Use of pesticides and risk perception of environmental contamination by farmers surrounding the Menoua River (West Cameroon).

Cameroonian farmers regularly use pesticides in farming to control pests, particularly along the riverbank of the Santchou agricultural area. The aim of this study was to assess the perception of farmers in West Cameroon (Santchou area) regarding the contamination risk in aquatic environments from the use of pesticides. A cross-sectional study via questionnaires was conducted among 150 selected farmers who cultivated fields along the banks of the Menoua River. Almost all the farmers (90%) used pesticides regularly, particularly herbicides, insecticides, and fungicides to combat pests. The main pesticides used were glyphosate, paraquat, dieldrin, chlorpyrifos-ethyl, copper oxide, and mancozeb. Farmers who cultivated larger areas of land or who had mixed culture crops tended to use pesticides more often (p < 0.001). The use of river water by farmers was correlated with pesticide use (p = 0.010). Most of the pesticide users (90%) did not use protective equipment when spraying the crops. The farmers' perceptions of the risk of pesticide contamination of the river water (p = 0.002) or fish (p = 0.008) did not influence their actions. A correlation was found among pesticide users who believed that there was a risk of river contamination (45%) or fish contamination (42%) and intensive pesticide application during the rainy season (61%) or non-respect of the prescribed pesticide application doses (51%; p = 0.002). Farmers who regularly or occasionally consumed fish used pesticides more often than those who did not consume fish from the river. The findings of this study emphasize the need for education of farmers in Santchou to prevent the risk of environmental contamination and health hazards from increased dietary and/or dermal pesticide exposure. Integr Environ Assess Manag 2023;19:1600-1608. © 2023 SETAC.

Concentrations of pesticide residues in fish tissue are below detectability in the Menoua River (West Cameroon).

Fresh water fish are an important source of animal protein in the diet of Africans, but despite their exposure to pollutants, particularly pesticides, in rivers and streams, there is scarcity of data on fish accumulation levels of these pollutants. The concentrations of 259 pesticide residues were measured in two highly consumed fish species (Clarias gariepinus and Oreochromis niloticus) sampled from the Menoua River, in the West Region of Cameroon. The pesticide residues were determined using QuEChERS (Quick Easy Cheap Effective Rugged and Safe) followed by gas chromatography-mass spectrometry. The results obtained show that concentrations of all pesticide residues in the samples were lower than 0.01 mg/kg and therefore below the WHO maximum residue limit for the evaluated pesticides. However, the non-detection of pesticides in the studied fish does not call for complacency as this does not imply a complete absence of pesticides. Low levels of pesticide mixtures have been shown to result in combined effects that are synergistic. There is therefore a need for further research on the possible biological effects, including endocrine disruption, growth and reproduction inhibition on the fish populations as well as dietary risk assessment on the local population. The contamination of water, sediment and other aquatic resources also remains a question for future research.

Soil Contamination and Bioaccumulation of Heavy Metals by a Tropical Earthworm Species (Alma nilotica) at Informal E-Waste Recycling Sites in Douala, Cameroon.

Soil contamination at electronic waste (e-waste) recycling sites is pervasive, though many locations have yet to be studied. While such contamination can present risks to soil organisms, little is known on the risks to native species. The objective of the present study was to assess soil contamination by heavy metals at e-waste recycling sites, and the potential of Alma nilotica, a native earthworm species, to bioaccumulate these metals. Soil samples collected from eight informal e-waste recycling sites and two non-e-waste sites in Douala, Cameroon, were analyzed for metal content. Metal concentrations in earthworm juveniles exposed to the soils for 21 days followed by a 14-day post-exposure period were measured weekly. Mean soil metal concentrations at e-waste sites ranked as Cu > Pb > Zn > Hg > Ni > As > Cd > Co > Cr. Based on contamination factors, soil contamination ranged from "moderate" (Cr), through "considerable" (Co and Cd), to "very high" for the rest of the metals. Based on the modified degree of contamination and risk index, all e-waste sites had "ultra-high" contamination with Ni, Pb, and Zn posing very high ecological risks and Bonaberi being the most contaminated site. There was a positive correlation between soil metal concentrations and metal accumulation (retention) by eathworms, but Hg and Co had the highest bioaccumulation factors (BAFs) despite having low soil concentrations. These results document that e-waste sites in Douala are contaminated with metals and that native earthworm species can bioaccumulate the studied metals at levels that could account for the toxic effects earlier recorded. With e-waste recycling growing worldwide, there is a need for more data, especially from understudied locations. Environ Toxicol Chem 2022;41:356-368. © 2021 SETAC.