Multi-Risk Assessment Based on PM2.5 Elemental Composition: A Case Study from an Open-Air Place in Yaoundé, Cameroon

This investigation provides a qualitative and quantitative characterisation of the toxic trace elements contained in fine airborne particles (PM _2.5 ) collected in an urban site of Yaoundé. The aim is to determine the contribution of natural and anthropogenic sources, as well as to assess exposure, ecological and health risks. X-ray fluorescence spectrometry identified 17 toxic trace elements, including nine heavy metals (Fe, Zn, Cu, V, Co, Mn, Ni, Cr and Pb). Fe was the most abundant element, with a concentration of 1.56E-1 µg/m ³ , while V was the least abundant, with a concentration of 9.00E-5 µg/m ³ . Cross-analysis of the enrichment factor, contamination factor and geo-accumulation index as well as the K/Fe and V/Ni ratios, revealed a mixed (crustal and anthropogenic) origin for PM _2.5 , with a particularly high contribution from metal sources. These results highlight the multiplicity of sources, marked temporal variability and irregular emission frequency. The exposure risk assessment, based on measured concentrations and international guideline values, indicates a low-to-moderate risk for heavy metals and a high risk for PM _2.5 . The ecological risk index calculated for PM _2.5 was 282.39, reflecting a potentially moderate impact on ecosystems. Of the analysed heavy metals, only Ni, Mn and Co exhibited high hazard indices, indicating a significant probability of non-carcinogenic health effects. Furthermore, Ni and Co exhibit values that are significantly indicative of high carcinogenic risk. These findings emphasise the urgent need to implement strategies to reduce fine particle emissions and target metal sources in this urban environment.