Human health effects of wildfire smoke

Water and Air Quality Bureau, Health Canada
May 2024

On this page

• 1.0 Introduction
• 2.0 Health effects of wildfire smoke
  • 2.1 Mortality
  • 2.2 Respiratory morbidity
  • 2.3 Cardiovascular morbidity
  • 2.4 Reproductive and developmental effects
  • 2.5 Mental health
  • 2.6 Mechanisms of toxicity of wildfire smoke
  • 2.7 Disproportionately impacted populations
• 3.0 Conclusions and considerations
• Appendix: Methodology
  • Approach
  • Search strategy and article selection
  • Data extraction
• References

1.0 Introduction

Wildfires, the uncontrolled burning of natural vegetation, are a major natural hazard and an important part of many ecosystems. Smoke from wildfires is a complex mixture of water vapour, gases, and particles, with many of the individual components associated with adverse health effects. The chemical composition of wildfire smoke is highly variable and determined by many factors including the type and composition of the vegetation burning (for example, wet or green vegetation versus dead or dry vegetation; forests versus grasslands; hardwood versus softwood; etc.), the physical and chemical combustion processes (for example, flaming versus smoldering), and weather conditions (for example, temperature, humidity) (Andreae and Merlet 2001; Black et al., 2017).

Wildfires are a major source of air pollution around the world. They are sources of primary emissions (that is, emitted directly into the environment) of particulate matter (PM), carbon dioxide (CO₂), carbon monoxide (CO), nitrogen oxides (NOx), methane, volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs) and of secondary pollutants (that is, pollutants formed through atmospheric chemistry), such as ozone (O₃) and secondary organic aerosols (Urbanski et al., 2008). Wildfire smoke can impact air quality in areas in close proximity to the wildfire activity and regionally or continentally due to long-range transport and transformation of the fire emissions (Urbanski et al., 2008; Matz et al., 2020).

As wildfires are a global issue, the health effects of wildfire smoke exposure are an active and growing area of research. Furthermore, there is growing interest in wildfires and the associated health effects as climate change is anticipated to increase wildfire activity by increasing the fire season length and frequency of fires (Wotton et al., 2017; Sun et al., 2019). Given this context and to better inform federal Health Portfolio guidance and actions related to wildfire smoke, there is a need to evaluate the scientific literature on the health effects of wildfire smoke.

The objective of this document is to provide a concise weight-of-evidence review of health outcomes associated with exposure to wildfire smoke. Specifically, the goal is to characterize the strength of the evidence for individual health endpoints rather than quantifying the risk level of each outcome. The approach consisted of a review of published systematic reviews, including meta-analyses, of primary studies examining the association between exposure to wildfire smoke and mortality and morbidity outcomes. The primary studies captured in the reviews were conducted in North America, South America, Australia, Europe and Asia. Systematic reviews provide a robust synthesis of available scientific evidence, and are leveraged here to provide a rapid evidence synthesis. Details of the methodology used for this evidence synthesis are provided in the Appendix.

Evaluation of air pollution from wildfires presents unique challenges, compared to air pollution from other sources, such as traffic or industrial point sources, as smoke exposure is seasonal and episodic in nature (Gould et al., 2023). Also, as the number and size of wildfires impacting an area are variable and as smoke production from wildfires is not constant or steady, the concentration of smoke experienced by populations can vary considerably, and can include high levels of exposure for short time periods or moderate exposure levels lasting for several days or longer. Additionally, to evaluate the health effects of wildfire smoke, it is necessary to distinguish the contribution of wildfire smoke from that of other sources of air pollution within the mixture that people are exposed to. To address this, researchers have employed a variety of methods to assess exposure to wildfire smoke for use in health studies including use of land-based PM monitors, satellite imagery, air quality modelling, comparison of fire versus non-fire periods, proximity to wildfire burn area, and self-reports. In these studies, the most commonly used surrogates for wildfire smoke exposure are PM_2.5 (particles with a diameter of 2.5 micrometres or less) and PM₁₀ (particles with a diameter of 10 micrometres or less). For the primary investigations included in the systematic reviews considered here, the health outcome data were based on administrative sources (for example, mortality registries, health care utilization data), surveys, or self-reports. In addition, most of the primary studies focused on short-term or episodic exposure to wildfire smoke (that is, daily exposure), while some of the studies assessing mental health impacts considered health effects in years following the wildfires, and studies of reproductive or developmental impacts considered wildfire smoke exposure during the gestational period. It is noted that the health effects of PM_2.5, a key pollutant in wildfire smoke, have been extensively studied and Health Canada has evaluated the health risks of ambient PM_2.5 (that is, PM_2.5 from all sources combined) (Health Canada 2022).

