Over time, many different groups of substances became the focus of interest, so their occurrence, behaviour and effects were studied. While in the 1990s, it was detergents and the formation of foam in water, later the causes of discolouration around tanneries were researched, as well as the presence of chemicals and pollutants near industrial plants. Organochlorine pesticides, brominated flame retardants, perfluoroalkyl substances or PFAS, organotin compounds are some examples of such Emerging substances. After pesticides and industrial chemicals, active pharmaceutical ingredients, cosmetics and personal care products have also become "Emerging substances". Ultimately, however, it is the effect of the substances-whether persistent, bioaccumulative, mobile, toxic or even endocrine disruption-that attracts attention and triggers legal regulations. As the substances and the methods for their detection changed, so did the corresponding legislation. This in turn led to the use of new or slightly modified substances and substance groups. Innovative methods such as non-targeted analytics and biological effect tests or bioassays are now being utilised to address the variety and combined effects of the existing substances. In order to ensure comprehensive groundwater and water protection, the investigation and assessment methods must be developed. Furthermore, the existing and newly acquired knowledge need to be translated into regulatory consequences more quickly. Beyond that, a comprehensive societal transformation with regard to the sustainable use of natural water resources is essential for environmentally sound and healthy development. This must therefore be implemented on many different levels; with knowledge transfer and awareness-raising also having a significant role to play.