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32 OCCUPATIONAL HEALTH AND SAFETY OF RESEARCH-ANIMAL WORKERS 3 Physical, Chemical, and Protocol-Related Hazards The diversity of physical, chemical, and protocol-related hazards associated with animal research is tremendous. Animals bite, scratch, and kick; moving bulky animal cages can result in sprains and strains; and electricity, machinery, and noise can cause injury. Chemicals are ubiquitous in the laboratory and animal room environments; chemicals are used to disinfect and clean surfaces, anesthe- tize animals, and process tissue samples. Research protocols can introduce toxic chemicals, human pathogens, or radioactive materials into animals, and these agents can enter the waste stream of the animal facility. This chapter provides a brief review of specific physical, chemical, and protocol-related hazards that are commonly observed in animal care and use programs. PHYSICAL HAZARDS Animal care and use by their very nature present many situations that require safe practices to protect workers from physical hazards. The hazards of bites, kicks, and scratches are associated inevitably with most laboratory animal con- tact. A survey of animal-related injuries among veterinarians indicated that 35% required sutures for lacerations during their career. Working with heavy animals and equipment, such as metal cages, can stress muscles and joints. The potential for wet floors in animal rooms and cage washing areas increases risks of slipping and falling. Workers can also be exposed to physical hazards that are commonly found in the research environment, such as flammable solvents, ultraviolet radia- tion, ionizing radiation, pressure vessels, noise, and electric shock. The physical 32
PHYSICAL, CHEMICAL, AND PROTOCOL-RELATED HAZARDS 33 hazards selected for discussion in this section present the highest potential for causing serious harm and are likely to be present in most animal facilities. Animal Bites, Scratches, Kicks, and Related Hazards Bites, scratches, and kicks are ubiquitous hazards associated with laboratory animal contact. They are largely preventable through proper training in animal- handling techniques. People working with large domestic animals might sustain crushing injuries when the animals kick, fall, or simply shift their body weight. Personnel should be aware of environmental factors, as well as factors intrin- sic to the animal, that can precipitate a traumatic event in a research animal facility. Several factors need to be considered in work with animals (Grandin 1987). Animals respond to sounds and smells as people do; they also hear, smell, and react to things that people might not detect. If an animal hears a high-pitched sound, it might become frightened. Such situations can result in an unexpected response that results in injury to the animal handler. Many animals have a âflight zoneâ: approaches by another animal or a person cause an attempt to escape. Being aware of an animalâs flight zone will help to avoid injuries. Many animals, including monkeys and livestock, are social and show visible signs of distress if isolated from others of their kind. Knowledge of animal behavior is important in reducing risks. Inappropriate handling can induce discomfort, pain, and distress, provoking an animal to inflict injury on its handler. Personnel should review educational materials pertinent to safe animal-handling techniques (Fowler 1986; Kesel 1990) and should have supervised instruction before undertaking new animal-handling procedures. The institution should be prepared to evaluate the causes of any injuries that result from newly adopted procedures. The injured persons should participate in this evaluation. Special attention should be given to the training of personnel involved in the handling and restraint of nonhuman primates. In addition to posing a bite and scratch hazard, nonhuman primates can be challenging and difficult to handle safely because of their great strength, dexterity, intelligence, and tenacity. Unsus- pecting personnel have been injured when nonhuman primates have grabbed and pulled neckties, loose-fitting laboratory coats, or long hair, and some individual great apes have been known to throw their feces. When it is compatible with the experimental conditions of animal use and the clinical condition of the particular animal, consideration should be given to chemical immobilization of nonhuman primates to facilitate the ease of handling them and to reduce the risk of injury of personnel. Personnel who work with nonhuman primates should wear face shields and other protective garments and equipment appropriate for the circumstances and species involved. In a survey of animal bites among the general population, dogs were the species most commonly involved, with cats and rodents second and third (Moore
34 OCCUPATIONAL HEALTH AND SAFETY OF RESEARCH-ANIMAL WORKERS and others 1977). Comparable data on bites in animal facilities are not available, but rodent bites probably predominate because of the large number of rodents used and the broader exposure of personnel to them. Animal bites, especially those by rodents that inflict little tissue damage, are sometimes considered inconsequential by personnel who are unfamiliar with the host of diseases that can be spread by this mechanism and the complications that can result from wound contamination by the normal oral flora of the animals involved. Personnel should be alerted to the need to ascertain their current teta- nus-immunization status, seek prompt medical review of wounds, and initiate veterinary evaluation of the animal involved if it is warranted. Rabies, B-virus infection, hantavirus infection, cat-scratch fever, tularemia, rat-bite fever, brucel- losis, and orf are among the specific diseases that can be transmitted by animal bites with profound consequences (covered in more detail in Chapter 5). The early initiation of antimicrobial therapy for all animal bites that are not trivial appears warranted because there is a high probability of wound contamina- tion with a potential pathogen. That approach will limit the progression of a localized infection