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Article

Workers’ Exposure to Respirable Dust and Quartz in the Southern African Large, Medium, Small and Artisanal Small-Scale Mining Industry: An Exploratory Study

by
Norman Nkuzi Khoza
1,2,*,
Oscar Rikhotso
3,
Thokozane Patrick Mbonane
2,
Dingani Moyo
4,5,6,
Phoka Caiphus Rathebe
2 and
Masilu Daniel Masekameni
1,7
1
Human Capacity and Institutional Development, African Union Development Agency—NEPAD, Midrand 1685, South Africa
2
Department of Environmental Health, School of Health Sciences, University of Johannesburg, Johannesburg 2028, South Africa
3
Department of Environmental Health, Faculty of Science, Tshwane University of Technology, Pretoria 0001, South Africa
4
Baines Occupational Health Services, Harare 024, Zimbabwe
5
Department of Community Medicine, Faculty of Medicine, National University of Science and Technology, Bulawayo 029, Zimbabwe
6
Division of Occupational Health, School of Public Health, University of Witwatersrand, Johannesburg 2193, South Africa
7
Developmental Studies, School of Social Sciences, University of South Africa, Pretoria 0003, South Africa
*
Author to whom correspondence should be addressed.
Safety 2026, 12(3), 58; https://doi.org/10.3390/safety12030058
Submission received: 27 September 2025 / Revised: 14 November 2025 / Accepted: 2 December 2025 / Published: 30 April 2026
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Abstract

Mining activities are characterised by a multiplicity of inherent occupational hazards. Exposure to mineral dust such as silica, asbestos, and coal dust is common in mining, leading to pneumoconiosis. Exposure to respirable silica-containing dust is one of the common respiratory hazards associated with adverse health effects such as silicosis, lung cancer, renal failure, scleroderma, systemic lupus erythematosus (SLE) and chronic obstructive pulmonary disease (COPD), to mention but just a few. In southern Africa, there is a rising epidemic of silicosis, human immunodeficiency virus (HIV) and tuberculosis (TB). Excessive exposure to silica-containing dust exacerbates the TB and silicosis epidemic in mining areas. There is poor control of dust exposure and a lack of occupational hygiene assessments of silica dust in mining in southern Africa. In southern Africa, there remains a persistent knowledge gap regarding the extent of occupational exposures to respirable chemical substances, such as silica dust. Consequently, occupational hygiene air monitoring was conducted in mining companies across four low-income Southern Africa Development Community (SADC) countries, Lesotho, Mozambique, Malawi and Zambia, to provide a baseline exposure dataset. The hazardous nature of work associated with mining activities still persists in these low-income countries, with 53% (n = 72) of quarries and 20% (n = 19) of coal mines having respirable quartz exposures exceeding the reference occupational exposure limit (OEL) of 0.1 milligrams per cubic meter (mg/m3). The highest exposure ranges for quartz were recorded in surface aggregate quarries, with the maximum concentration recorded at 2.739 mg/m3. The highest number of air samples (93%, n = 111), which were in compliance with the OEL of 3 mg/m3 for respirable dust, were recorded in the copper, diamond, ruby, cement quarry and gold mines. This exploratory study confirms the variable extent of mineworker exposure to respirable dust and corresponding quartz fractions emanating from different mining activities. The collected exposure data provides a baseline overview of exposures within the mining industry in the SADC region. It also serves as a vital input for future regional exposure surveillance databases, as well as preliminary data for directing future research towards regional exposure prevention initiatives.

