Sustainability Issue #1 January 2009

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The general population in Sweden is primarily exposed to pesticides indirectly through residues in food, chiefly from fresh fruit and vegetables. Direct exposure through domestic use of pesticides or proximity to areas where crops are sprayed are the next commonest sources of pesticide residues in the body. Those who spray are exposed most. Against the background that more than one half of the fruit and green vegetables that we eat is imported, treatment with pesticides in other countries is significant from the Swedish perspective also. In our food, residues of pesticides are found in about one half of the samples taken. Almost six per cent of imported fruit and vegetables have contents in excess of permitted values. The corresponding percentage for fruit and vegetables grown in Sweden is about one half of one per cent.

Biomarkers show exposure

The vision of a sustainable society incorporates a nontoxic environment, good dietary habits and safe foods, and reduction of the exposure of people and the environment in Sweden to pesticides. One way of monitoring such a development is to check with the help of biomarkers how the population is exposed to pesticides. Biological monitoring of exposure to substances which are still in use has been performed in other countries but not previously in Sweden.

On the initiative of the County Administrative Board in Skåne and with the support of the Swedish Environmental Protection Agency, the Occupational and Environmental Medicine Clinic (AMM) at Lund University Hospital has, over the period 2004-2008, investigated the residual contents of several pesticides in urine. The contents are also related to data supplied by the participants in response to a questionnaire. Up to date, we have collected material from about 300 people, comprising the adult general population in a medium Swedish town, and also from a group of vegetarians and a group of immigrants of the first generation. The general population does not include people who are in contact with pesticides in their work. We have also collected samples from some groups who have a slight exposure in their work. In another project at AMM in Lund, adults and children in Central America from the general population and those exposed in their work were also examined with similar methods.

In Sweden and the world, hundreds of active substances are used as pesticides. We now have methods for the analysis of biomarkers for 14 substances. As the analysis method, we have used liquid chromatography with tandem mass spectrometry (LC/MS/MS). We have studied markers for pesticides against weeds, mould and insects. The contents we can determine with our methods are at such a level that we can analyse these substances in the very low contents found in the general population in Sweden.

In order that we should be able to evaluate the contents we have found, and as a control for our methods, we have conducted a number of experiments where two persons were asked to drink a certain dose of various pesticides.  We then measured the quantity excreted in the urine and the rate at which residues leave the body. We have been able to establish that our methods work well for analysis of the low contents in the urine of the general population, and that early morning urine can be used to monitor the substances so far investigated.

Higher contents in the spring

On examining the first 100 Swedish population samples collected in 2004 as total urine quantities, we found that residues of all the investigated pesticides can be present in urine. The contents in samples collected from people aged over 40, from women and from those who answered in the questionnaire that they do not prefer organic foods even when such are available, were slightly higher in samples collected in the spring/ early spring than in the autumn. None of the participants used the investigated pesticides in their homes.

More in vegetarians and golfers

Urine collected later as early morning samples from the general population gave similar results. One group of vegetarians had slightly higher contents, and for certain pesticides even up to three times higher contents, than non-vegetarians,. Those whose hobby is golf also had slightly higher contents than non-golfers.

Some groups who are exposed to pesticides in their work were investigated before and after work, and the exposure is very well reflected in the urine samples. Contents after exposure are ca 10 times as high as those before work.

On comparing these contents with the contents in urine samples from adults and children in Central America, interesting differences are seen. It is clear that the pesticides which are used there on a large scale produce higher contents than those in the Swedish samples – but the differences are nevertheless not as large as may be thought: adults from the Central American general population have 2-3 times higher contents than Swedish people, and "environmentally exposed" children in Central America have 5-10 times higher contents than we have, while the contents in children from villages where there is no spraying have contents at the same level as Swedish adults.

We can thus demonstrate a low dose exposure to the investigated pesticides in the Swedish general population. The most important source is probably our food, chiefly fruit and vegetables, a large proportion of which is imported. But exposure other than that through food may also be significant, even if to a lesser extent in Sweden than in many European and non-European countries.

Organic food lower load

There may be reason to make a special study of risk groups in the population – apart from those who consume a lot of fruit and vegetables, obviously those who are exposed to pesticides in their work or in their leisure time, and also others who have a higher exposure, e.g. children who eat "conventionally" produced food. In other countries, biomarker studies of children have shown both that children are generally more exposed, and that consumption of a "conventional" diet produces a higher "load" of the residues of certain insecticides than consumption of organic food. In countries where farming is more chemical-intensive than in Sweden, there is particular reason to monitor and reduce the exposure of the population.

Whether the contents of pesticide residues have any significance for health has not been investigated in the Swedish studies. There may however be risk groups for whom the general indirect low dose exposure to pesticides – and other substances in our environment – poses a risk, especially if it is borne in mind that several substances may act through the same mechanism and have the same target organ, and if it is also borne in mind that some of us have a lower capacity than others to metabolise and excrete alien substances from the body.

Future exposure studies of pesticides could to advantage be combined with well substantiated data regarding diet and drinking water, and performed in cooperation with others, for example the Swedish Food Administration.

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