More information about the waters of Lake Mälaren

Lake Mälaren is Sweden’s third biggest lake. It provides drinking water to around 2.5 million people. We have a responsibility to preserve and protect the environment so that future generations have clean water to drink.

Mälarens vattenvårdsförbund (the Lake Mälaren Water Management Association) does an important job, which involves sampling and analysing the water. Residues of nicotine, PFAS and medications have been measured. Levels vary depending on the season. There are higher concentrations of anti-depressants in autumn and allergy medications in spring, for example. Our treatment plants are not designed to remove pharmaceutical residues or PFAS substances. Although some is captured, significant amounts still flow into Lake Mälaren. One concern is what is known as the cocktail effect – what happens when various substances interact. Low levels of individual substances may not do all that much harm. But as yet we do not know how several substances collectively affect the environment and aquatic life. The Lake Mälaren Water Management Association is trying to find out more about this, with the help of researchers.