Environmental levels and human body burdens of per- and poly-fluoroalkyl substances in Africa: A critical review

Identification and quantification of novel per- and polyfluoroalkyl substances (PFAS) contamination in a Great Lakes urban-dominated watershed

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic organic fluoro-compounds that are oil-, water-, and flame-resistant, making them useful in a wide range of commercial and consumer products, as well as resistant to environmental degradation. To assess the impact of urbanization and wastewater treatment processes, surface water and sediment samples were collected at 27 sites within the Great Lakes in the Lake Huron to Lake Erie corridor (HEC), an international waterway including the highly urbanized Detroit and Rouge Rivers. Samples were analyzed for 92 PFAS via UHPLC-MS/MS. Our previous data in the HEC found the highest amount of PFAS contamination at the Rouge River mouth. In addition to evaluating the input of the Rouge River into the HEC, we evaluated the transport of PFAS into the HEC from other major tributaries. PFAS were detected in both surface water and sediment at all sites in this study, with a total of 10 congeners quantified in all surface water samples and 16 congeners quantified in all sediment samples, indicating ubiquitous contamination. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) were pervasive in the HEC as these two compounds were detected in all sites and matrices, often at concentrations above the US EPA's recommended lifetime interim updated health advisories. Surface water samples contained more perfluorohexanoic acid (PFHxA) than any other congener, with average aqueous PFHxA across all surface water samples exceeding the average concentration previously reported in the Great Lakes. Sediment samples were dominated by PFOS, but novel congeners, notably 3-Perfluoropentyl propanoic acid (FPePA), were also quantified in sediment. The Rouge River and other tributaries contribute significantly to the PFAS burden in the HEC including Lake Erie. Overall, our results indicate the need for expanding toxicological research and risk assessment focused on congeners such as PFHxA and PFAS mixtures, as well as regulation that is tighter at the onset of production and encompasses PFAS as a group at a national level.

Environmental health science research: opportunities and challenges for some developing countries in Africa

Due to ongoing developmental projects, there is a need for regular monitoring of the impact of pollutants on the environment. This review documented the challenges and opportunities in the field of environmental health sciences in some African countries. A systematic review was used to investigate opportunities and challenges in the field of environmental health science in Africa by examining published work with a specific focus on Africa. The reports showed that funding and infrastructure as the major problems. The study also highlighted recruiting study participants, retention, and compensation as a bane in the field in Africa. The absence of modern equipment also hinders research. The review, however, noted research collaboration from the region including studies on emerging pollutants such as pharmaceuticals, per and polyfluoroalkyl substances (PFAS), and microplastic (MPs) as great opportunities. The study concluded that collaboration with other continents, exchange programs and improved governmental interventions may help.

Predicting the dynamics of per- and polyfluoroalkyl substances in coastal regions of Africa: vulnerability index and adverse ecological pathways from remote-sensed variables

This study aimed to predict the dynamics of per- and polyfluoroalkyl substance (PFAS) contamination and ecological vulnerability within coastal regions of Africa utilizing time-averaged remote-sensed data patterns from 2020 to 2023. The analysis identified PFAS contamination hotspots along the coast of Africa, particularly in western Africa around Nigeria and in areas spanning Equatorial Guinea and Guinea-Bissau, with risk influenced by eastward wind patterns, overland runoff, and elevated aerosol optical depth (AOD) values. Regional trends indicated that variations in solar energy absorption and surface air temperature could influence PFAS dynamics in North Africa, South Africa, East Africa, and West Africa. In North Africa, intermediate overland runoff and lower sea-surface temperatures were observed. In South Africa, there were intermediate runoff levels and warmer sea-surface temperatures. East Africa experienced intermediate runoff as well. In West Africa, there was increased susceptibility to high overland runoff and aerosol-related PFAS contamination. From the weighted vulnerability index, significant disparities in environmental conditions across African coastal regions revealed that North Africa had relatively lower vulnerability, while West Africa had the highest susceptibility to per- and polyfluoroalkyl substance (PFAS) contamination. This study emphasizes the necessity for region-specific vulnerability index models and targeted mitigation strategies to address diverse ecological and health risks from PFAS contamination along the African coast. Regional and international collaboration, spearheaded by organizations such as the AU and ECOWAS, is essential, with tailored policies aligned with the SDGs, Agenda 2063, and NEPAD crucial for effective environmental management, urging policymakers to prioritize cooperation and resource sharing for comprehensive sustainability goals.

