B-1/2 values of pyrene-dimethylaniline radical pair system in different single and binary solvents have been measured. The data supports the observation of Grampp et al., (Phys. Chem. Chem. Phys. 14 (2012) 3155) in a different system explained on the basis of lowering of local concentration of neutral donor molecules in the dielectrically enriched polar micro-domain around the radical ion pair. In this letter an alternative explanation based on the modulation of size of the polar micro-domain with change in e has been proposed and the variation of B-1/2 in single solvents has been explained on the basis of diffusivity and specific solvent property like H-bonding. (C) 2012 Elsevier B. V. All rights reserved.