Wildfire smoke impacts respiratory health more than fine particles from other sources: observational evidence from Southern California

Asthma medication usage after environmental exposure to wildfire smoke: A systematic review

Asthma is a chronic respiratory condition exacerbated by exposure to particulate air pollution. Smoke from landscape fires has been associated with increased mortality, asthma-related admissions to emergency and other hospital departments, and uptake in primary care services. With climate change and more frequent landscape fires, healthcare systems must prepare for disaster, including surges in asthma medication demand. Past reviews have not resolved the direction and magnitude of the association between PM2.5 exposure during landscape fires and asthma medication use. The aim of this review was to investigate the relationship between exposure to landscape fire smoke and the use of asthma medications. We conducted a systematic review of PubMed, Scopus, and Web of Science, identifying peer-reviewed articles that examined asthma medication usage following environmental exposure to landscape fire smoke. After a full-text review, we identified twelve articles, three from Canada, three from the USA and six from Australia, with five being retrospective cohort studies. Despite differences in study design, outcome and exposure assessment, the included studies reported a consistent increase in asthma medication use after exposure to wildfires. There is consistent evidence that exposure to wildfire smoke is associated with an increase in the use of reliever medications, particularly salbutamol. Increases in other asthma management medications were also consistently identified. Increases in demand for asthma medications after exposure to wildfire smoke highlight the urgent need to address the growing frequency and intensity of wildfires driven by climate change.

Evaluating public exposure to airborne particulates from major incident fires: A back trajectory plume modelling approach

Major incident fires at industrial facilities, particularly waste sites, pose a significant risk to public health because of the large amounts of hazardous airborne pollutants released into the ambient environment. Monitoring carried out during these fires is limited in spatial resolution, meaning that the full extent of population exposure is difficult to estimate. In this study, we overcome these limitations by using a novel back-trajectory plume modelling approach, applied to PM10 emission data from a significant tyre fire that occurred in the UK in 2010. This approach allows the calculation of an hourly emission rate that is then used in the forward modelling mode to predict hourly plume concentrations. An analysis of the modelled plume indicated that, as a reasonable worst case, up to 8000 residents in areas adjacent to the fire may have been exposed to PM10 concentrations that are deemed hazardous. Moreover, a vulnerability analysis showed that the exposed population had disproportionately poorer health than the national average, thus raising concerns about environmental justice. This work highlights the need to improve regulatory controls for waste sites located near urban areas and for further research on population exposure and the health impacts of major incident fires.

Compound drought and heatwave extreme weather events: Mortality risk in individuals with chronic respiratory disease

Background

Compound extreme weather events are severe weather conditions that can jointly magnify human health risks beyond any single event alone. Drought and heatwaves are extreme weather conditions associated with adverse health, but their combined impact is poorly understood.

Methods

We designed a case-crossover study to estimate heatwave-associated mortality stratified by drought conditions in 183,725 US Veteran patients (2016-2021) with chronic obstructive pulmonary disease (COPD). A conditional logistic regression with distributed lag models was applied. Droughts were categorized into binary and categorical metrics, and we further explored the timing of heatwaves as a risk factor.

Results

Our results indicate that drought amplifies heatwaves with hotter temperatures and longer durations during drought conditions, and the percentage of mortality attributable to heatwaves during drought was 7.41% (95% confidence interval [CI]: 2.91, 12.28) compared with 2.91% (95% CI: 0.00, 4.76) for heatwaves during nondrought conditions. Heatwaves that occurred during drought conditions in the late warm season had a larger association with mortality compared with late-season heatwaves during nondrought conditions, 7.41% (95% CI: 1.96, 13.04) of mortality events and 0.99% (95% CI: -1.01, 3.85) of mortality events attributable to these exposures, respectively.

Conclusion

Compound drought and heatwave events trend toward increased mortality risk among patients with COPD and present a growing human health threat under climate change. Existing heat warnings and vulnerability maps may include drought conditions to better capture heat-related public health risks.

Analysis of Pediatric Acute Upper Airway Pathology During Local Wildfires and Increased PM 2.5 Burden

OBJECTIVE

As wildfires worldwide increase in severity and frequency, fine particulate matter (PM 2.5), generated as a component of wildfire smoke, increasingly impacts air quality. Children are particularly vulnerable to poor air quality in numerous ways, including inhalation of more air in proportion to their body size than adults. Though its adverse impacts on the lower airway are well demonstrated, the clinical effects of PM 2.5 on the pediatric upper airway are poorly understood and warrant investigation.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary academic medical center.

METHODS

From 2014 to 2023, patient presentations to a pediatric emergency department in Northern California during exposure periods of elevated PM 2.5 burden associated with nearby wildfires were identified. Patient diagnoses, presenting symptoms, and management were analyzed. Comparison group patients were evaluated during date-matched control periods with confirmed normal air quality. Chi-squared analyses determined significance.

RESULTS

During periods of increased wildfire-generated PM 2.5 burden, a significantly greater proportion of pediatric patients presented to the emergency department with upper airway pathology compared to matched control periods of healthy air quality. Further, a significantly greater proportion of patients were diagnosed with croup during wildfires. Of patients presenting with upper airway pathology, a significantly greater proportion experienced dysphonia during wildfires and had a negative strep test.

CONCLUSION

Wildfire-generated PM 2.5 may contribute to increased rates of croup presentations, and PM 2.5 may disproportionately affect the larynx in the pediatric upper airway. Larger population-based studies and preclinical models may clarify these clinical manifestations of a growing public health threat.

Aqueous Oxidation of Biomass-Burning Furans by Singlet Molecular Oxygen (1O2*)

Furans are abundant emissions from biomass burning that can react with gas-phase oxidants to produce secondary organic aerosol (SOA). Furans might also react with aqueous photooxidants, such as singlet molecular oxygen (1O2*), to form aqueous SOA (aqSOA), but this has not been studied. To investigate the aqueous reactivities of furans and their potential to make low-volatility products, we first measured the reaction kinetics for singlet oxygen with 17 furans. The resulting second-order rate constants vary widely with chemical substitution, ranging from 105 to nearly 109 M-1 s-1. Inorganic salts can decrease or enhance the first-order loss of furans by singlet oxygen. To investigate whether furan-1O2* reactions might produce particulate matter, we measured SOA mass yields for three furans: furoic acid, furfuryl alcohol, and 2-methylfuran-3,4-dicarboxylic acid (MFDCA). The resulting mass yields span a huge range, with values of ∼0, 51, and 125%, respectively. Finally, we estimated rates of gas- and aqueous-SOA formation from reactions of MFDCA over a range of conditions, from cloud and fog drops to aerosol liquid water. Results suggest that aqueous reactions of highly substituted furans with 1O2* could be a significant source of aqSOA in biomass-burning plumes but that aqueous reactions of triplet excited states with phenols are more important.

Wildfire-Related Air Pollution and Infectious Diseases: Systematic Review and Meta-Analysis

Amid the global rise in wildfire events, the health impacts of wildfire-related air pollution are increasingly scrutinized. While numerous reviews have examined the link between air pollution and infectious diseases, reviews specifically focusing on wildfire-related air pollution and infectious diseases remain scarce. To address this gap, we conducted a comprehensive search in MEDLINE, EMBASE, Scopus and Web of Science databases up to December 31, 2023, using PRISMA (Preferred Reporting Items for Systematic Reviews & Meta-Analyses) guidelines. Search terms included synonyms of wildfire and infectious diseases. Peer-reviewed epidemiological studies that reported any association or trend between wildfire air pollution and infectious diseases were selected against eligibility criteria. Risk of bias and quality of included studies were assessed using modified risk of bias and quality assessment tools. Our review included 30 studies, predominantly from developed countries including the United States (USA), Australia, and Canada. Most focused on respiratory infectious diseases (n = 29), including 9 specifically on the coronavirus disease 2019 (COVID-19). The majority examined short-term wildfire air pollution (n = 27) (exposure of one month or less). Twenty-three studies reported effect estimates for the meta-analysis. We found that a 10 μg/m3 increase in short-term wildfire PM2.5 (particulate matter with a diameter of 2.5 micrometer of less) exposure was associated with a 15% increase in COVID-19 infections (relative risk [RR] = 1.15; 95% confidence interval [CI]: 1.09-1.21; heterogeneity (I 2): 83%), a 3% increase in respiratory diseases (RR = 1.03; 95% CI: 1.01-1.05; I 2: 0%) and a 3% increase in acute upper respiratory infection combined with acute bronchitis (RR = 1.03; 95% CI: 1.02-1.05; I 2: 62%). Medium-term exposure (more than a month but less than a year) to wildfire smoke was associated with 20% rising hospitalization for systemic fungal infections like coccidioidomycosis (95% CI: 5-38%). The current research exclusively examines respiratory infections in developed countries. Future high-quality primary studies should prioritize understanding the impact of wildfire-related air pollution on various infectious diseases.

