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Chemistry (joint degree UvA/VU)
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Academic staff

Dr. Pim de Voogt

Name: Dr. Pim de Voogt


'Where does a substance end up if I throw it in the canal? How much of it will end up in the air, how much will end up in the fish? And just how toxic will it prove to be for those fish? In my research concerning (emerging) water contaminants, I have mainly focused on the study of water-soluble polar residues in the ecosystem.'

'The field of environmental chemistry has not been researching polar substances for all that long. Studies in the 1960s mainly focused on non-polar substances, such as insecticides (DDT) and waste materials (PCBs and dioxins). Non-polar substances are characterised by the fact that they do not fully dissolve in water, and have an affinity with other non-polar substances such as fat. Animals and humans store up any non-polar contaminants in their fat tissue, where the substances generally remain without causing too many problems. The animal will not suffer until the concentration becomes too high. If, for example, breeding birds start to use up their fat reserves, any DDT stored inside them will enter their bloodstream, with potentially life-threatening consequences.'

'In the 1990s, the field of environmental chemistry undergo a major transformation. A new technology helped shift the focus to polar organic substances, which had been almost impossible to examine at low levels until that point. We owe a lot to the LC-MS: a machine that links liquid chromatography to mass spectrometry. It allows us to detect much lower concentrations of polar substances, providing an enormous impetus to the study of these substances and their effects. Polar substances that end up in the environment take a very different course than their non-polar counterparts. For example, they generally dissolve in blood, which is similar to water. As a result, they are a lot more likely to reach critical receptors and may thus cause harmful effects.'

'The introduction of new detection methods in the 1990s helped uncover a whole new range of polar substances in the environment. However, this rise in contaminants is partially deceptive. We can simply see more nowadays. A case in point would be perfluorinated compounds, which are used to make textiles and other materials water and oil-resistant. These compounds are applied in pizza boxes, extinguisher foam, raincoats and textile fibres. It wasn't until around 1996 that these substances were discovered in living polar bears, but they had already been in use since the fifties.' 

'The detection of substances in nature is just one aspect of my work. My research also focuses on the potential effects of polar substances. It's satisfying that the technique at the core of my 1990 doctoral thesis can now be applied to polar substances. Applying what are known as quantitative structure-activity relationships (QSARs), I use the chemical structure of substances to predict their behaviour in the environment: water, humans or animals. For example, we look at the number of polar groups within a molecule, or the relationship between the polar and non-polar elements. Does it matter which polar group is linked to the compound? How do substances react in different conditions; will they be absorbed when filtered through active carbon, or will they be destroyed by active ozonisation? In some cases, we create models to predict a substance's potential effects: how does the substance link to an enzyme, which part of the molecule will it link to, and how does it fit in in stereochemical terms?'

'The new techniques used to detect polar substances also come with their own set of drawbacks. Water companies, for example, sampling the inflow of water to detect harmful substances, will find around 50 different substances per sample. And this merely represents a fraction of the thousands of substances potentially occurring in groundwater and surface waters. It would simply be impossible to detect and identify them all. This is why many researchers tend to use reverse testing nowadays. An assessment of the biological effects serves as the basis for a targeted search for harmful substances. This process applies bio-testing to - for example - expose fish embryos to potentially contaminated water. Embryos are highly sensitive to polluted water: developmental defects are a clear indicator of pollutants. This technique is known as effect-directed analysis. If I were to sample some water from the canal outside, I could then use bio-testing to measure whether it contained substances that could harm living organisms. If this turns out to be the case, I would then have to carry out further research to determine which substance is causing the measured effect. This search for harmful substances is conducted by dividing the water sample into fractions and using various separation methods to divide the substances in the sample over the fractions. The bio-test is then repeated for each fraction; if the results are positive, the sample will be divided into smaller fractions. This process is repeated until, ideally, the fraction causing the problem consists of a single substance. We will then have found the offending substance.'

'In addition to my tenure at the UvA, I am also a researcher at the KWR Watercycle Research Institute, the water research institute in which all drinking water companies in the Netherlands hold a stake. As a part of my duties at the Institute, I am responsible for the chemical fractioning of water samples. We sort the molecules on the basis of their size, shape, polarity and acidity. I am interested in the sort of predictions you can make when a certain effect can be traced back to a specific fraction. As a result of the fractionation method employed, you are already familiar with some of the substance's properties.'

'Working in collaboration with KWR, Researchers at VU University Amsterdam applied effect-directed analysis to detect three teratogenous substances (teratogenous = harmful during embryonic development) in soil sampled from below a waste disposal site in Brabant. These substances disrupt the development of the spine and air bladder in fish embryos. Serious effects. If leachate from the landfill were to seep into the system, it could have a harmful effect on the viability of fish populations.'

'I would like to generate more general interest in my field. The government regards knowledge as the Netherlands' prime export product for the future. This country has always had a wealth of knowledge when it comes to water-related issues. That means my discipline is essential to the Netherlands. Environmental chemistry is in need of more skilled scientists, which starts with a larger number of students. One of the advantages of having two employers is being in a position to introduce students to the practical field during their studies. For example, I can show them how things work at water companies. The processes applied in fundamental research are often the exact same as those used by companies. We are already seeing a great deal of collaboration in this area, of which my tenures are a good example. It's this type of exchange that makes this such a fascinating field to work in.'