New Hampshire has recently become the second state in the nation to lower the Maximum Contaminant Level (MCL) for arsenic in municipal water systems from 10 ppb (parts per billion) to 5 ppb. However, in New Hampshire around 40% of the population does not rely on municipal water systems. Being a rural state, many New Hampshire residents have a private well water as their main drinking water source. These wells do not undergo regular testing like municipal water systems and levels of arsenic can be significantly higher than 5 ppb. The levels of arsenic in private wells throughout New Hampshire, Vermont and Maine can vary greatly and are dependent on the geology of the area and the amount of arsenic in bedrock. It is up to the homeowner to test their own well water. Learn more about how to get your well water tested in New Hampshire.