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Persistent organic pollutants (POPs) are ubiquitous contaminants with adverse health effects in the ecosystem. One of such effects is endocrine disruption in humans and wildlife even at background exposure concentrations. This study assessed maternal breastmilk concentrations of POPs; brominated flame retardants (BFRs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), and the potential health risks posed to the nursing infants. We also evaluated the association of these POPs with total 3,3',5-triiodo-L-thyronine (T 3 ), L-thyroxine (T 4 ), and 3,3',5'-triiodo-L-thyronine (rT 3 ) levels measured in human breast milk. Thirty breastmilk samples were collected from Kampala, Uganda between August and December 2018. Hexabromobenzene was not detected while the maximum level of 2,2',4,4',5,5'-hexabrombiphenyl was 64.7 pg/g lw. The median levels of total indicator PCBs, PBDEs, dioxin-like PCBs, and PCDD/Fs in the samples were 159 pg/g lw, 511 pg/g lw, 1.16 pg TEQ/g lw, and 0.4 pg TEQ/g lw, respectively. These levels were lower than those reported in other countries. Owing to their bio accumulative nature, PCBs -81, -169, and ∑PCDD/Fs increased with increase in maternal age. Estimated dietary intakes for dioxin-like PCBs and PCDD/Fs were lower than those reported elsewhere but were higher than the WHO tolerable daily intakes suggesting potential health risks to nursing infants. In adjusted single pollutant models, PCB-126, PCB-169, and ∑PCB TEQ were negatively associated with T 3 , while 1,2,3,4,5,7,8-HpCDF was positively associated with rT 3 . Although these associations did not persist in multipollutant models, our findings suggest potential thyroid hormone disruption by POPs in mothers. This may reduce the levels of thyroid hormones transferred from the mother to the neonates and, hence, adversely influence infant growth. A temporal study with a bigger sample size is required to corroborate these findings., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Per- and polyfluoroalkyl substances (PFASs) are known organic pollutants with adverse health effects on humans and the ecosystem. This paper synthesises literature about the status of the pollutants and their precursors, identifies knowledge gaps and discusses future perspectives on the study of PFASs in Africa. Limited data on PFASs prevalence in Africa is available because there is limited capacity to monitor PFASs in African laboratories. The levels of PFASs in Africa are higher in samples from urban and industrialized areas compared to rural areas. Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are the dominant PFASs in human samples from Africa. Levels of PFOS and PFOA in these samples are lower than or comparable to those from industrialized countries. PFOA and PFOS levels in drinking water in Africa are, in some cases, higher than the EPA drinking water guidelines suggesting potential risk to humans. The levels of PFASs in birds' eggs from South Africa are higher, while those in other environmental media from Africa are lower or comparable to those from industrialized countries. Diet influences the pollutant levels in fish, while size and sex affect their accumulation in crocodiles. No bioaccumulation of PFASs in aquatic systems in Africa could be confirmed due to small sample sizes. Reported sources of PFASs in Africa include municipal landfills, inefficient wastewater treatment plants, consumer products containing PFASs, industrial wastewater and urban runoff. Relevant stakeholders need to take serious action to identify and deal with the salient sources of PFASs on the African continent., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental pollutants with adverse effects on the foetus and infants. This study aimed at assessing in utero exposure levels and transplacental transfer (TPT) characteristics of BDE congeners in primiparous mothers from Kampala, the capital city of Uganda. Paired human samples (30 placenta and 30 cord blood samples) were collected between April and June 2018; and analysed for a suite of 24 tri-to deca-BDE congeners. Extraction was carried out using liquid-liquid extraction and sonication for cord blood and placenta samples, respectively. Clean-up was done on a solid phase (SPE) column and analysis was performed using gas chromatography/mass spectrometry (GC/MS). Total (∑) PBDEs were 0.25-30.9 ng/g lipid weight (lw) (median; 7.11 ng/g lw) in placental tissues and 1.65-34.5 ng/g lw (median; 11.9 ng/g lw) in cord blood serum, with a mean