1. Introduction
Unrehabilitated asbestos mines continue to be a significant environmental and public health concern that impacts communities situated nearby [
1,
2,
3]. More than 230,000 people die every year from asbestos dust exposure; meanwhile, 125 million people worldwide remain at high risk of occupational exposure to asbestos [
4,
5,
6,
7]. A recent study indicated that more than 55 countries have banned the mining and use of asbestos [
8,
9]. Despite the ban on exploring this mineral in countries such as Canada, China, Russia, South Korea, Kuwait, Norway, Australia, Japan, and South Africa, asbestos continues to pose substantial health and environmental hazards, especially in areas closer to unrehabilitated mines and disposal sites [
8,
9,
10,
11]. In South Africa, unrehabilitated asbestos mines are prevalent in communities of Mpumalanga, Northwest, Northern Cape, and Limpopo provinces [
12,
13,
14,
15,
16]. The scientific context related to asbestos exposure from these unrehabilitated areas is important; hence, this study is inevitable.
Asbestos mines are evenly distributed globally, guided by the presence of naturally occurring asbestos in those specific areas. For example, ref. [
17] focused on the distribution of active and inactive asbestos mines globally and highlighted that the chrysotile asbestos mines were located in the northern hemisphere, particularly in North America, Europe, and Asia. The authors of [
18] further highlighted that, in North America, the majority of the asbestos mines were located in Canada, including British Columbia, Newfoundland and Labrador, Ontario, and Quebec, as well as Yukon Territory. Thirteen asbestos mines were located in Quebec Province, which include a small open-pit mine at Puturniq in Nunavik and the largest open-pit asbestos mine, Jeffrey Mine [
19]. Abandoned asbestos mines and their associated environmental legacies are not unique to North America but represent a global concern. In Europe, the Amiantos mine in Cyprus was one of the largest asbestos mines and remains inactive, with long-term environmental and health implications. Italy also hosts several former asbestos mining and processing sites, including the Balangero mine in Piedmont and other asbestos-bearing localities in Valle d’Aosta, Biancavilla (Sicily), Lombardy (e.g., Crestun), Traversella, and Brosso [
1,
6]. These sites have been widely documented as sources of persistent asbestos contamination in surrounding soils, sediments, and communities, highlighting the global relevance of asbestos-related environmental risk. On the other hand, ref. [
20] focused on the distribution of asbestos mines in South Africa, Lesotho, and Swaziland. Their results highlighted that chrysotile asbestos mines were predominant in Mpumalanga, Limpopo, and Northern Cape. Anthophyllite asbestos mines were mostly located in Limpopo Province, whereas crocidolite asbestos mines were situated in both Limpopo and Northern Cape. Limpopo Province is the sole province that has extracted four varieties of asbestos [
20]. A study by ref. [
13,
21] demonstrated that there are unrehabilitated asbestos mines, shafts, tailings, and dumps in different communities of the province. However, few studies have been identified that focus on the distribution of asbestos mines in the local context where risk and vulnerability to exposure and environmental contamination are imminent. As such, this study aims to focus specifically on determining the distribution of asbestos minerals in a rural area of Limpopo, the Ga-Mathabatha community, where unrehabilitated asbestos mines are located.
Geographic information system (GIS) and remote sensing techniques are valuable tools used for mapping the potential spatial distribution of naturally occurring fibrous silicate minerals, including those associated with waste materials from abandoned asbestos mines [
22,
23]. In this study, these geospatial tools were applied to assess the spatial distribution of asbestos-prone lithologies and mineral assemblages associated with fibrous silicate minerals within the juristriction of the Ga-Mathabatha community.
