Evidence map›Paper›PMID 40324806›Full record

ArticleCMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne2025

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

Hong Chen, Jay S Kaufman, Chen Chen, Jun Wang, Allison Maier, Adam van Dijk, Nancy Slipp, Juwel Rana, Elaina MacIntyre, Yushan Su and 2 more

Abstract read
PubMed Full text at PMC Publisher
In one paragraph

Article in CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 9 papers, 1 of them a synthesis that pooled it.

0numbers the graph read from it
0cells of the map it votes in
9citing papers in PubMed, 1 pooled it
–field-weighted citation impact
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

9 citing papers in PubMed, 1 synthesis or guideline pooled it.

  1. Pooled it
  2. Article
  3. Disparities in fine particulate matter (PMEnvironmental research, health : ERH · 2026
    Article
  4. Mechanisms and therapeutic strategies of asthma: from bench to bedside.Signal transduction and targeted therapy · 2026
    Review
  5. Article
  6. Article
  7. Article
  8. CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne · 2025
    Article
  9. Wildfire smoke air pollution: new approaches needed to protect people affected.CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne · 2025
    Article
4 · The record

Corrections and comments

5 · Who and what money

Authors and funding

12 authors.

Hong ChenEnvironmental Health Science and Research Bureau (H. Chen), Health Canada, Ottawa, Ont.; Public Health Ontario (H. Chen, Wang, MacIntyre, Kim); ICES Central (H. Chen); Dalla Lana School of Public Health (H. Chen, MacIntyre, Kim), University of Toronto, Toronto, Ont.; Department of Epidemiology and Biostatistics (Kaufman, Rana), McGill University, Montréal, Que.; Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California, San Diego, La Jolla, Calif.; Kingston, Frontenac and Lennox & Addington (KFL&A) Public Health (Maier, van Dijk, Slipp), Kingston, Ont.; Ministry of the Environment, Conservation and Parks (Su), Toronto, Ont. hong.chen@oahpp.ca.
Jay S KaufmanEnvironmental Health Science and Research Bureau (H. Chen), Health Canada, Ottawa, Ont.; Public Health Ontario (H. Chen, Wang, MacIntyre, Kim); ICES Central (H. Chen); Dalla Lana School of Public Health (H. Chen, MacIntyre, Kim), University of Toronto, Toronto, Ont.; Department of Epidemiology and Biostatistics (Kaufman, Rana), McGill University, Montréal, Que.; Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California, San Diego, La Jolla, Calif.; Kingston, Frontenac and Lennox & Addington (KFL&A) Public Health (Maier, van Dijk, Slipp), Kingston, Ont.; Ministry of the Environment, Conservation and Parks (Su), Toronto, Ont.
Chen ChenEnvironmental Health Science and Research Bureau (H. Chen), Health Canada, Ottawa, Ont.; Public Health Ontario (H. Chen, Wang, MacIntyre, Kim); ICES Central (H. Chen); Dalla Lana School of Public Health (H. Chen, MacIntyre, Kim), University of Toronto, Toronto, Ont.; Department of Epidemiology and Biostatistics (Kaufman, Rana), McGill University, Montréal, Que.; Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California, San Diego, La Jolla, Calif.; Kingston, Frontenac and Lennox & Addington (KFL&A) Public Health (Maier, van Dijk, Slipp), Kingston, Ont.; Ministry of the Environment, Conservation and Parks (Su), Toronto, Ont.
Jun WangEnvironmental Health Science and Research Bureau (H. Chen), Health Canada, Ottawa, Ont.; Public Health Ontario (H. Chen, Wang, MacIntyre, Kim); ICES Central (H. Chen); Dalla Lana School of Public Health (H. Chen, MacIntyre, Kim), University of Toronto, Toronto, Ont.; Department of Epidemiology and Biostatistics (Kaufman, Rana), McGill University, Montréal, Que.; Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California, San Diego, La Jolla, Calif.; Kingston, Frontenac and Lennox & Addington (KFL&A) Public Health (Maier, van Dijk, Slipp), Kingston, Ont.; Ministry of the Environment, Conservation and Parks (Su), Toronto, Ont.
Allison MaierEnvironmental Health Science and Research Bureau (H. Chen), Health Canada, Ottawa, Ont.; Public Health Ontario (H. Chen, Wang, MacIntyre, Kim); ICES Central (H. Chen); Dalla Lana School of Public Health (H. Chen, MacIntyre, Kim), University of Toronto, Toronto, Ont.; Department of Epidemiology and Biostatistics (Kaufman, Rana), McGill University, Montréal, Que.; Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California, San Diego, La Jolla, Calif.; Kingston, Frontenac and Lennox & Addington (KFL&A) Public Health (Maier, van Dijk, Slipp), Kingston, Ont.; Ministry of the Environment, Conservation and Parks (Su), Toronto, Ont.
Adam van DijkEnvironmental Health Science and Research Bureau (H. Chen), Health Canada, Ottawa, Ont.; Public Health Ontario (H. Chen, Wang, MacIntyre, Kim); ICES Central (H. Chen); Dalla Lana School of Public Health (H. Chen, MacIntyre, Kim), University of Toronto, Toronto, Ont.; Department of Epidemiology and Biostatistics (Kaufman, Rana), McGill University, Montréal, Que.; Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California, San Diego, La Jolla, Calif.; Kingston, Frontenac and Lennox & Addington (KFL&A) Public Health (Maier, van Dijk, Slipp), Kingston, Ont.; Ministry of the Environment, Conservation and Parks (Su), Toronto, Ont.
