Heavy metals in farmed and wild milkfish (Chanos chanos) and wild mullet (Mugil cephalus) along the coasts of Tanzania and associated health risk for humans and fish

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.

Prenatal exposure to persistent organic pollutants in Northern Tanzania and their distribution between breast milk, maternal blood, placenta and cord blood

Human exposure to persistent organic pollutants (POPs) begins during pregnancy and may cause adverse health effects in the fetus or later in life. The present study aimed to assess prenatal POPs exposure to Tanzanian infants and evaluate the distribution of POPs between breast milk, maternal blood, placenta and cord blood. For assessment of prenatal exposure, 48 maternal blood samples from Mount Meru Regional Referral Hospital (MMRRH), Arusha Tanzania, were analyzed for organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs), dioxin-like (DL) activity and perfluorinated alkyl substances (PFASs). For evaluation of POPs distribution between maternal/infant compartments, breast milk, placenta and cord blood corresponding to the maternal blood were analyzed for OCPs, PCBs and BFRs. In maternal blood, p,p´- DDE was detected in 100% of the samples ranging between 29 and 1890 ng/g lipid weight (lw). PCB-153 was the only PCB detected in maternal blood, with detection rate of 29% and concentrations up to 116 ng/g lw. BDE-47 was detected in 65% of the maternal blood samples, ranging between <LOD and 83.2 ng/g lw. DL activity was measured using Dioxin Responsive CALUX® bioassay. The DL activity was above LOQ in 92% of the samples, ranging from <LOQ to 114 pg CALUX TEQ/g lw. PFASs was dominated by PFOS and PFOA, however, the concentrations were low (range ∑PFASs 0.18-3.14 ng/mL). p,p´-DDE was detected in 100% of the breast milk, placenta and cord blood samples and the concentrations were strongly correlated (r = 0.89-0.98) between all compartments. Maternal blood (MB) had significantly lower p,p´-DDE concentrations (ng/g lw) than cord blood (CB) and breast milk (BM). The median CB/MB ratio was 1.3 and median MB/BM ratio was 0.8. p,p´-DDE concentrations in breast milk and cord blood did not show significant difference and median CB/BM ratio was 1. In addition, the relative p,p`-DDE transfer from maternal blood to breast milk and to cord blood increased when p,p`-DDE concentrations in maternal blood increased. This study shows that Tanzanian infants are exposed to a wide range of POPs during fetal life, which raise concerns for potential health effects. In addition, this study found that maternal blood concentrations may lead to underestimation of prenatal exposure, while breast milk collected close to delivery may be a more suitable indicator of prenatal exposure.

Occurrence and levels of persistent organic pollutants (POPs) in farmed and wild marine fish from Tanzania. A pilot study

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. ∑₁₀PCBs levels were low, ranging from <LOD to 8.13 ng/g lw with the highest mean level found in farmed milkfish from Shakani, Unguja (3.94 ng/g lw). The PCB pattern was dominated by PCB -153 > -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.

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in human breast milk and associated health risks to nursing infants in Northern Tanzania

This is the first study to report organochlorines (OCs), including chlorinated pesticides (OCPs) and polychlorinated biphenyls (PCBs) in human milk from Tanzania. The main aims of this study were to assess the level of contamination and the possible health risks related to OC exposure in nursing infants from the Northern parts of Tanzania. Ninety-five healthy mother-infant couples attending Mount Meru Regional Referral Hospital (MMRRH), Arusha, Tanzania, were assessed for associations between maternal/infant characteristics, i.e. mother's age, BMI, gestational weight gain, occupation, residence and fetal growth parameters and breast milk levels of OCPs, such as dichlorodiphenyltrichloroethane (DDT) and its metabolites, dieldrin and PCBs. p,p'-DDE and p,p'-DDT were detected in 100% and 75% of the breast milk samples, respectively, and ranged between 24 and 2400ng/g lipid weight (lw) and <LOD and 133ng/g lw, respectively. Dieldrin was detected in 66% of the samples in levels up to 937ng/g lw. ∑7PCBs ranged between <LOD and 157ng/g lw. Other OCPs were detected in low levels. For assessment of health risks, the Hazard Quotient (HQ) was calculated by comparing estimated daily intakes of OCPs and PCBs with health based guidance values. The estimated daily intake (ng/kg body weight/day) of ∑DDTs, dieldrin and nondioxin-like PCBs (∑6PCBs) exceeded the provisional tolerable daily intake (PTDI) in two, six and forty-eight of the nursing infants, respectively, suggesting potential health risks. In addition, head circumference were negatively associated with p,p´-DDE in female infants, suggesting that OC exposure during pregnancy may influence fetal growth.

Brominated flame retardants (BFRs) in breast milk and associated health risks to nursing infants in Northern Tanzania

The main aim of this study was to assess brominated flame retardants (BFRs) in breast milk in the Northern parts of Tanzania. Ninety-five colostrum samples from healthy, primiparous mothers at Mount Meru Regional Referral Hospital (MMRRH), Arusha Tanzania, were analyzed for polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), hexabromobenzene (HBB), (2,3-dibromopropyl) (2,4,6-tribromophenyl) ether (DPTE), pentabromoethylbenzene (PBEB) and 2,3,4,5,6-pentabromotoluene (PBT). The Ʃ7PBDE (BDE 28, 47, 99, 100, 153, 154, 183) ranged from below level of detection (<LOD) to 785ng/g lipid weight (lw). BDE 47, 99, 100 and 153 were the dominating congeners, suggesting recent and ongoing exposure to banned, commercial PentaBDE mixture. A multiple linear regression model revealed that mothers eating clay soil/Pemba during pregnancy had significantly higher levels of BDE 47, 99, 100 and 153 in their breast milk than mothers who did not eat clay soil/Pemba. Infant birth weight and birth length were significantly correlated with the levels of BDE 47, 99, 100 and 153. The estimated daily intake (ng/kg body weight/day) of BDE 47 and 99 exceeded the US EPA Reference doses (RfD) in four and eight mothers, respectively, suggesting a potential health risk to the nursing infants.