Health and Safety in Medical Laboratories*

Bulletin of the World Health Organization, 60 (1): 9- 16 (1982) Health and safety in medical laboratories* J. M. HARRINGTON' There has been a large increase in the number ofpersons employed in medical laboratories in the last 25 years. These workers are exposed to a variety of infective agents in the course oftheir work, the most important being Mycobacterium tuberculosis, Salmonella typhi, Brucella spp., and serum hepatitis virus. Chemical and physical hazards include toxic chemicals, lacerations, skin disease, and possibly cancer. Current knowledge ofsafe workingpractice in laboratories leaves much to be desired and there is an urgent needfor both internationally agreed codes ofsafeprac- tice and the development of guidelines for the medical surveillance of laboratory workers. The World Health Organization is developing such guidelines in an attempt to protect the health of workers employed in the investigation of ill health in others. The technological advances of the past 150 years have transformed medicine from an art to a modern science. A growing number of clinical investigations are available to the phys- ician and there is an increasing need for technicians to perform these laboratory tests. The advent of nationalized health services in many countries has resulted in the employment of large numbers of people in medical and paramedical occupations. For example, in the United Kingdom, approximately 1 out of every 20 workers is employed in the National Health Service and experience in the United States of America suggests that the demand for more health care will continue. Western European countries have a doctor to patient ratio as high as 1 per 1000 population, and ancillary workers in the health field generally outnumber the physicians. Medical laboratory workers form one of the larger subgroups and, in England and Wales, there are currently more than 25 000. Such work is not without its occupational hazards and these risks have recently received considerable publicity as a result of some unfortunate laboratory-acquired infections. Ironically, the global extinction of smallpox as an endemic disease coincided with two deaths from smallpox in the United Kingdom, both of which were traced back to laboratory sources of the virus. These isolated events have focused attention on the microbiological hazards of laboratory work but, at the same time, have obscured the degree of risk and overshadowed the chemical and physical hazards inherent in laboratory activities. The purpose of this article is to review the risks associated with work in medical laboratories and to outline practical ways in which health and safety measures can be instituted to minimize them. OCCUPATIONAL HAZARDS General considerations Laboratory workers are exposed to a wide range of hazards associated with the materials they employ and the methods they use in the course of their work. The subject has been of * A French translation of this article will appear in a later issue of the Bulletin. Professor of Occupational Health, Faculty of Medicine, University of Birmingham, Birmingham B15 2TJ, England. 4139 -9- 10 J. M. HARRINGTON increasing interest in recent years and the hazards to health professionals have been re- viewed by Tolonena and Harrington.b,C Research establishments may be especially hazardous places as the danger associated with a substance or process may not be realized until some unforeseen accident, illness, or death occurs. Routine and diagnostic laboratories handle a wide range of materials and a large number of potentially dangerous, pathogenic agents. The control of many infectious diseases following the introduction of effective anti- microbial drugs has, moreover, added a new and insidious danger to the laboratory workers' job. There is now less likelihood that a particular specimen contains pathogenic material, and this can lull the laboratory technician into a false sense of security. For example, in the United Kingdom pulmonary tuberculosis is now a relatively rare disease, yet it is sometimes discovered inadvertently during post-mortem examination or during the analysis of a sputum specimen submitted for cytological rather than bacteriological analysis. Moreover, in these circumstances, the organism is frequently resistant to first line antituberculosis therapy and is therefore especially dangerous. In addition to the handling of infective or potentially infective material, normal laboratory practice also includes the use of chemical reagents, gases, and solvents that may consti- tute a non-microbiological hazard. These agents may be explosive, flammable, or toxic, and fires, gassings, and explosions occasionally occur in laboratories. To these immediate dangers must be added the longer term risk involved in handling carcinogenic chemical reagents. The literature on medical laboratory hazards has largely centred on infections and, therefore, on microbiological establishments. This is partly because laboratory-acquired infections tend to be more easily remembered than other hazardous events. The cause and effect pathway may also be clearer although the mode of transmission for most laboratory infections remains speculative; a large number of reports of infections are anecdotal and few are more than case reports. Such circumstances preclude an accurate assessment of risk for even the more unusual infective agents and it is likely that infections due to the commoner organisms such as streptococci or staphylococci are underreported. It is often difficult to acquire definitive evidence that an infection common to the community at large has, in a particular instance, been acquired in the laboratory. Nevertheless, the first human cases of several diseases were seen in laboratory workers, e.g., herpes B virus, American Q fever, Marburg disease, louping-ill, and Newcastle disease. Infectious diseases Early attempts to survey large populations of laboratory workers were little more than collections of cases. The surveys ofSulkin and Pike are among the most extensive and in one of the later reports Pike describes 3921 cases.d Attempts to link the infections with specific laboratory accidents or incidents were only partially successful. In a review of 426 cases of laboratory infections covering 32 diseases in 12 countries, Phillips noted that tuberculosis, Q fever, brucellosis, psittacosis, and tularaemia were most common. However, in over 80% of the cases, it was difficult to establish the incident that had precipitated the infection. The most frequently cited causes were self-inoculation, aerosol spread, and glassware injuries. Occasionally, a single laboratory can be the source of widespread illness; an example of this was reported from the USSR, where there were 46 cases of laboratory-acquired encephalitis a TOLONEN, M. Occupational hazards in health professions. A review. Working group on occupational hazards in hospitals, The Hague, 19- 21 October 1981. b HARRINGTON, J. M. The occupational hazards of medical laboratory work. Laboratory practice, 29: 626- 629 (1980). c HARRINGTON, J. M. The health industry. In: McDonald, J. C., ed., Recent advances in occupational health, London, Churchill Livingstone (in press). d PIKE, R. M. Laboratory-associated infections: summary and analysis of 3921 cases. Health laboratory science, 13: 105-114 (1976). HEALTH AND SAFETY IN MEDICAL LABORATORIES 11 between 1950 and 1963, 24 of which resulted from a single accident in a laboratory handling Venezuelan equine encephalitis. Tuberculosis This disease has been traditionally considered an occupational disease of health workers. The risk is now more insidious because, in several western European countries, the diagnosis is made post mortem in up to half of all reported cases in the general population. These occupational risks were not quantified until 1957 when Reide reported that for British pathologists the risk of acquiring tuberculosis was many times higher than for a comparable population of post office workers. Studies undertaken between 1971 and 1974 by the present author confirmed a continuing threat to the health of British laboratory personnel, when it was noted that laboratory technicians were at greatest risk (7 times higher than for a comparison population), medically qualified staff slightly lower (4 times that for a comparison population), with clerical staff having a 2-fold excess. Morbid anatomy department staff and, in particular, post-mortem room technicians were particu- larly at risk, but it is disturbing to note that non-technical personnel such as clerks and secretaries also ran a higher risk than their counterparts outside the laboratory. There is little information on the relative risks to laboratory staff in countries where pulmonary tuberculosis is more prevalent in the general population, though it could be pre- sumed than a higher population prevalence would be translated into a higher laboratory risk. Alternatively, a high community prevalence might ensure that laboratory personnel take greater care with, say, sputum specimens than do their opposite numbers in countries where the disease is generally rare. Serum hepatitis Serum hepatitis is usually transmitted parenterally, the first outbreaks having been described in association with vaccination procedures for smallpox and arsphenamine therapy for venereal disease. Infection with the type B hepatitis virus has become of much greater significance during the last decade or so, and severe, even fatal, outbreaks of the disease have occurred in association

Load more