Nancy SlippEnvironmental Health Science and Research Bureau (H. Chen), Health Canada, Ottawa, Ont.; Public Health Ontario (H. Chen, Wang, MacIntyre, Kim); ICES Central (H. Chen); Dalla Lana School of Public Health (H. Chen, MacIntyre, Kim), University of Toronto, Toronto, Ont.; Department of Epidemiology and Biostatistics (Kaufman, Rana), McGill University, Montréal, Que.; Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California, San Diego, La Jolla, Calif.; Kingston, Frontenac and Lennox & Addington (KFL&A) Public Health (Maier, van Dijk, Slipp), Kingston, Ont.; Ministry of the Environment, Conservation and Parks (Su), Toronto, Ont.
Juwel RanaEnvironmental Health Science and Research Bureau (H. Chen), Health Canada, Ottawa, Ont.; Public Health Ontario (H. Chen, Wang, MacIntyre, Kim); ICES Central (H. Chen); Dalla Lana School of Public Health (H. Chen, MacIntyre, Kim), University of Toronto, Toronto, Ont.; Department of Epidemiology and Biostatistics (Kaufman, Rana), McGill University, Montréal, Que.; Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California, San Diego, La Jolla, Calif.; Kingston, Frontenac and Lennox & Addington (KFL&A) Public Health (Maier, van Dijk, Slipp), Kingston, Ont.; Ministry of the Environment, Conservation and Parks (Su), Toronto, Ont.
Elaina MacIntyreEnvironmental Health Science and Research Bureau (H. Chen), Health Canada, Ottawa, Ont.; Public Health Ontario (H. Chen, Wang, MacIntyre, Kim); ICES Central (H. Chen); Dalla Lana School of Public Health (H. Chen, MacIntyre, Kim), University of Toronto, Toronto, Ont.; Department of Epidemiology and Biostatistics (Kaufman, Rana), McGill University, Montréal, Que.; Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California, San Diego, La Jolla, Calif.; Kingston, Frontenac and Lennox & Addington (KFL&A) Public Health (Maier, van Dijk, Slipp), Kingston, Ont.; Ministry of the Environment, Conservation and Parks (Su), Toronto, Ont.
Yushan SuEnvironmental Health Science and Research Bureau (H. Chen), Health Canada, Ottawa, Ont.; Public Health Ontario (H. Chen, Wang, MacIntyre, Kim); ICES Central (H. Chen); Dalla Lana School of Public Health (H. Chen, MacIntyre, Kim), University of Toronto, Toronto, Ont.; Department of Epidemiology and Biostatistics (Kaufman, Rana), McGill University, Montréal, Que.; Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California, San Diego, La Jolla, Calif.; Kingston, Frontenac and Lennox & Addington (KFL&A) Public Health (Maier, van Dijk, Slipp), Kingston, Ont.; Ministry of the Environment, Conservation and Parks (Su), Toronto, Ont.
JinHee KimEnvironmental Health Science and Research Bureau (H. Chen), Health Canada, Ottawa, Ont.; Public Health Ontario (H. Chen, Wang, MacIntyre, Kim); ICES Central (H. Chen); Dalla Lana School of Public Health (H. Chen, MacIntyre, Kim), University of Toronto, Toronto, Ont.; Department of Epidemiology and Biostatistics (Kaufman, Rana), McGill University, Montréal, Que.; Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California, San Diego, La Jolla, Calif.; Kingston, Frontenac and Lennox & Addington (KFL&A) Public Health (Maier, van Dijk, Slipp), Kingston, Ont.; Ministry of the Environment, Conservation and Parks (Su), Toronto, Ont.
Tarik BenmarhniaEnvironmental Health Science and Research Bureau (H. Chen), Health Canada, Ottawa, Ont.; Public Health Ontario (H. Chen, Wang, MacIntyre, Kim); ICES Central (H. Chen); Dalla Lana School of Public Health (H. Chen, MacIntyre, Kim), University of Toronto, Toronto, Ont.; Department of Epidemiology and Biostatistics (Kaufman, Rana), McGill University, Montréal, Que.; Scripps Institution of Oceanography (C. Chen, Benmarhnia), University of California, San Diego, La Jolla, Calif.; Kingston, Frontenac and Lennox & Addington (KFL&A) Public Health (Maier, van Dijk, Slipp), Kingston, Ont.; Ministry of the Environment, Conservation and Parks (Su), Toronto, Ont.

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

backgroundDuring 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.

methodsWe 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.

resultsAfter 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).

interpretationThe 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.

Indexed as

AsthmaEmergency Service, HospitalMyocardial IschemiaSmokeWildfiresAdolescentAdultAgedChildChild, PreschoolFemaleHumansInterrupted Time Series AnalysisMaleMiddle AgedOntarioSmoke

Identifiers

PMID40324806
PMCPMC12052414

What OpenQuestion holds

Textmetadata
LicenceCC BY-NC-ND
Read underepoch 390

Registered trials

None linked

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.