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1.3. Chronic illness processes start when the total exposome load exceeds the host tolerance

The risk of developing an acute disease rises when a threat, either a virus, bacteria, fungus, or environmental toxin, is exposed at high doses. Clinical COVID-19 was caused by exposure to virulent virus strains like SARS-CoV2 during recent pandemics. Pesticide consumption at high doses results in death. Therefore, an acute clinical illness is probably caused by a large dose of a particular exposome.

Low-dose exposure activates adaptive mechanisms to deal with the subsequent tissue damage from one or more exposomes, even though no clinical symptoms are present at the time. These hormesis processes enable hosts to maintain their health while building up their resistance to potential threats. However, when host damage-control limits are surpassed, these pathophysiologic consequences cumulate the processes of chronic illnesses. The risk of metabolic and cardiovascular problems rises in humans staying in an air environment with high PM 2.5, despite the absence of acute respiratory symptoms. Additionally, whereas a single exposome can induce a variety of chronic diseases, a chronic illness entity may be caused by multiple exposomes.

Therefore, the modern-day prevalence of chronic diseases is influenced by total exposome load, host tolerance, and vulnerability.

Oskar Karlsson, Joacim Rocklöv, Alizée P Lehoux, Jonas Bergquist, Anna Rutgersson, Martin J Blunt, Linda S Birnbaum, The human exposome and health in the Anthropocene, International Journal of Epidemiology, Volume 50, Issue 2, April 2021, Pages 378–389,

Rui Martins, Ana Rita Carlos, Faouzi Braza, Jessica A. Thompson, Patricia Bastos-Amador, Susana Ramos, Miguel P. Soares, Disease Tolerance as an Inherent Component of Immunity, Annual Review of Immunology 2019 37:1, 405-437

Zhang, P.; Arora, M.; Chaleckis, R.; Isobe, T.; Jain, M.; Meister, I.; Melén, E.; Perzanowski, M.; Torta, F.; Wenk, M.R.; Wheelock, C.E. Tackling the Complexity of the Exposome: Considerations from the Gunma University Initiative for Advanced Research (GIAR) Exposome Symposium. Metabolites 2019, 9, 106.

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