3D imaging of London roadside particulate matter

Abstract

Air pollution kills up to eight million people annually and is a recognised risk factor for respiratory disease [1]. Effects are not restricted to the lungs with reports of combustion derived inhalable PM identified in brain and heart tissue [2]. The mechanism of action by which PM adversely affects health is poorly understood. It has been suggested that, in addition to size, PM morphology may be an important property [3]. The aim of this study was to examine roadside PM in 3D using confocal microscopy.

Samples of air pollution derived ≤PM10 were collected as dry respirable particles on a major London road (Marylebone Road) using a high-volume cyclone [4]. Aggregated particles were separated and deposited onto a glass slide before imaging (Olympus LEXT OLS4100 confocal microscope x100 objective lens). Particles were assessed for 3D shape, size and colour using Olympus microscope software.

3D visualisation showed that particles often had jagged, sharp edges which may not be evident from 2D images alone. From 10 particles, the median (range) longest length was 4.0 (1.3 to 6.6)µm, perpendicular length 2.1(1.2 to 5.6)µm and height 1.2 (0.3 to 2.2)µm (example shown in figure 1).

These results suggest that some roadside PM particles have a sharp or jagged appearance which may help explain their ability to tightly adhere to and infiltrate the respiratory system.

^1.WHO ed 2016; ^2.J Med Tox.2012;8(2):166. Langmuir, 2006.22(12); ^4.J Env Monit, 2010. 12(10)