1. Introduction

The mining industry continues to contribute to both the growth of the global economy and social development [1,2]. The economic growth of African countries, specifically, is anchored by the mining industry, an outcome of their rich mineral resource endowment inclusive of gold and diamonds [3]. The other common minerals in Africa include coal, iron ore and copper [1]. The minerals serve as important raw materials or inputs for the manufacture of modern technological products. The mining industry contributed above 50% of the total mineral exports, earning governments and companies alike billions of dollars in revenue through revenue and taxes in countries such as Mozambique and Zambia between 1996 and 2016 [1]. However, the mining industry’s economic contribution has waned over the years [4], notwithstanding the increase in commodity prices. Quite often, low-income and developing countries prioritise economic development with minimal consideration for occupational health and safety (OHS) aspects [5]. Despite the recorded positive contribution of the mining industry in the socio-economic aspects, Workers involved in the extraction of these minerals have been adversely affected through injuries and occupational diseases resulting from exposure to inherent health hazards associated with the industry [6,7,8]. The societal and regulatory response to these occupational diseases and injuries has been the enactment of occupational health and safety legislation, such as the Mine Health Safety Act in South Africa [9], the Mine Safety and Health Act in the United States [10], as examples in the SADC countries. However, across the four countries, these regulatory frameworks remain grossly inadequate and fragmented [11]. The impact of these regulatory instruments, as well as advancements in mining technologies and methods, has reduced exposure to some extent [12]. However, exposure to various chemical, ergonomic and physical hazards still persists to this date [6,13,14,15]. Furthermore, the lack of exposure databases and occupational disease and injury surveillance curtails the objective measurement of the effectiveness of these introduced regulatory instruments [16]. Employers and regulatory authorities have been assigned the ultimate role of conducting and analysing exposure monitoring data for various purposes [17]. Employers are specifically mandated to conduct statutory exposure monitoring and report the data to regulatory authorities at various frequencies, depending on current or previous exposure results.
Workers conducting activities associated with mining operations are exposed to different dust fractions [18]. The Mine Health and Safety Act in South Africa, as an example, regulates exposure to dust through the prescription of objective OELs, levels above which employers are mandated to institute specific exposure control measures [9]. Exposure monitoring remains the cornerstone for decision-making, as it informs employer actions for determining legal compliance, as well as control institutions [16,17]. The mandatory requirement for occupational exposure monitoring is, however, dependent on the political will of policymakers, as is the case in countries such as the Russian Federation [19], South Africa [20,21] and the United Kingdom [22], amongst others. In low-income and some developing countries, in general, exposure to occupational health hazards, such as excessive dust levels remains largely undocumented [23] and is often exacerbated by lack of regulation and outdated legislation, weak enforcement regimes and low compliance levels on the part of employers [24,25,26,27]. In some SADC countries, such as Botswana, Zambia and Zimbabwe, the full implementation of OHS systems remains incomplete and lags behind that of other low-income and developing countries [28] and they are unable to prevent occupational disease incidence, particularly for small-scale mining operations [29,30]. The situation is exacerbated by the limited OHS coverage of the large informal sector in these countries, which remains largely unregulated [24]. Within the informal sector, OHS legislation is also largely ignored [25]. For low-income countries, the benefits deriving from regulatory inspections often outweigh the expended costs, resulting in a protracted status of unsafe work conditions [31]. The long-term, unprotected inhalation exposure to dust, such as coal dust, which also contains a quartz dust fraction based on the type of mined ore, is associated with COPD and pneumoconiosis [32,33]. Furthermore, exposure to quartz dust fractions contained within coal dust and other mineral ores has been shown to result in silicosis, a form of pneumoconiosis closely linked to lung cancer [7,32,34]. This highlights the importance of exposure data in establishing its association with occupational diseases [17]. Furthermore, mineworkers diagnosed with silicosis are often misdiagnosed to have TB, a communicable disease of public health concern. The prevalence of silicosis and TB amongst mineworkers exposed to dust in the SADC countries, especially South Africa, has been extensively studied and poses an even greater public health risk to the broader community [35,36,37,38]. Studies quantifying exposure monitoring have, however, been previously conducted and limited to the gold mining industry [39,40]. However, there remains limited exposure to monitoring data in the mining industry from Zambia, Lesotho, Malawi, and Mozambique, particularly in other mining operations that extract different commodities. In Mozambique, previous studies have focused on mercury exposure amongst artisanal gold miners [41,42]. This highlights the pressing need for heightened efforts directed towards both exposure quantification and control in these countries.
This paper reports on the extent and distribution of respirable dust exposure from the mining industries of the four countries. The exposure monitoring data provides a basis for regional policy convergence on the management of TB and other occupational lung diseases associated with occupational dust exposure in the mining industry.

