Background :
Pediatric cancers, though rare, remain a major concern due to their mortality and profound impacts on children and their families. Their etiology is still poorly understood, but environmental factors are strongly suspected. In the Pays de Retz (France), a spatiotemporal clustering of childhood cancers around Sainte-Pazanne raised concerns and citizen demands for clarification. 
This lack of knowledge can be explained by the multifactorial complexity of exposure in children, combining :
– poly-exposure, which is the cumulative, combined and/or synergistic effect of multiple agents (pesticides, endocrine disruptors, air pollution, electromagnetic fields, parental occupational exposure, etc.) in the development of cancer in children
 – and the concept of the exposome – defined as ‘all environmental exposures throughout life (including lifestyle factors), starting from the prenatal period
 This work is all the more complex given that pre-conception exposure of parents and maternal exposure during pregnancy to carcinogens are described as potentially promoting cancer in children. As a result, these ‘histories’ of exposure embedded in life trajectories must be investigated.
Objectives
The present study aims to develop a methodological tool to assess environmental exposures, integrating the concepts of poly-exposure and the exposome.
Methods
The approach is structured around three axes : (1) a systematic umbrella review of the literature on environmental risk factors for pediatric cancers ; (2) an assessment of pollutant presence based on economic activities and environmental monitoring data ; and (3) the integration of these findings into a Geographic Information System (GIS). 
This work focused on pesticide exposure, combining literature analysis with territorial data (graphical land register, national office for the distribution and sale of pesticides, treatment frequency index, and environmental measurements in air and groundwater). Based on participatory sciences and interdisciplinary approaches, our work tended to combine knowledge from different sources and field investigations.
Results
The systematic umbrella review showed a possible association between agricultural proximity and childhood leukemia, although evidence remains fragile due to methodological heterogeneity and small sample sizes. At the territorial scale near Ste Pazanne city, land use is dominated by agriculture, with practices relying heavily on pesticides, including substances classified as carcinogenic, confirmed in both air and groundwater. We were able to identify some hot spots where carcinogenic risk factors could be cumulated over time. 
Conclusion
This study constitutes a first step toward a comprehensive tool combining spatial, quantitative, and qualitative analysis of exposures. It underlines the need for complementary approaches such as field surveys, biomonitoring, and interactive mapping, to better address environmental poly-exposure in research on the clustering of pediatric cancers.