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Pesticides double the risk of developing Parkinson’s disease

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Pesticides double the risk of developing Parkinson’s disease

Pesticides double the risk of developing Parkinson's disease

Exposure to pesticides doubles the risk of developing Parkinson’s disease in farm workers. Thus concludes a study by a research team from UPMC and InsermNouvelle fenêtre’s NeuroepidemiologyNouvelle fenêtre Unit. The study, headed by Alexis Elbaz, was recently published in "Annals of NeurologyNouvelle fenêtre".

The causes of Parkinson’s disease, the most frequent neurodegenerative pathology after Alzheimer’s, are unclear. It seems that the disease is triggered when environmental factors add to a genetic predisposition. One tangible element of the hypothesis is MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), a chemical substance capable of inducing parkinsonian symptoms: slow movements, stiffness of limbs, trembling, etc.

The chemical factor proven in humans

MPTP has long been used in Parkinson’s research on primates, but its effects on humans had only been observed incidentally. Doses of MPPP, an opiate close to heroin, accidentally contaminated by MPTP, caused parkinsonism in users. When it penetrates into a region of the brain called the substantia nigra, MPTP is transformed into MPP+, a toxin which destroys the dopamine-producing neurons involved in motor control. The chemical structure of MPP+ is close to that of Paraquat, an herbicide used in agriculture… reason enough to stimulate research on the influence of pesticides on the development of Parkinson’s.

Effect of pesticides doses on the disease: an alarming discovery

The Neuroepidemiology team lead a meticulous study involving hundreds of retired and active French farm workers. “They were seen at home by occupational doctors who reconstituted their careers in detail, looking at each farm, agricultural product and method. Three main types of pesticides were examined: fungicides, insecticides and herbicides” explained Alexis Elbaz. The results showed that people who had used pesticides professionally were more often Parkinson’s sufferers than the control subjects. “The risk doubles in those who have used insecticides – in particular organochlorides such as lindane and DDT – and it increases with the number of years of exposure”. Like MPTP, these organochloride insecticides cross the encephalic barrier and, being lipophilic, fuse easily with the brain’s fatty cells.

To be continued…

Though now banned in France, organochloride insecticides were once widely used and linger for many years in the environment. In addition, accordingly to Alexis Elbaz “we cannot rule out a link between other, less common products and Parkinson’s disease”. Currently, the Neuroepidemiology Unit is preparing a new study based on geographic parameters, which will measure whether certain farming methods are linked to an increase in frequency of the disease.


Emmanuelle Manck

Read the studyNouvelle fenêtre