Health implications of heavy metal contamination in urban vegetables:  Assessing the risks in Kinshasa and Lubumbashi

doi:10.21203/rs.3.rs-4955506/v1

The contamination of edible vegetables with heavy metals is a significant global environmental and public health issue. These inorganic pollutants persist in the environment, accumulate in human tissues, and pose serious health risks. This study aimed to assess the levels of heavy metals such as aluminium (Al), arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), selenium (Se), and zinc (Zn) in leaves of Brassica oleracea, Hibiscus sabdariffa L., Amaranthus sp., and Ipomoea batatas leaves. The samples were collected from urban markets in Kinshasa and Lubumbashi, two major cities in the Democratic Republic of Congo. The microwave digestion system was used to extract metals from the samples, and the concentrations of heavy metals were measured using advanced spectroscopic techniques. The detected concentration ranges (in mg/kg dry weight) were as follows: Pb (0.23–1.76), Cd (0.31–1.73), As (1.16–7.19), Fe (22.69–94.22), Zn (17.75-375.01), Al (18.78–93.62), Cr (0.15–0.77), Cu (1.88–16.17), Mn (7.03-153.89), and Se (0.51–3.17). The health risk assessments revealed significant non-carcinogenic and carcinogenic risks to local populations, particularly from Pb and As exposure. These findings highlight the urgent need for regulatory measures to reduce heavy metal exposure from consuming vegetables in urban areas, aligning with global health and sustainability goals.

Heavy metal

potential health risks

vegetal

Kinshasa

Lumbumbashi

Heavy metal contamination in agricultural products is a significant global public health concern, especially in the fast-growing urban areas of developing countries (Atta et al., 2023). Urban expansion often leads to increased industrial activities and inadequate waste disposal practices, which raise the levels of heavy metals in agricultural soils(Lu et al., 2022). As cities expand, there is an increased need for locally grown food. This often leads to farming on land that has been contaminated by industrial waste in urban areas (Lemessa et al., 2022). In developing countries, this issue is exacerbated by weak environmental regulations, leading to the use of polluted water sources for irrigation, thereby increasing the heavy metal content in agricultural products (Gupta et al., 2022).

Due to their environmental persistence, heavy metals can pose significant risks to ecosystems and human health (Ahmed et al., 2022; Aransiola et al., 2024). They can accumulate in human tissues over time, leading to severe health outcomes such as cardiovascular, neurological, and renal diseases (Bist & Choudhary, 2022; Danouche et al., 2022; Mitra et al., 2022; Rahim et al., 2024). Humans and animals absorb heavy metals through contaminated food, water, and air (Faizan et al., 2024). Once ingested, they are bioaccumulated in vital organs and tissues, disrupting biological processes and causing various health issues (Abd Elnabi et al., 2023). Metals like lead (Pb), cadmium (Cd), and arsenic (As) are especially worrisome because of their significant toxicity and potential to cause cancer (Niu et al., 2018; Bist & Choudhary, 2022; Mitra et al., 2022). Pb, once widely used for its versatility, is now recognised as highly toxic, especially to children, where it can cause irreversible neurological damage and developmental delays (Faizan et al., 2024). Cd, commonly found in batteries and paints, can result in severe kidney failure and bone density loss with prolonged exposure (Abd Elnabi et al., 2023). As a natural element exacerbated by pesticide use and industrial activities, it is notorious for its potent carcinogenic properties, significantly increasing the risk of lung, skin, and bladder cancers (Ahmed et al., 2022; Parida & Patel, 2023). The widespread presence of these metals allows them to contaminate various agricultural products, from leafy greens to root vegetables, posing a systemic risk to public health (Gupta et al., 2022). It is crucial to take extensive measures to reduce their presence in the food chain (Rafique et al., 2022).

Vegetables are indispensable to human nutrition, offering essential nutrients like Fe for blood oxygenation, Ca for bone health, and proteins for tissue repair, along with vital vitamins that support numerous biochemical functions (Hassan et al., 2024; Amarloei et al., 2023). Vitamins C and E, antioxidant compounds present in vegetables, are essential for decreasing oxidative stress and improving immune function, thus reducing the likelihood of chronic conditions like cancer and cardiovascular diseases (Jolly et al., 2024; Tongprung et al., 2024; Ugulu et al., 2024). However, the soil that nourishes these vegetables can also harbour harmful heavy metals like Pb, Cr, Cd, and Cu, introduced through environmental contamination from industrial runoff, waste mismanagement, and unregulated mining activities (Amarloei et al., 2023; Ismael & Goran, 2024; Jolly et al., 2024). These inorganic pollutants can accumulate in vegetables, leading to contamination in humans and animals through consumption (Zhang et al., 2024). While vegetables are a vital component of a healthy diet, their potential as carriers of heavy metals presents complex challenges to public health and environmental conservation. It is crucial to have strict oversight of environmental and agricultural practices to guarantee the safety of our food (Rahim et al., 2024).

Urban agriculture is growing in sub-Saharan Africa, especially in cities such as Kinshasa and Lubumbashi in the Democratic Republic of the Congo (DR Congo). Kinshasa, the largest city and capital of the DR Congo, covers an area of 9,965 square kilometres and is estimated to be home to 13 million people (Nuapia et al., 2018). This urban growth has led to significant heavy metal contamination, driven by industrial emissions, vehicle exhaust, polluted irrigation water, and pesticide use (Ngweme et al., 2021). Lubumbashi, the second-largest city and the country's mining capital covers 747 km² with a population of 2.58 million (Tshibanda et al., 2024). As a hub for major mining companies, Lubumbashi contributes significantly to producing over 3 per cent of the world’s copper and half of its cobalt (Mata et al., 2020). However, the city's industrial activities have resulted in severe environmental pollution, including heavy metal pollution of soil, air and water (Langunu et al., 2024). These inorganic pollutants enter the food chain through vegetables grown in affected soils, posing severe health risks to the local population (Nuapia et al., 2018; Kayembe et al., 2018). The contamination of locally grown vegetables, a vital part of the local diet, underscores the broader implications of urban agriculture in similar global settings (Tuakuila et al., 2012). Recent studies highlight the need for thorough investigations into heavy metal pollution in urban agriculture, particularly in African cities where data on environmental pollutants is often lacking (Afonne & Ifediba, 2020; Agoro et al., 2020; Atitsogbey et al., 2023; Fonge et al., 2021a; Golia et al., 2021; Iyama et al., 2021; Naangmenyele et al., 2021; Oguntade et al., 2020; Oruko et al., 2021; Sayo et al., 2020; Tomno et al., 2020). The conditions in Kinshasa and Lubumbashi offer valuable perspectives on the environmental and public health difficulties associated with urban farming in fast-growing areas.

Our research aims to assess the levels of heavy metals, including Al, As, Cd, Cr, Cu, Fe, Mn, Pb, Se, and Zn, in vegetables sold in the urban markets of Kinshasa and Lubumbashi and evaluate their potential health risks. It offers comprehensive data illustrating the concentrations of heavy metals in the metropolitan areas of Congo. The study used health assessment models to evaluate the potential non-carcinogenic and carcinogenic impacts on public health. This information is anticipated to impact local and national regulations to minimise exposure to heavy metals. This effort is particularly significant for enhancing food safety standards and public health frameworks in the DR Congo and similar contexts.

Study area and sample collection

The study was conducted in Kinshasa and Lubumbashi, two big cities in the Democratic Republic of Congo (DRC). The samples were collected from 16 open markets in Kinshasa, including Cecomaf, Saïo, Zigida, Masina, Monastery, Kimwenza, Luzizila, Mukonzo, Wayawaya, Kalamu, Tchad, N’sele, Livulu, Kisenso, Mayimbi, and Masangambila. In Lubumbashi, samples were collected from nine open markets, including Zambia, Rail, Mzee, Kenya Central, Kenya Njanja, Katina, Payage, Golf, and Double Poto.

Sample preparation

Leaves from vegetables, including Brassica oleracea, Hibiscus sabdariffa L, Amaranthus sp., and Ipomoea batatas leaves, were collected from urban markets in Kinshasa and Lubumbashi. Samples were obtained from five vendors, each weighing approximately 1 kg. These were combined into a single composite sample. In the laboratory, the samples underwent an initial washing with tap water, followed by a rinse with distilled water to eliminate dust and debris. The cleaned vegetables were cut into small pieces and air-dried for five days. Once dried, the samples were ground into a powder using a clean laboratory mortar and pestle. The powdered samples were then sealed in zip-lock plastic bags and shipped to the Molecular Sciences Institute at the School of Chemistry, University of Witwatersrand, South Africa, for further analysis.

Sample analysis

The analytical method employed was based on the protocol outlined by Nuapia et al. (2018), with a specific modification regarding the mass of the samples. The dried samples were homogenised and precisely weighed to 0.10 ± 0.005 g using an analytical balance (Precisa 180A, Switzerland). These samples were then transferred into acid-washed digestion tubes fitted with PTFE-TFM liners for processing in a Multiwave 3000 microwave digester (Anton Paar, Switzerland). The metal content of the vegetable samples was analysed using two methods: ICP-OES (Spectro, Kleve, Germany) for measuring As, Fe, Zn, Al, Cr, Cu, and Mn and ICP-MS (Agilent Technologies, 7700 series, Johannesburg, South Africa) for detecting Pb, Cd, and Se. The results were reported in milligrams per kilogram (mg/kg) per dry weight (DW).

Estimated daily intake (EDI).

