Assessing health risk associated with uranium in Rietspruit water, far West Rand goldfield, South Africa

Uranium, U, as a radiological and chemically toxic element has detrimental impacts on human health when ingested at elevated concentration in water. Effluents from an underground gold mine located in the head water region of the Rietspruit contaminated the stream with waterborne uranium. The Rietspruit is a tributary of the Vaal River and subsequently flows through residential and agricultural land. Water samples from the stream were collected and analysed using inductively coupled plasma mass spectrometry to determine the concentrations of dissolved U. The maximum concentration of U recorded was 781.9 µg/L at the mine from where it decreases with growing distance from the mine. Results from calculations showed that the maximum annual effective dose at the mine was above the regulatory limit for public exposure for all age groups. The radiological risk associated with consumption of untreated water from the Rietspruit is lower than the chemical risk. The chemical risk ranges from 0 to 37.2 while the highest life-time cancer risk was 1.7 E-03 for morbidity cancer risk and 1.1 E-03 for mortality cancer risk. The chemical risk analysis showed that within 24 km of downstream of the mine, stream users are exposed to toxic U levels. Therefore, adequate interventions by relevant government agencies are required.


Introduction
The quality of most South African water resources has deteriorated over the years which poses serious health risks to humans and livestock (WWF-SA 2016). Due to a strongly negative climatic water balance where potential evaporation exceeds rainfall by several times in large parts of the country, including the study area, much of South Africa is affected by water scarcity (Bwapwa 2019). Some 62% of South Africa's limited water resources are currently used for irrigation and 11% for mining and industrial use (WWF-SA 2016;DWS 2020). Poor communities like informal settlements often suffer from a lack of piped water. Consequently, residents depend on the use of untreated surface water, as observed in the study area, exposing them to the risk of waterborne diseases. (Satterthwaite et al. 2020). In gold mining areas, much of the surface water is polluted with heavy metals, uranium inclusive. Uranium (U) has been reported to have health impacts on humans exposed to the element (Adams et al. 2010;ATSDR 2014;Bjørklund et al. 2020;Bleise et al. 2003;Winde 2011;Zamora et al. 1998). Depending on the solubility of the uranium compound, exposure route, and concentration, kidneys, lungs, bones are among the targeted vitals that could be damaged by U (ATSDR 2014; Dewar 2019; Keith et al. 2013;WHO 2001). Uranium is mined in South Africa in most cases as the by-product of gold mining (Ford 1993;Krige 1966;Tutu et al. 2003;Winde and de Villiers 2002). High concentrations of U have been found within gold mines in water and sediment (Durand 2012;Fashola et al. 2016;Kamunda et al. 2016;Raji et al. 2021).
Gold mining has been a contributing factor to the economy of South Africa; however, large volumes of mine wastes have been deposited as a result (Fedderke and Pirouz 2002;McCarthy 2011). In the Witwatersrand Basin, one of the richest gold deposits worldwide (Tutu et al. 2008), high concentrations of U have been recorded in some of the Editorial responsibility: Samareh Mirkia. mined gold reefs. About 70 years ago, the Far West Rand became the first goldfield in South Africa where commercial production of U was established (Coetzee et al. 2006). Winde (2001) reported an average U concentration of about 110 mg/kg in gold tailings, also known as slimes dam, across seven goldfields of the Witwatersrand Basin (Winde 2001). Winde (2004) concluded that for each ton of gold produced, more than 10 tons of U was brought to the earth's surface (Winde 2004). Mined gold reefs are therefore regarded as the original source of U (Winde and Sandham 2004).
Other sources of U pollution include mine waste deposits such as slimes dams and mine dumps often located close to streams or rivers. In many cases, these waste deposits are the primary source of U pollution of the nearby water bodies. The process includes the transport of dissolved U via seepage into underlying alluvial aquifers  and of U-bearing tailings particles by wind and water erosion (Winde and Sandham 2004). Uranium can be emitted from point sources or from non-point (diffuse) sources. Point sources include the discharge of fissure and processed water through canals and pipelines into nearby streams or dams also observed in this study. Even though the mine has been decommissioned about 5 years ago, dewatering of underground tunnels is still ongoing. Another example of point source is the storm-water run-off from slimes dams, storm-water retention dams, rock and sand dumps, etc. A typical example of diffuse sources of pollution includes seepage from slimes dams, and uncaptured run-off from various mine waste deposits included washed-off tailings material downstream of eroded slimes dams.
Uranium is released into the environment in a number of ways which include erosion of slime dams by wind and water leading to eroded slimes settling on dams, wetland, irrigation channels and agricultural land, etc. (Coetzee et al. 2006). In addition, there are spillages of tailings associated with burst pipelines, partial dam failures, etc.
High concentrations of U have been found several kilometres from the mining site in river sediment, wetlands, and dams as a result of precipitation, adsorption, co-precipitation, and bioaccumulation . Wetlands and dams have been identified as sinks for U and other toxic heavy metals such as mercury, lead, cadmium, arsenic (Coetzee et al. 2006;Ross and Dudel 2008;Schöner et al. 2009). Raji et al. (2021) recorded high concentrations of the aforementioned heavy metals above the acceptable limit in a wetland and dam located about 3 km and 6 km, respectively, away from a mining site (Raji et al. 2021). These sites can be a secondary source of U pollution and other heavy metals if there is a change in the water chemistry which could be influenced by the water's pH, electric conductivity, redox state, and seasonal changes (from winter to summer).
The focus of this study is on the Rietspruit, a small stream draining the south-eastern part of the Far West Rand (FWR) goldfield that is impacted by mining-related water pollution. The study explores the main pathways of U entering the Rietspruit system, the concentrations of dissolved U along the entire longitudinal profile of the Rietspruit as well as both the carcinogenic and non-carcinogenic risk assessments using the concentrations of U found at sampled sites.
Due to human exposure pathways witnessed during fieldwork, and the lack of information on the level of U users could be exposed to, it is imperative to assess potential health risks associated with ingestion of dissolved U found in the Rietspruit. This study will be used to sensitize the locals about the danger involved with the use of the water for domestic, agricultural, and religious purposes. Due to human exposure observed in the field, e.g. ingestion of the water from the stream, both carcinogenic and non-carcinogenic risks were assessed.
The objectives of this study are: 1) To determine the concentration of U in the Rietspruit water along its entire longitudinal profile from source to mouth. 2) To assess the health risk posed by the U levels in Rietspruit water. 3) To propose possible interventions and recommendations to local authorities.

