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Assessment of Heavy Metals in Wild and Farmed Tilapia (Oreochromis Niloticus) on Lake Kariba, Zambia: Implications for Human and Fish Health
(Taylor & Francis, 2022) Simukoko, Chalumba K.; Mwakalapa, Eliezer B.; Bwalya, Patricia; Muzandu, Kaampwe; Berg, Vidar; Mutoloki, Stephen; Polder, Anuschka; Lyche, Jan, L.
The aim of this study was to assess the levels of heavy metals in both wild and farmed tilapia on
Lake Kariba in Zambia and to evaluate the impact of intensive fish farming on wild tilapia. Three
sites for wild fish (2 distant and 1 proximal to fish farms) and two fish farms were selected. One
hundred fish (52 from distant sites; 20 near fish farms; 28 farmed fish) were sampled and muscle
tissues excised for analysis of heavy metals (Mg, Fe, Zn, Al, Cu, Se, Co, Mo, As, Cr, V, Ni, Hg, Pb, Li, Cd,
and Ag) by acid (HNO3) digestion and ICP-MS. All metals were found to be below the maximum
limits (MLs) set by WHO/EU. Essential metals were higher in farmed tilapia, whereas non-essential
metals were higher in wild tilapia. Significantly higher levels of essential metals were found in wild
fish near the fish farms than those distant from the farms. Estimated weekly intake (EWI) for all
metals were less than the provisional tolerable weekly intakes (PTWI). Target hazard quotients
(THQ) and Hazard Indices (HI) were <1, indicating no health risks from a lifetime of fish consump-
tion. Selenium Health Benefit Value (HBVSe) was positive for all locations, indicating protective
effects of selenium against mercury in fish. Total cancer risk (CR) due to As, Cr, Cd, Ni and Pb was less
than 1 × 10−4, indicating less than 1 in 10,000 carcinogenic risk from a lifetime consumption of
tilapia from Lake Kariba. Hg levels (0.021 mg/kg) in wild tilapia at site 1 were higher than the
Environmental quality standard (EQS = 0.020 mg/kg) set by EU, indicating possible risk of adverse
effects to fish. Except for Hg, levels of metals in fish were safe for human consumption and had no
adverse effects on fish.
Histological Identification of Germline Stem Cells’ Recipients for Conservation of Balkan Trout Fish Species by Transplantation Technology
(MUST Journal of Research and Development, 2024) Shimo, Seleman S; Nicholaus, Regan; Horváth, Ákos; Marinović, Zoran
Combining cryopreservation of germline stem cells (GSCs) with their subsequent transplantation into recipient fish is a powerful technique for long-term conservation of the genetic resources of threatened fish species. However, transplantation of GSCs has been limited by a failure to identify an appropriate recipient for surrogate production of donor-derived gametes. In the worst-case scenario, recipients may completely reject the transplanted GSCs due to an immunological reaction. This limitation can be overcome by specifying the gonadal status of both GSC donor and recipient species. This study used histological methods to identify possible GSC recipients for rescuing endangered trout fish species on the Balkan Peninsula. The study specified the gonadal status of brown trout, triploid rainbow trout, and tiger trout. The findings revealed that both triploid rainbow trout and tiger trout are sterile. The fish's testes contained only early-stage germ cells and did not develop past type-B spermatogonia, whereas the ovaries contained only oogonia. Both spermatogenesis and oogenesis were incomplete in these fish, and the gametes, i.e., functional spermatozoa and eggs, could not be formed. As a result, these fish make excellent recipients for GSC transplantation. Because most Balkan trout belong to the genus Salmo and closely related species, tiger trout would be a more feasible recipient of GSCs due to the small phylogenetic distance, as it is a hybrid of brown trout female and brook trout male.
Accumulation and Distribution of Mercury in Agricultural Soils, Food Crops and Associated Health Risks: A Case Study of Shenda Gold Mine-Geita Tanzania
(ELSEVIER, 2023) Sanga, Tumikia R.; Maseka, Kenneth K.; Ponraj, Mohanadoss; Tungaraza, Clavery; Mng’ong’o, Marco E.; Mwakalapa, Eliezer B.
