Chlorine reacting with urea in urine and other nitrogen-containing wastes from bathers can produce chloramines. Chlorine and chloramines can both be removed by activated carbon filters and other methods. Chlorinated amino acids rapidly decompose, but protein chloramines are longer-lived and retain some oxidative capacity. Aging may take weeks to remove chloramines, whereas chlorine disappears in a few days. Metallic iron is shown to reduce inorganic and organic chloramines effectively. Two classes of compounds are considered, inorganic chloramines and organic chloramines. This is often done through the addition of chloramines, discussed above as a primary disinfectant. It also burns off chloramines in the same manner as traditional shock (oxidizer). Such species are generated by treatment of osmium tetroxide with the sodium chloramines. A variety of organic chloramines are useful in organic synthesis. Medium pressure UV technology is used to control the level of chloramines in indoor pools. Since the 1980s, most dialysis machines are built with filters to remove chloramines. A perfectly maintained consecutive dilution system drastically reduces the build-up of chloramines and other DBP's. Chloramines are responsible for the distinctive "chlorine" smell of swimming pools. Chloramines pose a threat to aquatic ecosystems that are exposed to discharges of treated wastewater.