1 Introduction

Per- and polyfluoroalkyl substances (PFAS) are synthetic materials with unusual physicochemical characteristics. For example, they can survive high temperatures, tolerate chemical reactions, and have emulsifying and surfactant properties. They are also referred to as forever chemicals owing to their persistence in environment. Since the 1950s, PFAS have been utilized internationally for a range of industrial and consumer uses, including carpets, water-repellent fabrics, frying-pans, pesticides, cosmetics and paints owing to their qualities [1, 2]. They are extremely persistent chemicals that are present in the environment constantly due to their extensive application. PFAS have been found in treated water, wastewater treatment plants, landfill leachate, soil, sediments, surface and groundwater [3,4,5,6,7]. There are significant environmental problems associated with the expanding usage of PFAS in both household and industrial products. Nations like Australia, the United States of America, Canada, United Kingdom, European Union, and most recently China have implemented institutional and scholarly efforts to address PFAS over the last decade [8,9,10].

High amounts of PFAS are still discovered in the world's aquatic systems despite the Stockholm Convention on persistent organic pollutants, which forbids industry from creating specific forms of PFAS world [11]. PFAS contamination in Africa as well as its threat on ecosystem and human health are little understood in spite of their widespread use globally [12]. Additionally, the usage of substitute PFAS is growing without adequate understanding of their potential dangers and emission sources [13]. As a result, there is an urgent need for PFAS monitoring in environmental matrices. Policy makers and health authorities should pay attention to PFAS as a public health hazard.

Previous reviews on PFAS have primarily been conducted in high-income countries [7]. Academics in the developed world lamented on data scarcity on the occurrence of forever chemicals in Africa [9, 14,15,16]. The assessment of PFAS in low-and middle-income countries (LMICs) is crucial because of the populations' continual growth and adoption of new, sophisticated consumer patterns.

The generation of data on the environmental risks of PFAS in LMICs will help decision makers design, modify, and put into practice regulatory procedures for the environmental management of PFAS [17]. In this survey, the regulation and advisory limit of PFAS in various countries, its sources and occurrence, characteristics, environmental fate, different methods on sampling and analysis in Africa is broadly discoursed and analyzed.

2 Results

2.1 The Prescribed/Normal Level as Reported by International Agencies for PFAS in Different Sources

Most high-income countries have set guidelines and regulations on limits for PFAS in food and environmental matrix due to their wide use, persistence, widespread and ecological contamination. Recently, the European Union (EU) set regulation for maximum concentrations of PFAS such as perfluorononanoic acid (PFNA), perfluorohexane sulfonic acid (PFHxS), perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in foodstuffs (see Table 1) [18]. In Canada, there are guidelines for some of these chemicals in soil and drinking water [19] (see Tables 2 and 3). The Australian Government Department of Health have set guidelines for PFOA at 560 ng/L and 70 ng/L for PFHxS and PFOS in drinking water. Moreover, there are guidelines for PFOA at 10,000 ng/L and 20,000 ng/L for total PFHxS and PFOS in Australian recreational water [20]. Zhang and others [21] reported guideline limits of 47 and 85 ng/L for PFOS and PFOA in drinking water in China. Table 3 shows the guideline for PFAS in drinking water in different countries.

Table 1 European Union regulation for PFAS in foodstuff
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Table 2 Guidelines for PFAS in soil in Canada
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Table 3 Guideline for PFAS in drinking water for different countries
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Currently, the United State Environmental Protection Agency (US EPA) reported that PFOS and PFOA could cause adverse health problems even at levels close to zero in drinking water. To this effect, they updated the guideline limits for PFOS and PFOA in drinking water to 0.02 and 0.004 ng/L, respectively [22]. This replaced the limit which was set at 70 ng/L for both PFOS and PFOA in 2016. Most researchers in Africa adopted US EPA guideline limits on PFAS due to lack of advisory threshold in the continent [23]. The reported methods for sampling and analysis of PFAS in different sources are discussed in Sect. 3.5.

