An increasing role for solvent emissions and implications for future measurements of volatile organic compounds: Solvent emissions of VOCs

Alastair C. Lewis*, Jim R. Hopkins, David C. Carslaw, Jacqueline F. Hamilton, Beth S. Nelson, Gareth Stewart, James Dernie, Neil Passant, Tim Murrells

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Volatile organic compounds (VOCs) are a broad class of air pollutants which act as precursors to tropospheric ozone and secondary organic aerosols. Total UK emissions of anthropogenic VOCs peaked in 1990 at 2,840 kt yr -1 and then declined to approximately 810 kt yr -1 in 2017 with large reductions in road transport and fugitive fuel emissions. The atmospheric concentrations of many non-methane hydrocarbons (NMHC) in the UK have been observed to fall over this period in broadly similar proportions. The relative contribution to emissions from solvents and industrial processes is estimated to have increased from approximately 35% in 1990 to approximately 63% in 2017. In 1992, UK national monitoring quantified 19 of the 20 most abundant individual anthropogenic VOCs emitted (all were NMHCs), but by 2017 monitoring captured only 13 of the top 20 emitted VOCs. Ethanol is now estimated to be the most important VOC emitted by mass (in 2017 approx. 136 kt yr -1 and approx. 16.8% of total emissions) followed by n-butane (52.4 kt yr -1) and methanol (33.2 kt yr -1). Alcohols have grown in significance representing approximately 10% of emissions in 1990 rising to approximately 30% in 2017. The increased role of solvent emissions should now be reflected in European monitoring strategies to verify total VOC emission reduction obligations in the National Emissions Ceiling Directive. Adding ethanol, methanol, formaldehyde, acetone, 2-butanone and 2-propanol to the existing NMHC measurements would provide full coverage of the 20 most significant VOCs emitted on an annual mass basis. This article is part of a discussion meeting issue 'Air quality, past present and future'.

Original languageEnglish
Article number20190328
Number of pages20
Journal Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences
Issue number2183
Early online date28 Sep 2020
Publication statusPublished - 30 Oct 2020

Bibliographical note

© 2020 The Authors.
Funding Information:
(table 3) are based are available from the Centre for Environment Data and Analysis: Data on VOCs in Delhi are currently subject to embargo but will be available on CEDA in 2021. Authors’ contributions. A.C.L. conceived the research, performed the analysis of VOC emission trends and subsequent impacts on observations. J.R.H., J.F.H., G.S., B.S.N., J.R.H. and A.C.L. contributed the observations and data for VOCs in London, Delhi and Beijing. D.C.C. provided the analysis of atmospheric trends in VOCs from the Defra Network. J.D., T.M. and N.P. undertook the development of the underlying emissions inventory and supported observations made in the Defra Automated Hydrocarbon Network. All authors contributed to the writing of the paper. Competing interests. We declare we have no competing interests. Funding. The authors acknowledge funding from NERC (grant nos. NE/R011531/1, NE/T00197/1 and NE/P016502/10). Acknowledgements. The authors thank the members of the Defra Air Quality Expert Group (AQEG) for their contributions to the recent analysis of VOCs in the UK, work which has greatly informed the conclusions of this paper. A.C.L. and J.R.H. acknowledge funding from NERC NC LTSS and from NERC grant nos. NE/R011532/1 and NE/T001917/1. This paper draws on data from the version of the National Atmospheric Emissions Inventory programme published in 2019 (the 2017 NAEI) and prepared by the Ricardo Energy and Environment under contract to the Department for Business, Energy and Industrial Strategy. Trends in ambient non-methane hydrocarbons measured at Marylebone Road are drawn from the UK-AIR website operated by the Ricardo Energy and Environment under contract to the Department for Environment Food and Rural Affairs. The Delhi measurements were taken as part of the DELHI-FLUX project, grant no. NE/P016502/1. We acknowledge the logistic support of Ranu Gadi and Shivani (Indira Gandhi Delhi Technical University for Women), Eiko Nemitz and Neil Mulligan (Centre for Ecology and Hydrology) and Tuhin Mandal (CSIR-National Physical Laboratory).


  • air pollution
  • atmospheric emissions
  • volatile organic compounds (VOCs)

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