Additionally, the field observation method was adopted to validate the distribution of asbestos in different areas. Furthermore, other conventional techniques such as rock sampling, petrographic analysis, and X-ray diffraction (XRD) have been widely used to determine the mineral composition of geological formations [
24,
25]. Petrographic analysis is valuable for the examination of mineral textures and fabric relationships; however, in asbestos-related investigations its applicability is limited. In particular, petrographic methods cannot reliably distinguish among serpentine polymorphs, including chrysotile, lizardite, and antigorite. Consequently, X-ray diffraction (XRD) remains essential for the accurate identification of asbestos-related mineral phases, and for this reason many studies rely primarily on XRD for mineralogical characterization [
25]. For example, X-ray diffraction was used to analyze thirteen serpentinite rock samples from the Pollino area (Southern Apennines) in Italy [
26]. In the Durango mining site of Mexico, ref. [
27] utilized 2D electrical resistivity imaging (ERI) to detect abandoned and undocumented historic silver mining infrastructure. Meanwhile, in the Iranian city of Karaj, for instance, ref. [
28] successfully employed a phase-contrast microscope and magnetic survey to investigate the airborne asbestos fiber concentration, which was 1.84 fibers per liter (f/L) using phase contrast microsopy (PCM) and 18.16 f/L using scanning electron microscopy (SEM), higher than the regulated exposure standard. In this study, however, none of the conventional techniques was utilized, and we only relied on identifying the distribution of asbestos using its physical properties, such as colors, as adopted and guided by the literature [
29,
30,
31].
Communities residing near unrehabilitated asbestos mines remain at risk of exposure, and this raises significant public health concerns [
5]. Asbestos dust exposure causes respiratory lung diseases such as asbestosis, mesothelioma, and lung cancer. Asbestosis is a chronic lung disease caused by long-term inhalation of asbestos fibers [
32]. This disease leads to lung scarring (fibrosis) and respiratory complications [
33]. Studies on the communities affected by unrehabilitated asbestos mines are very limited, as scholars focused on occupational exposure. For example, ref. [
34] highlighted that, globally, more than 200,000 deaths are estimated to be caused by occupational exposure to asbestos, of which more than 70% are deaths from work-related cancers. For instance, in terms of occupational fatalities in the United Kingdom, the annual record is 3500, while in the United States, it is 10,000 [
35]. South Africa reports approximately 200 cases of mesothelioma annually [
36]. Approximately 30 percent of mesothelioma cases in South Africa are associated with environmental exposure, predominantly in the Northern Cape region. More than 70 percent of documented environmental cases impact women and children, who are most likely to have been exposed through fibers carried home on miners’ hair and clothing [
36]. Other provinces such as Limpopo, Mpumalanga, and Northwest are well known for post-asbestos mines concentrated there, with an unknown number of fatalities caused by the exposure.
Existing studies in South Africa have predominantly examined asbestos contamination from a technical and environmental perspective, focusing on mine impacts, rehabilitation status, and the mineralogical and geochemical characteristics of asbestos-bearing materials [
13,
16,
36]. Although geospatial and mineralogical analyses have improved understanding of asbestos distribution and persistence, these studies largely overlook the human dimension of exposure. Specifically, there remains a clear research gap in integrated studies that simultaneously assess the spatial distribution of asbestos debris and community awareness and perception of associated health risks. This study addresses this gap by empirically analyzing asbestos distribution in Ga-Mathabatha and evaluating community awareness and perception of asbestosis risk. The objectives of this study were to (i) evaluate the geographical distribution of asbestos-prone lithologies and mineral assemblages associated with fibrous silicate minerals within the juristriction of the Ga-Mathabatha community and (ii) awareness and perception of asbestosis risk in the Ga-Mathabatha community, Limpopo Province, South Africa.
2. Materials and Methods
2.1. Study Area
This study was conducted in Ga-Mathabatha, a rural area in the Capricorn District of Limpopo Province, South Africa (see
Figure 1a,b). The area is situated between 24°11′–24°14′ S and 29°46′–29°56′ E, covering a total area of 50.4 km
2 with an elevation of 772 m (2533 feet) above sea level [
37,
38]. It is divided into the following villages: Bodutlolo, Shushumela, Scheiding, Ga-Makgoba, Maseleseleng, Madikelong, Makapeng, Ga-GG, Lekgwareng, Mphaaneng, Roma, Ebenherzar, Masioneng, Mmashadi, and Success (see
Figure 1a). Access to the community water supply is still an ongoing crisis, and community members depend on boreholes, water from local rivers, and rainwater harvested from rooftops [
37]. The Ga-Mathabatha area is characterized by an annual average rainfall of 497 mm and an annual average temperature of 24 °C [
39]. Regionally, the study area falls within the Kaapvaal craton, which is one of the few regions on Earth where many relatively pristine Mid-Late Archaean rocks have been preserved [
40,
41,
42]. The craton covers an area of about 1.2 × 106 km
2 and predominantly comprises granitoid with interspersed greenstone belts, covered by various Late Archaean to Meso-proterozoic sedimentary and volcano-sedimentary basins.
