MDH review prompts changes to water sampling procedures


A Minnesota Department of Health (MDH) internal review has found inconsistent — and in some cases inadequate — procedures associated with the handling of some drinking water samples by its Environmental Health Division. Based on this finding, MDH has moved to immediately strengthen and standardize the procedures, and to conduct additional testing as needed to ensure accurate water quality assessments.

According to Minnesota Health Commissioner Dr. Ed Ehlinger, the inconsistent handling practices are unlikely to constitute a significant threat to public health but it is important to address the problem immediately and verify data through retesting where needed.

“While the situation as a whole would not suggest an increased risk for most communities, we want to ensure we have the highest level of reliability in our data on drinking water quality,” Commissioner Ehlinger said. “This inconsistency is unacceptable and should not have happened. We’re moving swiftly to correct it.”

MDH conducts routine water sampling of public drinking water systems around the state. The concern involves the holding temperature of water samples taken to determine the presence of organic chemicals, such as fertilizers, solvents and common household chemicals. The issue also potentially involves samples taken to determine the presence of inorganic compounds for which holding temperature may be an issue — specifically, cyanide and nitrite (a substance related to but not identical to nitrate). It does not involve samples taken to analyze for the presence of viruses or other infectious agents, fluoride, radionuclides, arsenic, lead, mercury or other heavy metals.

In 2015, MDH tested around 2,800 drinking water samples for organic chemicals. This work represented about 30 percent of the total water samples collected and analyzed that year, although the numbers may vary from year to year. While current federal guidelines for monitoring of various compounds including organic chemicals require water samples to be kept at or near four degrees Celsius during transport from the collection site to the laboratory, in some cases samples were transported at room temperature. This may have caused some samples to degrade and provide results lower than the true value. In most cases, the data were unlikely to have been off by a large margin, but the inconsistent practices introduced an unacceptable level of uncertainty to the data.

The MDH response plan for this issue includes the following elements:

  • Immediate communication and training for staff to ensure all water samples are kept at proper temperature during transport from collection site to laboratory;
  • Evaluation of past monitoring results to determine which results complied with the temperature requirements;
  • Prioritized retesting of water systems based on factors including past monitoring results; and
  • A broad, independent review of water sample handling procedures and practices of the department.

According to MDH Environmental Health Division Director Tom Hogan, the review that brought this issue to light indicates these inconsistent practices may have been in place since the early 1990s, at which point it seems updated guidance from the U.S. Environmental Protection Agency (EPA) was inconsistently implemented by the program.

“These practices should have been uniformly modified to comply with up-to-date EPA guidelines, and the division did not do so,” Hogan said. “We take our responsibilities in this area very seriously, and we deeply regret this oversight. We are taking immediate steps to set this right.”

Hogan noted that other state agencies have data regarding compounds in public waters, and these data indicate the risk to Minnesotans is limited.

“Even though that evidence would suggest the risk to communities is low, recent events like the case in Flint, Michigan, show the special expectations that exist around drinking water safety,” Hogan said. “That’s why we are going to immediately resample systems determined to have the greatest potential to be affected by the temperature inconsistencies. We will prioritize this work based on potential risk factors and will be working with laboratories to analyze the samples as quickly as possible.”


This information was provided by the Minnesota Department of Health (MDH). For more information, go to