School of Public Health (ETDs)
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Item Indoor/outdoor PM4 (respirable dust) and respirable crystalline silica source tracking in households located in close proximity to gold mine tailing dumps(University of the Witwatersrand, Johannesburg, 2023-10) Makhubele, Nkateko Rawendar; Mizan, Gabriel; Manganyi, Jeanneth; Masekameni, Masilu DanielBackground: Particulate matter (PM) is a major contributor to air pollution in indoor and outdoor environmental spaces. Exposure to respirable dust (PM4) and respirable crystalline silica (RCS) indoor and outdoor in communities located in close proximity to gold mine tailings dumps in South Africa has not yet been determined. Aim: The aim of this study was to investigate the concentration of RCS and PM4 mass in samples measured indoor and outdoor of the nine (9) selected households located in close proximity to a gold mine tailings dumps. Methodology: Sampling locations were separated according to grids, based on the distance from the mine tailings dumps. Three different grids were determined as follows: A (<500m from the dump), B (>500m<1km) and C (1km – 3 km). Three households were selected from each grid zone to measure indoor and outdoor PM4 samples continuously over a 24-hour period using GilAir constant sampling pumps calibrated at the flowrate of 2.2 L/min in both the dry and wet seasons. PM4 samples were collected on a 37mm polyvinyl chloride (PVC) filter with a pore size of 0.8, which was assembled on the Higgin Dewell cyclones fitted with a filter pad of the same pore size. PM4 sample filters were gravimetrically weighed before and after sampling to determine the mass concentration of PM4. The respirable crystalline silica in PM4 samples were analysed by an X-ray diffraction method by South African National Accreditation System (SANAS) accredited laboratory of the National Institute for Occupational Health (NIOH). Samples were collected during the dry and wet seasons in the Riverlea community, Johannesburg. Results: During the wet and dry seasons, the mean indoor and outdoor PM4 mass concentration ranged from 0.02±0.01 µg/m3 to 2.26±0.02 µg/m3, respectively. The dry season mean PM4 mass concentrations were higher than the wet season PM4 mass concentrations in all zones. The pairwise comparison of PM4 mass concentration for dry and wet season revealed no statistically significance difference (p<0.05) at 95% confidence interval. Results presented in Figure 5 depicts the mean indoor PM4 mass concentration distribution for the dry season. The zone with the highest mean indoor PM4 mass concentration was zone A, followed by zone B. Since the mean outdoor PM4 concentration in zone C was the lowest, this suggests that the mine tailings dumps were the primary source of PM. The dry season mean indoor/outdoor ratio was greater than one across all zones; indicating that indoor activities were the primary source of PM. In both seasons, the mean indoor and outdoor percentages of crystalline silica ranged from 0.08±0.01% to 0.08±0.01%. The mean indoor and outdoor 24hr RCS concentrations in both seasons were below the California Office of Environmental Health Hazard Assessment (OEHHA) defined 24hr ambient exposure threshold of 3µg/m3. Recommendations: The results of this study suggest that nearby mine tailings dumps may be the primary source of PM in the indoor and outdoor environments; however the strength of this source in comparison to other sources remains unknown. Therefore, it is recommended that further studies focusing on source apportionment be carried out to determine the relative contribution of the mine tailings dust to the overall PM load in the environment. Although the difference was not statistically significant, indoor and outdoor PM4 concentrations were greater in Zones A&B, with the lowest PM4 concentrations in Zone C. The I/O ratio indicated that there was contribution of PM from outdoor. It is also recommended that further studies be conducted, with focus on monitoring PM4 over a 30 days period, to determine the level of free crystalline silica that may be present in PM4 mass concentrations. Conclusion: In the South African context, studies that focus on the investigation of indoor and outdoor PM4 concentrations in households located in close proximity to gold mine tailings are limited. The findings of this study can be used to provide valuable information on the indoor and outdoor PM4 concentrations, which can be used in modelling exposure and conducting probabilistic health risk assessment. High dust levels are related with dry season weather conditions due to strong wind