2. Materials and Methods

2.1. Project Scope, Mine Selection and Ethical Clearance

This is a retrospective cross-sectional study reviewing occupational hygiene assessments performed in four countries: Lesotho, Malawi, Mozambique and Zambia (See Figure 1). The ministries responsible for mining in each respective country provided a list of continuing mining operations, from which mines with probable respirable silica dust and quartz exposures were specifically targeted for sampling. Thereafter, the project team divided and classified the mines into preassigned mining scales. The inclusion of the selected mining operations was informed by consideration of the scale of the mine, the commodity mined and available job titles/categories. Due to the study’s exploratory nature, mines included in the study were purposely selected, given the limited project funding and site accessibility. As shown in Table 1, a total of 21 mines (Lesotho, N = 5; Malawi, N = 3; Mozambique, N = 6; Zambia, N = 7) were included. The mines were involved in the mining of diamonds (n = 2), aggregates (n = 6), coal (n = 4), limestone (n = 2), rose quartz (n=1), ruby (n = 1), gold (n = 1), copper (n = 2) and manganese (n = 1), either through surface or underground mining processes. Table 1 also displays the total number of mine workers at each respective mine during the survey period.
The study received ethical clearances from the Faculty of Health Sciences Research Ethics Committee, ethics number: NHREC Registration: REC-2859-2024. Furthermore, gatekeeper permission was granted by the mines management.

2.2. Air Sampling and Analytical Methods

Respirable dust was collected as per the BS EN 481:1993 convention [43] as the target contaminant for this study. The general method for the detection of hazardous Substances (MDHS)14/4 [44], MDHS 101/2 [45,46] and NIOSH 7500 [47] methods were considered. A South African-based analytical laboratory, certified in accordance with the South African National Accreditation System 17025 (ISO/IEC 17025) [48], prepared the filter papers, conducted the gravimetric weighing and crystalline silica analysis, and issued a testing certificate outlining the results of all analysed samples. The MDHS 14/4 was, however, the primary method used throughout the study. Workers were issued with a Sensidyne Gilian GilAir-3 Air Sampling Pump, connected to a sampling head via a length of flexible tubing. The sampling head consisted of a 25 mm mixed cellulose ester (MCE) filter with a generic Higgins-Dewell sampler (cyclone) attached. The cyclone separates the respirable dust fraction (4–10 µm) from the coarse dust fraction, which is captured in the grit and discarded. The MCE filters were preferred due to their reduced susceptibility to moisture absorption and static build-up, which can result in excessive weight. The personal sampling pump was attached to the worker’s belt, and the sampling head was placed in the worker’s breathing zone, on the collar of their overalls, to ensure the sample represented the dust inhaled during the shift. These instruments were worn throughout the shift, during both work and rest periods. Each personal sampling pump was calibrated at a flow rate of 2.2 L per minute before and post checked after sampling. Following gravimetric weighing, X-ray diffraction was used to determine the percentage of quartz from the sampled respirable dust [44,45,47]. A total of 350 respirable dust samples were collected across the selected mines in the four countries. A standardised field sheet was used to record sample identification, sampling pump number, sampling start and end time, pre- and post-calibration values, Worker job category, calculated deviation percentage between the pre- and post-calibration values, work area, volume sampled, and sampling date. The entire sampling run was conducted, supervised, and overseen by certified occupational hygiene professionals, using a single-period 8-h sampling strategy [49].

2.3. Data Management and Statistical Analysis

The gravimetric and analytical results from the laboratory were input into an Excel spreadsheet for cleaning. To assign exposures to each monitored occupation, the cleaned data were input into the Expostats statistical toolkit freely available from www.expostats.ca [50,51] to determine the mean, median, standard deviation, geometric mean, and geometric standard deviation. These statistical variables are important indicators for interpreting the results. The results represent normalised 8-h time-weighted average (TWA) exposure.

