Pollution & Health

    Climate & Environmental Pollution

Post-Doctoral Fellowships

United Kingdom

Towards reducing air pollution toxicity

Air pollution from particles has been identified by the WHO as a global public health emergency. According to the organisations' latest estimates, around 7 million people die every year from exposure to fine particles in polluted air. «While it is known that airborne particulate matter causes serious health effects, the underlying reasons for its toxicity are still not clear», explains Dr. Sarah Steimer, researcher in Atmospheric Chemistry at the University of Cambridge. « To reduce the health effects of air pollution, it is essential that the most toxic particle sources are clearly identified.». In line with that reasoning, Steimer is exploring an alternative metric for measuring particle toxicity, one that is likely to be more precise and more revealing than the current method of simply measuring the particle mass per volume of air. Her ultimate objective is to allow policy makers a much more targeted and effective approach for reducing particulate toxicity in the future.
Her novel measurement approach will focus on a particular type of chemical species, called reactive oxygen species (ROS). «Present in the particles, or generated upon entry in the human lung, ROS are widely thought to be one of the main contributors to particle-related toxicity», reports Steimer. Such highly reactive species are known contributors of oxidative stress which leads to various diseases and disorders such as cardiovascular disease, cancer, ageing and neurodegenerative diseases. But proving the direct correlation between particle-bound ROS and pollution-related health effects is challenging. « Due to their high chemical reactivity, particle-bound ROS have a very short lifespan», explains Steimer. « Current methods for measuring ROS take too long. 80 to 90 % of species are lost in the process.» « The Department of Chemistry of the University of Cambridge has recently developed a unique instrument, capable of measuring ROS in the ambient atmosphere online and with a high time resolution to quantify also the short-lived ROS components»,she continues. «My project consists of taking it out and doing measurements in the field. I’m also developing a smaller, simplified, more field portable version of this instrument, which will allow deploying multiple instruments simultaneously to set up a network of ROS sensors.»


A new measurement approach to pollution toxicity

Indeed, Steimer and her team plan to use the instrument to quantify ROS concentration in atmospheric particles, and map their distribution within two cities, namely London and Dehli. Characterising ROS spatial and temporal variability in these highly polluted environments will shed light on the sources of ROS, and thus help answer crucial questions such as: « are ROS really the reason why pollution is bad for us? And if they are, where do they come from exactly? Instead of targeting all the things that generate particles, we choose to concentrate on the things that generate the ones we think are the most dangerous », Steimer summarises.« We can’t expect stake holders to ban everything that generates particles, at least not in the near future. But if we can tell them which sources are the most threatening, then they can tend to the most urgent measures. »

Despite the suspected importance of their role in pollution-related health effects, reactive oxygen species remain mysterious chemical compounds. By aiming to characterise and monitor ROS in two polluted cities, Dr. Sarah Steimer’s research holds great promise for a better understanding of the toxicity of atmospheric particles. Given than 91% of the world’s population lives in places where the air quality levels exceed WHO limits, this is an issue that concerns all of us. In developing countries in particular, Steimer insists, her findings could help prevent repeating «the profound air pollution-related mistakes of industrialisation and urbanisation in Europe and the US of the past». 



University of Cambridge


United Kingdom



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