Study area
The source of the Rietspruit is located in Gauteng Province, South Africa, about 1 km away from Ezulwini Gold and Uranium Mine. The Ezulwini Gold and Uranium Mine (coordinate: 26°21'46''S 27°42'52''E) was operational for about 56 years before it was decommissioned in August 2016. At the time of study, the mine still discharged its fissure and process water into the Peter Wright dam (PW dam) at a rate of approximately 68 ML per day. The outflow from the PW dam is currently the (man-made) source of the Rietspruit. It is believed that the Rietspruit will be a non-perennial river if the mine should stop discharging water into the PW dam (Kritzinger 2017).
The river flows for about 60 km south before joining the Vaal River (Fig. 1). The associated drainage region name is C22H according to the Department of Water Affairs and Sanitation comprising a catchment area of about 454 km 2 (Fig. 2). Tributaries of the Rietspruit include the Leeuspruit, the Evaton-Rietspruit, and the Klein-Rietspruit. While Leeuspruit is also polluted with U as a result of another gold mine being located upstream of the confluence with the Rietspruit, the Evaton-Rietspruit and Klein-Rietspruit are not polluted as they drain areas without mining activities. The Leeuspruit is in the C22J Quaternary Catchment draining some 668.7 km 2 (Department of Water Affairs and 1 3 Sanitation, 2011) (Fig. 2). As there are no mining or industrial activities in the catchments of the Evaton-Rietspruit and Klein-Rietspruit, the concentration of U in the water of these streams was used as the natural background concentration of U. Most farms located in the area depend on water from the Rietspruit for irrigation.
The climate of the study area is temperate, defined by moderately cold winters (April to August) and hot summers (October to March). Annual rainfall mainly occurs between October and March and with an average of about 664 mm. Evaporation is about twice the annual rainfall (about 1700 mm). In winter, the average temperature is 13 °C and 24 °C in summer (Kamunda et al. 2016).
The Ezulwini gold and uranium mine is located about 40 km south-west of Johannesburg in the Gauteng Province, South Africa. Gold is found in the upper Elsburg in the form of native gold and is associated with sulphide minerals (e.g. pyrite). Also, gold is found in the middle Elsburg reefs associated with pyrite underlying the mine and U is mined in the middle Elsburg reef (Kritzinger 2017), and it is found in the form of uraninite (Kritzinger 2017). This is the major source of all the U found in the Rietspruit.
Uranium is released from mine waste during a rain event and transported to PW dam, Rietspruit headwater. A concentration of about 52.7 µg/L of U was recorded in the fissure water discharged by the mine into the PW dam (Raji et al. 2021). According to Kritzinger (2017), about 68 ML of fissure water is pumped into the PW dam per day; this means the amount of U discharged into the PW dam is about 52 700 mg/L of U per day (Kritzinger 2017). Thus, the discharge of fissure water into the PW dam is the most significant U source into the Rietspruit.
The outflow from the PW dam into the Rietspruit makes the Rietspruit a perennial one. Observations during field sampling indicated that the Rietspruit water is used for drinking, cooking, bathing (especially by the residents of informal settlements within the area and religious worshippers), and animal watering and dam water is used for Field observation commenced on 13 July 2020 while water samples were collected on 28 August 2020 covering the total length of the Rietspruit within the Gauteng Province, South Africa.