The daily intake of metals (EDI) was calculated using the average concentration of heavy metals measured in the vegetable samples, expressed in grams per kg. The formula for calculating the EDI for each metal was adapted from the equation described by Afonne & Ifediba (2020) and Fonge et al. (2021b) and is represented as :

EDI = \(\:\frac{CxFIR}{WAB}\) (1)

In this context, C (mg/kg FW) represents the average heavy metal content in the edible portion of the vegetable. FIR (g/day per person) refers to the daily vegetable consumption. According to Nuapia et al. (2018) and Langunu et al. (2024), the average FIR for all residents and adults in Kinshasa is 67 g/day per person, while Lubumbashi is 23.5 g/day per person. WAB represents the average adult body weight of 57.8 kg (Tuakuila et al., 2012).

Target hazard quotient (THQ).

To assess the non-carcinogenic health risks from consuming these contaminated vegetables, we computed the target hazard quotient (THQ) using Eq. (2) (Naangmenyele et al., 2021; Oruko et al., 2021):

THQ = \(\:\frac{EDI}{RfD}\) Eq. (2)

EDI represents the estimated daily intake of metals in mg/day/kg body weight (Chinnannan et al., 2024; Malczyk et al., 2024). Rfd is the oral reference dose (mg/kg/day) for each metal, with specified values for metals such as Al, As, Cd, Cr, Cu, Fe, Mn, Pb, Se, and Zn (Oruko Ongon’g et al., 2020a; Edogbo et al., 2020; Zhang et al., 2022; Ismael & Goran, 2024; Tongprung et al., 2024). A THQ value of less than 1 is typically considered safe, whereas values exceeding 1 suggest an increased likelihood of non-carcinogenic risks as the value increases.

Hazard Index

The cumulative risk of multiple metal exposures is expressed through the hazard index (HI), calculated using Eq. (3) (Amarloei et al., 2023; Ismael & Goran, 2024; Tongprung et al., 2024):

HI = Σ THQ = THQ Al + THQ As + THQ Cd + THQ Cr + THQ Cu + THQ Fe + THQ Mn + THQ Pb + THQ Se + THQ Zn. Eq. (3)

An HI value below 1.0 indicates no apparent health impacts, but values above 1.0 suggest potential health risks, with values over 10.0 indicating severe chronic health impacts (Amarloei et al., 2023; Ismael & Goran, 2024).

The target cancer risk (TCR)

To evaluate the cancer risk (CR) from ingestion of carcinogenic metals, we used the equation describe by Jolly et al.(ya 2024):

AELCR =\(\:\frac{Exposure\:rate\:x\:SF}{DL\:X\:365}\) Eq. (4)

AELCR = annual excess lifetime cancer risk.

SF = cancer slope factor (mg/kg, day).

DL = average human longevity.

The annual excess lifetime cancer risk (AELCR) is represented by AELCR, where SF is the cancer slope factor. DL is the average human longevity in the Democratic Republic of Congo, which is 60.7 years (Tuakuila et al., 2012). The SF values for As, Pb, Cd, and Cr are based on established toxicity levels (Langunu et al., 2024). Regulatory acceptable risk levels range from 10^− 6 to 10^− 4 (Jolly et al., 2024).

Metal pollution index

the overall concentration of heavy metals in vegetables was evaluated using the Metal Pollution Index (MPI), calculated by taking the geometric mean of the concentrations of all metals in the edible parts of the vegetables (Afonne & Ifediba, 2020):

MPI (mg/kg) = (C1 × C2 · · ·×C_n)^1/n Eq. (5)

Where C_n = concentration of metal n in the sample.

Statistical analysis.

Metal concentrations were analysed using descriptive statistical approaches to determine the mean, standard deviation, minimum, and maximum values. One-way ANOVA and post-hoc tests, including Tukey HSD, were conducted to identify significant differences in metal distribution among different sampling sites at a significance level of p < 0.05 (Nguyen et al., 2020). Furthermore, a t-test was used to compare contamination levels in two cities. All analyses were performed using the R software package, including Pearson correlation, to investigate relationships among variables.

Heavy metal levels in the vegetables are presented in Table 1, showing significant variations between samples from Kinshasa and Lubumbashi, two major cities in the Democratic Republic of the Congo. The Pearson correlation matrix (Table S1) indicates the correlation coefficients between the analysed elements. A correlation coefficient higher than 0.99 was observed only between Al-Fe and Pb-Zn in Kinshasa and Al-Fe and Pb-Se in Lubumbashi, indicating a linear solid association at the 0.01 significance level. This suggests a common origin of these metals, possibly through sources like crustal contamination. Some other elements showed a positive correlation at the 0.05 significance level. In Kinshasa, Al is correlated with Cr, Mn, Pb, Se, and Zn; Cd is correlated with Se; Cr is correlated with Fe; it is correlated with Mn, Pb, Se, and Zn; and Mn is correlated with Se. In Lubumbashi, Al is correlated with Cr; Cr is correlated with Fe; and Cd is correlated with Cu and Zn. This demonstrates that the metals showing positive mutual associations interact, indicating a common source of pollution.

The levels of Al in the vegetable samples from Kinshasa and Lubumbashi are notably high, particularly in Lubumbashi. For instance, in Lubumbashi, Ipomoea batatas leaves contain as much as 93.62 mg/kg of aluminium, compared to 56.23 mg/kg in the same vegetable from Kinshasa. While aluminium is not typically associated with acute toxicity in humans, its elevated levels can indicate broader environmental contamination. The high aluminium content in Lubumbashi's vegetables likely reflects the pervasive influence of mining activities, which can introduce large amounts of aluminium into the soil. Although not as immediately harmful as some other metals, chronic exposure to high levels of aluminium may contribute to neurological conditions, including Alzheimer’s disease, and can impair bone mineralisation (Malamba-Lez et al., 2021).

The presence of As in vegetable samples is a grave concern due to its well-documented toxicity and carcinogenic properties (Mitra et al., 2022). In Lubumbashi, levels in Amaranthus sp. reach 7.64 mg/kg, and in Ipomoea batatas leaves, they reach 7.19 mg/kg. These levels far exceed the WHO/FAO guideline of 1.00 mg/kg (WHO/FAO, 2000), indicating a significant public health risk. Exposure to As is associated with a wide range of severe health issues, including skin lesions, cardiovascular disease, neurotoxicity, and various forms of cancer, such as lung, bladder, and skin cancer (Rafique et al., 2022). The high levels of As in Lubumbashi’s vegetables suggest that the local population could be at considerable risk, particularly with long-term consumption (Mata et al., 2020). Kinshasa's lower yet still concerning levels (ranging from 1.16 to 1.44 mg/kg) also pose a less severe risk than Lubumbashi. Cd in vegetable samples is a significant concern due to its high toxicity, even at low concentrations. In Lubumbashi, cadmium levels in vegetables like Amaranthus sp. (1.79 mg/kg) and Ipomoea batatas leaves (1.73 mg/kg) vastly exceed the WHO/FAO recommended 0.2 mg/kg limit. This presents a serious health risk, as cadmium is known to cause kidney damage, skeletal weakening, and respiratory problems. Prolonged exposure to cadmium, particularly at these elevated levels, can lead to chronic health conditions such as renal failure and osteoporosis. Although cadmium levels are lower (0.31 to 0.70 mg/kg) in Kinshasa, they still surpass safe limits, indicating a need for immediate concern and action in both cities.

The Concentrations of Cr in both cities are relatively low compared to other metals, yet the levels in Lubumbashi are still higher, ranging up to 0.77 mg/kg in Brassica oleracea. Chromium has several forms, with hexavalent chromium being highly toxic and carcinogenic (Genthe et al., 2018). While the specific form of chromium was not detailed in the data, its presence in elevated levels could suggest potential health risks, mainly if the toxic form is prevalent. Although the levels found do not exceed WHO/FAO limits, the consistent difference between the cities indicates ongoing environmental exposure that warrants monitoring. Copper (Cu) is an essential trace element necessary for various physiological processes, but at high concentrations, it can become toxic (Mitra et al., 2022). In Lubumbashi, copper levels in Amaranthus sp. reach 16.17 mg/kg, significantly higher than in Kinshasa (with a maximum of 3.93 mg/kg in Amaranthus sp.). While these levels do not exceed international safety guidelines, the elevated copper content in Lubumbashi’s vegetables suggests potential contamination from industrial sources. Chronic exposure to high levels of copper can lead to liver and kidney damage, and excessive intake can also cause gastrointestinal distress. Iron (Fe) is another essential nutrient for oxygen transport and energy metabolism (Mata et al., 2020). However, the levels of Fe in Lubumbashi’s vegetables, particularly in Ipomoea batatas leaves (94.22 mg/kg), are markedly high compared to those in Kinshasa (with a maximum of 65.76 mg/kg in Ipomoea batatas leaves). While these levels are within acceptable limits, they reflect the extent of environmental contamination in Lubumbashi. Excessive iron intake, especially from contaminated food sources, can lead to conditions like hemochromatosis, which causes iron overload and subsequent damage to organs such as the liver and heart (Malamba-Lez et al., 2021).

Manganese (Mn) levels are exceptionally high in Lubumbashi, particularly in Amaranthus sp., where concentrations reach 153.89 mg/kg. This starkly contrasts with Kinshasa, where the highest manganese concentration is 19.47 mg/kg in Ipomoea batatas leaves. While manganese is essential for bone formation and metabolic processes, excessive exposure, especially at the levels found in Lubumbashi, can lead to neurological issues similar to Parkinson’s disease. The significant disparity between the two cities suggests that manganese contamination in Lubumbashi directly results from the city’s intensive mining activities.

