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Spotlight on a diverse industry
Manufacturing facilities typically focus on the creation of a finite array of products in large volumes. Consequently, the potential hazards inherent to these workplaces are limited in scope, although they may be high in output. On the other hand, a research and testing laboratory performs testing and diagnostic evaluation of samples, a setting not typically within the production line sequence; hence, the likelihood of exposures to large volumes of potentially hazardous agents is usually much lower. However, the sophisticated analytical procedures conducted in laboratory settings often involve the use of a variety of exotic and potentially hazardous agents. It is this array of hazards, combined with differences among potentially exposed individuals, that makes the laboratory setting a unique working environment.
TASKS OF THE JOB
Laboratories are ubiquitous in today’s world, are designed to fulfil various roles, and can vary markedly in size, from that of a small closet area to multiple floors in large buildings. Commercially operated laboratories provide analytical testing services for products, such as processed food, or are involved in the research and development of new products. Governments operate laboratories for quality control purposes to ensure product integrity and performance. Governments also operate forensic laboratories for the identification of evidence in crimes or to determine cause of death. Healthcare facilities maintain medical, clinical, and/or veterinary laboratories to accommodate the processing of clinical specimens for medical diagnoses, whereas universities house laboratories directed at research endeavours. Based on data from the United States Bureau of Labor Statistics, in 2003 there were more than 430 000 persons employed in medical, diagnostic, veterinary, and/or testing laboratories—that is, approximately 0.3% of the civilian workforce (http://www.bls.gov/oes/2003/may/oessrci.htm).
Regardless of their purpose or setting, all laboratories share certain characteristic tasks. In a broad sense, the tasks inherent to laboratory work include some or all of the following: development of testing protocols and sampling strategies; instrument calibration and internal quality assurance; product sampling and collection; transport and delivery of samples to the laboratory; receipt and recording of sample entry; sample preparation; sample analysis; calculation and reporting of results; and waste disposal. Of these tasks, those of greatest concern for potentially hazardous exposures involve sample collection, preparation, and analysis.
All laboratories perform analyses using equipment and techniques that subject samples to extreme physical, chemical, radiological, and/or biological conditions, often simultaneously. In turn, these procedures represent potentially hazardous exposures to workers in and around these settings. Effective implementation of controls and protective measures for these workers requires an in-depth appreciation of the complexities of the laboratory work environment.
In addition to the various potential hazards that may be present in the laboratory work setting, it is important to consider the diversity of the potential at-risk population. First are the laboratory workers themselves. These individuals are recruited, hired, trained, and receive direct compensation for their efforts; their adherence to accepted work practices can be a condition of continued employment or annual performance evaluations. However, these kinds of administrative controls may not extend to other individuals who can spend time in a laboratory, including students, volunteers, and visiting scholars. Because of the cyclical nature and variable duration of such exchanges and visits, these persons may not be subjected to the same surveillance measures, workplace monitoring, hazard awareness training, safety performance assessment, controls, or expectations afforded to usual laboratory employees.
HAZARDS OF THE JOB AND IN THE WORKPLACE
The potential hazards present in a laboratory environment can be classified, from a pragmatic standpoint, into four main categories: chemical, physical, radiological, and biological. Each agent class exhibits a unique set of concerns, warranting specialised attention.
Given their large number, a detailed discussion of individual chemical agents used in laboratory settings is beyond the scope of this article. However, analysis of laboratory samples typically involves a series of elaborate processes that allow the isolation of a specific characteristic of a compound. In the processing and analysis of these samples, a wide array of exotic hazardous chemicals may be used, which can be broadly classified by the health and safety risks inherent in their use. These risk categories include carcinogens, toxic or highly toxic agents, reproductive toxins, irritants, corrosives, sensitisers, hepatotoxins, nephrotoxins, neurotoxins, haematopoietic system toxins, and agents which damage the lungs, skin, eyes, or mucous membranes.1 The most likely routes of exposure are inhalation and absorption through skin or mucous membranes.
