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This study aimed at investigating the levels and distribution of progesterone in receiving waters and wastewaters in Arusha, a fast-growing urban area and the third largest city in Tanzania. Specifically, the study was conducted along the Themi River and the adjacent waste stabilization ponds (WSPs). Progesterone was detected and quantified by using an enzyme-linked immunosorbent assay (ELISA) kit. For Themi River samples, the level of progesterone obtained ranged from 'no detection' to 439 ng/L with a mean value of 120.3 ng/L. The levels detected were significantly higher in the midstream than the upstream and downstream sections of the river (P<0.05). The higher values at the midstream were attributable to livestock, WSPs and household effluents; agricultural activities; and sewage infiltration. Progesterone levels in the present study, although not extremely high, correspond to those associated with harmful effects in other studies. Results for samples collected from the WSPs indicated a release of 215 ng progesterone per L of the receiving waters. Although progesterone removal efficiency by the WSPs was 75%, the amount released was still high enough to cause harm to aquatic organisms. Thus, more efficient techniques are required to adequately remove progesterone to the recommended levels.

In 2016, farmed milkfish (Chanos chanos) from Tanzania mainland (Mtwara), and Zanzibar islands (Pemba and Unguja) and wild milkfish and mullet (Mugil cephalus) from the Indian Ocean were collected for analyses of heavy metals (Pb, Cd, Hg, As, Al, Fe, Zn, Cu, Ni, Co and Cr) in muscles and livers. High concentrations of Pb were detected in muscles and livers from wild and farmed milkfish and wild mullet from all sites. The highest concentration of Pb was detected in wild milkfish liver from Mtwara (47.4 mg/kg ww). The Pb concentrations in fish muscle exceeded maximum levels (ML) set by FAO/WHO (0.3 mg/kg ww) in 100% of the analysed fish. Concentrations of Pb were higher in wild fish than in farmed fish. Cd concentrations were generally low. The comparison of the Hg concentration with EQS Biota indicated that Hg might pose potential health risk to 22% of the analysed fish. Median concentrations of Fe in livers from farmed milkfish from Jozani and Shakani, Zanzibar, were 40-80 times higher than the other sites. Assessment of human health risk and exposure to heavy metals indicated no potential risk from consuming the fish from the present study locations. However, the Pb concentrations exceeding ML in the fish suggests that Pb may affect the health of fish. Future investigations should include regular monitoring of heavy metals in farmed and wild fish in Tanzania for further development of sustainable aquaculture and the welfare of the wild fish stock in the coastal waters., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In 2016, farmed and wild milkfish (Chanos chanos) and mullet (Mugil cephalus) from Tanzania mainland (Mtwara) and Zanzibar islands (Pemba and Unguja) were collected for analyses of persistent organic pollutants (POPs). Fish livers were analysed for organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs). Muscle tissue was used for analyses of perfluoroalkyl substances (PFASs). The major contaminant was p,p'-DDE. The highest p,p'-DDE concentration was found in wild milkfish from Mtwara (715.27 ng/g lipid weight (lw)). This was 572 times higher than the maximum level detected in farmed milkfish from the same area. The ratios of p,p'-DDE/p,p'-DDT in wild milkfish and mullet from Mtwara and Pemba indicate historical use of DDT. In contrast, ratios in farmed milkfish from Unguja and Mtwara, suggest recent use. The levels of HCB, HCHs and trans-nonachlor were low. ∑ 10 PCBs levels were low, ranging from  -180> -138. PBDEs were detected in low and varying levels in all locations. BDE-47 was the dominating congener, and the highest level was found in farmed milkfish from Jozani (1.55 ng/g lw). HBCDD was only detected in wild mullet from Pemba at a level of 16.93 ng/g lw. PFAS was not detected in any of the samples. POP levels differed between geographic areas and between farmed and wild fish. Human activities seem to influence levels on PCBs and PBDEs on Unguja., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The coastal population in East Africa is growing rapidly but sewage treatment and recycling facilities in major cities and towns are poorly developed. Since estuarine mangroves are the main hotspots for pollutants, there is a potential for contaminants to accumulate in edible fauna and threaten public health. This study analysed trace metals in muscle tissues of the giant mud crabs (Scylla serrata) and the giant tiger prawns (Penaeus monodon) from the Tanzanian coast, in order to determine the extent of bioaccumulation and public health risks. A total of 180 samples of muscle tissues of S. serrata and 80 of P. monodon were collected from nine sites along the coast. Both species showed high levels of trace metals in the wet season and significant bioaccumulation of As, Cu and Zn. Due to their burrowing and feeding habits, mud crabs were more contaminated compared to tiger prawns sampled from the same sites. Apart from that, the measured levels of Cd, Cr and Pb did not exceed maximum limits for human consumption. Based on the current trend of fish consumption in Tanzania (7.7 kg/person/year), the measured elements (As, Cd, Co, Cu, Mn, Pb and Zn) are not likely to present health risks to shellfish consumers. Nevertheless, potential risks of As and Cu cannot be ruled out if the average per capita consumption is exceeded. This calls for strengthened waste management systems and pollution control measures.