Lead (Pb) is one of the most dangerous metals identified in the samples, with levels in Lubumbashi reaching 5.52 mg/kg in Ipomoea batatas leaves—far exceeding the WHO/FAO limit of 0.3 mg/kg. Lead is a potent neurotoxin, and its effects are particularly severe in children, leading to developmental delays, cognitive deficits, and behavioural problems. The high lead levels found in Lubumbashi’s vegetables indicate a severe public health hazard. Even in Kinshasa, where the lead levels are lower (0.23 to 1.76 mg/kg), the presence of this metal at these concentrations is concerning and highlights the need for urgent intervention.

Selenium (Se) is essential in small amounts, but its elevated levels in Lubumbashi’s vegetables (up to 3.17 mg/kg in Ipomoea batatas leaves) could pose health risks. Excess selenium intake can lead to toxicity, causing symptoms such as gastrointestinal distress, hair loss, and neurological damage. In Kinshasa, selenium levels are lower (0.51 to 1.01 mg/kg), which is within safer limits. However, the significant difference in selenium concentrations between the two cities suggests varying environmental factors, likely linked to industrial emissions in Lubumbashi.

Zinc (Zn) is another essential metal that, in excess, can cause adverse health effects. The concentrations of Zn in Lubumbashi’s vegetables are extremely high, with Amaranthus sp. containing up to 375.01 mg/kg. In comparison, the highest zinc concentration in Kinshasa is 77.97 mg/kg in Ipomoea batatas leaves. Although zinc is necessary for immune function and enzyme activity, such high levels can lead to toxicity, causing symptoms like nausea, vomiting, and impaired immune response (Rafique et al., 2022). The data suggests that zinc contamination is a significant issue in Lubumbashi, likely due to the extensive industrial activities in the region.

The analysis of heavy metal concentrations in vegetables from Kinshasa and Lubumbashi reveals a clear pattern of higher contamination in Lubumbashi, driven by its extensive mining activities. While some metals like iron and zinc are essential nutrients, their excessive presence poses significant health risks (Mitra et al., 2022). Metals like lead, cadmium, and arsenic, in particular, present serious public health concerns due to their high toxicity and the severe health effects associated with long-term exposure. The data underscores the urgent need for stricter environmental regulations, continuous monitoring, and public health interventions to address and mitigate the risks associated with heavy metal contamination in these urban centers.

Tables 1: Trace element levels (mean ± SD in mg kg^− 1 ) in vegetables from Markets in Kinshasa and Lubumbashi

Kinshasa
Samples	Al	As	Cd	Cr	Cu	Fe	Mn	Pb	Se	Zn
Brassica oleracea	18.78 ± 2.39	1.16 ± 0.73	0.31 ± 0.05	0.15 ± 0.08	1.88 ± 0.26	22.69 ± 2.16	7.03 ± 0.82	0.23 ± 0.02	0.51 ± 0.06	17.75 ± 1.95
Hibiscus sabdariffa L	32.04 ± 5.50	1.311 ± 0.56	0.36 ± 0.07	0.20 ± 0.08	1.79 ± 0.23	34.14 ± 4.71	6.51 ± 0.84	0.74 ± 0.15	0.55 ± 0.05	36.88 ± 6.29
Amaranthus sp	37.66 ± 4.46	1.44 ± 0.69	0.55 ± 0.05	0.21 ± 0.01	3.932 ± 0.37	36.18 ± 3.32	10.24 ± 1.05	0.57 ± 0.08	0.714 ± 0.08	26.71 ± 3.03
Ipomoea batatas leaves	56.23 ± 8.78	1.37 ± 0.09	0.70 ± 0.08	0.25 ± 0.017	3.87 ± 0.34	65.76 ± 7.67	19.47 ± 2.07	1.76 ± 0.04	1.01 ± 0.13	77.97 ± 10.65
Lubumbashi
Brassica oleracea	42.34 ± 7.89	5.80 ± 1.90	1.41 ± 0.17	0.77 ± 0.05	11.79 ± 0.78	47.67 ± 8.05	74.29 ± 10.05	0.71 ± 0.08	1.57 ± 0.27	239.64 ± 5.33
Hibiscus sabdariffa L	56.51 ± 2.86	6.56 ± 1.71	0.87 ± 0.05	0.56 ± 0.11	7.36 ± 0.81	83.49 ± 2.70	38.60 ± 4.51	1.36 ± 0.24	1.63 ± 0.78	97.02 ± 14.76
Amaranthus sp	81.03 ± 4.28	7.64 ± 3.56	1.79 ± 0.84	0.73 ± 0.37	16.17 ± 1.16	71.31 ± 4.54	153.89 ± 11.85	4.22 ± 0.57	2.44 ± 1.33	375.01 ± 31.92
Ipomoea batatas leaves	93.62 ± 5.95	7.19 ± 2.84	1.73 ± 0.38	0.70 ± 0.29	16.04 ± 1.77	94.22 ± 5.70	76.07 ± 6.68	5.52 ± 0.78	3.17 ± 0.55	274.76 ± 35.84
OMS/FAO 2007; 2011			0.2	1.3	73	425	500	0.3		99.4
FAO/WHO (2000)	12–71	1.00

Significant variations in heavy metal accumulation in Brassica oleracea are observed in different regions, reflecting the influence of local environmental factors and farming methods. For instance, in Lubumbashi, high levels of Pb and Cd in Brassica oleracea have been attributed to extensive mining activities. Similar findings in Jigawa State, Nigeria, also indicated significant health risks due to elevated levels of these metals (Sagagi et al., 2022). Conversely, studies in Durban and Barberton, South Africa, found that while Brassica oleracea did accumulate metals like iron (Fe) and lead, these were generally within permissible limits, suggesting lower health risks in these areas (Shabalala et al., 2022). In Kinshasa, heavy metal contamination was linked to urbanisation and industrial emissions, with levels comparable to those seen in wastewater irrigation regions, significantly increasing plant metal uptake (Shah et al., 2023). Despite these risks, Brassica oleracea in Kinshasa poses a relatively lower health risk than other vegetables, such as spinach, which accumulate higher levels of heavy metals.

Overall, samples from Lubumbashi consistently showed higher concentrations of heavy metals in all vegetables compared to Kinshasa, likely due to the city's intensive mining activities. The elevated levels of As, Cd, and Pb in Lubumbashi far exceed international safety standards, posing significant health risks, including cancer, neurological damage, and other severe health issues (Genthe et al., 2018). These findings highlight the need for region-specific monitoring and management of heavy metal pollution in agriculture to mitigate health risks effectively.

In the analysis conducted by Arslaner et al., (2021), Hibiscus sabdariffa L. accumulated significant concentrations of heavy metals, including manganese (Mn) at 308 mg/kg, Fe at 368 mg/kg, and Cu at 1.01 mg/kg. The study highlighted that Cr and As levels were particularly concerning, with Cr at 31.9 mg/kg and As ranging from 13.4 to 32.1 mg/kg, exceeding WHO permissible limits. Cd and Pb were also present at high levels, with Cd reaching up to 31.4 mg/kg and Pb up to 39.0 mg/kg, indicating potential health risks from consuming Hibiscus sabdariffa grown in contaminated soils. Similarly, in a comparative analysis of urban areas like Kinshasa and Lubumbashi, vegetables grown in heavily contaminated soils showed elevated levels of these metals, reinforcing concerns about health risks from such environments.

Njoku & Nwani, (2022) have explored the phytoremediation potential of Amaranthus spinosus. They reported that the plant accumulated significant levels of heavy metals, including 6.71 mg/kg of Cu, 38.1 mg/kg of Zn, 19.6 mg/kg of Pb, and 2.1 mg/kg of Cd when grown in contaminated soils. The study emphasised the high bioconcentration factor (BCF) for Zn and Cu, demonstrating Amaranthus spinosus's effectiveness in phytoremediation. The high Pb and Cd levels could pose health risks if the plant is consumed.

In another study by Tőzsér et al., (2023), Amaranthus species were found to accumulate considerable amounts of heavy metals, particularly Cd, with bioaccumulation factor (BAF) values indicating a substantial accumulation in the leaves. Pb and Zn also accumulated significantly, especially in the roots and leaves, while Fe, Ni, and Cu showed moderate accumulation levels across the plant parts. The study suggested that while Amaranthus species have strong potential for phytoremediation, the accumulation of heavy metals in edible parts like leaves could pose health risks if consumed without proper monitoring. Ramanlal et al. (2020) further supported these findings by showing that Amaranthus species effectively accumulated Zn and Cr when grown in soils contaminated with paint industry effluent. The study reported concentrations of 27.08 mg/kg Zn and 17.84 mg/kg Cr in the roots under 100% effluent treatment, with even higher concentrations in the shoots. Pb and Cu were also accumulated, with Pb reaching 28.47 mg/kg in roots and 18.13 mg/kg in shoots, indicating the plant's substantial potential for phytoremediation. However, accumulating such metals in edible parts raises health concerns.

Finally, Huang et al. (2020) examined Ipomoea batatas leaves. They found that they accumulated Cd and Pb at levels that exceeded Chinese National Food Safety Standards, with Cd concentrations ranging from 0.49 to 2.19 mg/kg and Pb from 0.65 to 1.92 mg/kg. These findings underscore the significant health risks posed by consuming Ipomoea batatas leaves from contaminated soils, particularly in areas with high levels of soil contamination by these metals. The consistent findings across these studies highlight the risks associated with consuming plants grown in contaminated environments, stressing the need for careful management and monitoring of agricultural practices in such areas.