Biological effects of perfluoroalkyl substances on running water ecosystems: A case study in Beiluo River, China

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are emerging contaminants that pose a threat to the biodiversity of the Beiluo River, a polluted watercourse on the Loess Plateau impacted by diverse human activities. However, the occurrence, spatial distribution, and substitution characteristics of PFASs in this region remain unclear. This study aimed to unravel PFAS distribution patterns and their impact on the aquatic ecosystems of the Beiluo River Basin. The total PFAS concentration in the area ranged from 16.64-35.70 ng/L, with predominantly perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs), collectively contributing 94%. The Mantel test revealed threats to aquatic communities from both legacy long-chain (perfluorooctanoic acid and sodium perfluorooctane sulfonic acid) and emerging (6:2 fluorotelomer sulfonic acid, 2-Perfluorohexyl ethanoic acid, and hexafluoropropylene oxide dimer acid (Gen-X)) PFSAs. The canonical correspondence analysis ordination indicated that trace quantities of emerging PFASs, specifically 2-Perfluorohexyl ethanoic acid and hexafluoropropylene oxide dimer acid (Gen-X), significantly influenced geographical variations in aquatic communities. In conclusion, this study underscores the importance of comprehensively exploring the ecological implications and potential risks associated with PFASs in the Beiluo River Basin.

Perturbation of IP3R-dependent endoplasmic reticulum calcium homeostasis by PPARδ-activated metabolic stress leads to mouse spermatocyte apoptosis: A direct mechanism for perfluorooctane sulfonic acid-induced spermatogenic disorders

Perfluorooctane sulfonic acid (PFOS) as an archetypal representative of per- and polyfluoroalkyl substances (PFAS) is ubiquitously distributed in the environment and extensively detected in human bodies. Although accumulating evidence is suggestive of the deleterious effects of PFOS on male reproduction, the direct toxicity of PFOS towards spermatogenic cells and the relevant mechanisms remain poorly understood. The aims of the present study were to explore the direct effects and underlying molecular mechanisms of PFOS on spermatogenesis. Through integrating animal study, transcriptome profiling, in silico toxicological approaches, and in vitro validation study, we identified the molecular initiating event and key events contributing to PFOS-induced spermatogenic impairments. The mouse experiments revealed that spermatocytes were involved in PFOS-induced spermatogenic disorders and the activation of peroxisome proliferator-activated receptor delta (PPARδ) was linked to spermatocyte loss in PFOS-administrated mice. GC-2spd(ts) cells were treated with an increased gradient of PFOS, which was relevant to environmental and occupational exposure levels of PFOS in populations. Following 72-h treatment, cells was harvested for RNA sequencing. The transcriptome profiling and benchmark dose (BMD) modeling identified endoplasmic reticulum (ER) stress as the key event for PFOS-mediated spermatocyte apoptosis and determined the point-of-departure (PoD) for perturbations of ER stress signaling. Based on the calculated PoD value, further bioinformatics analyses combined with in vitro and in vivo validations showed that PFOS caused metabolic stress by activating PPARδ in mouse spermatocytes, which was responsible for Beclin 1-involved inositol 1,4,5-trisphosphate receptor (IP3R) sensitization. The disruption of IP3R-mediated ER calcium homeostasis triggered ER calcium depletion, leading to ER stress and apoptosis in mouse spermatocytes exposed to PFOS. This study systematically investigated the direct impacts of PFOS on spermatogenesis and unveiled the relevant molecular mechanism of PFOS-induced spermatogenic disorders, providing novel insights and potential preventive/therapeutic targets for PFAS-associated male reproductive toxicity.

Endocrine disrupting chemicals in wastewater treatment plants in Kenya, East Africa: Concentrations, removal efficiency, mass loading rates and ecological impacts

This study investigated the levels, mass loadings, removal efficiency, and associated ecotoxicological risks of selected endocrine disrupting chemicals (EDCs), namely, dibutylphthalate (DBP), diethylhexylphthalate (DEHP), dimethylphthalate (DMP), linuron (LNR) and progesterone (PGT) in wastewater, sludge, and untreated dry biosolid (UDBS) samples from twelve wastewater treatment plants (WWTPs) in nine major towns in Kenya. Analysis was done using high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (LC-MS/MS). All the wastewater influents had quantifiable levels of EDCs with DBP being the most abundant (37.49%) with a range of 4.33 ± 0.63 to 19.68 ± 1.24 μg L-1. DEHP was the most abundant in sludge and accounted for 48.2% ranging between 278.67 and 9243.49 ng g-1 dry weight (dw). In the UDBS samples, DEHP was also the most abundant (40%) of the total EDCs detected with levels ranging from 78.77 to 3938.54 ng g-1 dw. The average removal efficiency per pollutant was as follows: DMP (98.7%) > DEHP (91.7%) > PGT (83.4%) > DBP (77.9%) > LNR (72.2%) which can be attributed to sorption onto the biosolid, biological degradation, photolysis, and phytoremediation. The pH was negatively correlated to the EDC concentrations while total dissolved solids (TDS), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), and electrical conductivity (EC) were positively correlated. The mass loadings were as high as 373.33 g day-1 of DBP in the treatment plants located in densely populated cities. DEHP and PGT had their Risk Quotients (RQs) > 1, posing a high risk to biota. DMP, DBP, and LNR posed medium risks as their RQ values were between 0.1 and 1. EDCs are therefore loaded to environmental compartments through either the effluent that loads these pollutants into the receiving aquatic ecosystem or through the UDBS, which are used as fertilizers in agricultural farmlands causing potential toxicological risks to aquatic and terrestrial life.

