Incorrect. Free chlorine (HOCl) and monochloramine (NH2Cl) (the predominant chloramine in municipal water supplies) are both small molecules (52 and 51 daltons, respectively) that are comparable in size to urea (60 daltons). Both easily cross dialyzer membranes by diffusion.

Incorrect. Historically, free chlorine was added to municipal water supplies to suppress bacterial growth. Free chlorine reacts with natural organic compounds in the water to form trihalomethanes (THMs), which are carcinogenic. The Environmental Protection Agency placed a limit on the concentration of THMs in drinking water. To comply with this limit, alternative methods of disinfection have been introduced. The use of chloramine, which does not form THMs, is becoming an increasingly common alternative to the use of free chlorine.

Correct. Monochloramine is a strong oxidant that oxidizes the iron of hemoglobin to form methemoglobin. The methemoglobin precipitates to form Heinz bodies in the red cells, which are then destroyed in the spleen. Chloramines also inhibit the activity of the red cell hexose monophosphate shunt and oxidize lipids in the red cell membrane, making the cells more fragile. These processes lead to a reduction in red cell half-life, which was manifest as a hemolytic anemia in early reports (Kjellstrand et al) , but which may now present as an apparent resistance to erythropoietin (Fluck et al).

Incorrect. Monochloramine, even at very low concentrations is toxic to red blood cells. The maximum level of chloramines permitted in water used to prepare dialysate is 0.1 mg/L (ANSI/AAMI RD62:2001, Water treatment equipment for hemodialysis applications. Association for the Advancement of Medical Instrumentation, Arlington, VA 2001).

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