Global disparities in indoor wildfire-PM2.5 exposure and mitigation costs

Wildfires have become more frequent and severe, and evidence showed that exposure to wildfire-caused PM2.5 (fire-PM2.5) is associated with adverse health effects. Fire-PM2.5 exposure occurs mainly indoors, where people spend most of their time. As an effective and timely approach of mitigating indoor PM2.5 pollution, air purifiers incur notable associated costs. However, the long-term global population exposure to indoor fire-PM2.5 and the economic burden of using air purifiers remain unknown. Here, we estimated the indoor fire-PM2.5 concentration and the cost of reducing indoor PM2.5 exposure, along with the extra cost incurred because of fire-PM2.5, at a resolution of 0.5° by 0.5° globally during 2003 to 2022. Our findings revealed 1009 million individuals exposed to at least one substantial indoor wildfire-air pollution day per year. We identified pronounced socioeconomic disparities in the costs of mitigating indoor PM2.5 exposure, with low-income countries bearing a disproportionately higher economic burden, emphasizing the critical need for addressing these disparities.

The cost of clean air: Global disparities in reducing indoor wildfire-related PM2.5 exposure

Using air purifiers to reduce indoor exposure to wildfire-related PM2.5 is effective but costly, placing a disproportionately higher financial burden on low-income countries.

Associations of wildfire-derived particulate matter with hospitalization, emergency department visits and mortality: A systematic review and meta-analysis

Epidemiological studies on wildfire smoke exposure and its associated disease morbidities and mortalities are rapidly accumulating in recent years. However, the findings of the existing studies have not been quantitatively evaluated with a conclusion. We conducted a systematic review and meta-analysis for the studies focused on associations of wildfire-sourced particles (PM2.5 and PM10) with cardiorespiratory diseases and mortality. We reviewed all literatures related to wildfire particles (PM2.5 and PM10) and cardiorespiratory disease morbidities [hospital admission, emergency department (ED) visits] and mortality (all-cause and cause-specific) from January 1, 2000 to August 1, 2024. Meta-analyses were conducted to summarize Relative Risks (RRs) and 95% confidence intervals (CIs) across studies when at least three studies were available for a particular exposure-outcome. All articles were assessed for risk of bias using a standard tool (Grading of Recommendations Assessment, Development and Evaluation, GRADE) for quality assurance. Studies (N = 45) were increasingly published between the years of 2020-2024 and from North America (N = 21) and Australia (N = 11) where wildfires are common. In the meta-analysis of over 124 million patients, wildfire smoke was consistently associated with increased risk of all-cause mortality (RR: 1.02, 95% CI 1.01-1.03 for PM2.5 per 10 μg/m3) and respiratory outcomes, including hospital admission (1.04, 95% CI 1.02-1.05 for wildfire PM2.5 and 1.01, 95% CI 1.00-1.02 for wildfire PM10) and ED visits (1.04, 95% CI 1.02-1.06 for wildfire PM2.5). Associations between wildfire PM2.5 and cardiovascular diseases were inconclusive (mortality: 1.02, 95% CI 1.01-1.03; hospital admission: 1.01, 95% CI 1.00-1.02; ED visit: 1.01, 95%CI: 0.98-1.04). Current studies provide evidence of an increased risk of hospitalization and ED visits for respiratory diseases and all-cause mortality due to wildfire PM2.5 and PM10 exposures worldwide. Future research is needed to explore health effects of wildfire exposure on cardiovascular diseases.

Where There is Smoke: An Updated Review of Environmental Contributions to Chronic Rhinosinusitis

PURPOSE

The pathogenesis of chronic rhinosinusitis (CRS) is thought to include a complex interaction between environmental exposures and host immune responses that generates a self-perpetuating inflammatory process. As molecular pathways continue to be explored, the impact of environmental exposures on CRS pathogenesis and exacerbation must not be overlooked. This review will explore the association between environmental exposures and CRS, specifically focusing on tobacco smoke, occupational inhalational exposures, air pollution, particulate matter, and wildfire smoke.

MAJOR FINDINGS

Tobacco smoke is associated with increased prevalence of CRS symptoms and formal diagnosis with worse surgical outcomes observed in both adults and children exposed to tobacco smoke. Numerous occupational exposures have been associated with increased sinonasal symptoms, though exposures and disease definitions are often poorly characterized. Pollution and microparticle exposure has been associated with an increased likelihood of CRS diagnosis, as well as increased need for surgery. Last, while wildfire smoke has been attributed to increased hospital and emergency room visits for respiratory-related complaints, no primary research has yet been performed regarding CRS and wildfire smoke, though in-vitro studies support an association.

CONCLUSIONS

Population-based studies bolstered by in-vitro mechanistic data support an association between numerous environmental exposures and the onset and severity of CRS.

Impact of the 2023 wildfire smoke episodes in Ontario, Canada, on asthma and other health outcomes: an interrupted time-series analysis

BACKGROUND

During the 2023 wildfire season, Ontario, Canada, had unprecedented wildfire smoke, but the health impact on the population is unknown. We aimed to quantify the acute impact of the wildfire smoke on respiratory and cardiovascular outcomes across Ontario.

METHODS

We conducted a quasi-experimental study by leveraging the timing of 2 consecutive wildfire smoke episodes in June 2023. Heavy wildfire smoke blanketed much of Ontario on 2 occasions, in early June and again in late June, causing severely degraded daily air quality. Following the epidemiologic triangulation framework, we collected health data on emergency department visits for 4 outcomes (asthma-related causes, other respiratory causes, ischemic heart disease, and non-cardiorespiratory causes) from Ontario's real-time syndromic surveillance system and the National Ambulatory Care Reporting System. We also employed different epidemiologic methodologies, including interrupted time-series and case-crossover analyses.

RESULTS

After the initial heavy wildfire smoke in early June 2023, daily asthma-related visits increased substantially across Ontario, peaking at a 23.6% increase (95% confidence interval 13.2%-34.9%) at a 1-day lag and lasting up to a lag of 5 days after the start of the smoke episode. The later episode of heavy smoke, despite causing higher exposures, had a reduced effect on asthma-related visits. We did not detect any effect on other outcomes in either episode. These findings were consistent across different methodologies and data sources. Post hoc analysis revealed that asthma-related visits were briefly elevated after the wildfire smoke among children (40% higher), but we observed a more sustained effect among adults (48% higher, lasting 1 week).

INTERPRETATION

The 2023 wildfires substantially increased asthma-related emergency department visits in Ontario, with age and timing of exposure being important factors influencing the impact. As wildfires emerge as one of the fastest-growing environmental risk factors globally, future research should identify and evaluate measures to effectively mitigate the acute health impacts of wildfire smoke.

Anthropogenic climate change contributes to wildfire particulate matter and related mortality in the United States

Climate change has increased forest fire extent in temperate and boreal North America. Here, we quantified the contribution of anthropogenic climate change to human mortality and economic burden from exposure to wildfire particulate matter at the county and state level across the contiguous US (2006 to 2020) by integrating climate projections, climate-wildfire models, wildfire smoke models, and emission and health impact modeling. Climate change contributed to approximately 15,000 wildfire particulate matter deaths over 15 years with interannual variability ranging from 130 (95% confidence interval: 64, 190) to 5100 (95% confidence interval: 2500, 7500) deaths and a cumulative economic burden of $160 billion. Approximately 34% of the additional deaths attributable to climate change occurred in 2020, costing $58 billion. The economic burden was highest in California, Oregon, and Washington. We suggest that absent abrupt changes in climate trajectories, land management, and population, the indirect impacts of climate change on human-health through wildfire smoke will escalate.

Long-term exposure to smoke PM2.5 and COPD caused mortality for elderly people in the contiguous United States

Wildfire events in the US are becoming more frequent and more intensive due to climate change. Fire smoke can significantly contribute to ambient PM2.5 (PM2.5, particles smaller than 2.5 µm in diameter) levels and alter its chemical composition. An emerging body of literature has linked COPD mortality and episodic wildfire smoke exposure, but studies on the effect of long-term fire smoke exposure is lacking. We aimed to evaluate how long-term exposure to smoke PM2.5 can affect COPD mortality among elderly people and to explore the spatial variability in this effect. We investigated all elderly people aged 65-100 years in the contiguous United States using Medicare and National Death Index data from 2008 to 2016. We identified three subregions based on wildfire smoke risk to indicate spatial differences in smoke exposure. We used time-varying Cox Proportional Hazards Models to explore the effect of smoke PM2.5 on COPD mortality. We found that smoke PM2.5 is strongly associated with COPD mortality. An increase of 1 µg/m3 in smoke PM2.5 was associated with a 9.2 % increase in COPD mortality among elderly people (95 % CI: 8.8 %-9.7 %). Specifically, A 1 µg/m3 increase in smoke PM2.5 may increase deaths by 40.4 %, 9.6 % and 3.9 % in low, moderate, and high wildfire risk areas, respectively. Our study reveals that long-term exposure to smoke PM2.5 significantly contributes to COPD mortality among elderly people. Notably, those living in regions with relatively lower wildfire risk appear vulnerable. Therefore, wildfire prevention should be emphasized in areas that are not typically wildfire active.