Metal Pollution index

Figure 1 illustrates the Metal Pollution Index (MPI) of different vegetables from Kinshasa and Lubumbashi. In Kinshasa (A), Amaranthus sp. exhibits the highest MPI at 26.382, indicating substantial metal contamination, followed by Ipomoea batatas leaves and Brassica oleracea with MPI values of 17.193 and 17.459, respectively. Hibiscus sabdariffa L. shows the lowest MPI at 9.59, suggesting relatively lower contamination than the other vegetables. In Lubumbashi (B), the pattern of metal contamination is similar, with Amaranthus sp. again displaying the highest MPI, emphasising its significant role as a metal accumulator. These results underscore the need for targeted interventions to reduce heavy metal exposure from these commonly consumed vegetables in both cities. The MPI values emphasise the need for careful monitoring and management of these vegetables to ensure they are safe for consumption (Golia et al., 2021).

Potential Health Risks

Estimated Daily and weekly intake

The estimation of the daily intake of vegetables, as presented in Table 2, provides a comprehensive overview of the potential exposure to various toxic metals for the populations of Kinshasa and Lubumbashi. This analysis highlights significant disparities in the levels of heavy metal contamination across different vegetables, reflecting the distinct environmental conditions in each city.

Brassica oleracea samples from Kinshasa and Lubumbashi exhibit notable differences in heavy metal contamination. In Kinshasa, Brassica oleracea shows relatively low levels of Al, with an Estimated Daily Intake (EDI) of 21.77 mg/kg and an Estimated Weekly Intake (EWI) of 152.39 mg/kg, staying within acceptable limits. However, in Lubumbashi, Al levels are significantly higher, with an EDI of 172.25 mg/kg and an EWI of 1205.77 mg/kg, indicating substantial contamination likely linked to industrial activities. The concentration of As in Brassica oleracea is less of a concern in Kinshasa, with levels below the safety threshold. However, in Lubumbashi, As contamination is higher, although still within safer limits.

Table 2

Estimated Daily Intake (EDI) (mg.day^− 1.person^− 1)
Kinshasa
METAL	Brassica oleracea		Hibiscus sabdariffa L		Amaranthus sp		Ipomoea batatas leaves		Guidelines (FAO/WHO,2000)
	EDIT	EWI	EDIT	EWI	EDIT	EWI	EDIT	EWI	EDIT	EWI
Al	21.77	152.39	37.14	259.99	42.71	298.99	88.36	618.52	120^b	840
As	1.34	9.387	1.52	10.64	1.61	11.26	1.55	10.87	2.14^a	14.98
Cd	0.39	2.75	0.43	2.912	0.63	4.42	0.81	5.67	1^a	7
Cr	0.18	1.24	0.23	1.64	0.25	1.72	0.29	1.99	0.039^b	0.273
Cu	2.18	15.25	2.08	14.53	4.56	31.91	4.48	31.39	700^a	4900
Fe	26.34	18.44	39.57	277.03	41.94	293.58	76.23	533.64	45^b	315
Mn	8.15	57.02	7.55	52.82	11.87	83.06	22.57	158.01	11^b	77
Pb	0.27	1.86	0.85	5.98	0.66	4.60	2.04	14.25	3.6^a	25.2
Se	0.59	4.12	0.64	4.49	0.83	5.79	1.17	8.15	0.055^b	0.385
Zn	20.58	144.05	42.76	299.29	33.28	232.99	90.38	632.63	1000^a	7000
Lubumbashi
Al	172.25	1205.77	63.64	445.47	187.46	1312.19	160.05	1120.33	120^b	840
As	2.36	16.52	2.67	18.67	3.11	21.74	2.93	20.4	2.14^a	14.98
Cd	0.57	4.01	0.36	2.48	0.73	5.08	0.70	4.91	1a	7
Cr	0.31	2.18	0.23	1.58	0.29	2.07	0.29	1.99	0.039^b	0.273
Cu	4.49	31.46	2.99	20.94	6.57	46.02	6.52	45.67	700^a	4900
Fe	193.69	1355.84	74.61	522.25	208.63	1460.41	179.60	1257.22	45^b	315
Mn	30.21	211.44	15.69	109.87	62.57	438.01	30.93	216.49	11^b	77
Pb	0.29	2.01	0.55	3.88	1.72	12.00	2.24	15.69	3.6^a	25.2
Se	0.64	4.46	0.66	4.65	0.99	6.93	1.29	9.03	0.055^b	0.385
Zn	97.44	682.06	39.45	276.14	152.48	1067.36	111.72	782.02	1000^a	7000

The levels of Cd are low in Kinshasa (EDI of 0.39 mg/kg and EWI of 2.75 mg/kg). Lubumbashi’s Brassica oleracea shows slightly higher Cd levels (EDI of 0.57 mg/kg and EWI of 4.01 mg/kg), still below the critical threshold but warranting attention. The level of Pb is minimal in Kinshasa’s Brassica oleracea, with an EDI of 0.27 mg/kg and an EWI of 1.86 mg/kg. In Lubumbashi, Pb levels are slightly elevated, with an EDI of 0.29 mg/kg and an EWI of 2.01 mg/kg, reflecting increased exposure risks. The concentration of Fe is moderate in Kinshasa (EDI of 26.34 mg/kg and EWI of 184.44 mg/kg) but is substantially higher in Lubumbashi (EDI of 193.69 mg/kg and EWI of 1355.84 mg/kg), indicating significant environmental contamination. The levels of Mn are relatively low in Kinshasa (EDI of 8.15 mg/kg and EWI of 57.02 mg/kg) but are much higher in Lubumbashi (EDI of 30.21 mg/kg and EWI of 211.44 mg/kg), suggesting more significant exposure risks. The amount of Se in Brassica oleracea is below concern levels in both cities, with slightly higher levels in Lubumbashi. The concentration of Zn in Brassica oleracea is higher in Lubumbashi (EDI of 97.44 mg/kg and EWI of 682.06 mg/kg) compared to Kinshasa (EDI of 20.58 mg/kg and EWI of 144.05 mg/kg), reflecting the broader environmental challenges in Lubumbashi.

Hibiscus sabdariffa L. shows varying levels of contamination between the two cities. In Kinshasa, Al levels are moderate, with an EDI of 37.14 mg/kg and an EWI of 259.99 mg/kg. In Lubumbashi, however, Al contamination is significantly higher, with an EDI of 63.64 mg/kg and an EWI of 445.47 mg/kg, indicating substantial industrial pollution. The amounts of As are concerning in Lubumbashi, with an EDI of 2.67 mg/kg and an EWI of 18.67 mg/kg, exceeding recommended safety limits. In contrast, Kinshasa’s Hibiscus sabdariffa L shows safer As levels (EDI of 1.52 mg/kg and EWI of 10.64 mg/kg). Both cities have Cd levels in Hibiscus sabdariffa L below critical thresholds, although slightly higher in Lubumbashi. The concentration of Pb in Hibiscus sabdariffa L is minimal in Kinshasa (EDI of 0.85 mg/kg and EWI of 5.98 mg/kg). Still, Lubumbashi shows higher Pb levels (EDI of 0.55 mg/kg and EWI of 3.88 mg/kg), reflecting greater environmental exposure. The levels of Fe are moderate in Kinshasa but substantially higher in Lubumbashi, similar to other metals. The amounts of Mn are relatively low in Kinshasa (EDI of 7.55 mg/kg and EWI of 52.82 mg/kg) but significantly elevated in Lubumbashi (EDI of 15.69 mg/kg and EWI of 109.87 mg/kg). The levels of Se are slightly elevated in both cities, with higher concentrations in Lubumbashi. Zinc (Zn) contamination is higher in Lubumbashi’s Hibiscus sabdariffa L (EDI of 39.45 mg/kg and EWI of 276.14 mg/kg) compared to Kinshasa (EDI of 42.76 mg/kg and EWI of 299.29 mg/kg), indicating widespread environmental challenges.

Amaranthus sp. is one of the most contaminated vegetables in both cities, with significantly higher levels in Lubumbashi. In Kinshasa, Al levels in Amaranthus sp are elevated, with an EDI of 42.71 mg/kg and an EWI of 298.99 mg/kg. However, in Lubumbashi, Al contamination is extreme, with an EDI of 187.46 mg/kg and an EWI of 1312.19 mg/kg, reflecting severe environmental degradation. The As levels in Amaranthus sp are moderately high in Kinshasa but reach critical levels in Lubumbashi (EDI of 3.11 mg/kg and EWI of 21.74 mg/kg), posing severe health risks (). The Cd levels in Kinshasa are near safety thresholds (EDI of 0.63 mg/kg and EWI of 4.42 mg/kg). In comparison, Lubumbashi shows even higher levels (EDI of 0.73 mg/kg and EWI of 5.08 mg/kg), increasing the risk of chronic health conditions (). The Pb levels in Amaranthus sp are concerning in both cities. Kinshasa’s Amaranthus sp has an EDI of 0.66 mg/kg and an EWI of 4.60 mg/kg. At the same time, Lubumbashi’s levels are significantly higher, with an EDI of 1.72 mg/kg and an EWI of 12.00 mg/kg, indicating substantial exposure risks (). The concentration of Fe is also severe in Lubumbashi (EDI of 208.63 mg/kg and EWI of 1460.41 mg/kg), compared to Kinshasa (EDI of 41.94 mg/kg and EWI of 293.58 mg/kg). The Mn levels are high in both cities but particularly elevated in Lubumbashi (EDI of 62.57 mg/kg and EWI of 438.01 mg/kg), reflecting significant environmental exposure. The Se and Zn levels are also much higher in Lubumbashi, indicating widespread ecological contamination.