Predictors of serum- per- and polyfluoroalkyl substance (PFAS) concentrations among infants in Guinea-Bissau, West Africa

BACKGROUND

Knowledge about PFAS exposure in Africa is limited. We have previously detected six types of PFAS in the serum of infants from Guinea-Bissau, West Africa. The aim of this study was to identify predictors of the infant serum-PFAS concentrations.

METHODS

This cross-sectional study was based on a subset of data from a randomized controlled trial of early measles vaccination performed in 2012-2015 in three rural regions of Guinea-Bissau. Blood samples were obtained from 237 children aged 4-to-7 months, and six types of PFAS were quantified in serum. Location of residence was recorded, and information about predictors related to socioeconomic status as well as maternal and child characteristics were obtained through structured interviews with the mothers through routine surveillance. Associations between potential predictors and infant serum-PFAS concentrations were examined in linear regression models while adjusting for potential confounding and mediating factors as identified in a directed acyclic graph.

RESULTS

Infants from the Cacheu region had the lowest concentrations of perfluorooctanoic acid (PFOA), while infants from the Oio region had the lowest concentrations of all other PFAS. Compared to infants from Oio, infant serum-perfluorooctane sulfonic acid (PFOS) concentrations were 94.1% (95% CI: 52.4, 147.1%) and 81.9% (95% CI: 45.7, 127.1%) higher in Cacheu and Biombo, respectively. Higher maternal age and lower parity were associated with slightly higher child-serum perfluorohexane sulfonic acid (PFHxS) concentrations, while infants with higher socioeconomic status and infants breastfed without supplementary solid foods at inclusion had higher average concentrations of most PFAS, although the confidence intervals were wide and overlapped zero.

DISCUSSION

Location of residence was the most important determinant of serum-PFAS concentrations among Guinea-Bissau infants, indicating a potential role of diet as affected by the global spread of PFAS, but future studies should explore reasons for the regional differences in PFAS exposure.

Water quality of The Gambia River: A prospective drinking water supply

Drinking water in The Gambia is mostly derived from boreholes that could potentially be contaminated. The Gambia River, a major river in West Africa that covers 12 % of the country's area, could be more exploited for drinking water supply. During the dry season, the total dissolved solids (TDS), ranging from 0.02 to 33 g/L in The Gambia River, decreases with the distance to the river mouth with no major inorganic contamination. The freshwater (<0.8 g/L TDS) starts from Jasobo at approximately 120 km from the river mouth and extends by about 350 km to the eastern border of The Gambia. With a dissolved organic carbon (DOC) ranging from 2 to 15 mgC/L, the natural organic matter (NOM) of The Gambia River was characterised by 40-60 % humic substances of paedogenic origin. With such characteristics, unknown disinfection by-products could be formed if chemical disinfection, such as chlorination, was implemented during treatment. Out of 103 types of micropollutants, 21 were detected (4 pesticides, 10 pharmaceuticals, 7 per- and polyfluoroalkyl substances (PFAS)) with concentrations ranging from 0.1 to 1500 ng/L. Pesticides, bisphenol A and PFAS concentrations were below the stricter EU guidelines set for drinking water. These were mainly confined to the urban area of high population density near the river mouth, while the quality of the freshwater region of low population density was surprisingly pristine. These results indicate that The Gambia River, especially in its upper regions, would be well suited as a drinking water supply when using decentralised ultrafiltration treatment for the removal of turbidity, as well as, depending on pore size, to a certain extent microorganisms and DOC.

Electronic-waste-associated pollution of per- and polyfluoroalkyl substances: Environmental occurrence and human exposure

Occupational exposure to per- and polyfluoroalkyl substances (PFASs) is of serious concern because their adverse health effects. Nevertheless, knowledge regarding contamination in e-waste dismantling regions is rather scarce. We therefore analysed seven neutral PFASs (n-PFASs) and forty ionized PFASs (i-PFASs) in dust and hand wipes collected from an e-waste dismantling plant and homes. Both dust (1370 ng/g) and workers' hand wipe (1100 ng/m²) in e-waste dismantling workshops contained significantly higher median levels of ∑PFASs than those from homes (684 ng/g and 444 ng/m²) (p < 0.01). ∑PFAS concentrations in dust and on workers' hand wipes from workshops were significantly higher than those from storage area. 8:2 fluorotelomer alcohol was the dominant n-PFAS in workshop dust (70.7%) and on worker's hand wipes (46.6%). Perfluoroalkyl carboxylic acids (C2 -C3) were the significant components (based on concentration) of i-PFASs in dust (57.9%) and on hand wipes (89.6%). A significant positive correlation (p < 0.001) of ∑PFAS concentrations between workshop dust and workers' hand wipes was observed, indicating that they come from common sources. Compared to dust ingestion, hand-to-mouth contact was highlighted as a vital exposure route, accounting for 68.8% for workers and 72.2% for residential population, respectively, of the sum of two exposure doses.

