A method for production of a bacteriostatic and fungistatic additive paste in the form of pellets masterbatch to be employed in the manufacture of plastic articles characterized in that it comprises the following steps: a) preparing a zinc oxide concentrate comprising: i) mixing a paste of nanometric zinc oxide surface treated with silanes in a high intensity mixer, with one or more polymers compatible with a resin to be used in the article, thereby obtaining a concentrate with 20% by weight of zinc oxide; and ii) mixing the concentrate of step a) i) in a twin screw extruder with the resin to be used in the article until a concentration between 1 and 10% by weight of zinc oxide is obtained; b) preparing a silver concentrate comprising: i) mixing a silver paste of nanometric metallic silver with 80-85 wt% of solids in a twin screw extruder, with a thermoplastic polymer compatible with the resin to be used in the article, thereby obtaining a concentrate with 10% by weight of silver; and ii) mixing the concentrate of step b) i) with the resin to be used in the article in a twin screw extruder until a concentration between 0.1 and 1% by weight of silver is obtained; wherein the metallic silver in the paste used for preparation of the concentrate is in the form of nanoparticles with the following specifications: Characteristic Specification Purity (%) 99-99.3 Size of the particles D 10 nm 41.5 D 50 nm 47.0 D 90 nm 56.0 Solid contents (weight %) 80-85 and the zinc oxide in the paste is in the form of nanoparticles with the following specifications: Characteristic Specification Purity (%) 100 Size of the particles D 10 nm 0.04-0.09 D 50 nm 0.050-0.087 D 90 nm 0.1-0.3 Solid contents (weight %) 45-50 and c) mixing the zinc oxide concentrate of a) and the silver concentrate of b) in a twin screw extruder to obtain the bacteriostatic and fungistatic additive paste, wherein the additive paste has a ratio of ZnO:Ag° ranging from 10:90 to 90:10; and wherein the fungistatic and bacteriostatic additive paste has an effective concentration of 0.01 to 0.5 % by weight of the plastic formulation. a) preparing a zinc oxide concentrate comprising: i) mixing a paste of nanometric zinc oxide surface treated with silanes in a high intensity mixer, with one or more polymers compatible with a resin to be used in the article, thereby obtaining a concentrate with 20% by weight of zinc oxide; and ii) mixing the concentrate of step a) i) in a twin screw extruder with the resin to be used in the article until a concentration between 1 and 10% by weight of zinc oxide is obtained; i) mixing a paste of nanometric zinc oxide surface treated with silanes in a high intensity mixer, with one or more polymers compatible with a resin to be used in the article, thereby obtaining a concentrate with 20% by weight of zinc oxide; and ii) mixing the concentrate of step a) i) in a twin screw extruder with the resin to be used in the article until a concentration between 1 and 10% by weight of zinc oxide is obtained; b) preparing a silver concentrate comprising: i) mixing a silver paste of nanometric metallic silver with 80-85 wt% of solids in a twin screw extruder, with a thermoplastic polymer compatible with the resin to be used in the article, thereby obtaining a concentrate with 10% by weight of silver; and ii) mixing the concentrate of step b) i) with the resin to be used in the article in a twin screw extruder until a concentration between 0.1 and 1% by weight of silver is obtained; wherein the metallic silver in the paste used for preparation of the concentrate is in the form of nanoparticles with the following specifications: Characteristic Specification Purity (%) 99-99.3 Size of the particles D 10 nm 41.5 D 50 nm 47.0 D 90 nm 56.0 Solid contents (weight %) 80-85 and the zinc oxide in the paste is in the form of nanoparticles with the following specifications: Characteristic Specification Purity (%) 100 Size of the particles D 10 nm 0.04-0.09 D 50 nm 0.050-0.087 D 90 nm 0.1-0.3 Solid contents (weight %) 45-50 and i) mixing a silver paste of nanometric metallic silver with 80-85 wt% of solids in a twin screw extruder, with a thermoplastic polymer compatible with the resin to be used in the article, thereby obtaining a concentrate with 10% by weight of silver; and ii) mixing the concentrate of step b) i) with the resin to be used in the article in a twin screw extruder until a concentration between 0.1 and 1% by weight of silver is obtained; wherein the metallic silver in the paste used for preparation of the concentrate is in the form of nanoparticles with the following specifications: Characteristic Specification Purity (%) 99-99.3 Size of the particles D 10 nm 41.5 D 50 nm 47.0 D 90 nm 56.0 Solid contents (weight %) 80-85 and the zinc oxide in the paste is in the form of nanoparticles with the following specifications: Characteristic Specification Purity (%) 100 Size of the particles D 10 nm 0.04-0.09 D 50 nm 0.050-0.087 D 90 nm 0.1-0.3 Solid contents (weight %) 45-50 and c) mixing the zinc oxide concentrate of a) and the silver concentrate of b) in a twin screw extruder to obtain the bacteriostatic and fungistatic additive paste, wherein the additive paste has a ratio of ZnO:Ag° ranging from 10:90 to 90:10; and wherein the fungistatic and bacteriostatic additive paste has an effective concentration of 0.01 to 0.5 % by weight of the plastic formulation.