Disclosed is an in vitro method to determine efficacy of a cosmetic cleansing composition or an active ingredient comprised therein to remove particulate pollutants adhering to the skin, comprising the steps of: (i) contacting a human skin-equivalent with a model fine particulate matter resembling a particulate atmospheric pollutant and measuring a first concentration of said model fine particulate matter on said human skin equivalent by an imaging technique； (ii) cleansing said human skin equivalent bearing said model fine particulate matter thereon with said cosmetic cleansing composition and measuring a second concentration of said model fine particulate matter on said human skin equivalent by the imaging technique； (iii) differentiating between said first and said second concentration； and, (iv) ascertaining said efficacy from the information of step (iii), wherein, said technique is a spectroscopic or microscopic chemical imaging technique, where said chemical imaging does not mean or include colorimetric or digital image analysis and wherein said human skin equivalent is artificial skin, donor skin, living skin equivalent or pig skin and wherein said model fine particulate matter is in the form of beads comprising polystyrene and a fluorescent material, further wherein said microscopic imaging technique is fluorescence microscopy and said human skin- equivalent is artificial skin.L'invention concerne un procédé in vitro pour déterminer l'efficacité d'une composition de nettoyage cosmétique ou d'un ingrédient actif compris dans celle-ci pour éliminer des polluants particulaires adhérant à la peau, comprenant les étapes consistant à : (i) la mise en contact d'un équivalent de peau humaine avec une matière particulaire fine de modèle ressemblant à un polluant atmosphérique particulaire et la mesure d'une première concentration dudit modèle de matière particulaire fine sur ladite peau humaine équivalente par une technique d'imagerie ； (ii) le nettoyage dudit équiv
