Demonstrating PM2.5 and road-side dust pollution by heavy metals along Thika superhighway in Kenya, sub-Saharan Africa

Abstract

This study assessed the level of heavy metal in roadside dust and PM mass concentrations along Thika superhighway in Kenya. Thika superhighway is one of the busiest roads in Kenya, linking Thika town with Nairobi. Triplicate road dust samples collected from 12 locations were analysed for lead (Pb), chromium (Cr), cadmium (Cd), nickel (Ni), zinc (Zn), and copper (Cu) using atomic absorption spectrophotometry (AAS). PM samples were collected on pre-weighed Teflon filters using a BGI personal sampler and the filters were then reweighed. The ranges of metal concentrations were 39-101 μg/g for Cu, 95-262 μg/g for Zn, 9-28 μg/g for Cd, 14-24 μg/g for Ni, 13-30 μg/g for Cr, and 20-80 μg/g for Pb. The concentrations of heavy metals were generally highly correlated, indicating a common anthropogenic source of the pollutants. The results showed that the majority of the measured heavy metals were above the background concentration, and in particular, Cd, Pb, and Zn levels indicated moderate to high contamination. Though not directly comparable due to different sampling timeframes (8 h in this study and 24 h for guideline values), PM for all sites exceeds the daily WHO PM guidelines of 25 μg/m. This poses a health risk to people using and working close to Thika superhighway, for example, local residents, traffic police, street vendors, and people operating small businesses. PM levels were higher for sites closer to Nairobi which could be attributed to increased vehicular traffic towards Nairobi from Thika. This study provides some evidence of the air pollution problem arising from vehicular traffic in developing parts of the world and gives an indication of the potential health impacts. It also highlights the need for source apportionment studies to determine contributions of anthropogenic emissions to air pollution, as well as long-term sampling studies that can be used to fully understand spatiotemporal patterns in air pollution within developing regions.

The toxicity of ambient fine particulate matter (PM2.5) to vascular endothelial cells

“…Metal components of PM2.5 might be crucial factors that affect cellular toxicity (Wang et al, 2016). Nickel (Ni) is a transitional metal identified in PM2.5 from different sources (Bačeva, Stafilov, Sajn, & Tănăselia, 2012; Barandovski et al, 2012; Lu et al, 2015; Maina, Gachanja, Gatari, & Price, 2018; Slezakova, Alvim‐Ferraz Mda, & Pereira Mdo, 2012), but it is mainly produced by burning fossil fuels (Bencko, 1983). Ying et al explored whether Ni induced endothelial dysfunction through oxidative stress‐dependent inhibition of endothelial nitric oxide synthase (eNOS) dimerization in VECs (Ying et al, 2013).…”

Functional, Structural and Non-Structural Preparedness of Ahvaz Health Centers Against Disasters in 2014 – 2015

“…Suspended particles are dangerous for human health at high concentrations, for example, they cause different diseases such as upper respiratory tract infection, pulmonary inflammation, and bronchitis (6,7). Heavy metals are one group of compounds present in the air with a high risk for human health (8,9). The presence of heavy metals in greater concentration than the standard levels causes environmental problems and damages the inhabitant's health of that site and the ecosystem (10,11).…”

Air pollution in Kenya: a review

“…Twenty studies report PM 1 , PM 2.5 or TSP concentrations (Ngang'a and Ngugi 1986; Karue et al 1992;Gatebe et al 2005;Vliet and Kinney 2007;Gatari et al 2009aGatari et al , b, 2019Odhiambo et al 2010;Kinney et al 2011;Gaita et al 2014Gaita et al , 2016Ngo et al 2015;Shilenje et al 2015Shilenje et al , 2016deSouza et al 2017;Mukaria et al 2017;Maina et al 2018;Pope et al 2018;Egondi et al 2018;West et al 2020). One study included in this review also reports the number and kind of bacteria in aerosol samples in Nairobi (Yin et al 2018).…”