of polyvinyl alcohol (PVA)-fixed fecal smears, poses potential toxic and fire hazards. Again, Hemo-De has successfully replaced xylene in both the carbol-xylene and xylene steps of the trichrome procedure (33). Other substitutes are available as well (e.g., Hemo-Sol [Fisher Scientific]). Check with your local pathology departments or reagent suppliers for other alternatives.
12. Mercuric chloride, used in PVA and in Schaudinn’s fixative, presents both a toxic hazard and a disposal problem. Copper sulfate has been suggested as a substitute for mercuric chloride (35, 36); however, protozoan morphology is not as clear and precise when this formula is used. The use of zinc rather than copper gives fairly good morphology when the trichrome stain is used (35).
Note Information on other substances is provided in Table 11.5.
Current OSHA Regulations for the Use of Formaldehyde
Formaldehyde has been in use for over a century as a disinfectant and preservative; it is also found in a number of industrial products. There is disagreement about the carcinogenic potential of lower levels of exposure, and epidemiologic studies of the effects of formaldehyde exposure among humans have given inconsistent results. Studies of industry workers with known exposure to formaldehyde report little evidence of increased cancer risk (37). It also appears that persons with asthma respond no differently from healthy individuals following exposure to concentrations of formaldehyde up to 3.0 ppm (38).
OSHA requires all workers to be protected from dangerous levels of vapors and dust. Formaldehyde vapor is the most likely air contaminant to exceed the regulatory threshold in the clinical laboratory (39, 40). Current OSHA regulations require vapor levels not to exceed 0.75 ppm (measured as a time-weighted average [TWA]) and 2.0 ppm (measured as a 15-min short-term exposure). OSHA requires monitoring for formaldehyde vapor wherever formaldehyde is used in the workplace. The laboratory must have evidence at the time of inspection that formaldehyde vapor levels have been measured, and both 8-h and 15-min exposure must have been determined.
If each measurement is below the permissible exposure limit and the 8-h measurement is below 0.5 ppm, no further monitoring is required as long as laboratory procedures remain constant. If the 0.5-ppm 8-h TWA or the 2.0-ppm 15-min level is exceeded, monitoring must be repeated semiannually. If either the 0.75-ppm 8-h TWA or the 2.0-ppm 15-min level is exceeded (unlikely in a clinical laboratory setting), employees must be required to wear respirators. Accidental skin contact with aqueous formaldehyde must be prevented by the use of proper clothing and equipment (gloves and laboratory coats).
The amendments of 1992 add medical removal protection provisions to supplement the existing medical surveillance requirements for employees suffering significant eye, nose, or throat irritation and for those experiencing dermal irritation or sensitization from occupational exposure to formaldehyde. In addition, these amendments establish specific hazard-labeling requirements for all forms of formaldehyde, including mixtures and solutions composed of at least 0.1% formaldehyde in excess of 0.1 ppm. Additional hazard labeling, including a warning label that formaldehyde presents a potential cancer hazard, is required where formaldehyde levels, under reasonably foreseeable conditions of use, may potentially exceed 0.5 ppm. The final amendments also provide for annual training of all employees exposed to formaldehyde at levels of 0.1 ppm or higher (41).
Note The use of monitoring badges may not be a sensitive enough method to correctly measure the 15-min exposure level. Contact the Occupational Health and Safety Office within your institution for monitoring options. Usually, the accepted method involves monitoring airflow in the specific area(s) within the laboratory where formaldehyde vapors are found.
The incidence and evidence of clinical latex sensitivity appear to be increasing since its first description in 1979. Since the introduction of standard precautions, the use of latex gloves by health care workers has increased dramatically (7). Those at risk appear to be health care workers and employees working in latex industries, patients with atopic diathesis, and patients who underwent repeated surgical procedures during childhood (42). The allergic response occurs to one or more natural rubber latex proteins, resulting in contact urticaria, angioedema, allergic rhinitis, asthma, or anaphylaxis. Early recognition of sensitization to latex is crucial to prevent the occurrence of life-threatening reactions in sensitized health care providers or patients (43). Latex allergy is now an important medical, occupational, medicolegal, and financial problem, and it is essential that policies be developed to reduce the problem (44–46). There also seems to be a relationship between allergies to natural latex rubber and allergies to avocados, chestnuts, and bananas. A high incidence of latex sensitivity has also been found in people with spina bifida (47).
The use of cornstarch powder in gloves can sensitize healthy people and exacerbate the symptoms of allergic patients. The powder spreads the latex allergens into the environment (42). Accompanying this increase in latex allergy is evidence of positive circulating specific immunoglobulin E antibodies to latex (48). Unfortunately, the primary treatment for latex allergy is avoidance (49).
The area of quality systems forms an integral part of any clinical laboratory operation. In many cases of clinical laboratory testing, various programs and guidelines for quality assurance procedures (including QC) have been thoroughly outlined. However, specific quality assurance recommendations within the parasitology section of microbiology have not been well defined in the past, and the information in this chapter should help clarify these recommendations. Although the diagnostic procedures in this area seldom yield numerical data, there are still a number of QC measures that can help to ensure accurate results.
The range of services provided will vary from one laboratory to another. To comply with the Health Care Financing Administration (HCFA) guidelines, only two extent classifications (rather than the previous four) are recognized in parasitology by the College of American Pathologists (50).
1. Extent 2. “Limited parasitology performed. The laboratory is able to recognize the presence of parasites,