2.0 Health effects of wildfire smoke

2.1 Mortality

Most reviews of the epidemiological evidence identified a consistent association between wildfire smoke exposure and increased risk of all-cause mortality, while in comparison, the evidence for respiratory- or cardiovascular-specific mortality is mixed and less conclusive (Youssouf et al., 2014; Adetona et al., 2016; Liu et al., 2016; Reid et al., 2016; Black et al., 2017; Chen et al., 2021; Karanasiou et al., 2021; Barros et al., 2023; Gao et al., 2023; Gould et al., 2023; Jiao et al., 2024). From the two systematic reviews that included meta-analysis, the pooled analyses identified significant associations between daily all-cause mortality and various measures of wildfire smoke exposure (summarized in Table 1) (Karanasiou et al., 2021; Gould et al., 2023). The recent reviews of the cardiovascular (Chen et al., 2021) and respiratory (Jiao et al., 2024) effects of wildfire smoke concluded that while a majority of the primary studies of cause-specific mortality have observed positive associations, only a few studies had statistically significant risk estimates, and null associations have also been reported in some of the studies. However, the meta-analysis by Karanasiou et al. (2021) identified a significant increase in risk of cardiovascular mortality for smoky compared to non-smoky days (Table 1); in comparison, there were insufficient data for a pooled analysis based on pollutant concentration, which are more refined exposure metrics.

2.2 Respiratory morbidity

From a large number of primary studies, there is consistent and significant evidence of an association between wildfire smoke exposure and an increased risk of emergency room visits (ERVs), hospital admissions (HAs), physician visits, or medication dispensations for respiratory conditions (Youssouf et al., 2014; Adetona et al., 2016; Liu et al., 2016; Reid et al., 2016; Black et al., 2017; Borchers Arriagada et al., 2019; Henry et al. 2021; Karanasiou et al., 2021; Skinner et al., 2022; Barros et al., 2023; Gao et al., 2023; Gould et al., 2023; Zhang et al., 2023; Jiao et al., 2024). From the four systematic reviews that included meta-analysis, the pooled analyses considered different wildfire smoke exposure metrics and determined significant increases in all-cause respiratory HAs and ERVs (summarized in Table 2) (Borchers Arriagada et al., 2019; Karanasiou et al., 2021; Barros et al., 2023; Gould et al., 2023).

Regarding specific respiratory endpoints, there is consistent and significant evidence supporting an association between wildfire smoke exposure and asthma- and chronic obstructive pulmonary disease (COPD)-related healthcare utilization; however, there is less evidence of an increased risk of HAs or ERVs for other respiratory illnesses (for example, pneumonia, bronchitis) and these results are inconsistent (Youssouf et al., 2014; Adetona et al., 2016; Reid et al., 2016; Black et al., 2017; Skinner et al., 2022; Zhang et al., 2023; Jiao et al., 2024). These general observations are supported by the pooled analyses which have consistently determined significant associations for asthma and COPD, while the pooled associations for other respiratory illnesses are weaker and mixed or non-significant (summarized in Table 2) (Karanasiou et al., 2021; Barros et al., 2023).

Although the various pooled analyses summarized in this report mainly focused on same-day associations between wildfire smoke exposure and the health endpoint, there is evidence that increased healthcare utilization may be lagged by up to 3 days (Skinner et al., 2022). Additionally, increased risks for respiratory morbidity were commonly noted for women, children, and seniors compared to the risks observed for the general population (Borchers Arriagada et al., 2019; Kondo et al., 2019; Henry et al., 2021; Karanasiou et al., 2021; Skinner et al., 2022; Jiao et al., 2024).