conditions. Therefore, the PM4 mass concentrations in all zones were higher during the dry season than during wet season. Since the mean outdoor PM4 concentration in zone C was the lowest, this suggests that the mine tailings dumps were the primary source of PM.Item Efficacy of water suppression method for controlling the emissions of submicron particles at a quarry, Boksburg, South Africa(2024) Mkwanazi, D. D.Background: Respiratory diseases has contributed 70% to worldwide occupational disease mortality in all industrial sectors since over a decade ago. Pneumoconioses occur as a result of accumulation of dust in the lungs. Silicosis, one of the most common forms of pneumoconioses, presents in three different forms namely acute, accelerated, and chronic silicosis. Quarrying and open cast mining are responsible for different workplace hazards including noise, trauma, vibration, ultraviolet radiation, and dust exposure, which may cause silicosis. Lung deposition of particulate matter depend on the particulate matter surface characteristics, aerodynamic size, and weight. Quarrying and stone crushing activities are associated with high levels of crystalline silica release. Water suppression has been proven to effectively control dust in mining and construction industries, but not enough attention has been paid on effects of water suppression on fine particulate matter. Purpose: To evaluate efficacy of water suppression as a dust control measure for submicron particles for the primary, secondary and tertiary treatment processes during the production of stone aggregates in a quarry. Methods: In this cross-sectional study data was collected using a Nanozen dust sampling device to monitor dust emissions in 0.300µm to 10.658µm bin sizes across 4 different sampling points namely primary, secondary, tertiary treatment area, and office complex at a quarry in Boksburg, South Africa. In the primary treatment area big rocks are crushed into 150mm smaller rock without dust suppression, the secondary area breaks them further into 57mm stones with water supperssion applied, and tertiary breaks them into 19mm and smaller stone products under further water suppression conditions. Primary treatment area and office complex were sampled as dry areas, while secondary and tertiary treatment areas were sampled as water suppression areas. Data was analysed based on mass and number concentrations for different bin sizes, and comparisons were made between dry and wet areas. The effect of water treatment (suppression) on submicron bin ranges (0.300-0.915µm) in terms of mass concentration and number concentration was analysed to determine its efficacy in reducing dust emissions in this range. Results: The total average mass concentration of 460.2 µg/m3 (±486.3) was emitted from the primary area without dust suppression with average of 2.22E+08 (±136958.7) number concentration. This was reduced to 6.02µg/m3 and 60.9 million (±552879) mass and number concentration respectively in secondary treatment area with water suppression. In tertiary area emissions were 10.52µg/m3 and 54.8 million particles/cm3 (±828126) respectively for mass and number concentrations following further water suppression, while in office area (no water suppression) 6.07µg/m3 and 44.4 million/cm3 mass and number concentrations were recorded respectively. Conclusions & Recommendations: Data showed reduction of emissions between primary and secondary area by 98.7% (mass concentration) and 72.5% (number concentration). Further treatment in tertiary treatment showed a further decrease in total average number concentration compared to secondary treatment. Emissions at the office block as a control site were consistent with emissions from secondary and tertiary treatment areas, demonstrating possible dispersion by wind. Water suppression was demonstrated to be effective against particle bin sizes larger than 1 micron, with progressively less effect on submicron particles as they became smaller. More research is recommended on suppression of submicron dust particulate matter emission and consideration of number concentration as a key dose matrix to determine exposure.Item Risk assessment of exposure to indoor particulate matter (PM2.5) near a Ferro-manganese smelter - Meyerton, Gauteng Province(2024) Khoza, Goodwill Jopa ZimakaziBackground- Globally, over 90% of the populace have no access to clean air. Exposure to airborne contaminants is associated with adverse health risks. Studies have reported on direct correlation between industrialised settings with increased incidence of air pollution associated illnesses. Chronic exposure to