Development of a GIS-based knowledge hub for contaminants of emerging concern in South African water resources using open-source software: Lessons learnt

With population growth and dwindling freshwater sources, protecting such sources has come to the forefront of water resource management. Historically, society's response to a problem is based on funding availability, current threat, and public outcry. Achieving this is largely dependent on the knowledge of the factors that are resulting in compromised water sources. These factors are constantly changing as novel contaminants are introduced into surface water sources. As we are in the information age, the interest in contaminants of emerging concern (CEC) is gaining ground. Whilst research is being conducted to identify contaminants in South African water sources, the research outputs and available information is not collated and presented to the science community and stakeholders in readily available formats and platforms. Current research outcomes need to be made known to regulators in order to develop environmental laws. By using fourth industrial revolution technology, we were able to collate available data in literature and display these in a user-friendly online format to regulatory bodies as well as researchers. A standardized excel spreadsheet was developed and uploaded to a PostgreSQL, running a PostGIS extension and was then processed in the GeoServer to allow for visualization on an interactive map which can be continuously updated. The near real-time access to information will reduce the possibility of duplication of research efforts, enhance collaboration in the discipline, and act as a CEC early warning system.

Overview of African water resources contamination by contaminants of emerging concern

This review look at several classes of contaminants of emerging concern (CECs) in conventional and non-conventional water resources across the African continent's five regions. According to the review, pharmaceuticals, endocrine-disrupting chemicals, personal care products, pesticides, per- and polyfluoroalkyl compounds, and microplastics were found in conventional and non-conventional water resources. Most conventional water resources, such as rivers, streams, lakes, wells, and boreholes, are used as drinking water sources. Non-conventional water sources, such as treated wastewater (effluents), are used for domestic and agricultural purposes. However, CECs remain part of the treated wastewater, which is being discharged to surface water or used for agriculture. Thus, wastewater (effluent) is the main contributor to the pollution of other water resources. For African countries, the prevalence of rising emerging pollutants in water poses a severe environmental threat. There are different adverse effects of CECs, including the development of antibiotic-resistant bacteria, ecotoxicological effects, and several endocrine disorders. Therefore, this needs the urgent attention of the African Union, policymakers, Non-Governmental Organizations, and researchers to come together and tackle the problem.

Occurrence characteristics and health risk assessment of per- and polyfluoroalkyl substances from water in residential areas around fluorine chemical industrial areas, China

Recently, identifying the contamination status and assessing the health risk of per- and polyfluoroalkyl substances (PFASs) in surface water and groundwater have been of great significance. Eighteen individual PFASs were analyzed in thirty-three surface/groundwater samples during one period in a fluorine chemical park (Park A) and during two periods in Park B. The mean total concentration of 18 PFASs (∑PFASs) in Park A (9104.63 ng·L^-1) was significantly higher than that in the wet season (WS) (801.68 ng·L^-1) or DS (714.64 ng·L^-1) in Park B. The perfluorobutane sulfonate (PFBS) was the predominant substance in the two parks, and the maximum concentration in groundwater exceeded 10,000 ng·L^-1. The contamination status in the wet season (WS) was higher than that in the dry season (DS) in Park B. The ∑PFASs in Park A presented an increasing tendency following the groundwater flow direction, whereas this rule was limited to all periods in Park B. Two relative source contributions (RSCs) of 20% or 100% allowed assessing the PFASs risk to different age groups, and the results revealed that some PFASs (4 ≤ C ≤ 7 or 9 ≤ C ≤ 12) were identified as having a low risk quotient (RQ), except for perfluorooctane sulfonate (PFOS) and PFOA (C = 8). The RQ_mix value mainly relies on PFOA and PFOS, with a larger contribution rate of 80-90%. All assessed cases (case 1, case 2, case 3, and case 4) in all age groups revealed that infants were vulnerable to PFASs influence, followed by children, teenagers, and adults.