Ipomoea batatas leaves show the highest contamination levels in both cities, particularly in Lubumbashi. In Kinshasa, Ipomoea batatas leaves exhibit significant Al levels, with an EDI of 88.36 mg/kg and an EWI of 618.52 mg/kg. However, in Lubumbashi, Al levels are dramatically higher, with an EDI of 160.05 mg/kg and an EWI of 1120.33 mg/kg, indicating severe environmental pollution. The As levels in Ipomoea batatas leaves are higher in Lubumbashi (EDI of 2.93 mg/kg and EWI of 20.49 mg/kg) compared to Kinshasa (EDI of 1.55 mg/kg and EWI of 10.87 mg/kg), posing severe health risks (). The Cd levels are also concerning, with Kinshasa showing an EDI of 0.81 mg/kg, an EWI of 5.67 mg/kg, and Lubumbashi showing slightly lower levels but still above safety thresholds. The presence of Pb in Ipomoea batatas leaves is particularly alarming in both cities. Kinshasa’s leaves have an EDI of 2.04 mg/kg and an EWI of 14.25 mg/kg, while Lubumbashi’s leaves reach an EDI of 2.24 mg/kg and an EWI of 15.69 mg/kg, underscoring the neurotoxic severe risks posed by Pb (). The Fe levels are also extremely high in Lubumbashi (EDI of 179.60 mg/kg and EWI of 1257.22 mg/kg), compared to Kinshasa (EDI of 76.23 mg/kg and EWI of 533.64 mg/kg). The Mn levels in Ipomoea batatas leaves are significantly higher in Lubumbashi (EDI of 30.93 mg/kg and EWI of 216.49 mg/kg) compared to Kinshasa (EDI of 22.57 mg/kg and EWI of 158.01 mg/kg). The Se and Zn levels are elevated in both cities, with Lubumbashi showing much higher concentrations, reflecting the broader environmental challenges in the region.

Overall, this detailed comparison of heavy metal contamination in vegetables from Kinshasa and Lubumbashi highlights significant differences in the levels of toxic metals, with Lubumbashi consistently showing higher contamination across all vegetables analysed. This disparity is likely due to the city’s extensive industrial and mining activities, which contribute to widespread environmental pollution. The elevated levels of multiple toxic metals, particularly in vegetables like Amaranthus sp. and Ipomoea batatas, underscore the urgent need for immediate and comprehensive interventions. Implementing stringent environmental regulations, conducting targeted public health campaigns, improving agricultural practices, and ensuring continuous monitoring are essential to mitigate the health risks of heavy metal exposure in these urban centres. Addressing these issues is crucial to protecting the health of the populations in Kinshasa and Lubumbashi and ensuring a sustainable and safe food supply.

Target hazard quotient

Figure 2 illustrates the Target Hazard Quotient (THQ) for various heavy metals in different vegetables from A) Kinshasa and B) Lubumbashi. This offers valuable information on the possible health risks of consuming these vegetables regularly. The THQ is a risk assessment metric that estimates the likelihood of adverse health effects from long-term exposure to chemical pollutants, with a THQ greater than 1 indicating a potential health risk.

The heavy metal such as Pb demonstrates the highest THQ across all vegetables in both Kinshasa and Lubumbashi, significantly surpassing the safe threshold of one, which raises serious concerns for potential adverse health effects (Afonne & Ifediba, 2020). The elevated THQ values for Pb are particularly alarming in Ipomoea batatas (sweet potato leaves), Amaranthus sp. (amaranth), and Brassica oleracea (cabbage), where the risk is most pronounced. The extremely high THQ values indicate a grave risk of Pb toxicity, which could lead to severe health consequences, especially in children, including cognitive impairment and developmental delays (Alfaro et al., 2022; Gupta et al., 2022). The higher Pb levels in Lubumbashi may be attributed to the city’s extensive mining and industrial activities, which contribute to environmental contamination. Fe also presents a notable risk, with THQ values that, while generally below the threshold of one, are still elevated, particularly in Ipomoea batatas and Amaranthus sp. Fe is an essential nutrient, but excessive intake can lead to conditions such as hemochromatosis, which causes damage to organs like the liver and heart due to Fe overload (Abd Elnabi et al., 2023; Ahmed et al., 2022; Rafique et al., 2022). The higher THQ values in Lubumbashi suggest a greater risk of Fe-related health issues in this region than in Kinshasa. Al shows elevated THQ values across all vegetables, with Ipomoea batatas and Amaranthus sp. presenting the highest values again. Although the THQ for Al remains below 1, it is still concerning due to the potential for cumulative effects over time, particularly as Al has been associated with neurotoxicity and an increased risk of neurological disorders such as Alzheimer's disease (Amarloei et al., 2023; Tongprung et al., 2024). As is another metal of concern, with elevated THQ values observed in Hibiscus sabdariffa L. (roselle), Amaranthus sp., and Ipomoea batatas. In Lubumbashi, the THQ for As approaches or exceeds the threshold of one, indicating a potential risk of chronic As exposure associated with various cancers and cardiovascular diseases (Hassan et al., 2024). The elevated As levels in these vegetables could pose a significant health risk (Zhang et al., 2024), particularly in populations that consume them regularly. Cd exhibits moderately elevated THQ values, particularly in Amaranthus sp. and Ipomoea batatas, with values approaching the threshold of one. Cd exposure is linked to kidney damage and bone demineralization, and chronic exposure can lead to severe health conditions such as osteoporosis and renal failure (Mitra et al., 2022). The THQ values indicate a potential risk of Cd toxicity (Afonne & Ifediba, 2020), especially in Lubumbashi, where the values are generally higher. Cr levels are reflected in the THQ values for both Kinshasa and Lubumbashi, with Amaranthus sp. and Ipomoea batatas showing higher THQ values. Although the THQ for Cr remains below the critical value of one, persistent exposure to Cr, particularly in its hexavalent form (Cr(VI)), is a concern due to its carcinogenic properties (Oruko et al., 2021). The slightly elevated THQ values suggest a need for continuous monitoring to prevent chronic exposure risks (Afonne & Ifediba, 2020). Mn THQ values are elevated, particularly in Amaranthus sp. and Ipomoea batatas, but remain below the threshold of one. Mn is essential for human health in trace amounts. However, excessive exposure can lead to neurological problems, including manganese poisoning, a condition similar to Parkinson’s disease (Oruko Ongon’g et al., 2020b). The elevated THQ values indicate a potential risk of neurotoxicity, particularly with long-term consumption of these vegetables (Giri et al., 2022). Se THQ values, while generally low, are elevated in some vegetables, particularly Ipomoea batatas from Lubumbashi. Se is an essential micronutrient, but excessive intake can lead to selenosis, characterized by gastrointestinal upsets, hair loss, and neurological damage (Amarloei et al., 2023). Zn, another essential nutrient, shows THQ values below the threshold of one across all vegetables. However, the values are higher in Amaranthus sp. and Ipomoea batatas, particularly in Lubumbashi. While Zn is necessary for immune function and metabolic processes, excessive intake can lead to adverse effects such as immune dysfunction and reduced Cu absorption (Tongprung et al., 2024). The Zn THQ values, while not immediately alarming, indicate that Zn levels should still be monitored to prevent potential overexposure.

The THQ analysis highlights significant health risks associated with consuming vegetables contaminated with heavy metals in both Kinshasa and Lubumbashi. Pb, As, and Fe present the most severe risks, with THQ values exceeding safe thresholds, particularly in Ipomoea batatas and Amaranthus sp. While generally below the threshold, other metals, such as Cd, Cr, Mn, Al, Se, and Zn, still pose potential risks due to their elevated levels in certain vegetables. The findings emphasize the need for ongoing monitoring and intervention to reduce exposure to these harmful metals and protect public health in these regions.

Hazard index (HI)

Figures 3 (A, B) compare the Hazard Index (HI) values for different vegetables from Kinshasa and Lubumbashi, highlighting the potential health risks associated with trace element contamination (Amarloei et al., 2023). The HI is a crucial metric that quantifies the cumulative risk posed by exposure to multiple contaminants, with values greater than one indicating a significant potential for health risks (Mitra et al., 2022).

In Kinshasa, the HI values for the vegetables indicate varying degrees of contamination, all of which surpass the concern threshold of one. The leaves of Ipomoea batatas show the highest HI at 2.5, suggesting that they pose the most significant health risk among the sampled vegetables. This is closely followed by Amaranthus sp. with an HI of 2.2 and Hibiscus sabdariffa L. with an HI of 1.8. Brassica oleracea shows the lowest HI at 1.5, but even this value exceeds the safe threshold, indicating potential health concerns if consumed in significant quantities (Amarloei et al., 2023).

Lubumbashi's situation is markedly more severe, with substantially higher HI values across all vegetables, indicating a more critical risk to public health. Amaranthus sp. exhibits an alarmingly high HI of 1.8, pointing to an extreme health risk associated with its consumption. Ipomoea batatas leave, and Brassica oleracea also show very high HI values of 1.5 and 1.4, respectively, further underscoring the widespread issue of trace element contamination in the region. Although Hibiscus sabdariffa L. has the lowest HI in Lubumbashi at 0.9, it still presents a significant health risk, close to the safe threshold.

The comparative analysis between the two cities reveals that Lubumbashi experiences significantly greater trace element contamination in its vegetable produce compared to Kinshasa. The consistently elevated HI values across Lubumbashi's vegetables suggest pervasive environmental or agricultural sources of contamination contributing to these alarming levels. This situation calls for urgent and comprehensive measures, including environmental assessments, enhanced regulatory oversight, and strategies to mitigate exposure to these contaminants (Genthe et al., 2018).

