Manganese is an essential nutrient in our diet, and too much or too little both have adverse human health effects. There are newer studies that indicate elevated manganese levels can cause adverse human health effects, so EPA has included manganese in the testing required to determine if national regulation as a primary drinking water standard is needed.
This testing, called the Unregulated Contaminant Monitoring Rule #4 (UCMR4), is in its second of three years of national testing. All Iowa public water supply systems serving at least 10,000 people, and a selection of smaller systems, are required to monitor for the contaminants listed in the rule. Manganese is included and must be monitored in the finished drinking water. Once the data is collected and analyzed, EPA will determine whether to regulate any of the listed contaminants as a primary drinking water standard. The data for each specific system required to monitor under UCMR is included in that year’s Consumer Confidence Report, which is available to their customers by July 1st each year.
EPA has developed health advisories for manganese, which includes both acute (immediate) and non-acute (chronic) levels.
- For bottle-fed infants six months of age and younger, the acute level is 0.3 mg/L, while the acute level for the rest of the population is 1 mg/L, both of which are 10-day advisories. Typically, manganese concentrations in the groundwater are fairly constant, so there isn’t much variation over time.
- For the entire population, the lifetime health advisory is 0.3 mg/L.
Health advisories are not enforceable drinking water standards but public notice can be required when levels exceed the health advisory.
For more information on the UCMR, adverse health effects of manganese, and other information, please visit the DNR’s Drinking Water Health Advisories webpage, which includes links to DNR’s Frequently Asked Questions about Manganese in Drinking Water, DNR’s Manganese in Drinking Water Fact Sheet, and other reference material.
In Iowa, the groundwater aquifers are known to contain manganese, with those in the western half of the state testing at higher concentrations in the raw well water monitoring that has been done. Staff in the DNR’s water supply program have been working on developing a response to this emerging contaminant since the UCMR4 testing started, and have been presenting the issues during operator training events. While to-date there have been no samples over the 0.3 mg/L health advisory level in the UCMR4 testing in Iowa, there have been other samples from Iowa PWS that have had elevated manganese levels. Some of these have been in response to colored water complaint investigations. Prior to UCMR4, there has been no required certified lab testing for manganese in finished drinking water, and there is very little data available about Iowa’s systems.
To obtain more data and get an accurate picture of manganese levels in Iowa’s more than 1,800 public water supply systems, a sampling effort will soon begin. From July 1, 2019 – June 30, 2022, the DNR inspector will collect a water sample from each source/entry point at each public water supply system during the system’s next sanitary survey. he source/entry point is a point which is after any treatment and before entering the distribution system, and the sanitary survey is an on-site inspection of the public water supply system that happens at least every three years. For the smallest systems, where certain county sanitarians conduct an annual visit of those systems, the sampling project will start in July 2020.
The sample will be analyzed for manganese through a contract with the State Hygienic Laboratory. Depending upon the analytical result, the system may have no further action, may have additional samples required on a quarterly or annual basis, and, if the health advisory levels are exceeded, will be required to conduct public notification.
On a national basis, 22 states have had systems with manganese levels over 0.3 mg/L in the first 16 months of the UCMR4 testing.