Scientists confirmed more drinking water wells in the lakes area contain levels of arsenic exceeding federal health limits.
An updated map released in early June by AW Research Labs in Brainerd reveals wells on Round Lake, North Long Lake, Pelican Lake and Campbell Lake contain arsenic in excess of 10 parts per billion (ppb). Approximately 27 samples fell between 10 ppb and 50 ppb out of 83 tested, according to laboratory director Sara Ahlers.
The highest rates among the samples - 39 ppb and 30 ppb - both came from Merrifield, which is known as an area that seems to have higher rates of contamination. Ahlers said she is working to confirm another sample that tested at 50 ppb.
She said the lab is also currently testing another 25 samples turned in by residents in the Pelican Lakes area following a recent gathering of the Pelican Lakes Conservation Club.
In January, the lab found contamination in six out of 11 samples near Round and North Long lakes on Ojibwa Road north of Brainerd.
Arsenic is odorless, tasteless and is known to be harmful to human health, depending on the chemical form, dosage and length of exposure.
"We're seeing a lot of arsenic in certain areas," Ahlers said. "We were a little surprised that there was a bunch up in Pelican as well."
But not too surprised, she said, as officials have long known of the presence of arsenic in the state. The most recent data indicates the contamination rate is higher than previously thought, however. The Minnesota Department of Health (MDH) reports 10 percent of all new wells in Minnesota exceed the federal arsenic standard.
Testing of municipal water sources is mandated, but existing private wells are tested only at homeowner expense. Recent state regulations require testing of all new wells installed since August 2008.
According to data compiled by MDH, a total of 1,371 new wells in Crow Wing County were tested for arsenic from August 2008 through July 2013. Of these wells, 46, or 3.4 percent, contained arsenic at levels exceeding 10 ppb. In Cass County, 56 of 1,313 wells tested above 10 ppb, or 4.3 percent. Both counties fell well below the state average; these figures, however, do not account for wells that existed prior to data collection. The counties with the highest contamination levels, above 20 percent, are in western and south central Minnesota.
Ed Schneider, a spokesperson for the MDH, said the agency began requiring well construction records be submitted in 1974, but records are spotty until the mid-1980s. The total number of wells that reportedly exist in Crow Wing and Cass counties are 20,399 and 14,805, respectively.
This could mean another 1,200 wells in both counties are affected by contamination, but the number is likely higher given the lack of regulation on older wells and incomplete data.
Schneider said it is difficult to estimate the total number of wells, but a "rough guess" would be that two to three times as many exist than are reported. The average lifespan of a well, he said, is 30-50 years, so it is likely that some of the oldest wells are being replaced.
"There are also wells out there over 100 years old still being used," he said.
Arsenic is a chemical element that is part of the earth's crust and naturally occurs in soil and rock. According to MDH, arsenic can dissolve from the soil or rock into groundwater, and almost all sources of arsenic in well water in Minnesota are naturally occurring. Arsenic is present in the environment from human applications as well, including from its use in pesticides and treated wood products, although these uses are in decline because of the health concerns.
MDH reports that an oral dose of 70,000 to 180,000 micrograms of inorganic arsenic, or about the weight of a few grains of rice, is deadly to most humans. Although this is a tiny amount, it is huge in comparison to the amount of arsenic typically present in ground water, food, air and water.
On average, a person consumes about 50 micrograms of arsenic per day, mostly the less harmful organic form, from water and foods such as fish and rice. One microgram per liter is the same as one part per billion.
There is evidence that people who've consumed arsenic at levels of 100 ppb over an extended period of time can develop diabetes, nervous system problems, several circulatory diseases and high blood pressure. Studies have also linked long-term arsenic exposure to certain types of cancers, particularly of the lungs, bladder and liver. Evidence of health problems at even lower exposures, however, prompted the federal government to change the health limit from 50 ppb to 10 ppb in 2001.
One way for affected homeowners to combat arsenic contamination in wells is to install a reverse osmosis filtration system. These systems range in price from $1,000 to $3,000, according to area retailers, and can also be rented monthly.
Ahlers noted that although the majority of the samples they've tested are from lakeshore properties, this is more a function of their relationships with lake associations for water quality testing than a correlation with arsenic contamination. Arsenic can be found everywhere, not only near lakes.
The lab is currently working on a project with MDH to learn more about where arsenic occurs and a possible relationship with the amount of oxygen in the soil. The results of this analysis will be available at a future date, and hopes are it will shed light on narrowing down likely areas of contamination.
To Ahlers' knowledge, AW Research Labs is the only laboratory in the state collecting data on this subject.
The lab is currently offering discounted testing for arsenic for $20 per sample. Ahlers said it is also important for owners of private drinking water wells to test for coliform bacteria and nitrates, and they offer testing on all three for $54.
Coliform bacteria can threaten health, particularly the more virulent forms such as E. coli. MDH recommends testing once a year or any time water's appearance, odor or taste changes.
Like arsenic, nitrate is another naturally occurring chemical, also odorless and tasteless. Too much in drinking water can pose health risks, particularly to infants. In the most extreme cases, nitrate can cause "blue baby syndrome," a condition that affects the blood's ability to carry oxygen and causes an infant's skin to appear blue in color. If left untreated, the condition can result in death.
The recommendations for nitrate testing from MDH are once every two to three years, more often if positive results have occurred in the past. Expecting mothers are encouraged to test their water as well.