The Epidemiological and Toxicological Intersection of Air Pollution and Dementia

Abstract Accumulating evidence indicates that exposure to air pollution can be strongly associated with the development of dementia. However, different components and species of air pollution have been found to have varying associations with incidence of dementia in exposed populations. Among the most broadly studied pollutants in this context are particulate matter (PM), nitrogen dioxide (NO 2 ), ozone (O 3 ), and sulfur dioxide (SO 2 ). Here, we offer a joint toxicological and epidemiological review of the association of each of these well-studied pollutants with dementia, as well as other less-studied pollutants, such as black carbon (BC) and metals (both independently potent components of PM), carbon monoxide (CO), and polyaromatic hydrocarbons (PAHs). Sources and properties of these pollutants are considered in tandem with studies regarding their epidemiological association with dementia and the possible biological basis of these associations. By considering this joint perspective, we identify the pollutants with the greatest association with dementia incidence. Further, we offer a classification of pathological mechanisms and subtypes of dementia associated with exposure to the aforementioned pollutants. Despite variance in exposure assessment, dementia diagnosis and follow-up, and source population, our qualitative review indicates exposure to air pollutants, especially PM 2.5 and NO 2 , is associated with increased risk and incidence of dementia. Increasing evidence shows exposure to specific pollutants is tied to pathological mechanisms and dementia subtypes, as summarized here.