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Part XVII. Services and Trade
- Health Care Facilities and Services
Chemicals in the Health Care Environment
Overview of Chemical Hazards in Health Care
Exposure to potentially hazardous chemicals is a fact of life for health care workers. They are encountered in the course of diagnostic and therapeutic procedures, in laboratory work, in preparation and clean-up activities and even in emanations from patients, to say nothing of the “infrastructure” activities common to all worksites such as cleaning and housekeeping, laundry, painting, plumbing and maintenance work. Despite the constant threat of such exposures and the large numbers of workers involved—in most countries, health care invariably is one of the most labour-intensive industries—this problem has received scant attention from those involved in occupational health and safety research and regulation. The great majority of chemicals in common use in hospitals and other health care settings are not specifically covered under national and international occupational exposure standards. In fact, very little effort has been made to date to identify the chemicals most frequently used, much less to study the mechanisms and intensity of exposures to them and the epidemiology of the effects on the health care workers involved.
This may be changing in the many jurisdictions in which right-to-know laws, such as the Canadian Workplace Hazardous Materials Information Systems (WHMIS) are being legislated and enforced. These laws require that workers be informed of the name and nature of the chemicals to which they may be exposed on the job. They have introduced a daunting challenge to administrators in the health care industry who must now turn to occupational health and safety professionals to undertake a de novo inventory of the identity and location of the thousands of chemicals to which their workers may be exposed.
The wide range of professions and jobs and the complexity of their interplay in the health care workplace require unique diligence and astuteness on the part of those charged with such occupational safety and health responsibilities. A significant complication is the traditional altruistic focus on the care and well-being of the patients, even at the expense of the health and well-being of those providing the services. Another complication is the fact that these services are often required at times of great urgency when important preventive and protective measures may be forgotten or deliberately disregarded.
Categories of Chemical Exposures in the Health Care Setting
Table 1 lists the categories of chemicals encountered in the health care workplace. Laboratory workers are exposed to the broad range of chemical reagents they employ, histology technicians to dyes and stains, pathologists to fixative and preservative solutions (formaldeyde is a potent sensitizer), and asbestos is a hazard to workers making repairs or renovations in older health care facilities.
Table 1. Categories of chemicals used in health care
|
Types of chemicals |
Locations most likely to be found |
|
Disinfectants |
Patient areas |
|
Sterilants |
Central supply |
|
Medicines |
Patient areas |
|
Laboratory reagents |
Laboratories |
|
Housekeeping/maintenance chemicals |
Hospital-wide |
|
Food ingredients and products |
Kitchen |
|
Pesticides |
Hospital-wide |
Even when liberally applied in combating and preventing the spread of infectious agents, detergents, disinfectants and sterilants offer relatively little danger to patients whose exposure is usually of brief duration. Even though individual doses at any one time may be relatively low, their cumulative effect over the course of a working lifetime may, however, constitute a significant risk to health care workers.
Occupational exposures to drugs can cause allergic reactions, such as have been reported over many years among workers administering penicillin and other antibiotics, or much more serious problems with such highly carcinogenic agents as the antineoplastic drugs. The contacts may occur during the preparation or administration of the dose for injection or in cleaning up after it has been administered. Although the danger of this mechanism of exposure had been known for many years, it was fully appreciated only after mutagenic activity was detected in the urine of nurses administering antineoplastic agents.
Another mechanism of exposure is the administration of drugs as aerosols for inhalation. The use of antineoplastic agents, pentamidine and ribavarin by this route has been studied in some detail, but there has been, as of this writing, no report of a systematic study of aerosols as a source of toxicity among health care workers.
Anaesthetic gases represent another class of drugs to which many health care workers are exposed. These chemicals are associated with a variety of biological effects, the most obvious of which are on the nervous system. Recently, there have been reports suggesting that repeated exposures to anaesthetic gases may, over time, have adverse reproductive effects among both male and female workers. It should be recognized that appreciable amounts of waste anaesthetic gases may accumulate in the air in recovery rooms as the gases retained in the blood and other tissues of patients are eliminated by exhalation.
Chemical disinfecting and sterilizing agents are another important category of potentially hazardous chemical exposures for health care workers. Used primarily in the sterilization of non-disposable equipment, such as surgical instruments and respiratory therapy apparatus, chemical sterilants such as ethylene oxide are effective because they interact with infectious agents and destroy them. Alkylation, whereby methyl or other alkyl groups bind chemically with protein-rich entities such as the amino groups in haemoglobiin and DNA, is a powerful biological effect. In intact organisms, this may not cause direct toxicity but should be considered potentially carcinogenic until proven otherwise. Ethylene oxide itself, however, is a known carcinogen and is associated with a variety of adverse health effects, as discussed elsewhere in the Encyclopaedia. The potent alkylation capability of ethylene oxide, probably the most widely-used sterilant for heat-sensitive materials, has led to its use as a classic probe in studying molecular structure.
For years, the methods used in the chemical sterilization of instruments and other surgical materials have carelessly and needlessly put many health care workers at risk. Not even rudimentary precautions were taken to prevent or limit exposures. For example, it was the common practice to leave the door of the sterilizer partially open to allow the escape of excess ethylene oxide, or to leave freshly-sterilized materials uncovered and open to the room air until enough had been assembled to make efficient use of the aerator unit.
The fixation of metallic or ceramic replacement parts so common in dentistry and orthopaedic surgery may be a source of potentially hazardous chemical exposure such as silica. These and the acrylic resins often used to glue them in place are usually biologically inert, but health care workers may be exposed to the monomers and other chemical reactants used during the preparation and application process. These chemicals are often sensitizing agents and have been associated with chronic effects in animals. The preparation of mercury amalgam fillings can lead to mercury exposure. Spills and the spread of mercury droplets is a particular concern since these may linger unnoticed in the work environment for many years. The acute exposure of patients to them appears to be entirely safe, but the long-term health implications of the repeated exposure of health care workers have not been adequately studied.