Wildfire and wood smoke effects on human airway epithelial cells: A scoping review

BACKGROUND

Wildfires, which occur naturally but are increasingly intensified by climate change, release a complex mixture of organic and inorganic pollutants. These emissions have significant public health implications, contributing to increased morbidity and mortality. Epidemiological and clinical studies have consistently shown that exposure to wildfire smoke exacerbates respiratory conditions such as chronic obstructive pulmonary disease (COPD) and asthma. There are many epidemiological studies of the potential impact of smoke on human health; however, there are remarkably few in vitro studies, and an investigation of the underlying mechanisms of wildfire and wood smoke exposure on airway epithelial cells is required to better understand their toxicity and significance.

OBJECTIVES

This scoping review aimed to critically examine studies on the association between wildfire and wood smoke exposure and airway epithelial cell responses.

METHODS

We conducted a systematic search of relevant studies that used a combination of keywords related to wood smoke, wildfire, and epithelial cells and were published up to May 2024. Studies were retrieved from MEDLINE, PubMed, Google Scholar, and Web of Science.

RESULTS

Twenty-three studies fulfilled our inclusion criteria and were included. This review highlights inflammation, oxidative stress, and cytotoxicity as key impacts of wildfire and wood smoke on airway epithelial cells, causing lung damage. More studies are needed to understand these effects and guide prevention strategies.

DISCUSSION

This scoping review underscores the need for further research to better understand the complex biological endpoints associated with exposure to wildfire/wood smoke, informing strategies to mitigate health effects, ultimately improving health and well-being of population exposed to wildfire/wood smoke.

Climate Change and Respiratory Health: Opportunities to Contribute to Environmental Justice: An Official American Thoracic Society Workshop Report

Adverse environmental exposures worsened by our changing climate threaten respiratory health and exacerbate existing social inequities that further undermine environmental justice (EJ). EJ is the capacity of all people, regardless of sociodemographic characteristics, to minimize harmful exposures and live a healthy life. EJ is achieved through the development, implementation, and enforcement of environmental laws, regulations, and policies. In 2023, an American Thoracic Society workshop convened a group of 39 clinicians, researchers, community advocates, research program administrators, and health policy experts to characterize the respiratory health threats and EJ concerns arising from climate change. The workshop explored four main climate areas through a socioecological and EJ perspective: 1) respiratory health risks, 2) respiratory health impacts in low- and middle-income countries, 3) climate mitigation and adaptation strategies, and 4) priority research infrastructure needs. The workshop committee concluded that climate change can directly and indirectly impair respiratory health and that persistently excluded or marginalized communities (including those in low- and middle-income countries) are disproportionately impacted. These disproportionately impacted communities also lack hazard monitoring and resources to evaluate and advocate for mitigation of adverse environmental exposures. Future respiratory health research must inform mitigation strategies to reduce climate-related emissions from industry to net zero. Researchers, communities, and policymakers require training and support to meaningfully engage with systems-thinking research as well as policy solutions focused on mitigating and adapting to climate change. Finally, the workshop committee recommends a rapid transition away from fossil fuel dependence to a world that provides an equitable allocation of clean transportation options and renewable sources of energy production.

Smoke Exposure and Respirator Use Among Wildland Firefighters: A Narrative Review

Climate change contributes to warm, dry conditions, which leads to longer and more active fire seasons. Wildland firefighters work long hours in smoky conditions without regulations requiring respiratory protection. Wildfire smoke has many toxic components, including high levels of fine particulate matter (PM2.5). Regular monitoring for short- and long-term health outcomes in wildland firefighter populations is uncommon. However, extrapolating from knowledge about the individual components of smoke, it is likely that the firefighters' health is negatively affected. Firefighters are routinely exposed to dangerous levels of smoke, which may lead to both acute and chronic health consequences. Current guidelines from Occupational Safety and Health Administration (OSHA), the U.S. Forest Service (USFS), and the Interagency Standards for Fire and Fire Aviation Operations do not recommend respirator use for wildland firefighters. The methodologies used to quantify exposure and harm likely underestimate actual risks. Although there are no respirators that can filter all known harmful components of wildfire smoke, this review examines the potential benefit of respirator use by reducing some of the most harmful components of the smoke. Smoke exposure among wildland firefighters needs to be further characterized and quantified. Regulations should be reassessed to accurately reflect the exposure and potential harm that firefighters face. This narrative review gathers information from peer-reviewed scientific literature, government publications, news articles, and personal conversations with both public- and private-sector professionals. The objectives are to describe the likely health effects of wildland firefighting, evaluate the evidence behind current respiratory protection guidelines, and propose potential solutions.

Gestational exposure to particulate matter from urban wildfires is associated with changes in circulating oxylipins but not flame retardants 7 to 13 months post-exposure

Exposure to fine particulate matter (PM2.5) from wildfire smoke has been linked to immune dysregulation underlying multiple health conditions, but data on the long-term effects of these exposures during gestation are lacking. Smoke PM2.5 from wildfires occurring in urban areas is of particular concern because it can carry persistent chemicals within household furniture or soil, as well as polyaromatic hydrocarbons (PAHs) from combusted materials. The present study investigated the long-term associations between wildfire PM2.5 and serum polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), PAHs and lipid mediators (i.e., oxylipins) involved in immune regulation in participants from the B-SAFE (Bio-Specimen Assessment of Fire Effects) study, which enrolled women pregnant during or shortly after the 2017 Tubbs Fire in California (n = 140). Serum samples were collected and assayed 7 to 13 months post-exposure, at which point 20 women were still pregnant and 120 women were postpartum. Adjusted linear regression models revealed a significant positive association between increasing PM2.5 (μg/m3) exposure and serum concentrations of benzo[k]fluoranthene, a PAH (β = 0.866, P = 0.0403, [95 %CI: 0.0389, 1.69]). No significant associations were observed between PM2.5 exposure and serum PBDEs, PCBs or other PAHs. Increased exposure to PM2.5 was associated with lower serum concentrations of lipoxygenase (LOX)-derived free oxylipins and increased concentrations of LOX-derived oxylipins esterified to circulating lipids. These findings provide new evidence of long-term effects of gestational wildfire PM2.5 exposure on serum benzo[k]fluoranthene levels and the turnover of oxylipins involved in immunity via the LOX pathway. Additional studies are warranted to better understand the impact of these changes on maternal and child health.

What drives parents' use of air quality indexes during wildfire smoke events: predictors of index knowledge, frequent checking, and following health guidance

Wildfire smoke poses a serious and growing health threat to communities in the United States (US), Canada, and beyond. Some populations-including children-are especially susceptible. Air Quality Indexes (AQIs) can inform parents about local air quality during smoke events and offer guidance on actions that protect children. In July-August 2023, parents from Oregon, Washington, California, and British Columbia (BC) (n = 2100) participated in an online cross-sectional study. Binary and ordinal logistic regression models were used to examine geographic, demographic, and psychosocial predictors of three dependent variables: knowledge of where to check AQI information, frequent checking of AQI information during wildfire seasons, and adherence to AQI health messages around reducing/rescheduling outdoor physical activity. Smoke-exposure analysis indicated widespread potential exposures to wildfire smoke across all four jurisdictions. Nonetheless, parents in BC, on average, were less likely to report knowing where to check AQI information, checked less frequently, and were less likely to adhere to AQI guidance than parents in the three US states. Adherence to AQI health messages did not differ by jurisdiction in the presence of other covariates, suggesting parents are equally likely to follow AQI guidance when they know where to find it and check it. Other consistent predictors of the three dependent variables included experience with prior smoke-related health impacts, smoke risk perceptions, and use of internet/mobile applications as sources of smoke information. These findings indicate that increased promotion of AQIs may benefit parents in some regions during wildfires. Future evaluations of smoke education initiatives could help health agencies share effective practices across jurisdictions and target interventions to increase AQI adoption.

Supplementary information

The online version contains supplementary material available at 10.1007/s11111-025-00491-w.

Exposure to low concentrations of PM2.5 and its constituents with preterm birth in Shenzhen, China: a retrospective cohort study

BACKGROUND

Due to the Air Pollution Prevention and Control Measures issued by the Chinese government, air quality has significantly improved, particularly with respect to PM2.5. However, studies on the relationship between low concentrations of PM2.5 and preterm birth (PTB) remain limited in China.

OBJECTIVE

To examine the associations between low concentrations of PM2.5 and its constituents and PTB.

METHODS

This retrospective cohort study was conducted from July 2021 to April 2023 in Shenzhen, China. Data on questionnaires and pregnancy outcomes were collected for each participant. Using the Tracking Air Pollution in China (TAP) dataset, we assessed the concentrations of PM2.5 and its chemical constituents, including sulfate (SO42-), nitrate (NO3-), organic matter (OM), black carbon (BC), and ammonium (NH4+). We applied a generalized additive model (GAM) to evaluate the relationship. The relationship between exposure to PM2.5 and its constituents and PTB was further examined using a method that combined dummy variable settings with trend tests. Stratified analysis was conducted to explore the potential factors.

