Some substances are used because of their specific biological activity (pharmaceuticals, biocides, plant protection products etc.). Some even have properties preserving the required effect for as long as possible, i.e. they are stable and non-degradable. However, this also means that they pass the municipal wastewater treatment plant almost unaffected and enter the aquatic environment.

Damage to aquatic life

Even at low concentrations, micropollutants can inadvertently have the very effect on aquatic life that was intended for their actual application, e.g. herbicides applied to kill weeds prevent photosynthesis in algae, neurotoxic insecticides damage the nervous systems of aquatic organisms and endocrine substances affect fish reproduction.

Some substances trigger other undesirable side effects in aquatic life. For example, in the worst case the widely available analgesic diclofenac can cause kidney damage in humans. The same effects are now being observed in trout. Flame retardants used in upholstery, electrical and electronic products, buildings etc. to prevent fire can disrupt reproduction in aquatic organisms. More subtle damage, such as behavioural problems (caused among other things by the disruption of olfactory orientation) or damage to the immune system of organisms is also possible.

The situation is made more complicated by the aggregation effect of similar substances and the effects of complex substance mixtures. Additional stress factors such as UV radiation and elevated temperatures may additionally increase the damage. Because the current knowledge about these risks is very limited, more research is needed in this field.

Effect on drinking water resources

In Switzerland, more than 80% of drinking water is obtained from groundwater (including springs). The remainder is supplied from lake water and river bank infiltrate. River water containing micropollutants can infiltrate [AC1] the groundwater and affect the quality of this drinking water resource. Depending on the treatment, drinking water obtained from lake water and bank infiltrate can therefore still contain micropollutants.

Based on current knowledge, the micropollutant concentrations detected in groundwater and surface waters are harmless to human health. Nevertheless, as a precautionary measure, pollution of drinking water resources should be prevented as far as possible.

Objectives of water protection

The purpose of water protection is to prevent harmful effects in the aquatic environment, in particular it is aimed at human, animal and plant health. Micropollutants currently represent a water protection challenge. According to the FOEN water quality can be further improved by reducing inputs of micropollutants.