What unit is used to report arsenic concentration in drinking water standards?

What unit is used to report arsenic concentration in drinking water standards?

• A. Milligrams per liter
• B. Micrograms per liter
• C. Parts per million
• D. Parts per billion

Answer: (B)

Arsenic in drinking water is a trace-level contaminant, so the reporting unit is a very small one. Micrograms per liter is used because it aligns with the actual regulatory limits, which are in the tens of micrograms per liter. In water, 1 milligram per liter is the same as 1 part per million, and 1 microgram per liter equals 1 part per billion. So saying arsenic is measured in micrograms per liter communicates the right scale for drinking-water standards (for example, the standard is around 10 µg/L). While parts per billion conveys the same magnitude, the conventional reporting unit for these standards is micrograms per liter.

Arsenic in drinking water is a trace-level contaminant, so the reporting unit is a very small one. Micrograms per liter is used because it aligns with the actual regulatory limits, which are in the tens of micrograms per liter. In water, 1 milligram per liter is the same as 1 part per million, and 1 microgram per liter equals 1 part per billion. So saying arsenic is measured in micrograms per liter communicates the right scale for drinking-water standards (for example, the standard is around 10 µg/L). While parts per billion conveys the same magnitude, the conventional reporting unit for these standards is micrograms per liter.