In the city of Moanda, where one of the world’s largest manganese (Mn) deposits is located, the soils are very rich in manganese, which promotes the transfer of Mn from the soil to the various organs of fruits and vegetables that are grown near the manganese plateaus. Cassava is widely cultivated and consumed daily by the population of this region of Gabon. These cassava leaves pose a moderate but not negligible risk to the people who consume them daily. This study was conducted to assess the health risks to the population of this region who regularly consume cassava leaves. Manganese (Mn) concentrations in cassava leaves were measured at four sites in Moanda (La Gare, Leyima, L’Alliance, and L’Oasis), which have relatively high levels in the soil. The results show high concentrations of manganese in cassava leaves, concentrations above regulatory limits with a maximum of 48200 µg.kg-1. The risk factor calculation indicates that these concentrations represent a moderate but not negligible risk factor for the health of the inhabitants of Moanda who regularly consume cassava leaves.

C4 plants are plants with modified photosynthetic metabolism, allowing overproduction of organic matter, compared to other so-called C3 plants. It is for this reason that C4 plants are used primarily in the nutritional and nutritional formulations of infants. Current data on these plants are only limited to Western work done on a limited sample. This work has been done to identify the C4 food plants found on the Gabonese market. A collection of food plants was thus carried out on the central market of Franceville, and the samples studied in the laboratory. The determination technique was based on anatomical identification of perivascular sheaths at the level of cellular cross sections. The results obtained showed that out of 32 species analyzed, only 5 plants belonging to 2 families were of C4 typology. These are local lemongrass (Cymbopogon cytratus, Poaceae), maize (Zea mays, Poaceae), sugar cane (Saccharum officinarum, Poaceae), Chinese lemongrass (Cymbopogon sp., Poaceae) and folon / amaranth (Amaranthus sp. Amaranthaceae). The presence of C4 plants on the Gabonese market seems relatively weak.