The genetic diversity of giant tiger prawns in relation to trace metals (TMs) pollution was analysed using 159 individuals from eight sites at the Tanzanian coast. The seven microsatellites analysed showed high degree of polymorphism (4-44 alleles). The measured genetic diversity (H o =0.592±0.047) was comparable to that of populations in the Western Indian Ocean. Apart from that, correlation analysis revealed significant negative associations between genetic diversity and TMs pollution (p<0.05), supporting the genetic erosion hypothesis. Limited gene flow was indicated by a significant genetic differentiation (F ST =0.059, p<0.05). The Mantel test rejected the isolation-by-distance hypothesis, but revealed that gene flow along the Tanzanian coast is limited by TMs pollution. This suggests that TMs affect larvae settlement and it may account for the measured deficiency of heterozygosity. This calls for strengthened pollution control measures in order to conserve this commercially important species., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Mangroves ecosystems support livelihood and economic activities of coastal communities in the tropics and subtropics. Previous reports have documented the inefficiency of waste treatment facilities in Tanzania to contain trace metals. Therefore, the rapidly expanding coastal population and industrial sector is likely to threaten mangrove ecosystems with metal pollution. This study analysed trace metals in 60 sediment samples and 160 giant tiger prawns from the Tanzanian coast in order to document the distribution of trace metals and to establish if measured levels present a threat to mangrove fauna and are of public health importance. High levels of Cr, Co, Cu, Fe, Mn, Ni, and V was observed in mangroves of river Pangani, Wami, and Rufiji. Multivariate analysis showed that they originate mainly from weathering and erosion in the river catchments. Extreme enrichment of Cd was observed in a mangrove affected by municipal sewage. The distribution of Hg, Pb, and Zn was related with urbanisation and industrial activities along the coast. The metal pollution index was high at Pangani, Saadani, and Rufiji, suggesting that these estuarine mangroves are also affected by human activities in the catchment. Moderate to considerable ecological risks were observed in all sampled mangroves, except for Kilwa Masoko. It was revealed that As, Cd, and Hg present moderate risks to fauna. High levels of Cu, Fe and Zn were observed in prawns but the level of the non-essential Cd, Hg, and Pb did not exceed the maximum allowed levels for human consumption. However, based on the trends of fish consumption in the country, weekly intake of Hg is likely to exceed provisional tolerable weekly intake level, especially in fishing communities. This calls for measures to control Hg emissions and to strengthen sewage and waste treatment in coastal cities and urban centres in the basin of major rivers., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The interactive effects of mixed pollutants in sewage wastewater on biomarker responses were investigated using wild male African sharptooth catfish (Clarias gariepinus) in Morogoro, Tanzania. A total of 58 fish were used, of which 21 were from Mindu dam (reference site) and 22, 9 and 10 from Mafisa, Mazimbu and Mzumbe sewage ponds, respectively. Liver somatic index (LSI) and gonadosomatic index (GSI) were significantly greater (two- to threefold) and (five- to sixfold), respectively, in fish from all sewage ponds. Haemoglobin concentration and gill filament 7-ethoxyresurufin O-deethylase (EROD) activities were significantly higher (1.2-fold and twofold, respectively) in fish from Mzumbe sewage ponds than in fish from Mindu dam, whereas liver EROD activity was significantly higher in fish from Mzumbe and Mafisa sewage ponds (5-fold). A HPLC method for determination of enzymatically formed p-nitrophenyl-glucuronide (PNPG) was developed and applied to measure UDP-glucuronosyl transferase (UGT) activities that was significantly higher in fish from all sewage ponds (2-2.5-fold) than in fish from Mindu dam. Kinetic characteristics and assay dependence of UGT were studied with microsomal preparations. Metallothionein (MT) content was significantly lower (three- to fourfold) in fish from sewage ponds than in fish from Mindu dam, and corresponded with cumulative levels of cadmium, lead and mercury. Condition factor, vitellogenin (Vtg), acetylcholinesterase (AChE) activities in plasma, eyes and brain, haematocrit, plasma protein and cytosolic glutathione S-transferase (GST) activities were comparable in fish from sewage ponds and Mindu dam. Although specific pollutants other than the metals were not identified by chemical analysis, application of a suite of biomarkers in C. gariepinus demonstrated that all sewage ponds were contaminated by pollutants of public health concern.