PM2.5 is linked to cardiovascular and respiratory illnesses. Exposure to particulate matter (PM) in residential settings has been studied in many big mega-cities globally. However, fewer studies were achieved in low-income settings and South Africa is no exception. Exposure and risk assessments research emanate from occupational settings with less emphasis on residential settings. Studies assessing the risk of exposure to PM2.5 in residential settings are quite limited. This provides understanding a research knowledge gap in South African low-income societies. Purpose- The purpose of the study is to determine indoor PM2.5 chronic daily intake to estimate the non-carcinogenic risk in communities living adjacent industrial PM emitting sources. Methods- Secondary data from the main study titled “Motor and cognitive health outcomes in a manganese-exposed African community” (HREC clearance certificate no. M121117), which was conducted during the period of 2019/20 was used to assess the risk of exposure to indoor PM2.5. The secondary data used in this study was collected during winter season, and PM2.5 was sampled using a gravimetric technique over a period of seven days. Particles were drawn into the sampling head by a Gillian Gil-Air 300plus pump (Sensidyne, St Petersburg FL, USA) which was connected using a teflon tubing. A PM2.5 Cyclone D32 with a cut-off point of PM2.5 attached to the sampling head to isolate larger particles from entering the inlet of the cassette. The pump was calibrated and operated at a continuous flow rate of 2.75 L/minute over a seven-days period. Pre-and-post-weighing of filters was performed to derive the final mass in a controlled laboratory environment using a micro-balance scale (modelCPA225D, Sartorius, AG, Göttingen, Germany). The pre-weight (mass) consisted only of the mass of a filter while the post mass consisted of particulate and filters. Results- The particulate matter (PM) mass concentration for New Sicelo, Old Sicelo and Noldick was found to be 0.0125 mg/m³, 0.0115 mg/m³ and 0.0061 mg/m³ respectively. The indoor PM mass concentrations for both New and Old Sicelo was found to be doubled as compared to that of Noldick’s. An increased PM mass concentrations for the New and Old Sicelo areas implied an unavoidable risk of PM exposure to the population of New and Old Sicelo, respectively. Flowing from the identified risk; sustainable mitigation plans are fundamental to curb the risk of generational poisonous exposures which will rampantly lower the populace life expectancy tremendously if not proactively addressed especially at source. Daily intake (DI) fractions for females and males were 22.98 m3 /kg/day and 17 m3 /kg/day for all three locations, respectively. Higher DI for females corroborate and support preceding studies’ findings that women spent 80% of their instances indoors. The chronic daily intake (CDI) for males at New Sicelo, Old Sicelo and Noldick were 0.21 mg/kg/day, 0.20 mg/kg/day and 0.10 mg/kg/day and females at New Sicelo, Old Sicelo and Noldick had been 0.29 mg/kg/day, 0.26 mg/kg/day and 0.14 mg/kg/day, respectively. The difference in CDI values for females and males tells how women are over exposed compared to men. Hazard quotients (HQ) for females throughout the three locations were 261, 240 and 127 respectively while males were 193, 178 and 94. A hazard quotients (HQ) measurement means women are over exposed compared to men. H>1 for women means that non-carcinogenic impact has been surpassed and cancer is high while men with H>1 for women means that non-carcinogenic impact has been surpassed and cancer is high while men with H>1 have a negligible cancer risk in the tree areas (Old and New Sicelo, Noldick). The findings from the study positively affirm the following aspects; i) characterization of the PM mass concentration from the three locations and, ii) how impactful is the PM exposure levels to the population health status which in turn influence the concept of exposure assessment. To support the exposure assessment process; a systematic review was conducted on time-activity patterns, the demographic data for risk assessment input variables were noted and the estimation non-carcinogenic health risk of exposure to indoor PM concentration especially for the community of Meyerton. Conclusion -The study determined indoor PM2.5 chronic daily intake to estimate the non-carcinogenic risk in communities living adjacent to industrial PM emitting sources. The study may want to aid in perception of exposure and development of abatement measures to decrease exposure to PM2.5 sources and assists in performing exposure assessments.