Occurrence and Distribution of Per- and Polyfluoroalkyl Substances from Multi-Industry Sources to Water, Sediments and Plants along Nairobi River Basin, Kenya

Per- and polyfluoroalkyl substances (PFAS) are ever-present pollutants in the environment. They are persistent and bio-accumulative with deleterious health effects on biota. This study assesses the levels of PFAS in environmental matrices along the Nairobi River, Kenya. An aggregate of 30 PFAS were determined in water, while 28 PFAS were detected in sediments and plants using solid phase extraction then liquid chromatography–mass spectrometric techniques. In water, higher levels of perfluoroundecanoic acids of up to 39.2 ng L−1 were observed. Sediment and plant samples obtained in the midstream and downstream contained higher levels of perfluorooctanoic acid of up to 39.62 and 29.33 ng g−1, respectively. Comparably, levels of long-chain PFAS were higher in water and sediments than in plants. Sediment/water log distribution of selected PFAS ranged between 2.5 (perfluoroundecanoic acid) and 4.9 (perfluorooctane sulfonate). The level of perfluorooctane sulfonate (1.83 ng L−1) in water is above the acceptable level in surface water posing high human health and ecological risks. The observed PFAS concentrations and distribution were attributed mainly to multi-industries located along the river, among other sources. The knowledge of PFAS occurrence and distribution in Nairobi River, Kenya, provides important information to local regulatory agencies for PFAS pollution control.

Suspect screening to support source identification and risk assessment of organic micropollutants in the aquatic environment of a Sub-Saharan African urban center

Organic micropollutants (OMPs) are contaminants of global concern and have garnered increasing attention in Africa, particularly in urban and urbanizing areas of Sub-Saharan Africa (SSA). In this work, we coupled suspect screening enabled by liquid chromatography-high-resolution mass spectrometry (LC-HRMS) with multivariate analysis to characterize OMPs in wastewater, surface water, and groundwater samples collected from Kampala, the capital and largest city of Uganda. Suspect screening prioritized and confirmed 157 OMPs in Kampala samples for target quantification. Many OMPs detected in Kampala samples occurred within concentration ranges similar to those documented in previous studies reporting OMP occurrence in SSA, but some have never or rarely been quantified in environmental water samples from SSA. Hierarchical cluster analysis established the source-related co-occurrence profiles of OMPs. Partial least squares regression and multiple linear regression analyses further pinpointed the concentration of nitrate and the content of a fluorescent organic matter component with excitation/emission maxima around 280/330 nm as predictors for the sample-specific cumulative concentrations of OMPs, suggesting the likely contribution of diffuse runoff and wastewater discharges to OMP occurrence in the aquatic environment of Kampala. Parallel calculations of exposure-activity ratios and multi-substance potentially affected fractions provided insights into the potential for biological effects associated with OMPs and highlighted the importance of expanded analytical coverage for screening-level risk assessments. Overall, our study demonstrates a versatile database-driven screening and data analysis methodology for the multipronged characterization of OMP contamination in a representative SSA urban center.

The Next Frontier of Environmental Unknowns: Substances of Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCBs)

Substances of unknown or variable composition, complex reaction products, or biological materials (UVCBs) are over 70 000 "complex" chemical mixtures produced and used at significant levels worldwide. Due to their unknown or variable composition, applying chemical assessments originally developed for individual compounds to UVCBs is challenging, which impedes sound management of these substances. Across the analytical sciences, toxicology, cheminformatics, and regulatory practice, new approaches addressing specific aspects of UVCB assessment are being developed, albeit in a fragmented manner. This review attempts to convey the "big picture" of the state of the art in dealing with UVCBs by holistically examining UVCB characterization and chemical identity representation, as well as hazard, exposure, and risk assessment. Overall, information gaps on chemical identities underpin the fundamental challenges concerning UVCBs, and better reporting and substance characterization efforts are needed to support subsequent chemical assessments. To this end, an information level scheme for improved UVCB data collection and management within databases is proposed. The development of UVCB testing shows early progress, in line with three main methods: whole substance, known constituents, and fraction profiling. For toxicity assessment, one option is a whole-mixture testing approach. If the identities of (many) constituents are known, grouping, read across, and mixture toxicity modeling represent complementary approaches to overcome data gaps in toxicity assessment. This review highlights continued needs for concerted efforts from all stakeholders to ensure proper assessment and sound management of UVCBs.

A Critical Review on Transplacental Transfer of Per- and Polyfluoroalkyl Substances: Prenatal Exposure Levels, Characteristics, and Mechanisms

Prenatal exposure to perfluoroalkyl and polyfluoroalkyl substances (PFASs) has aroused public concerns as it can pose multiple health threats to pregnant women and cause adverse birth outcomes for fetuses. In previous studies, the prenatal exposure levels and transplacental transfer efficiencies (TTE) of PFASs have been reported and discussed. Specifically, the binding affinities between PFASs and some transporters were determined, demonstrating that the TTE values of PFASs are highly dependent on their binding behaviors. To summarize primary findings of previous studies and propose potential guidance for future research, this article provides a systematic overview on levels and characteristics of prenatal exposure to PFASs worldwide, summarizes relationships between TTE values and structures of PFASs, and discusses possible transplacental transfer mechanisms, especially for the combination between PFASs and transporters. Given the critical roles of transporters in the transplacental transfer of PFASs, we conducted molecular docking to further clarify the binding behaviors between PFASs and the selected transporters. We proposed that the machine learning can be a superior method to predict and reveal behaviors and mechanisms of the transplacental transfer of PFASs. In total, this is the first review providing a comprehensive overview on the prenatal exposure levels and transplacental transfer mechanisms of PFASs.

