Climate-extreme soil exposome: how drought converts contaminated agricultural soils into one-health risk hotspots

Contaminated agricultural soils are conventionally treated as static pollutant repositories whose hazard state is adequately captured by total contaminant concentration, an assumption that intensifying drought regimes are rendering untenable. This review advances the concept of a climate-sensitive soil exposome, in which drought functions as a hydro-biogeochemical driver that reorganizes the bioavailability, speciation, and biological accessibility of metals, antibiotics, pesticides, per- and polyfluoroalkyl substances, and microplastics without altering their total soil inventories. By reducing porewater connectivity, concentrating solutes within disconnected microsites, and expanding the air-water interfacial area, drought can modify the spatial co-localization and interactions among pollutant classes whose mixture-level exposure potential cannot be predicted from single-contaminant assessments. At the same time, drought imposes ecological filtering on soil microbial communities, selectively enriching stress-tolerant, biofilm-forming, and resistance-bearing taxa that, in soils co-contaminated with persistent metals and antibiotic residues, disproportionately expand antibiotic resistance genes and mobile genetic elements. Global evidence now associates aridity with elevated hospital-level antibiotic resistance rates (i.e., the frequency of resistant clinical isolates recorded in hospital surveillance data) across 116 countries, implicating climate-driven soil microbial filtering in public health consequences extending far beyond field boundaries. Drying-rewetting cycles emerge as periods of potentially elevated exposure, generating acute pulses of contaminants, resistant microorganisms, and resistance genes through crop uptake, contaminated dust inhalation, and post-drought hydrological export pathways that static, concentration-anchored monitoring frameworks may not fully capture. Future risk assessment should consider drought-rewetting transitions as primary sampling targets, adopt bioavailability-resolved and mixture-sensitive monitoring, and explicitly incorporate contaminated agricultural dust as a critically undercharacterized inhalation exposure route, prioritizing it as a research frontier in climate-sensitive soil exposome science.