Strengths of our study were the use of full occupational histories in combination with a JEM to objectively estimate life-time occupational exposures, because reporting occupational histories is less influenced by a potential recall bias than self-reported use of substances or exposures. Furthermore, instead of using a single category of solvent exposure, we studied two classes of organic solvents: aromatic and chlorinated solvents separately. In addition, we had detailed information on lifestyle factors most notably detailed information on smoking which in line with a range of previous reports, showed a reduced risk of PD in smokers.