WQRF Contaminant Occurrence Map

Data Looks at 57 Different Contaminants

Watch this video for a quick overview of how the map can be used.

The new Contaminant Occurrence Map displays data in the United States for regulated drinking water contaminants that have an enforceable level (MCL or Action Level) above the health-based goal level (MCLG) and also aesthetic contaminants that can cause taste, odor and color or staining issues.

• ​The Contaminant Occurrence data collection effort gathered water quality data over the last 10 years for 57 different drinking water analytes in the United States. 
• The mapping tool provides a visual illustration of this occurrence data provided by the States and through US EPA UCMR4. 
• Occurrence data below the MCL or Action Level is compliant with the Safe Drinking Water Act standards. 
• This map shows statistical summaries of all data, not regulatory compliance. 
• See key terms below for more information.​

CLICK HERE TO ACCESS THE MAP

The data collected for this map was pulled from 46 state regulatory agencies, the United States Environmental Protection Agency’s (USEPA) Fourth Unregulated Contaminant Monitoring Rule (UCMR4), and the federal Safe Drinking Water Information System (SDWIS).

KEY TERMS:

• Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals. 
• Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.
• Maximum Residual Disinfectant Level Goal (MRDLG) - The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants. 
• Treatment Technique (ITT) - A required process intended to reduce the level of a contaminant in drinking water. 
  • ​Lead and copper are regulated by a treatment technique that requires systems to control the corrosiveness of their water. If more than 10% of tap water samples exceed the action level, water systems must take additional steps. For copper, the action level is 1.3 mg/L, and for lead is 0.015 mg/L.

• Maximum Residual Disinfectant Level (MRDL) - The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants. 
• Non-detect (ND) Data - This means the concentration was lower than the analytical instrument's detection limit and are treated as a result of zero.
• Community Water System (CWS) - This supplies water to the same population year-round. It serves at least 25 people at their primary residences or at least 15 residences that are primary residences (for example, municipalities, mobile home park, sub-divisions).
• Transient Non-community Water Systems (TNCWS) - These provide water to 25 or more people for at least 60 days/year, but not to the same people and not on a regular basis (for example, gas stations, campgrounds). 
• Non-transient Non-community Water Systems (NTNCWS) - These regularly supply water to at least 25 of the same people at least six months per year, but not year-round (for example, schools, factories, office buildings, and hospitals which have their own water systems). 

Find more resources for water quality testing and treatment at www.WQA.org