3. Results

3.1. Overall Overview of Samples Taken and Compliance

A total of 350 respirable dust samples were collected across the four countries. The overall compliance overview of the samples is shown in Table 2. The respirable dust and quartz (Table 3) results were compared to the reference OEL values of 3 mg/m3 and 0.1 mg/m3, respectively, currently used in South Africa [9]. A large percentage of both the respirable dust samples (93%, n = 111) and corresponding quartz concentrations (98%, n = 117) taken in the copper, gold, and ruby mines complied with the referenced OELs. For coal mines (Table 4), a large percentage of the respirable coal mine dust (96%, n = 90) and corresponding quartz concentrations (80%, n = 75) were also within the referenced occupational exposure limit. For samples taken in quarries (Table 5), only 47% (n = 65) of the quartz samples met the reference OEL. For statistical analysis, exposure concentrations below the detection limits of the instruments used were set to 0.01 mg for quartz.

3.2. Overall Respirable Dust and Quartz Exposures

Table 3 presents the respirable dust exposure and corresponding quartz fractions for each country and mine. Of the 350 respirable dust samples, the highest geometric mean for respirable dust was recorded in Mine 1 (Zambia) at 0.88 mg/m3. The highest geometric mean for quartz at 1.13 mg/m3 was recorded in Mine 2 (Malawi) at 1.13 mg/m3. Malawi (all mines) had the highest quartz ranges above the reference OEL, followed by Zambia (Mines 1, 3, 4 and 6) and Lesotho (Mines 3 and 4).

3.3. Respirable Coal Mine Dust and Quartz Exposures

Table 4 provides exposure ranges for respirable coal mine dust and corresponding quartz fractions. Both the highest respirable coal mine dust exposure (6.721 mg/m3) and quartz (0.217 mg/m3) ranges exceeding the respective reference OELs were recorded in Mine 1 (underground mine), Malawi. The highest exposure range for quartz (1.8 mg/m3) was also exceeded at Mine 3 (surface mine), Zambia.

3.4. Quartz Exposure in Quarries

Quarrying is associated with high exposure to respirable quartz concentrations, high risk of silicosis and other occupation-induced respiratory diseases. Table 5 provides an overview of the quartz concentrations from the case quarries. The geometric mean for all quartz concentrations across all quarries included indicates overexposure, with the highest quartz exposure range (2.739 mg/m3) recorded in a surface limestone quarry (Mine 4) in Zambia. Comparatively, surface aggregate quarries Mine 5 (Lesotho) and Surface Aggregate Quarry Mine 3 (Mozambique) had low quartz exposure ranges, presenting a low risk of silicosis. The comparable overall mean quartz exposures were above the reference OEL, an indicator of excessive exposure and high risk of silicosis.

3.5. Respirable Dust and Quartz Concentration Exposure in Comparison with the Respective Occupational Exposure Limits

Among the total mean exposure results across the sampled mines in the study countries, none of the respirable dust results exceeded the recommended occupational exposure limit of 3 mg/m3; the highest exposure was 2.06 mg/m3, while the minimum was 0.005 mg/m3. However, 14% of the results were above 50% of the stated occupational exposure limit (Figure 2). However, 33.3% of the overall quartz exposure concentration across countries exceeded the recommended exposure limit of 0.1 mg/m3. A maximum exposure result of 1.76 mg/m3 was recorded, which is seventeen times higher than the occupational exposure limit (Figure 3).

