Epidermal Hyperplasia in Mouse Skin Following Treatment with Alternative Drinking Water Disinfectants

• Published in: Environmental health perspectives Vol. 69; pp. 293 - 300
• Main Authors: Robinson, Merrel, Bull, Richard J., Schamer, Marlene, Long, Richard E.
• Format: Journal Article
• Language: English
• Published: United States National Institute of Environmental Health Sciences. National Institutes of Health. Department of Health, Education and Welfare 01.11.1986
• Subjects: Animals; Antiseptics; Chloramines - toxicity; Chlorine; Chlorine - toxicity; Chlorine Compounds; Disinfectants - toxicity; Disinfection - methods; Dosage; Epidermis; Eyepieces; Female; Hyperplasia; Hypochlorous Acid - toxicity; Mice; Oxides - toxicity; Poster Session; Potable water; Skin; Skin - drug effects; Skin - pathology; Sodium Hypochlorite - toxicity; Tumors; Water Supply - analysis
• ISSN: 0091-6765; 1552-9924
• DOI: 10.1289/ehp.8669293

Female SENCAR mice were treated with aqueous solutions of hypochlorous acid (HOCl), sodium hypochlorite (NaOCl), chlorine dioxide ( ClO2), and monochloramine ( NH2Cl) by whole body exposure (except head) for a 10-min period for 4 days in the first experiment and for 1 day (except NH2Cl) in the second experiment. Animals were sacrificed the day following the last treatment (experiment 1) or on day 1, 2, 3, 4, 5, 8, 10, and 12 following treatment (experiment 2), and skin thickness was measured by light microscopy at ×400 by use of an eyepiece micrometer. Concentrations of disinfectants were 1, 10, 100, 300, and 1000 mg/L, for experiment 1 and 1000 mg/L for experiment 2. Thickness of the interfollicular epidermis (IFE) for control animals was 15.4 ± 1.5 μm. After 4 days of treatment at 1000 mg/L, HOCl and ClO2increased thickness to 39 ± 7.0 and 40.2 ± 11.8, and NaOCl increased thickness to 25.2 ± 6.1 μm. Only HOCl and ClO2were tested at 300 mg/L, yielding an IFE thickness of 30.0 ± 13.1 and 16.8 ± 0.8 μm, respectively. The response to HOCl was found to be dose-related; the minimally effective dose was 100 mg/L. In earlier, preliminary tests to determine optimum treatment schedule, the response to HOCl appeared to be maximal after 4 days of treatment and tended to decrease with further treatment. The time-course study following a single treatment of 1000 mg/L HOCl, however, showed a progression of IFE thickening of from 18.3 ± 1.4 at 1 day to 30.8 ± 8.0 at 8 days, decreasing to 19.1 ± 6.2 μm at 12 days. ClO2and NaOCl when tested in this manner did not produce increased thickness of IFE with time, but rather gave a persistent level of increase that remained for the 12 days. NH2Cl reduced skin thickness to 13.6 ± 6.1 μm. Examination of sections of skin treated with HOCl and ClO2indicated an increase in cell numbers. HOCl and ClO2are therefore capable of inducing hyperplastic responses in the mouse skin. The basis for the decrease in skin thickness resulting from NH2Cl treatment remains to be established.