Finally, such medical techniques as laser surgery, electro-cauterization and use of other radiofrequency and high-energy devices can lead to the thermal degradation of tissues and other substances resulting in the formation of potentially toxic smoke and fumes. For example, the cutting of “plaster” casts made of polyester resin impregnated bandages has been shown to release potentially toxic fumes.
The hospital as a “mini-municipality”
A listing of the varied jobs and tasks performed by the personnel of hospitals and other large health care facilities might well serve as a table of contents for the commercial listings of a telephone directory for a sizeable municipality. All of these entail chemical exposures intrinsic to the particular work activity in addition to those that are peculiar to the health care environment. Thus, painters and maintenance workers are exposed to solvents and lubricants. Plumbers and others engaged in soldering are exposed to fumes of lead and flux. Housekeeping workers are exposed to soaps, detergents and other cleansing agents, pesticides and other household chemicals. Cooks may be exposed to potentially carcinogenic fumes in broiling or frying foods and to oxides of nitrogen from the use of natural gas as fuel. Even clerical workers may be exposed to the toners used in copiers and printers. The occurrence and effects of such chemical exposures are detailed elsewhere in this Encyclopaedia.
One chemical exposure that is diminishing in importance as more and more HCWs quit smoking and more health care facilities become “smoke-free” is “second hand” tobacco smoke.
Unusual chemical exposures in health care
Table 2 presents a partial listing of the chemicals most commonly encountered in health care workplaces. Whether or not they will be toxic will depend on the nature of the chemical and its biological proclivities, the manner, intensity and duration of the exposure, the susceptibilities of the exposed worker, and the speed and effectiveness of any countermeasures that may have been attempted. Unfortunately, a compendium of the nature, mechanisms, effects and treatment of chemical exposures of health care workers has not yet been published.
There are some unique exposures in the health care workplace that substantiate the dictum that a high level of vigilance is necessary to protect workers fully from such risks. For example, it was recently reported that health care workers had been overcome by toxic fumes emanating from a patient under treatment from a massive chemical exposure. Cases of cyanide poisoning arising from patient emissions have also been reported. In addition to the direct toxicity of waste anaesthetic gases to anaesthetists and other personnel in operating theatres, there is the often unrecognized problem created by the frequent use in such areas of high-energy sources which can transform the anaesthetic gases to free radicals, a form in which they are potentially carcinogenic.
Table 2. Chemicals cited Hazardous Substances Database (HSDB)
The following chemicals are listed in the HSDB as being used in some area of the health care environment. The HSDB is produced by the US National Library of Medicine and is a compilation of more than 4,200 chemicals with known toxic effects in commercial use. Absence of a chemical from the list does not imply that it is not toxic, but that it is not present in the HSDB.
|
Use list in the HSDB |
Chemical name |
CAS number* |
|
Disinfectants; antiseptics |
benzylalkonium chloride |
0001-54-5 |
|
Sterilants |
beta-propiolactone |
57-57-8 |
|
Laboratory reagents: |
2,4-xylidine (magenta-base) |
3248-93-9 |
* Chemical Abstracts identification number.
Managing Chemical Hazards in Hospitals
The vast array of chemicals in hospitals, and the multitude of settings in which they occur, call for a systematic approach to their control. A chemical-by-chemical approach to prevention of exposures and their deleterious outcome is simply too inefficient to handle a problem of this scope. Moreover, as noted in the article “Overview of chemical hazards in health care”, many chemicals in the hospital environment have been inadequately studied; new chemicals are constantly being introduced and for others, even some that have become quite familiar (e.g., gloves made of latex), new hazardous effects are only now becoming manifest. Thus, while it is useful to follow chemical-specific control guidelines, a more comprehensive approach is needed whereby individual chemical control policies and practices are superimposed on a strong foundation of general chemical hazard control.
The control of chemical hazards in hospitals must be based on classic principles of good occupational health practice. Because health care facilities are accustomed to approaching health through the medical model, which focuses on the individual patient and treatment rather than on prevention, special effort is required to ensure that the orientation for handling chemicals is indeed preventive and that measures are principally focused on the workplace rather than on the worker.
Environmental (or engineering) control measures are the key to prevention of deleterious exposures. However, it is necessary to train each worker correctly in appropriate exposure prevention techniques. In fact, right-to-know legislation, as described below, requires that workers be informed of the hazards with which they work, as well as of the appropriate safety precautions. Secondary prevention at the level of the worker is the domain of medical services, which may include medical monitoring to ascertain whether health effects of exposure can be medically detected; it also consists of prompt and appropriate medical intervention in the event of accidental exposure. Chemicals that are less toxic must replace more toxic ones, processes should be enclosed wherever possible and good ventilation is essential.
While all means to prevent or minimize exposures should be implemented, if exposure does occur (e.g., a chemical is spilled), procedures must be in place to ensure prompt and appropriate response to prevent further exposure.
Applying the General Principles of Chemical Hazard Control in the Hospital Environment
The first step in hazard control is hazard identification. This, in turn, requires a knowledge of the physical properties, chemical constituents and toxicological properties of the chemicals in question. Material safety data sheets (MSDSs), which are becoming increasingly available by legal requirement in many countries, list such properties. The vigilant occupational health practitioner, however, should recognize that the MSDS may be incomplete, particularly with respect to long-term effects or effects of low-dose chronic exposure. Hence, a literature search may be contemplated to supplement the MSDS material, when appropriate.