Field work
A total of 28 water samples were collected on 28th of August 2020 along the entire length of the Rietspruit (Fig. 2). Water samples were collected in a 100 mL PVC water bottle below the water surface. The water bottle was rinsed three times with river water before collecting water samples. Water samples were taken in the middle of the river, depending on the depth of the site. Each water bottle was labelled accordingly and kept in a cooler box. The samples were taken to the laboratory the following day for chemical analysis. Samples were analysed in the laboratory to determine the concentration of U using inductively coupled plasma mass spectrometry (ICP-MS).
At each sampled site, the water pH, electric conductivity, temperature, and coordinates were taken using handheld instruments. The detailed readings and their influence on U concentrations were, however, published in the first part of this study (Raji et al 2021).

Laboratory analysis
The water samples were analysed in the Eco-analytical laboratory of the North-West University, Potchefstroom Campus, South Africa. Each water sample was first filtered using a 0.45 µm sieve to remove suspended particles. 1 mL of the filtered water was measured, and 9 mL of nitric acid was added to remove any dissolved organic material in the water. An Agilent 7500 CE ICP-MS with Collision Reaction Cell (CRC) technology for interference removal was used to determine the concentration of U in the water. In order to achieve a quantitative result, the instrument was calibrated using ULTRASPEC certified custom mixed multi-element stock standard (De Bruyn Spectroscopic Solutions, Midrand, South Africa) solutions containing all major trace elements which include U at a concentration of 10 µg/L. The ICP-MS detection limit for U was 0.31 µg/L.

Exposure assessment
According to the US EPA (1992), exposure assessment can be defined as the determination of the magnitude, frequency, and duration of exposure and exposure dose (EPA 1992). Exposure assessment includes identification of all important sources of pollutant, routes of exposure (exposure pathways), the potentially exposed population, mechanisms of pollutant transportation, quantification of exposure, toxicity assessment of pollutants, and risk characterization. Exposure assessment is one of the most essential steps in human health risk assessment with hazard identification, dose-response assessment, and risk characterization being the other steps (NRC 2009).

