RESUMEN
Trace metals and metalloids are groups of chemical elements that naturally occur in low concentrations and cycle in the environment driven by natural processes and human activities. They have a persistent and bio-accumulative tendency in the environment, and certain trace metals and metalloids have become a public health concern. This study assesses the concentration of eleven trace metals and a metalloid in sediments and catfish muscle from five study sites in the Eastern Tanzanian River basin. Forty catfish tissues and fifteen sediment samples were collected and analyzed using ICP-MS. Concentrations of As, Cd, Co, Pb, and Zn did not exceed the United States Environmental Protection Agency (USEPA) guideline for pollution of sediments, while Al Cr, Al, Mn, and V with values ranging from (118.54 to 70154.55) indicating moderately polluted. The stations Java-Sadaani and Matandu showed the highest Cr, Ni, and Cu concentrations, but the potential ecological risk index (RI) was low (RI < 95). In the catfish muscle tissue, the levels of Cd, Pb, Cu, and Zn did not surpass the EU and FAO/WHO limits and results ranged from 2.22 to 35.22mg/kg. Low levels of accumulation of Cd, Pb, and As were found in this study compared to catfish muscles from other studies, whereas the concentrations of other trace metals and metalloids analyzed had comparable results. Biota/sediment accumulation factors (BSAF) were all < 1. The weekly metal intake (MWI) results ranged from 6.89E-04 to 2.43E+01 µg/know-1week-1, indicating a low risk as the value did not exceed the FAO/WHO established Permissible Tolerable Weekly Intake (PTWI). The non-carcinogenic health risk result THQ was 4.43E-02 and the carcinogenic health risks result HI was 4.42E-05 which indicated tolerable levels of risks as both the values of the Target Hazard Quotient (THQ) and the Hazard Index (HI) was < 1, and the carcinogenic target risk (TR) is < 0.0001. The highest TR values were observed for Cr and Ni. We recommend a continued monitoring of the changes in trace metal levels in the environment and biota together with continuous public health education on the dangers of high levels of trace metals.
Asunto(s)
Arsénico , Bagres , Sedimentos Geológicos , Músculos , Contaminantes Químicos del Agua , Animales , Bagres/metabolismo , Sedimentos Geológicos/análisis , Sedimentos Geológicos/química , Contaminantes Químicos del Agua/análisis , Tanzanía , Arsénico/análisis , Músculos/química , Músculos/metabolismo , Monitoreo del Ambiente/métodos , Oligoelementos/análisis , Ríos/químicaRESUMEN
BACKGROUND: Cholera, one of the world's deadliest infectious diseases, remains rampant and frequent in Tanzania and thus hinders existing control measures. The present study was undertaken to evaluate the occurrence of toxigenic Vibrio cholerae O1 in wastewater, fish and vegetables during a non-outbreak period in Morogoro, Tanzania. METHODS: From October 2014 to February 2015, 60 wastewater samples, 60 fish samples from sewage stabilization ponds and 60 wastewater irrigated vegetable samples were collected. Samples were cultured for identification of V. cholerae using conventional bacteriological methods. Isolates were confirmed as V. cholerae by detection of the outer membrane protein gene (ompW) using polymerase chain reaction (PCR). Isolates were further tested for antibiotic susceptibility and presence of virulence genes including, cholera enterotoxin gene (ctx), the toxin co-regulated pilus gene (tcpA) and the haemolysin gene (hlyA). RESULTS: The prevalence of V. cholerae in wastewater, vegetables and fish was 36.7, 21.7 and 23.3 %, respectively. Two isolates from fish gills were V. cholerae O1 and tested positive for ctx and tcpA. One of these contained in addition the hlyA gene while five isolates from fish intestines tested positive for tcpA. All V. cholerae isolates were resistant to ampicillin, amoxicillin and some to tetracycline, but sensitive to gentamicin, chloramphenicol, and ciprofloxacin. CONCLUSIONS: Our results show that toxigenic and drug-resistant V. cholerae O1 species are present and persist in aquatic environments during a non-cholera outbreak period. This is of public health importance and shows that such environments may be important as reservoirs and in the transmission of V. cholerae O1.