and avert the more serious complications of wound infection, which could include cellulitis, abscess, septic arthritis, tenosynovitis, osteomyeli- tis, sepsis, endocarditis, and meningitis. If infections do not respond to therapy, additional microbiological studies that encompass unusual and fastidious organ- isms should be pursued. Fungal agents should not be overlooked as possible wound contaminants; the transmission of blastomycosis to humans by dog bite has been reported (Gnann and others 1983). A wide variety of poisonous and venomous reptiles (Russell 1983), marine animals (Halstead 1978), and arthropods (Biery 1977) might be maintained in the laboratory or animal facility for research or instructional purposes. Institutions that host these uncommon research animals have a special obligation to perform a comprehensive review of safety precautions to ensure the security of animal housing and the appropriate training of personnel who are involved in their care and use. Institutions also should have a plan for the immediate delivery of defini- tive medical care in response to envenomation, including the use of antivenin if available. Many types of envenomation cause massive tissue destruction that predisposes a wound to secondary bacterial infection and indicates a need for treatment with tetanus toxoid and antimicrobial therapy (Goldstein 1990a; Sanford 1985). Sharps Sharps are ubiquitous in animal care. Needles, broken glass, syringes, pi- pettes, scalpelsâall are commonly used in animal facilities and laboratories. Controls include installing puncture-resistant and leakproof containers for sharps at critical locations in the facilities. Workers should be trained to handle and dispose of sharps safely. Improper disposal of sharps with regular trash can
PHYSICAL, CHEMICAL, AND PROTOCOL-RELATED HAZARDS 35 expose custodial staff to puncture wounds and cuts and potentially to exposure to infectious agents and hazardous chemicals. Many states and some municipalities have regulations that specify how to dispose of sharps; these regulations should be checked to ensure that disposal practices are in compliance. Special care is required in the use of needles and syringes to avoid needlestick injuries. This hazard presents a substantial risk for occupationally acquired infec- tion in inoculating or drawing blood from laboratory animals (Miller and others 1987). Appropriate restraint or sedation of animals during procedures entailing the use of sharps decreases the risk of sharps injury to workers. Flammable Materials The National Fire Protection Association (NFPA) has classified fires into four types according to the character of the flammable or combustible materials. Class A, B, and C fires involve general combustible materials (such as wood, paper, and cloth), flammable gases and liquids (such as oil and paint), and electric equipment, respectively. Class D fires involve such combustible metals as mag- nesium, sodium, and potassium. Class A, B, and C materials are found in all animal care facilities. Common combustible materials in Class A fires found in animal care facilities include animal bedding, paper gowns, plastic animal cages, paper towels, and laboratory wipes. Class B flammable solvents might be used in painting animal care rooms, cleaning floors and surfaces, sterilizing equipment, administering anesthesia, and performing laboratory analyses of tissues. Com- mon Class C materials include lighting, wet vacuums, steam-cleaning units, auto- matic cage-washers, and many types of laboratory equipment. Explosive materi- als are not commonly used, however, crystallized picric acid and previously opened and expired cans of ether are common potential explosion hazards. Class D materials are not common in animal care facilities but might exist in some laboratories. Class B liquids are classified according to their flash point, the lowest tem- perature at which a liquid will produce vapor sufficient to propagate a flame. Flammable liquids have flash points less than 100Â°F. Combustible liquids have flash points greater than 100Â°F but less than 200Â°F. The flash points of combus- tible liquids are higher, so they are more difficult than are flammable liquids to ignite at room temperature. Knowledge of flash points of materials can be helpful in selecting a less-flammable material for a particular use so as to lower the related fire hazard. Material Safety Data Sheets for chemicals include informa- tion on flash points. (See page 42, Chemical Hazards.) OSHA provides very strict regulations for the storage and use of flammable and combustible liquids (29 CFR 1910.106).
36 OCCUPATIONAL HEALTH AND SAFETY OF RESEARCH-ANIMAL WORKERS Pressure Vessels Compressed-gas cylinders, air receivers, high-pressure washing equipment, hydraulic lift lines, and steam generators house high-pressure air lines (over 30 psi), and autoclaves contain steam and contents under high pressure. These ves- sels present a substantial hazard to workers if uncontrolled or improper release of the pressure occurs. Compressed-gas cylinders should be secured at all times. Lighting One characteristic of animal care facilities that is not seen in many other operations is a fixed light-dark cycle. In animal care rooms, light cycles can vary, and most animals receive only artificial light. Animals can be kept on light-dark cycles that do not match the natural daily cycles. Or animals might be kept in rooms with single-color lights (usually red) or very low light. For humans, poor lighting can cause visual fatigue or create safety hazards that cause trips, slips, or falls. They might bump into corners of cages or other objects because they cannot see them easily in low light. Humans need an adjustment period for their eyes to become accustomed to the color or light levels in the room. Waiting for this adjustment will make work in the room easier and safer. Electricity Electric hazards can be present whenever electric current is flowing. Electric hazards are ubiquitous in animal care. Most of the hazards are obvious, such as the absence of a plate on a wall socket, an open electric panel, or an ungrounded plug. Less obvious hazards