Microplastics are emerging threat contaminants that have been shown to provide toxic pollutants, either from the environment or from their inherent toxic monomers and additives, a pathway into the aquatic food web. In the present study, the occurrence, abundance, and composition of microplastic load in the surface water of Lake Naivasha (Kenya) was determined. The surface water physicochemical parameters were measured in situ; microplastic samples were collected using plankton net trawls and treated with H2O2 to decompose organic matter. The microplastic particles recovered were classified both by visual observation and by attenuated total reflection–Fourier transform infrared spectroscopy. The average microplastic concentration range in surface water was 0.183 ± 0.017 to 0.633 ± 0.067 particles/m2, with the mean concentration being 0.407 ± 0.135 particles/m2. Fragments, fibers, and films were identified and were mostly composed of polypropylene, polyethylene, and polyester. We also performed correlational analysis, which showed a strong positive association between microplastic quantity and turbidity, total nitrogen, and total phosphorus in the lake. The high variability in microplastic densities exhibited between the sampled locations was attributed to human activities, water and wastewater intake through rivers and tributaries, and the presence of local wind patterns responsible for the general water circulation. Our assessment adds to the growing documentation of microplastic presence in freshwater ecosystems, and provides a baseline for future monitoring and assessment in sediment and biota of Lake Naivasha and other Kenyan freshwater systems. Environ Toxicol Chem 2020;39:765–774. © 2020 SETAC

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Due to climate change and anthropogenic activities such as agriculture, mining, and urbanization, water contamination has become a very real modern problem. Modern solutions such as activated carbon, reverse osmosis, and ultrafiltration, among others, have been employed in the decontamination of water. These methods are, however, expensive to set up and maintain and therefore have proved a challenge to implement in developing countries. Zeolite materials exhibit excellent structural properties, such as high ion exchange capacity, porosity, and relative surface area, which make them attractive to water decontamination processes. However, conventional zeolites are expensive, and recent research has focused on utilizing low-cost materials such as agro-wastes and clays as raw materials for the synthesis of zeolites. This review aims to discuss the role of low-cost zeolites in their removal of heavy metals and the feasibility of agro-wastes and natural clays in the synthesis of zeolites. Recent research studies based on the synthesis of zeolites from clays and agro-wastes and their application in heavy metal removal have been reviewed and discussed. Agro-wastes such as rice husk ash and sugarcane bagasse ash and layered silicate clays such as kaolinite and smectites are particularly of interest to zeolite synthesis due to their high silica to alumina ratio. Zeolites synthesized through various methods such as hydrothermal, molten salt, and microwave irradiation synthesis have been discussed with their effect on the adsorption of various heavy metals.

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Pesticide use in Kenya plays a critical role in socio-economic development because its economy depends heavily on agriculture, which contributes to 30% of the GDP and accounts for 60% of export earnings. For agriculture and public health vector control, the country relies on pesticides, most of which (95%) are formulated products imported from China, India and Germany as the top exporters. In this chapter, we present the chemistry, manufacturing, importation and regulatory processes regarding pesticides in Kenya as well as their usage and impacts. All the various categories, organochlorine, organophosphate, carbamate, pyrethroid, neonicotinod insectides, as well as fungicides, herbicides and biopesticides, which are used in the country, are considered. A total of 1,447 and 157, which include formulations and active ingredients, respectively, for use in agriculture and public health sectors, with sufficient information on their usages and toxicities, are listed on the Pest Control Products Board (PCPB) database that is available to the public. A significant number of studies have been conducted in major agricultural regions, which have characterized pesticides, their toxicities, the types of crops and pests, the usage and human and environmental health risk indices, since the 2000, but the reports have not made any impacts on pesticide regulation, as some of the very toxic active ingredients, belonging to the WHO Class I and II, are still reported by farmers. However, a recent call from NGO’s made an impact in government and parliament, and a bill was introduced in 2020 with the aim of banning some of the toxic ones that have already been withdrawn from the EU market.