1. a) Estimate the risk-based screening level (RBSL) of arsenic in a drinking water supply in a residential neighborhood (assume an exposure duration of 40 years). Assume a target risk level of 10^-5. The cancer slope factor for arsenic is 1.5 (mg/kg-day)^-1. State all relevant assumptions clearly.

2. If the concentration of arsenic in the drinking water supply was 500 g/L, how much treatment (report as a percentage) is required to achieve the target risk level (10^-5).
3. What are two strategies and/or treatment methodologies to reduce the risks associated with arsenic contamination of drinking water?