Abstract
This review presents MALDI mass spectrometry imaging (MALDI-MSI) as a label-free technique that maps emerging contaminants inside biological samples and shows where they accumulate in organisms. This spatial information is essential in a One Health context, as pollutants such as pharmaceuticals, pesticides, PFAS, and micro- and nanoplastics can appear at low environmental levels but concentrate on specific tissues, increasing ecological and health risks. Unlike LC/GC-MS, which provides average concentrations after homogenization, MALDI-MSI preserves tissue structure and links contaminants with local biological responses. Applications in plants, aquatic organisms, invertebrates, and human tissues are summarized. Current limitations, including matrix interference, ion suppression, and quantification challenges, are discussed together with future perspectives such as 3D imaging, MALDI-2, ion mobility, and semi-mobile monitoring approaches.