Dose dependent effects of Benzo[a]pyrene (BaP) on cytochrome P4501A (CYP1A), glutathione-S-transferase (GST) and fluorescent aromatic compounds (FACs) metabolites biomarker responses were studied in African sharptooth catfish (Clarias gariepinus) following 24 h of waterborne exposures. Based on biomass of C. gariepinus in different tanks, BaP concentrations of 1.60, 3.44, and 18.21 microg/L that corresponded to 0.5, 1.0, and 5.0 mg/kg body weight were used. Significant induction of EROD activities in gill filaments was observed at all doses and the accumulation of FACs metabolites in bile was significantly different between groups. Accumulation of FACs metabolites in bile strongly correlated (r (2) = 0.99) with BaP doses. Hepatic EROD activities were undetectable and no effect on GST activities was observed. The highest dose of BaP from the dose dependent study was further studied to assess the interactive and temporal responses of C. gariepinus on CYP1A, GST, and FACs metabolites biomarkers following exposure to either BaP alone, 17alpha-ethynylestradiol (EE(2)) alone or a combination of both compounds at concentrations of 54.17 microg/L for BaP, 51.38 microg/L for EE(2) and 54.44 microg/L for each of both compounds. Based on biomass in each tank, these concentrations corresponded to 5 mg/kg body weight. While a group of six fish was sacrificed on day 0 from the control tank only, other groups of six fish were sacrificed after 1, 3, and 6 days of exposure from the control and exposed groups. Maximum induction of gill filament and hepatic EROD activities was observed after 1 day of exposure. Both EROD activities in gill filaments and liver were significantly induced by exposure to BaP alone or co-administration with EE(2). Gill filament EROD induction was significantly inhibited (50%) by co-administration of BaP and EE(2) compared to administration of BaP alone. Levels of FACs in bile for BaP and BaP + EE(2) exposed groups were significantly different from the control at all doses and time points. A significant induction of GST activities was observed in fish exposed to BaP and BaP + EE(2) after 3 days. Exposure to EE(2) alone caused significant induction of this enzyme after day 6. This study reports for the first time the significant antagonistic influence of EE(2) on BaP in gills of fish following waterborne exposures. The results also indicate that chemical mixtures may affect biomarker responses differently from compounds administered alone and that the sensitivity of CYP1A to interactive chemicals is different in gills and liver.

The ability of African sharptooth catfish (Clarias gariepinus) in inducing cytochrome P-450 class 1A (CYP1A) and glutathione S-transferase (GST) biomarkers was determined in liver and gill filaments after 4 days of waterborne exposure to the polycyclic aromatic hydrocarbon, benzo[a]pyrene (B[a]P). Male (n=6) and female (n=6) fish were exposed to B[a]P added to the water (30 microg/l) corresponding to 5 mg/kg total body weight. Five female and six male fish, exposed to acetone alone added to the water served as controls. The 7-ethoxyresurufin-O-deethylase (EROD) activity was measured in hepatic microsomes and gill filaments. In addition, GST activity was determined in the hepatic cytosolic fraction and fluorescent aromatic compounds (FACs) in bile and biliverdin. Benzo[a]pyrene strongly induced EROD activities in gill filaments of both sex. Levels of FACs per ml of bile were 17-fold higher in exposed fish compared to the controls. Correlations between induction of EROD activities in gill filaments and liver and between induction of EROD activities in gill filaments and levels of biliary FACs metabolites were strong. GST activities in the hepatic cytosolic fraction were similar amongst the treated and control groups. This is the first report on studies determining EROD activities in gill filaments and hepatic tissue, FACs in bile and GST in hepatic tissues of C. gariepinus after waterborne exposure to B[a]P. The findings suggest that the gill filament-based EROD assay in C. gariepinus can be used to monitor the pollution of AhR agonists in aquatic ecosystems in eastern and southern African countries.