Currently, environmental monitoring is largely based on measuring concentrations of a limited number of environmental pollutants. However, international research has shown that up to 99% of the toxic effects that can be measured in the environment are caused by unknown chemicals, which are completely overlooked when focusing on concentrations of known environmental contaminants. Our effect-based methods can be used to measure the total effect of toxic substances in environmental samples, both known and unknown compounds. The methods show the total effect, the so-called cocktail effect, which occurs when several compounds interact. Our methods can be used to monitor time trends and spatial variations in the occurrence of environmentally hazardous substances or. The methods can also be used to sources-trace emissions. Our effect-based methods have been used for environmental monitoring by both state and regional authorities.