As MS is likely to be a preventable disease we should be doing everything we can to reduce our exposure to modifiable risk factors. Smoking, passive smoking, solvent exposure and air pollution have all been linked to an increased incidence of MS. It has always been argued that air pollution may work by acting as a filter for ultraviolet light and hence increases one's risk of getting MS by reducing UVB exposure, which is important for vitamin D synthesis in the skin. However, I am not sure this is the case as common to all these exposures, including air pollution, is inflammation in the lungs. The current hypothesis is that inflammation in the lungs changes or alters proteins via a process called post-translational modification, which converts normal proteins in highly immunogenic autoantigens that trigger autoimmune disease. There is good support for the latter hypothesis in rheumatoid arthritis, but to the best of my knowledge outside of animal models, the evidence in MS remains...