Source of uranium pollution
The main source of uranium, as a contaminant of concern, in the Rietspruit is the Ezulwini Gold and Uranium mine (Fig. 3). Slimes and waste rock are deposited on the surface. Oxidized mine wastes release U when it encounters water (in the form of rain, pore-water and seepage), which then runs off into the PW dam. The mine also discharges fissure water with elevated concentration of U, 52.7 µg/L, into PW dam as source of the Rietspruit. Fissure water consists of dolomitic water from the overlying karst aquifers that migrates via fractures and faults into the underlying main void. Where this water comes in contact with mined or unmined uraniferous ore, it can get contaminated resulting in elevated levels of dissolved U (Winde 2004). Another source of U in the Rietspruit injection of washed-off tailings materials is eroded by water and wind from nearby mine waste deposits.

Exposure pathways
In this study, the pathways include the usage of the water for domestic, religious and agricultural purposes. Domestic and religious activities observed in the Rietspruit include drinking of the Rietspruit water, using the water for cooking, bathing in the river, as well as fishing in the dam located downstream of the river (Fig. 4). The water is also used for the irrigation of farmlands. A commercial wheat plantation located a few kilometres from the Ezulwini Mine uses the water from the dam for irrigation (Figs. 3 and 4c). Several studies have been done on the uptake of U and other heavy metals by plants (Dzoma et al. 2010;Edayilam et al. 2020;Genthe et al. 2018;Gupta and Walther 2020;Hakonson-Hayes et al. 2002).
Wind erosion is another pathway. The deposition of tailings materials on nearby farmland could potentially introduce U into the food chain due to the uptake by plants. The consumption of animals that were fed with plants irrigated with polluted water is also another route for indirect consumption of U by humans ( Fig. 4a and b). Formal and informal settlers within the immediate environment of the slime dams could also be exposed as a result of inhaling dust particles (Fig. 4e).
The only exposure pathway considered in this study is the oral ingestion of U from drinking water. This is the most prevalent exposure pathway experienced in the Rietspruit by different population groups that depend on the water for both domestic and religious activities and the primary objective of this study.

Mechanism of transport
The major mode of transportation of U from the point source to the Rietspruit is through water and air.

Exposed population
The majority of the inhabitants in the study area live in informal settlements, e.g. Lawley (Fig. 1). Informal settlements are housing areas often built illegally on municipal land (Huchzermeyer 2009). Most of the houses in an informal settlement are built out of metal sheets and other materials which are in most cases reused or repurposed (Fig. 4e).
Another group of exposed residents are the worshippers using the water from the river for their various religious activities which include drinking. On several visits to site 6, 7, 8, 9, and 11, cooking activities using water from the river were also witnessed as well as bathing in the river. The worshippers are of different age groups and sex.

Annual effective dose (radiation dose) due to the ingestion of uranium in Rietspruit water
Whenever there is human contact with a hazardous chemical as U in this study, there is exposure (Means 1989). Residents and worshippers using the water for drinking, cooking, bathing are therefore exposed. In order to screen the area that could constitute a health risk, radiation doses for all the sampled sites were calculated and compared with the radiation dose limit prescribed by UNSCEAR (2000), 0.1 mSv/y, to control the presence of radionuclide in water used for drinking.
The annual effective absorbed dose is the estimated value of radiation energy absorbed by the human body as a result of an intake of a certain amount of radioactivity in a year (DWAF 2002). In order to calculate the annual effective dose, Eq. 1 was used.
(1) Annual effective dose = C × AWI × DCF Fig. 4 Exposure pathways witnessed in Rietspruit; a: cattle grazing in the Rietspruit river b: cattle grazing next to the canal used by the mine to discharge water c: wheat plantation irrigated by water from PW dam, d: local residents fishing in PW dam, e: informal settlement within the study area where C is the activity concentration of U (Bq/L), DCF is the dose conversion factor for a specific age group (Sv/Bq) and AWI is the age-dependent annual water intake (L/year). The annual water intake default values for different age groups and the dose conversion factor values were obtained from the Department of Water Affairs handbook (DWAF 2002). The concentration of natural U (U nat ) recorded in the water was converted to activity concentration using 1 µg/L = 0.025 Bq/L as the conversion factor (Dowdall et al. 2013;Duggal et al. 2021).

