Relationship between long-term exposure to sources of particulate matter, ambient air pollution and cognitive function in older adults

Long-term exposure to particulate matter with a diameter of less than 2.5 μm (PM2.5) is associated with cognitive decline, but it is not clear whether the potential effects of PM2.5 from different emission sources vary. This study aims to assess the association between PM2.5 from different emission sources and cognitive function in older adults in Northern Ireland. Using data of the Northern Ireland Cohort of Longitudinal Ageing from wave 1 (n = 3440) and wave 2 (n = 5408). Long-term exposure to PM2.5 (5-year and 10-year average) was estimated using the UK Pollution Mapping approach within the 1-km residential circular buffers, while PM2.5 source fraction was calculated using the atmospheric chemistry-transport model. Cognitive function was assessed using the Mini-Mental State Examination (MMSE) scores. The association between PM2.5 and MMSE scores was estimated using multilevel linear regression models, and the Quantile-based g-computation approach was employed to decompose the potential effect of different emission sources of PM2.5. The 5-year average PM2.5 levels were negatively associated with MMSE scores (coef. = −0.07; SE = 0.02), with no evidence of association with 10-year average levels (coef. = −0.05; SE = 0.02). Furthermore, 5-year average PM2.5 from agriculture, wildfires and road traffic were negatively associated with MMSE scores, while 10-year average PM2.5 from agriculture was also negatively associated with MMSE outcomes. Moreover, industry and agricultural sources provide the greatest contributions to the potential effect of PM2.5. Long-term exposure to PM2.5, especially from agricultural, road traffic, and wildfire, may be harmful to cognition. Therefore, policy should aim to regulate emissions from high-risk sources.