are present on cage-changing tables, biological safety cabinets, and wet vacuum systems. The electric hazards associated with those and other kinds of equipment can be minimized or eliminated through such engineer- ing controls as ground-fault interrupters, such operational procedures as the use of lockout and tagout procedures to control energy sources during repair and maintenance of equipment (CFR 1919.147), and vigilance. Equipment that has frayed or exposed wires or that is designed to be connected to an ungrounded receptacle (as with a two-pronged plug) should not be used. Ultraviolet Radiation Exposure to ultraviolet (UV) radiation can occur in some operations in- volved in the care and use of laboratory animals. For example, UV germicidal lamps are used to sterilize clean surfaces in some work areas, and UV radiation is used in sterilizing water and in the diagnosis of fungal diseases. The most impor- tant exposures to UV radiation might be those of workers who perform outside work. UV radiation is divided into three classes designated UV-A, UV-B, and
PHYSICAL, CHEMICAL, AND PROTOCOL-RELATED HAZARDS 37 TABLE 3-1 Classification and Description of Ultraviolet Radiation UV Classification Wavelengths (nm) Effects Sources UVâA 320â400 Pigmentation of skin Sunlight, black light (black-light region) UVâB 280â320 Photokeratitis, Sunlight, artificial (erythemal region) cataracts, erythema sources UVâC 100-280 Germicidal effects Germicidal lamps (germicidal region) Sources: Adapted from National Safety Council 1988, pp. 227â232, and from the American Confer- ence of Governmental Industrial Hygienists (ACGIH), 1994, p. 100. UV-C, whose wavelengths, effects, and sources are shown in Table 3-1. UV radiation reacts with the vapors of chlorinated solventsâsuch as trichloroethyl- ene, trichloroethane, and chlorofluorocarbonsâto produce phosgene, a potent lung irritant. Those solvents should not be used in areas where UV-B or UV-C radiation is present. If employees must work in the presence of UV radiation, their eyes and skin should be protected against UV exposure. Interlocking devices can be used to turn off UV sources before exposed areas are entered. Window glass is very effective at filtering out wavelengths less than 320 nm except for very intense sources. Lasers Laser is an acronym for light amplification by the stimulated emission of radiation. Laser emissions are produced by solid-state, gaseous, and semiconduc- tor lasers. Most states require lasers to be registered. The American National Standards Institute (ANSI Zâ136.1 1986) has classified lasers on the basis of their power level and hazard potential as follows: â¢ Class I. Lasers that under normal operating conditions do not emit a hazardous level of radiation. â¢ Class II. Low-power lasers that do not have enough power to injure someone accidentally but do have enough power to cause injury if the beam is viewed for extended periods. â¢ Class III. Class IIIa, higher-power lasers that can cause injury if the beam is concentrated with a viewing device, such as binoculars; Class IIIb, lasers that can produce injury if viewed directly. The beam reflected off a mirror-like sur- face is also hazardous.
38 OCCUPATIONAL HEALTH AND SAFETY OF RESEARCH-ANIMAL WORKERS â¢ Class IV. Lasers that, in addition to the conditions in Class III, can present a fire hazard. The major hazard associated with lasers is related to the beam. The beam can cause burns, eye damage, lacerations, or fires, depending on its power. In animal care operations, lasers might be used to perform surgery or to provide medical treatment. Personnel who work with or around lasers should be trained in the hazards and the means to protect themselves. In the case of higher-power lasers, enclosing or shielding the beam (if possible) and providing interlocks on doors where a laser will be used are effective ways to reduce exposure to the beam. Laser surgery can also produce substantial aerosols, fumes, and toxic gases. These hazards should be controlled to prevent harmful exposures of employees. All lasers use electric power, some in large quantities, so the risk of electric shock should be considered and reduced. The National Safety Council (NSC 1988) has produced a list of possible steps for reducing the risk of electric shock associated with lasers. Ionizing Radiation Ionizing radiation is ubiquitous in our daily lives. We are exposed to cosmic radiation, radon gas, natural background radiation, medical x rays, and even internal radiation from potassium-40. To be classified as ionizing, radiation must have enough energy to remove electrons from atoms and so create ions. The ionization can cause chemical changes that can be harmful to a living organism. Ionizing radiation can be classified as particulate and nonparticulate. Particulate radiation is composed of particles that are of atomic origin. Alpha particles are charged particles that each contain two neutrons and two protons. Beta particles are electrons that are emitted with very high energy from many radioisotopes. Positively charged counterparts of beta particles are called positrons. Alpha par- ticles do not travel more than 0.5 in (1.3 cm) in air and cannot penetrate the dead layer of skin. The distance that beta particles can travel depends on their source: in air, some of the more energetic beta particles, such as those from phosphorus- 32, can travel up to 30 ft (9 m), but beta particles from tritium (hydrogen-3) travel only 0.02 ft (0.6 cm). Beta particles are usually stopped by the skin but can cause serious damage to skin and eyes. Nonparticulate radiation includes x rays and gamma rays. X rays and gamma rays are electromagnetic radiation with very short wavelengths. They are photons of energy and can penetrate matter. Photons are relatively difficult to shield. Gamma rays arise from nuclear decay; x rays arise from electron dislocation. When a radionuclide decays, it might produce alpha particles, gamma rays, beta particles, neutrons, or combinations of these. Irradiators and diagnostic x-ray machines are commonly used in research settings. Appropriate training of per-
