This study aims to answer the following questions:

- what are the colonies' chemical contamination levels and what is the origin of this contamination (both by integrating data already available and contributing with new exposure data)?

- to what extent may such a contamination determine the colony's fate when put in its context: its genetic, pathogen/parasite load, nutritional state, climate conditions and land use around it (both through observational studies and target (semi) controlled experiences)?

- which recommendations could be proposed to mitigate the problem of colony mortality at several levels: decision making (medicament and/or pesticide authorisation and use, bee health management), scientific (further research questions), and practice (agricultural and beekeeping practice)?

- can we propose a tool box, including indicators of bee health and pesticide exposure, methods for pesticide surveillance carried out by honey bees or cost-effective surveillance programmes for colony mortality?