Contamination of the environment and foodstuffby potentially harmful elements (PHEs) has become a serious concern due to the associated health risks to the population. In the present study total mercury (Hg) levels in soil and food crops from farms around Shenda gold mine in Geita Tanzania was determined by Cold Vapor Atomic Fluorescence Spectrometry (CVAFS). Generally, it was found that there was significant different of Hg content in soil and food crops ( P < 0.05) among studied sites. The total Hg concentrations determined were in the ranges of; soils (0.003-0.1220 mg/kg), rice (0.0752-0.1587 mg/kg) and vegetables (0.0556-0.3439 mg/kg) all measurement were based on dry weight basis (dw). Total Hg levels in soil were compared with the maximum allowable concentration (MAC) set by Tanzania Bureau of Standards (TBS) and United Kingdom (UK). All studied soil samples were within acceptable range (2 mg/kg) set by TBS and UK (1 mg/kg). Total Hg contents in food crop samples were compared with Chinese MAC of Hg (0. 01 and 0.02 mg/kg for leafy vegetables and grains respectively in a fresh weight basis). It was observed that Hg contents in potato leaves, pumpkin leaves and Chinese cabbage were within the MAC while Hg levels in cassava leaves and rice grains exceeded the MAC. In addition, Hg associated health risks to consumers of contaminated foods for residents around Shenda gold mine were estimated. The estimated weekly intake (EWI) of Hg due to consumption of rice grain was above the provisional tolerable weekly intake (PTWI) set by FAO/WHO (1.6 mg/kg bw/week) while the EWI due to consumption of leafy vegetables were below the PTWI. Target hazard quotient (THQ) was < 1 due to consumption of vegetables while THQ value for rice was > 1, indicating a potential non-carcinogenic risk to adult population from the consumption of rice grain from the study area. Therefore, people living near Shenda goldmine might be potential victim of Hg accumulation in soil and food crops, thus necessary management options have to be in place
Concerning the status of mathematics and physics for secondary school science students’ sustainability in the 21st century STEM disciplines
(ORIGINAL RESEARCH ARTICLE, 2026-01-08) Kibona ,Isack E
The National Examination Council of Tanzania plays a significant role in shaping secondary school graduates’ career pathways through the Certificate of Secondary School Education (CSEE). This study examined future implications and strategies for improving graduates’ prospects in Science, Technology, Engineering, and Mathematics (STEM) fields, using the 2022 CSEE results from secondary schools in Mbeya City.
OPTIMIZING THE EFFICIENCY OF SUBSIDY FERTILIZER DISTRIBUTION SYSTEM; A CASE STUDY OF MBEYA, TANZANIA
(MBITA, OSCAR DAVID, 2025-06-30) MBITA OSCAR DAVID
Agriculture remains the backbone of Tanzania’s economy, employing over 65% of the
population and playing a vital role in food security and rural development. To enhance
agricultural productivity and ensure affordable access to essential inputs, the
Tanzanian government implemented a fertilizer subsidy program targeting
smallholder farmers. Despite its intentions, the current distribution system faces
critical challenges, including inefficiencies, fraud, delayed deliveries, and low user
satisfaction. The primary objective of this study was to optimize the efficiency of the
subsidy fertilizer distribution system. The study examines how blockchain technology
can address existing challenges by providing transparency, traceability, and enhanced
accountability. A mixed-methods approach involving stakeholder interviews and
structured questionnaires revealed weaknesses in the current system, underscoring the
need for innovation. In response, a blockchain-enabled framework was developed,
incorporating a layered e-voucher system built on a hybrid N-tier and microservices
architecture. The framework includes Key features such as smart contracts for
automated eligibility verification and a permissioned ledger to ensure tamper-proof
data integrity. Functional and heuristic testing confirmed the system’s usability,
scalability, and reliability. The proposed solution offers a robust and scalable model
for policymakers and practitioners to modernize fertilizer subsidy programs in
Tanzania, utilizing decentralized technologies.