The second step in controlling a hazard is characterizing the risk. Does the chemical pose a carcinogenic risk? Is it an allergen? A teratogen? Is it mainly short-term irritancy effects that are of concern? The answer to these questions will influence the way in which exposure is assessed.
The third step in chemical hazard control is to assess the actual exposure. Discussion with the health care workers who use the product in question is the most important element in this endeavour. Monitoring methods are necessary in some situations to ascertain that exposure controls are functioning properly. These may be area sampling, either grab sample or integrated, depending on the nature of the exposure; it may be personal sampling; in some cases, as discussed below, medical monitoring may be contemplated, but usually as a last resort and only as back-up to other means of exposure assessment.
Once the properties of the chemical product in question are known, and the nature and extent of exposure are assessed, a determination could be made as to the degree of risk. This generally requires that at least some dose-response information be available.
After evaluating the risk, the next series of steps is, of course, to control the exposure, so as to eliminate or at least minimize the risk. This, first and foremost, involves applying the general principles of exposure control.
Organizing a Chemical Control Programme in Hospitals
The traditional obstacles
The implementation of adequate occupational health programmes in health care facilities has lagged behind the recognition of the hazards. Labour relations are increasingly forcing hospital management to look at all aspects of their benefits and services to employees, as hospitals are no longer tacitly exempt by custom or privilege. Legislative changes are now compelling hospitals in many jurisdictions to implement control programmes.
However, obstacles remain. The preoccupation of the hospital with patient care, emphasizing treatment rather than prevention, and the staff’s ready access to informal “corridor consultation”, have hindered the rapid implementation of control programmes. The fact that laboratory chemists, pharmacists and a host of medical scientists with considerable toxicological expertise are heavily represented in management has, in general, not served to hasten the development of programmes. The question may be asked, “Why do we need an occupational hygienist when we have all these toxicology experts?” To the extent that changes in procedures threaten to have an impact on the tasks and services provided by these highly skilled personnel, the situation may be made worse: “We cannot eliminate the use of Substance X as it is the best bactericide around.” Or, “If we follow the procedure that you are recommending, patient care will suffer.” Moreover, the “we don’t need training” attitude is commonplace among the health care professions and hinders the implementation of the essential components of chemical hazard control. Internationally, the climate of cost constraint in health care is clearly also an obstacle.
Another problem of particular concern in hospitals is preserving the confidentiality of personal information about health care workers. While occupational health professionals should need only to indicate that Ms. X cannot work with chemical Z and needs to be transferred, curious clinicians are often more prone to push for the clinical explanation than their non-health care counterparts. Ms. X may have liver disease and the substance is a liver toxin; she may be allergic to the chemical; or she may be pregnant and the substance has potential teratogenic properties. While the need to alter the work assignment of particular individuals should not be routine, the confidentiality of the medical details should be protected if it is necessary.
Right-to-know legislation
Many jurisdictions around the world have implemented right-to-know legislation. In Canada, for example, WHMIS has revolutionized the handling of chemicals in industry. This country-wide system has three components: (1) the labelling of all hazardous substances with standardized labels indicating the nature of the hazard; (2) the provision of MSDSs with the constituents, hazards and control measures for each substance; and (3) the training of workers to understand the labels and the MSDSs and to use the product safely.
Under WHMIS in Canada and OSHA’s Hazard Communications requirements in the United States, hospitals have been required to construct inventories of all chemicals on the premises so that those that are “controlled substances” can be identified and addressed according to the legislation. In the process of complying with the training requirements of these regulations, hospitals have had to engage occupational health professionals with appropriate expertise and the spin-off benefits, particularly when bipartite train-the-trainer programmes were conducted, have included a new spirit to work cooperatively to address other health and safety concerns.
Corporate commitment and the role of joint health and safety committees
The most important element in the success of any occupational health and safety programme is corporate commitment to ensure its successful implementation. Policies and procedures regarding the safe handling of chemicals in hospitals must be written, discussed at all levels within the organization and adopted and enforced as corporate policy. Chemical hazard control in hospitals should be addressed by general as well as specific policies. For example, there should be a policy on responsibility for the implementation of right-to-know legislation that clearly outlines each party’s obligations and the procedures to be followed by individuals at each level of the organization (e.g., who chooses the trainers, how much work time is allowed for preparation and provision of training, to whom should communication regarding non-attendance be communicated and so on). There should be a generic spill clean-up policy indicating the responsibility of the worker and the department where the spill occurred, the indications and protocol for notifying the emergency response team, including the appropriate in-hospital and external authorities and experts, follow-up provisions for exposed workers and so on. Specific policies should also exist regarding the handling, storage and disposal of specific classes of toxic chemicals.
Not only is it essential that management be strongly committed to these programmes; the workforce, through its representatives, must also be actively involved in the development and implementation of policies and procedures. Some jurisdictions have legislatively mandated joint (labour-management) health and safety committees that meet at a minimum prescribed interval (bimonthly in the case of Manitoba hospitals), have written operating procedures and keep detailed minutes. Indeed in recognizing the importance of these committees, the Manitoba Workers’ Compensation Board (WCB) provides a rebate on WCB premiums paid by employers based on the successful functioning of these committees. To be effective, the members must be appropriately chosen—specifically, they must be elected by their peers, knowledgeable about the legislation, have appropriate education and training and be allotted sufficient time to conduct not only incident investigations but regular inspections. With respect to chemical control, the joint committee has both a pro-active and a re-active role: assisting in setting priorities and developing preventive policies, as well as serving as a sounding board for workers who are not satisfied that all appropriate controls are being implemented.
