Worldwide heavy oil and bitumen deposits amount to 9 trillion barrels of oil distributed in over 280 basins around the world1, with Canada home to oil sands deposits of 1.7 trillion barrels2. The global development of this resource and the increase in oil production from oil sands has caused environmental concerns over the presence of toxic compounds in nearby ecosystems3,4 and acid deposition5,6. The contribution of oil sands exploration to secondary organic aerosol formation, an important component of atmospheric particulate matter that affects air quality and climate7, remains poorly understood. Here we use data from airborne measurements over the Canadian oil sands, laboratory experiments and a box-model study to provide a quantitative assessment of the magnitude of secondary organic aerosol production from oil sands emissions. We find that the evaporation and atmospheric oxidation of low-volatility organic vapours from the mined oil sands material is directly responsible for the majority of the observed secondary organic aerosol mass. The resultant production rates of 45–84 tonnes per day make the oil sands one of the largest sources of anthropogenic secondary organic aerosols in North America. Heavy oil and bitumen account for over ten per cent of global oil production today8, and this figure continues to grow9. Our findings suggest that the production of the more viscous crude oils could be a large source of secondary organic aerosols in many production and refining regions worldwide, and that such production should be considered when assessing the environmental impacts of current and planned bitumen and heavy oil extraction projects globally.

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We thank the National Research Council of Canada flight crew of the Convair-580, the technical support staff of the Air Quality Research Division, S. Cober for the management of the study, and the community of Fort McKay for the support of the Oski ôtin ground site at Fort McKay. The project was supported by the Clean Air Regulatory Agenda and the Joint Oil Sands Monitoring program.

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  1. Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario M3H 5T4, Canada

    • John Liggio
    • , Shao-Meng Li
    • , Katherine Hayden
    • , Craig Stroud
    • , Andrea Darlington
    • , Mark Gordon
    • , Patrick Lee
    • , Peter Liu
    • , Amy Leithead
    • , Samar G. Moussa
    • , Danny Wang
    • , Jason O’Brien
    • , Richard L. Mittermeier
    • , Jeffrey R. Brook
    • , Gang Lu
    • , Ralf M. Staebler
    • , Yuemei Han
    • , Paul A. Makar
    •  & Junhua Zhang
  2. Department of Chemistry, University of Calgary, Calgary, Alberta T2N 1N4, Canada

    • Youssef M. Taha
    • , Travis W. Tokarek
    •  & Hans D. Osthoff
  3. Department of Chemical & Environmental Engineering, Yale University, New Haven, Connecticut 06520-8267, USA

    • Brian D. Drollette
    • , Desiree L. Plata
    •  & Drew R. Gentner


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All authors contributed to the collection of observations in the field, in the laboratory or the development of the box model. J.L. and S.-M.L. wrote the paper with input from all co-authors. S.-M.L. designed and directed the flights. Y.M.T. and C.S. conducted the box modelling work with input from J.L. D.R.G., D.P., B.D.D. and P.L. provided bitumen volatility distributions.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to John Liggio or Shao-Meng Li.

The data used are available on the Canada-Alberta Oil Sands Environmental Monitoring Information Portal (http://jointoilsandsmonitoring.ca/default.asp?n=5F73C7C9-1&lang=en).

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    This file contains Supplementary Methods, Supplementary Discussion, Supplementary Tables 1-2 and Supplementary References.

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