Drug accumulation can be expressed for a specific specimen, such as plasma, or for the whole animal. Those quantities should be kept separate. Muir and colleagues compared fish plasma and surface-water measurements in a wetland receiving treated wastewater in southern Ontario.
The researchers studied caged and wild goldfish and wild carp. They calculated plasma-based accumulation factors from measurements in plasma and surface water. In carp, the combined diazepam and oxazepam measure had a reported factor of 927 litres per kilogram. Modeled accumulation did not agree well with observed measurements overall.
The authors noted that the model was designed for whole-body measures and that some compounds absent from plasma might be found in other tissues. Species, site and chemical properties can affect the comparison. A plasma-based factor cannot be used as a whole-fish concentration or a measure of harm without additional evidence addressing that specific question.