Ga-Mathabatha is among the regions in South Africa where asbestos extraction was historically undertaken, with mining activities continuing until the government halted asbestos mining in 2002, followed by the formal closure of operations in 2008 after several decades of activity [
13,
16,
43]. Asbestos mines in this area include the Uitkyk, Lagerdraai, and Uitval asbestos sites [
44]. Upon their closure, a proper mine rehabilitation plan was implemented by the Department of Mineral Resources (DMR), and a contract to rehabilitate these mines was awarded to Minteck and GCS [
45]. However, due to unforeseen circumstances, not all asbestos mines were rehabilitated. According to [
16], Lagerdraai and Uitkyk sites in the Bewaarkloof Nature Reserve, near Chuenespoort, were rehabilitated, while Uitval and Weltevreden asbestos mines were abandoned with no observed evidence of rehabilitation. The Weltevreden asbestos mine was located at the Bewaarkloof near Chuenespoort, approximately 10 km from Ga-Mathabatha. Reports from [
13,
46] and SABC News reports highlighted that there were more than 10 unrehabilitated asbestos shafts, dumpings, and resurfacing of asbestos fibers causing environmental pollution in the community. Furthermore, abundant asbestos houses, roofing, dumpings, tailings, and asbestiform minerals were observed on the soils downstream as well as in surrounding areas [
13,
46]. According to the locals, the presence of asbestos debris, dust, and loose fibers in the community has contributed to respiratory health-related issues and unmeasured fatalities [
13,
46].
2.2. Data and Methods
A case study design was utilized for its advantage of allowing an in-depth, localized spatial analysis of distribution and human awareness and perceptions within the specific geographical context of Ga-Mathabatha. To achieve a comprehensive understanding, the study adopted a mixed-methods approach to assess the spatial distribution of asbestos and community awareness and perceptions of asbestosis risk. According to [
47], a mixed-methods design collects and analyzes both qualitative and quantitative data in order to study the research problem broadly and deeply. As such, quantitative methods such as remote sensing and household survey analysis were integrated with qualitative methods such as in-depth interviews and field observations to investigate the spatial distribution of asbestos and community awareness of asbestosis risk in the study area. Furthermore, triangulation was applied by cross-validating multiple data sources—remote sensing maps with field observations and household survey responses with in-depth interviews—to enhance credibility and reliability and ensure a holistic perspective on asbestos distribution and exposure.
2.3. Satellite Data Acquisition and Processing
Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery from Ministry of Economy, Trade and Industry (METI) and Japanese industrial/research partners, Japan, Tokyo was used to map the location and distribution of asbestos minerals in the study area. ASTER is an advanced multispectral remote imaging instrument that covers a wide spectral region with 14 bands ranging from the visible to the thermal infrared region with high spatial, spectral, and radiometric resolutions. The resolution varies with the spectral region: 15 m in the visible and near-infrared (VNIR), 30 m in the short-wavelength infrared (SWIR), and 90 m in the thermal infrared (TIR). These three spectral regions have three, six, and five bands, respectively. Each ASTER scene has a swath width of 60 km. ASTER has been widely used to discriminate different Earth materials based on the dissimilarity that exists among their spectral properties [
48,
49,
50].
The ASTER imagery selected for this study includes one ASTER L1T cloud-free scene acquired in August 2005 from the US Geological Survey (USGS) website (
https://earthexplorer.usgs.gov/, accessed on 15 October 2024). This winter scene was relatively less vegetated compared to other scenes collected during the summer season. The authors of [
51] argue that vegetation density negatively affects the amount of mineralogical information that can be retrieved from the processing of remote sensing data. In addition to this, ASTER data collected in 2005 carry all fourteen bands, unlike data collected post-2009, which lack SWIR bands due to the failure of the SWIR instrument in 2008 [
52]. Minerals associated with asbestos, such as chrysotile, tremolite, serpentine, and actinolite, have diagnostic spectral features in the VNIR and SWIR regions, thus making these spectral regions the most significant regions for mapping minerals of interest [
52]. Therefore, ASTER bands are considered appropriate for the accurate mapping of minerals of interest in this study.