2.3 Cardiovascular morbidity

The evidence base for cardiovascular morbidity is largely mixed and inconsistent (Youssouf et al., 2014; Adetona et al., 2016; Liu et al., 2016; Reid et al., 2016; Black et al., 2017; Chen et al., 2021; Karanasiou et al., 2021; Barros et al., 2023; Gould et al., 2023). Null or non-significant associations have generally been observed in the primary studies that have evaluated all-cardiovascular morbidity. However, significant associations have been reported for seniors (≥65 years) indicating an increased risk for this age group. Additionally, positive associations are more commonly reported for specific endpoints (for example, ischemic heart disease [IHD], hypertension, congestive heart disease [CHD], heart failure, and myocardial infarction [MI]), than for the aggregate outcome, though the pooled analyses do not consistently identify an association for the individual outcomes. From the three systematic reviews that included meta-analysis, the pooled analyses for cardiovascular morbidity for the various health endpoints and different measures of wildfire smoke exposure are summarized in Table 3, and largely considered same-day associations (Karanasiou et al., 2021; Barros et al., 2023; Gould et al., 2023). The null associations observed in many of the primary studies may be due to the lower occurrence of cardiovascular cases (or outcomes), especially among children and younger adults, compared to respiratory cases, limiting the ability to detect an association (Chen et al., 2021).

2.4 Reproductive and developmental effects

The effects of wildfires on reproductive and developmental outcomes are an active area of research. Recent systematic reviews identified that the most consistent evidence is for low birth weight and preterm birth, with most of the primary studies reporting positive associations with exposure to wildfire smoke or wildfire occurrences (Amjad et al., 2021; Evans et al., 2022; Gould et al., 2023; Zhang et al., 2023; Foo et al., 2024). From the two systematic reviews that included meta-analysis, there is some evidence for an association with low birth weight, which is summarized in Table 4 (Zhang et al., 2023; Foo et al., 2024). Notably, Foo et al. (2024) included more recent primary studies and did not observe significant associations. Additionally, there is evidence that timing of exposure, especially during the second or third trimesters, severity of the wildfires, and proximity to the wildfires may be influential factors in the observed adverse birth outcomes. The certainty in the evidence is limited due to a lack of information on maternal health status (for example, pre-existing conditions, nutritional status) for many of the primary studies, as these are known confounders for the endpoints. The primary investigations were also highly varied in terms of study design and exposure assessment methods, which limited the number of studies in the pooled analyses. Notably, the reproductive or developmental effects were associated with wildfire occurrence and not specifically limited to wildfire smoke exposure. This is an important consideration, as increased maternal stress leading to the adverse birth outcomes could result from both wildfire smoke exposure and occurrence. For other reproductive and developmental endpoints, such as size for gestational age, birth defects, gestational diabetes or hypertension, sex ratio, neonatal intensive care unit admission, or stillbirth, the systematic reviews identified that a small number of primary studies have been conducted per endpoint and the associations are inconsistent with most studies reporting non-significant or null associations (Amjad et al., 2021; Evans et al., 2022; Zhang et al., 2023; Foo et al., 2024).

2.5 Mental health

Given the potentially disruptive effects of wildfires and wildfire smoke on communities, a number of primary studies have evaluated mental health impacts and have identified increased rates of post-traumatic stress disorder (PTSD), anxiety, and depression in both children and adults with impacts that may persist months to years following a wildfire (Cianconi et al., 2020; Eisenman and Galway, 2022; Gao et al., 2023; Gould et al., 2023; Walinski et al., 2023). This evidence base is largely drawn from primary studies relying on surveys or self-reporting, as primary studies that have evaluated administrative data (for example, ERVs or physician visits for mental health conditions) have not detected associations (Reid et al., 2016; Eisenman and Galway, 2022). In addition, the evidence is inconsistent and limited for associations with wildfire smoke specifically, given the difficulties in differentiating the impacts attributable to smoke from those due to trauma associated with the wildfire occurrence (for example, potential loss of property or livelihood, physical threat, evacuation). Several possible pathways leading to mental health impacts from wildfires have been identified, including sleep disturbance, reduced physical activity, increased perceived risk, social isolation, evacuation or relocation, and loss of access to nature (Eisenman and Galway, 2022; Gould et al., 2023).