PHYSICAL, CHEMICAL, AND PROTOCOL-RELATED HAZARDS 39 sonnel and personal protection should be provided. Preventive maintenance of equipment is also critical to safe operations. Radiation can present a hazard through inhalation, ingestion, skin contact, or proximity. The biological effect of ionizing radiation depends on the type of radiation, its energy, and the type of tissue that absorbs it. Two types of hazard must be considered: external and internal. A radionuclide that presents a radiation hazard when it is outside the body constitutes an external hazard; a radionuclide that presents a radiation hazard when it is ingested, inhaled, or absorbed consti- tutes an internal hazard. Alpha and beta particles do not travel very far in air, so they present mainly internal hazards; they can produce harm by being near tissue. Some of the more-energetic beta particles can present an external hazard. Experimentation involving animals and radioisotopes is common in molecu- lar biology today. Use of radioisotopes in or with animals presents several new hazards that must be dealt with. For example, some isotopes can be concentrated in a specific organ, such as iodine in the thyroid. Tissue that has concentrated a radioactive material might have to be handled or disposed of differently, depend- ing on the isotope and the concentration. Bedding material from experimental animals exposed to radioactive materials should be surveyed to determine its radioactivity and then disposed of according to applicable regulations. If an iso- tope could be released by exhalation, additional engineering controls might be required. The use of radioisotopes is strictly controlled by the US Nuclear Regu- latory Commission (US Congress 1971). Investigators should be authorized to use radioisotopes by their institutions; authorizations are based in part on evi- dence of training and established work practices. Housekeeping Good housekeeping keeps work surfaces clean and clear of obstructions, waste, and other material. If boxes, hoses, or bags of bedding material are not removed from the work area, trip hazards can be created or safe work might be impossible because working conditions are cramped. The act of cleaning itself sometimes creates hazards. For example, during steam cleaning of walls and floors of an animal room, the hoses can cause tripping hazards, high-temperature steam can cause burns, and wet floors can cause slipping hazards. Material left in hallways that are used for emergency egress poses a very serious hazard. Imme- diate removal of blockages of exits is imperative. Poor housekeeping practices can increase the seriousness of other hazards associated with animal care. For example, sweeping bedding, hair, and dander from floors, rather than using a vacuum cleaner with a filtered exhaust, can result in high concentrations of airborne allergens that can be distributed throughout the animal facility.
40 OCCUPATIONAL HEALTH AND SAFETY OF RESEARCH-ANIMAL WORKERS Ergonomic Hazards Physical trauma can occur when workers perform tasks that require repeti- tive motions and lifting of heavy loads. Injuries that result from repetitive small stresses are often termed cumulative injuries. Cumulative injuries are not associ- ated with a specific exposure incident. Common cumulative injuries include back injuries, carpal-tunnel syndrome, tennis elbow, and bursitis. Activities in animal care operations that contribute to back injuries include lifting heavy bags of feed, lifting heavy animals, lifting small weights incorrectly, moving or lifting cages, or clipping animalsâ fur manually. Adjusting control knobs, using a screwdriver, using pliers, opening and closing cage doors, moving small animals from cage to cage, operating video display terminals for extended periods, and mopping floors can also lead to repetitive-stress injuries. To reduce hazards due to repetitive motion, vary tasks to lessen the number of repetitions, re-engineer tasks, or redesign equipment or tools to require fewer repetitions with less strain. Lifting heavy loads that exceed permissible-load recommendations of the National Institute for Occupational Safety and Health (NIOSH 1991) is unsafe and presents a substantial risk of acute injury. Anyone lifting heavy loads should be physically fit, should avoid sudden movements, and should use a two-handed lifting technique. Animal care operations that involve a potential for substantial physical stress include moving and restraining large animals, lifting and moving cages, lifting large feed bags, and moving high-pressure wet-vacuum systems. Engineering controlsâsuch as the use of lifting equipment, automation of the lifting operation, or splitting of the loadâcan reduce the risk. Once a hazard is recognized, employee education and engineering controls can be applied to reduce the potential for these types of injuries. Training should be updated if new tools are used in an operation and updated periodically to remind employees of proper work techniques. Employee involvement should be part of each solution. Machinery Conveyor belts, sanders, floor polishers, cage washers, room washing equip- ment, and other machinery have potential to cause injury. The common types of hazards presented by machinery are in-running nip points, crush points, and pinch points. In-running nip points are places on a roller or similar moving surface where a body part of an exposed worker could be pulled into the machin- ery. Crush points and pinch points are areas of a machine where two surfaces could come together to crush or pinch part of the body. These all occur in machin- ery that has exposed moving parts. Each machine should be evaluated to deter- mine whether a workerâs hand or arm could be placed in an area where it could be injured. If a hazardous area is identified, guarding should be installed to eliminate the hazard. Guarding is important even when workers know that they are not to
