Heavy metal levels and human health risk implications associated with fish consumption from the lower Omo river (Lotic) and Omo delta lake (Lentic), Ethiopia.

This study is the first to determine the levels of heavy metals in commercially important fish species, namely Lates niloticus and Oreochromis niloticus and the potential human health risks associated with their consumption. A total of 120 fish samples were collected from the lower Omo river and Omo delta, with 60 samples from each water source. The fish tissue samples (liver and muscle) were analyzed using a flame atomic absorption spectrometer for nine heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn). The human health risk assessment tools used were the target hazard quotient (THQ), the hazard index (HI), and the target cancer risk (TCR). The mean levels of heavy metals detected in the liver and muscle of L. niloticus from the lower Omo river generally occurred in the order Fe > Zn > Pb> Cu > Mn> Cr > Co > Ni and Pb > Cu > Mn > Co > Ni, respectively. The mean levels of metals in the muscle and liver tissues of O. niloticus were in the order Fe > Pb > Zn > Mn > Cu > Cr > Co > Ni and Pb > Zn > Mn > Fe > Cu > Co > Ni, respectively. Similarly, the mean levels of heavy metals detected in the liver and muscle of L. niloticus from Omo delta occurred in the order Fe > Zn > Pb > Cu > Mn > Cr > Co > Ni and Fe > Pb > Zn > Mn > Cu > Co > Cr > Ni, respectively. The mean levels in the muscle and liver tissues of O. niloticus from the Omo delta were in the order Fe > Pb > Zn > Mn > Cu > Cr > Co > Ni and Pb > Fe > Zn > Mn > Co > Cu > Ni, respectively. The study revealed that the THQ values were below 1, indicating that consumption of L. niloticus and O. niloticus from the studied sites does not pose a potential non-carcinogenic health risk. Although the TCR values for Pb in this study were within the tolerable range, it's mean concentration in the muscle and liver tissues of both fish species from the two water bodies exceeded the permissible limit established by FAO/WHO. This is a warning sign for early intervention, and it emphasizes the need for regular monitoring of freshwater fish. Therefore, it is imperative to investigate the pollution levels and human health risks of heavy metals in fish tissues from lower Omo river and Omo delta for environmental and public health concerns.

Level of Heavy Metals in Fish and Associated Human Health Risk From the Omo Delta in Southern Ethiopia: A First-Hand Report.

This study was the first to investigate the levels of heavy metals in commercially important fish species (Lates niloticus and Oreochromis niloticus) and the human health risk in Southern Ethiopia. Sixty fish samples were collected from the Omo delta. The target hazard quotient (THQ), hazard index (HI), and target cancer risk (TCR) were used to estimate the human health risks. The mean levels of heavy metals detected in the liver and muscle of Lates niloticus generally occurred in the order of Fe> Zn > Pb > Cu >Mn> Cr > Co > Ni and Fe > Pb > Zn >Mn > Cu > Co > Cr >Ni, respectively. Similarly, the mean levels of iron in the muscle and liver tissues of Oreochromis niloticus were in the order of Fe > Pb > Zn >Mn> Cu > Cr > Co > Ni and Pb > Fe > Zn >Mn> Co > Cu > Ni, respectively. The THQs in the muscle of L. niloticus and O. niloticus decreased in the order Pb > Cr > Cu >Mn> Co > Zn > Fe> Ni and Pb >Mn> Co > Cu > Zn > Ni> Fe respectively. Pb had the highest THQ value in L. niloticus and O. niloticus, which were 0.61 and 0.409, respectively in adult. Similarly, Pb had noted that, L. niloticus and O. niloticus had the highest THQ values, at 0.87 and 0.58, respectively in children. The HI values due to consumption of L. niloticus muscle were 0.668 for adults and 0.942 for children. The mean concentrations of Pb and Cr in the tissues of L. niloticus and O. niloticus were above the FAO/WHO permissible limits. Consequently, investigating heavy metal pollution levels in fish and human health risks from the Omo delta is imperative for addressing environmental and public health concerns.

Levels and Trophic Transfer of Selected Pesticides in the Lake Ziway Ecosystem.

The levels of 30 selected pesticides and trophic biomagnification of DDT were investigated in biota samples of the Lake Ziway in the Rift valley region, Ethiopia. Carbon source and trophic position were calculated by using 13C and 15N stable isotopes, individually, and trophic magnification factors (TMFs) were inferred. Only DDT and its metabolites were quantified in all samples analyzed. The most prominent metabolite was p,p'-DDE with mean concentration ranging from the 0.82-33.69 ng g-1 lipid weight. Moreover, the ratio of DDT/DDD + DDE in all the biota samples was less than 1 signifying historical DDT application. Regression of log [ΣDDT] vs TL (trophic level) among all biota species showed a significant correlation, indicating that DDTs are biomagnifying along with the food web of Lake Ziway with an estimated TMF of 2.75. The concentrations of DDTs and other organochlorine pesticides found in biota from Lake Ziway were, in general, lower than studies found in previous studies carried out in the same lake.

Small-scale Farmer Pesticide Knowledge and Practice and Impacts on the Environment and Human Health in Ethiopia.

BACKGROUND: Inappropriate use and application of pesticides in Ethiopia pose a major threat to the health of farmers and the environment. OBJECTIVE: The present study aimed to assess the level of knowledge, attitudes, and practices of small-scale vegetable farmers towards the use of pesticides in Ethiopia along the Lake Ziway watershed. METHODS: This was a cross-sectional study involving a total of 210 farmers randomly selected during a period of pesticide application from a purposively selected village located in the immediate vicinity of Lake Ziway, Ethiopia. Data were generated through structured in-depth interviews and on-site observations on farms. A Chi-square test was applied to evaluate whether the collected data and their probable associations were significant. RESULTS: World Health Organization (WHO) class II pesticides (moderately toxic) were the most frequently used pesticides in the study area. There was no reported use of WHO classes 1a and 1b and banned or restricted pesticides such as dichlorodiphenyltrichloroethane (DDT) and endosulfan. Most (92%) farmers reported indiscriminately disposing of empty containers in the field, while 86.7% applied the leftover pesticides to other crops. More than 90% of small-scale farmers did not use any personal protective equipment (PPE) when handling pesticides. About 95% of farmers had poor knowledge regarding pesticides. A significant association (p < 0.001) was observed between the knowledge of farmers and their practices related to pesticides. CONCLUSIONS: Generally, the knowledge of small-scale farmers on pesticides was poor. Moreover, the inappropriate disposal of pesticides and pesticide containers poses a risk to the environment. The findings of the present study underline the need to train farmers concerning the safe and proper use of pesticides to mitigate hazards to human health and the environment. PARTICIPANT CONSENT: Obtained. ETHICS APPROVAL: The study was granted an exemption from requiring ethics approval from the Hawassa University College of Natural and Computational Science, Research and Review Committee. COMPETING INTERESTS: The authors declare no competing financial interests.