2.6 Mechanisms of toxicity of wildfire smoke

The exact mechanisms of how wildfire smoke causes health effects are not fully understood, although the evidence suggests they may be similar to those identified for ambient PM. Based on studies in humans and animals exposed to wildfire or wood smoke, several pathways have been proposed as mechanisms of toxicity underlying the adverse health effects (Adetona et al., 2016; Reid et al., 2016; Black et al., 2017; Cascio, 2018; Chen et al., 2021). Oxidative stress and systemic inflammation have been identified as key mechanisms, as many components of wildfire smoke are capable of activating the oxidative stress pathway. Inhalation of wildfire smoke induces production of reactive oxygen species (ROS) and elicits inflammatory responses in the lung, which can lead to systemic inflammation and other biochemical changes (for example, lipid peroxidation, depletion of antioxidants, cell cycle alteration, platelet activation, DNA damage). Additionally, inhaled wildfire smoke particles can interact with the receptors in the lung and activate the autonomous nervous system, resulting in changes in blood pressure and heart rhythm. Ultrafine particles (particles with a diameter less than 0.1 micrometres) and gases in the smoke may translocate through alveolar membranes and enter systemic circulation, which can result in biochemical and physiological changes, including endothelial dysfunction and injury. Lastly, wildfire smoke may compromise immune system function, including immune responses in the lung, increasing the risk of infection.

2.7 Disproportionately impacted populations

Although few studies have been designed to directly evaluate differential impacts or susceptibilities to wildfires and wildfire smoke, several groups have been identified as potentially being disproportionately impacted, including seniors, children, women, pregnant people, Indigenous populations, people living in remote areas, people with pre-existing health conditions, people with lower socio-economic status (SES), and wildland firefighters (Youssouf et al., 2014; Adetona et al., 2016; Liu et al., 2016; Reid et al., 2016; Borchers Arriagada et al., 2019; Kondo et al., 2019; Chen et al., 2021; Karanasiou et al., 2021; Thomas et al., 2022; Melton et al., 2023). Various factors contribute to these disproportionate risks, including biological and physiological differences due to lifestage and/or presence of a comorbidity, and increased likelihood of exposure to wildfires due to location or occupation. From an analysis of studies of wildfire smoke conducted in North America, increased risks of respiratory morbidity outcomes were identified for children, seniors, women and those with lower SES (Kondo et al., 2019). Studies in wildland firefighters have identified cardiorespiratory effects (for example, reduced lung function, airway and systemic inflammation) associated with short-term exposures to wildfire smoke (Yousouff et al., 2014; Black et al., 2017; Groot et., 2019; Chen et al., 2021), and there is an indication of increased risk of mental health impacts (for example, PTSD) in this occupational group (Groot et al., 2019; Walinski et al., 2023).

3.0 Conclusions and considerations

As wildfires are projected to increase in frequency and severity, the health effects of wildfire smoke will continue to be an active area of research. Based on published systematic reviews of the literature, there is strong and consistent evidence that wildfire smoke exposure is associated with an increased risk of premature mortality and adverse respiratory effects, including exacerbation of asthma and COPD. There is some evidence of an association between wildfire smoke exposure and increased risk of cardiovascular mortality and morbidity, including an increased risk of non-fatal effects in seniors. For reproductive and developmental effects and mental health impacts, further studies are needed to differentiate the effects attributable to wildfire smoke versus the effects resulting from the occurrence of wildfires. At present, there is some evidence of an association between wildfire smoke and reproductive and developmental effects (for example, low birth weight) and limited evidence on the mental health impacts of wildfire smoke specifically. With respect to other health outcomes, there is emerging evidence of potential associations between exposure to wildfire smoke and wildfires and risk of neurological effects (for example, cognitive deficits), cancer, and skin and eye conditions (Gould et al., 2023; Zhang et al., 2023). Also, there is limited evidence of the long-term effects of wildfire smoke exposure, which is attributable to the episodic nature of wildfires, seasonal and spatial variability in wildfire smoke exposure, and the difficulties in differentiating wildfire-PM_2.5 from PM_2.5 from all sources (Gao et al., 2023; Gould et al., 2023). There is a need for a better characterization of the lagged effects of wildfire smoke exposure that have been observed, which will help to better understand the cumulative impacts on health care utilization (Skinner et al., 2022; Gould et al., 2023). As such, additional, well-designed studies are needed to address these knowledge gaps and to more fully understand the totality of the health effects of wildfire smoke. Since this evidence synthesis is based on published systematic reviews, it may not include the most recent primary studies of the health effects of wildfire smoke.