4. Discussion

This study provides insight into the extent of mineworker exposure to respirable dust, respirable coal mine dust and corresponding quartz concentrations associated with select mining activities/per commodity in four SADC countries. The measured exposure concentrations confirm the hazardous nature and presence of occupational health hazards associated with mining activities. Overall, the results indicate a variation in respirable dust exposure from mine to mine, relative to the commodity being mined. The recorded worker exposures are influenced by prevailing weather, production levels, and work practices [52], as well as the extraction and processing methods employed at each mine [53]. The United States’ NIOSH surveillance reports on exposures in the coal mining industry [16,54]. Also, confirm the widespread and historical nature of exposures in the coal mining industry. The NIOSH surveillance exposure data covering 1982–2017 for respirable coal mine dust at surface mines also indicates that exposure concentrations in mines still exceed OELs [54], highlighting the inherent nature of mine-related occupational health hazards [6]. Exposure to respirable dust in the mining industry also extends to other countries, as noted in a Turkish study [55], an Australian study [18], and a Tanzanian study [56]. For example, a study conducted at a Mongolian copper mine revealed that mineworkers were exposed to levels exceeding both the respirable and quartz dust fractions [57]. Exposure concentrations exceeding the OEL value indicate the possible failure of the current hierarchical control measures, such as engineering and administrative controls, to adequately protect workers [58]. Exposures below the reference OEL may not be protective enough and should be supplemented by corresponding medical surveillance to determine the complete health of workers [59,60].
Apart from the generic exposure to dust, workers in coal mines are concurrently exposed to respirable coal mine dust and crystalline silica, also known as quartz. The quartz content in respirable coal mine dust, however, fluctuates with the coal type [61] and encountered geological mine conditions [62]. On this point, only 24% of the respirable coal mine dust samples collected and reported in the NIOSH surveillance report exceeded the OEL for quartz in coal dust [16,54]. The results in this current study indicate that only a small proportion of workers were exposed to both respirable coal mine dust exposure levels at half the OEL for the reference OELs used. In a Tanzanian study, quartz concentrations were recorded at 0.75 mg/m3 and 0.027 mg/m3, respectively [55]. In view of the double potency of coal dust, the United States’ approach to regulating exposure to respirable coal mine dust, with or without quartz, incorporates different OELs for both air contaminants, depending on the exposure concentrations [62,63]. The countries in this study, where OHS regulation still lags, can consider such an approach in their efforts to minimise the high incidence of respiratory diseases such as COPD among mineworkers concurrently exposed to respirable mince coal dust and quartz [64].
Exposure to respirable dust with high fractions of quartz, particularly in mining operations, was also widespread, with quarrying being the most prominent type of attributable mining (Table 5). This confirms that quarrying and the mining industry in general, exposed a high number of workers to quartz [65]. The exposure concentrations also confirm that the quartz content in mining ores varies by mined commodity, with both high mean respirable dust exposure and quartz concentrations, as well as high mean respirable dust with low quartz concentrations noted (Table 4). The prevailing quartz exposures are alarming and should prompt employers, workers, and regulators to reduce the risk of silicosis through effective exposure controls and regulatory interventions [58]. It was also observed that 33.3% of the mean samples analysed were above the occupational exposure limit of 0.1 mg/m3.
This current study adds a new perspective to the body of knowledge about respirable dust exposures in low-income countries. The dataset in this study can be input into a regional and, in future, a continental exposure/surveillance database for the region’s mining industry. Exposure surveillance databases are being utilised in countries such as the United States, Australia, and Europe to monitor exposure trends over time, as well as to track the use of exposure controls, including respiratory protective equipment [48,54,66,67]. While exposure to respirable dust may be decreasing over time in countries such as Australia, the situation surrounding actual exposure remains unclear, particularly in low-income countries. Low awareness levels further exacerbate the situation in these countries, increasing the risks associated with exposure to occupational health hazards [68] and a lag in workplace regulation and enforcement [27]. This highlights the importance and urgency of establishing an exposure surveillance database that will serve as a scientific tool to inform future epidemiological studies linking dust exposure to silicosis [53,67,68].

Limitations and Strengths of the Study

The limited resources allocated for the project resulted in a reduced number of mines included in the study compared to the total existing mining operations across the four participating countries. The results from this study only represent actual exposures recorded from the sampled mining operations and are not generalisable for the unsampled mines. The types of coal mined, rock quarried and soil type handled during the sampling were not recorded during the actual study, a limitation that affects discussions related to the expected respirable dust quartz load. Additional papers from the same dataset will be reported in future publications, covering work activities and job categories with high exposure, risk assessment, and currently implemented controls, as well as their effectiveness.
To our knowledge, this is the first study to address the research gap on worker exposure to crystalline silica among mine workers in four southern African countries. The study assessed workers’ exposure to respirable dust in various mining commodities, including artisanal small-scale mines. The findings of this study may serve as a basis for the adoption and implementation of international policies.