PHYSICAL, CHEMICAL, AND PROTOCOL-RELATED HAZARDS 41 place their hands in a dangerous area. Slips, falls, and loss of awareness of the hazard can cause injury if guarding is not in place. In large equipment that requires operators or repair mechanics to work in the operating chamber, such as cage washers, an internal release mechanism should be available to allow emer- gency escape if the equipment is inadvertently started. Noise Exposure to intense noise can result in loss of hearing. Chronic noise-in- duced hearing loss is a permanent condition and cannot be treated medically. This type of hearing loss is usually characterized by declining sensitivity to frequen- cies above 2,000 Hz. Exposure to an intense noise for a short period can cause temporary or permanent loss of hearing. OSHA limits employee exposure to noise to 90 decibels measured on the A scale of a standard sound-level meter at slow response (dBA) averaged over an 8-h workshift (29 CFR 1910.95). The time-weighted average must be lower than 90 dBA if the workshift is longer than 8 h (29 CFR 1910.95). Where levels exceed 85dBA, the exposed employees need to participate in a hearing-conservation program that includes monitoring, audio- metric testing, hearing protection, training, and record-keeping (29 CFR 1910.95 c though o). Hearing loss is not the only adverse effect of exposure to noise. Noise can make speech difficult, cause loss of concentration, distract workers, and increase fatigue (NSC 1988). In an animal care facility, noise can result from animals, particularly pigs and dogs, and from equipment, such as cage washers, high pressure air cleaning equipment, and wet vacuum systems operated in a confined space. A useful way of assessing whether a noise exposure might be excessive is to visit the area and attempt to converse with another person or attempt to talk on the telephone. The noise is probably excessive if normal speech or talking on the telephone is diffi- cult or impossible. When this condition is observed, the noise levels should be assessed by a person knowledgeable about noise, noise-measurement techniques, and data interpretation. Most often, such a person will be an industrial hygienist or an acoustical engineer. OSHA requires that engineering controls be applied first to control the hazard. Engineering controls include shielding, quieter equip- ment, and installation of sound-deadening materials on the walls and ceilings. If acceptable noise levels are not achieved that way, administrative controls or personal protective equipment will be necessary. Administrative controls include limiting the time that an employee works in the noise-hazard area. It is prudent to provide workers who are exposed to a noise hazard earplugs, earmuffs, or other protective equipment during the noise-evaluation period. Ultrasonography is used in laboratories and animal care facilities for imag- ing internal structures. If the frequency is below 20 kHz, it is covered by the OSHA noise standard. Even if it is above 20 kHz, noise exposure is possible because of subharmonics at these higher frequencies (Strickoff and Walters 1990).
42 OCCUPATIONAL HEALTH AND SAFETY OF RESEARCH-ANIMAL WORKERS Chemical Hazards Most employees engaged in the care and use of research animals are familiar with the hazards of chemicals used in animal care and laboratory environments. Employee knowledge of chemical hazards and of relevant protective measures has been focused and increased in recent years through employersâ responses to two important health and safety standards promulgated by OSHA: the Hazard Communication Standard (29 CFR 1910.1200) and the Occupational Exposure to Hazardous Chemicals in Laboratories (29 CFR 1910.1450), which is known as the laboratory standard. The recognition and control of chemical hazards in re- search institutions have also been aided by Prudent Practices for Handling Haz- ardous Chemicals in Laboratories (NRC 1981). That volume was extensively revised and updated in 1995, and the new edition, Prudent Practices in the Laboratory: Handling and Disposal of Chemicals (NRC 1995), provides practi- cal guidance for evaluating chemical hazards and for working safely with chemi- cals in the research setting. It extensively discusses sources of hazard information and principles for evaluating and elucidating toxic effects of chemicals. It consti- tutes a relevant and comprehensive reference document on the recognition and control of chemical hazards, and it should be consulted by all who have responsi- bility for the planning, conduct, and support of safe research. Flammability, corrosiveness, reactivity, and explosivity are hazardous prop- erties of chemicals that are usually well understood. Toxicity is the least-predict- able hazardous property of chemicals. Exposure to toxic chemicals can cause acute or chronic health effects. General classes of toxic chemicals that might be handled in a research environment are carcinogens, allergens, asphyxiants, corro- sives, hepatotoxicants, irritants, mutagens, nephrotoxicants, neurotoxicants, and teratogens. Health risks associated with toxicants depend on both the inherent toxicity of the chemicals and the nature and extent of exposure to them. Animal care activities can seriously influence the potential for employee exposure. Thus, animal care practices that might contribute to employee exposures need to be carefully assessed so that toxic hazards of chemicals associated with the care and use of research animals can be recognized and controlled. A comprehensive review of chemical-hazard assessment and control is provided in Prudent Prac- tices in the Laboratory: Handling and Disposal of Chemicals (NRC 1995). Typical sources of chemical exposure in the care and use of research animals involve the use of disinfectants, pesticides, anesthetic gases, and chemicals for preserving tissues. Sources can include animals that have been intentionally exposed to highly toxic chemicals. Another important source is the disposal of bedding and other waste materials from experimental procedures. Disinfectants and detergents include soaps, cleaning chemicals, acid-con- taining chemicals, alcohols (most commonly ethanol and isopropanol), aldehydes (including formaldehyde and gluteraldehyde), and halogenated materials (such as chlorinated and iodinated bleaches). Some phenolic compounds (including potas-
