A new study reveals that particulate emissions from cooking tend to remain in the air for a longer time compared to what was thought earlier, thus contributing more to poor air quality and human health.
At the University of Birmingham, scientists were successful in illustrating how cooking emissions—constituting up to 10% of particulate pollution in the United Kingdom—can stay in the air over several days, instead of being disintegrated and dispersed.
The researchers collaborated with experts at the University of Bath, the Central Laser Facility and Diamond Light Source to illustrate how these fatty acid molecules react with molecules that occur naturally in the Earth’s atmosphere.
At the time of the reaction, a coating, or crust, develops around the particle’s outer part and safeguards the fatty acid inside from gases like ozone, which would otherwise disintegrate the particles.
For the first time, researchers have been able to simulate the process such that it can be studied under lab conditions using the strong X-ray beam at Diamond Light Source to track the degradation of thin layers of molecules representative of such cooking emissions in minute detail. The findings of the study were published in the Royal Society of Chemistry’s journal Faraday Discussions.
The potential of these particles to stay in the air has several impacts on climate change and human health. Since the interaction of the molecules with water is so close, this influences the capability of water droplets to develop into clouds.
At the same time, this might change the amount of rainfall, plus the amount of sunlight that is either reflected by cloud cover or absorbed by the Earth—all of which could lead to temperature changes.
Moreover, when the cooking emission particles form their protective layer, they can also add other pollutant particles, such as those that are known to be detrimental to health, like carcinogens from diesel engine emissions. Then, these particles can be transported over much broader regions.
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%.
Dr Christian Pfrang, Study Lead Author, School of Geography, Earth and Environmental Sciences, University of Birmingham
“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,” added Pfrang.
The study was financially supported by the Science and Technology Facilities Council (STFC) and the Natural Environment Research Council (NERC).
Milsom, A., et al. (2020) 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. doi.org/10.1039/d0fd00088d.