5. Conclusions

Mining workers are exposed to respirable dust and respirable crystalline silica dust above the recommended occupational exposure limits. These workers are at high risk of developing silicosis and any other occupational lung disease. The hazardous nature associated with mining operations persists in low-income countries, where workers are exposed to varying respirable and corresponding quartz dust fractions that exceed OELs for each mining activity type. The collected exposure data provides a baseline overview of exposure within the mining industry in the four SADC countries. This exposure dataset can be utilised to establish a regional exposure data surveillance system, enabling effective planning and control. The envisaged regional exposure surveillance data has the potential to provide a high-level overview of exposure extent or status, especially for countries with OHS regulatory shortcomings, as well as direct research focus areas and exposure prevention initiatives. Cross-border partnerships aimed at quantifying exposure, as conducted in this study, are vital for supporting decision-making in workplace interventions that aim to prevent the spread of TB and occupational lung disease, a significant public health concern. The study revealed that workers are exposed to quartz released during mining processes, which is a serious hazard due to its toxicity. This study concurs with other studies showing that silica quartz exposure is a common occupational risk in various mining settings, associated with occupational lung disease, such as silicosis and lung cancer [69,70]. The findings urgently call for enhanced monitoring and analysis using real-time technology, as well as strengthened compliance and control of sub-micron toxic respirable crystalline silica (quartz) dust. Future research should explore real-time sampling and analysis methodologies and test the efficacy of current controls for capturing sub-micron dust, which is the most toxic due to its ability to reach the alveolar regions of the lungs.

Author Contributions

Conceptualization, N.N.K., T.P.M., P.C.R. and M.D.M.; methodology, N.N.K. and M.D.M.; validation, P.C.R., T.P.M., M.D.M. and N.N.K.; formal analysis, O.R., D.M. and N.N.K.; writing—original draft preparation, N.N.K. and O.R.; writing—review and editing, D.M. and T.P.M.; visualisation, N.N.K.; supervision, P.C.R. and M.D.M.; project administration, N.N.K.; funding acquisition, N.N.K. and T.P.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded under the World Bank’s SATBHSS project grant numbers P155658 and P173228. No restrictions were placed on the research.

Institutional Review Board Statement

The study received ethical clearances from the Faculty of Health Sciences Research Ethics Committee, ethics number: NHREC Registration: REC-2859-2024. Furthermore, gatekeeper permission was granted by the mines management.

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

The data presented in this study are available in the paper and can also be obtained from the project lead and principal investigator (N.K.).

Acknowledgments

This work was performed in collaboration with several individuals and institutions. We are grateful to all staff participating in the SATBHSS project in four countries: Lesotho, Mozambique, Malawi, and Zambia.

