Exposure to ambient levels of urban air pollution elicits inflammatory response in human olfactory bulb

There is increasing recognition in the literature that air pollution threatens brain health across lifespan. Effects range from neurodevelopment problems in early life to neurodegenerative diseases later in life. Experimental studies corroborate the findings in humans. However, the mechanisms by which tiny particles reach the central nervous system (CNS) and cause disease have not yet been fully elucidated. Formed by the incomplete combustion of fossil fuels, Black Carbon (BC) is a major component of particulate matter (PM). In this descriptive autopsy-based study, we used a two-photon label-free microscopy to identify in situ, the presence of black carbon particles in the human olfactory bulb. We adapted the previous methodology to ensure that what we visualize are solely black carbon particles, for this, we included a verification step to avoid overestimating the number of particles. We detected BC particles in the human olfactory bulb. In addition, BC is associated with microglial activation at microscopic level. Additionally, we showed that lifetime exposure to air pollution (BC) measured directly in the lungs of the deceased (pleural anthracosis) alters gene expression in the olfactory bulb. In conclusion, our study provided additional evidence to support the concept that exposure to particulate air pollution causes detectable alterations in the central nervous system.