PHYSICAL, CHEMICAL, AND PROTOCOL-RELATED HAZARDS 43 sium o-phenylphenate and potassium o-benzyl-p-chlorophenate) and quaternary ammonium compounds are also used as disinfectants. Various pesticides can be used within animal facilities, but most animal facilities restrict the use of pesti- cides because of their potential effects on the animals. The primary chemical used as a preservative is formalin as a 10% neutral-buffered solution, but other mate- rials are used from time to time. Several occupational diseasesâincluding cancer, spontaneous abortion, and liver diseaseâhave been associated with exposure to waste anesthetic gases. Monitoring exposures to waste anesthetic gases in animal operating rooms is an important part of the health and safety program because of the difficulty in matching anesthetic-delivery equipment to the animals. Burns and irritation of the skin are the most common chemical injuries associated with animal care and use. Some chemicals, such as formaldehyde and gluteraldehyde used for preserving tissue, can cause an allergic response in sen- sitized people. The risk of injury and illness associated with chemical use can be minimized by practices that reduce or prevent exposure. HAZARDS ASSOCIATED WITH EXPERIMENTAL PROTOCOLS A fundamental principle in the conduct of research is the need to determine the potential hazards associated with an experiment before beginning it. That is extremely important in planning experiments that involve research animals, be- cause investigators might be unfamiliar with the intrinsic hazards presented by the animal species of choice or tissues derived from them, and managers and their employees who care for the research animals should be informed of the hazards presented by the experimental protocol. Consideration of both animal-related hazards and protocol-related hazards would benefit from a collaborative assess- ment in which the investigator, the institutional veterinarian, the animal care supervisor, and a health and safety professional participate. A collaborative as- sessment is strongly encouraged if the animal experimentation involves either the testing of chemicals for their toxic properties or research with experimentally or naturally infected animals. Whether or not a collaborative initiative is pursued, investigators have an obligation to identify hazards associated with their research and to select the safeguards that are necessary to protect employees involved in the care and use of their research animals. Hazards associated with experimental protocols are influenced by two prin- cipal factors: the dangerous qualities of the experimental agents and the complex- ity or type of the experimental operations. For example, toxicity, reactivity, flam- mability, and explosivity should be considered when an experimental protocol involving chemical agents is being planned, and virulence, pathogenicity, and communicability are possible hazardous qualities of biological agents. The complexity and type of an experimental operation have a direct impact on the extent of potential exposure that an employee receives while carrying out
44 OCCUPATIONAL HEALTH AND SAFETY OF RESEARCH-ANIMAL WORKERS or participating in an experimental protocol. For example, during incorporation of a test chemical into feed for ingestion studies, a contaminated dust created during milling and mixing and during transfer of the diet could result in respira- tory and dermal exposures. Test material applied to the skin of experimental animals might be disseminated by handling of animals, clipping of hair, changing of bedding, and sweeping of the animal room floor. Vapors are potential sources of exposure during the application of test material to the skin. Exposing an animal to an agent by injection will create a risk of accidental self-inoculation. Inhala- tion challenges are particularly hazardous and should be conducted only by in- vestigators who have appropriate experience and containment equipment. Protocols Involving Chemicals of Unknown Hazard A comprehensive, rigidly followed plan is necessary for testing chemicals of unknown hazard for their toxic properties. It should be presumed that a chemical is hazardous to humans, and the plan should describe specific procedures for handling the chemical from receipt through disposal of animal waste and process- ing of tissues for histopathological or biochemical examination. Prudent Prac- tices in the Laboratory: Handling and Disposal of Chemicals (NRC 1995) pro- vides an excellent general model for planning experiments that involve hazardous chemicals. It was specifically structured to follow the sequence of stages that should be considered in planning a safe experiment: evaluating hazards and as- sessing risks in the laboratory, management of chemicals, working with chemi- cals, working with equipment, disposal of chemicals, laboratory facilities, and government regulation of laboratories. It is important not to underestimate the risk presented by experimental chemicals. But most references on chemical safety provide little guidance that is directly applicable to the care and use of research animals. Therefore, developing plans for a specific research protocol that in- volves research animals and chemicals of unknown hazard will require ingenuity, a quality best derived from a collaborative planning process. Protocols Involving Infectious Agents Experiments involving experimentally or naturally infected research animals present recognized risks of occupationally acquired infections. In the largest survey of laboratory-acquired infections conducted to date, research animals or their ectoparasites were associated with about 17% of the reported infections (Pike 1976). In the few cases (under 3%) in which infections were attributed to a recognized accident, the primary source was a bite or scratch from an infected animal. That survey and others (Sullivan and others 1978) have shown that trained scientific personnel and technicians were most likely to be infected, although animal care providers and janitorial and maintenance workers have been proved to be at risk for occupationally acquired infection. Most of the zoonotic infections
