No abstract

In this study, we explored the effects of particulate matter 2.5 (PM2.5) eye drops on the ocular surface structure and tear function in mice and established a novel animal model for dry eye research. We found that, following treatment with PM2.5, the tear volume and, the tear film break-up time showed statistical differences at each time point (P < 0.05). The FL score of the PM2.5-treated group was higher than that of others (P < 0.05). The average number of corneal epithelial layer cells in groups A and B was significantly lower than that in group C (P < 0.05). Scanning electron microscopy and transmission electron microscopy revealed that the number of corneal epithelial microvilli and corneal desmosomes was drastically reduced in group C. PM2.5 induced apoptosis in the corneal superficial and basal epithelium and led to abnormal differentiation and proliferation of the ocular surface with higher expression levels of Ki67 and a reduced number of goblet cells in the conjunctival fornix in group C. PM2.5 significantly increased the levels of TNF-α, NF-κB p65 (phospho S536), and NF-κB in the cornea. Thus, the topical administration of PM2.5 in mice induces ocular surface changes that are similar to those of dry eye in humans, representing a novel model of dry eye.

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The high concentration of K + in PM 2.5 (4.41 µg m −3 ) and its good correlation with black carbon (r = 0.90) and oxalic acid (r = 0.87) suggested the severe pollution from biomass burning, which was proved to be a main source of fine particles over central eastern China in summer. The contribution of biomass burning to the fine particle at MT accounted for 7.56 % in spring and 36.71 % in summer, and even reached to 81.58 % on a day. As and Pb were two of the most enriched elements. The long-range transport of aerosols spread the heavy pollution from coal-mining/coal-ash to everywhere over China. Anthropogenic air-pollution was evidently rather severe at MT, though it has been declared by UNESCO to be a World Heritage site.

Daily particulate matter with particles less than 2.5 μm in aerodynamic diameter (PM2.5) and total suspended particulates (TSP) were analyzed for chemical composition and daily PM10, SO2, and NO2 were monitored by automatic monitoring systems on the seven sites over China along the pathway of the long‐range transport of the dust from 20 March to 19 April 2007. The highest recorded dust and daily Air Pollution Index topped 500 for the first time since 2002, when the routine continuous monitoring of PM10 was initiated in Shanghai. The daily 24 h average PM10 concentration of 648 μg m−3 was observed on 2 April 2007. The ratios of SO2/PM10, NO2/PM10, and PM2.5/PM10 were 0.066, 0.077, and 15.5% on 2 April 2007, which were significantly different from the nondust day and could be used as the index to judge the occurrence of dust in Shanghai. On the peak dusty day, the ratios of crustal matter rose to 70% and 64% of the total mass of PM2.5 and TSP, respectively, while the ratios were 13% and 37% on nondust days. The ratio of Ca/Al in the dust aerosol in Shanghai was much closer to that in Duolun and Yulin near Mongolia Gobi rather than that in Tazhong of Taklimakan desert, indicating that the dust was transported from Mongolia Gobi instead of Taklimakan desert in Xinjiang province. The compositions of sea salt aerosol in PM2.5 and TSP, combined with back trajectories, indicated that the dust passed through the East China Seas before reaching Shanghai, which is one of the typical dust pathways that lead to heavily polluted days in Shanghai due to dust transport. The anthropogenic sources along the pathway also partially contributed to the PM pollution in Shanghai during this dust event.