Researchers believe a factor is a chemical used in drycleaning and household products such as shoe polishes and carpet cleaners in the US.

Asked about the future of Parkinson’s disease in the US, Dr Ray Dorsey says, “We’re on the tip of a very, very large iceberg.”

Dorsey, a neurologist at the University of Rochester Medical Center and author of Ending Parkinson’s Disease, believes a Parkinson’s epidemic is on the horizon. Parkinson’s is already the fastest-growing neurological disorder in the world; in the US, the number of people with Parkinson’s has increased 35% the last 10 years, says Dorsey, and “We think over the next 25 years it will double again.”

Most cases of Parkinson’s disease are considered idiopathic – they lack a clear cause. Yet researchers increasingly believe that one factor is environmental exposure to trichloroethylene (TCE), a chemical compound used in industrial degreasing, dry-cleaning and household products such as some shoe polishes and carpet cleaners.