The metals observed in the atmospheres of cool white dwarfs (Teff≤20,000 K) have shown a new way of revealing planetary material. Since the settlement and diffusion time scales of elements heavier than hydrogen and helium in these stars are shorter that their cooling times, the atmospheric pollution may be explained by two mechanisms: the accretion of interstellar medium and accretion of planetesimals. The first one consists in getting material onto the surface while the white dwarf moves in the gravitational potential of the galaxy. The second, and most accepted scenario to explain the metal pollution in white dwarfs involves the accretion of rocky bodies and planetesimals as they are disrupted by the white dwarf tidal forces. In this work, we link the accreting mechanisms and the evolution of the star by studying observed samples of white dwarfs from different surveys and catalogs to gain insight on the mechanism behind the observed metal pollution.