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SOS! Summer of Smoke: a retrospective cohort study examining the cardiorespiratory impacts of a severe and prolonged wildfire season in Canada’s high subarctic
  1. Courtney Howard1,
  2. Caren Rose2,
  3. Warren Dodd3,
  4. Katherine Kohle4,
  5. Craig Scott5,
  6. Patrick Scott6,
  7. Ashlee Cunsolo7,
  8. James Orbinski8
  1. 1 Cumming School of Medicine, University of Calgary, Yellowknife, Northwest Territories, Canada
  2. 2 School of Population and Public Health, The University of British Columbia, Vancouver, British Columbia, Canada
  3. 3 School of Public Health and Health Systems, University of Waterloo, Waterloo, Ontario, Canada
  4. 4 Northwest Territories Health and Social Services, Yellowknife, Northwest Territories, Canada
  5. 5 Climate Change Initiatives, Ecology North, Yellowknife, Northwest Territories, Canada
  6. 6 Jordanstone College of Art and Design, University of Dundee, Dundee, UK
  7. 7 Labrador Institute, Memorial University of Newfoundland, Saint John's, Newfoundland, Canada
  8. 8 Dahdaleh Institute for Global Health Research, York University, Toronto, Ontario, Canada
  1. Correspondence to Dr Courtney Howard; doctorswithinborderscanada{at}


Objectives To determine healthcare service utilisation for cardiorespiratory presentations and outpatient salbutamol dispensation associated with 2.5 months of severe, unabating wildfire smoke in Canada’s high subarctic.

Design A retrospective cohort study using hospital, clinic, pharmacy and environmental data analysed using Poisson regression.

Setting Territorial referral hospital and clinics in Yellowknife, Northwest Territories, Canada.

Participants Individuals from Yellowknife and surrounding communities presenting for care between 2012 and 2015.

Main outcome measures Emergency room (ER) presentations, hospital admissions and clinic visits for cardiorespiratory events, and outpatient salbutamol prescriptions

Results The median 24-hour mean particulate matter (PM2.5) was fivefold higher in the summer of 2014 compared with 2012, 2013 and 2015 (median=30.8 µg/m3), with the mean peaking at 320.3 µg/m3. A 10 µg/m3 increase in PM2.5 was associated with an increase in asthma-related (incidence rate ratio (IRR) (95% CI): 1.11 (1.07, 1.14)) and pneumonia-related ER visits (IRR (95% CI): 1.06 (1.02, 1.10)), as well as an increase in chronic obstructive pulmonary disease hospitalisations (IRR (95% CI): 1.11 (1.02, 1.20). Compared with 2012 and 2013, salbutamol dispensations in 2014 increased by 48%; clinic visits for asthma, pneumonia and cough increased; ER visits for asthma doubled, with the highest rate in females, in adults aged ≥40 years and in Dene people, while pneumonia increased by 57%, with higher rates in males, in individualsaged <40 years and in Inuit people. Cardiac variables were unchanged.

Conclusions Severe wildfires in 2014 resulted in extended poor air quality associated with increases in health resource utilization; some impacts were seen disproportionately among vulnerable populations, such as children and Indigenous individuals. Public health advisories asking people to stay inside were inadequately protective, with compliance possibly impacted by the prolonged exposure. Future research should investigate use of at-home air filtration systems, clean-air shelters and public health messaging which addresses mental health and supports physical activity.

  • asthma
  • accident & emergency medicine
  • public health

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  • Contributors CH: Study conception and design, building of team, grant application, review of qualitative interview content, collection of quantitative data, study write-up and editing. CR: Study design, quantitative data analysis, study write-up and editing. WD: Qualitative data collection, qualitative data analysis, consultation on statistical analyses of quantitative data, review and editing of study write-up. KK: Study conception and design, grant application, collection of quantitative data and study editing. CS: Study conception and design, grant application, project management and community outreach, and study editing. PS: Study conception and design, grant application, interview design and qualitative information and study editing. AC: Study design, qualitative interview design and study editing. JO: Study design, grant application, consultation on quantitative analysis, review and editing of study write-up, and oversight of the project.

  • Funding This project was funded by a grant from Health Canada’s Climate Change and Health Adaptation Program for First Nations and Inuit Communities (Grant Number N/A).

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval This project was reviewed and approved by the Stanton Territorial Hospital Ethics Board and Wilfrid Laurier University Research Ethics Board (REB #4700), as well as by the Aurora Research Institute (license numbers 15733; 15801).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available upon reasonable request. The data used in this study includes publicly available air monitoring data, and hospital, and clinic records that were requested from the relevant authorities. Pharmaceutical data was collected from local pharmacies. The data is held by the epidemiologist on our team and is available upon reasonable request.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.