Among the different air pollutants, PM2.5 can be easily inhaled into the lungs and might cause diverse health effects especially cardiovascular and respiratory diseases (Anderson et al. 2012). That is why it is important to understand which species contribute the most to the toxicity of these particles. One of the practical indicators recently used for the evaluation of the oxidative capacity of PM as whole is the oxidative potential (OP) (Crobeddu et al. 2017). In this study, the oxidative potential of PM2.5 was evaluated using dithiothreitol (DTT) and ascorbic acid (AA) assays on samples collected in an urban site under industrial influence in the East Mediterranean: Zouk Mikael region (ZK) in Lebanon. ZK is characterized by the biggest power plant in the country which runs on heavy fuel oil, a high density of population (4,200 inhabitants/km2) along with high road traffic and the use of diesel generators for electricity generation. The mean volume normalized OP-AA value was 0.67 ± 0.29 nmol.min¬-1.m-3. On the other hand, the mean OP-DTTv was 0.52 ± 0.32 nmol.min-1.m-3. Different approaches were used to study the relationship between the characterized species (carbonaceous matter, ions, major and trace elements, and organic compounds) or the sources contribution and OP values. Spearman correlations and hierarchical classification after principal components analysis showed that both OP-DTTv and OP-AAv at ZK were correlated with HFO combustion, diesel generators, crustal dust, road dust and vehicular emissions sources. A multiple linear regression approach was applied to the contribution of the sources obtained by PMF and the OP values at ZK site in order to estimate the contributions of PM sources to OP values. The results showed that the sources that largely contribute to the PM2.5 mass (crustal dust and ammonium sulfate sources) were not the major sources contributing to the values of OP. However, local anthropogenic sources such as biomass burning (33% of OP-AAv and 9% of OP-DTTv), vehicular emissions (20% and 23%), and heavy fuel oil combustion (31% and 46%) contribute the most to the OP-AAv and OP-DTTv, respectively. This study is a first in Lebanon and in the East Mediterranean and the Middle Eastern region presenting results of oxidative potential (OP-AA and OP-DTT), studying the correlation between the OP values and different classes of compounds (carbonaceous, ionic, elemental, and organic) and attributing OP values to the PM2.5 identified sources at the sites. The findings of this study will be of utmost importance to policymakers in order to implement policies to protect health and improve the air quality in the region.