Organic solvents and multiple sclerosis: a synthesis of the current evidence.

To evaluate the possible relation between exposure to organic solvents and the development of multiple sclerosis, we carried out a best-evidence synthesis of the available information. We found 13 studies with varying methodology that included information on solvent exposure. In 10 of the studies, there were indications of an increased risk of multiple sclerosis in relation to solvent exposure. We made three selections of studies for both pooled analyses and meta-analyses. The relative risk point estimates that we obtained varied from 1.7 to 2.6. Our evaluation is consistent with the hypothesis that organic solvents may be a cause of multiple sclerosis.