RESULTS

Among 17,240 live-born infants, the rate of PTB was 6.0%, and the average exposure concentration of PM2.5 was 20.24 μg/m3. There were positive associations between PM2.5 and its constituents and PTB. With each interquartile range (IQR) increase in PM2.5 during the third trimester, the risk of PTB increased by 2.23 times. The exposure effects of sulfate (SO42-) and organic matter (OM) were comparable to the total PM2.5. The third trimester might be the critical susceptibility window. The risk was higher among women who conceived in the cold season and were exposed to higher temperatures during pregnancy.

CONCLUSION

Even at low levels, PM2.5 can still increase the risk of PTB, with varying health effects attributed to different constituents. This underscores the importance of further strengthening environmental management and characterizing the contributions of PM2.5 sources.

Environmental risk factors for all-cause dementia, Alzheimer's disease dementia, vascular dementia, and mild cognitive impairment: An umbrella review and meta-analysis

BACKGROUND

Mitigation of environmental risk factors for neurocognitive disorders could reduce the number of incident cases. We sought to synthesize the literature on environmental risk factors for dementia and mild cognitive impairment.

METHODS

We conducted an umbrella review and meta-analysis. Multiple databases were systematically searched to identify systematic reviews and meta-analyses of longitudinal studies examining environmental risk factors for dementia or mild cognitive impairment. We used random effects multi-level, meta-analytic models to synthesize risk ratios for each risk factor while accounting for overlap in the studies within reviews. As a secondary objective, we examined risk factors for two common phenotypes of dementia: Alzheimer's disease dementia and vascular dementia.

RESULTS

A total of 19 reviews containing 37 meta-analyses were included umbrella review. We found 9 factors where exposure was associated with higher risks of all-cause dementia: fine particulate matter, particulate matter, nitrogen dioxide, nitrogen oxides, carbon monoxide, shift work, night shift work, chronic noise, and extremely-low frequency magnetic fields. Neighbourhood greenness was associated with a lower risk of all-cause dementia. In a narrative review, we found that exposure to sulfur dioxide, proximity to roadways, ionizing radiation, aluminum, solvents, pesticides, and environmental tobacco smoke were also associated with dementia. We also found that fine particulate matter, extremely-low frequency magnetic fields, sulfur dioxide, chronic noise, and pesticides were related to Alzheimer's disease dementia. Fine particulate matter, particulate matter, and chronic noise were related to vascular dementia. No systematic review reported on mild cognitive impairment.

CONCLUSION

Achieving stronger air quality targets has the potential to reduce population-level dementia risk. Neighbourhood (i.e., greenness and chronic noise) and occupational (i.e., shift work) characteristics are associated with dementia and are viable public health intervention points. Additional research should examine the relationship between other environmental risk factors and mild cognitive impairment and specific types of dementia.

Fine Particulate Matter From 2020 California Wildfires and Mental Health-Related Emergency Department Visits

Importance

A growing body of research suggests that exposure to fine particulate matter (PM2.5; particle size 2.5 microns or smaller) may be associated with mental health outcomes. However, the potential impact of wildfire-specific PM2.5 exposure on mental health remains underexplored.

Objective

To investigate whether wildfire-specific PM2.5 exposure may be associated with emergency department (ED) visits for mental health conditions, including all-cause and for psychoactive substance use, nonmood psychotic disorders, anxiety, depression, and other mood-affective disorders during the extensive 2020 California wildfire season.

Design, Setting, and Participants

This cross-sectional study used data on ED visits from July to December 2020 obtained from the California Department of Health Care Access and Information (HCAI). Eligible participants were California residents who presented to an ED in California for mental health conditions without COVID-19. The data were analyzed between July 2020 and December 2020.

Exposure

Wildfire-specific PM2.5 exposure (with up to 7-day lags) based on participants' residential zip codes.

Main Outcomes and Measures

Daily ED visit counts for all-cause and disease-specific mental health conditions (F00-F99) identified using International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes at zip code tabulation areas.

Results

Between July and December 2020, there were 86 609 ED visits for mental health conditions (median [IQR] patient age, 38 [27-54] years; 40 272 female [46.5%]; 10 657 Black [12.3%], 30 044 Hispanic [34.7%], 35 145 White [40.6%]). Visits included psychoactive substance use (23 966 [27.6%]), nonmood psychotic disorders (16 714 [19.3%]), anxiety (26 711 [30.8%]), depression (10 422 [12.0%]), and other mood-affective disorders (5338 [6.2%]). During peak wildfire months, the median (IQR) daily concentration of wildfire-specific PM2.5 increased to 11.9 (3.9-32.5) μg/m3. A 10-μg/m3 increase in wildfire-specific PM2.5 was associated with higher ED visits for all-cause mental conditions (cumulative relative risk [cRR] over lag 0-7 days, 1.08; 95% CI, 1.03-1.12), depression (cRR over lag 0-7 days, 1.15; 95% CI, 1.02-1.30), other mood-affective disorders (cRR over lag 0-7 days, 1.29; 95% CI, 1.09-1.54), and anxiety (cRR over lag 0-4 days, 1.06; 95% CI, 1.00-1.12). Subgroup analyses suggested that wildfire smoke was associated with disproportionately increased ED visits among female individuals (eg, depression: cRR over lag 0-4 days, 1.17; 95% CI, 1.03-1.32) and young people (other mood-affective disorders: cRR over lag 0-4 days, 1.46; 95% CI, 1.08-1.98). Effect modification by race was found, with non-Hispanic Black individuals having an increased risk of ED visits for other mood-affective disorders (cRR over lag 0-5 days, 2.35; 95% CI, 1.56-3.53) and Hispanic individuals an increased risk for visits for depression (cRR over lag 0-7 days, 1.30; 95% CI, 1.06-1.59).

Conclusions and Relevance

Wildfire smoke exposure was associated with significantly increased odds of subsequent ED visits for mental health conditions in this cross-sectional study, with varying lag times for different subconditions and demographic groups.

Quantifying the association between pregnancy exposure to biomass-attributable PM2.5 and the risk of preterm birth and stillbirth: A case-control study in Sydney, Australia for 2010-2020

Biomass combustion, including wildfires and residential wood burning, is a significant source of particulate matter (PM2.5) in Australia, with potentially distinct health effects due to its unique chemical composition. This study aimed to quantify the association between exposure to ambient biomass-attributable PM2.5 and the risk of preterm birth and stillbirth across pregnancy windows in Sydney, Australia, from 2010 to 2020. We conducted case-control studies nested within a cohort of 578,391 singleton pregnancies, including 29,954 preterm births and 2,928 stillbirths. Controls were randomly selected using risk-set sampling. Daily all-source PM2.5 estimates at a 5 km resolution were obtained from a previous study. Days exceeding the 95th percentile of all-source PM2.5 at statistical area level 4 without significant dust storm pollution were classified as biomass-affected days. For these days, biomass-attributable PM2.5 was estimated using the remainder component from a seasonal trend decomposition, with the seasonal and trend components representing nonbiomass-attributable PM2.5. Conditional logistic regressions were used to analyze associations between biomass-attributable PM2.5 exposure and outcomes, adjusting for area-level socioeconomic factors, temperature, humidity, and temporal and seasonal trends. The odds ratio for preterm birth per interquartile range increase in biomass-attributable PM2.5 was 1.002 (95% CI = 0.997, 1.007) for the entire pregnancy average exposure, with similar null results across trimesters. For stillbirth, the odds ratio was 1.002 (95% CI = 0.985, 1.019) for the entire pregnancy average exposure, with comparable null findings across trimesters. These results suggest that in Sydney, biomass-attributable PM2.5 exposure during pregnancy may not increase the risk of preterm births or stillbirths.

Toxicological screening of PM2.5 from wildfires involving different biomass fuels

Wildfires are becoming increasingly frequent and severe, particularly in Southern Europe. In addition to their immediate environmental and socioeconomic impacts, wildfires release significant amounts of particulate matter (PM), which poses serious health and ecological risks. Gaseous (CO and CO2) and PM2.5 samples were collected directly from smoke plumes, and the modified combustion efficiency (MCE) was calculated to characterise combustion conditions. This study aims to assess the cytotoxicity, mutagenicity and ecotoxicity of PM2.5 collected during wildfires in Portugal, with a focus on how varying biomass types and combustion conditions impact these effects. Ecotoxicity assessments using Aliivibrio fischeri showed that PM2.5 samples ranged from toxic to extremely toxic, with mixed vegetation burns (eucalyptus, acacia, ferns) exhibiting the highest toxicity levels. Cytotoxicity tests on human lung epithelial cells (A549) demonstrated a dose-dependent decrease in metabolic activity and no membrane damage, while mutagenicity assays identified direct-acting mutagens from smouldering acacia debris combustion, specifically inducing frameshift mutations in Salmonella typhimurium strain TA98. Root growth inhibition tests showed no toxicity, with some samples, instead, promoting growth probably due to nutrient content. Peroxidase activity responses indicated that, at higher concentrations, the enzyme function could be reduced if defence mechanisms are overwhelmed or stimulated due to high nutrient levels. These findings highlight the complex and varying toxicological profiles of wildfire PM, emphasising the need for further research.