Major contaminants of emerging concern in soils: a perspective on potential health risks

Soil pollution by the contaminants of emerging concern (CECs) or emerging contaminants deserves attention worldwide because of their toxic health effects and the need for developing regulatory guidelines. Though the global soil burden by certain CECs is in several metric tons, the source-tracking of these contaminants in soil environments is difficult due to heterogeneity of the medium and complexities associated with the interactive mechanisms. Most CECs have higher affinities towards solid matrices for adsorption. The CECs alter not only soil functionalities but also those of plants and animals. Their toxicities are at nmol to μmol levels in cell cultures and test animals. These contaminants have a higher propensity in accumulating mostly in root-based food crops, threatening human health. Poor understanding on the fate of certain CECs in anaerobic environments and their transfer pathways in the food web limits the development of effective bioremediation strategies and restoration of the contaminated soils and endorsement of global regulatory efforts. Despite their proven toxicities to the biotic components, there are no environmental laws or guidelines for certain CECs. Moreover, the information available on the impact of soil pollution with CECs on human health is fragmentary. Therefore, we provide here a comprehensive account on five significantly important CECs, viz., (i) PFAS, (ii) micro/nanoplastics, (iii) additives (biphenyls, phthalates), (iv) novel flame retardants, and (v) nanoparticles. The emphasis is on (a) degree of soil burden of CECs and the consequences, (b) endocrine disruption and immunotoxicity, (c) genotoxicity and carcinogenicity, and (d) soil health guidelines.

Distribution of perfluoroalkyl substances (PFASs) in water, sediment, and fish tissue, and the potential human health risks due to fish consumption in Lake Hawassa, Ethiopia

Due to their global distribution, persistence, bioaccumulative potential and toxicity, perfluoroalkyl substances (PFASs) are considered as hazardous chemicals. Although many studies on PFASs pollution in aquatic environments have been done in the Northern hemisphere, less is known on PFASs pollution in African aquatic ecosystems and the risks they pose to humans through consumption of contaminated biota. The objective of this study was to determine the spatial distribution of PFASs in water, sediment, and fish tissue in Lake Hawassa, Ethiopia, and to investigate possible human health risks due to fish consumption. Among the PFASs detected in water and sediment, perfluorooctanoic acid (PFOA) was the most abundant with mean concentrations of 6.93 ng/L and 0.23 ng/g dw respectively. Long-chained PFASs dominated the PFAS accumulation profiles in fish tissues, with higher concentrations measured in liver compared to muscle tissue. The detected concentrations of PFASs were, however, often similar to those reported in other African aquatic ecosystems. This study showed no potential health risk due to consumption of contaminated fish based on mean concentrations and fish consumption. However, it is expected that peoples who consume more fish (fishermen and local peoples living close to Lake Hawassa) may suffer health risks due to PFASs contamination.

Contaminants of Emerging Concern in the Lower Volta River, Ghana, West Africa: The Agriculture, Aquaculture, and Urban Development Nexus

Contaminants of emerging concern (CECs) are ubiquitous in aquatic environments across all continents and are relatively well known in the developed world. However, few studies have investigated their presence and biological effects in low- and middle-income countries. We provide a survey of CEC presence in the Volta River, Ghana, and examine the microbial consequences of anthropogenic activities along this economically and ecologically important African river. Water and sediment samples were taken by boat or from shore at 14 sites spanning 118 km of river course from the Volta estuary to the Akosombo dam. Sample extracts were prepared for targeted analysis of antimicrobial CECs, N,N-diethyl-meta-toluamide, and per- and polyfluoroalkyl substances (PFAS; water only). Concurrent samples were extracted to characterize the microbial community and antibiotic-resistant genes (ARGs). Antibiotics and PFAS (PFAS, 2-20 ng/L) were found in all water samples; however, their concentrations were usually in the low nanograms per liter range and lower than reported for other African, European, and North American studies. N,N-Diethyl-meta-toluamide was present in all samples. The number of different genes detected (between one and 10) and total ARG concentrations varied in both water (9.1 × 10^-6 to 8.2 × 10^-3 ) and sediment (2.2 × 10^-4 to 5.3 × 10^-2 ), with increases in gene variety at sites linked to urban development, sand mining, agriculture, and shellfish processing. Total ARG concentration spikes in sediment samples were associated with agriculture. No correlations between water quality parameters, CEC presence, and/or ARGs were noted. The presence of CECs in the lower Volta River highlights their global reach. The overall low concentrations of CECs detected is encouraging and, coupled with mitigation measures, can stymie future CEC pollution in the Volta River. Environ Toxicol Chem 2022;41:369-381. © 2021 SETAC.

