| Summary: | In order to evaluate the toxicity of PM<sub>2.5</sub> in the Dushanzi area, PM<sub>2.5</sub> samples were collected from December 2015 to July 2016, and a plasmid DNA damage assessment method was used to analyze the variation in the oxidative damage ability and its relationship with sampling conditions and toxic components (polycyclic aromatic hydrocarbons, and heavy metals) loaded on the surface of PM<sub>2.5</sub>. The results showed that the TD<sub>30</sub> values (toxic dosage of PM<sub>2.5</sub> causing 30% of plasmid DNA damage) of both the whole samples and the water-soluble fractions were lower during the heating period (369 μg/mL and 536 μg/mL, respectively), but higher in the dust period and non-heating period (681 μg/mL and 498 μg/mL, respectively; and 804 μg/mL and 847 μg/mL, respectively). Studies on the effect of meteorological parameters showed an increasing trend in TD<sub>30</sub> values for the whole samples and the water-soluble fractions as relative humidity, temperature and wind speed decrease. TD<sub>30</sub> values for the whole samples and the water-soluble fractions were negatively correlated with Flu (r = −0.690,r = −0.668; <i>p</i> < 0.05), Flt (r =−0.671, r = −0.760; <i>p</i> < 0.05), BaP (r = −0.672, r = −0.725; <i>p</i> < 0.05), IcdP (r = −0.694, r = −0.740; <i>p</i> < 0.05), Pyr (r = −0.727, r = −0.768; <i>p</i> < 0.01) and BghiP (r = −0.874, r = −0.845; <i>p</i> < 0.01) during the heating period, while As (r = 0.792, r = 0.749; <i>p</i> < 0.05) and Sr (r = 0.776, r = 0.754; <i>p</i> < 0.05) during the dust period showed significant positive correlation. In addition, the TD<sub>30</sub> values of PM<sub>2.5</sub> collected during sand blowing weather was the highest (1458 μg/mL and 1750 μg/mL), while the average TD<sub>30</sub> value of PM<sub>2.5</sub> collected on hazy days were the lowest (419.8 μg/mL and 488.6 μg/mL). Particles collected on the first day after snowfall showed a lower oxidizing capacity (676 μg/mL and 1330 μg/mL). The characteristic TD<sub>30</sub> values combined with back trajectory analysis indicated that hazy days were heavily influenced by air masses originating from the southern continent and local emissions, whereas the sand blowing weather came from the north of the Taklimakan Desert.
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