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Following research undertaken at Diamond, particulate emissions from cooking have been discovered to stay in the atmosphere for longer than initially thought, causing a prolonged contribution to poor air quality and human health.
A new study, led by researchers at the University of Birmingham, demonstrated how cooking emissions can survive in the atmosphere over several days, rather than being broken up and dispersed.
The team collaborated with Diamond, the University of Bath and the Central Laser Facility to show how these fatty acid molecules react with molecules found naturally in the earth's atmosphere. During the reaction process, a coating is formed around the outside of the particle that protects the fatty acid inside from gases such as ozone which would otherwise break up the particles.
This research was made possible by using Diamond's powerful X-ray beamline (I22). For the first time researchers we able to recreate the reaction process in a way that enables it to be studied in laboratory conditions.
Nick Terrill, Principal Beamline Scientist on I22, said:
The well collimated, very intense X-ray beam on I22 made it possible to explore the film reactivity in these cooking emission proxies under realistic conditions. It also gave us the opportunity to explore a diverse range of cooking emission lifetimes. The versatile nature of the I22 Sample Environment space and close collaboration with the Central Laser Facility made the laser setup, used in this study, possible.
The study, published in Royal Society of Chemistry’s Faraday Discussions, shows that the ability of these particles to remain in the atmosphere for longer may have a number of implications on climate change and human health. The molecules are interacting so closely with water, this affects the ability of water droplets to form clouds. In turn this may alter the amount of rainfall, and also the amount of sunlight that is either reflected by cloud cover or absorbed by the earth – all of which could contribute to temperature changes.
Cooking emissions currently account for up to 10 per cent of particulate pollution in the UK. However, this research has discovered that when the cooking emission particles form their protective layer they can also incorporate other pollutant particles, including those known to be harmful to health such as carcinogens from diesel engine emissions. These particles can then be transported over much wider areas.
Lead author, Dr Christian Pfrang, of the University of Birmingham’s School of Geography, Earth and Environmental Sciences, said:
These emissions, which come particularly from cooking processes such as deep fat frying, make up a significant proportion of air pollution in cities, in particular of small particles that can be inhaled known as PM2.5 particles. In London it accounts for around 10 per cent of those particles, but in some of the world’s megacities for example in China it can be as much as 22 per cent with recent measurements in Hong Kong indicating a proportion of up to 39 per cent.
The implications of this should be taken into account in city planning, but we should also look at ways we can better regulate the ways air is filtered – particularly in fast food industries where regulations do not currently cover air quality impacts from cooking extractor emissions for example.
The research was supported by the Science and Technology Facilities Council (STFC) and the Natural Environment Research Council (NERC).
For more information about Diamond's I22 beamline, please visit the website.
Milsom, A. et al. The persistence of a proxy for cooking emissions in megacities: a kinetic study of the ozonolysis of self-assembled films by simultaneous small and wide angle X-ray scattering (SAXS/WAXS) and Raman microscopy. Faraday Discussions (2020) DOI:10.1039/d0fd00088d
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