Worldwide, outdoor air pollution is responsible for 4.2 million premature deaths per year. Both chronic and acute exposure to particulate matter air pollution is a risk factor for heart and lung diseases. One of the atmospheric pollutant particles is represented by soot or carbonaceous particles (CPs), which are produced during the incomplete combustion of fuels. To evaluate human CP exposure, a direct and label-free approach for detecting such particles in body fluids and tissues was still lacking. We present a novel technique to finally close the diagnostic gap. We report for the first time white-light generation by CPs under femtosecond pulsed near-infrared light illumination in aqueous environments and demonstrate the potential of this approach in biomedical and diagnostic context. In fact, it was shown that urinary carbon loading can serve as an exposure matrix to carbon-based air pollution, reflecting the passage of soot particles from circulation into urine. The novel method is straightforward, fast and flexible without the need of sample pretreatment. Moreover, the technique offers several other advantages such as inherent 3D sectioning and high imaging depths making it possible to screen at the cellular and tissue level. In conclusion, this novel diagnostic technique allows to quantify exposure at the personal level including different scenarios like occupational exposure, smog, forest fires, etc.. Additionally, this approach paves the way to unravel the complexity of soot-related health effects.
The adverse health effects of particulate matter exposure are a generally accepted concern. Dramatic statistical figures suggest that fine dust is a main environmental risk in Europe and can be held accountable for hundreds of thousands of deaths per year . Locating and tracking these nanometer sized particles, however, is not straight forward: In epidemiological and toxicology research only measurements based on labels  such as radionuclide markers have been applied.
In this paper we present a direct, label-free optical contrast mechanism to detect carbon nanoparticles immersed in aqueous environments . The virtue of this technique is its ability to perform in body fluids such as urine but also in cells and tissues. The mechanism is based on white light (WL) generation upon illumination with femtosecond pulsed near-infrared and is therefore non-incandescence related. We demonstrate the technique in various biological settings with dry and suspended carbon black particles (CB), a widely used model compound for soot . Our approach allows for the unequivocal localization of CB alongside of common fluorophores and markers and can be performed on multiphoton laser-scanning microscopy platforms, a system commonly available in research laboratories.
 European Environment Agency (2015). Press release.
 Kong et al. Int. J. Mol. Sci. 2013, 14, (11), 22529-22543
 Bové and Steuwe et al. Nano letters, 2016, (16) , pages 3173-3178
 Arnal et al. Combust. Sci. Technol. 2012, 184, (7-8), 1191-1206.