The multidisciplinary team
As noted above, the control of chemical hazards in hospitals requires a multidisciplinary endeavour. At a minimum, it requires occupational hygiene expertise. Generally hospitals have maintenance departments that have within them the engineering and physical plant expertise to assist a hygienist in determining whether workplace alterations are necessary. Occupational health nurses also play a prominent role in evaluating the nature of concerns and complaints, and in assisting an occupational physician in ascertaining whether clinical intervention is warranted. In hospitals, it is important to recognize that numerous health care professionals have expertise that is quite relevant to the control of chemical hazards. It would be unthinkable to develop policies and procedures for the control of laboratory chemicals without the involvement of lab chemists, for example, or procedures for handling anti-neoplastic drugs without the involvement of the oncology and pharmacology staff. While it is wise for occupational health professionals in all industries to consult with line staff prior to implementing control measures, it would be an unforgivable error to fail to do so in health care settings.
Data collection
As in all industries, and with all hazards, data need to be compiled both to help in priority setting and in evaluating the success of programmes. With respect to data collection on chemical hazards in hospitals, minimally, data need to be kept regarding accidental exposures and spills (so that these areas can receive special attention to prevent recurrences); the nature of concerns and complaints should be recorded (e.g., unusual odours); and clinical cases need to be tabulated, so that, for example, an increase in dermatitis from a given area or occupational group could be identified.
Cradle-to-grave approach
Increasingly, hospitals are becoming cognizant of their obligation to protect the environment. Not only the workplace hazardous properties, but the environmental properties of chemicals are being taken into consideration. Moreover, it is no longer acceptable to pour hazardous chemicals down the drain or release noxious fumes into the air. A chemical control programme in hospitals must, therefore, be capable of tracking chemicals from their purchase and acquisition (or, in some cases, synthesis on site), through the work handling, safe storage and finally to their ultimate disposal.
Conclusion
It is now recognized that there are thousands of potentially very toxic chemicals in the work environment of health care facilities; all occupational groups may be exposed; and the nature of the exposures are varied and complex. Nonetheless, with a systematic and comprehensive approach, with strong corporate commitment and a fully informed and involved workforce, chemical hazards can be managed and the risks associated with these chemicals controlled.
Waste Anaesthetic Gases
The use of inhaled anaesthetics was introduced in the decade of 1840 to 1850. The first compounds to be used were diethyl ether, nitrous oxide and chloroform. Cyclopropane and trichloroethylene were introduced many years later (circa 1930-1940), and the use of fluoroxene, halothane and methoxiflurane began in the decade of the 1950s. By the end of the 1960s enflurane was being used and, finally, isoflurane was introduced in the 1980s. Isoflurane is now considered the most widely used inhalation anaesthetic even though it is more expensive than the others. A summary of the physical and chemical characteristics of methoxiflurane, enflurane, halothane, isoflurane and nitrous oxide, the most commonly used anaesthetics, is shown in table 1 (Wade and Stevens 1981).
Table 1. Properties of inhaled anaesthetics
|
Isoflurane, |
Enflurane, |
Halothane, |
Methoxyflurane, |
Dinitrogen oxide, |
|
|
Molecular weight |
184.0 |
184.5 |
197.4 |
165.0 |
44.0 |
|
Boiling point |
48.5°C |
56.5°C |
50.2°C |
104.7°C |
— |
|
Density |
1.50 |
1.52 (25°C) |
1.86 (22°C) |
1.41 (25°C) |
— |
|
Vapour pressure at 20 °C |
250.0 |
175.0 (20°C) |
243.0 (20°C) |
25.0 (20°C) |
— |
|
Smell |
Pleasant, sharp |
Pleasant, like ether |
Pleasant, sweet |
Pleasant, fruity |
Pleasant, sweet |
|
Separation coefficients: |
|||||
|
Blood/gas |
1.40 |
1.9 |
2.3 |
13.0 |
0.47 |
|
Brain/gas |
3.65 |
2.6 |
4.1 |
22.1 |
0.50 |
|
Fat/gas |
94.50 |
105.0 |
185.0 |
890.0 |
1.22 |
|
Liver/gas |
3.50 |
3.8 |
7.2 |
24.8 |
0.38 |
|
Muscle/gas |
5.60 |
3.0 |
6.0 |
20.0 |
0.54 |
|
Oil/gas |
97.80 |
98.5 |
224.0 |
930.0 |
1.4 |
|
Water/gas |
0.61 |
0.8 |
0.7 |
4.5 |
0.47 |
|
Rubber/gas |
0.62 |
74.0 |
120.0 |
630.0 |
1.2 |
|
Metabolic rate |
0.20 |
2.4 |
15–20 |
50.0 |
— |
All of them, with the exception of nitrous oxide (N2O), are hydrocarbons or chlorofluorinated liquid ethers that are applied by vapourization. Isoflurane is the most volatile of these compounds; it is the one that is metabolized at the lowest rate and the one that is least soluble in blood, in fats and in the liver.
Normally, N2O, a gas, is mixed with a halogenated anaesthetic, although they are sometimes used separately, depending on the type of anaesthesia that is required, the characteristics of the patient and the work habits of the anaesthetist. The normally used concentrations are 50 to 66% N2O and up to 2 or 3% of the halogenated anaesthetic (the rest is usually oxygen).
The anaesthesia of the patient is usually started by the injection of a sedative drug followed by an inhaled anaesthetic. The volumes given to the patient are in the order of 4 or 5 litres/minute. Parts of the oxygen and of the anaesthetic gases in the mixture are retained by the patient while the remainder is exhaled directly into the atmosphere or is recycled into the respirator, depending among other things on the type of mask used, on whether the patient is intubated and on whether or not a recycling system is available. If recycling is available, exhaled air can be recycled after it is cleaned or it can be vented to the atmosphere, expelled from the operating room or aspirated by a vacuum. Recycling (closed circuit) is not a common procedure and many respirators do not have exhaust systems; all the air exhaled by the patient, including the waste anaesthetic gases, therefore, ends up in the air of the operating room.
