Bioconcentration Testing

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click to enlarge Animals living in the aquatic environment take up chemicals from water as well as from the food they eat. For many chemicals, the concentration in the animal is higher than the concentration in the fish.

Scientists measure the chemical's bioconcentration  factor (or BCF), which tells us how much more of the chemical is in the fish than in the water. If the BCF=2, the concentration of the chemical in the organism will be twice the concentration in the water. This is important because the amount of a chemical that gets into an animal helps to determine the toxicity of that compound. The BCF also helps scientist to calculate how much of a chemical an organism will take up from its food.

BCF can be measured in the laboratory or calculated using computer models (see QSAR). When we measured surfactant BCF values in fish, we noticed they were lower than predicted by computer models. These models were based on a physical chemical property called the octanol : water partition coefficient (or Kow). The Kow basically tells the scientist how soluble the chemical is in fat, since the fat is where many chemicals get stored in the body. Unfortunately, these computer models do not consider the possibility that chemicals can be metabolised by the organism. Metabolism  is the breakdown of food and other chemicals into smaller molecules. These smaller molecules are quickly eliminated from the body.

We think the reason the measured BCF values were lower than the computer model predicted was due to metabolism in fish. To help figure this out, P&G is using an in vitro system to study the metabolism of chemicals in fish. In vitro studies are currently being conducted on selected chemicals (particularly surfactants) for which data can be compared to in vivo data. Our hope is that this research will lead to toxicity, BCF and metabolism test methods that do not use animals. This work is linked with our work on QSAR, and we hope to further improve these tools so that we won't have to conduct even in vitro work in the future.