In comparison to private industry as a whole, where trends in the incidence of both work related skin disorders and acute toxic inhalations have been declining steadily since 1998, rates in laboratory settings have either fluctuated or increased (table 1).
In addition to the hazards represented by the intrinsic toxicity of a chemical agent, its physical state may also pose a health hazard (for example, combustible liquids, compressed gas, explosive, flammable, pyrophoric compounds, and compounds that are unstable or water reactive).
From an ergonomic standpoint, laboratory analytical techniques can require long periods of standing on hard floors or sitting in one position, together with the performance of repeated tasks, increasing the chances of low back pain and other musculoskeletal discomfort. Work surfaces not matched to the worker’s height and inadequate task lighting in the work area can also cause work discomfort. Repetitive procedures such as opening and closing vial caps, pipetting (fig 1), and sample sorting hold the potential to result in repetitive motion injuries or other cumulative trauma. Similar concerns exist when prolonged periods of data entry or other computer based work are required. In selected laboratory settings, such as animal research work areas, chronic exposure to noise may also be an additional physical hazard of concern.
A review of occupational illness rates in the United States in private industry, for the years 1998 to 2001 (most recently available data), indicates that the incidence of cases due either to physical agents or repetitive trauma in medical and dental laboratories are consistently higher than those for industry as a whole (table 1).
Sources of both ionising and non-ionising radiation are commonly employed in laboratory analytical procedures, most notably in government and university research settings. For example, almost 80% of all biochemical research funded by the US National Institutes of Health includes use of radiation in some form or fashion, and the evaluation of 90% of all new pharmaceutical drugs approved by the US Food and Drug Administration involves radionuclide based testing.2 Ionising radiation sources in the form of radionuclide tracers are used to label chemical compounds to determine their fate in various systems. The amount of activity used in such tracer experiments is typically small, measured in the microcurie to megabecquerel range, so the potential for acute biologically significant whole body doses is quite low. However, since the material used in radiotracer experiments is often in an unsealed form, the possibility exists for internal organ exposure through inhalation or ingestion.
Higher activity sources of encapsulated radioactive materials, with doses in the curie to gigabecquerel range, may be used to irradiate products. For example, blood banks may irradiate whole blood products to decrease chances of a graft-versus-host reaction in immunosuppressed patients. In such operations, the sources are typically housed in a specially designed device that precludes direct accessibility to the radioactive source.
Lasers have become a common source of non-ionising radiation used in laboratories. Laser systems are classified according to the possible threat they represent to key organ systems such as the eye and skin, ranging from class I, which does not present harm during use, to class IV, which can produce significant eye and/or skin damage.3 Other sources of non-ionising radiation in laboratories include radio frequency, microwave, and infrared radiation. Although acute health effects such as burns or localised heating from exposure to non-ionising radiation are well recognised, the possibility of chronic effects is still being evaluated.4
Potentially infectious agents may be encountered in laboratories, such as microbiology laboratories, when analysing samples derived from humans, plants, or animals, and risks associated with handling such specimens are dependent on the specific microorganism and the pathway of exposure. A hallmark series of elegant surveys conducted many years ago by Sulkin and Pike on laboratory acquired infections showed that laboratory acquired infections paralleled the prevalent infectious diseases at the time, and were most likely transmitted via procedures that resulted in the creation of aerosols.5,6 On the other hand, infectious agents such as human immunodeficiency virus, hepatitis B, and hepatitis C viruses are primarily transmitted in the laboratory setting via percutaneous transmission or contact with mucous membranes or non-intact skin; in these cases, the most common vehicles of transmission are needles and cutting sharps. More recently, occupationally acquired infections caused by “new” microorganisms, such as West Nile virus, have been documented in laboratory workers.7
Compounding the diversity of potential hazards present in the laboratory setting are situations involving simultaneous exposures, which can be commonplace. For example, it is not unusual to encounter a laboratory environment where individuals work in a building (with its concurrent physical hazards), and perform extractions on potentially infectious biological materials using chemical solvents and radioisotope tracers. The appropriate design and implementation of safety measures to control such simultaneous exposure situations warrants a sound understanding of the risks and associated controls for each type of agent on both the part of the worker and the occupational health professionals supporting the operations. Thus, a laboratory procedure involving the manipulation of potentially infectious agents may require the use of an enclosure device such as a biological safety cabinet, but if the process involves an ignition source and potentially flammable chemicals with lower vapour pressures, gases could accumulate in the safety cabinet enclosure and cause an explosion. Likewise, personal protective equipment intended for one hazard may not provide adequate protection against a second agent. A classic example would be the use of latex gloves, which provide protection against the transmission of infectious agents through breaks in the skin, but could allow permeation of certain chemicals.