PHYSICAL, CHEMICAL, AND PROTOCOL-RELATED HAZARDS 45 cited in these surveys were associated with research activities involving experi- mentally infected animals. Transmission of zoonotic disease in an animal facility that is not involved with infectious disease research is rare. CDC and NIH have identified 17 infectious agents or genera other than arboviruses as proven hazards for personnel who use and care for experimentally or naturally infected research animals (CDC-NIH 1993). The agents and genera are summarized in Table 3-2. Arbovirusesâmost notably Venezuelan equine encephalomyelitis virus, yellow fever virus, Rift Valley virus, and Chikungunya virusâhave also been respon- sible for laboratory animal-associated infections (Hanson and others 1950). The Subcommittee on Arbovirus Laboratory Safety (SALS) of the American Com- mittee on Arthropod-Borne Viruses reported 818 occupationally acquired infec- tions caused by 62 different arboviruses or related viruses (SALS 1980). A total of 19 of these infections, which were associated with 10 virusesâSemliki Forest, Venezuelan equine encephalitis, Western equine encephalitis, yellow fever, Hypr, Rift Valley fever, Congo-Crimean hemorrhagic fever, Junin, Lassa, and Machupoâresulted in death. Investigators who are planning research activities involving experimentally or naturally infected vertebrate animals should carefully review Biosafety in Mi- crobiological and Biomedical Laboratories (CDC-NIH 1993). It defines four levels of control that are appropriate for animal research with infectious agents that present occupational risks ranging from no risk of disease for healthy people to high individual risk of life-threatening disease, and it recommends guidelines for specific agents. The four levels of control, referred to as animal biosafety levels 1-4, each have appropriate microbiological practices, safety equipment, and features of animal facilities. The selection of an animal biosafety level is influenced by several characteristics of the infectious agent, the most important of which are the severity of the disease, the documented mode of transmission of the infectious agent, the availability of protective immunization or effective therapy, and the relative risk of exposure created by manipulation in handling the agent and caring for infected animals. Animal biosafety level 1 is the basic level of protection appropriate for well- characterized agents that are not known to cause disease in healthy humans. Animal biosafety level 2 is appropriate for handling a broad spectrum of moder- ate-risk agents that cause human disease by ingestion or through percutaneous or mucous-membrane exposure. Extreme precautions with needles or sharp instru- ments are emphasized at this level. Animal biosafety level 3 is appropriate for agents that present risks of respiratory transmission and that can cause serious and potentially lethal infections. Emphasis is placed on the control of aerosols by containing all manipulations and housing infected animals in isolators or venti- lated cages. At this level, the animal facility is designed to control access to areas where animals are kept and includes a specialized ventilation system that is designed to maintain directional airflow. Exotic agents that pose a high indi- vidual risk of life-threatening disease by the aerosol route and for which no
46 OCCUPATIONAL HEALTH AND SAFETY OF RESEARCH-ANIMAL WORKERS TABLE 3-2 Reported Occupationally Acquired Infections Associated with Experimentally or Naturally Infected Research Animals Pathogenic Agent Animals Comment References Viral Agents B virus Macaques Contact with Holmes and others (Circopithecine experimentally and 1990, Palmer 1987 herpesvirus 1) (formerly naturally infected Herpesvirus simiae) animals Hepatitis A virus Nonhuman Contact with Pike 1979 primates experimentally and naturally infected animals Lymphocytic Mice, hamsters, Contact with Bowen and others choriomeningitis virus guinea pigs experimentally and 1975, Jahrling and naturally infected Peters 1992, Pike animals 1976 Marburg virus African Green Contact with Martini & Siegert monkeys naturally infected 1971 animals Martini 1973 Simian Macaques Handling of blood CDC 1992a, immunodeficiency virus from experimentally Khabbaz and others infected animals 1992 Vesicular stomatitis virus Livestock Contact with naturally Hanson and others infected animals 1950, Patterson and others 1958 Rickettsial Agents Coxiella burnetii Sheep Contact with naturally CDC 1979, Spinelli infected animals and others 1981 Bacterial Agents Brucella (B. abortus, Cattle, dogs, Contact with Pike 1976 B. canis, B. melitensis, goats, swine experimentally and B. suis) naturally infected animals, presumed aerosol exposure Campylobacter jejuni Dogs, primates, Fox and others 1989 coyotes, etc. Chlamydia psittaci Birds Contact with Miller and others experimentally and 1987, Pike 1976 naturally infected animals, presumed aerosol exposure
PHYSICAL, CHEMICAL, AND PROTOCOL-RELATED HAZARDS 47 TABLE 3-2 Continued Pathogenic Agent Animals Comment References Francisella tularensis Rabbits Contact with Pike 1976 experimentally and naturally infected animals or their ectoparasites Leptospira interrogans Rabbits, dogs, Contact with Richardson 1973 rats, mice, experimentally and guinea pigs naturally infected animals Legionella pneumophila Guinea pigs Aerosol or droplet CDC 1976 exposure during animal challenge Mycobacterium Nonhuman Contact with Kaufmann and tuberculosis primates experimentally and Anderson 1978 naturally infected animals Salmonella spp. Mice, rats, Contact with Grist and Emslie dogs, cats experimentally and 1987, Miller and naturally infected others 1987, Pike animals 1976 Shigella spp. Guinea pigs, rats, Contact with Pike 1976 mice, nonhuman experimentally primates infected animals Streptobacillus Rats Contact with Pike 1976 moniliformis experimentally and naturally infected animals Fungal Agents Sporothrix schenckii Rats Bite from an Jeanselme and experimentally Chevallier 1910, infected animal 1911 Microsporum, Mice, rabbits, Contact with Hanel and Kruse Trichophyton guinea pigs experimentally and 1967, McAleer naturally infected 1980; Pike 1976 animals Source: CDC-NIH 1993.
