The chemical state of surface waters (reported to EU in 2010) is classified on the basis of environmental quality norms defined for 42 harmful or hazardous substance and substance groups. The norms, which refer to annual average concentrations of the substances in aquatic environments, were included in Government Decree 1022/2006 on Substances Dangerous and Harmful to the Aquatic Environment. Some of the norms applied in evaluating the chemical state of water bodies have not yet been fully enacted in official legislation, but they still serve as useful guidelines in the classification procedure.
The concentrations of harmful and hazardous substances measured in Finland’s surface waters have generally been below the provisionally defined norms (environmental quality standards), and in many cases the substances have not been detected at all. Chemical statuses worse than “good” have been assigned to several rivers in Ostrobothnia which flow through regions with acidic, sulphate-rich soils, and contain high concentrations of substances including cadmium. Some of the metals that affect the chemical state of water bodies also occur naturally, and this factor must be considered in classifications to ensure that statuses are not misleadingly lowered by naturally high concentrations of metals.
There is still a lack of data about the occurrence in surface waters of substances that affect their chemical state, however. There is also a need to enhance the analytical procedures used in measuring concentrations of substances. Evaluations of chemical state have not considered isolated cases where measurements reveal unusually high concentrations. The plastic additive DEHP phthalate, for instance, has on several occasions been observed in concentrations exceeding norms; but it has not been possible to base a classification on limited information without further monitoring of concentrations of the substances in question. Surface-active substances such as the nonylphenols used in detergents can be found in low concentrations at many monitoring stations, but their concentrations do not exceed norms. The use of these substances in their most significant applications has been banned since the beginning of 2005. Some substances used to protect plants, such as phenoxy herbicides have been found in rivers entering the sea, in concentrations within norms.