OCCUPATIONAL HEALTH AND SAFETY MANAGEMENT
The protection of workers in laboratory environments requires a combination of clear management commitment, appropriate facility design, engineering controls, worker training, personal protective equipment, routine surveillance, periodic audits and inspections, and effective communication. Ultimately, though, an effective health and safety programme depends most critically on upper management support and commitment. When upper management clearly articulates its dedication to maintaining a work environment that is safe and healthy, the remaining necessary protective measures become easier to implement.
Facility design and engineering controls
Central to the protection of workers is proper planning and design of the laboratory environment, which has evolved markedly over the past 30 years. The design should be comprehensive, with attention to areas for storage of chemicals (fig 2), general and local exhaust ventilation, adequate workstation design and task lighting (fig 3), implementation of appropriate fume hoods and wash basins, disposal of laboratory waste, and accessible safety eyewash stations and emergency showers. Because laboratories are usually housed within a larger physical structure (either permanently fixed or mobile in nature), structural safety hazard controls such as effective fire detection and suppression, and occupant means of egress are essential.1,8 The presence of sophisticated analytical equipment mandates the availability and proper functioning of electrical power supplies and associated safety features, such as ground fault circuit interrupters. For example, gel electrophoresis units employ high electrical currents to separate chemical compounds, a procedure performed in the presence of electrically conductive liquids, making it essential to incorporate safety systems able to interrupt current flow in the event of a system malfunction.9 In settings where flammable or explosive vapours or gases may be present, specialised designs for the enclosure of switches and lighting sources may also be needed.
Facilities should be designed with means of egress in mind, including clear hallways and proper placement of office areas to avoid traversing the laboratory area in the event of an accidental release. Shutoff valves for gases and fluids should also be clearly marked, and access to emergency stations kept clear and free of clutter.
Since local exhaust ventilation systems are widely used in laboratory settings to remove vapours from the worker’s breathing zone or to prevent the release of aerosols, occupational health professionals should pay particular attention to these devices. Laboratory exhaust hoods draw room air into the hood so that contaminants are prevented from entering the breathing zone of the worker. A variation to this design is when the job task requires protection of the material in the hood as well, such as when manipulating biological agents and tissue cultures. In these cases, a biological safety cabinet must be used, in which room air is first filtered before passing over any items inside the cabinet, thus providing both personnel and product protection (fig 4). Improper placement, malfunction or misuse of either type of enclosure unit can result in contaminant release. For example, hoods and cabinets placed too close to pedestrian traffic can result in airflow disruptions and loss of capture velocity.
