Processing Magazine

Chemical pollution in Minnesota surface waters widespread, studies find

May 14, 2013
Lake Superior
For the lakes study, 50 lakes were randomly selected across Minnesota.

Two new studies by the Minnesota Pollution Control Agency (MPCA) found that chemical pollution in the state's surface waters is more widespread than previously thought.

In 2010 and 2012, the MPCA sampled lakes and rivers using funds from the state of Minnesota and the U.S. Environmental Protection Agency, part of nationwide EPA surveys to find out what’s in the nation’s waters.  

For the lakes study, 50 lakes were randomly selected across Minnesota. Samples were collected and analyzed for 125 chemicals. The study included analysis of “endocrine-active compounds” (EACs), so called because they mimic or interfere with the actions of naturally occurring hormones. These chemicals can have adverse effects on aquatic ecosystems and fish.

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Results of the lake study were generally consistent with findings of previous but smaller studies that found commonly used chemicals widely distributed in Minnesota lakes. The insect repellent DEET was found in 76% of the lakes sampled, making it the most frequently detected chemical.  Chemicals not previously analyzed -- including cocaine, the antidepressant amitriptyline and the veterinary antibiotic carbadox -- also were often detected in the lakes.

MPCA officials said the detection of cocaine was unexpected, one for which they couldn’t account except that other studies have shown it can attach to fine particles and might be transported long distances through the atmosphere.

The rivers study analyzed 18 chemicals, including several pharmaceuticals and personal care products, and was conducted at 150 river locations selected at random. Parabens, a family of chemicals used as preservatives for food and cosmetics, were commonly found, with methylparaben detected in more than 30% of the samples. A breakdown product of the corrosion inhibitor benzotriazole was found in 12% of the samples. Carbamazepine, used in medications to treat attention deficit hyperactivity disorder, and several antidepressants were also found.  

Many of the chemicals in the MPCA studies were detected at very small concentrations, in the low parts per trillion. Such levels are of concern because EACs have the potential to adversely affect fish and other aquatic organisms even at extremely low levels. One part per trillion is roughly equivalent to one drop in a pool of water covering the area of a football field 43 feet deep.

The MPCA plans to continue testing surface waters for pharmaceuticals and EACs on a rotating five-year basis to identify any trends that may be occurring.