Emerging contaminant exposure to aquatic systems in the Southern African Development Community

The growing production and use of chemicals and the resultant increase in environmental exposure is of particular concern in developing countries where there is rapid industrialization and population growth but limited information on the occurrence of emerging contaminants. Advances in analytical techniques now allow for the monitoring of emerging contaminants at very low concentrations with the potential to cause harmful ecotoxicological effects. Therefore, we provide the first critical assessment of the current state of knowledge about chemical exposure in waters of the Southern African Developmental Community (SADC). We achieved this through a comprehensive literature review and the creation of a database of chemical monitoring data. Of the 59 articles reviewed, most (n = 36; 61.0%) were from South Africa, and the rest were from Botswana (n = 6; 10.2%), Zimbabwe (n = 6; 10.2%), Malawi (n = 3; 5.1%), Mozambique (n = 3; 5.1%), Zambia (n = 2; 3.4%), Angola (n = 1; 1.7%), Madagascar (n = 1; 1.7%), and Tanzania (n = 1; 1.7%). No publications were found from the remaining seven SADC countries. Emerging contaminants have only been studied in South Africa and Botswana. The antiretroviral drug ritonavir (64.52 µg/L) was detected at the highest average concentration, and ibuprofen (17 times) was detected most frequently. Despite being the primary water source in the region, groundwater was understudied (only 13 studies). High emerging contaminant concentrations in surface waters indicate the presence of secondary sources of pollution such as sewage leakage. We identify research gaps and propose actions to assess and reduce chemical pollution to enable the SADC to address the Sustainable Development Goals, particularly Goal 3.9, to reduce the deaths and illnesses from hazardous chemicals and contamination. Environ Toxicol Chem 2022;41:382-395. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A review on degradation of perfluorinated compounds based on ultraviolet advanced oxidation

Perfluorinated compounds (PFCs), as emerging persistent pollutants, can exist for a long time in the environment due to their high stability. PFCs have been detected in drinking water, wastewater, and the human body. Studies have shown that PFCs pose a threat to human health and the ecological environment, which is expected to be listed in new drinking water regulations. Traditional processes, including coagulation, biological filtration, chlorination, ozonolysis, and ultraviolet light have ineffective removal efficiency on PFCs; however, advanced oxidation processes (AOP) based on ultraviolet (UV) light have good application prospects for the removal of PFCs. This study provides an overview of the removal of PFCs by UV-based AOPs; systematically introduces the research status of various UV-based AOPs from the perspectives of degradation pathways, degradation efficiency, influencing factors, formation of by-products; and comprehensively compares these different UV-based AOPs. Finally, the limitations of existing research and future research needs are discussed. This review aims to provide an overview for a better understanding of the degradation status and prospects of UV-based AOPs for the degradation of PFCs.

Risks posed by per- and polyfluoroalkyl substances (PFAS) on the African continent, emphasizing aquatic ecosystems

Per- and polyfluoroalkyl substances (PFAS) are organic pollutants that may have adverse effects on the ecosystem. Despite the global presence of PFAS, knowledge of PFAS on the African continent is limited because monitoring of PFAS is challenging and often not feasible owing to the lack of analytical capacity and high cost. However, it is necessary to understand the environmental risks posed by these chemicals in developing countries, because increasing urbanization will likely increase PFAS contamination in the environment. Although, as far as is known, PFAS concentrations in the African aquatic environment are generally lower than in more developed countries, exceedances of ecological quality standards (EQS) were reported in a few cases, providing evidence of potential ecological risks to these ecosystems. However, the number of ecosystems at risk will likely increase as urbanization and modernization increase in African countries. Therefore, environmental regulations should be updated and implemented to reduce further contamination of the aquatic environment with these chemicals. In addition, analytical laboratories in Africa should develop their capacity to detect PFAS and related compounds regularly and routinely. Local hot spots need to be identified, the influence of these hot spots on the PFAS burden in the environment should be investigated, and environmental regulations should be implemented for these hot spots to reduce their environmental impact. Therefore, we recommend a more routine monitoring of PFAS, including new PFAS that are currently used as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) alternatives, which are not regulated and environmentally concerning. Integr Environ Assess Manag 2021;17:726-732. © 2021 SETAC.