Special attention should be given to the training and orientation of all individuals in a laboratory setting, including visitors and students, given the complexity of potential hazards present. Workers should be thoroughly trained on the laboratory facility’s features, including proper operation and how to proceed in the event of an emergency. Safety training should cover the proper use and maintenance of fume hoods and biological safety cabinets, as well as the proper selection and use of personal protective equipment, with particular attention to the compatibility of the equipment with the worker (video clip 1). For example, cases of both irritant and allergic contact dermatitis associated with the use of latex gloves are well described, reflecting an unintended consequence of a regulatory measure originally intended to protect against such events.10,11
In the USA, the Occupational Safety and Health Administration (OSHA) requires that laboratories handling hazardous chemicals have a comprehensive chemical hygiene plan in place. This written programme, developed and implemented by the employer, addresses procedures, equipment, personal protective equipment, work practices, employee training, and exposure control directed at protecting employees from the health hazards presented by hazardous chemicals.12 Because of the variety of chemicals and their potential toxicities, laboratory workers should receive proper training in the identification and safe handling of chemicals and have ready access to information on their hazards. Material safety data sheets and other technical information sheets, often created by chemical product manufacturers, can provide important initial safety information regarding specific risks, and should be readily available in the workplace.
Training of employees in the handling of radioactive sources and biological agents, the latter emphasising the use of universal (standard) precautions, addresses radiological and biological hazards. In the USA, worker training in these areas is mandated under the Nuclear Regulatory Commission and the OSHA Bloodborne Pathogens Standard.13,14
Surveillance and safety committees
Because the laboratory environment is inherently dynamic, change is the norm. Therefore, routine health and safety audits and assessments are necessary to determine if any changes have resulted in the emergence of new potential hazards. For example, the placement of a new analytical device in a local exhaust ventilation fume hood could result in the partial block of airflow, producing eddy currents which actually result in reintroduction of contaminants into the work environment (video clip 2). Ideally, such periodic inspections should be conducted by health and safety personnel, with the active involvement of the laboratory staff, thus stimulating local interest and control over the safety systems in place.
One way of establishing a community culture of safety in the organisations hosting laboratory work environments is through the creation of safety committees that are inclusive of representation of upper management and workers. Through the routine reporting of both the successes and failures of an organisation’s health and safety efforts, the workforce can be appraised of the systems and procedures that work, and those that warrant attention. The lessons learned from these efforts can be applied to the non-employee populations as well. Active worker involvement, combined with upper management commitment, can represent a powerful tool in maintaining a healthy, safe and productive environment.
Although there are many workplaces in both developed and developing nations that are associated with significant occupational hazards, laboratories represent perhaps one of the microenvironments with the greatest diversity of risks, combined with a diverse at-risk population. The protection of workers in these environments requires an in-depth knowledge of the various exposures (which may occur simultaneously), management support of health and safety, appropriate facility design, worker training, protective equipment, a team approach to surveillance and inspections, and effective communication. When applied appropriately, these measures can assist laboratories in fulfilling their essential functions so that workers remain productive without undue occupational risk.
Video clip 1: Different types of protective equipment used in laboratories. This video segment shows some examples of safety equipment and devices in a laboratory setting, including eye wash stations and safety showers, flammable storage cabinets, secured compressed gas cylinders, ground fault circuit interrupters, sealed centrifuge cups, sharps containers, hazard signage, and material safety data sheet binders.
Video clip 2: Air flow through a laboratory fume hood. This video segment illustrates the consequences of improper placement of a piece of laboratory equipment within a local exhaust ventilation fume hood, resulting in the partial block of airflow, producing eddy currents which actually result in reintroduction of contaminants into the work environment.
Spotlight on a diverse industry
Video clip 2: Air flow through a laboratory fume hood
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When developing programs to protect workers, primary emphasis should be placed on engineering controls, such as protective barriers and guards. When these measures are not sufficient to control the risk, the use of personal protective equipment is needed. This video sequence will provide a quick overview of some of the different types of personal protective equipment used in laboratory work settings [Available shortly]
The key considerations for the selection of personal protective equipment include the characteristics of the hazard to be encountered, the part of the body to be protected, and the limitations of the equipment itself [Available shortly]
Safety glasses & goggles
Take, for example, protective eyewear. Safety spectacles can protect the eye from accelerated particles or splashes, but this type of eyewear may not protect against vapors or gases. Modifications are necessary to protect those who wear prescriptive eyewear, and special consideration must be given to those wearing contact lens as well. [Available shortly]
Gloves must also be carefully selected. A particular glove may offer protection against one type of agent, but may not serve as an effective barrier for another. Users should verify compatibility as per the glove manufacturer�s specifications [View Clip]
File size: 74MB
Lab coats, tyvex, etc.