Air pollution and its impact on cancer incidence, cancer care and cancer outcomes

Air pollution is an under-recognised global health threat linked to an increased risk of cancers and is due primarily to the burning of fossil fuels. This review provides a high-level overview of the associations between outdoor and indoor air pollution and cancer risk and outcomes. Outdoor air pollutants are largely due to the burning of fossil fuels from human activities, although there is growing data implicating outdoor pollution from wildfire smoke. Indoor air pollution is primarily caused by burning solid fuel sources such as wood, coal and charcoal for household cooking and heating. There is a growing number of pieces of evidence linking exposure to pollution and the risk of developing cancers. The strongest evidence is seen on the positive association of air pollution, particularly particulate matter 2.5 with lung cancer. Emerging data implicate exposure to pollutants in the development of breast, gastrointestinal and other cancers. The mechanisms underlying these associations include oxidative stress, inflammation and direct DNA damage facilitated by pollutant absorption and distribution in the body. References were identified through a PubMed search for articles published in 2000 to October 2024 using the terms 'air pollution' or 'pollutants' and 'carcinoma' or ''cancer'. Air pollution poses significant risks to health. Its health impacts, including cancer risks, are often underestimated. Hazardous pollutants have been studied in several epidemiological cohort studies. Despite the mounting evidence, air pollution is often overlooked in predictive cancer risk models and public health intervention.

The effect of wildfire smoke exposure on student performance: A nationwide study across two decades (2000-2020) and over 40 million students in Brazil

The impact of wildfire smoke exposure on public health has been extensively studied, yet its potential consequences on academic performance remain relatively unexplored, particularly in the context of fire-prone regions, such as Brazil. We conducted a nationwide study of more than 40 million high school students in Brazil who took the National High School Exam (ENEM) between 2000 and 2020. We used mixed-effects regression models with state-specific random intercepts to examine the associations between the wildfire events and academic performance among Brazilian students. We accounted for multiple covariates, including socioeconomic status, spatiotemporal factors, air pollutants, and weather variables. We also explored the effect modification by exam subject (general subjects and essay), school management (private and public schools), location (urban and rural schools), and time period. Our findings suggest that increased wildfire events are associated with lower academic performance in both essay and general subjects. After adjustments for the covariates, the primary analysis results indicate a negative impact of wildfires on essay writing, with an estimated coefficient of -0.09 (95 % CI: -0.13; -0.05) with 100 wildfire records increase. Similarly, an increase of 100 wildfire records per year corresponded to a decrease of 0.10 (95 % CI: 0.06; 0.11) points for general subjects. This effect on academic performance was associated with a reduction of 0.33 % (95 %CI: 0.31 %; 0.34 %) in essay and 0.54 % (95 %CI: 0.52 %; 0.56 %) in general subjects. Our findings highlight the need for further attention to the influence of wildfire smoke exposure on student academic performance, suggesting that even small associations at the individual level could have broader implications for public health and education policies.

Depressed nestling growth during exposure to smoke from distant wildfires

Human and animal populations increasingly encounter smoke pollution as climate change enhances the frequency and intensity of wildfires. Most work on smoke effects in animals has studied populations close to fires, populations experiencing small, prescribed burns, or animals in the lab. In June of 2023, smoke from distant Canadian wildfires quickly elevated particulate matter (PM2.5) pollution in a wild house wren (Troglodytes aedon) population for three days before returning to baseline levels. Compared to previous years, nestlings experiencing three days of elevated PM2.5 within the first 6 days of life weighed less on days 6 and 10 after hatching and had shorter tarsometatarsus bones, a sign of smaller skeletal size. In contrast, nestlings that hatched before or after this event did not differ in size from previous years. Although sublethal, these effects may have important consequences for survival and reproduction. As wildfire activity increases, more wildlife populations are at risk of smoke-related fitness consequences, even those distant from the blaze.

Understanding the health impacts of the climate crisis

The climate crisis is the greatest threat to global health. Anthropogenic greenhouse gas emissions have increased the temperature of the Earth by over 1.5 °C and caused sea levels to rise by over 24 cm since the beginning of the 20th century. 2024 was the warmest year on record and the last 10 hottest years have all occurred in the last 10 years. Climate models suggest that global surface temperature could rise between 1.5 °C and 5.5 °C compared with the pre-industrial period by 2100, and sea-level rise could be between 0.5 m and 1.3 m. Climate change is already causing significant shifts in weather patterns and an increase in extreme weather events around the world, including droughts, heatwaves, wildfires, storms and floods. These are having an impact on the spread of infectious diseases and the severity of non-infectious diseases. Climate change is already causing food and water insecurity, increasing levels of malnourishment and the burden of disease. The unpredictable impacts of climate change and the perceived inaction from local, national and international leaders, is creating anxiety that is contributing to deteriorating mental health, particularly in young people. The health impacts of climate change will increase in the future if nothing is done to curb greenhouse gas emission. We need action to deal with the climate crisis while improving the health, security and income of the very poorest people in our global society. We must plan for a net zero world that provides healthy, safe and low environmental impact lives for 10 billion people by 2050.

Impact of occupational exposures in patients with chronic obstructive pulmonary disease: current understanding and knowledge gaps

PURPOSE OF REVIEW

Chronic obstructive pulmonary disease (COPD) is thought of as a disease caused by tobacco exposure, but numerous occupational exposures have been identified as risk factors for development of disease and exacerbations, although these remain underappreciated and underdiagnosed. We highlight evidence of occupational exposures and how they relate to COPD, while also looking at gaps in how the changing workplace might affect the occupational COPD landscape.

RECENT FINDINGS

Historical exposures linked to COPD included inorganic dusts like coal and silica and organic dusts like cotton and wood. Other data associated agricultural exposures, cleaning agents, air pollution, and construction work with COPD. As the workplace has evolved to include more work from home and growing industries like ridesharing and delivery, items like radon and indoor and outdoor air quality must be factored into the equation as occupational exposures with the potential to cause COPD and increase its morbidity. Despite this, causal conclusions with many risk factors are challenging due to the complex interaction between patient susceptibilities and environmental factors, both occupation-related and nonoccupation related.

SUMMARY

Additional studies are needed, not only to better evaluate occupational exposures and COPD pathogenesis, but also to look at more solution-oriented areas like precision medicine and interventions targeting a healthier workplace.

[Wildfires and their respiratory impact]

INTRODUCTION

Largely due to climate change, wildland fires are currently increasing in extent and frequency. While particles from fire smoke exhibit higher toxicity, those identified in wildland urban interface (WUI) areas, which are exacerbated by household and vehicle emissions, are even more toxic.

STATE OF THE ART

This review article is based on English-language papers published by peer-reviewed journals. Since a previous review article was published in 2018, only papers since 2017 have been selected. The respiratory impacts of wildfires in the general population include irritative symptoms, exacerbation of chronic respiratory diseases (asthma, rhino-sinusitis, COPD…) and excess short and probably long-term mortality. Among firefighters, the short-term impact of wildfires on respiratory function has yet to be clearly established. Asthma prevalence, asthma exacerbation rates and chronic obstructive pulmonary disease (COPD) occurrence seem to be higher than in other occupational groups. That said, the different studies have not highlighted excess mortality. As regards cancer, while mesothelioma incidence has clearly increased, lung cancer incidence generally has not.

PERSPECTIVES

Two areas require clarification: first, short-term respiratory impact according to the characteristics of inhaled smoke; the long-term impact of exposure to particles from fire smoke.

CONCLUSION

Forest fires have become increasingly worrisome, in terms of both their negative health impact and their detrimental contribution to climate change.

Emergency department visits in California associated with wildfire PM2.5: differing risk across individuals and communities

The threats to human health from wildfires and wildfire smoke (WFS) in the United States (US) are increasing due to continued climate change. A growing body of literature has documented important adverse health effects of WFS exposure, but there is insufficient evidence regarding how risk related to WFS exposure varies across individual or community level characteristics. To address this evidence gap, we utilized a large nationwide database of healthcare utilization claims for emergency department (ED) visits in California across multiple wildfire seasons (May through November, 2012-2019) and quantified the health impacts of fine particulate matter <2.5 μm (PM2.5) air pollution attributable to WFS, overall and among subgroups of the population. We aggregated daily counts of ED visits to the level of the Zip Code Tabulation Area (ZCTA) and used a time-stratified case-crossover design and distributed lag non-linear models to estimate the association between WFS and relative risk of ED visits. We further assessed how the association with WFS varied across subgroups defined by age, race, social vulnerability, and residential air conditioning (AC) prevalence. Over a 7 day period, PM2.5 from WFS was associated with elevated risk of ED visits for all causes (1.04% (0.32%, 1.71%)), non-accidental causes (2.93% (2.16%, 3.70%)), and respiratory disease (15.17% (12.86%, 17.52%)), but not with ED visits for cardiovascular diseases (1.06% (-1.88%, 4.08%)). Analysis across subgroups revealed potential differences in susceptibility by age, race, and AC prevalence, but not across subgroups defined by ZCTA-level Social Vulnerability Index scores. These results suggest that PM2.5 from WFS is associated with higher rates of all cause, non-accidental, and respiratory ED visits with important heterogeneity across certain subgroups. Notably, lower availability of residential AC was associated with higher health risks related to wildfire activity.