2.2 Reported Value

2.2.1 Drinking Water

Drinking water contributes to 2–17% of PFAS detected in the human body [24]. In Africa, reports of PFAS in drinking water are scarce and evidence exists from only a few countries including Burkina Faso, Ivory Coast, Ghana and Uganda [25, 26]. Kaboré et al. [25] in their study reported the amount of PFAS at low concentrations in bottled and tap water from Burkina Faso and Ivory Coast. The levels of PFOS and PFOA in bottle water and tap water in Burkina Faso were 0.12–3.83 ng/L and 0.06–1.89 ng/L, respectively. Samples from Ivory Coast showed levels of 0.06–0.44 ng/L in bottle water and 0.03–1.32 ng/L in tap water (see Table 4). Nevertheless, samples from 2 tap water in Burkina Faso recorded levels up to 39 ng/L, which was due to landfill close to the water reservoir. This implies that PFAS contamination may occur from landfills. The risk assessment report indicated that the levels of PFOS and PFOA detected is safe for drinking in Burkina Faso and Ivory Coast based on the previous US EPA guideline limit of 70 ng/L. However, the detection of PFAS at 39 ng/L from 2 tap water in Burkina Faso exceeded the recent US advisory limit of 0.02 and 0.004 ng/L for PFOS and PFOA in drinking water.

Table 4 Comparison of levels of PFAS in drinking water in Africa and elsewhere
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In Ghana, PFAS have been found in tap water at extreme levels 197–200 ng/L [26]. About 99% of the mean PFAS (∑PFAS) were PFOS and PFOA. The contamination of drinking water resources with these forever chemicals at extreme levels calls for concern. Although Ghana does not produce these chemicals, they do import PFAS containing products. This reveals the limitation of conventional water treatment for complete removal of these pollutants from drinking water. Arinaitwe et al. [27] reported PFAS in tap water at level range from 1.96 to 5.38 ng/L in Uganda, which is above the recent US EPA advisory limit.

In various parts of the world, drinking water sources have been found to contain PFAS, according to recent studies. For instance, ΣPFAS was detected at elevated levels in drinking water at range between 0.1 and 502.9 ng/L in China [28, 29]. This is primarily because of the intense industrial activity and dense population in certain areas in China [28]. Munoz et al. [30] reported PFOS and PFOA at 2.6 ng/L and 2.1 ng/L after treatment of drinking water in Québec province, Canada. These concentrations exceed the recent US EPA guideline limit for PFOS and PFOA. Table 4 shows the comparison of concentration of PFAS in drinking water in Africa and elsewhere.

2.2.2 Surface Water

With typical mean annual rainfall of 497 mm, South Africa has a water shortage compared to the world average of 860 s mm [31, 32]. Rivers are possible supplies of freshwater in South Africa, therefore surface water contamination there could have a significant impact on the environment [33, 34]. Studies have indicated that the distribution of PFAS in concentrations range between 1.38 and 788 ng/L in surface water such as rivers and dams in South Africa [23, 31, 35, 36]. These surpass the recommended level of 4.4 ng/L for PFAS in surface water reported by the European Commission [24]. The high concentration of these emerging pollutants shows that there is reason to be concerned, particularly in catchments where surface water is utilized for farming or drinking purposes. The use of these contaminated surface water for farming or drinking can cause thyroid and urine acid diseases in humans [37]. Communities that are close to rivers and dams contaminated with PFAS are more vulnerable to be being exposed to it. According to Batayi et al. [23], PFAS levels in South Africa were higher during summer (wet) and lower in the winter (dry). This suggested that seasonal variations in rainfall and temperature may have influenced the levels of PFAS. The authors reported that the high concentrations of forever chemicals could be due to point source discharge from industries close to the area. Hope et al. [38] detected PFOS at 0.141 ng/L and PFOA at 0.025 ng/L in surface water samples in Mozambique. These concentrations were low and may not pose any threat based on the EU advisory limit of 4.4 ng/L for PFAS in surface water. In Zambia, PFOS and PFOA have been reported in surface water at 0.13 and 0.10 ng/L, which are minimal [39].