The data underscores a significant health risk associated with consuming vegetables from both Kinshasa and Lubumbashi, with Lubumbashi presenting a more critical situation. Continuous monitoring and preventive interventions must be implemented to protect the health of local populations who rely on these vegetables as dietary staples.

The target cancer risk (TCR)

The target cancer risk (TCR) associated with exposure to As, Pb, Cd, and Cr through consuming contaminated vegetables in our study is detailed in Table 3. As indicated by the data for Kinshasa in Table 3, the TCR of As due to the consumption of Hibiscus sabdariffa L., Amaranthus sp., and leaves of Ipomoea batatas were 1.196 × 10⁻4, 1.267 × 10⁻4, and 1.223 × 10⁻4, respectively. In Lubumbashi, the TCR of As due to the consumption of Brassica oleracea, Hibiscus sabdariffa L., Amaranthus sp., and leaves of Ipomoea batatas leaves were 1.603 × 10⁻4, 1.812 × 10⁻4, 2.109 × 10⁻4, and 1.988 × 10⁻4, respectively. These values exceed the maximum threshold of 1 × 10⁻4, indicating a high risk of cancer exposure from consuming these local vegetables (Tongprung et al., 2024). It has been observed that the intake of vegetables does not pose a cancer risk to the adult population in the area from Pb, Cd, or Cr. This is because the TCR values for Pb, Cd, and Cr in samples from both cities were below the maximum threshold value. However, it is worth noting that the TCR value for As (1.9 × 10^− 8) reported by Shaheen et al. (2016) was much lower than the value reported in this study. Similarly, the TCR values for As reported in Ethiopia (Gebeyehu et al., 2020) were also lower due to the consumption of Brassica oleracea.

Table 3

Cancer risk associated with the presence of heavy metal in vegetable samples
Kinshasa
Metal	Brassica oleracea	Hibiscus sabdariffa L	Amaranthus sp	Ipomoea batatas
As	9.11 10^− 5	1.19 10^− 4	1.27 10^− 4	1.22 10^− 4
Cd	6.76 10^− 6	8.29 10^− 6	1.26 10^− 5	1.62 10^− 5
Cr	4.01 10^− 6	6.14 10^− 6	6.43 10^− 6	7.41 10^− 6
Pb	1.02 10^− 6	3.81 10^− 6	2.93 10^− 6	9.08 10^− 6
Lubumbashi
As	1.60 10^− 4	1.81 10^− 4	2.11 10^− 4	1.99 10^− 4
Cd	9.86 10^− 6	6.11 10^− 6	1.49 10^− 5	1.21 10^− 5
Cr	7.49 10^− 6	5.12 10^− 6	6.70 10^− 6	6.45 10^− 6
Pb	1.11 10^− 6	2.13 10^− 6	6.60 10^− 6	8.63 10^− 6

The comprehensive analysis of heavy metal concentrations in vegetables from Kinshasa and Lubumbashi has revealed significant contamination, posing potential health risks to the local population. Heavy metals such as Pb, Cd, and As exceeded recommended safety limits in both cities, especially in vegetables like Ipomoea batatas leaves, Hibiscus sabdariffa L., and Amaranthus sp. The utilisation of MPI and HI calculations further highlighted the elevated risks associated with consuming these vegetables, emphasising the urgent need for intervention and mitigation strategies. The EDI values also pointed to a potential overexposure to specific metals, mainly Pb and Cd, underscoring the critical need for continuous monitoring and stringent regulation of vegetable production practices. The THQ and TCR assessments indicated that metals like As, Pb, Cd, and Cr, especially in Kinshasa, could lead to non-carcinogenic and carcinogenic health effects surpassing acceptable thresholds. These findings highlight the imperative to implement stringent measures to reduce trace elements contamination in vegetable crops and protect public health. A comparative analysis between Kinshasa and Lubumbashi showed varying degrees of contamination, with Lubumbashi exhibiting higher metal concentrations, likely due to industrial and mining activities. This disparity signals the necessity for region-specific interventions tailored to address the unique sources of contamination in each city. In response to these findings, urgent actions are required to regulate agricultural practices, water sources, and industrial emissions to reduce trace elements exposure through vegetable consumption. Public awareness campaigns and proactive measures by regulatory bodies are crucial to minimise health risks associated with heavy metal-contaminated vegetables in these regions. Continued research and monitoring efforts are essential to assess the effectiveness of the implemented measures and ensure long-term environmental and public health sustainability.

Ethical responsibilities of authors

All authors have read, understood, and complied as applicable with the statement on "Ethical responsibilities of Authors" as found in the instructions for authors.

Disclosure of potential conflicts of interest

The authors declare no competing interests.

Research involving Human participants and Animals

Not applicable

Funding

No financial support was received for this work.

Consent to participate

Not applicable.

Consent for publication

Not applicable.

Human ethics

Not Applicable

Acknowledgements

The authors thank the Environmental Analytical Chemistry department at the School of Chemistry, the University of the Witwatersrand Johannesburg, for their valuable assistance in analysing the vegetable samples.

Contributions

Mputu Malolo Lievins: methodology, formal analysis and investigation, writing original draft preparation, Ndelo Matondo Patrick: write and review the manuscript, Tuakuila Joel: write and review the manuscript, Ndelo-di-Phanzu Josaphat: write and review the manuscript.

