Atmospheric Particulate Matter as a Carrier of Pb, Cd, and Ni: From Environmental Transfer and Bioaccessibility to Molecular Toxicity and Predictive Modeling.

Atmospheric particulate matter (PM) is a heterogeneous carrier of toxic metals whose environmental fate and biological effects depend on particle size, source-related composition, chemical form, solubility, and bioaccessibility. Lead (Pb), cadmium (Cd), and nickel (Ni) are of particular concern because atmospheric transport and deposition connect air pollution with persistent contamination of soils, vegetation, waters, sediments, food, and feed, followed by human and animal exposure. This review integrates evidence across a source-to-effect continuum encompassing emission, atmospheric transport, deposition, post-depositional redistribution, food-chain transfer, bioaccessibility, toxicokinetics, molecular toxicity, biomonitoring, remediation, and predictive assessment. Total PM mass and total metal concentration do not adequately represent biologically effective exposure, which is additionally determined by respiratory deposition, gastrointestinal release, dissolution kinetics, absorption, tissue distribution, intracellular retention, and interactions with co-associated constituents. Pb, Cd, and Ni share downstream effects including oxidative imbalance, inflammation, mitochondrial dysfunction, DNA damage, impaired genome maintenance, epigenetic remodeling, and cytogenetic abnormalities, but differ in environmental mobility, persistence, target-organ distribution, and molecular mechanisms. Effective risk assessment therefore requires coordinated multi-matrix monitoring, distinction between total and biologically accessible fractions, pathway-specific remediation, and appropriately validated predictive models. An integrated One Health framework can improve identification of priority matrices, exposure pathways, and risk-reduction measures.