Lifetime cancer risk (Carcinogenic risk assessment)
The lifetime cancer risk (risk factor) estimates the likelihood of developing cancer due to exposure to a carcinogen (Bleam 2012). In order to calculate the lifetime risk factor due to the consumption of the Rietspruit water, Eq. 2 was used. The concentrations of U in the Rietspruit water were converted to uranium activity concentration (Bq/L). 1 µg/L = 0.025 Bq/L.
As U decays, its decay products such as radon, lead, thorium, radon, radium, etc. emit alpha, beta and gamma radiation that results in internal exposure to the exposed population once U is ingested. Based on the zero-threshold linear dose model, any absorbed dose of U is believed to result in an increased risk of cancer. The model stipulates that with every exposure to an ionizing radiation, there is a linear increasing risk of causing cancer. Due to the accumulation of U in certain human organs, the risk of cancer of the bone, liver, and blood is believed to increase (Golden et al. 2022;Keith and Faroon 2022).
The calculation is based on the assumption that the activity concentration of U at each site remains constant and the resident only consumes untreated stream water of this U-concentration at the specified rate throughout their lifespan (i.e. a highly unlikely scenario that overestimates the true risk significantly). This method was designed by the US EPA (USEPA 1986) and has been used in several studies (Bleam 2012;Giri and Jha 2012;Okeyode and Jibiri 2013).
In order to calculate lifetime cancer risk, the activity intake of U must be determined using the concentration of dissolved uranium quantified in the water samples collected at each site. Equation 3 was used to calculate the uranium activity intake: (2) Lifetime cancer risk = Uintake (Bq/L) over a lifetime × risk coefficient where C is the uranium activity concentration (Bq/L), ED is the lifetime exposure duration (70 years), and EF is the exposure frequency (365 days per year). Lifetime cancer morbidity and mortality risk coefficients for uranium are 1.3E-09 and 1. 73E-09, respectively (EPA;Radiation, 2000).

Hazard quotient (Non-carcinogenic risk assessment)
Hazard quotient (HQ) is the ratio of the lifetime average daily dose at each site and the reference dose for U, 0.6 µg/ kg/day, ) through the ingestion of drinking water. A reference dose (RfD) is the estimate of the dose level considered safe for human consumption (ATSDR 2014). It relates the dose at the exposure point to a toxicological endpoint (Bleam 2012). Hazard quotient below 1 signifies no risk while above 1 means there is risk. The hazard quotient has been used to assess the health risk of U in several studies (Giri and Jha 2012;Kamunda et al. 2018;Njinga et al. 2016).

