Cytotoxicity of liquid disinfectants

This study was prompted by toxic responses to disinfecting agents reported in patients after surgical procedures and in sensitized health care personnel. We evaluated the cytotoxicity of seven substances used in the formulation of common liquid chemical disinfectants and sterilants. We found that a standard method based on direct microscopic examination of cell cultures was insensitive and may result in an underestimation of the risk that disinfectants pose to health care personnel or patients who are exposed to these substances. Using independent quantitative tests measuring the integrity of the cellular membrane, metabolic activity, or cell growth, we found that there is a several-hundredfold difference in the relative toxicity of various disinfecting substances. The concentration toxic in 50% of the cell population (TC(50)) that was found for each disinfectant was similar in a variety of cell lines from human, monkey, or mouse origin. Statistical analysis of TC(50)s suggests that liquid disinfecting agents could be classified in three main groups according to their relative toxicity, with: (1) mild (TC(50) > 1 mM, including phenol, hydrogen peroxide, and formaldehyde); (2) moderate (1mM > TC(50) > 0.1 mM, sodium hypochlorite); and (3) severe (TC(50) < 0.1 mM, glutaraldehyde, cupric ascorbate, and peracetic acid) toxicity. These data suggest a vast difference in the potential risk of various disinfectants and sterilants. The data presented in this study should help to define the relative toxic risk of different disinfecting substances to patients and health care personnel and assist in the selection of safer microbicidal formulations.