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The delayed effect of wildfire season particulate matter on subsequent influenza season in a mountain west region of the USA.

ABSTRACT: 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.

SUBMITTER: Landguth EL

PROVIDER: S-EPMC7275907 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:AimDrastic changes in fire regimes are altering plant communities, inspiring ecologists to better understand the relationship between fire and plant species diversity. We examined the impact of a 90,000-ha wildfire on woody plant species diversity in an arid mountain range in southern Arizona, USA. We tested recent fire-diversity hypotheses by addressing the impacts on diversity of fire severity, fire variability, historical fire regimes, and topography.LocationChiricahua National Monument, Chiricahua Mountains, Arizona, USA, part of the Sky Islands of the US-Mexico borderlands.TaxonWoody plant species.MethodsWe sampled woody plant diversity in 138 plots before (2002-2003) and after (2017-2018) the 2011 Horseshoe Two Fire in three vegetation types and across fire severity and topographic gradients. We calculated gamma, alpha, and beta diversity and examined changes over time in burned versus unburned plots and the shapes of the relationships of diversity with fire severity and topography.ResultsAlpha species richness declined, and beta and gamma diversity increased in burned but not unburned plots. Fire-induced enhancement of gamma diversity was confined to low fire severity plots. Alpha diversity did not exhibit a clear continuous relationship with fire severity. Beta diversity was enhanced by variation in fire severity among plots and increased with fire severity up to very high severity, where it declined slightly.Main conclusionsThe results reject the intermediate disturbance hypothesis for alpha diversity but weakly support it for gamma diversity. Spatial variation in fire severity promoted variation among plant assemblages, supporting the pyrodiversity hypothesis. Long-term drought probably amplified fire-driven diversity changes. Despite the apparent benign impact of the fire on diversity, the replacement of two large conifer species with a suite of drought-tolerant shrubs signals the potential loss of functional diversity, a pattern that may warrant restoration efforts to retain these important compositional elements.

Project description:BACKGROUND:The effects of exposure to fine particulate matter ([Formula: see text]) during wildland fires are not well understood in comparison with [Formula: see text] exposures from other sources. OBJECTIVES:We examined the cardiopulmonary effects of short-term exposure to [Formula: see text] on smoke days in the United States to evaluate whether health effects are consistent with those during non-smoke days. METHODS:We examined cardiopulmonary hospitalizations among adults [Formula: see text] y of age, in U.S. counties ([Formula: see text]) within [Formula: see text] of 123 large wildfires during 2008-2010. We evaluated associations during smoke and non-smoke days and examined variability with respect to modeled and observed exposure metrics. Poisson regression was used to estimate county-specific effects at lag days 0-6 (L0-6), adjusted for day of week, temperature, humidity, and seasonal trend. We used meta-analyses to combine county-specific effects and estimate overall percentage differences in hospitalizations expressed per [Formula: see text] increase in [Formula: see text]. RESULTS:Exposure to [Formula: see text], on all days and locations, was associated with increased hospitalizations on smoke and non-smoke days using modeled exposure metrics. The estimated effects persisted across multiple lags, with a percentage increase of 1.08% [95% confidence interval (CI): 0.28, 1.89] on smoke days and 0.67% (95% CI: [Formula: see text], 1.44) on non-smoke days for respiratory and 0.61% (95% CI: 0.09, 1.14) on smoke days and 0.69% (95% CI: 0.19, 1.2) on non-smoke days for cardiovascular outcomes on L1. For asthma-related hospitalizations, the percentage increase was greater on smoke days [6.9% (95% CI: 3.71, 10.11)] than non-smoke days [1.34% (95% CI: [Formula: see text], 3.77)] on L1. CONCLUSIONS:The increased risk of [Formula: see text]-related cardiopulmonary hospitalizations was similar on smoke and non-smoke days across multiple lags and exposure metrics, whereas risk for asthma-related hospitalizations was higher during smoke days. https://doi.org/10.1289/EHP3860.

Project description:BackgroundEmissions from a large peat fire in North Carolina in 2008 were associated with increased hospital admissions for asthma and the rate of heart failure in the exposed population. Peat fires often produce larger amounts of smoke and last longer than forest fires, however few studies have reported on their toxicity. Moreover, reliable alternatives to traditional animal toxicity testing are needed to reduce the number of animals required for hazard identification and risk assessments.MethodsSize-fractionated particulate matter (PM; ultrafine, fine, and coarse) were obtained from the peat fire while smoldering (ENCF-1) or when nearly extinguished (ENCF-4). Extracted samples were analyzed for chemical constituents and endotoxin content. Female CD-1 mice were exposed via oropharyngeal aspiration to 100 ?g/mouse, and assessed for relative changes in lung and systemic markers of injury and inflammation. At 24 h post-exposure, hearts were removed for ex vivo functional assessments and ischemic challenge. Lastly, 8 mm diameter lung slices from CD-1 mice were exposed (11 ?g)?±?co-treatment of PM with polymyxin B (PMB), an endotoxin-binding compound.ResultsOn an equi-mass basis, coarse ENCF-1 PM had the highest endotoxin content and elicited the greatest pro-inflammatory responses in the mice including: increases in bronchoalveolar lavage fluid protein, cytokines (IL-6, TNF-?, and MIP-2), neutrophils and intracellular reactive oxygen species (ROS) production. Exposure to fine or ultrafine particles from either period failed to elicit significant lung or systemic effects. In contrast, mice exposed to ENCF-1 ultrafine PM developed significantly decreased cardiac function and greater post-ischemia-associated myocardial infarction. Finally, similar exposures to mouse lung slices induced comparable patterns of cytokine production; and these responses were significantly attenuated by PMB.ConclusionsThe findings suggest that exposure to coarse PM collected during a peat fire causes greater lung inflammation in association with endotoxin and ROS, whereas the ultrafine PM preferentially affected cardiac responses. In addition, lung tissue slices were shown to be a predictive, alternative assay to assess pro-inflammatory effects of PM of differing size and composition. Importantly, these toxicological findings were consistent with the cardiopulmonary health effects noted in epidemiologic reports from exposed populations.

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The delayed effect of wildfire season particulate matter on subsequent influenza season in a mountain west region of the USA.

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