The number of workers occupationally exposed to waste anaesthetic gases is high, because it is not only the anaesthetists and their assistants who are exposed, but all the other people who spend time in operating rooms (surgeons, nurses and support staff), the dentists who perform odontological surgery, the personnel in delivery rooms and intensive care units where patients may be under inhaled anaesthesia and veterinary surgeons. Similarly, the presence of waste anaesthetic gases is detected in recovery rooms, where they are exhaled by patients who are recovering from surgery. They are also detected in other areas adjacent to operating rooms because, for reasons of asepsis, operating rooms are kept at positive pressure and this favours the contamination of surrounding areas.
Health Effects
Problems due to the toxicity of anaesthetic gases were not seriously studied until the 1960s, even though a few years after the use of inhaled anaesthetics became common, the relationship between the illnesses (asthma, nephritis) that affected some of the first professional anaesthetists and their work as such was already suspected (Ginesta 1989). In this regard the appearance of an epidemiological study of more than 300 anaesthetists in the Soviet Union, the Vaisman (1967) survey, was the starting point for several other epidemiological and toxicological studies. These studies—mostly during the 1970s and the first half of the 1980s—focused on the effects of anaesthetic gases, in most cases nitrous oxide and halothane, on people occupationally exposed to them.
The effects observed in most of these studies were an increase in spontaneous abortions among women exposed during or before pregnancy, and among women partners of exposed men; an increase in congenital malformations in children of exposed mothers; and the occurrence of hepatic, renal and neurological problems and of some types of cancer in both men and women (Bruce et al. 1968, 1974; Bruce and Bach 1976). Even though the toxic effects of nitrous oxide and of halothane (and probably its substitutes as well) on the body are not exactly the same, they are commonly studied together, given that exposure generally occurs simultaneously.
It appears likely that there is a correlation between these exposures and an increased risk, particularly for spontaneous abortions and congenital malformations in children of women exposed during pregnancy (Stoklov et al. 1983; Spence 1987; Johnson, Buchan and Reif 1987). As a result, many of the people exposed have expressed great concern. Rigorous statistical analysis of these data, however, casts doubt on the existence of such a relationship. More recent studies reinforce these doubts while chromosomal studies yield ambiguous results.
The works published by Cohen and colleagues (1971, 1974, 1975, 1980), who carried out extensive studies for the American Society of Anaesthetists (ASA), constitute a fairly extensive series of observations. Follow-up publications criticized some of the technical aspects of the earlier studies, particularly with respect to the sampling methodology and, especially, the proper selection of a control group. Other deficiencies included lack of reliable information on the concentrations to which the subjects had been exposed, the methodology for dealing with false positives and the lack of controls for factors such as tobacco and alcohol use, prior reproductive histories and voluntary infertility. Consequently, some of the studies are now even considered invalid (Edling 1980; Buring et al. 1985; Tannenbaum and Goldberg 1985).
Laboratory studies have shown that exposure of animals to ambient concentrations of anaesthetic gases equivalent to those found in operating rooms does cause deterioration in their development, growth and adaptive behaviour (Ferstandig 1978; ACGIH 1991). These are not conclusive, however, since some of these experimental exposures involved anaesthetic or subanaesthetic levels, concentrations significantly higher than the levels of waste gases usually found in operating room air (Saurel-Cubizolles et al. 1994; Tran et al. 1994).
Nevertheless, even acknowledging that a relationship between the deleterious effects and exposures to waste anaesthetic gases has not been definitively established, the fact is that the presence of these gases and their metabolites is readily detected in the air of operating rooms, in exhaled air and in biological fluids. Accordingly, since there is concern about their potential toxicity, and because it is technically feasible to do so without inordinate effort or expense, it would be prudent to take steps to eliminate or reduce to a minimum the concentrations of waste anaesthetic gases in operating rooms and nearby areas (Rosell, Luna and Guardino 1989; NIOSH 1994).
Maximum Allowable Exposure Levels
The American Conference of Governmental Industrial Hygienists (ACGIH) has adopted a threshold limit value-time weighted average (TLV-TWA) of 50 ppm for nitrous oxide and halothane (ACGIH 1994). The TLV-TWA is the guideline for the production of the compound, and the recommendations for operating rooms are that its concentration be kept lower, at a level below 1 ppm (ACGIH 1991). NIOSH sets a limit of 25 ppm for nitrous oxide and of 1 ppm for halogenated anaesthetics, with the additional recommendation that when they are used together, the concentration of halogenated compounds be reduced to a limit of 0.5 ppm (NIOSH 1977b).
With regard to values in biological fluids, the recommended limit for nitrous oxide in urine after 4 hours of exposure at average ambient concentrations of 25 ppm ranges from 13 to 19 μg/L, and for 4 hours of exposure at average ambient concentrations of 50 ppm, the range is 21 to 39 μg/L (Guardino and Rosell 1995). If exposure is to a mixture of a halogenated anaesthetic and nitrous oxide, the measurement of the values from nitrous oxide is used as the basis for controlling exposure, because as higher concentrations are used, quantification becomes easier.
Analytical Measurement
Most of the procedures described for measuring residual anaesthetics in air are based on the capture of these compounds by adsorption or in an inert bag or container, later to be analysed by gas chromatography or infrared spectroscopy (Guardino and Rosell 1985). Gas chromatography is also employed to measure nitrous oxide in urine (Rosell, Luna and Guardino 1989), while isoflurane is not readily metabolized and is therefore seldom measured.
