The Wells and Increased Infant Sensitivity and Exposure (WIISE) Study was a pilot project with the Minnesota Department of Health to evaluate private well users’ exposure to manganese and other contaminants of concern for children’s health. Dakota County staff collected untreated water samples from outside faucets at the homes of 274 private well owners in Inver Grove Heights to test for manganese, nitrate, nitrite, chloride, sulfate, fluoride, lead and coliform bacteria. Read theWells and Increased Infant Sensitivity and Exposure Study or the Summary Fact Sheet.
Recommendations for well owners
Summary of findings
Of the 274 water samples collected, 194 (71 percent) exceeded the Minnesota Department of Health’s drinking water guidance for manganese of 100ug/L for infants 12 months and younger. And, 153 of the samples (56 percent) exceeded the Minnesota Department of Health’s drinking water guidance for manganese of 300 ug/L for everyone older than 12 months.
Study participants whose result exceeded 100ug/L for manganese were asked to submit a sample of their drinking water from their primary drinking water faucet. Of the 109 drinking water samples submitted, 39 (36 percent) exceeded the drinking water guidance for manganese of 100 ug/L. Water softeners were shown to be effective at reducing the manganese concentration to below 100 ug/L. All of the water samples that were treated by a reverse osmosis (RO) system were also softened, so the effectiveness of a reverse osmosis system could not be evaluated. Carbon, iron and sediment filters did not consistently reduce manganese.
Infants younger than 12 months of age that consume water with too much manganese may develop learning and behavior problems. Children older than 12 months and adults that consume water with high levels of manganese for a long time may have problems with memory, attention and motor skills.
Three of 274 outside spigot samples (1 percent) exceeded the health-based guidance value of 10 ug/L for arsenic; 155 of 274 (57 percent) had arsenic detected in outside spigot; 19 of 29 samples (66 percent) had arsenic detected in the sample collected by the well owner of the primary drinking water faucet. The Minnesota Department of health does not consider the guidance value of 10 ug/L low enough to eliminate all risk of cancer and other health effects from arsenic.
Lead was detected in 144 of 273 outside spigot samples (53 percent) and in 9 of 35 samples (26 percent) collected by the well owner at their primary drinking water faucet. Minnesota Department of Health states there is no amount of lead that is safe to consume.
All of the fluoride results were less than the recommended fluoride levels of 0.7 mg/L for good oral health. Parents of children in homes with fluoride levels below 0.7 mg/L should discuss the need for fluoride supplements with their child’s dentist or health care provider.
Coliform bacteria was present in 67 of 270 water samples (25 percent). One well tested positive for E. coli. Bacteria detected in a well sample can be an indication that surface contamination is reaching the water in the well.
No wells had nitrate above the drinking water guidance of 10 mg/L, and only six wells had nitrate above background levels of 3 mg/L.
No nitrite was detected, and sulfate was at levels significantly lower than the drinking water guidance.
Water treatment options
Many home water treatment options are available. Continue to test your drinking water even after you install a treatment unit. All home water treatment units require regular maintenance.
Dakota County recommends that a private well be sampled at least one time for manganese and arsenic. And, water from the primary drinking water faucet should be tested for lead each time the plumbing associated with the primary faucet is changed. Minnesota Department of Health recommends private wells be tested annually for coliform bacteria and every two to three years for nitrate, more frequently if nitrate has been detected in previous samples. Treated water should be sampled to confirm that the treatment device is reducing contaminants of concern. Request a water test kit.