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.