In 2003, the USEPA revised the drinking water standard for arsenic from which range to which range?

• A. 10 micrograms/L to 1 micrograms/L
• B. 25 micrograms/L to 5 micrograms/L
• C. 50 micrograms/L to 10 micrograms/L
• D. 100 micrograms/L to 25 micrograms/L

Answer: (C)

Lowering exposure to a known cancer-causing contaminant in drinking water is the focus. In 2003, the USEPA tightened the arsenic limit by cutting the allowable concentration from fifty micrograms per liter to ten micrograms per liter. This change came after risk assessments showed greater cancer and other health risks at higher levels, so the standard was made more protective to safeguard public health. Water systems must treat or blend water to meet the ten microgram per liter limit, with compliance timelines implemented accordingly. The other ranges listed don’t reflect what the regulatory change actually was, which was a substantial reduction from fifty to ten.