『Abstract
　The processes impacting arsenic toxicity are a function of molecular speciation, where risk from chronic exposure to the reduced arsenic species is estimated to be four orders of magnitude higher than many oxidized arsenic species. While the adverse health effects of arsenic are generally well known, the impact of speciation on carcinogenic and noncarcinogenic adverse health effects has rarely, if ever, been considered in traditional chronic arsenic exposure risk assessments. Utilizing standard Environmental Protection Agency protocol, lifetime cancer risk and hazard quotient are calculated for chronic arsenic exposure at the local, regional, and national scale to characterize potential risk as a function of arsenic speciation. Additionally, the antagonistic and synergistic impacts of biogeochemical processes on arsenic bioavailability and bioaccessibility are discussed and show chronic exposure risk is likely to be reduced below some maximum value calculated foe reduced arsenic species.

Keywords: Arsenic; Speciation; Risk assessment』

1. Introduction
2. Materials and methods
　2.1. Development of the chronic exposure risk charts
　2.2. Calculation of chronic exposure risk
3. Results and discussion
　3.1. Description of the chronic exposure risk charts
　3.2. Arsenic speciation in the environment
　3.3. Application of the chronic exposure risk charts
　　3.3.1. National assessment: Groundwater
　　3.3.2. Regional assessment: Surface water
　　3.3.3. Local assessment
　3.4. The role of bioavailability and bioaccessibility
　3.5. Assessment of the chronic exposure risk chart and potential limitations
4. Implications
Disclaimer
References