Protective garments in the form of lab coats, aprons or jump suits can also be used to protect workers. Proper fit and resistance to liquids are important considerations. [Available shortly]
Respirators � fit testing
A wide variety of respiratory protection devices are available for use. To be effective, workers need to be educated in their proper use and knowledgeable of their use limitations. Respirators with a tight fitting face seal can be fit tested to assess the integrity of the seal established when worn by a worker. [Available shortly]
Adverse Reactions to PPE and appropriate measures
In some instances, workers can exhibit adverse reactions from wearing protective equipment, so consideration must be given to the compatibility of the worker and the protective equipment as well. When afforded a choice, engineering controls are the desired means of worker protection because they do not rely on human intervention once installed. But when such controls are insufficient, personal protective equipment can be used to help protect workers. When relying on protective equipment be sure to become aware of the characteristics of the hazard, identify the part of the body to be protected, and the know limitations of the equipment [Available shortly]
Video clip 1: Different types of protective equipment used in laboratories
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Introduction & Air Intake The appropriate management of air flow within a laboratory is crucial to the maintenance of a safe and healthy working environment. This video sequence will show the typical ventilation process for laboratories, and will highlight some common problems. Air is drawn from outside and may be passed through any of a variety of filtering media. The air is then conditioned, by either heating or cooling, and then delivered through ducts to the lab. [View Clip]
File size: 114MB
Air Intake, Ceiling diffuser
The terminal end of the air supply duct in the lab is typically covered with a diffuser to enhance the distribution of the air. [View Clip]
File size: 61MB
The air exits the lab via two main pathways. A return air duct may draw some portion of the air into the return air plenum. [View Clip]
File size: 63MB
Exhaust, Fume hood
Air can also be removed from the room by exhaust hoods, which are designed to capture and remove gases and vapors from the breathing zone of lab workers. [Available shortly]
Room Changes Per Hour
The rate at which the air is supplied to, and subsequently removed from, a lab is reported in the units of "room changes per hour". This represents the equivalent volume of the room being exchanged over a set period of time. Recommended room changes for labs can range from 4 to 15 per hour, depending upon the work performed in the lab. [Available shortly]
Air Flow Direction
To prevent the accidental release of contaminants into areas of general access, the air pressure in the lab should be lower than that in corridor areas, so that the flow of air is from the corridor into the lab. To verify the proper direction of flow, tracer gases such as smoke tubes can be used. [Available shortly]
Laboratory Fume Hood
Work involving gases and vapors should be performed within exhaust hoods so that emissions are captured and drawn away from the breathing zone of workers. The flow rate of exhaust hood should be routinely verified to ensure appropriate functionality. Although exhaust hoods can provide protection to workers, they do not provide protection to the product or specimen located in the hood, as ambient air is being drawn across the work surface [Available shortly]
Biological safety cabinet
When products or specimens must also be protected, a biological safety cabinet may be used. These devices offer worker protection by drawing air away from the breathing zone, but also offer product protection by filtering the air before it crosses the work surface. These units may stand alone or may be ducted into the lab ventilation system [Available shortly]
Maintaining appropriate air pressures in a lab is a delicate balance, and malfunctions can result in releases of contaminants. Some common problems to be on the look-out for include:
Modifications to ventilation systems resulting in re-entrainment of exhaust air or the closing off of outside air intakes System alternations or malfunctions that cause the lab air pressure to be higher than the adjoining corridor Failure of exhaust hood fans and Improper work techniques in exhaust hoods � not far enough into the hood or rapid movements disrupting air curtains
Regular monitoring of the work environment can help reduce the instances of such events. [Available shortly]
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