Abd Elnabi, M. K., Elkaliny, N. E., Elyazied, M. M., Azab, S. H., Elkhalifa, S. A., Elmasry, S., Mouhamed, M. S., Shalamesh, E. M., Alhorieny, N. A., Abd Elaty, A. E., Elgendy, I. M., Etman, A. E., Saad, K. E., Tsigkou, K., Ali, S. S., Kornaros, M., & Mahmoud, Y. A.-G. (2023). Toxicity of Heavy Metals and Recent Advances in Their Removal: A Review. Toxics, 11(7), 580. https://doi.org/10.3390/toxics11070580.
Afonne, O. J., & Ifediba, E. C. (2020). Heavy metals risks in plant foods – need to step up precautionary measures. Current Opinion in Toxicology, 22, 1–6. https://doi.org/10.1016/j.cotox.2019.12.006.
Agoro, M. A., Adeniji, A. O., Adefisoye, M. A., & Okoh, O. O. (2020). Heavy Metals in Wastewater and Sewage Sludge from Selected Municipal Treatment Plants in Eastern Cape Province, South Africa. Water, 12(10), 2746. https://doi.org/10.3390/w12102746.
Ahmed, S. F., Kumar, P. S., Rozbu, M. R., Chowdhury, A. T., Nuzhat, S., Rafa, N., Mahlia, T. M. I., Ong, H. C., & Mofijur, M. (2022). Heavy metal toxicity, sources, and remediation techniques for contaminated water and soil. Environmental Technology & Innovation, 25, 102114. https://doi.org/10.1016/j.eti.2021.102114.
Alfaro, M. R., Ugarte, O. M., Lima, L. H. V., Silva, J. R., Da Silva, F. B. V., Da Silva Lins, S. A., & Do Nascimento, C. W. A. (2022). Risk assessment of heavy metals in soils and edible parts of vegetables grown on sites contaminated by an abandoned steel plant in Havana. Environmental Geochemistry and Health, 44(1), 43–56. https://doi.org/10.1007/s10653-021-01092-w.
Amarloei, A., Mirzaei, S. A., Noorimotlagh, Z., Nazmara, S., Nourmoradi, H., Fard, N. J. H., Heidari, M., Mohammadi-Moghadam, F., & Mazloomi, S. (2023). Human health risk assessment of toxic heavy metals in summer crops and vegetables: A study in Ilam Province, Iran. Journal of Environmental Health Science and Engineering, 22(1), 139–148. https://doi.org/10.1007/s40201-023-00881-y.
Aransiola, S.A., Akinsola, R.O., Abioye, O.P., & Maddela, N.R. (Eds.). (2024). Emerging Contaminants in Food and Food Products (1st ed.). CRC Press. https://doi.org/10.1201/9781003438236.
Arslaner, A., Salik, M. A., & Bakirci, İ. (2021). The effects of adding Hibiscus sabdariffa L. flowers marmalade on some quality properties, mineral content and antioxidant activities of yogurt. Journal of Food Science and Technology, 58(1), 223–233. https://doi.org/10.1007/s13197-020-04533-z.
Atitsogbey, P., Kyereh, E., Ofori, H., Johnson, P.-N. T., & Steiner-Asiedu, M. (2023). Heavy metal, microbial and pesticides residue contaminations are limiting the potential consumption of green leafy vegetables in Ghana: An overview. Heliyon, 9(4), e15466. https://doi.org/10.1016/j.heliyon.2023.e15466.
Atta, M. I., Zehra, S. S., Dai, D.-Q., Ali, H., Naveed, K., Ali, I., Sarwar, M., Ali, B., Iqbal, R., Bawazeer, S., Abdel-Hameed, U. K., & Ali, I. (2023). Amassing of heavy metals in soils, vegetables and crop plants irrigated with wastewater: Health risk assessment of heavy metals in Dera Ghazi Khan, Punjab, Pakistan. Frontiers in Plant Science, 13, 1080635. https://doi.org/10.3389/fpls.2022.1080635.
Bist, P., & Choudhary, S. (2022). Impact of Heavy Metal Toxicity on the Gut Microbiota and Its Relationship with Metabolites and Future Probiotics Strategy: A Review. Biological Trace Element Research, 200(12), 5328–5350. https://doi.org/10.1007/s12011-021-03092-4.
Chinnannan K., Somagattu P., Yammanuru H., Reddy U.K., Nimmakayala P.(2024). Health risk assessment of heavy metals in soil and vegetables from major agricultural sites of Ohio and West Virginia, Biocatalysis and Agricultural Biotechnology, 57,2024, 103108. https://doi.org/10.1016/j.bcab.2024.103108.
Danouche, M., El Ghatchouli, N., & Arroussi, H. (2022). Overview of the management of heavy metals toxicity by microalgae. Journal of Applied Phycology, 34(1), 475–488. https://doi.org/10.1007/s10811-021-02668-w.
Edogbo, B., Okolocha, E., Maikai, B., Aluwong, T., & Uchendu, C. (2020). Risk analysis of heavy metal contamination in soil, vegetables and fish around Challawa area in Kano State, Nigeria. Scientific African, 7, e00281. https://doi.org/10.1016/j.sciaf.2020.e00281.
Faizan, M., Alam, P., Hussain, A., Karabulut, F., Tonny, S. H., Cheng, S. H., Yusuf, M., Adil, M. F., Sehar, S., Alomrani, S. O., Albalawi, T., & Hayat, S. (2024). Phytochelatins: Key regulator against heavy metal toxicity in plants. Plant Stress, 11, 100355. https://doi.org/10.1016/j.stress.2024.100355.
Fonge, B. A., Larissa, M. T., Egbe, A. M., Afanga, Y. A., Fru, N. G., & Ngole-Jeme, V. M. (2021a). An assessment of heavy metal exposure risk associated with consumption of cabbage and carrot grown in a tropical Savannah region. Sustainable Environment, 7(1), 1909860. https://doi.org/10.1080/27658511.2021.1909860.
Fonge, B. A., Larissa, M. T., Egbe, A. M., Afanga, Y. A., Fru, N. G., & Ngole-Jeme, V. M. (2021b). An assessment of heavy metal exposure risk associated with consumption of cabbage and carrot grown in a tropical Savannah region. Sustainable Environment, 7(1), 1909860. https://doi.org/10.1080/27658511.2021.1909860.
Gebeyehu HR, Bayissa LD (2020). Levels of heavy metals in soil and vegetables and associated health risks in Mojo area, Ethiopia. PLoS ONE 15(1): e0227883. https://doi.org/10.1371/journal.pone.0227883.
Genthe, B., Kapwata, T., Le Roux, W., Chamier, J., & Wright, C. Y. (2018). The reach of human health risks associated with metals/metalloids in water and vegetables along a contaminated river catchment: South Africa and Mozambique. Chemosphere, 199, 1–9. https://doi.org/10.1016/j.chemosphere.2018.01.160.
Giri, A., Bharti, V. K., Kalia, S., Acharya, S., Kumar, B., & Chaurasia, O. P. (2022). Health Risk Assessment of Heavy Metals Due to Wheat, Cabbage, and Spinach Consumption at Cold-Arid High Altitude Region. Biological Trace Element Research, 200(9), 4186–4198. https://doi.org/10.1007/s12011-021-03006-4.
Golia, E. E., Chartodiplomenou, M.-A., Papadimou, S. G., Kantzou, O.-D., & Tsiropoulos, N. G. (2021). Influence of soil inorganic amendments on heavy metal accumulation by leafy vegetables. Environmental Science and Pollution Research, 30(4), 8617–8632. https://doi.org/10.1007/s11356-021-17420-7.
Gupta, N., Yadav, K. K., Kumar, V., Prasad, S., Cabral-Pinto, M. M. S., Jeon, B.-H., Kumar, S., Abdellattif, M. H., & Alsukaibia, A. K. D. (2022). Investigation of Heavy Metal Accumulation in Vegetables and Health Risk to Humans From Their Consumption. Frontiers in Environmental Science, 10, 791052. https://doi.org/10.3389/fenvs.2022.791052.
Hassan, J., Rajib, Md. M. R., Khan, Md. N.-E.-A., Khandaker, S., Zubayer, Md., Ashab, K. R., Kuba, T., Marwani, H. M., Asiri, A. M., Hasan, Md. M., Islam, A., Rahman, M. M., & Awual, Md. R. (2024). Assessment of heavy metals accumulation by vegetables irrigated with different stages of textile wastewater for evaluation of food and health risk. Journal of Environmental Management, 353, 120206. https://doi.org/10.1016/j.jenvman.2024.120206.
Huang, F., Zhou, H., Gu, J., Liu, C., Yang, W., Liao, B., & Zhou, H. (2020). Differences in absorption of cadmium and lead among fourteen sweet potato cultivars and health risk assessment. Ecotoxicology and Environmental Safety, 203, 111012. https://doi.org/10.1016/j.ecoenv.2020.111012.
Ismael, D. S., & Goran, S. M. A. (2024). Health risk assessment of heavy metals in some vegetables-Erbil City-Kurdistan Region of Iraq. Environmental Monitoring and Assessment, 196(5), 417. https://doi.org/10.1007/s10661-024-12542-0.
Iyama, W., Okpara, K., & Techato, K. (2021). Assessment of Heavy Metals in Agricultural Soils and Plant (Vernonia amygdalina Delile) in Port Harcourt Metropolis, Nigeria. Agriculture, 12(1), 27. https://doi.org/10.3390/agriculture12010027.
Jolly, Y. N., Akter, S., Kabir, M. J., Mamun, K. M., Abedin, M. J., Fahad, S. M., & Rahman, A. (2024). Heavy Metals Accumulation in Vegetables and Its Consequences on Human Health in the Areas Influenced by Industrial Activities. Biological Trace Element Research, 202(7), 3362–3376. https://doi.org/10.1007/s12011-023-03923-6.
Jolly, Y. N., Akter, S., Kabir, M. J., Mamun, K. M., Abedin, M. J., Fahad, S. M., & Rahman, A. (2024). Heavy Metals Accumulation in Vegetables and Its Consequences on Human Health in the Areas Influenced by Industrial Activities. Biological Trace Element Research, 202(7), 3362–3376. https://doi.org/10.1007/s12011-023-03923-6.
Kayembe, J. M., Sivalingam, P., Salgado, C. D., Maliani, J., Ngelinkoto, P., Otamonga, J.-P., Mulaji, C. K., Mubedi, J. I., & Poté, J. (2018). Assessment of water quality and time accumulation of heavy metals in the sediments of tropical urban rivers: Case of Bumbu River and Kokolo Canal, Kinshasa City, Democratic Republic of the Congo. Journal of African Earth Sciences, 147, 536–543. https://doi.org/10.1016/j.jafrearsci.2018.07.016.
Langunu, S., Kilela Mwanasomwe, J., Colinet, G., & Ngoy Shutcha, M. (2024). Are Ecological Risk Indices for Trace Metals Relevant for Characterizing Polluted Substrates in the Katangese Copperbelt (DR Congo) and for Assessment of the Performance of Remediation Trials? Environments, 11(6), 122. https://doi.org/10.3390/environments11060122.
Lemessa, F., Simane, B., Seyoum, A., & Gebresenbet, G. (2022). Analysis of the concentration of heavy metals in soil, vegetables and water around the bole Lemi industry park, Ethiopia. Heliyon, 8(12), e12429. https://doi.org/10.1016/j.heliyon.2022.e12429.
Lu, W., Luo, H., He, L., Duan, W., Tao, Y., Wang, X., & Li, S. (2022). Detection of heavy metals in vegetable soil based on THz spectroscopy. Computers and Electronics in Agriculture, 197, 106923. https://doi.org/10.1016/j.compag.2022.106923.