The literature base identified some groups that may be disproportionately impacted by wildfires and wildfire smoke, including seniors, children, women, pregnant people, Indigenous populations, people living in remote areas, people with pre-existing health conditions, people with lower SES, and wildland firefighters. Additional research will also help to better understand the groups that may be disproportionately impacted by wildfires and wildfire smoke.

As the understanding of the health effects of wildfire smoke develops, there are a few considerations that should be taken into account. With respect to exposure assessment, there are numerous challenges; for example, monitoring methods cannot distinguish between sources of PM, methods based on proximity to wildfires may not represent smoke exposure, and use of smoky versus non-smoky days is a coarse metric that cannot be used to quantify the risk per unit of exposure. Furthermore, the diverse approaches to exposure assessment can limit the ability to quantitatively synthesize the results from the primary studies. Additionally, behaviour changes associated with exposure to wildfire smoke (for example, remaining indoors, wearing masks, relocation) will alter individual exposures and, if unaccounted for, would bias the exposure-response relationship. Other important areas of investigation include an understanding of the differential effects of ambient PM_2.5 and wildfire-PM_2.5, the health effects of the other components of wildfire smoke, and the combined effects of wildfire smoke and heat, as smoke and heat events may occur simultaneously.

Appendix: Methodology

Approach

The objective of the report is to provide a concise weight-of-evidence review of health outcomes associated with exposure to wildfire smoke. To facilitate this, an umbrella review approach was taken. Umbrella reviews systematically search, organize, and evaluate existing evidence from systematic reviews with or without meta-analyses (Aromataris et al., 2015).

Search strategy and article selection

Literature searches were conducted by a Health Canada librarian in three databases – Ovid Embase, Ovid MEDLINE, and Global Health – and covered the period from January 1, 2013 to November 6, 2023. The detailed search strategy is provided in Tables A1, A2 and A3. There were no limitations based on language of publication, though only articles in English were retrieved. The references identified from the literature search were screened first by title and abstract, and then underwent full-text screening for eligibility. The review process was managed using DistillerSR (Evidence Partners, Ottawa, ON).

To be considered for inclusion in the report, the review articles needed to employ systematic review techniques and evaluate the health effects of wildfires or wildfire smoke. Narrative reviews (that is, non-systematic reviews) were excluded. Review articles that considered non-wildfire smoke (for example, burning of built environment or agricultural waste; indoor biomass burning) were excluded. Of the full-text review articles that were screened, articles were excluded for: not being specific to wildfires or wildfire smoke (n = 10), narrative reviews (n = 6), review was not based on epidemiological studies (n = 2), and record was correspondence (n = 1). Additionally, for the quantitative syntheses, pooled risk estimates that combined wildfire smoke with non-wildfire smoke were excluded.

The study selection process is outlined in Figure A1. Overall, 26 review articles were included within the evidence synthesis, which included three articles identified by peer-reviewers that were not captured by the initial literature search but otherwise met the inclusion criteria.

Data extraction

For the systematic reviews with meta-analysis that met the inclusion criteria, the following data was extracted: first author's name, year of publication, number of studies included in meta-analysis, health outcome, wildfire smoke exposure, and summary risk estimate with corresponding 95% confidence interval.

Figure A1 : Descriptive text

Figure A1 depicts the flow of information through the different phases of a systematic review and maps out the number of records identified, included and excluded, and the reasons for exclusions. For the evidence review: 379 records were identified through database searching, of which 187 records remained after the duplicates were removed. 187 records were then screened for title and abstract screening, at which point 145 records were excluded and the full-text of 42 review articles were assessed for eligibility. Of these full-text articles, 19 were excluded with reason. 3 articles were identified from external review. In total, 26 articles were included in the evidence synthesis.