2.4. Processing of ASTER Satellite Data
The processing of ASTER satellite imagery was carried out using ENVI software (version 5.1). Out of fourteen ASTER bands, only nine bands from VNIR and SWIR spectral regions were used for mineral mapping due to their relatively high spatial resolution and spectral wavelengths favorable for mapping minerals of interest [
53,
54]. The VNIR and SWIR bands were stacked together to form a single multiband layer. During band stacking, the SWIR bands with 30 m by 30 m resolution were resampled using the nearest neighbor resampling method to match the spatial resolution (15 m by 15 m) of VNIR bands. This was done so that all nine bands could have the same spatial resolution, which is a prerequisite for further spatial analysis.
The log residuals atmospheric correction technique was then applied to the VNIR-SWIR multiband layer to remove atmospheric effects and to convert ASTER L1T radiance data to surface reflectance data. Conversion from radiance to surface reflectance is essential for multispectral image processing when detecting the presence of surface targets using a reference mineral spectral library, as spectral libraries are signatures of surface reflectance [
5].
2.5. Mapping of Asbestos Minerals
Mapping minerals of interest requires reference mineral spectra. These could be acquired from spectral libraries like the USGS or image extraction. In this study, the USGS spectral libraries of asbestos minerals were used to map chrysotile, tremolite, serpentine, and actinolite (
Figure 2). The spectral libraries were resampled to match the VNIR-SWIR ASTER bands. Firstly, central wavelengths of the VNIR-SWIR bands were provided, and then ENVI assumed critical sampling and used a Gaussian model with an FWHM equal to the band spacings.
The ASTER resampled asbestos mineral libraries (
Figure 2) were used to generate areas with potential to host asbestos minerals based on the spectral mapping process which is discussed in the following section.
Spectral Matching
To perform spectral matching, the spectral information divergence (SID) mapping algorithm was employed. A spectral matching process was performed in order to compare the image spectra to known mineral spectral libraries from USGS databases (
Figure 3). In this case, SID uses divergence measures to match the pixels of an image (under question) to known reference mineral spectral libraries. The smaller the divergence value, the more likely the pixels and reference spectra are similar [
55]. The divergence between unknown
ri and
rj reference spectra can be defined as:
SID (ri, rj) represents the symmetrized divergence between two signals or distributions ri and rj.
((ri||rj) is the Itakura–Saito divergence between ri and rj and
((rj||ri) is the Itakura–Saito divergence between rj and ri, but reversed.
SID results in a classified image showing the best fit between each pixel and input mineral reference spectra depending on the divergence measure. Additionally, rule images are provided showing the divergence measure values between each pixel and each reference spectrum [
54].
Finally, the ASTER resampled spectral libraries of asbestos minerals were used to produce asbestos mineral maps of the study area.
Figure 3.
(a) Asbestos minerals mapped with SID algorithm; (b) The asbestos mineral and parent geology structure (Source: Authors’ creation).
Figure 3.
(a) Asbestos minerals mapped with SID algorithm; (b) The asbestos mineral and parent geology structure (Source: Authors’ creation).
2.6. Accuracy Assessment
To evaluate the reliability of the asbestos distribution map derived from ASTER imagery, an accuracy assessment was conducted using ground truth data collected from field observations and known asbestos exposure sites. A confusion matrix was generated to compare the classified results with reference data. From this matrix, standard accuracy metrics—overall accuracy (OA), producer’s accuracy (PA), user’s accuracy (UA), and kappa coefficient (κ)—were computed following [
56].
The accuracy assessment quantifies how well the spectral-angle-based classification (SID) distinguishes asbestos-bearing surfaces from non-asbestos lithologies and helps identify areas of spectral confusion, particularly between crocidolite and other fibrous or silicate minerals with similar spectral signatures.
