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Rights: The University of Waikato
Published 18 June 2008

Dr Ravi Gooneratne, Lincoln University, describes how using an organism to measure pollutants enables us to look at the effect a chemical has on living creatures rather than just the amount or type of the chemical. Not all chemicals are able to be absorbed by the body, or have an effect even if they are absorbed – this is called the bioavailability of the chemical.


Why we do this, you know, use earthworms instead of analysing of chemicals in the lab, is, as you know, chemical analysis is quite expensive, it takes quite a long time using fairly sophisticated instruments. This method is cheap, and we can get a reading fairly quickly. Sometimes we can be exposed to fairly high concentrations of a chemical but that chemical may be in a form that we are not able to absorb – and that is called bioavailability – because if the bioavailability of that chemical is slow, then less of that chemical gets into the body and therefore what we have is less effect, so whereas when you do a chemical analysis, what they’re looking at is the total concentration of the chemical, so in fact you might get an over-estimation of that chemical in the soil, whereas with this method, it shows that the chemical gets into the body and that’s why it has an effect on the nervous system. One of the advantages of this test is because we don’t kill the animal – we can do daily measurements on the same worm so we can see a sort of a gradual reduction in conduction velocity over a period of time.

Dr Chris Nokes, ESR