What is the MCL for Arsenic in mg/l?

• A. 0.1 mg/L
• B. 0.05 mg/L
• C. 0.01 mg/L
• D. 0.001 mg/L

Answer: (C)

The key idea is the enforceable limit set for drinking water, known as the maximum contaminant level (MCL). For arsenic, the current MCL is 0.01 mg/L, which equals 10 µg/L (or 10 parts per billion). This value was adopted to lower cancer risk from arsenic exposure; it is the regulatory standard today, replacing the older, higher limit. So the correct choice is 0.01 mg/L.