Source-resolved black carbon and PM2.5 exposures during wildfires and prescribed burns

Changes in climate and land-use have significantly increased both the frequency and intensity of wildland fires globally, exacerbating the potential for hazardous impacts on human health. A better understanding of particle exposure concentrations and scenarios is crucial for developing mitigation strategies to reduce the health risks. Here, PM2.5 and black carbon (BC) concentrations were monitored during wildland fires between 2022 and 2024, in fire-prone areas in Catalonia (NE Spain), by means of personal monitors (AirBeam2 and Micro-aethalometers AE51 and MA200). Results revealed that exposures to combustion aerosols (PM2.5 and BC) were significant and comparable during wildfires and prescribed burns (mean PM2.5 during wildfires = 152 μg/m3 vs. 110-145 μg/m3 for prescribed burns). Overall, BC/PM2.5 ratios showed a large variability as a function of the monitoring scenario, indicating varying contributions from mineral aerosols to the emissions mix originating from fire management and extinction tasks. Specifically, mop-up tasks (final extinction tasks involving stirring top soil using handheld tools) were identified as a significant contributor to PM2.5 exposures, with 1-min PM2.5 peak concentrations reaching up to 1190 μg/m3. These results may be especially valuable for emissions modelling. Source apportionment of multi-wavelength BC datasets provided deeper insights into emissions and their impact on exposure profiles: line operators (who control the fire perimeter) were predominantly exposed to biomass burning smoke BCbb (61%) when compared to BC from fossil-fuel combustion (BCff = 39%), while torchers (in charge of initiating technical fires using fossil-fuel drip-torches) were predominantly exposed to BCff (77% vs. 23% BCbb). These findings highlight the value of portable monitors in the assessment of wildfire emissions and impacts on human exposure and environment. The combination of these tools, reporting data in real-time and with high time-resolution, is key to the design and implementation of effective mitigation strategies for environmental and health concerns related to wildland fires.

Climate-Driven Escalation of Global PM2.5 Health Burden from Wildland Fires

Wildland fires constitute a major source of ambient fine particulate matter (PM2.5), significantly impacting air quality and public health. As the climate becomes warmer and drier, fire frequency is projected to rise, yet how the associated health impacts of fire-sourced PM2.5 (FPM2.5) respond to climate change remains vague. In this study, we modeled the global concentration and associated premature deaths of FPM2.5 over the past two decades. Our results reveal an upward trend in FPM2.5 concentrations globally, contributing to an increase in premature deaths from 156,000 to 241,000 between 2000 and 2021, alongside population growth and aging. Substantial variations are observed on a regional scale, but most regions experience increasing exposure levels, suggesting an increased impact of FPM2.5. Further regression analysis indicates that climate change plays a critical role in these trends, accounting for 56% of the net changes in FPM2.5-related premature deaths. Warming and drought emerge as key drivers of climate-induced health risks, with slightly different contributions to the FPM2.5 concentration and the associated premature deaths. Our findings underscore the urgent need to integrate climate adaptation strategies with fire management to mitigate the growing health burden caused by FPM2.5 worldwide.

Impacts of wildfire smoke PM2.5, greenspace and terrain ruggedness on life expectancy in the contiguous United States

Wildfire smoke PM2.5 has been associated with many adverse health effects. However, little is known about its impact on life expectancy. This study investigated the impact of wildfire smoke PM2.5 and its interaction with greenspace and terrain ruggedness on life expectancy in the contiguous United States. By analyzing life expectancy estimates during the 2010 to 2015 period in 66,263 census tracts with multi-level regression models adjusted for income, age, race, and population density, we found that life expectancy was negatively associated with the concentration of smoke PM2.5 and the number of smoke days. Specifically, the increase of 1 μg/m3 in the annual daily average smoke PM2.5 levels is associated with a decrease in life expectancy by 1.10 years (regression coefficient β = -1.10, 95 % confidence interval (CI): [-1.21, -0.99]). For every extra smoke day, life expectancy might decrease by 0.021 years (β = -0.021, 95 % CI: [-0.024, -0.018]). Additionally, the interaction of greenspace with smoke PM2.5 negatively affected life expectancy (β = -0.29, 95 % CI: [-0.38, -0.21]). No significant relationship was observed between life expectancy and terrain ruggedness. The generalized additive model revealed that the impact of smoke PM2.5 on life expectancy varied across concentration levels. The sensitivity analysis confirmed that the results were robust. Our study suggests that wildfires not only have a direct negative effect on life expectancy but also diminish the beneficial impact of greenspace, potentially turning its positive effects detrimental.

The heterogenous molecular characteristics of biomass-pyrogenic smoke dissolved organic matters (BPS-DOMs) binding with PAHs: Novel insights from combined analysis of FT-ICR MS and fluorescence variation

Biomass-pyrogenic smoke dissolved organic matter (BPS-DOM) can co-deposit with polycyclic aromatic hydrocarbons (PAHs), thereby altering their environmental behavior and fate in surface environments. However, the heterogeneous molecular characteristics of BPS-DOM binding with PAHs remain unclear. This study systematically elucidates the binding characteristics of PAHs (phenanthrene and pyrene), with various molecular compositions in BPS-DOM, utilizing FT-ICR MS and fluorescence variation analysis. CHO compounds in BPS-DOM, characterized by high aromaticity and abundant CO bonds, significantly enhance PAHs binding by promoting π-π electron donor-acceptor interactions. In contrast, CHON compounds with higher aliphaticity inhibit pyrene binding by competing for binding sites on BPS-DOM. Furthermore, the binding sequence of different fluorescent molecules follows the order of CHO→CHOS→CHON for phenanthrene and CHO→CHON→CHOS for pyrene. This was primarily due to the larger conjugated aromatic structures of CHO compounds, which provide stronger π-π interaction sites for PAHs binding. The difference in binding sequences between phenanthrene and pyrene is primarily attributed to phenanthrene's reliance on π-π electron donor-acceptor interactions induced by -SO and -N = O, while pyrene binding depended on π-π interactions driven by larger conjugated aromatic structures. These results provide an important theoretical foundation for further understanding the molecular-level interactions between BPS-DOM and PAHs.

Impacts of Aging and Relative Humidity on Properties of Biomass Burning Smoke Particles

Quantifying changes in the properties of smoke aerosols under varying conditions is important for understanding the health and environmental impacts of exposure to smoke. Smoke composition, aerosol liquid water content, effective density (ρeff), and other properties can change significantly as smoke travels through areas under different ambient conditions and over time. During this study, we measured changes in smoke composition and physical properties due to oxidative aging and exposure to humidity. We found that smoke aging led to SOA formation and increases in ratios of organic carbon to elemental carbon. Aerosol liquid water content increased with increasing relative humidity (RH), and aged smoke took up more water than fresh smoke at all humidity levels, likely due to a combination of changes in aerosol surface polarity at low and medium RH and increases in surface area with aging at high RH. Growth factors ranged from 1.06 ± 0.08 for fresh smoke at low RH to 1.32 ± 0.08 for aged smoke at high RH. Oxidative aging and exposure to humidity led to increases in ρeff. For 100 nm particles, ρeff ranged from ∼1.2 for fresh smoke at low RH to ∼1.6 for aged smoke at high RH. Results from these experiments suggest that exposure to humidity leads to smoke restructuring and compaction and/or changes in surface chemistry.

The effect of wildfire smoke on children's health: A systematic review

BACKGROUND

With wildfires increasing globally due to climate change, children may be more behaviourally exposed and more physiologically vulnerable to adverse health outcomes.

OBJECTIVE

To complete a comprehensive investigation of epidemiological studies examining respiratory and non-respiratory impacts of wildfires to identify research gaps and inform decision-making to protect children's health.

DATA SOURCES

The databases searched were PubMed, Embase, Scopus and Google Scholar.

STUDY SELECTION AND DATA EXTRACTION

Global epidemiological studies that investigated individuals under the age of 18 and were published from January 2006 to July 2024 were eligible to be included. Studies were included if they had wildfire days, smoke, or pollutants as the main exposure and had an outcome related to children's health. Though a meta-analysis was not possible, results were reported qualitatively through summaries of evidence tables and noteworthy results and the magnitude of the associations for each outcome was reported.

RESULTS

Twenty-four studies were selected. Sixteen studies examined respiratory outcomes and 11 studies included non-respiratory outcomes. A meta-analysis was not conducted, and consistent conclusions could not be made due to the heterogeneity and the small number of studies. Most respiratory-related studies found positive associations between wildfire exposure and adverse respiratory outcomes. All non-respiratory outcomes, except physical activity, had positive associations with wildfire exposure. For most non-respiratory outcomes, only one study evaluated each outcome. Higher-risk children were asthmatic, obese, under the age of five, in low-income countries or with a low socio-economic status.