Concentration of U in collected water samples
The highest concentration of U (781.9 µg/L) in the water was recorded at the inflow of PW dam (Rietspruit headwater) ( Table 1). It decreases gradually with distance from the mine. This is similar to the study of Davidson (2003) which also reported a gradual reduction in the concentration of U moving downstream from the source of pollution (Davidson 2003).
The concentration of U in the water is above the WHO guideline limit in drinking water, 30 µg/L (WHO 2012), and South Africa standards, 10 µg/L, in water used for irrigation and 30 µg/L in drinking water (DWAF 1996) for about 24 km away from the point source. The concentration of U in the water used for the irrigation of the wheat plantation (Fig. 4c) is 52.7 µg/L. Hakonson-Hayes et al. (2002) concluded that the concentration of U in plants is directly proportional to the concentration of U in the water used for the irrigation of the plant (Hakonson-Hayes et al. 2002). The consumption of such plants by humans and animals that fed on the plant could be detrimental to human health (ATSDR 2014;Bjørklund et al. 2020;Corlin et al. 2016).
(4) Hazard quotient = lifetime average daily dose reference dose The reduction in the concentration of U from the point source downstream is attributed to the dilution effect from unpolluted water (e.g. discharge from water treatment plants and tributaries), infiltrating groundwater and the river water-sediment interplay which removed dissolved uranium from water column into the riverbed and vice-versa. Despite the reduction in the concentration of U in water downstream, the site used for religious activities, Site8 in Table 1, has U concentration more than twice the guideline limit of U in water. This is about 6 km from the source of the pollutant. Factors responsible for the increase and decrease in the concentrations of U at these sites were discussed in previous study by Raji et al. (2021).
The concentrations of U at the sites designated as this study natural background concentration of U were 0.3 µg/L at the Evaton Rietspruit and 0.7 µg/L at the Klein-Rietspruit. As mentioned earlier, these sites were selected as the natural background concentration of U because there is no mining activity or industrial operation upstream of the river. At the Leeuspruit tributary, the concentration of U in the river was 17.4 µg/L. A gold mine is located about 24 km upstream of the sampled site (Fig. 1). Besides Table 1 Concentration of uranium in the stream (28th August 2020) *The field number is the ascribed number on collected water sample, and the flow distance is the approximated distance of sampled site from the PW dam; MU is the measurement uncertainty the grazing of cattle and the location of farmlands along the Leeuspruit, no human exposure was witnessed. The source of the water used for irrigation of the farmlands is unknown. However, Leeuspruit water might be used by the residents of the informal settlements within this area.

Hazard quotient (Non-carcinogenic risk assessment)
The lifetime average daily dose (LADD) of U due to the ingestion of Rietspruit water ranged from 0.0 to 22.3 µg/kg/ day of uranium with an average of 2.1 µg/kg/day. As mentioned earlier, the HQ was estimated for uranium using a reference dose of 0.6 µg/kg/day as recommended by EPA OGWDW (2000). The result of the non-carcinogenic risk (chemical risk) ranged from 0 to 37.2 (Fig. 5). The minimum HQ was recorded at sites selected as the natural background concentration of U in the study area. Similar to the U concentration in the Rietspruit, the maximum HQ was recorded at the PW dam inlet. In this study, HQ was above 1 for about 24 km from the mining environment (Fig. 5). With human exposure observed within this radius, it means people drinking from the water could be exposed to chemical toxins as a result of ingesting U in the water.

Annual effective dose due to the ingestion of uranium in Rietspruit water
There are many human exposure pathways for U; however, the major pathway witnessed during the field survey was considered in this study, ingestion through drinking of water. From Fig. 6, it was confirmed that an individual annual radiation dose limit of 0.1 mSv/year (for members of the general public) prescribed by UNSCEAR (2000) was exceeded at the PW dam inlet for all the age groups. At PW dam outflow, the radiation dose limit was exceeded by the 15 years age group while the rest of the age groups' annual effective dose was equal to the radiation dose limit, 0.1 mSv/year (Fig. 6). This means the ingestion of the water at the observed U activity concentration will cause a proportional increase in the chance of a health effect. Given the numerous exposure pathways that may cause radiation exposure, it was recommended by the International Commission on Radiological Protection (ICRP) to keep individual exposure doses to a minimum. This is essential in order to keep the total dose received by an individual below the annual dose limit.
At sites where human exposure was observed, the annual effective dose was not greater than 0.1 mSv/year for all the age groups (damlit outflow, between damlit, religious site, and post-religious site). The maximum effective dose was recorded at the PW dam inlet for all the age groups (Fig. 6). This coincided with the maximum Fig. 5 Non-carcinogenic risk: via drinking untreated stream water only at site-specific U-concentrations observed on 28 August 2020 concentration of U recorded in this study. The annual effective dose is in the order 15 years' age group as the highest > adults > 1 year > infants > 5 years and 10 years.
In Table 2, the values of annual water intake (AWI) and dose conversion factor (DCF) used to calculate the annual effective dose were given. Also included in Table 2 are the minimum, maximum, average, and standard deviation for each of the studied age groups.

