An aqueous polymer dispersion with an average particle size of less than 1000 nm comprising a) a polymer carrier prepared by heterophase radical polymerization of at least one ethylenically unsaturated monomer in the presence of b) an oil-soluble organic UV absorber selected from the class of p-aminobenzoic acid derivatives; salicylic acid derivatives; benzophenone derivatives; diphenyl acrylate derivatives; benzofuran derivatives; polymeric UV absorbers, comprising one or more organosilicon radicals; cinnamic acid derivatives; camphor derivatives; s-triazine derivatives; trianilino-striazine derivatives; menthyl anthranilates; and benzotriazole derivatives; wherein the weight ratio of the oil-soluble organic UV absorber (b) to polymer carrier (a) is greater than 50 parts UV absorber per 100 parts of carrier; and c) a surfactant selected from c1) a nonionic surfactant selected from c11) the condensation product of a C6 to C18 fatty alcohol or C6 to C18 fatty acid and a mono- or disaccharide; and c2) an anionic surfactant selected from c21) sulfosuccinates and sulfosuccinamates; c22) fatty alcoholates; and c23) mixtures of phosphoric acid esters and fatty alcohols having from 6 to 18, preferably from 8 to 10, carbon atoms. The aqueous polymer dispersions show unexpectedly high sunscreen effects and a positive skin feeling. They have excellent anti-pollen, anti-dust and anti-oxidant performances in sun screen compositions.