CONCLUSIONS

There is consistent evidence that wildfire exposure is associated with adverse respiratory health in children, globally. There is less consistent evidence for the effect of wildfire exposure on non-respiratory outcomes. Further long-term research on non-respiratory outcomes in children, specifically physical activity, academic success and mental health is needed, especially in high-risk populations.

Polycyclic aromatics-derived benzene carboxylic acids (BPCAs) as a fast predictor of the genotoxicity of combustion particles

Polycyclic aromatic compounds (PAC) are common toxics in combustion particles. Numerous studies on health effects of PAC mixtures focused on limited compounds. It's still challenging to quantify complex PAC mixtures in combustion particles. Recently, benzene polycarboxylic acids (BPCAs) method, which involves conversion of PAC mixtures into a few BPCAs, has been used to quantify complex PAC mixtures in particles. In this study, in vitro biossays were used to evaluate the toxicity of extractable organic matter (EOM) in combustion particles. Analysis with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) identified ~1000 molecules, mostly aromatics (84.47 ± 5.32 %), that positively associate with the EOM toxicity (p < 0.05). We further employed BPCAs method to quantify PAC mixtures in the EOM of combustion particles, and observed the toxicity (especially genotoxicity) of EOM linearly increases with the abundance of PAC mixtures (r2: 0.68-0.89, p < 0.05), as it is shown by a data set referring to all source types including biomass burning, coal combustion and vehicle exhaust. The genotoxicity of PAC mixtures in EOM of combustion particles was estimated to be 10-13 times that of benzo[a]pyrene at the same mass concentration. Target analysis of 48 PAC was carried out, but a weaker relationship is found for the toxicity of EOM and the abundance of 48 PAC. Taken together, we suggest PAC-derived BPCAs as a fast predictor of the genotoxicity of combustion particles, which could be promising in routine monitoring of PAC pollution in the air.

Probing Interactions at the Organic-Inorganic Interface of Biomass Burning Aerosol: Reactivity of Organic Tracer Species with Different Iron Oxide Mineral Phases

As wildfire events become more frequent, there is a need to better understand the impact of smoke on the environment and human health. Smoke, or biomass burning aerosol (BBA), can undergo atmospheric processing changing its chemical and optical properties. We examined the interactions between four lignin pyrolysis products (catechol, syringol, syringic acid, and vanillic acid) and three BBA-relevant iron oxide mineral phases (hematite, maghemite, and magnetite) using attenuated total reflectance-Fourier transform infrared spectroscopy and dissolved iron measurements to better understand how atmospheric processing changes concentrations of soluble iron, iron oxidation state, and brown carbon abundance. Reductive dissolution was the primary dissolution mechanism for catechol and syringol, which led to a substantial amount of iron release (p < 0.05), whereas syringic and vanillic acids had little impact on dissolution. Comparisons with other BBA relevant compounds highlight the importance of both steric and electronic structures in the reductive dissolution process. The maghemite and magnetite phases, which are more likely to be present in BBA, released significantly more dissolved iron than hematite (p < 0.05), emphasizing the need to use BBA relevant iron oxide proxies in laboratory studies. This work provides insight into observations of iron dissolution and transformation of organics in BBA.

Lung function may recover after coal mine fire smoke exposure: a longitudinal cohort study

BACKGROUND AND OBJECTIVE

The 2014 Hazelwood coal mine fire exposed residents in nearby Morwell to high concentrations of particulate matter <2.5 µm (PM2.5) for approximately 6 weeks. This analysis aimed to evaluate the long-term impact on respiratory health.

METHODS

Adults from Morwell and the unexposed town of Sale completed validated respiratory questionnaires and performed spirometry, gas transfer and oscillometry 3.5-4 years (round 1) and 7.3-7.8 years (round 2) after the fire. Individual PM2.5 exposure levels were estimated using chemical transport models mapped onto participant-reported time-location data. Mixed-effects regression models were fitted to analyse associations between PM2.5 exposure and outcomes, controlling for key confounders.

RESULTS

From 519 (346 exposed) round 1 participants, 329 (217 exposed) participated in round 2. Spirometry and gas transfer in round 2 were mostly lower compared with round 1, excepting forced vital capacity (FVC) (increased) and forced expiratory volume in 1 second (minimal change). The effect of mine fire-related PM2.5 exposure changed from a negative effect in round 1 to no effect in round 2 for both pre-bronchodilator (p=0.005) and post-bronchodilator FVC (p=0.032). PM2.5 was not associated with gas transfer in either round. For post-bronchodilator reactance and area under the curve, a negative impact of PM2.5 in round 1 showed signs of recovery in round 2 (both p<0.001).

CONCLUSION

In this novel study evaluating long-term respiratory outcomes after medium-duration high concentration PM2.5 exposure, the attenuated associations between exposure and respiratory function may indicate some recovery in lung function. With increased frequency and severity of landscape fires observed globally, these results inform public health policies and planning.

Evidence for cytotoxicity and mitochondrial dysfunction in human lung cells exposed to biomass burning aerosol constituents: Levoglucosan and 4-nitrocatechol

Biomass burning (BB) emissions are one of the largest sources of carbonaceous aerosol, posing a significant risk as an airway irritant. Important BB markers include wood pyrolysis emissions, such as levoglucosan (LG) that is an anhydrous sugar bearing a six-carbon ring structure (i.e., 1,6-anhydro-β-D-glucopyranose). Atmospheric chemical aging of BB-derived aerosol (BBA) in the presence of nitrogen oxides (NOx) can yield nitro-aromatic compounds, including 4-nitrocatechol (4NC). There is building evidence that NOx-mediated chemical aging of BBA poses a more serious exposure effect than primary pyrolysis emissions. This study provides a comparative toxicological assessment following the exposure to important BBA marker compounds in human lung cells (i.e., A549 and BEAS-2B) to determine whether aromatic 4NC is more toxic than BBA-bound anhydrous carbohydrate (i.e., LG). We determined inhibitory concentration-50 (IC50) and examined reactive oxygen species (ROS) changes, mitochondrial dysfunction, and apoptosis induction in the two cell lines following exposure to LG and 4NC in a dose-response manner. In the BEAS-2B cells, estimated IC50 values for 4NC were 33 and 8.8 μg mL-1, and for LG were 2546 and ∼3 × 107 μg mL-1 at 24 h and 48 h of exposure, respectively. A549 cells exhibited a much higher IC50 value than BEAS-2B cells. LG exposures resulted in mitochondrial stress with viability inhibition, but cells recovered with increasing exposure time. 4NC exposures at 200 μg mL-1 resulted in the induction of apoptosis at 6 h. Mitochondrial dysfunction and ROS imbalance induced the intrinsic apoptotic pathway induction following 4NC exposures. While increased ROS is caused by LG exposure in lung cells, 4NC is a marker of concern during BB emissions, as we observed apoptosis and high mitochondrial ROS in both lung cells at atmospherically-relevant aerosol concentrations. It may be associated with higher airway or inhalation pathologies in higher BBA emissions, such as wildfires or during wood combustion.

Wildfire Smoke: Health Effects, Mechanisms, and Mitigation

Wildfires are becoming more frequent and intense on a global scale, raising concerns about their acute and long-term effects on human health. We conducted a systematic review of the current epidemiological evidence on wildfire health risks and a meta-analysis to investigate the association between wildfire smoke exposure and various health outcomes. We discovered that wildfire smoke increases the risk of premature deaths and respiratory morbidity in the general population. Meta-analysis of cause-specific mortality and morbidity revealed that wildfire smoke had the strongest associations with cardiovascular mortality (RR: 1.018, 95% CI: 1.014-1.021), asthma hospitalization (RR: 1.054, 95% CI: 1.026-1.082), and asthma emergency department visits (RR: 1.117, 95% CI: 1.035-1.204) in the general population. Subgroup analyses of age found that adults and elderly adults were more susceptible to the cardiopulmonary effects of wildfire smoke. Next, we systematically addressed the toxicological mechanisms of wildfire smoke, including direct toxicity, oxidative stress, inflammatory reactions, immune dysregulation, genotoxicity and mutations, skin allergies, inflammation, and others. We discuss wildfire smoke risk mitigation strategies including public health interventions, regulatory measures, and personal actions. We conclude by highlighting current research limitations and future directions for wildfire research, such as elucidating the complex interactions of wildfire smoke components on human health, developing personalized risk assessment tools, and improving resilience and adaptation strategies to mitigate the health effects of wildfires in changing climate.

Polluted Air from Canadian Wildfires and Cardiopulmonary Disease in the Eastern US

Importance

Intense wildfires affecting residential populations are increasingly frequent. However, the adverse cardiopulmonary consequences to patients from remote wildfire smoke exposure is uncertain.

Objective

To investigate the association between wildfire smoke originating in Western Canadian provinces with cardiopulmonary disease burden in sociodemographically heterogenous populations in the Eastern US.