Conflicts of Interest

Author Dingani Moyo was employed by the company Baines Occupational Health Services. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Safety 12 00058 g001
Figure 1. Presentation of the Study Sites (SADC countries).
Figure 1. Presentation of the Study Sites (SADC countries).
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Figure 2. Respirable dust concentration.
Figure 2. Respirable dust concentration.
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Figure 3. Quartz exposure concentration.
Figure 3. Quartz exposure concentration.
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Table 1. Descriptive statistics for mining operations included.
Table 1. Descriptive statistics for mining operations included.
Country Mine Scale *Type of MineCommodity MinedTotal Mineworkers
(Including Contractors)
Lesotho (N = 5)
Mine 1LargeSurfaceDiamonds 711
Mine 2LargeSurfaceDiamonds 1500
Mine 3MediumSurfaceAggregate230
Mine 4SmallSurfaceAggregate35
Mine 5SmallSurfaceAggregate64
Malawi (N = 5)
Mine 1LargeUndergroundCoal400
Mine 2MediumSurfaceAggregate100
Mine 3Medium SurfaceLimestone600
Mine 4Small SurfaceAggregate350
Mine 5Small SurfaceRose quarts25
Mozambique (N = 4)
Mine 1Large SurfaceCoal 1500
Mine 2Medium UndergroundRuby 144
Mine 3Large SurfaceQuarry 20
Mine 4Small SurfaceGold 1480
Zambia (N = 7)
Mine 1LargeUndergroundCopper2226
Mine 2Large SurfaceCopper2982
Mine 3Large SurfaceCoal 633
Mine 4Medium SurfaceLimestone760
Mine 5Medium UndergroundCoal 437
Mine 6Small SurfaceAggregate47
Mine 7Small SurfaceManganese150
* Large|total Workers > 500; Medium| total Workers > 100 and <500 Workers; Small|total Workers < 100.
Table 2. Overview of samples taken and compliance percentages.
Table 2. Overview of samples taken and compliance percentages.
Sample TypeTotal SamplesSamples Under OELSamples > OELSamples > 1/2 OEL
No.%No.%No.%
Respirable dust1191119387108
   ▪ Quartz11798221210
Respirable coal mine dust9490964455
   ▪ Quartz (coal mine dust)758019 2066
Quartz (quarries)137654772531410
Table 3. Combined statistical overview of respirable dust and quartz exposures across the four countries’ mines.
Table 3. Combined statistical overview of respirable dust and quartz exposures across the four countries’ mines.
CountryMine NameNumber of Samples
Collected		Contaminant TypeRangeGeometric MeanGeometric Standard
Deviation		MeanStandard DeviationMedianCoefficient of
Variation
(mg/m3)(mg/m3)(mg/m3)(mg/m3)(%)
LesothoMine 111: Quartz fraction0.007–1.7120.003771.250.003870.0009870.003625.5
: Respirable dust0.003–0.0060.1314.920.2840.3740.134132
Mine 29: Quartz fraction0.022–1.7120.003721.390.004010.002290.003357.1
: Respirable dust0.003–0.0140.2812.810.3970.410.3103
Mine 323: Quartz fraction0.020–1.4050.03624.180.08370.1040.0333124
: Respirable dust0.004–0.2960.1383.810.3260.4520.117138
Mine 419: Quartz fraction0.187–2.1840.2092.280.2720.1860.21468.4
: Respirable dust0.056–0.5390.7882.321.030.6990.86367.9
Mine 524: Quartz fraction0.139–2.1040.01862.310.02470.01890.019376.5
: Respirable dust0.005–0.0660.62.50.8320.6320.80575.9
MalawiMine 126: Quartz fraction0.065–6.7210.023.580.04310.05770.0217134
: Respirable dust0.005–0.2170.7022.951.211.480.736122
Mine 225: Quartz fraction0.252–10.6300.0252.460.3790.440.239116
: Respirable dust0.058–2.0041.133.032.062.590.97126
Mine 39: Quartz fraction0.147–0.5160.01133.360.02860.0490.0055171
: Respirable dust0.016–0.2790.6223.851.532.450.424160
Mine 410: Quartz fraction0.064–3.8470.02555.130.07970.1330.0292167
: Respirable dust0.006–0.4370.3153.370.6851.140.267167
Mine 520: Quartz fraction0.074–10.6230.04992.190.06990.07990.0595114
: Respirable dust0.005–0.1640.2391.540.260.1210.2546.5
MozambiqueMine 128: Quartz fraction0.005–1.4400.008352.760.01430.01630.0045114
: Respirable dust0.003–0.0600.1472.40.2260.2860.125126
Mine 230: Quartz fraction0.017–0.4990.007651.90.009480.006650.004970.1
