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 ... 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." 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. To date, the clearest evidence around the risk of TCE to human health is derived from workers who are exposed to the chemical in the work-place. A 2008 peer-reviewed study in the Annals of Neurology, for example, found that TCE is "a risk factor for parkinsonism." And a 2011 study echoed those results, finding "a six-fold increase in the risk of developing Parkinson's in individuals exposed in the workplace to trichloroethylene (TCE)." While some countries heavily regulate TCE (its use is banned in the EU without special authorization) the EPA estimates that 250m lb of the chemical are still used annually in the US. TCE is currently estimated to be present in about 30% of US groundwater. Using activated carbon filtration devices (like Brita filters) can help reduce TCE in drinking water.