Trace amounts of arsenic found in some tap water could add up to problems later on. Certain parts of the United States, Canada, and UK have traces of arsenic within their tap water. According to the World Health Organization, drinking arsenic-rich water over a long period of time can lead to skin problems and possible cancers of the skin, kidney, lung, and bladder. Invest in a water purifier and have your tap water checked for additional safety. For more on this topic, click here:: Arsenic Poisoning in Drinking Water: Huge Public Health Problem