Arsenic occurs naturally in the ground, as part of soil and rocks. When it is in water, arsenic cannot be seen or tasted. It also has no aroma.
Some arsenic is always present in water.
This level is also accepted by many countries, including the United States and most European nations. It revised this Guideline Value to 10 ppb in 1993. They are intended for use as a basis for the development of national standards in the context of local or national environmental, social, economic, and cultural conditions. Water can be tested by trained personnel to determine if it contains more than an acceptable level of arsenic. Measuring arsenic is a complex process that requires specialized equipment under controlled conditions.