Particulate
matter (PM) presents an environmental health risk for
communities residing close to uranium (U) mine sites. However, the
role of the particulate form of U on its cellular toxicity is still
poorly understood. Here, we investigated the cellular uptake and toxicity
of C-rich U-bearing particles as a model organic particulate containing
uranyl citrate over a range of environmentally relevant concentrations
of U (0–445 μM). The cytotoxicity of C-rich U-bearing
particles in human epithelial cells (A549) was U-dose-dependent. No
cytotoxic effects were detected with soluble U doses. Carbon-rich
U-bearing particles with a wide size distribution (<10 μm)
presented 2.7 times higher U uptake into cells than the particles
with a narrow size distribution (<1 μm) at 100 μM U
concentration. TEM-EDS analysis identified the intracellular translocation
of clusters of C-rich U-bearing particles. The accumulation of C-rich
U-bearing particles induced DNA damage and cytotoxicity as indicated
by the increased phosphorylation of the histone H2AX and cell death,
respectively. These findings reveal the toxicity of the particulate
form of U under environmentally relevant heterogeneous size distributions.
Our study opens new avenues for future investigations on the health
impacts resulting from environmental exposures to the particulate
form of U near mine sites.
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