Arsenic is a highly poisonous metallic element.It has three allotropic forms , yellow, black and gray.
It can not be removed by boiling the water. Because Arsenic does not melt. It sublimes at 616 c.Which means that it transforms directly from a solid to a vapour by passing a liquid state.
There for a special kind of media is used to remove Arsenic from drinking water.
It does not effect the health immediately.A regular use of Arsenic effected water can cause different kind of health problems like bladder, lung, and skin cancer and may cause kidney and liver problems.