Radon: a possible risk factor in multiple sclerosis.

Ecological studies in Norway, using a method for spatially moving bivariate correlation analysis, show that south of 65 degrees N, there are significant positive correlations (p < 0.01) for rates of multiple sclerosis (MS) versus contents of radon (Rn) in indoor air, and significant negative correlations for MS rates versus fallout of magnesium (Mg) and amounts of precipitation. Based on these data, we propose the hypothesis that the content of Rn in inhaled air is a risk factor in MS. The release of harmful Rn levels to the air may be influenced by (1) the levels of exchangeable Mg in soil, which may affect the soil content of the Rn precursor radium (Ra), and (2) the amounts of precipitation through its effects on soil moisture, which is one of the factors controlling Rn emanation from the soil. This hypothesis agrees with several of the known epidemiological characteristics of MS. Copyright 2003 S. Karger AG, Basel