difference of 1.26 ng/g lw between the compartments. Statistical analysis showed no significant difference between the levels of PBDEs in cord blood and placenta samples (Wilcoxon signed rank test, p = 0.665), possibly because foetus and neonates have poorly developed systems to metabolise the pollutants from the mothers. BDE-209 was the dominant congener in both matrices (contributed 40.5% and 51.2% to ∑PBDEs in placenta and cord blood, respectively), suggesting recent and on-going maternal exposure to deca-BDE formulation. Non-significant associations were observed between ∑PBDEs in maternal placenta and maternal age, household income, pre-pregnancy body mass index (BMI), and beef/fish consumption. This suggested on-going exposure to PBDEs through multiple sources such as dust from indoor/outdoor environments and, ingestion of other foods. Based on absolute concentrations, the extent of transplacental transport was greater for higher congeners (BDE-209, -206 and -207) than for lower ones (such as BDE-47), suggesting alternative TPT mechanisms besides passive diffusion. More studies with bigger sample sizes are required to confirm these findings., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The aim of this study was to investigate levels of polybrominated diphenyl ethers (PBDEs) in breast milk samples from healthy primiparous mothers who had lived in Kampala capital city (urban area) and Nakaseke district (a rural area) for the last five years. Fifty samples were collected between March and June 2018 and were extracted by dispersive solid-phase extraction (SPE). Clean-up was performed on an SPE column and analysis was done using gas chromatography-mass spectrometry. Total (∑) PBDEs (BDE 28, 47, 49, 66, 77, 99, 100,138,153, 154, 183 and 209) ranged from 0.59 to 8.11 ng/g lipid weight (lw). The levels of PBDEs in samples from Kampala capital city were significantly higher than those from Nakaseke (p < 0.01, Mann-Whitney U test). The most dominant congeners were BDE-209 and -47 (contributed 37.1% and 20.2%, respectively to ∑PBDEs), suggesting recent exposure of mothers to deca-and penta-BDE formulations. Fish and egg consumption, plastics/e-waste recycling and paint fumes were associated with higher levels of BDE-47, -153 and -99, respectively, implying that diet and occupation were possible sources of the pollutants. Estimated dietary intakes (ng kg -1 body weight day -1 ) for BDE-47, -99 and -153 were below the US EPA reference doses for neurodevelopmental toxicity, suggesting minimal health risks to nursing infants who feed on the milk. Generally, the risk quotients for BDE-47, -99 and -153 were <1 in majority (96%) samples, indicating that the breast milk of mothers in Uganda was fit for human consumption., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This paper reviews literature for the last two decades with emphasis on levels, toxic equivalencies and sources of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in Africa. Further, we comprehensively analysed data, interpret differences and identify existing gaps with those from other continents. We observed that high levels of PCDD/Fs and dl-PCBs were reported in environmental and biological samples near densely populated urban and industrialised areas compared to those in rural settings. In general, the concentrations of PCDD/Fs and dl-PCBs in the blood samples from Africa were in the same range as those from Asia but lower than those from Europe. The concentrations of dioxins and dioxin-like compounds in the atmosphere in Africa were comparable to and/or higher than those in developed countries. The reported sources of PCDD/Fs and dl-PCBs in Africa were industrial emissions, obsolete pesticide stockpiles, household heating, recycling of electronic waste, and incineration and combustion of domestic waste. Regional and intercontinental transport of dioxins could not be confirmed because of the lack of sufficient literature on them. Further data about the levels and sources of PCDD/Fs and dl-PCBs in Africa need to be generated to complete the chemical inventories for the continent and to facilitate the implementation of the Stockholm Convention on persistent organic pollutants. The reviewed literature shows that most analyses have been carried out in laboratories outside Africa because of the limited institutional capacity in Africa. More support needs to be given to laboratories in Africa to develop the capacity to accurately quantify dioxins on routine basis., (Copyright © 2019 Elsevier Ltd. All rights reserved.)