Common Levels of Residual Concentrations in the Air of Operating Rooms
In the absence of preventive measures, such as the extraction of residual gases and/or introducing an adequate supply of new air into the operating suite, personal concentrations of more than 6,000 ppm of nitrous oxide and 85 ppm of halothane have been measured (NIOSH 1977). Concentrations of up to 3,500 ppm and 20 ppm, respectively, in the ambient air of operating rooms, have been measured. The implementation of corrective measures can reduce these concentrations to values below the environmental limits cited earlier (Rosell, Luna and Guardino 1989).
Factors that Affect the Concentration of Waste Anaesthetic Gases
The factors which most directly affect the presence of waste anaesthetic gases in the environment of the operating room are the following.
Method of anaesthesia. The first question to consider is the method of anaesthesia, for example, whether or not the patient is intubated and the type of face mask being used. In dental, laryngeal or other forms of surgery in which intubation is precluded, the patient’s expired air would be an important source of emissions of waste gases, unless equipment specifically designed to trap these exhalations is properly placed near the patient’s breathing zone. Accordingly, dental and oral surgeons are considered to be particularly at risk (Cohen, Belville and Brown 1975; NIOSH 1977a), as are veterinary surgeons (Cohen, Belville and Brown 1974; Moore, Davis and Kaczmarek 1993).
Proximity to the focus of emission. As is usual in industrial hygiene, when the known point of emission of a contaminant exists, proximity to the source is the first factor to consider when dealing with personal exposure. In this case, the anaesthetists and their assistants are the persons most directly affected by the emission of waste anaesthetic gases, and personal concentrations have been measured in the order of two times the average levels found in the air of operating rooms (Guardino and Rosell 1985).
Type of circuit. It goes without saying that in the few cases in which closed circuits are used, with reinspiration after the cleansing of the air and the resupply of oxygen and the necessary anaesthetics, there will be no emissions except in the case of equipment malfunction or if a leak exists. In other cases, it will depend on the characteristics of the system used, as well as on whether or not it is possible to add an extraction system to the circuit.
The concentration of anaesthetic gases. Another factor to take into account is the concentrations of the anaesthetics used since, obviously, those concentrations and the amounts found in the air of the operating room are directly related (Guardino and Rosell 1985). This factor is especially important when it comes to surgical procedures of long duration.
Type of surgical procedures. The duration of the operations, the time elapsed between procedures done in the same operating room and the specific characteristics of each procedure—which often determine which anaesthetics are used—are other factors to consider. The duration of the operation directly affects the residual concentration of anaesthetics in the air. In operating rooms where procedures are scheduled successively, the time elapsed between them also affects the presence of residual gases. Studies done in large hospitals with uninterrupted use of the operating rooms or with emergency operating rooms that are used beyond standard work schedules, or in operating rooms used for prolonged procedures (transplants, laryngotomies), show that substantial levels of waste gases are detected even before the first procedure of the day. This contributes to increased levels of waste gases in subsequent procedures. On the other hand, there are procedures that require temporary interruptions of inhalation anaesthesia (where extracorporeal circulation is needed, for example), and this also interrupts the emission of waste anaesthetic gases into the environment (Guardino and Rosell 1985).
Characteristics specific to the operating room. Studies done in operating rooms of different sizes, design and ventilation (Rosell, Luna and Guardino 1989) have demonstrated that these characteristics greatly influence the concentration of waste anaesthetic gases in the room. Large and non-partitioned operating rooms tend to have the lowest measured concentrations of waste anaesthetic gases, while in small operating rooms (e.g., paediatric operating rooms) the measured concentrations of waste gases are usually higher. The general ventilation system of the operating room and its proper operation is a fundamental factor for the reduction of the concentration of waste anaesthetics; the design of the ventilation system also affects the circulation of waste gases within the operating room and the concentrations in different locations and at various heights, something that can be easily verified by carefully taking samples.
Characteristics specific to the anaesthesia equipment. The emission of gases into the environment of the operating room depends directly on the characteristics of the anaesthesia equipment used. The design of the system, whether it includes a system for the return of excess gases, whether it can be attached to a vacuum or vented out of the operating room, whether it has leaks, disconnected lines and so on are always to be considered when determining the presence of waste anaesthetic gases in the operating room.
Factors specific to the anaesthetist and his or her team. The anaesthetist and his or her team are the last element to consider, but not necessarily the least important. Knowledge of the anaesthesia equipment, of its potential problems and the level of maintenance it receives—both by the team and by the maintenance staff in the hospital—are factors that affect very directly the emission of waste gases into the air of the operating room (Guardino and Rosell 1995). It has been clearly shown that, even when using adequate technology, the reduction of the ambient concentrations of anaesthetic gases cannot be achieved if a preventive philosophy is absent from the work routines of anaesthetists and their assistants (Guardino and Rosell 1992).
Preventive Measures
The basic preventive actions required to reduce occupational exposure to waste anaesthetic gases effectively can be summarized in the following six points:
- Anaesthetic gases should be thought of as occupational hazards. Even if from a scientific standpoint it has not been conclusively shown that anaesthetic gases have a serious deleterious effect on the health of people who are occupationally exposed, there is a high probability that some of the effects mentioned here are directly related to the exposure to waste anaesthetic gases. For that reason it is a good idea to consider them toxic occupational hazards.
