How do wildfires create toxic haze and what does it do to your health?

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1. 1

   Cardiopulmonary hospitalization risks from wildfire-specific and non-wildfire PM2.5 in 20 US states.

   Nature communications (Zhang et al.)Published Sep 17, 2026Checked Oct 15, 2026

   “Using a self-controlled design, we examine associations between 2-year average wildfire-specific and non-wildfire PM2.5 and cardiopulmonary hospitalization risks across 20 US states during 2006-2019. Per 1 µg/m3 increase, wildfire-specific PM2.5 is associated with significantly higher hospitalization risks for all cardiopulmonary diseases, with relative risks ranging from 10% for heart failure to 16% for asthma. In contrast, a 1-µg/m3 increase in non-wildfire PM2.5 is associated with smaller risk elevations, ranging from 4.7% for chronic obstructive pulmonary disease to 8.5% for hypertension. Stronger associations for both wildfire-specific and non-wildfire PM2.5 are observed among minorities, metropolitan residents, those with fewer years of education, and more deprived communities. Overall, at an equivalent concentration increase, long-term exposure to wildfire-specific PM2.5 poses greater cardiopulmonary hospitalization risks than non-wildfire PM2.5, underscoring wildfire smoke as a growing public health threat that requires targeted mitigation alongside conventional air quality control strategies.”

2. 2

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

   Nature Communications (Aguilera et al.)Published Mar 5, 2021Checked Oct 15, 2026

   “Wildfires are becoming more frequent and destructive in a changing climate. Fine particulate matter, PM 2.5 , in wildfire smoke adversely impacts human health. Recent toxicological studies suggest that wildfire particulate matter may be more toxic than equal doses of ambient PM 2.5 . Air quality regulations however assume that the toxicity of PM 2.5 does not vary across different sources of emission. Assessing whether PM 2.5 from wildfires is more or less harmful than PM 2.5 from other sources is a pressing public health concern. Here, we isolate the wildfire-specific PM 2.5 using a series of statistical approaches and exposure definitions. We found increases in respiratory hospitalizations ranging from 1.3 to up to 10% with a 10 μg m −3 increase in wildfire-specific PM 2.5 , compared to 0.67 to 1.3% associated with non-wildfire PM 2.5 . Our conclusions point to the need for air quality policies to consider the variability in PM 2.5 impacts on human health according to the sources of emission.”

3. 3

   Critical Review of Health Impacts of Wildfire Smoke Exposure

   Environmental Health Perspectives (Reid et al.)Published Apr 15, 2016Checked Oct 15, 2026

   “Consistent evidence from a large number of studies indicates that wildfire smoke exposure is associated with respiratory morbidity with growing evidence supporting an association with all-cause mortality. More research is needed to clarify which causes of mortality may be associated with wildfire smoke, whether cardiovascular outcomes are associated with wildfire smoke, and if certain populations are more susceptible.”

4. 4

   Health Effects of Wildfire Smoke Exposure

   Annual Review of Medicine (Gould et al.)Published Sep 22, 2023Checked Oct 15, 2026

   “We review current knowledge on the trends and drivers of global wildfire activity, advances in the measurement of wildfire smoke exposure, and evidence on the health effects of this exposure. We describe methodological issues in estimating the causal effects of wildfire smoke exposures on health and quantify their importance, emphasizing the role of nonlinear and lagged effects. We conduct a systematic review and meta-analysis of the health effects of wildfire smoke exposure, finding positive impacts on all-cause mortality and respiratory hospitalizations but less consistent evidence on cardiovascular morbidity. We conclude by highlighting priority areas for future research, including leveraging recently developed spatially and temporally resolved wildfire-specific ambient air pollution data to improve estimates of the health effects of wildfire smoke exposure.”

5. 5

   The mental health and well-being effects of wildfire smoke: a scoping review

   BMC Public Health (Eisenman & Galway)Published Dec 5, 2022Checked Oct 15, 2026

   “Our review suggests that exposure to wildfire smoke may have mental health impacts, particularly in episodes of chronic and persistent smoke events, but the evidence is inconsistent and limited. Qualitative studies disclose a wider range of impacts across multiple mental health and well-being domains. The potential pathways connecting wildfire smoke with mental health and well-being operate at multiple interacting levels including individual, social and community networks, living and working conditions, and ecological levels. Priorities for future research include: 1) applying more rigorous methods; 2) differentiating between mental illness and emotional well-being; 3) studying chronic, persistent or repeated smoke events; 4) identifying the contextual factors that set the stage for mental health and well-being effects, and 5) identifying the causal processes that link wildfire smoke to mental health and well-being effects.”

6. 6

   Assessing the Evidence for Differential Health Effects of Wildfire Smoke Across Fires and Populations: A Critical Review of Recent Studies.

   Current environmental health reports (Reid & Magzamen)Published Jun 30, 2026Checked Oct 15, 2026

   “Although some recent studies have documented larger health risks from wildfire-derived as compared to non-wildfire-derived PM2.5, we document how further research could evaluate whether these findings are confounded by type of fuel burned, due to methodological concerns, or are true. We also conclude that more research is necessary to elucidate potential differences in health risks of constituents of wildfire smoke other than PM2.5 or from burning of different fuels. Wildfire smoke is projected to continue to increase. We encourage future research to move away from further documentation of respiratory health impacts of wildfire smoke, which has been very well established, into studies of other health endpoints that have been less well studied to date, more exploration into health effects from wildfire smoke constituents other than PM2.5 and from different types of fires (i.e., wildland urban interface (WUI) fires versus wildland fires), and additional exploration of remaining uncertainties with a goal of further supporting public health protection from wildfire smoke.”

7. 7

   Wildfire smoke and health: current evidence, mechanisms, and future challenges.

   Lancet (London, England) (Chen et al.)Published Sep 8, 2026Checked Oct 15, 2026

   “Although previous studies have shed light on health effects of wildfire smoke, crucial research gaps persist, including long-term health effects, interactions with pre-existing health conditions, and health disparities. Closing these gaps is vital to enhancing the ability to safeguard public health during wildfire events and to formulate effective strategies for prevention, mitigation, and response. This Review synthesises global evidence on the trends, health effects, and physical and chemical characteristics of wildfire smoke, exploring potential biological mechanisms and challenges in health risk assessment. Acknowledging the global impact of wildfires and their health effects is essential for mitigating environmental, social, and economic challenges. Safeguarding public health requires an interdisciplinary approach to comprehensively address the public health burden from wildfires. This integrated strategy is essential to systematically assess and mitigate the substantial public health burden posed by wildfires, as well as promoting resilience and sustainable solutions for affected communities.”

8. 8

   'Nowhere to escape' - Indonesians share footage of orange haze blanketing towns

   BBC NewsPublished Oct 15, 2026Checked Oct 15, 2026

   “Thick orange smog descended on the Indonesian city of Palangka Raya as wildfires continue raging nearby.”