Malamba-Lez, D., Tshala-Katumbay, D., Bito, V., Rigo, J.-M., Kipenge Kyandabike, R., Ngoy Yolola, E., Katchunga, P., Koba-Bora, B., & Ngoy-Nkulu, D. (2021). Concurrent Heavy Metal Exposures and Idiopathic Dilated Cardiomyopathy: A Case-Control Study from the Katanga Mining Area of the Democratic Republic of Congo. International Journal of Environmental Research and Public Health, 18(9), 4956. https://doi.org/10.3390/ijerph18094956.
Malczyk, E., Muc-Wierzgoń, M., Muc-Wierzgoń, M., Fatyga, E., & Dzięgielewska-Gęsiak, S. (2024). Salt Intake of Children and Adolescents: Influence of Socio-Environmental Factors and School Education. Nutrients, 16(4), 555.
Mata, H. K., Al Salah, D. M. M., Ngweme, G. N., Konde, J. N., Mulaji, C. K., Kiyombo, G. M., & Poté, J. W. (2020). Toxic metal concentration and ecotoxicity test of sediments from dense populated areas of Congo River, Kinshasa, Democratic Republic of the Congo. Environmental Chemistry and Ecotoxicology, 2, 83–90. https://doi.org/10.1016/j.enceco.2020.07.001.
Mitra, S., Chakraborty, A. J., Tareq, A. M., Emran, T. B., Nainu, F., Khusro, A., Idris, A. M., Khandaker, M. U., Osman, H., Alhumaydhi, F. A., & Simal-Gandara, J. (2022). Impact of heavy metals on the environment and human health: Novel therapeutic insights to counter the toxicity. Journal of King Saud University - Science, 34(3), 101865. https://doi.org/10.1016/j.jksus.2022.101865.
Naangmenyele, Z., Ncube, S., Akpabey, F. J., Dube, S., & Nindi, M. M. (2021). Levels and potential health risk of elements in two indigenous vegetables from Golinga irrigation farms in the Northern Region of Ghana. Journal of Food Composition and Analysis, 96, 103750. https://doi.org/10.1016/j.jfca.2020.103750.
Nguyen, T., Lin, X., Nyman, M., & Prykhodko, O. (2020). Monobutyrin and Monovalerin Affect Brain Short-Chain Fatty Acid Profiles and Tight-Junction Protein Expression in ApoE-Knockout Rats Fed High-Fat Diets. Nutrients, 12(4), 1202.
Ngweme G.N., Konde J.N.N., Laffite A., Kiyombo G.M., Mulaji C.K., Poté J.W. (2021). Contamination Levels of Toxic Metals in Marketed Vegetable (Amaranthus Viridis) at Kinshasa, Democratic Republic of the Congo. Food Science and Nutrition, 7(1), 1–8. https://doi.org/10.24966/FSN-1076/100087.
Niu, L., Cao, R., Kang, J., Zhang, X., & Lv, J. (2018). Ascorbate-Glutathione Cycle and Ultrastructural Analyses of Two Kenaf Cultivars (Hibiscus et al.) under Chromium Stress. International Journal of Environmental Research and Public Health, 15(7), 1467.
Njoku, K. L., & Nwani, S. O. (2022). Phytoremediation of heavy metals contaminated soil samples obtained from mechanic workshop and dumpsite using Amaranthus spinosus. Scientific African, 17, e01278. https://doi.org/10.1016/j.sciaf.2022.e01278.
Nuapia, Y., Chimuka, L., & Cukrowska, E. (2018). Assessment of heavy metals in raw food samples from open markets in two African cities. Chemosphere, 196, 339–346. https://doi.org/10.1016/j.chemosphere.2017.12.134.
Oguntade, O. A., Adegbuyi, A. A., Nassir, A. L., Olagunju, S. O., Salami, W. A., & Adewale, R. O. (2020). Geoassessment of heavy metals in rural and urban floodplain soils: Health implications for consumers of Celosia argentea and Corchorus olitorius vegetables in Sagamu, Nigeria. Environmental Monitoring and Assessment, 192(3), 164. https://doi.org/10.1007/s10661-020-8077-9.
Oruko Ongon’g, R., Edokpayi, J. N., Msagati, T. A. M., Tavengwa, N. T., Ijoma, G. N., & Odiyo, J. O. (2020a). The Potential Health Risk Associated with Edible Vegetables Grown on Cr(VI) Polluted Soils. International Journal of Environmental Research and Public Health, 17(2), 470. https://doi.org/10.3390/ijerph17020470.
Oruko Ongon’g, R., Edokpayi, J. N., Msagati, T. A. M., Tavengwa, N. T., Ijoma, G. N., & Odiyo, J. O. (2020b). The Potential Health Risk Associated with Edible Vegetables Grown on Cr(VI) Polluted Soils. International Journal of Environmental Research and Public Health, 17(2), 470. https://doi.org/10.3390/ijerph17020470.
Oruko, R. O., Edokpayi, J. N., Msagati, T. A. M., Tavengwa, N. T., Ogola, H. J. O., Ijoma, G., & Odiyo, J. O. (2021). Investigating the chromium status, heavy metal contamination, and ecological risk assessment via tannery waste disposal in sub-Saharan Africa (Kenya and South Africa). Environmental Science and Pollution Research, 28(31), 42135–42149. https://doi.org/10.1007/s11356-021-13703-1.
Parida, L., & Patel, T. N. (2023). Systemic impact of heavy metals and their role in cancer development: A review. Environmental Monitoring and Assessment, 195(6), 766. https://doi.org/10.1007/s10661-023-11399-z.
Rafique, M., Hajra, S., Tahir, M. B., Gillani, S. S. A., & Irshad, M. (2022). A review on sources of heavy metals, their toxicity and removal technique using physico-chemical processes from wastewater. Environmental Science and Pollution Research, 29(11), 16772–16781. https://doi.org/10.1007/s11356-022-18638-9.
Rahim, N., Noor, A., Kanwal, A., Tahir, M. M., & Yaqub, A. (2024). Assessment of heavy metal contamination in leafy vegetables: Implications for public health and regulatory measures. Environmental Monitoring and Assessment, 196(8), 684. https://doi.org/10.1007/s10661-024-12855-0.
Ramanlal, D. B., Kumar, R. N., Kumar, N., & Thakkar, R. (2020). Assessing potential of weeds (Acalypha indica and Amaranthus viridis) in phytoremediating soil contaminated with heavy metals-rich effluent. SN Applied Sciences, 2(6), 1063. https://doi.org/10.1007/s42452-020-2859-0.
Sagagi, B. S., Bello, A. M., & Danyaya, H. A. (2022). Assessment of accumulation of heavy metals in soil, irrigation water, and vegetative parts of lettuce and cabbage grown along Wawan Rafi, Jigawa State, Nigeria. Environmental Monitoring and Assessment, 194(10), 699. https://doi.org/10.1007/s10661-022-10360-w.
Sayo, S., Kiratu, J. M., & Nyamato, G. S. (2020). Heavy metal concentrations in soil and vegetables irrigated with sewage effluent: A case study of Embu sewage treatment plant, Kenya. Scientific African, 8, e00337. https://doi.org/10.1016/j.sciaf.2020.e00337.
Shabalala, A., D. Ngwenya, P., & Timana, M. (2022). Heavy Metal Contamination and Health Risk of Soils and Vegetables Grown Near a Gold Mine Area: A Case Study of Barberton, South Africa. Journal of Agriculture and Crops, 83, 197–207. https://doi.org/10.32861/jac.83.197.207.
Shah, A. H., Shahid, M., Tahir, M., Natasha, N., Bibi, I., Tariq, T. Z., Khalid, S., Nadeem, M., Abbas, G., Saeed, M. F., Ansar, S., & Dumat, C. (2023). Risk assessment of trace element accumulation in soil and Brassica oleracea after wastewater irrigation. Environmental Geochemistry and Health, 45(12), 8929–8942. https://doi.org/10.1007/s10653-022-01351-4.
Shaheen N, Irfan NM, Khan IN, Islam S, Islam MS, Ahmed MK.(2016). Presence of heavy metals in fruits and vegetables: Health risk implications in Bangladesh, Chemosphere; 152:431–438. https://doi.org/ 10.1016/J.
Tomno, R. M., Nzeve, J. K., Mailu, S. N., Shitanda, D., & Waswa, F. (2020). Heavy metal contamination of water, soil and vegetables in urban streams in Machakos municipality, Kenya. Scientific African, 9, e00539. https://doi.org/10.1016/j.sciaf.2020.e00539.
Tongprung, S., Wibuloutai, J., Dechakhamphu, A., & Samaneein, K. (2024). Health risk assessment associated with consumption of heavy metal-contaminated vegetables: A case study in the southern area of Northeast Thailand. Environmental Challenges, 14, 100845. https://doi.org/10.1016/j.envc.2024.100845.
Tőzsér, D., Yelamanova, A., Sipos, B., Magura, T., & Simon, E. (2023). A meta-analysis on the heavy metal uptake in Amaranthus species. Environmental Science and Pollution Research, 30(36), 85102–85112. https://doi.org/10.1007/s11356-023-28374-3.
Tshibanda, J. B., Atibu, E. K., Malumba, A. M., Otamonga, J.-P., Mulaji, C. K., Mpiana, P. T., Carvalho, F. P., & Poté, J. (2024). Persistent organic pollutants in sediment of a tropical river: The case of N’djili River in Kinshasa (Democratic Republic of the Congo). Discover Applied Sciences, 6(6), 314. https://doi.org/10.1007/s42452-024-05962-7.
Tuakuila, J., Lison, D., Lantin, A.-C., Mbuyi, F., Deumer, G., Haufroid, V., & Hoet, P. (2012). Worrying exposure to trace elements in the population of Kinshasa, Democratic Republic of Congo (DRC). International Archives of Occupational and Environmental Health, 85(8), 927–939. https://doi.org/10.1007/s00420-012-0733-0.
Ugulu, I., Khan, Z. I., Bibi, S., Ahmad, K., Munir, M., & Memona, H. (2024). Evaluation of the Effects of Wastewater Irrigation on Heavy Metal Accumulation in Vegetables and Human Health in the Cauliflower Example: Heavy Metal Accumulation in Cauliflower. Bulletin of Environmental Contamination and Toxicology, 112(3), 44. https://doi.org/10.1007/s00128-024-03858-1.
Zhang, X., Song, X., Zhang, H., Li, Y., Hou, Y., & Zhao, X. (2024). Source apportionment and risk assessment of heavy metals in typical greenhouse vegetable soils in Shenyang, China. Environmental Monitoring and Assessment, 196(1), 72. https://doi.org/10.1007/s10661-023-12250-1.
Zhang, Z., Zhang, Q., Liu, G., Zhao J., Xie W., Shang S., Luo J., Liu J., Huang W., Li J., and et al. (2022). Accumulation of Co, Ni, Cu, Zn and Cd in Aboveground Organs of Chinese Winter Jujube from the Yellow River Delta, China" International Journal of Environmental Research and Public Health 19, no. 16: 10278. https://doi.org/10.3390/ijerph191610278.

No competing interests reported.

Supplementaryinformation.docx

Health implications of heavy metal contamination in urban vegetables: Assessing the risks in Kinshasa and Lubumbashi

Status:

Version 1

Abstract

Figures

Introduction

Materials and methods

Study area and sample collection

Sample preparation

Sample analysis

EDI = \(\:\frac{CxFIR}{WAB}\) (1)

Hazard Index

The target cancer risk (TCR)

Metal pollution index

Statistical analysis.

Results and Discussion

Metal Pollution index

Potential Health Risks

Estimated Daily and weekly intake

Target hazard quotient

Hazard index (HI)

The target cancer risk (TCR)

Conclusion

Declarations

References

Additional Declarations

Supplementary Files

Status:

Version 1