The study published in the journal Annals of Neurology, was based on interviews with 99 pairs of twins in the USA and examined details of their lifetime exposure to six solvents previously associated with the condition in medical literature. One of each pair suffered from Parkinson’s but the other did not.

Researchers concluded that: “Exposure to specific solvents may increase risk of Parkinson’s. TCE is the most common organic contaminant in groundwater, and perc and CCl4 are also ubiquitous in the environment.”

The report calls for more studies to determine whether TCE and perc actually cause Parkinson’s disease, and if not, how they influence the development of the disease.