In West Africa, PFOS have been reported as the dominant PFAS in rivers at high levels in some samples range between 1.71 and 16.19 ng/L in Nigeria [40, 41]. Discharges of domestic and industrial waste were reported as the possible source of PFAS in the affected areas. This calls for great concern as aquatic organisms may be adversely affected and some of the rivers are main sources of water supply. PFAS have been reported at extreme levels of up to range between 2 and 398 ng/L in Ghana [26, 42]. PFOS and PFOA made up 99% of the ∑PFAS. The extreme levels of these compounds in water bodies may pose health challenges and affect aquatic organisms in the affected areas in Ghana.

Studies have indicated that PFAS were found at elevated levels of 0.4–109.4 ng/L in rivers and lakes in Kenya [43,44,45]. These can pose high ecological and human health threats within the areas of occurrence because most of the rivers were reported to be sources of domestic water. The distribution of these forever chemicals was ascribed to effluent discharge from domestic, hospital and industries in the locality [44]. In Uganda, PFAS have been found in concentration ranges of 0.08–23.8 ng/L in rivers and lakes in Uganda due to release from municipal wastewater [27, 46]. This exceeds the advisory limit of PFAS in surface water and could have adverse effects on humans and aquatic organisms such as Nile perch, Nile tilapia, tiger fish, and bargus catfish in Uganda. According to reports, PFAS have been found in level range between 0.073 and 6.93 ng/L in surface water in Ethiopia [47, 48]. These were attributed to the discharge of wastewater from industries around Hawassa city in Ethiopia [47]. Baabish et al. [39] detected PFAS in surface water in Egypt, Senegal and Tunisia at low concentrations of 0.48–0.93 ng/L, 0.12–0.41 ng/L and 0.64–0.94 ng/L, respectively. Table 5 presents the details of PFAS in surface water across Africa.

Table 5 PFAS in surface water across Africa
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2.2.3 Sediments

PFAS have also been found in sediments across Africa. It was reported in levels ranging from 1.64 to 10.29 ng/g in Nigeria [40, 41]. A study revealed that the level of PFAS in sediment increased with increase in organic matter due to the adsorption of pollutants by suspended solid particles [41]. This suggests that organic matter could affect the distribution of PFAS in sediment. The occurrence of PFAS in sediments in Nigeria was reported to be due to municipal waste and point source release from industries [40]. Figure 1 shows map of sampling locations of study on selected rivers in Nigeria.

Fig. 1
figure 1

Map of sampling locations of study on selected rivers in Nigeria [41]

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In South Africa, PFAS have been detected in sediments at high concentrations range between 2.36 and 248.14 ng/g [11, 36, 50]. This poses danger to aquatic organisms in the affected areas in South Africa. Reports have indicated that PFAS occurred at high concentrations range of 39.62–99.1 ng/g in sediments in Kenya [43, 51]. In Ethiopia, PFAS have been reported at low levels 0.22–0.55 ng/g in sediments [47, 48]. Though this may not pose danger to humans and aquatic organisms in Ethiopia, however, regular monitoring should be carried out. Table 6 presents levels of PFAS in sediments across Africa.

Table 6 Occurrence of PFAS in sediment across Africa
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2.2.4 Wastewater (Raw and Treated)

In South Africa, a study reported PFAS at elevated concentration range from 2.7 ± 2.8 to 507.9 ± 257.6 ng/L and 4.4 ± 2.6 to 94.9 ± 1.5 ng/L for influent and effluent samples from wastewater treatment plants (WWTPs) [52]. The authors stated that maximum removal efficiency obtained was 80%, which indicated that WWTPs do not remove PFAS completely from wastewater. Therefore, additional treatment process should be considered to ensure total removal of PFAS and safe discharge of effluent into water bodies.

In Kenya, PFAS have been found in wastewater at concentration ranges of 0.9–28 ng/L [53]. Additionally, it was reported that wastes collected from households, hospital, and industries were mixed. Consequently, these may contain different unknown chemicals that could have negative impact on human health and degrade surface and groundwater quality [53]. Figure 2 shows the map of reported study area in Kenya. Sahar Dalahmeh [46] observed that ∑PFAS levels ranging from5.6 to 9.1 ng/L in effluent from WWTPs were higher than the influent in the range of 3.4–5.1 ng/L in Uganda. This could be due to the interaction of PFAS with different chemicals and inefficiency of WWTPs to remove PFAS. This could pose health risk in Uganda. Details of PFAS in wastewater across Africa is presented in Table 7.