Lifetime cancer risk (Carcinogenic risk assessment)
According to US EPA, 1991, lifetime cancer risk ranging from 1.0E-06 to 1.0E-04 is acceptable and above 1.0E-04 requires immediate remediation while a cancer risk below 1.0E-06 is not considered to pose any significant health effect (Fryer et al. 2006;Hu et al. 2012). Using Eq. 2, the result of the cancer risk is displayed in Fig. 7.
The highest mortality cancer risk recorded was 1.1 E-03 and 1.7E -03 for morbidity cancer risk. The result revealed  that more than 1 person in 1000 person are at risk of both mortality and morbidity cancer as a result of ingestion of dissolved U from the Rietspruit water. These values were the only values above the radiological risk limit (1.0E-03) in this study. From the result above, (Fig. 7), downstream users of the Rietspruit water are below the cancer risk limit and can be considered safe. Similar to the exposure dose result, the PW dam inlet has the highest cancer risk (Fig. 7). This means the sites require immediate intervention. Since no human contact was witnessed in this environment, possible human exposure to U will be the consumption of cattle that graze within this environment and consumption of plants irrigated with U-polluted water ( Fig. 4a to d)-indirect exposure (Dzoma et al. 2010).

Recommendation
Due to the high concentration of U found in the study area, the usage of the water for domestic, agricultural, and religious activities should be discouraged. This could be achieved by educating the inhabitants of the informal settlements, farmers, and worshipers about the health impacts of U and the concentration of U in the water used for these activities.
Mining companies in conjunction with relevant government agencies should work together in order to remediate this situation. This will help in reducing human exposure to the U.

Limitations
The risk assessments are all based on the assumption that the concentrations of U will remain constant and people consume only Rietspruit water at the given quantity per day throughout their lifespan. This is unrealistic and results in a significant overestimation of actual exposure and associated health risks.
Furthermore, individual risk can be influenced by genetic, age, sex, diet, state of health and lifestyle factors; as a result, lifetime cancer risk does not estimate the actual risk of any individual. Generally, poor communities are particularly vulnerable due to malnutrition, lack of access to adequate health care, poverty related stress levels, and high prevalence of other diseases negatively affecting the immune system including HIV/AIDS, tuberculosis, etc. commonly found in mining areas.

Conclusion
The maximum concentration of U, 781.9 µg/L, was recorded around the Elzuwini Gold and Uranium Mine which is the primary source of U in the Rietspruit. Where human exposure was observed, the concentrations of U ranged from 49.2 to 181.2 µg/L. The exposed population are therefore exposed to both chemical and radiological risks from U.
The chemical toxicity of U in the Rietspruit has values above the standard limit. The HQ was above 1 for about 24 km away from the mine. These are sites where human exposure, cattle grazing, and farmlands were observed.
Radiological (lifetime) cancer risks of mortality and morbidity due to Rietspruit water consumption are above the safe limit of 1.0E3 within the mining environment. The grazing of cattle within this environment and the use of the water for irrigation activity could be an entry point for the introduction of U into the food chain. Also, people observed drinking water at these sites and fetching the water for domestic purposes are at risk of radiological exposure.
This study revealed that the probability of carcinogenic risk is low; however, the non-carcinogenic risk may be due to the chemical toxicity of U. It will be recommended that the mining environment should be fenced in order to limit cattle grazing, portable water should be provided for the informal settlers, and farmers and religious activities along the stream should be discouraged.
Author contributions Conceptualization was performed by IBR, EH, EE, AN, and FW; methodology by IBR, EH, EE, AN, and FW; investigation by IBR; resources by IBR; writing-original draft preparation-by IBR; writing-review & editing-by IBR, EH, EE, AN, and FW; visualization by IBR, EH, EE, AN, and FW; supervision by AN and FW; funding acquisition by WF and HE. All authors have read and agreed to the published version of the manuscript.
Funding The study was funded by Sasol Research and North-West University.

Conflict of interest
The authors declare that there is no conflict of interest regarding the publication of this manuscript.
Ethical approval This article does not contain any studies with human participants or animals performed by any of the authors.