References

Adetona O, Reinhardt TE, Domitrovich J, et al. Review of the health effects of wildland fire smoke on wildland firefighters and the public. Inhal Toxicol. 2016;28(3):95-139. doi:10.3109/08958378.2016.1145771

Amjad S, Chojecki D, Osornio-Vargas A, Ospina MB. Wildfire exposure during pregnancy and the risk of adverse birth outcomes: A systematic review. Environ Int. 2021;156:106644. doi:10.1016/j.envint.2021.106644

Andreae MO, Merlet P. Emission of trace gases and aerosols from biomass burning, Global Biogeochem. Cycles 2001;15:955-966. doi:10.1029/2000GB001382.

Barros B, Oliveira M, Morais S. Continent-based systematic review of the short-term health impacts of wildfire emissions. J Toxicol Environ Health B Crit Rev. 2023;26(7):387-415. doi:10.1080/10937404.2023.2236548

Black C, Tesfaigzi Y, Bassein JA, Miller LA. Wildfire smoke exposure and human health: Significant gaps in research for a growing public health issue. Environ Toxicol Pharmacol. 2017;55:186-195. doi:10.1016/j.etap.2017.08.022

Borchers Arriagada N, Horsley JA, Palmer AJ, Morgan GG, Tham R, Johnston FH. Association between fire smoke fine particulate matter and asthma-related outcomes: Systematic review and meta-analysis. Environ Res. 2019;179(Pt A):108777. doi:10.1016/j.envres.2019.108777

Cascio WE. Wildland fire smoke and human health. Sci Total Environ. 2018;624:586-595. doi:10.1016/j.scitotenv.2017.12.086

Chen H, Samet JM, Bromberg PA, Tong H. Cardiovascular health impacts of wildfire smoke exposure. Part Fibre Toxicol. 2021;18(1):2. Published 2021 Jan 7. doi:10.1186/s12989-020-00394-8

Cianconi P, Betrò S, Janiri L. The Impact of Climate Change on Mental Health: A Systematic Descriptive Review. Front Psychiatry. 2020;11:74. Published 2020 Mar 6. doi:10.3389/fpsyt.2020.00074

Eisenman DP, Galway LP. The mental health and well-being effects of wildfire smoke: a scoping review. BMC Public Health. 2022;22(1):2274. Published 2022 Dec 5. doi:10.1186/s12889-022-14662-z

Evans J, Bansal A, Schoenaker DAJM, Cherbuin N, Peek MJ, Davis DL. Birth Outcomes, Health, and Health Care Needs of Childbearing Women following Wildfire Disasters: An Integrative, State-of-the-Science Review. Environ Health Perspect. 2022;130(8):86001. doi:10.1289/EHP10544

Foo D, Stewart R, Heo S, et al. Wildfire smoke exposure during pregnancy and perinatal, obstetric, and early childhood health outcomes: A systematic review and meta-analysis. Environ Res. 2024;241:117527. doi:10.1016/j.envres.2023.117527

Gao Y, Huang W, Yu P, et al. Long-term impacts of non-occupational wildfire exposure on human health: A systematic review. Environ Pollut. 2023;320:121041. doi:10.1016/j.envpol.2023.121041

Gould CF, Heft-Neal S, Prunicki M, et al. Health Effects of Wildfire Smoke Exposure. Annu Rev Med. Published online September 22, 2023. doi:10.1146/annurev-med-052422-020909

Groot E, Caturay A, Khan Y, Copes R. A systematic review of the health impacts of occupational exposure to wildland fires. Int J Occup Med Environ Health. 2019;32(2):121-140. doi:10.13075/ijomeh.1896.01326

Health Canada. 2022. Canadian health science assessment for fine particulate matter (PM2.5). Ottawa, Ontario: Health Canada. Cat. No. H144-100/2022E-PDF. http://www.publications.gc.ca/pub?id=9.907208&sl=0

Henry S, Ospina MB, Dennett L, Hicks A. Assessing the Risk of Respiratory-Related Healthcare Visits Associated with Wildfire Smoke Exposure in Children 0-18 Years Old: A Systematic Review. Int J Environ Res Public Health. 2021;18(16):8799. Published 2021 Aug 20. doi:10.3390/ijerph18168799

Jiao A, Headon K, Han T, et al. Associations between short-term exposure to wildfire particulate matter and respiratory outcomes: A systematic review. Sci Total Environ. 2024;907:168134. doi:10.1016/j.scitotenv.2023.168134.

