Abstract Radiocarbon content in biogenic samples is widely used to study the variation of atmospheric CO2 due to anthropogenic activities. A total of 20 samples of several types of tree leaves, were analyzed for this study. Sampling was carried out at the end of the rainy season in 2017 from the surrounding of the SOCOCIM cement factory in Rufisque town. Rufisque is located on the peninsula of Cape Verde, 25 km east of Dakar, where it is the «south gate» of the agglomeration. Reference samples of five different species were collected during the same period (2017) from a clean zone. The 14C method was used for the determination of Δ14C values. The data show that the 14C concentration in the studied sites was significantly lower than the clean area, due to the release of anthropogenic CO2. To estimate the Suess effect, the fossil fuel fraction was determined based on equations of mass balance for CO2 concentration, stable isotopic composition of carbon, and 14C concentration. The results show that selected locations are affected differently according to their distance from the factory and the wind direction.