This paper presents the update of the atmospheric transfer matrices in the MINNI integrated assessment modelling system for air quality in Italy. The performed tests demonstrated the feasibility of improving the horizontal resolution from 20 km to 4 km on the ENEA CRESCO HPC infrastructure. This allows reaching the spatial detail of state-of-art operational chemical-transport modelling systems in Europe but offering a faster way to estimate the efficacy of different air pollution control policies in reducing the impact on human health and the environment.