The effect of various impurities and micro-alloying additions (B, N, C, O, Al, Si, S and P) on the intrinsic resistance of the Σ3 (111) GB in Tungsten has been investigated using Molecular Dynamics simulation. The atomic interactions have been accounted for through the use of the Finnis-Sinclair interatomic potentials. The fracture resistance of the GB has been characterized by computing, in each case, the ideal work of GB separation, the Mode I stress intensity factor and the Eshelby F - conservation integral at the onset of crack propagation. The results obtained suggest that pure Tungsten is relatively resistant toward GB decohesion and that this resistance is further enhanced by the presence of B, C and N. Elements such as O, Al and Si on the other hand, have a relatively minor effect on the cohesion strength of the Σ3 (111) GB. In sharp contrast, S and P greatly reduce this strength making Tungsten quite brittle. These findings have been correlated with the effect of the impurity atoms on material evolution at the crack tip.