Science - October 14, 2004

Commentary: Unused pesticides

The world food organisation FAO warned recently of ‘chemical time bombs’. In developing countries and some Eastern European countries old supplies of pesticides are lying around in sheds, under tarpaulins or in the open air: a serious threat to public health. The FAO estimates that of the two hundred thousand victims each year, many are children who play among the chemicals. Is the problem really that bad?

Dr Arnold van Huis, Laboratory of Entomology:

‘I have seen serious examples myself. Next to a sugar cane factory in Zanzibar there were rusty cans of pesticides that were leaking into the ground water. The chemicals had come from China, but the people there couldn’t read the Chinese characters and therefore didn’t know what was in the containers. Large amounts of chemicals are also used to fight malaria. I remember seeing open sacks of poison for malaria next to a place where children were playing. Pesticides are often left lying in fields in the open air or in the sun. But it’s not only pesticides used for crop protection or against malaria, industrial chemicals are also a problem. And then there are substances which are no longer manufactured because they are considered too dangerous, but of which there are still unused supplies lying around. Dieldrin is an example, an organochlorine that decomposes very slowly: it has been forbidden worldwide since 1990. If you want to get rid of it you have to burn it at very high temperatures, and there are no facilities for this in Africa. That means you have to ship the stuff to somewhere like the Netherlands to burn it. Or you have to ensure that there are safe storage places where leakage will not take place. You have to pack the remains in containers and make sure that the people who are doing the work are protected. That requires effort and money, from donors. The FAO has programmes and the Netherlands contributes considerable amounts to these. But if you really want to do something about the problem you have to address the cause of the problem. During a locust epidemic at the end of the 1980s for example, many of the insecticides intended for pest control did not reach their destination. Donors sent pesticides to fight the locusts, but much too late, which meant that much of the stuff was left unused, lying around. There are regulations for importing chemicals into developing countries. Manufacturers have to make clear what the dangers of the substances are, and the countries themselves have to indicate whether they accept these dangers. After the locust epidemic there was much discussion about the problem of out-of-date pesticides. One idea was to set up a pesticide bank, which would be responsible for seeing that unused pesticides are not just left lying around, but are sent to other places where they are needed. But decisions on the use or purchase of pesticides are often also of a political nature. Even if the technical experts agree that pesticides are not necessary, local leaders often still decide to use them to keep the farmers happy. Many substances are used that are not necessary. Responsibility also lies with donors to see that this doesn’t happen.’

Joris Tielens