Contamination and ecological risk assessment of toxic metals in Awetu watershed stream waters and sediments, Ethiopia.

The study analyzed the contamination level and ecological risk assessment of toxic metals Awetu watershed streams. A total of 20 water and 20 sediment samples were collected and analyzed for the toxic metals of Arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), tin (Sn), and zinc (Zn). Sediment samples showed severe contamination levels based on ranges in sediment quality guidelines (SQGs). Water samples showed high grades of contamination factor and potential ecological risk factor by toxic metals. The synergistic effects of toxic metals in the sampling sites were evaluated by Nemerow pollution index, potential ecological risk index and modified degree of contamination and were found to have similar results. Dololo stream (D1, D2, D3, and D4) and Kito (K1, K2, and K3) were found at 'toxic' contamination and 'severe' ecological risk. Cd, Mn, Ni, Pb, and Sn contributed to the highest ecological risk. Toxic metal contamination in Dololo stream is attributed to institutions carrying out various anthropogenic activities along the stream bank, including traditional metal plating, garages, laboratory effluents, extensive agriculture, carwash, irresponsible waste disposal, and urban population growth. The result shows Awetu watershed streams are seriously contaminated by toxic metals. Therefore, future pollution control and management plans should accentuate the strict regulation of discharge of wastes from these anthropogenic activities.

Correction: Exposure to organochlorine pesticides as a predictor to breast cancer: A case-control study among Ethiopian women.

[This corrects the article DOI: 10.1371/journal.pone.0257704.].

Exposure to organochlorine pesticides as a predictor to breast cancer: A case-control study among Ethiopian women.

Breast cancer (BC) is becoming one of the most prevalent non-infectious disease in low and middle income countries. The steady rise of BC incidence may be related to the different risk factors. Among many, rampant presence of environmental pollutants might be one of the risk factors. Therefore, the aim of this study is to investigate exposure to organochlorine pesticides as a risk factor to breast cancer. A case-control study design was employed among breast cancer patients and non-breast cancer individuals (controls). Blood samples were collected from 100 study participants (50 cases and 50 controls) followed by serum separation, extraction and cleanup using standard analytical procdures. The findings revealed that ten organochlorine pesticides were detected in the serum of the study participants. From the detected organochlorine pesticides, heptachlor was observed at higher concentration for breast cancer patients (6.90±4.37 µg/L) and controls (9.15±3.84 µg/L). Mean serum level of p,p'-DDE, p,p'-DDT, heptachlor, gamma-chlordane, endosulfan, and dibutyl-chlorendate were significantly higher in the serum of breast cancer patients than the controls. From the studied pesticides, p,p'-DDT and gamma-chlordane are significant predictors for BC, while, others are equivocal. A unit increment of the concentration of p,p'-DDT (AOR; 2.03, 95% CI: 1.041-3.969) increased the odds of developing breast cancer by two, while for gamma-chlordane (AOR;3.12, 95% CI; 1.186-8.203) by three. Our study results suggesting that, organochlorines are a risk factors for breast cancer in Ethiopia. Decreasing exposure to such organochlorines might have a significant public health relevance in reducing non-communicable chronic illnesses. Besides, continues monitoring of persistent organic pollutants using body biomarkers is important for disease prevention and device mitigation measures.

Corrigendum to "Organochlorine pesticide residues in tea and their potential risks to consumers in Ethiopia" [Heliyon 7 (7) (July 2021) e07667].

[This corrects the article DOI: 10.1016/j.heliyon.2021.e07667.].

Sources and level of heavy metal contamination in the water of Awetu watershed streams, southwestern Ethiopia.

The present study aimed to investigate the contamination source, level, and spatial distribution of globally alarming trace metals from Awetu watershed streams, southwestern Ethiopia. Surface water samples were collected from 20 sampling sites in December 2019. Water samples were collected in 500 ml polyethylene bottles previously washed with deionized water and rinsed with the sample to be collected from different stretches and acidified with 5 ml concentrated nitric acid. The samples were digested with open acid digestion and the contents of the metal were analysed using inductively coupled plasma optical emission spectrometry (ICP-OES) ranged from 18 - 351 µg/L for As, 5-19 µg/L for Cd, 232-421 µg/L for Cr, 314-920 µg/L for Pb and 10-16 µg/L for Hg. The highest concentrations of As were detected at K3, Cd at K2, Pb and Cr at D4, and Hg at D5. Analysis of variance results revealed that the Cd concentrations were statistically significant among all the streams except for Boye. Streams found at the center of Jimma city with effluents emanated from Jimma University, garage maintenances, car-wash and agricultural areas had higher values than the streams in the periphery. This study concluded that a higher concentration of trace elements is associated with the type of waste entering the streams. Trace elements concentration in the watershed is to the level that can pose a risk to downstream users. Public awareness creation to establish waste management systems and river quality monitoring should be implemented to minimize the public health risk and deterioration of the aquatic ecosystem.