Detection of Ambient Black Carbon in Conjunctival Sac Washed Fluid Reveals the Ocular Exposure Risks of Particulate Pollution

Ambient ultrafine particles have been identified in thehuman body,raising serious concerns about the systemic health risks of air particulatepollution. While eyes constantly and directly contact airborne particulatematter, the associated ocular surface health risks are often overlooked.Here, we developed a laser desorption/ionization mass spectrometryimaging method to identify and detect ambient black carbon particles,a typical component of PM2.5, in conjunctival sac washedfluid samples. We have detected black carbon particles in 24 of 55samples (selected from 656 patients), with concentrations rangingfrom 0.31 to 5.1 & mu;g/mL (mean value of 0.95 & mu;g/mL). Thepresence of black carbon particles at the ocular surface was influencedby daily life habits. Moreover, it is associated with some ocularindices and dry eye disease, indicating potential ocular health risks.As this is the first report about the high-frequency presence of blackcarbon at the human ocular surface, our findings not only demonstrateblack carbon as a potential marker of airborne particulates on theocular surface but also provide evidence for a neglected but importantaspect of health impacts associated with PM2.5 exposure.