Particularly in rural settings, there has been little research regarding the health impacts of fine particulate matter (PM_2.5) during the wildfire season smoke exposure period on respiratory diseases, such as influenza, and their associated outbreaks months later. We examined the delayed effects of PM_2.5 concentrations for the short-lag (1-4 weeks prior) and the long-lag (during the prior wildfire season months) on the following winter influenza season in Montana, a mountainous state in the western United States. We created gridded maps of surface PM_2.5 for the state of Montana from 2009 to 2018 using spatial regression models fit with station observations and Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical thickness data. We used a seasonal quasi-Poisson model with generalized estimating equations to estimate weekly, county-specific, influenza counts for Montana, associated with delayed PM_2.5 concentration periods (short-lag and long-lag effects), adjusted for temperature and seasonal trend. We did not detect an acute, short-lag PM_2.5 effect nor short-lag temperature effect on influenza in Montana. Higher daily average PM_2.5 concentrations during the wildfire season was positively associated with increased influenza in the following winter influenza season (expected 16% or 22% increase in influenza rate per 1 μg/m³ increase in average daily summer PM_2.5 based on two analyses, p = 0.04 or 0.008). This is one of the first observations of a relationship between PM_2.5 during wildfire season and influenza months later.

Introduction: Growing evidence implicates air pollution as a risk factor for dementia, but prior work is limited by challenges in diagnostic accuracy and assessing exposures in the decades prior to disease development. We evaluated the impact of long‐term fine particulate matter (PM_2.5) exposures on incident dementia (all‐cause, Alzheimer's disease [AD], and vascular dementia [VaD]) in older adults.Methods: A panel of neurologists adjudicated dementia cases based on extensive neuropsychological testing and magnetic resonance imaging. We applied validated fine‐scale air pollutant models to reconstructed residential histories to assess exposures.Results: An interquartile range increase in 20‐year PM_2.5 was associated with a 20% higher risk of dementia (95% confidence interval [CI]: 5%, 37%) and an increased risk of mixed VaD/AD but not AD alone.Discussion: Our findings suggest that air pollutant exposures over decades contribute to dementia and that effects of current exposures may be experienced years into the future.