- Scavenger systems should be used for waste gases. Scavenger systems are the most effective technical hardware for the reduction of waste gases in the air of the operating room (NIOSH 1975). These systems must fulfil two basic principles: they must store and/or adequately eliminate the whole volume of air expired by the patient, and they must be designed to guarantee that neither the respiration of the patient nor the proper functioning of the anaesthesia equipment will be affected—with separate safety devices for each function. The techniques most commonly employed are: a direct connection to a vacuum outlet with a flexible regulating chamber that allows for the discontinuous emission of gases of the respiratory cycle; directing the flow of the gases exhaled by the patient to the vacuum without a direct connection; and directing the flow of gases coming from the patient to the return of the ventilation system installed in the operating room and expelling these gases from the operating room and from the building. All these systems are technically easy to implement and very cost-efficient; the use of installed respirators as part of the design is recommended. In cases where systems that eliminate waste gases directly cannot be used because of the special characteristics of a procedure, localized extraction can be employed near the source of emission as long as it does not affect the general ventilation system or the positive pressure in the operating room.
- General ventilation with a minimum of 15 renewals/hour in the operating room should be guaranteed. The general ventilation of the operating room should be perfectly regulated. It should not only maintain positive pressure and respond to the thermohygrometric characteristics of the ambient air, but should also provide a minimum of 15 to 18 renewals per hour. Also, a monitoring procedure should be in place to ensure its proper functioning.
- Preventive maintenance of the anaesthesia circuit should be planned and regular. Preventive maintenance procedures should be set up that include regular inspections of the respirators. Verifying that no gases are being emitted to the ambient air should be part of the protocol followed when the equipment is first turned on, and its proper functioning with regard to the safety of the patient should be checked. The proper functioning of the anaesthesia circuit should be verified by checking for leaks, periodically replacing filters and checking the safety valves.
- Environmental and biological controls should be used. The implementation of environmental and biological controls provides information not only about the correct functioning of the various technical elements (extraction of gases, general ventilation) but also about whether the working procedures are adequate for curtailing the emission of waste gases into the air. Today these controls do not present technical problems and they can be implemented economically, which is why they are recommended.
- Education and training of the exposed personnel is crucial. Achieving an effective reduction of occupational exposure to waste anaesthetic gases requires educating all operating room personnel about the potential risks and training them in the required procedures. This is particularly applicable to anaesthetists and their assistants who are most directly involved and those responsible for the maintenance of the anaesthesia and air-conditioning equipment.
Conclusion
Although not definitively proven, there is enough evidence to suggest that exposures to waste anaesthetic gases may be harmful to HCWs. Stillbirths and congenital malformations in infants born to female workers and to the spouses of male workers represent the major forms of toxicity. Since it is technically feasible at a low cost, it is desirable to reduce the concentration of these gases in the ambient air in operating rooms and adjacent areas to a minimum. This requires not only the use and correct maintenance of anaesthesia equipment and ventilation/air conditioning systems but also the education and training of all personnel involved, especially anaesthetists and their assistants, who generally are exposed to higher concentrations. Given the work conditions peculiar to operating rooms, indoctrination in the correct work habits and procedures is very important in trying to reduce the amounts of anaesthetic waste gases in the air to a minimum.
Health Care Workers and Latex Allergy
With the advent of the universal precautions against bloodborne infections which dictate the use of gloves whenever HCWs are exposed to patients or materials that might be infected with hepatitis B or HIV, the frequency and severity of allergic reactions to natural rubber latex (NRL) have zoomed upward. For example, the Department of Dermatology at the Erlangen-Nuremberg University in Germany reported a 12-fold increase in the number of patients with latex allergy between 1989 and 1995. More serious systemic manifestations increased from 10.7% in 1989 to 44% in 1994-1995 (Hesse et al. 1996).
It seems ironic that so much difficulty is attributable to rubber gloves when they were intended to protect the hands of nurses and other HCWs when they were originally introduced toward the end of the nineteenth century. This was the era of antiseptic surgery in which instruments and operative sites were bathed in caustic solutions of carbolic acid and bichloride of mercury. These not only killed germs but they also macerated the hands of the surgical team. According to what has become a romantic legend, William Stewart Halsted, one of the surgical “giants” of the time who is credited with a host of contributions to the techniques of surgery, is said to have “invented” rubber gloves around 1890 to make it more pleasant to hold hands with Caroline Hampton, his scrub nurse, whom he later married (Townsend 1994). Although Halsted may be credited with introducing and popularizing the use of rubber surgical gloves in the United States, many others had a hand in it, according to Miller (1982) who cited a report of their use in the United Kingdom published a half century earlier (Acton 1848).
Latex Allergy
Allergy to NRL is succinctly described by Taylor and Leow (see the article “Rubber contact dermatitis and latex allergy” in the chapter Rubber industry) as “an immunoglobulin E-mediated, immediate, Type I allergic reaction, most always due to NRL proteins present in medical and non-medical latex devices. The spectrum of clinical signs ranges from contact urticaria, generalized urticaria, allergic rhinitis, allergic conjunctivitis, angioedema (severe swelling) and asthma (wheezing) to anaphylaxis (severe, life-threatening allergic reaction)”. Symptoms may result from direct contact of normal or inflamed skin with gloves or other latex-containing materials or indirectly by mucosal contact with or inhalation of aerosolized NRL proteins or talcum powder particles to which NRL proteins have adhered. Such indirect contact can cause a Type IV reaction to the rubber accelerators. (Approximately 80% of “latex glove allergy” is actually a Type IV reaction to the accelerators.) The diagnosis is confirmed by patch, prick, scratch or other skin sensitivity tests or by serological studies for the immune globulin. In some individuals, the latex allergy is associated with allergy to certain foods (e.g., banana, chestnuts, avocado, kiwi and papaya).
