What Cancels Hand Washing

Question
Before I leave work to daven Mincha I first do netillath yadayim with a bracha. On my way to the shul I take a short-cut which involves my leaning with my hands on an outside concrete surface. Does touching that surface mean that the netillah which I did is not valid?

Answer
So long as any dust which goes on your hands is easily removable without the need to wash them then the netillah which was done is is still effective. One should simply wipe off whatever dust may be on one’s hands and continue onwards towards davening.