupational infections with training, procedures, and special equipment and facilities. This is particularly true for laboratories involved with infectious agents. The U.S. Department of Health and Human Services, Public Health Service, developed guidelines for preventing laboratory infections. The principles they developed are helpful in assessing risk and preventing infections in other activities.
The overriding principle for preventing laboratory infections is containment, the purpose of which is to reduce exposure of laboratory personnel and other persons to potentially hazardous agents. Containment includes preventing escape of potentially hazardous agents outside the laboratory to such persons as workers laundering laboratory clothing, visitors, and family members of laboratory workers. The three elements of containment include laboratory practice and techniques, safety equipment, and facility design. Primary containment addresses protection of personnel and the immediate laboratory environment from exposure, which is achieved with proper techniques and safety equipment. Vaccines may provide additional protection for personnel. Secondary containment refers to protection of environments outside the immediate laboratory, which requires both proper procedures and facility design.
Warnings that laboratories and containers have biohazards are important. The biohazard symbol is an essential part of a biohazard warning. Several organizations have biohazard warning requirements and standards.
Laboratory Practice and Technique
Laboratory workers must learn what hazards exist for particular agents in a laboratory and must receive training in proper handling and operations of laboratory materials. Workers must periodically update their knowledge and skills to ensure high retention levels. There should be an operations and biosafety manual for each laboratory that identifies hazards that may be encountered and what protection is needed for these hazards. Persons knowledgeable in hazards, safety procedures, and laboratory techniques should direct the work. Knowledgeable people should complete a risk assessment before starting any work to identify dangers and to implement appropriate protection.
Biosafety related to laboratory work extends into criminal laboratories and the investigator and laboratory personnel handling and analyzing criminal evidence. Specialists in this field are becoming more concerned with safety in their work with biological materials from crime scenes.
Enclosed containers, biological safety cabinets, and personal protection equipment are the main kinds of safety equipment. Safety containers prevent release of unsafe substances during normal activities and operations. An example is a safety centrifuge cup. Biological safety cabinets are partial or full enclosures where the air flow is designed to retain agents within the cabinets. There are three classes of cabinets.
biological safety cabinet has an open front. Air moves inward across the face at 75 ft/min and exhaust air is filtered through high-efficiency particulate air (HEPA) filters.
biological safety cabinet also has an open front with a 75 ft/min face velocity.
It has vertical laminar flow air movement and the air is both HEPA filtered and recirculated within the cabinet and HEPA filtered and exhausted. The filtered recirculation prevents contamination of agents by air drawn into the cabinet. Class II cabinets must meet the National Sanitation Foundation standard.
biological safety cabinets are totally enclosed. Workers complete activities in the cabinet via rubber gloves built into the cabinet walls. To prevent contamination of the contents, supply air enters the cabinet through HEPAfilters. The cabinet operates under at least 0.5 in of water-negative pressure. Exhaust air moves through two stages of HEPA filters. Typically, a Class III cabinet has its own exhaust fan, which is independent of any other ventilation systems. Other equipment, such as refrigerators, dunk tanks, and centrifuges, is a part of the cabinet or is contained in the work area within the cabinet.
One can achieve Class III standards another way. Workers wear one-piece, positivepressure, full-body protective suits that have a life support system and work inside Class I or II cabinets. In this case, the work area must have an airlock with airtight doors. Workers must pass through a chemical shower to decontaminate the suit before leaving the work area. Exhaust from the suit must pass through a two-stage HEPA filter.
Facilities play an important role in containment. Designs protect both those working in a facility and those outside the laboratory and the surrounding community. There are three classes of facility design, each providing a different level of safety. The three facility classes are basic, containment, and maximum containment laboratories. Design features are based on four levels of biosafety for infectious agents and for work with vertebrate animals. Tables 26-3 and 26-4 summarize the four biosafety levels. Designs include easily cleaned surfaces, special features for furniture, cleaning facilities for workers, and other features.
Basic laboratories are intended for work with agents not associated with disease in healthy adults and work in which standard laboratory practices provide adequate protection. Separate basic laboratories from public and office areas. Containment equipment is not normally required.
A major feature of a containment laboratory is a controlled access zone. Containment laboratories have specialized ventilation systems and may be separate buildings or controlled access modules within a building.
Maximum containment laboratories support work with agents that are extremely hazardous or may cause epidemics. Often these laboratories are separate buildings. Amain design feature is highly effective barriers, which may include sealed openings, airlocks or liquid disinfectant barriers, clothing-change and shower rooms, double-door autoclave, biowaste treatment system, separate ventilation system, and treatment system to decontaminate exhaust air.
Another control to reduce the dangers of contact with biohazards is the use of robotics for analysis and processing of biological samples. A robot placed in an enclosure can perform many functions, thereby reducing human handling and potential contacts. Automatic or manual controls operated from outside the enclosure direct the actions of the robot. There are companies that produce robots for processing biohazards.
Sick building syndrome is a term from the 1980s. It stems from a number of incidents where many occupants of an entire building or a certain portion of a building exhibited a rash of physical complaints, including headaches, muscle pains, chest tightness, nausea, fever, cough, allergic asthma, allergic rhinitis, pneumonitis, and pneumonia. Often the symptoms diminished over weekends. Some individuals became sensitized or exhibited allergic reactions to conditions. ASHRAE defines the term sick building as a building in which a significant number (more than 20%) of building occupants report illnesses perceived as building related.
