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Clinical Effects of Pollution
Published in William J. Rea, Kalpana D. Patel, Reversibility of Chronic Disease and Hypersensitivity, Volume 5, 2017
William J. Rea, Kalpana D. Patel
An important feature of the lateral olfactory area is that many signal pathways from this area also feed directly into an older part of the cerebral cortex called the paleocortex in the anteromedial portion of the temporal lobe. This is the only area of the entire cerebral cortex where sensory signals pass directly to the cortex without passing first through the thalamus.
PM2.5 exposure and olfactory functions
Published in International Journal of Environmental Health Research, 2022
John Andersson, Anna Oudin, Steven Nordin, Bertil Forsberg, Maria Nordin
One important component of pollution is particle matter (PM), which has been associated with negative cognitive outcomes (Ailshire and Crimmins 2014) and increased risk of dementia (Fu and Young 2020). Ultrafine particles (UFPM) (particles with a diameter less than 0.1 μm) can reach the brain, activate the immune system and thereby cause small inflammations. If the inflammations become chronic, they can result in neuronal death (Meraz-Rios et al. 2013). Several pathways through which UFPM can affect the brain have been proposed. These pathways are not mutually exclusive, and it is not clear which one is the most important. One is a systemic pathway (Block and Calderon-Garcidueñas 2009), in which UFPM cause inflammations in the body, which raises the levels of cytokines in the blood stream. These cytokines transfer the inflammation to the brain via the circulatory system. Another suggested pathway involves UFPM reaching the CNS by entering the blood stream via the lungs, breaking the blood-brain barrier through various kinds of transport (Heusinkveld et al. 2016). A third pathway involves the olfactory system. Since the olfactory receptors are directly exposed to ambient air, olfactory functions are especially vulnerable to air pollution exposure. Experiments using rodents (Oberdörster et al. 2004), as well as postmortem examinations of canines (Calderon-Garcidueñas et al. 2002) and humans (Calderon-Garcidueñas et al. 2004, 2008) suggest that particulate matter can reach the brain directly via the olfactory system. As we breathe, the air along with any PM and pollutants in it comes into contact with the olfactory epithelium in the nasal cavity. These particles can bind to the olfactory neurons and via retrograde transport end up in the olfactory bulb in the paleocortex (Heusinkveld 2016).