Abstract Mental health is a complex Public Health challenge, especially youth. A better understanding of factors that contribute to youth mental health and reduce the burden of youth mental health conditions such as executive and emotional functioning is needed to develop primary and secondary prevention interventions. One of the main challenges for better understanding mental health of youth is the complexity and diversity of exposures that individuals experience throughout their lifetime. There is a wide range of factors in the environment, and individuals are exposed to different combinations of external factors depending on their location, occupation, and lifestyles. These factors include physical (e.g., noise and indoor and outdoor air), chemical and social factors (e.g., neglect and abuse, relationship conflicts) based on the exposome framework. The exposome is a guiding framework for the multi-country study EARLY involving Albania, Belgium, Germany, Israel, Moldova, Portugal, Romania, Serbia, Spain, and Switzerland. EARLY is one of the first projects to theoretically explore and empirically investigate youth mental health in line with the exposome framework. We aim to identify factors influencing youth mental health with validated exposure measures. An exploratory list of measures was collected in Albania, Belgium, Germany, Israel, Moldova, Portugal, Romania, Serbia, Spain, and Switzerland. The measures vary widely. Besides the variation, there is still a lack of standardized methods for measuring environmental exposures. Limitations of measures affect reliability and validity. Therefore, an overview of available assessment methods and steps toward improving measures will be discussed in this talk. Speakers/Panelists Karin Boode GGD GHOR Nederland, Utrecht, Netherlands Peter Van Den Hazel INCHES, Ellecom, Netherlands