An international study has linked an industrial solvent to Parkinson's disease.Researchers found a six-fold increase in the risk of developing Parkinson's in individuals exposed in the workplace to trichloroethylene (TCE).Although many uses for TCE have been banned around the world, the chemical is still used as a degreasing agent.The research was based on analysis of 99 pairs of twins selected from US data records.Parkinson's can result in limb tremors, slowed movement and speech impairment, but the exact cause of the disease is still unknown, and there is no cure.Research to date suggests a mix of genetic and environmental factors may be responsible. A link has previously been made with pesticide use.