Endotoxin inactivation by selected drinking water treatment oxidants

Exposure to endotoxins in treated drinking water can occur through ingestion, dermal abrasions, inhalation of water vapor, intravenous injection or during dialysis. While the risks associated with endotoxin ingestion and entry through dermal abrasions are not well quantified, adverse effects of intravenous injection and dialysis are well known and some studies indicate that inhalation of moisture-laden air may impact human health. This study quantifies the inactivation of endotoxin derived from Escherichia coli O55:B5 by three substances used either as disinfectants or oxidants in drinking water treatment: chlorine, monochloramine and potassium permanganate. Inactivation rates were found to be 1.4, 1.0 and 0.7 endotoxin units (EU)/mL h, for free chlorine, potassium permanganate and monochloramine, respectively. These rates are relatively slow given that contact times in drinking water distribution systems are typically less than 48 h. While small amounts of endotoxin may be removed by oxidation the observed removals are much less than those provided by physical removal processes. The significance of this finding is important for dialysis considerations but is as yet unclear with regard to inhalation, as the risk of inhaling sufficient quantities of endotoxin-containing aerosolized water droplets to adversely affect human health has not yet been adequately quantified.