Hassan Aftab Sheikh

Islamic Republic of Pakistan

University of Cambridge



We are exposed to harmful particulates in the air everyday—knowingly and unknowingly. Air pollution consists of various compounds, aerosols, and particulate matter (PM) where some of these are more toxic than others. My research focuses on characterising iron-bearing ultrafine PM (< 100 𝑛𝑚 in aerodynamic diameter) for their potentially serious health implications. These particulates are invisible, therefore, there is a need to detect them and quantify their amount in ambient air. It is important that we identify these particles because in traditional monitoring systems usually underestimate the number of ultrafine particles skew the particle size distribution to large particles (as particles are aggregated).

Magnetic techniques are useful when it comes to identifying and focusing on health-relevant particles. The project involved multiple sampling campaigns in different micro-environments—Lahore, Pakistan, London Underground, and Manchester. We have used both passive monitoring (leaves) and active monitoring in indoor and outdoor environments. The primary objective of the project is to use magnetic methods for the detection and characterisation of variations in iron oxide nanoparticles in tree leaves, complement it with chemical and microscopy techniques to add value to the existing air pollution monitoring methods. This will be an important contribution to unravelling different sources of particulates for specific microenvironments and could have wide-reaching implications.

One question we are trying to answer is to understand why people in certain areas are more at risk to certain diseases despite lower PM concentrations. Our hypothesis is that it is likely to be because of the dominance of ultrafine sizefraction (ultrafine particles are lower in mass and higher in number concentration). Ideally, we would perform studies to see whether green infrastructure (trees, shrubs, hedges etc.) are effective in PM removal through deposition or
dispersal processes.