DescriptionArsenic, a known human carcinogen, is naturally occurring in groundwater in New Jersey and many other states and countries. Many municipalities in the Piedmont, Highlands, and Valley and Ridge Physiographic Provinces have a high proportion of wells that exceed the New Jersey maximum contaminant level (MCL) of 5 µg/L. Hopewell Township, located in Mercer County and the Piedmont Province, has a progressive local ordinance which requires the installation of dual tank, point-of-entry treatment (POET) systems on affected wells and provided a unique study opportunity. The purpose of this research was to determine the efficacy of existing arsenic treatment systems, if they are maintained, the behaviors and beliefs of homeowners and the risk reduction provided by treatment systems. A total of 65 homes were recruited into the study. Of the homes with dual tank POET, 92.7% of homes, regardless of age and maintenance schedule adherence, had arsenic levels under the MCL at the kitchen sink. Maintainers, homeowners who test their water yearly and replace their arsenic tanks when needed, were found to be the group with the lowest risk of arsenic exposure. This study appears to be the first to identify a potential health hazard as water treatment media was found to escape many of the systems and enter the water supply potentially leading to acute doses of arsenic through ingestion. A potential solution of adding a post-treatment sediment filter is proposed to remedy this problem. Based on the average concentrations of arsenic at the kitchen sink, average water consumption and the Township population, Hopewell’s arsenic water treatment ordinance, requiring POET dual tank arsenic treatment reduced the incidence of excess lifetime (70-year) bladder and lung cancers from 121 (1.7 cancer cases/year) to 16 (0.2 cancer cases/year) preventing 105 lifetime cancer cases (1.5 cases/year). Because the high risk of cancer from arsenic can be mitigated with effective arsenic water treatment systems, this ordinance should be considered a model for other municipalities. An effort should also be made to increase the number of homeowners who test yearly and maintain their treatment systems.