Assessing levels of cytotoxicity in A549 epithelial lung cells under various exposure to African dust particles
A dust storm is a common source of atmospheric particulate matter (PM) that can define air quality levels in arid and semi-arid regions. Dust particles vary in size and can travel long distances from their source. Coarse dust particles with aerodynamic diameter less than 10 m (PM10) can enter the mouth and nose and stay in the upper respiratory tract, while fine dust particles with aerodynamic diameter less than 2.5 m (PM2.5) can get deep into the lower respiratory tract causing damage to the lungs or exacerbate symptoms in those with pre-existing respiratory conditions like chronic obstructive pulmonary disease (COPD), rhinitis and asthma. The Sahara-Sahel region and the Southern Africa region in Africa account for more than half of the total global dust emission, yet there are very limited data on these particles cytotoxic effect. There are various assessments on epidemiological studies involving African dust particles that reach European, Asian and Caribbean countries, yet the exact cytotoxic effects of the dust source origin remain unclear. This project investigated the impact of twelve soil samples from the Sahara-Sahel region and two soil samples from the Southern Africa region to understand the (1) dose dependent effect of samples at concentrations 0, 25, 50, 100, 250, and 500 µg ml-1 (2) impact of particle sizes (3) effects on A549 cells after 24 and 48 hours exposure (4) association between samples collected from the same countries. Exposure assessments were carried out using Trypan Blue dye exclusion for all soil samples. Generally, results showed significant difference (P0.001) in dosage dependent cytotoxicity in higher concentrations. Higher percentage of cell death was mostly in cells exposed to ground samples (samples with higher concentrations of smaller particles), however some unground samples had higher cell death than the ground samples in high concentrations. Fungi growth in the unground samples collected from parts of Ethiopia and Senegal indicated presence of biological materials that were not broken down in the dust grinding process. Time effect analysis showed that generally, cytotoxicity was more present in cells exposed to particles for 24 hours than those exposed for 48 hours. Comparing all ground samples for 24 hours revealed that one of the samples collected from Algeria was the least toxic of all samples, and the sample collected from South Africa was the most toxic which indicates that cytotoxicity of particles varies on location. LDH assay revealed non-monotonic relationship in two toxic samples suggesting similarity in the mechanism effect of toxic samples while a clonogenic assay revealed that the least toxic sample formed more smaller colonies while the most toxic sample formed less bigger colonies indicating that toxic dust inhibits cell proliferation.Embargo status: Restricted until September 2023. To request an access exception, click on the PDF link to the left.