It is very difficult to reverse the effects of water pollution. Natural processes that cleanse the water can take years, decades, or even centuries, and even with costly technological processes, it can take years to remove all of the harmful substances from the water.
While there have been improvements to mining practices in recent years, significant environmental risks remain. Negative impacts can vary from the sedimentation caused by poorly built roads during exploration through to the sediment, and disturbance of water during mine construction. Water pollution from mine waste rock and tailings may need to be managed for decades, if not centuries, after closure.
POPs are a group of man-made substances, most of which share characteristics like low water solubility (they do not easily dissolve in water), the ability to accumulate in fat (high lipophilicity), and resistance to biodegradation (they take a very long time to break down and stop being harmful). The name POPs refers to many pollutants such as pesticides like DDT and pollutants like PCBs. These chemicals come from pesticides, industrial chemicals, and are the unwanted by-products of industrial processes or combustion.