In addition to the naturally occurring minerals present in local surface water or groundwater supplies, all municipalities add chlorine and/or chloramines and fluoride for the purposes of human health. Water from well or spring sources are often high in minerals such as sodium, calcium, magnesium, sulfur, iron, and manganese. Although city water treated by municipalities must meet the minimum EPA standards, well water is not regulated and can also contain harmful contaminants like chromium, arsenic, or bacteria. While city or well water may meet drinking water standards, it may not be ideal for plants or hydroponics.