2.7. Asbestos Field Observations
This study utilized field observation techniques to confirm areas predicted to contain high levels of asbestos-related minerals through remote sensing spectral and imagery analyses. The purpose of using field observation was to document and capture concrete, verifiable evidence of different types of asbestos rocks present in different locations within Ga-Mathabatha. A systematic side observation/inspection was conducted to eximine asbestos-bearing rocks and contaminated soils within the Ga-Mathabatha community. Rock and soil samples were collected across the community, and each sample and sample point was recorded and documented accordingly. Preliminary identification of asbestos-bearing materials was carried out using a handheld magnifying lens (field hand lens). The lens was used to examine the physical characteristics of the samples, including minerals, fibers, color variations, and structural composition to distinguish them from one another.
Observations were further adopted to identify potential asbestos-containing materials (ACMs) based on observable physical characteristics, the adjacent environmental context (local ultramafic and serpentinized lithologies), and proximity to documented historical asbestos mining operations. Photographs and notes were taken to document the extent and distribution of potential asbestos-bearing materials prior to geospatial analysis.
It is recognized that visual inspection alone cannot definitively verify the presence of asbestos, since other fibrous substances may display comparable physical characteristics [
13,
14,
15]. Therefore, field observations were employed as a screening and contextual evaluation instrument rather than as a definitive identification method. Laboratory mineralogical analyses (such as PLM or XRD) were not performed owing to resource constraints and scope limitations. Therefore, the findings are understood as suggesting the prospective or suspected presence of asbestos rather than definitive confirmation of asbestos occurrence.
2.8. Community’s Level of Awareness and Perceptions of Asbestosis Risk
Two methods of data collection, namely, in-depth interviews and household surveys, were blended to assess the community’s level of awareness and perceptions of the risk of asbestosis. Initially, a semi-structured interview guide was used in an exploratory phase to elicit information and reveal variations in perspective, experiences, and opinions of the specific target population that revealed potential themes and variables that were important in informing the development and design of more focused and valid final questions for the survey questionnaire. As such, the respondents for the in-depth interviews were selected using purposive sampling, where the Ga-Mathabatha households were selected due to their closer proximity to unrehabilitated mines. Furthermore, the data collection process continued until a saturation point was reached, with 18 respondents, where no new information was being presented by the respondents. After the 14th interview, no new information (codes or themes) emerged and interviews 15, 16, 17, and 18 produced repetition of previously identified information. This indicated that additional interviews were unlikely to yield new insights. Therefore, recruitment was stopped at 18 respondents. The decision was based on data saturation rather than predefined sample size. The results from the interviews were used to provide depth to the interpretation of statistical analysis results from the questionnaire [
57,
58]. The plan was to triangulate findings from both types of data; hence, the preliminary survey instrument that aligns with the qualitative research was created during the proposal stage but was modified to create a context-specific questionnaire as new data from interviews were recorded.
Meanwhile, the household survey was conducted using a structured questionnaire with closed-ended questions to elicit information on the demographic and socio-economic characteristics, awareness, and perceptions of the participants. The total number of households in Ga-Mathabatha for the year 2023 was not known; therefore, Cochran’s formula was used to determine the estimate sample size. Cochran’s (1963:75) formula at a 90% confidence level with
p = 0.5, while
q is 1-
p, with a confidence interval of +/− 5%, was adopted to ensure representativeness. Cochran’s formula is a well-established statistical method for determining sample sizes in survey studies that seek to ensure representativeness, particularly when the study population is larger or unknown. Equation (2):
where:
n0 = the required sample size;
Z = the z-value corresponding to the desired confidence level (1.645 for 90% confidence level);
p = the estimated proportion of the population;
e = the desired level of precision (also called margin of error);
q = 1 − p (the estimated proportion of the population).
The calculated total number of households using Cochran’s formula was 271, however, only 250 questionnaires were issued and administered due to limitations such as time frame, resources and accessibility. Therefore, the total sample size used in this study was 250 households. The 250 households were selected using simple random sampling, and within each selected household, the head of the household was purposely selected to complete the survey. If the household head was not available, anyone between the ages of 15 and 18 or older was allowed to participate.
Raw data from survey questionnaires was coded using Microsoft Excel 2016 Version and imported into Statistical Package for Social Sciences (SPSS) Version 27 for analysis. Descriptive statistical analysis was used to summarize demographic characteristics (e.g., gender and age) and socio-economic characteristics (e.g., occupation, level of education, and marital status) as variables. Additionally, chi-square (χ2) statistical tests were performed to establish the possible association between independent and dependent variables. Specifically, Pearson’s chi-square analysis tool in SPSS was adopted to analyze the relationship between age and asbestosis risk, level of education and community awareness of asbestosis, and years spent in the community and awareness and perception of asbestosis risk. The significance level (α) was set at 0.05, and the results were reported using p-values derived from the chi-square test. A p-value less than 0.05 indicated a statistically significant association between the variables.