Fig. 2
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Map of Lake Victoria in Kenya showing the study area [53]

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Table 7 Occurrence of PFAS in wastewater across Africa
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2.2.5 Sludge

Sewage sludge offers an intriguing medium to track the current release of several chemicals, including PFAS, in a nation. Concentrations in sewage sludge could reflect current PFAS releases from industrial and consumer items, making it a good choice for screening current release of forever chemicals from municipalities and industries [54]. When compared to high income countries like the United States of America (USA), Europe, and Asia, the levels of PFAS in sludge samples from Africa are low, according to currently known research (see Table 8). In Nigeria, Sindiku et al. [55] detected perfluoroalkyl carboxylates (PFCAs) and perfluoroalkyl sulfonates (PFSAs) in sludge from domestic, hospital and industrial wastewater treatment plants (WWTPs). They detected PFCAs and PFSAs at level range between 0.01–0.597 ng/g and 0.014–0.540 ng/g, respectively. Hospitals sewage had the highest concentration of PFSAs at 0.539 ng/g, which was related to minor release from medical wastes containing PFAS. The levels were much lower compared to those obtained from USA, Switzerland and China in the range of26 ± 20—403 ± 127 ng/g [56], 14–600 ng/g [57] and 126–809 ng/g [58] respectively. Similarly, Chirikona et al. [53] detected PFAS at low levels in sludge samples from domestic, industrial and hospital effluents in Kenya. The authors reported levels of PFOS and PFOA in the range of 0.117–0.673 and 0.098–0.0683 ng/g, respectively. The major contribution of PFAS in the area was reported to come from wastes released from hospitals. Although low levels are reported, sludge sample are sources of forever chemicals and should be monitored nonetheless.

Table 8 Comparison of PFAS in Sludge in Africa and elsewhere
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2.2.6 Plants

There is a dearth of information on the levels of PFAS in plants across the continent. Dalahmeh et al. [46], reported PFAS in plants at concentration ranges of 0.16–0.38 ng in Uganda. The authors stated that the occurrence of these forever chemicals in plants was due to their translocation from root to stem owing to their high solubility. Chirikona et al. [43] detected PFAS in plants at concentrations up to 29.33 ng/g in Kenya, which can cause bioaccumulation in humans due to consumption of such contaminated plants. Table 9 shows details of PFAS levels in plants across Africa.

Table 9 PFAS levels in plants across Africa
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2.2.7 Seafood Including Fishes

The intake of seafoods (including fish) exposes people to PFAS more frequently than other ways of exposure, however, information on the levels of PFAS in seafood and how much of the African population is exposed to it via the eating of seafood is scarce [59]. In South Africa, Thimo Groffen [36] detected PFAS at 289 ng/g in liver and muscle tissue 34 ng/g of fish. The authors determined whether eating PFAS-contaminated fish posed a risk to people. The acceptable daily intake levels (grams of fish that can be consumed every day without endangering health impacts) were less than the average daily fish consumption in South Africa, indicating potential threat to health of humans from eating of PFAS-contaminated fish in South Africa. Similarly, Ojemaye and Petrik [60], in their study reported that perfluorodecanoic acid, perfluorononanoic acid and perfluoroheptanoic acid were detected in the range of 20.13–179.2 ng/g, 21.22–114.0 ng/g and 40.06–138.3 ng/g in fish. The authors stated that estimated values from risk assessment exceeded 0.5 and 1.0 for acute and chronic risk, which revealed that PFAS in Kalk Bay harbor, South Africa poses serious threat to aquatic life and human health. In another study, the Σ11PFAS levels ranging from 0.12 to 6.43 ng/g were found in farmed shellfish in South Africa [59]. Furthermore, it was stated that the evaluated daily consumption for Σ10 PFAS through the intake of marine shellfish ranged between 0.05 and 1.58 ng/kg per day. In summary, the hazard quotients were low, suggesting that the South African population is not exposed to danger through eating of shellfish from the studied area. Nevertheless, regular monitoring should be carried out.