Per and polyfluoroalkyl substances scientific literature review: water exposure, impact on human health, and implications for regulatory reform

Among other emerging contaminants in water, per and polyfluoroalkyl substances (PFASs) have garnered international attention from the scientific community on a global scale. Some countries, such as the United States, have found that PFASs are present in humans on a wide scale. Although two PFASs have been widely studied-Perfluorooctanoic acid and Perfluorooctanesulfonic acid-many more PFASs are being created by industry and are either not known, not studied, or both. The objective of this literature review on PFASs is to give an overview of the information available about PFASs related to human exposure. The information from this literature review on the exposure of humans to PFASs through drinking water and the lack of many conventional drinking water treatment systems' ability to remove PFASs (particularly short-chain PFASs) suggests that current regulatory limits are insufficient to adequately protect humans. This is especially true for particularly vulnerable populations such as infants, young children, and developing children (pubescent). The gaps in the current knowledge and in current regulatory approaches could have long-term effects on human health.

Legacy and emerging per- and polyfluoroalkyl substances (PFASs) in Dagang Oilfield: Multimedia distribution and contributions of unknown precursors

A systematic survey was conducted on twenty-six per- and polyfluoroalkyl substances (PFASs) in fifty-one paired samples of surface water, sediment, and soil from Dagang Oilfield, Tianjin, China. Perfluorooctanoic acid, perfluorooctane sulfonic acid, p-perfluorous nonenoxybenzenesulfonate (OBS), and 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) were ubiquitous in the oilfield with field log K_d of 1.3-2.2, indicating a high partition potential from surface water to sediment. Total petroleum hydrocarbons (TPH) are a predictor for PFAS contamination at oilfield. The concentrations of OBS and 6:2 FTAB were higher in surface water and sediment with elevated TPH level. With total oxidizable precursor assay, unknown precursors for C2-C3 perfluoroalkyl carboxylic acids (PFCAs) (57-99 mol%) contributed more than those for C4-C12 PFCAs in the three mediums. The unknown C4-, C6-, and C8-based precursors tended to be precursors for perfluoroalkyl sulfonates at the oilfield, and C8 fluorotelomer-based precursors particularly occurred in the surface water. The concentrations of C4- and C8-based precursors were found positively correlated with TPH levels (r = 0.67-0.72, p < 0.05), while C6 precursors may also come from other sources. Further studies are necessary to clarify the mass balance and risk assessment for unknown PFASs.

Per- and Polyfluoroalkyl Substances in Human Serum Samples of Selected Populations from Ghana

The aims of this study were to assess serum concentrations of per- and polyfluoroalkyl substances (PFASs) in selected populations from Ghana, including workers engaged in the repair of electronic equipment (ERWs), and to elucidate PFAS concentrations in relation to blood mercury concentrations (B-Hg) as a biomarker of seafood consumption. In all, 219 participants were recruited into the study, of which 26 were women and 64 were ERWs. Overall, the PFAS concentrations were low. The most abundant components were perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonic acid (PFHxS). Women had generally lower PFAS concentration than men. The ERWs had statistically significantly higher concentrations of perfluorooctanoate (PFOA), which was associated with the concentration of tin in urine. This could indicate exposure during soldering. The concentration of B-Hg was associated with several of the PFASs such as PFOA, PFOS and perfluoroheptane sulfonate (PFHpS). Additionally, the concentrations of perfluorodecanoic acid (PFDA) and perfluoroundecanoate (PFUnDA) were highly associated with the concentrations of B-Hg. It is noteworthy that the linear isomer of PFHxS was strongly associated with B-Hg while the branched isomers of PFHxS were not. In conclusion, the PFAS concentrations observed in the present study are low compared to other populations previously investigated, which also reflects a lower PFAS exposure within the Ghanaian cohorts. ERWs had significantly higher PFOA concentrations than the other participants. Several PFASs were associated with B-Hg, indicating that seafood consumption may be a source of PFAS exposure.

Fluorotelomer Alcohols' Toxicology Correlates with Oxidative Stress and Metabolism

Fluorotelomer alcohols (FTOHs) are widely used as industrial raw materials due to their unique hydrophobic and oleophobic properties. However, because of accidental exposure to products containing FTOHs or with the widespread use of FTOHs, they tend to contaminate the water and the soil. There are reports demonstrating that FTOHs can cause various harmful effects in animals and humans (for example, neurotoxicity, hepatotoxicity, nephrotoxicity, immunotoxicity, endocrine-disrupting activity, and developmental and reproductive toxicities). Oxidative stress is related to a variety of toxic effects induced by FTOHs. To date, few reviews have addressed the relationship between the toxicity of FTOHs and oxidative stress. This article summarises research demonstrating that the toxicity induced by FTOHs correlates with oxidative stress and metabolism. Furthermore, during the metabolic process of FTOHs, a number of cytochrome P450 enzymes (CYP450) are involved and many metabolites are produced by these enzymes, which can induce oxidative stress. This is also reviewed.