MassDEP considers 1,4-dioxane an emerging contaminant because it is toxic, widely used so that pathways for human exposure exist, and health protection standards are needed. 1,4-dioxane is a synthetic chemical with many uses as a solvent. It is used as a stabilizer for chlorinated solvents used in degreasing operations and is present in many products (e.g., paint, varnish remover, antifreeze, airplane deicing solutions and an impurity in many personal care products, etc). Based on toxicity studies, EPA has categorized 1,4-dioxane as likely to be carcinogenic to humans. It is also to undergo Tier 1 screening as an endocrine disruptor under the EPA Endocrine Disruptor Screening Program. In addition, growing evidence exists that 1,4-dioxane may be more prevalent in groundwater throughout the United States than previously realized, potentially due to releases from hazardous waste sites and landfills. Enhanced monitoring efforts for 1,4-dioxane are underway. For example, the EPA has listed 1,4-dioxane under the Unregulated Contaminant Monitoring Rule 3 (UCMR3) in order to collect information on the frequency and levels of 1,4-dioxane in public drinking water supplies across the United States, including those in Massachusetts. Based on these findings and other determinants, EPA will determine if a national drinking water standard, or Maximum Contaminant Level (MCL), for 1,4-dioxane should be set to protect public health.  

MassDEP Workplan:  

  • MassDEP recently set groundwater and soil cleanup standards for 1,4-dioxane in its hazardous waste site cleanup program (M.G.L. Chapter 21E). These were promulgated in April 2014. See: 310 CMR 40.0000 - Massachusetts Contingency Plan (MCP)  pdf format of 310 CMR 40.0000 - Massachusetts Contingency Plan (MCP)
file size 3MB doc format of                             310 CMR 40.0000 - Massachusetts Contingency Plan (MCP)                file size 3MB and MCP Numerical Standards .
  • The agency will include 1,4-dioxane in upcoming revisions to its Laboratory Certification regulations.
  • MassDEP also has updated its drinking water guideline for 1,4-dioxane. See: Current Regulatory Limit: 1,4-Dioxane
  • The agency will obtain data about the presence of 1,4-dioxane in Massachusetts public water supplies due to EPA’s Unregulated Contaminant Monitoring Rule 3 (UCMR3) for nationwide testing of public drinking water supplies (2013 to 2015). MassDEP will respond to any cases in which standards and guidelines for 1,4-dioxane are exceeded.

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