Since its introduction in 1980, ICP-MS evolved from a lab-built instrument to a family of commercially available analytical techniques, ranging from single-collector quadrupole mass filter units (ICP-QMS) to single-collector and multi-collector sector-field based ICP-MS instruments with high mass resolution capabilities. The versatility of ICP-MS units as (i) environmental regulatory monitoring tool for the determination of major and trace elements, (ii) elemental-specific detector in the context of hyphenation with different separation techniques and (iii) mass spectrometer for the determination of isotope ratios is endorsed in this dissertation. As an introduction, the synchronicity in the emergence of (Flemish) environmental legislation on the one hand and that of ICP-MS in environmental analysis since 1980 on the other hand is discussed. Subsequently, ranges of background concentrations of heavy metals are summarised for all environmental compartments in Flanders based on European Standard ICP-MS methods and on a selection of non-polluted background locations (derived from regulatory monitoring studies). Thereafter, the scientific papers covering the development of methods based on ICP-MS for the determination, speciation and isotopic analysis of metals and oxy-anions in an environmental context are presented (see timeline) with emphasis on the connecting thread of the PhD dissertation, i.e., the relation between the ICP-MS measurement, the environmental issue and the regulatory context.