In Zambia, PFAS have been detected in fish at concentration of 0.66 ng/g. This is lower than the levels reported in South Africa [61]. Vaccher et al. [62] reported PFAS in fish samples in Benin and Mali at a concentration of 2.60 and 10.4 ng/g, respectively.

PFAS have been found in the range of 0.08–2.1 ng/g in fish samples in Ethiopia [47, 48]. However, it was stated that evaluation from relative risk revealed that the population of Ethiopia that eats fish is unlikely to suffer any negative effects from consuming fish contaminated with PFAS in Ethiopia [47, 48]. Arinaitwe et al. [63], reported ∑PFAS levels at concentration ranges of 0.24–1.75 ng/g in fish samples in Uganda. They reported that calculated human daily intake values of PFAS showed no danger to people who consume fish contaminated in Uganda. Barhoumi et al. [64], reported Ʃ21PFAS level in seafood samples range between 0.202 and 2.89 ng/g in Bizerte lagoon, Tunisia. The authors stated that the estimated daily intakes (EDIs) for detected PFAS were much lower than the tolerable daily intakes (TDIs), indicating that the consumption of fish contaminated with PFAS from Bizerte lagoon, Tunisia will not pose health risk to consumers. Table 10 presents the PFAS levels in seafood including fishes in Africa.

Table 10 Comparison of PFAS levels in seafood in Africa
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2.2.8 Indoor Dust

Shoeib et al. [65], reported PFAS in indoor dust samples at a range of levels 1.3–69 ng/g in Egypt. The dust samples were taken from chairs, roofs and dashboards from homes and cars in Cairo. They reported estimated exposure for toddlers and adults as 0.2 ng/day and 0.01 ng/day, respectively. This indicates that PFAS contamination in indoor dust is unlikely to cause health problem in Egypt. Furthermore, they reported that the total level of precursors PFAS (FTOHs + FOSA + FOSEs) in indoor dust in Egypt had a median of 6.92 ng/g. This is higher than the reported value of 0.83 ng/g in Spain [66], but lower than values of 370 ng/g and 989.2 ng/g in Birmingham, United Kingdom [67] and Australia [67] respectively.

2.2.9 Soil

Ibor et al. [68] reported PFAS in soil at levels ranging from 0.05 to 5.0 ng/g in Nigeria. The source of contamination is due to solid waste dumpsites (SWDs) within the affected area. This reveals that SWDs can contribute to the distribution of PFAS in soil, which could cause underground water pollution. Eze et al. [69] in their study reported PFAS at extreme concentration range of 2.6–275.3 ng/g in soil in Ghana. The authors stated that occurrence of PFAS at elevated level was due to electronic waste sites. This could cause danger to humans and microorganisms as well as bioaccumulation in plants within the area of occurrence. Dalahmeh et al. [46] detected PFAS in soil at levels ranging from 1.7 to 7.9 ng/g in Uganda.

2.3 Reported Methods for Sampling and Analysis of PFAS

The quantification of PFAS is faced with difficulties that can arise from sampling to analysis. This is due to the pervasive occurrence of PFAS which could cause interference associated with the type of sampling container and analytical techniques used. PFAS analytes may be contaminated or sorb onto sampling and storage containers made of fluoropolymer and glass materials [70]. The use of these materials should be avoided during sampling and analysis in order to reduce imprecise analysis. Polypropylene or polyethylene is considered as the most suitable material for sampling [71]. The detailed information on the different methods used for sampling and analysis of PFAS in various environmental matrix in Africa are presented in Table 11. The procedure for PFAS analysis involves sample collection and preparation prior to analysis. Sampling techniques depend on the type of environmental media. In Africa, Va Veen grab sampler, Ekman grab, pole dipper and composite sampling techniques have been used for collection of samples from sediments, drinking water, surface water and wastewater [11, 23, 26, 36, 41,42,43, 50]. Dust samples have been collected using vacuum cleaner bags [65].

Table 11 Different methods used for sampling and analysis of PFAS in various environmental matrix in Africa
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The primary purpose of sample preparation is to focus on target analytes, while removing matrix interferences simultaneously. Generally, a sample preparation procedure is necessary before an instrumental analysis. The extraction of PFAS from various environmental samples in Africa has been accomplished using a range of sample preparation techniques, including automated off-line solid phase extraction, solid phase extraction (SPE), solid-phase extraction-hydrophilic lipophilic balance (SPE-HLB) and solid–liquid extraction (SLE) [11, 25, 46, 48].

