Honeybees are insects with an essential function as pollinators for mostly of the agricultural and natural species, allowing so the vast majority of worldwide food production. Beyond this role, honeybees are used as excellent bioindicator of the environmental quality. The ability of honeybees to undertake the role of ecological detector is due to unique morphological and ethological characteristics of this insect. In fact, in every beehive forager bees can collect about 2 million of micro-samples per day during thier normal flying activity in an area of at least 700 ha, collecting nectar, pollen, honeydew, water, etc. Moreover, the body of honeybees is completely covered by 3 million hairs, therefore bees can intercept many particles and carry them inside the hive. Undesirable substances for bees like pesticides, heavy metals, herbicides, radionuclides get also involuntary pulled. Collected pollen loads proved to contain higher concentration of pesticides as this matrix is not ingested by bees, while highly polluted nectar will not be transformed in honey, because bees will likely get disorientated or die before coming back to the beehive. This study will analyze pollen loads coming from 21 apiaries placed along Val di Sole (Trentino, Italy), a 40 km alpine valley characterized by apple orchards in a lower part and hay meadows and pastures in the upper part. Samples will be collected in two periods of the year: after apple flowering and in July 2019. The botanical origin of the pollen loads will be identified under the microscope using palynology methods, while trace chemical analyses of ca. 500 pesticides and their metabolites will be done using liquid- and gas-chromatography methods. The data will be used to assess the pollution level of each area and the dispersion of pesticides along te valley. This thesis project is done in collaboration with the Beekeepers Association of Val di Sole, Rabbi and Peio.