Minnesota environmental officials carried out a study of state waterways, which unveiled the widespread contamination of chemicals, personal care products and other materials. For the study, the researchers from the Minnesota Pollution Control Agency tested 11 lakes and four streams for the presence of 125 compounds in 2013.

As per the analysis, 56 chemicals in rivers downstream coming from wastewater treatment plants and 33% chemicals in upstream waters and the lakes were found to have 27 chemicals. The chemicals were found both in extremely populated and remote areas.

In fact, traces of the X-ray drug iopamidol were found in around three-quarters of the lake samples and the maximum concentration was found in Voyageurs National Park. DEET was found to be evidence of the most common insect repellant in more than 90% of lake samples.

There could be a number of reasons for the presence of dozens of chemicals upstream from water treatment plants, including septic systems, stormwater runoff, dust or transmission through rainfall.

Study's lead author Mark Ferrey said, "Recent research has shown that a surprising number are found even in remote lakes or upstream waters. But we have a lot to learn about how they end up there".

Other northern lakes have also been tested positive for chemicals. The PCA is working with the Minnesota Department of Health to assess potential human health impacts from long-term, low-level exposure to the chemicals found in the state waterways.