The way SPE method operates is that the analytes are either trapped in a solid sorbent or the other components of the sample are trapped and the analytes are allowed to elute from the solid phase. Conditioning the extraction phase is the initial stage in most SPE processes. Subsequently, this phase is equilibrated using a solvent that has characteristics with the solvent used to dilute the sample. At this stage, the analytes or matrix components that are interfering may be retained, depending on the characteristics of the extraction phase [72].

SLE is mainly applied to solid sample analysis. This method’s primary objective is to move the analytes from the solid matrix into a liquid phase where they can be used for chromatographic analysis. Three fundamental mechanisms govern the SLE process: the penetration of the extractant into the solid matrix, the diffusion of analytes into the surrounding space, and the solubility of analytes in the extractant. SLE is associated with low quantitative efficiency, prompting various measures to enhance its efficacy. Among these, the most notable strategies for quantitative improvement involve employing high temperature and pressure and harnessing auxiliary energies, notably microwaves and ultrasound [73].

2.4 National Implementation Role

Concerns about the global occurrence and distribution of PFAS as well as its adverse environmental and human health effects have been raised about three decades ago. This was due to reported evidence on the persistence and the abundant presence of PFAS in environmental and biological matrices [17]. In 2009 and 2019, perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorooctane sulfonyl fluoride (PFOSF) as well as their salts and related compounds were included in the annexes of the Stockholm Convention [39, 74].

Article 7 of the Stockholm Convention mandates that Parties to the Agreement create a strategy on how they will carry out their duties under the Agreement and endeavor to put that plan into action [75]. For this reason, the National Implementation Plan (NIP), which is part of the national sustainable development strategy was recommended as a control measure for persistent organic pollutants (POPs). Additionally, the NIP is a dynamic document because it must be routinely reviewed and amended to take into account any new Convention responsibilities [75]. The information on the NIP in Africa is scarce. In South Africa, regulation has been made on the prohibition of use, production, distribution, importation or exportation of PFOA and PFOS which took effect from December 2021 [76]. Likewise, the NIP of Kenya (2014) recommends determining the concentrations of PFAS in various environmental matrices [43]. However, Orata [77] reported that lack of awareness is a major challenge in Kenya in terms of its mandatory responsibility to the Stockholm Convention. This makes it difficult for stakeholders to identify these pollutants [17].

3 Conclusion and Recommendation for Future Studies

The absence of data on assessment of PFAS in most African countries limits our knowledge of the sources and distribution of PFAS and health risks in Africa. The lack of PFAS monitoring studies in these areas may be due to the lack of funding, trained personnel and accessibility of modern analytical facilities in many African countries. The ubiquity of PFAS in environmental media in Africa is aggravated by weak governance and illegal importation of goods containing PFAS from developed countries. Hence, the key players in Africa such as decision makers, academics and Non-Governmental Organizations should advocate for implementation of existing laws, develop laboratories with modern facilities and train scientists in Africa for better monitoring of PFAS and updating of the NIP. Additionally, it is imperative that environmental control agencies in Africa should keep track of products that contain PFAS and concentrations sourced from abroad into the continent.

African governments should think about using commercial research labs to conduct some of the analyses when developing these profiles because they are typically better suited than those in governmental institutions. Also, the mechanisms for data sharing need to be enhanced. For example, information should be easily accessed by trade organizations, the general public, and environmental advocacy groups in order to increase public awareness of the presence and impacts of PFAS in the environment. Such public involvement will raise awareness of environmental health issues and have an impact on environmental management procedures. As a result, it will aid in lowering exposure to PFASs and other contaminants in both humans and the environment.

The scarcity of the occurrence and distribution of PFAS in most African nations requires future research. It is recommended that further studies should focus on the following:

  • Toxicity and epidemiological related studies on PFAS in different African nations.

  • Sampling techniques in PFAS monitoring due to the risk associated with background contamination.

  • Research should be carried out on other PFAS and new generation PFAS to comprehend their occurrence and fate in the environment.