To the Editor.—
Examination of the nail-fold capillaries may provide useful diagnostic information in a variety of rheumatic disorders. The capillaries are best seen when a clear viscous liquid is applied to the skin surface, and microscope immersion oil is commonly used for this purpose.1In 1973, Bennett and Albro2 reported that immersion oils used at that time contained 30% to 40% polychlorinated biphenyls (PCBs). In response to increasing concerns about environmental pollution with PCBs and adverse health effects of these compounds, manufacturers began to produce PCG-free immersion oil. Yet, it was not until 1976 that one major supplier of microscope immersion oil finally removed PCBs from its product.A large body of medical literature suggests that PCBs or associated contaminants are potentially injurious to humans, even at low concentrations.3 In the rat, microscope immersion oil containing PCBs, when applied to the skin in small quantities daily
Nashel DJ, Fischmann AB. Polychlorinated Biphenyls in Microscope Immersion Oil. JAMA. 1983;249(13):1706. doi:10.1001/jama.1983.03330370020007
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