General Assessment Methodology (GAM)

The most recent version of the General Assessment Methodology (GAM) (2016) has been adopted in july 1th 2016, a methodology adopted by what was then the Committee on Integrated Water Management (CIW). The CIW report was based on the ecotoxicological parameters and criteria under European legislation on the classification of substances and mixtures as laid down in the Dangerous Substances Directive and the Dangerous Preparations Directive.

The new version of the GAM takes the most recent developments in European legislation into account (REACH Regulation as successor to the above directives and the CLP Regulation). In 2015, the Ministry of Infrastructure and the Environment also adopted policy on Substances of Very High Concern (SVHC) for water. This approach has also been incorporated into the GAM update. Moreover, the document was updated for use under the forthcoming Environment and Planning Act as part of the assessment framework for discharges.

Part of general water quality policy, the GAM is a methodology for classification of the aquatic hazard of substances and mixtures into categories (Z, A, B or C), based on intrinsic properties of substances, such as toxicity, carcinogenicity and mutagenicity. Aquatic hazard is understood to mean: ‘the degree to which a substance is likely to have adverse effects on the aquatic environment’. Key differences from the old GAM are that biodegradability is used as a starting point for the assessment of substances and mixtures, that SVHC have been added as a separate class (Z) and that the rules for assessment of mixtures have been brought in line with European legislation.

A software tool has been developed to guarantee uniform implementation of the GAM. Based on specific substance data, this tool generates the classification of a substance or mixture into one of the GAM classes.