Community Water Systems

The annual mean (average) and maximum concentrations of arsenic, nitrate, radium, uranium and disinfection byproducts (DBPs) for community water systems in Minnesota.

If the concentrations of arsenic, nitrates, radium, uranium and DBPs are increasing or decreasing over time.

• The data provides summary information on arsenic, nitrate, radium, uranium and disinfection byproduct concentrations in drinking water from community water systems in Minnesota.

• State and local partners can use the data for program planning and evaluation.

• The origins of entry for contaminants in drinking water.

• The levels of arsenic, nitrate, radium, uranium and DBPs, in individual community water systems.

• Information about water quality in water sources other than community water systems

These are the contaminants that the Center for Disease Control's National Environmental Public Health Tracking Network selected because they appear more often in drinking water at levels that may be of public health significance.

The MN Environmental Public Health Tracking Program is working together with the MDH Drinking Water Protection Program to develop additional data and measures of interest in Minnesota and nationally.

• Sample results with concentrations less than the detection limit have been replaced with a value equal to 1/2 the detection limit for the analytical method used.

• No sensitivity analyses were conducted to characterize how the approaches to handling non-detects may impact the drinking water quality data; therefore, it is possible that the analysis may produce biased estimates of the mean - especially if a large proportion of samples are below the limit of detection for the analytical method.

• These data are limited to community water systems in Minnesota (i.e., systems that serve 15 or more locations or 25 or more people, year-round in Minnesota).

• Concentrations in drinking water systems cannot be directly linked to exposures and health risks, because they do not account for water use and consumption practices. In addition, people may obtain drinking water from sources other than community water systems (e.g., private wells, bottled water, workplace, school). Concentrations may not reflect levels in finished drinking water or water at the consumer's tap.

• The current form of the data and measures contain one record for each active community water system per year (i.e., active at the time of data analysis). Sampling results from inactive systems that were active prior to data analysis are not included in the data and measures. Early missing values may be because the water system was not yet active, or the system was not required to take a compliance sample during that particular time period. The data set does not distinguish between these two scenarios.

• Trends can be difficult to interpret if water quality standards and treatment requirements change over time.

• Presenting average concentrations by calendar year is not usually consistent with how maximum contaminant levels (MCLs) established by US Environmental Protection Agency (EPA) are calculated (i.e., typically based on running averages).

• The accuracy of the population served information is unknown. Water systems derive population estimates using census estimates, number of water connections, or other means. Furthermore, system population is a current estimate, so population-based estimates for past years may be inaccurate (likely over-estimated). Historical information on population served is not available.

• Systems may receive a sampling waiver from the state for reduced frequency of monitoring based on low analytical results. Reduced monitoring frequencies lead to a reduced number of samples. If a system was not required to sample within a calendar year, the most recent available sampling result was carried forward.

• For more information about data and measures, or to obtain earlier data records contact the MN Data Access Portal.

• For more information about regulatory and monitoring requirements related to Community Water Systems, contact the MDH Drinking Water Protection Program.