OECD 305: Bioaccumulation in Fish: Aqueous and Dietary Exposure

The regulatory process for chemicals (i.e. registered under REACH, plant protection products, biocides, human and veterinary medicinal products)  require that substances undergo an assessment to identify whether they are persistent (P), bioaccumulative (B) and toxic (T). The bioconcentration factor (BCF) is the usual basis for defining the B criterion in PBT assessment. The BCF is generally derived experimentally according to OECD Test Guideline 305.

The uptake of the test substance occurs either via direct accumulation of test substance from the aqueous environment (bioconcentration) or via food (biomagnification). However, the guideline OECD 305 states that there should be a preference for aqueous exposure bioaccumulation studies to be run when technically feasible.

Fish Species

The study is regularly designed as flow through study and is carried out with juvenile fish. We perform the bioaccumulation study usually with: 

  • Danio rerio (Zebrafish) or
  • Lepomis macrochirus (Bluegill Sunfish)
  • Oncorhynchus mykiss (Rainbow Trout).

Other fish species can also be tested e.g.

  • Pimephales promelas (Fathead Minnow).
  • Oryzias latipes (Medaka)

Only healthy fish free of observable diseases and abnormalities are used in the study.

Test Set Up

 In the study a continuous flow is set using metering pump systems. The loading rate of fish is appropriate for the test species and does not exceed 1 g/L. Fish are daily fed and uneaten food and faeces are removed. 

The study is performed with a control group and one or two test substance concentrations. Application of the test substance can be done by dosing the test substance into the water phase or by application of the test substance to the feed. The test consists of two phases: the exposure (uptake) and post-exposure (depuration) phases. During the uptake phase, separate groups of fish are exposed to the test substance. They are after the end of the uptake phase transferred to a medium free of the test substance for the depuration phase. The concentration of the test substance in the fish is followed through both phases. At each sampling point a minimum of four fish are collected. Each fish is analysed individually for its test substance content. The concentration in water or food is determined during the uptake phase.

Analytical Methods

The study can be performed either using non-labelled or radiolabelled test substance. Radiolabeled test substances can facilitate the analysis of water, food and fish samples, and may be used for identification and quantification of metabolites. Our laboratory is equipped with modern analytical devices for the quantification of labelled and non-labelled test substances. This encompasses liquid scintillation counters, UPLC systems coupled with radio detector and LC-MS/MS systems as well as instruments for sample extraction or clean up.



Based on the determined concentration in fish and water or food the bioconcentration factor is calculated. The kinetic bioconcentration factor /biomagnification is calculated from the model that best describes the measured concentrations of test substance in fish. The BCF will be growth and lipid corrected.

Guidelines and Literature

OECD 305 Bioaccumulation in fish: Aqueous and Dietary Exposure