: Respirable dust0.005–0.0230.1562.150.1930.110.18856.9
Mine 39: Quartz fraction0.090–7.3450.004731.050.004740.0002290.00484.84
: Respirable dust0.0043–0.0050.6543.731.472.070.496141
Mine 410: Quartz fraction0.022–4.0840.01062.70.01910.02780.00665146
: Respirable dust0.005–0.0930.1913.980.5761.240.162216
ZambiaMine 130: Quartz fraction0.0020–5.2410.885.421.761.461.5683
: Respirable dust0.0020–5.2410.885.421.761.461.5683%
Mine 230: Quartz fraction<0.0050.005 0.005 0.0050
: Respirable dust<0.0050.005 0.005 0.0050%
Mine 325: Quartz fraction0.005–1.80.0716.980.2960.4960.078171
: Respirable dust0.005–1.80.0716.980.2960.4960.078171%
Mine 420: Quartz fraction0.001–2.7390.3456.820.8210.7940.63797
: Respirable dust0.001–2.7390.3456.820.8210.7940.63797%
Mine 515: Quartz fraction<0.0050.005 0.005 0.0050
: Respirable dust<0.0050.005 0.005 0.0050%
Mine 610: Quartz fraction0.198–1.9280.7832.2210.06431.0164
: Respirable dust0.198–1.9280.7832.2210.06431.0164%
Mine 710: Quartz fraction<0.0050.005 0.005 0.0050
: Respirable dust<0.0050.005 0.005 0.0050%
mg/m3 milligram per cubic meter; % percent.
Table 4. Overview of respirable coal mine dust and quartz exposures in Malawi, Mozambique and Zambia.
Table 4. Overview of respirable coal mine dust and quartz exposures in Malawi, Mozambique and Zambia.
Country Mine NameContaminant TypeRange
(mg/m3)
MalawiMine 1: Respirable coal mine dust0.065–6.721
: Quartz fraction0.005–0.217
MozambiqueMine 1: Respirable coal mine dust<0.0001–1.440
: Quartz fraction0.003–0.060
ZambiaMine 3: Respirable coal mine dust<0.0001–1.754
: Quartz fraction0.005–1.621
Mine 5: Respirable coal mine dust<0.0001
: Quartz fraction<0.005
mg/m3 milligram per cubic meter; % percent.
Table 5. Overview of quartz exposure in quarries across the four countries.
Table 5. Overview of quartz exposure in quarries across the four countries.
Country Mine NameRangeGeometric MeanGeometric Standard
Deviation		MeanStandard DeviationMedianCoefficient of Variation
(mg/m3)(mg/m3)(mg/m3)(mg/m3)(%)
LesothoMine 30.004–0.2960.1383.810.3260.4520.117138
Mine 40.056–0.5390.7882.321.030.6990.86367.9
Mine 5<0.005–0.0660.62.50.8320.6320.80575.9
MalawiMine 20.06–21.133.032.062.590.97126
Mine 3<0.005–0.1640.6223.851.532.450.424160
Mine 40.006–0.4370.3153.370.6851.140.267167
Mine 50.016–0.2790.2391.540.260.1210.2546.5
MozambiqueMine 3<0.005–0.0100.1913.980.5761.240.162216
ZambiaMine 4<0.005–2.7390.3456.820.8210.7940.63797
Mine 60.198–1.9280.7832.2210.06431.0164
mg/m3 milligram per cubic meter; % percent.
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Khoza, N.N.; Rikhotso, O.; Mbonane, T.P.; Moyo, D.; Rathebe, P.C.; Masekameni, M.D. Workers’ Exposure to Respirable Dust and Quartz in the Southern African Large, Medium, Small and Artisanal Small-Scale Mining Industry: An Exploratory Study. Safety 2026, 12, 58. https://doi.org/10.3390/safety12030058

AMA Style

Khoza NN, Rikhotso O, Mbonane TP, Moyo D, Rathebe PC, Masekameni MD. Workers’ Exposure to Respirable Dust and Quartz in the Southern African Large, Medium, Small and Artisanal Small-Scale Mining Industry: An Exploratory Study. Safety. 2026; 12(3):58. https://doi.org/10.3390/safety12030058

Chicago/Turabian Style

Khoza, Norman Nkuzi, Oscar Rikhotso, Thokozane Patrick Mbonane, Dingani Moyo, Phoka Caiphus Rathebe, and Masilu Daniel Masekameni. 2026. "Workers’ Exposure to Respirable Dust and Quartz in the Southern African Large, Medium, Small and Artisanal Small-Scale Mining Industry: An Exploratory Study" Safety 12, no. 3: 58. https://doi.org/10.3390/safety12030058

APA Style

Khoza, N. N., Rikhotso, O., Mbonane, T. P., Moyo, D., Rathebe, P. C., & Masekameni, M. D. (2026). Workers’ Exposure to Respirable Dust and Quartz in the Southern African Large, Medium, Small and Artisanal Small-Scale Mining Industry: An Exploratory Study. Safety, 12(3), 58. https://doi.org/10.3390/safety12030058

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