48 OCCUPATIONAL HEALTH AND SAFETY OF RESEARCH-ANIMAL WORKERS treatment is available are restricted to animal biosafety level 4 high-containment facilities. Worker protection in these facilities is provided by the use of physi- cally sealed glove boxes or fully enclosed barrier suits that supply breathing air. Most research involving experimentally and naturally infected vertebrate animals will be conducted at animal biosafety level 2 or 3. A summary of hazard control elements for these two animal biosafety levels is presented in Table 3-3. Animal biosafety level 1 is not addressed here because it represents normal housing without special precautions. Animal biosafety level 4 is not discussed because containment facilities for this work are limited to a few highly specialized institu- tions that have considerable experience in the handling of dangerous and exotic pathogens. Research protocols involving emerging and re-emerging pathogens require careful planning and might require review of previous studies. Most of the litera- ture on safety in handling infectious agents was published 3-4 decades ago, but it is still invaluable in planning safe experiments. Modern research can also present novel hazards that require careful review. For example, the potential occupa- tional health and safety risks need to be considered before animal experiments are undertaken to evaluate the safety to humans of viral vectors that are being pro- posed for use in gene therapies. Similarly, studies with transgenic animals that express receptors for human pathogens or whose genomes contain proviral DNA for an infectious virus should be evaluated to determine whether safeguards appropriate for handling the wild-type infectious agent should be applied. Assis- tance in the determination of risk and the selection of appropriate safeguards can be found in the NIH Guidelines for Research Involving Recombinant DNA Mol- ecules (NIH 1994). A recent revision of its Appendix B has a section (B-V) on frequently used viral agents, including viral vectors. These protocols might require approval of the institution or funding agency. The institutionâs biosafety committee and biosafety officer are valuable resources and should be consulted when experiments are being planned. Several authoritative reference works provide excellent guidance for the safe handling of infectious microorganisms in research. Three that are particularly noteworthy are Biosafety in the Laboratory: Prudent Practices for the Handling and Disposal of Infectious Materials (NRC 1989), Laboratory Safety: Principles and Practices (Fleming and others 1995), and Biosafety in Microbiological and Biomedical Laboratories (CDC-NIH 1993). Most-helpful practices to prevent occupationally acquired infections associ- ated with the care and use of research animals are the following: â¢ Avoid the use of sharps whenever possible. Take extreme care when using a needle and syringe for inoculating research animals or when using sharps during necropsy procedures. â¢ Keep hands away from mouth, nose, and eyes.
TABLE 3-3 Summary of Recommended Animal Biosafety Levels 2 and 3 for Research Programs that Involve Experimentally or Naturally Infected Vertebrate Animals Animal Biosafety Agents Practices Safety Equipment Facilities Level 2 Cause human disease of â¢ Good personal hygiene â¢ Primary barriers: â¢ No recirculation of varied severity; indigenous â¢ Limited access containment equipment exhaust air â¢ Biohazard warning signs used for necropsy and â¢ Autoclave available Hazard: percutaneous exposure, â¢ Sharps precautions procedures with high â¢ Hand washing sink in mucous membrane exposure, â¢ Biosafety manual potential for creating animal rooms ingestion (enteric pathogens) â¢ Personal protective aerosols â¢ Decontamination of cages equipment: laboratory Examples: HBV, HIV, Shigella before washing coats, gloves, face and flexneri, Salmonella typhimurium, â¢ Decontamination of respiratory protection as Toxoplasma gondii infectious waste required 3 Cause human disease with â¢ Good personal hygiene â¢ Primary barriers: â¢ Physical separation from serious or lethal consequences; â¢ Controlled access containment equipment access corridors indigenous or exotic â¢ Biohazard warning signs used for all activities â¢ Self-closing double-door PHYSICAL, CHEMICAL, AND PROTOCOL-RELATED HAZARDS â¢ Sharps precautions involving infectious passage way Hazard: aerosol transmission â¢ Biosafety manual materials or infected â¢ No recirculation of â¢ Decontamination of clothing animals exhaust air Examples: Mycobacterium before laundering â¢ Personal protective â¢ Directional airflow tuberculosis, Brucella canis, â¢ Decontamination of cages equipment: laboratory â¢ Hand washing sink in Coxiella Burnetii before bedding is removed gowns, gloves, face and animal rooms â¢ Decontamination of all wastes respiratory protection as â¢ Autoclave available required, protective in facility footwear as required Source: CDC-NIH 1993. 49
50 OCCUPATIONAL HEALTH AND SAFETY OF RESEARCH-ANIMAL WORKERS â¢ Wear protective gloves and a laboratory coat or gown in areas where research animals are kept. â¢ Remove gloves and wash hands after handling animals or tissues derived from them and before leaving areas where animals are kept. â¢ Use mechanical pipetting devices. â¢ Never eat, drink, smoke, handle contact lenses, apply cosmetics, or take or apply medicine in areas where research animals are kept. â¢ Perform procedures carefully to reduce the possibility of creating splashes or aerosols. â¢ Contain operations that generate hazardous aerosols in biological safety cabinets or other ventilated enclosures. â¢ Wear eye protection. â¢ Keep doors closed to rooms where research animals are kept. â¢ Promptly decontaminate work surfaces after spills of viable materials and when procedures are completed. â¢ Decontaminate infectious waste before disposal. â¢ Use secondary leakproof containers to store or transfer cultures, tissues, or specimens of body fluids.