Despite what many websites out there may say, the answer is “no”. Being a “basic” material, this means that it cannot be broken down any further and will not leach anything into the water. Raw, untreated alumina will always give up some aluminum to the tune of maybe 0.1 ppb (the city actually adds more than this in treatment). But the preconditioning that takes place during manufacturing will prevent this from happening when put into actual use. Sometimes there are trace amounts of iron, sodium, silica that can come off alumina initially. But with a good flush of 15 minutes or so (for an under sink system) and a couple of days of use this would be removed. (Initially the effluent levels of these elements are in the low digit ppb levels). If the pH is really low, say 6.3 or so, then there may be some aluminum released to the tune of 50 ppb (Ontario Drinking Water Standard is 0.1 mg/L so this is 1/2 the standard). That said, he said that on any municipal supply this release would not take place.