Karanasiou A, Alastuey A, Amato F, et al. Short-term health effects from outdoor exposure to biomass burning emissions: A review. Sci Total Environ. 2021;781:146739. doi:10.1016/j.scitotenv.2021.146739

Kondo MC, De Roos AJ, White LS, et al. Meta-Analysis of Heterogeneity in the Effects of Wildfire Smoke Exposure on Respiratory Health in North America. Int J Environ Res Public Health. 2019;16(6):960. Published 2019 Mar 18. doi:10.3390/ijerph16060960

Liu JC, Pereira G, Uhl SA, Bravo MA, Bell ML. A systematic review of the physical health impacts from non-occupational exposure to wildfire smoke. Environ Res. 2015;136:120-132. doi:10.1016/j.envres.2014.10.015

Matz CJ, Egyed M, Xi G, et al. Health impact analysis of PM_2.5 from wildfire smoke in Canada (2013-2015, 2017-2018). Sci Total Environ. 2020;725:138506. doi:10.1016/j.scitotenv.2020.138506

Melton CC, De Fries CM, Smith RM, Mason LR. Wildfires and Older Adults: A Scoping Review of Impacts, Risks, and Interventions. Int J Environ Res Public Health. 2023;20(13):6252. Published 2023 Jun 29. doi:10.3390/ijerph20136252

Reid CE, Brauer M, Johnston FH, Jerrett M, Balmes JR, Elliott CT. Critical Review of Health Impacts of Wildfire Smoke Exposure. Environ Health Perspect. 2016;124(9):1334-1343. doi:10.1289/ehp.1409277

Skinner R, Luther M, Hertelendy AJ, et al. A Literature Review on the Impact of Wildfires on Emergency Departments: Enhancing Disaster Preparedness. Prehosp Disaster Med. 2022;37(5):657-664. doi:10.1017/S1049023X22001054

Sun Q, Miao C, Hanel M, et al. Global heat stress on health, wildfires, and agricultural crops under different levels of climate warming. Environ Int. 2019;128:125-136. doi:10.1016/j.envint.2019.04.025

Thomas AS, Escobedo FJ, Sloggy MR, Sánchez JJ. A burning issue: Reviewing the socio-demographic and environmental justice aspects of the wildfire literature. PLoS One. 2022;17(7):e0271019. Published 2022 Jul 28. doi:10.1371/journal.pone.0271019

Urbanski SP, Hao WM, Baker S. Chemical Composition of Wildland Fire Emissions. In Developments in Environmental Science, Bytnerowicz, A.; Arbaugh, M. J.; Riebau, A. R.; Andersen, C., Eds.; Elsevier, 2008; Chapter 4, Vol. 8, pp 79−107.

Walinski A, Sander J, Gerlinger G, Clemens V, Meyer-Lindenberg A, Heinz A. The Effects of Climate Change on Mental Health. Dtsch Arztebl Int. 2023;120(8):117-124. doi:10.3238/arztebl.m2022.0403

Wotton BM, Flannigan MD, Marshall GA. Potential climate change impacts on fire intensity and key wildfire suppression thresholds in Canada. Environ. Res. Lett. 2017;12:095003. doi: 10.1088/1748-9326/aa7e6e

Youssouf H, Liousse C, Roblou L, et al. Non-accidental health impacts of wildfire smoke. Int J Environ Res Public Health. 2014;11(11):11772-11804. Published 2014 Nov 14. doi:10.3390/ijerph111111772

Zhang Y, Tingting Y, Huang W, et al. Health Impacts of Wildfire Smoke on Children and Adolescents: A Systematic Review and Meta-analysis. Curr Environ Health Rep. Published online December 1, 2023. doi:10.1007/s40572-023-00420-9