Design, Setting, and Participants

This case-only study used International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes for cardiopulmonary diseases extracted from the University of Maryland Medical System in June 2023 vs June 2018 and June 2019. Data were analyzed from September 2023 to September 2024.

Exposures

High air pollution episodes where the concentration of particulate matter with aerodynamic diameter below 2.5 μm (PM2.5) exceeded the toxic National Ambient Air Quality Standard (35 μg/m3) (referred to as "hotspot days") on contiguous days.

Main Outcomes and Measures

The number of patients with inpatient, ambulatory, and emergency department clinical encounters during assigned hotspot days in June 2023 compared with matching days in June of control years. Adjustments for covariates for comparisons between groups were made with χ2 tests and multivariable logistic regression.

Results

Statewide air quality analysis identified June 6-8 and 28-30 as 6 hotspot days with an increase in PM2.5 by 9.4-fold and 7.4-fold, respectively, in Baltimore City compared with all other days in 2023. After adjusting for calendar days across years, the cohort included 2339 cardiopulmonary clinical encounters in June 2023 (mean [SD] age, 68 [15] years; 1098 female [46.9%]; 710 Black [30.4%], 1528 White [65.3%]) and 3609 encounters in June 2018-2019 (mean [SD] age, 65 [15] years; 1690 female [46.8%]; 1181 Black [32.7%], 2269 White [62.9%]). The proportion of clinical encounters occurring during hotspot days in June 2023 was 588 of 2339 days (25.1%) vs 806 of 3609 days (22.3%) in control years (χ2 = 6.07; P = .01), with an adjusted odds ratio (aOR) of 1.18 (95% CI, 1.03-1.34; P = .02). Restricting this analysis to cardiac diseases, there was a 20% increase in adjusted odds for a clinical encounter (aOR, 1.20; 95% CI, 1.01-1.42; P = .04). Patients with cardiopulmonary encounters on hotspot days had greater socioeconomic advantage vs control years by ADI score (mean [SD] score, 39.1 [21.1] vs 41.0 [23.7]; P = .05).

Conclusions and Relevance

In this case-only study of a large medical system, we identified an increased cardiopulmonary disease burden for residents of Maryland that was likely associated with contemporaneous wildfire smoke-based infiltration of polluted or toxic air originating from Western Canada up to 2100 miles remotely.

Airborne antibiotic resistome from sludge dewatering systems: Mobility, pathogen accessibility, cross-media migration propensity, impacting factors, and risks

Bioaerosol contamination was considered as a potential health threat in sludge dewatering systems (SDSs), while emission and risk of airborne antibiotic resistome remain largely unclear. Herein, seasonal investigations of fine particulate matter (PM2.5) were conducted using metagenomics-based methods within and around different SDSs, together with an analysis of sewage sludge. Featured with evident seasonality, antibiotic resistance genes (ARGs) in SDS-PM2.5 also possessed greater accumulation, transfer, and pathogen accessibility than those in ambient air PM2.5. Mobile ARGs in SDS-PM2.5 mainly encoded resistance to tetracycline, and most were flanked by integrase. Some pathogenic antibiotic resistant bacteria (PARB), including Enterobacter asburiae, Escherichia coli, Enterococcus faecium, and Staphylococcus aureus, also carried mobile genetic elements in SDS-PM2.5. Dewatering behavior actuated > 50.56% of ARG subtypes and > 42.86% of PARB in sewage sludge to aerosolize into air. Relative humidity, temperature, and PM2.5 concentration collectively drove the evolution of bacterial community and indirectly promoted the antibiotic resistance of SDS-PM2.5. SDS-PM2.5 posed more serious resistome risks than sewage sludge and ambient air PM2.5, and the highest levels were discovered in winter. These findings underline the role of dewatering behavior in facilitating resistome's aerosolization, and the need to mitigate this potential air pollution.

The temporal trend and disparity in short-term health impacts of fine particulate matter in California (2006-2019)

Most epidemiological studies assume that the relationship between short-term air pollution exposure and health outcomes is constant over time, which ignores potential changes in population composition and particulate matter emission sources. Limited studies have assessed changes in the relationship between fine particulate matter (PM2.5) and adverse health outcomes over time, with mixed results. Additionally, there is a need to identify which subgroups are disproportionately impacted over time by PM2.5-related health consequences. Therefore, we aimed to examine whether temporal trends exist in the relationships between daily PM2.5 exposure and circulatory and respiratory acute care utilization in California from 2006 to 2019. We further assessed whether certain subpopulations are more susceptible to PM2.5 exposure by demographic characteristics and extreme wildfire frequency. Daily PM2.5 concentrations estimated from a stacked ensemble model and daily cause-specific acute care utilization and demographic data from the California Department of Health Care Access and Information. We analyzed this relationship using modified two-stage Bayesian hierarchical models, where we first did not consider temporal trends, then stratified by two periods, and finally flexibly considered non-linear changes over time. Increases in circulatory (0.56 %; 95 % credible interval (CI): 0.17 %, 0.96 %) and respiratory acute care utilization risk (2.61 %; 95%CI: 2.29 %, 2.94 %) were found with every 10 μg/m3 increase in PM2.5 on the same day and previous two days. These risks were found to increase over time, where 0.13 % (95%CI: 0.02 %, 0.22 %) and 1.40 % (95%CI: 1.24 %, 1.54 %) increases were identified for circulatory and respiratory acute care utilizations, respectively, from the first (2006-2012) to second period (2013-2019). Differences by age, sex, race/ethnicity, and extreme wildfire frequency were noted. These findings confirm that air pollution guidelines should consider the dynamic nature of epidemiological dose-response and can provide insight for targeted air pollution control and adaptation policies designed to reduce PM2.5 exposure, particularly for the most susceptible subpopulations.

Intersections between climate change and antimicrobial resistance: a systematic scoping review

Climate change and antimicrobial resistance (AMR) present crucial challenges for the health and wellbeing of people, animals, plants, and ecosystems worldwide, yet the two are largely treated as separate and unrelated challenges. The aim of this systematic scoping Review is to understand the nature of the growing evidence base linking AMR and climate change and to identify knowledge gaps and areas for further research. We conducted a systematic search of the peer-reviewed literature in Scopus, Web of Science, and PubMed on 27 June, 2022. Our search strategy identified and screened 1687 unique results. Data were extracted and analysed from 574 records meeting our inclusion criteria. 222 (39%) of these reviewed articles discussed harmful synergies in which both climate change and AMR exist independently and can interact synergistically, resulting in negative outcomes. Just over a quarter (n=163; 28%) of the literature contained general or broad references to AMR and climate change, whereas a fifth (n=111; 19%) of articles referred to climate change influencing the emergence and evolution of AMR. 12% of articles (n=70) presented positive synergies between approaches aimed at addressing climate change and interventions targeting the management and control of AMR. The remaining literature focused on the shared drivers of AMR and climate change, the trade-offs between climate actions that have unanticipated negative outcomes for AMR (or vice versa), and, finally, the pathways through which AMR can negatively influence climate change. Our findings indicate multiple intersections through which climate change and AMR can and do connect. Research in this area is still nascent, disciplinarily isolated, and only beginning to converge, with few documents primarily focused on the equal intersection of both topics. Greater empirical and evidence-based attention is needed to investigate knowledge gaps related to specific climate change hazards and antimicrobial resistant fungi, helminths, protists, and viruses.

Biomass burning in Peninsular Southeast Asia intensifies meteorological drought in Southwest China

Biomass burning in Peninsular Southeast Asia (BB-PSEA) affects the climate in downwind regions, especially precipitation (PRE) in southern China. However, the impact of BB-PSEA on the meteorological drought in Southwest China (SWC), where closes to PSEA and often occurs seasonal drought, have not been clear yet. We selected a severe drought event in SWC from January to April 2010 and conducted sensitivity simulations using WRF-Chem (Weather Research and Forecasting model coupled with Chemistry) to evaluate the impact of BB-PSEA on the meteorological drought in SWC. Comparisons with observations revealed that the model performed well in simulating the spatiotemporal evolution of the drought in SWC. BB-PSEA increased the drought severity by 0.01-0.75 levels, enlarged drought areas by about 10%, and prolonged the drought duration mainly by one month in SWC. The impact of BB-PSEA on the drought in SWC in March/April was almost tenfold that in January/February, due to the higher emissions of BB-PSEA in March/April. The mechanism that BB-PSEA influenced drought predominantly involved the reduction of PRE, potential evapotranspiration (PET), and moisture fluxes in SWC. BB-PSEA aerosols warmed the air at 600-800 hPa and cooled the air near the surface in SWC, which stabilized the atmosphere and suppressed PRE and reduced PET in SWC. BB-PSEA aerosols also increased the sea surface temperature in South China Sea and the geopotential heights in the north of the Bay of Bengal, where the moisture sources of SWC originated from. This perturbation reduced the moisture fluxes across the west and south boundaries of SWC, resulting in the reduction of the water vapor content and PRE in SWC. Through elucidating the impact of BB-PSEA on the drought in SWC, this study clarified how BB-PSEA affected the climate in the downwind region and provided new understanding for drought prediction in SWC.