While most common among health care workers, latex allergy is also found among employees in rubber manufacturing plants, other workers who habitually use rubber gloves (e.g., greenhouse workers (Carillo et al. 1995)) and in patients with a history of multiple surgical procedures (e.g., spina bifida, congenital urogenital abnormalities, etc.) (Blaycock 1995). Cases of allergic reactions after the use of latex condoms have been reported (Jonasson, Holm and Leegard 1993), and in one case, a potential reaction was averted by eliciting a history of an allergic reaction to a rubber swimming cap (Burke, Wilson and McCord 1995). Reactions have occurred in sensitive patients when hypodermic needles used to prepare doses of parenteral medications picked up NRL protein as they were pushed through the rubber caps on the vials.
According to a recent study of 63 patients with NRL allergy, it took an average of 5 years of working with latex products for the first symptoms, usually a contact urticaria, to develop. Some also had rhinitis or dyspnoea. It took, on average, an additional 2 years for the appearance of lower respiratory tract symptoms (Allmeers et al. 1996).
Frequency of latex allergy
To determine the frequency of NRL allergy, allergy tests were performed on 224 employees at the University of Cincinnati College of Medicine, including nurses, laboratory technicians, physicians, respiratory therapists, housekeeping and clerical workers (Yassin et al. 1994). Of these, 38 (17%) tested positive to latex extracts; the incidence ranged from 0% among housekeeping workers to 38% among dental staff. Exposure of these sensitized individuals to latex caused itching in 84%, a skin rash in 68%, urticaria in 55%, lachrymation and ocular itching in 45%, nasal congestion in 39% and sneezing in 34%. Anaphylaxis occurred in 10.5%.
In a similar study at the University of Oulo in Finland, 56% of 534 hospital employees who used protective latex or vinyl gloves on a daily basis had skin disorders related to the usage of the gloves (Kujala and Reilula 1995). Rhinorrhoea or nasal congestion was present in 13% of workers who used powdered gloves. The prevalence of both skin and respiratory symptoms was significantly higher among those who used the gloves for more than 2 hours a day.
Valentino and colleagues (1994) reported latex induced asthma in four health care workers in an Italian regional hospital, and the Mayo Medical Center in Rochester Minnesota, where 342 employees who reported symptoms suggestive of latex allergy were evaluated, recorded 16 episodes of latex-related anaphylaxis in 12 subjects (six episodes occurred after skin testing) (Hunt et al. 1995). The Mayo researchers also reported respiratory symptoms in workers who did not wear gloves but worked in areas where large numbers of gloves were being used, presumably due to air-borne talcum powder/latex protein particles.
Control and Prevention
The most effective preventive measure is modification of standard procedures to replace the use of gloves and equipment made with NRL with similar items made of vinyl or other non-rubber materials. This requires involvement of the purchasing and supply departments, which should also mandate the labelling of all latex-containing items so that they may be avoided by individuals with latex sensitivity. This is important not only to the staff but also to patients who may have a history suggestive of latex allergy. Aerosolized latex, from latex powder, is also problematic. HCWs who are allergic to latex and who do not use latex gloves may still be affected by the powdered latex gloves used by co-workers. A significant problem is presented by the wide variation in content of latex allergen among gloves from different manufacturers and, indeed, among different lots of gloves from the same manufacturer.
Glove manufacturers are experimenting with gloves using formulations with smaller amounts of NRL as well as coatings that will obviate the need for talcum powder to make the gloves easy to put on and take off. The goal is to provide comfortable, easy to wear, non-allergenic gloves that still provide effective barriers to the transmission of the hepatitis B virus, HIV and other pathogens.
A careful medical history with a particular emphasis on prior latex exposures should be elicited from all health care workers who present symptoms suggestive of latex allergy. In suspect cases, evidence of latex sensitivity may be confirmed by skin or serological testing. Since there is evidently a risk of provoking an anaphylactic reaction, the skin testing should only be performed by experienced medical personnel.
At the present time, allergens for desensitization are not available so that the only remedy is avoidance of exposure to products containing NRL. In some instances, this may require a change of job. Weido and Sim (1995) at the University of Texas Medical Branch at Galveston suggest advising individuals in high-risk groups to carry self-injectable epinephrine to use in the event of a systemic reaction.
Following the appearance of several clusters of latex allergy cases in 1990, the Mayo Medical Center in Rochester, Minnesota, formed a multidisciplinary work group to address the problem (Hunt et al. 1996). Subsequently, this was formalized in a Latex Allergy Task Force with members from the departments of allergy, preventive medicine, dermatology and surgery as well as the Director of Purchasing, the Surgical Nursing Clinical Director and the Director of Employee Health. Articles on latex allergy were published in staff newsletters and information bulletins to educate the 20,000 member workforce to the problem and to encourage those with suggestive symptoms to seek medical consultation. A standardized approach to testing for latex sensitivity and techniques for quantifying the amount of latex allergen in manufactured products and the amount and particle size of air-borne latex allergen were developed. The latter proved to be sufficiently sensitive to measure the exposure of individual workers while performing particular high-risk tasks. Steps were initiated to monitor a gradual transition to low-allergen gloves (an incidental effect was a lowering of their cost by concentrating glove purchases among the fewer vendors who could meet the low allergen requirements) and to minimize exposures of staff and patients with known sensitivity to NLR.
To alert the public to the risks of NLR allergy, a consumer group, the Delaware Valley Latex Allergy Support Network has been formed. This group has created an Internet website (http://www.latex.org) and maintains a toll-free telephone line (1-800 LATEXNO) to provide up-to-date factual information about latex allergy to persons with this problem and those who care for them. This organization, which has a Medical Advisory Group, maintains a Literature Library and a Product Center and encourages the exchange of experiences among those who have had allergic reactions.
Conclusion
Latex allergies are becoming an increasingly important problem among health care workers. The solution lies in minimizing contact with latex allergen in their work environment, especially by substituting non-latex surgical gloves and appliances.
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