Abstract
Specific experiments that were performed with aquatic and terrestrial organisms have led to the conclusion that “bulk”; analyses are inadequate for the assessment of possible environmental risks. Furthermore, these experiments revealed that only specific chemical forms are bioavailable, although information about the exact nature of these forms and the chemical processes involved often remained obscure. Based on this type of experience, bioassay and biomonitoring techniques were developed and applied to determine bioavailability in a direct and realistic way.