Arsenic (As) is a semi-metal element of periodic table that can be found in drinking water. Arsenic is not easily dissolved in water, therefore, if it is found in a water supply, it usually comes from mining or metallurgical operations or from runoff from agricultural areas where materials containing arsenic were used. Arsenic in water has no color, taste or odor, and can be only detected via arsenic-specific water tests.

When digested with water in dangerous concentration, several conditions, including poisoning and cancer, may occur. EPA, Environmental Protection Agency has set the arsenic standard for drinking water at 0.10 parts per million , 0.01 mg/l or 10 parts per billion to protect consumers from the effects of short-term, and long-term chronic exposure to arsenic.