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expert reaction to study looking at the health impact and abatement costs of global nitrogen emissions

A study published in Science looks at the health impact and abatement costs of global nitrogen emissions.

This Roundup accompanied an SMC Briefing.


Prof Roy Harrison FRS, Professor of Environmental Health at the University of Birmingham, said:

“This is research of high quality which combines the modelling of atmospheric composition with economic analysis of abatement scenarios.  The report is of particular importance for the United Kingdom as it demonstrates how to achieve cost-effective control of airborne ammonium nitrate, which is the largest single contributor to PM2.5 particle concentrations in our atmosphere, responsible for many thousands of premature deaths and hospital admissions annually.  Ammonium nitrate is not emitted, but is formed in the air from chemical reactions of two ingredients, nitrogen oxides and ammonia.  We can expect to see major reductions in nitrogen oxides as road traffic becomes battery-electric, and more electricity is generated from renewables.  However, the main source of ammonia is from agriculture, and unlikely to change without more efficient use of fertilisers and better ways of disposing of animal waste.  These can be achieved by more closely matching fertiliser application to the needs of the crop, adoption of enhanced-efficiency fertilisers and application machinery, and sub-surface injection of slurry and other animal wastes.  Meeting the latest air quality guidelines recommended by WHO will be extremely challenging for the UK, and this paper demonstrates clearly the benefits which would accrue worldwide from reductions in ammonia emissions.”


Prof Bill Collins, Professor of Climate Processes, University of Reading, said:

“Ammonia is one of the pollutants that is least regulated. Since it comes mainly from agricultural practices, unlike other pollutants it won’t be reduced by the phasing-out of fossil fuel use and so is expected to continue to rise over the rest of the century. This study shows how significant the benefits of controlling ammonia emissions could be across the world in terms of reducing premature death, and that this could be done cheaply. This study uses global-scale modelling which will overestimate the contribution of ammonia compared to very localised sources of pollution (e.g. road dust, tyre wear, brake dust) experienced by people in city streets, but still makes a very valid point about the importance of ammonia. Controversially the study also finds that reducing emissions of nitric oxide “NOx” (which is primarily from fossil fuel burning) would cost more to reduce than would be gained from the reduction in mortality. This did not account for the direct health impacts of NO2 (acknowledged by the authors) which is a significant pollutant in cities, and did not account for the impact of ozone on reduction in crop and forestry yields. Hence this study should not be taken as a recommendation to relax NOx emission control measures.”



‘Abating ammonia is more cost-effective than nitrogen oxides for mitigating PM2.5 air pollution’ by Baojing Gu et al was published at 18:00 UK time on Thursday 4th November.

DOI: 10.1126/science.abf8623



All our previous output on this subject can be seen at this weblink:



Declared interests

Prof Roy Harrison: “Member of the Defra Air Quality Expert Group and the DHSC Committee on the Medical Effect of Air Pollutants.”

Prof Bill Collins: “None.”

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