The drum, having already been partially discharged during detack, is further discharged by light. Any remaining toner, that did not transfer in step 6, is removed from the drum surface by a rotating brush under suction, or a squeegee known as the cleaning blade. This 'waste' toner usually is routed into a waste toner compartment for later disposal; however, in some systems, it is routed back into the developer unit for reuse. This process, known as toner reclaim, is much more economical, but can possibly lead to a reduced overall toner efficiency through a process known as 'toner polluting' whereby concentration levels of toner/developer having poor electrostatic properties are permitted to build up in the developer unit, reducing the overall efficiency of the toner in the system.