News items Test pesticides for possible role in Parkinson's disease

20 December 2023

Pesticides may play a role in the development of Parkinson's disease, but are not sufficiently tested for this. Researchers from Radboud university medical center, among others, propose a step-by-step testing approach that should guarantee the safety of pesticides.

Parkinson's disease is the fastest growing brain disorder in the world. It is clear that environmental factors, such as air pollution and exposure to heavy metals, play an important role in the development of Parkinson's disease. In addition, there is increasing evidence that pesticides are involved. However, these substances are not adequately tested for their possible role in Parkinson's disease. Researchers from Radboud university medical center, the Netherlands Institute for Neuroscience and the RIVM want to change this. They present a systematic testing approach for pesticides that minimizes animal suffering as much as possible.

Four test phases

The researchers propose that both existing and new pesticides go through four testing phases. Firstly, database research must show whether there are indications that a substance could cause damage to brain cells. If so, laboratory research, in which the effects of the pesticide on brain cells, should be performed. If researchers find indications of undesirable properties in those experiments too, they must test the substances in animal species that bear little resemblance to humans, such as worms or flies. The final step involves exposing mice and rats to the pesticide.

Neuroscientist Judith Homberg, last author on the article, explains this step-by-step approach: 'This way, we test the pesticides very thoroughly, without needing a large number of laboratory animals. Unfortunately, research on rats and mice is necessary to definitively determine the safety of a substance. Parkinson's disease is diagnosed based on behavioral changes, and these animals exhibit behavior that is relevant to this disease. We can also expose these laboratory animals to pesticides for a long period of time and in a similar way to humans. For example, by adding these substances to drinking water or to the air that they inhale.'

Clear plan

Neurologist and co-author Bas Bloem emphasizes the importance of the tests: 'We are still largely in the dark about the safety of these drugs. The current admission criteria for pesticides provide insufficient insight into the risk of Parkinson's and other brain diseases. We now propose a clear plan of action to properly assess safety.'

The researchers are now entering into discussions with industry and regulatory authorities. They must agree to the proposed approach and decide who will perform the tests. Bloem: 'The pesticide manufacturers must finance the research, but they should not be involved in any other way.  Independent organizations such as universities or the RIVM are suitable candidates to carry out the experiments.'

About the publication

This study was published in npj Parkinsons Disease: Towards improved Screening of Toxins for Parkinson’s Risk. L. Shan, H.J. Heusinkveld, K.C. Paul, S. Hughes, S.K.L. Darweesh, B.R. Bloem, J.R. Homberg. DOI: 10.1038/s41531-023-00615-9.

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