SICK BUILDING SYNDROME AND INDOOR AIR QUALITY
In the 1950s, researchers discovered the double helix of deoxyribonucleic acid (DNA), the building block of life. Since then, research has mapped the complete DNA molecule and many companies work with modified DNA molecules. Genetic engineering, cloning, and gene splicing are becoming common and in some cases commercialized. In 1980, the U.S. Supreme Court decided that a live, laboratory-made microorganism is patentable. This decision let stand a lower court decision for the first patent on genetically engineered materials. The patent recognized a General Electric product—an oil-eating organism.
Genetic engineering, gene splicing, and cloning led to public fears about modifying DNA. Modified organisms, plant, and animal species produced in error or for destructive purposes made some people fear incidents similar to the black plague of the Middle Ages and the worldwide influenza epidemic of 1918 that killed 20 million people. The National Institutes of Heath (NIH) developed guidelines for recombinant DNA research8 and a review committee assesses potential hazards of proposed research. Genetic engineering has produced biological growth of insulin, interferon, and bacteria capable of digesting 2,4,5-T, the key chemical component in Agent Orange. Other useful products have also emerged from biotechnology research.
A major control to prevent dangerous releases of new organisms is careful review by government agencies, such as the EPA. There are few methods for evaluating the safety of genetically engineered products. Risk analysis techniques are useful.
There are many other ways biohazards can threaten people in daily living and in special environments. Biohazards in the food chain threaten many people. Biohazards in hospitals require careful control to prevent transfer in infections and disease
OTHER BIOHAZARDS AND CONTROLS
Biohazards enter the food chain at many points. For example, a natural bacterial growth in corn stored in grain bins and elevators can produce a toxic substance called aflatoxin. Farmers, grain elevators, and grain companies must monitor corn for this toxin. Some seasons have a greater problem than others. The U.S. Department of Agriculture has numerous standards for and conducts inspections on grain and other food materials. These standards and other controls ensure that plant and animal foods pose little risk of biohazards for consumers. The Department of Commerce has standards for fish and seafood products. The Food and Drug Administration sets standards on food for human consumption and food for animals intended for human consumption.
State and local governments have public health inspectors who regularly inspect restaurants and related food establishments. Regulations require workers to handle, refrigerate, and process food properly for customers. They also prevent spread of biological agents by insects and rodents through sanitary practices. Establishments that do not meet inspection standards must resolve deficiencies or face temporary or permanent closure. A major problem in food preparation and service at restaurants and hotels is ensuring that employees wash their hands and adhere to other basic sanitation practices.
Restaurants and Food Establishments
Federal regulations for construction of medical facilities include features that help minimize hazards of biological agents. State regulations and certification programs for medical facilities also help establish controls to minimize dangers of biological agents. The American Hospital Association and other healthcare organizations have their own guidelines to assist operators of facilities to minimize biohazards and any resulting infections.
Hospitals and Other Health Care Facilities
A variety of public facilities create opportunities for transfer of biohazards; proper design, operation, cleaning, and maintenance are important in controlling biohazards. Each recreational facility may have other safety and health hazards requiring additional controls. Water in swimming pools becomes contaminated by microorganisms from swimmers’ skin, mucus, feces, and urine and from dirt, plant material, and other sources. The water must be cleaned and disinfected. Recirculation systems pump water through filters to remove hair, lint, and other large particulates. Filters are backwashed to clean them and the collected materials are flushed down sewer lines. Chlorine and other chemicals are used to disinfect the water. The rate of filtration and disinfecting is based on swimmer load and tests of water samples. There are state and local codes for operation of public swimming pools, and there are many sources of criteria for design of large pools. Spas, therapy pools, hot tubs, and similar water containers that have multiple uses require treatments similar to swimming pools. Simply draining the containers, flushing out solids, and scrubbing them regularly with disinfecting detergents will prevent transfer of biohazards. Other recreational facilities that many people use require care in preventing transfer of biohazards. Cleaning, disinfecting, and other means can be effective.
Swimming Pools, Spas, Saunas, Therapy Pools, and Tanning Booths
The implementation of sanitary sewer systems removed many kinds of biohazards. State and local governments have plumbing codes, codes for sanitary sewer systems, and codes for water supply systems. In many locations, plumbing and sanitary lines must be inspected when they are initially installed or modified. Strict code enforcement prevents potential disease transfer. Careful separation of potable water from untreated water supplies and sewer lines prevents any cross-contamination or back flow to the potable water. Ventilation and dehumidification in closed spaces can help prevent the growth of molds. Treatment of standing water in air conditioning equipment also can minimize the opportunity for molds to grow.
Plumbing, Sanitary Sewer Systems, and Water Supplies
1. What are the five kinds of biohazard agents?
2. What are zoonoses?
3. What is the main danger from biohazards?
4. What are the four classes of biohazards in order of hazard severity?
5. What are the three major types of controls for biohazards in laboratory work?
6. Characterize class I, class II, and class III biological safety cabinets.
7. Define sick building syndrome. What symptoms do people typically exhibit with
sick building syndrome? What agents are commonly involved?
8. What are potential hazards for genetic engineering? What controls are there?