4. Conclusions and Recommendations
This study examined the spatial distribution of asbestos and the community’s awareness of asbestosis in the Ga-Mathabatha area. Remote sensing using ASTER imagery revealed the presence of fibrous asbestos minerals—chrysotile (a serpentine polymorph), tremolite, and actinolite—often occurring in overlapping clusters. These minerals were predominantly associated with ultramafic parent lithotypes, reflecting the local geology conducive to asbestos formation. Field observations further revealed extensive surface contamination in Success, Makapeng, and Maseleseleng villages, as well as along the Olifants and Tongwane river systems. The widespread occurrence of asbestos-prone rocks, soils, and mine-related debris along gravel roads and within residential areas indicates that both naturally occurring and disturbed asbestos-bearing materials remain accessible to the community. These findings address the first objective of the study and suggest a high potential environmental and public health risk. Consequently, continuous monitoring of water, air, and soil quality is essential, together with targeted interventions such as phytoremediation, removal of scattered asbestos debris, and improved waste management in collaboration with local authorities. Demographic findings further reveal patterns that shape vulnerability and risk perception within the community. The predominance of female participants aligns with rural demographic trends, while the high representation of individuals aged 25–34 and elders above 65 reflects a population with long-term residency, historical mining ties, and lived experiences that influence their engagement with asbestos-related issues. The low participation rates of males point to a persistent challenge in rural research, suggesting the need for flexible, targeted recruitment strategies. These demographic dynamics indicate that environmental risk in Ga-Mathabatha is influenced not by a single factor but by the intersection of residence duration, historical exposure, livelihood dependence on natural resources, and accessibility of information.
Community awareness remains a critical concern. Nearly half of participants were unaware that villages such as Makapeng, Success, and Maseleseleng—including the Tongwane, Olifants, and Mphogodima rivers—are areas of high asbestos concentration. Misunderstandings about exposure pathways, especially through water sources and livestock movement, highlight a dangerous knowledge gap. This lack of awareness may contribute to ongoing exposure and future increases in asbestosis cases. Therefore, strengthening community education is essential. Public seminars, school-based programs, farmer and builder training, and regulation of asbestos-contaminated sand are necessary to reduce risk and prevent disease.
Collectively, these findings demonstrate that asbestos contamination in Ga-Mathabatha is both an environmental and social challenge, shaped by mineral distribution and geological context, demographic characteristics, and limited awareness. The study contributes new evidence on the co-occurrence of asbestos minerals, identifies specific exposure hotspots, and highlights urgent gaps in knowledge and governance. Addressing these issues requires integrated environmental monitoring, targeted health education, and coordinated intervention by government, researchers, and local communities to reduce long-term health risks and promote a safer living environment.
The spatial distribution analysis also identified Maseleseleng, Makapeng, Success, and Madikane as high-concentration asbestos zones. Accordingly, local decision-makers—including tribal authorities and ward councillors—should refrain from allocating new residential stands, farming plots, or development projects in these hazardous areas. Restricting development in contaminated zones is essential to preventing future exposure and safeguarding community health.
The community observations and asbestos distribution results demonstrate a high level of environmental contamination in Ga-Mathabatha. It is therefore recommended that the South African Government, through the Department of Mineral Resources (DMR) and Mintek, intensify and revive rehabilitation programs for abandoned asbestos mines, shafts, and associated waste dumps. The findings on community awareness further revealed that 45.6% of participants were unaware of the presence of asbestos in their surroundings, and 10% did not know what asbestosis is, highlighting a significant knowledge deficit. To address this gap, schools, hospitals, and traditional authorities should collaborate with non-governmental organizations, qualified educators, trained healthcare professionals, and environmental specialists (including Mintek Consulting) to implement regular, community-wide awareness initiatives. These programs should utilize local radio stations, community meetings, social media platforms, and strategically placed educational posters to disseminate accurate information on asbestos risks and safe practices.