Health Risk Assessment of Airborne PM2.5 Emissions in the Steve Tshwete Local Municipality, Mpumalanga, South Africa

Abstract

Air pollution is a significant global public health concern, causing 8.1 million deaths in 2021, and is the second-leading risk factor for mortality worldwide. The issue is particularly dire in developing countries, where socio-economic and environmental factors heighten the risk of exposure to harmful pollution levels. In 2019, air pollution was responsible for 7 million premature deaths, with 91% of these occurring in low- and middle-income countries. Fine particulate matter (PM2.5), a major element of ambient air pollution, is closely associated with cardiovascular, respiratory, and metabolic diseases. Exposure to PM2.5 raises the risk of death, especially from cardiopulmonary diseases and lung cancer, with each 10 μg/m³ rise in PM2.5 levels linked to an increase in mortality rates. In South Africa, a country heavily reliant on coal for energy, the health risks related to PM2.5 exposure are significant. Coal combustion accounts for over 90% of the nation's energy, making South Africa one of the top global contributors to coal-based electricity generation. This reliance has placed the country as the fourth highest in Africa for deaths related to PM2.5 exposure. Although efforts such as transitioning to renewable energy and implementing stricter emission standards have been made, progress has been slow. With limited research and monitoring, particularly in marginalized areas, the health impacts of air pollution remain under- explored. Despite the World Health Organization's recommendation of a yearly average PM2.5 level of 5 μg/m³, many urban areas, including Johannesburg and Cape Town, experience significantly higher concentrations. This thesis examines the health impacts of PM2.5 exposure in South Africa, focusing on vulnerable populations and the ongoing efforts to mitigate the public health risks of air pollution. Aim: The aim of this study is to assess the health risks caused by airborne PM2.5 exposure in the Steve Tshwete local municipality, Mpumalanga Province in South Africa. Methods: The study utilized a cross-sectional research design with secondary data from the South African Air Quality Information System (SAAQIS), collected over a 12-month period in 2022 through a stationary air quality monitoring station. The data was validated, with spike detection algorithms applied to remove outliers, and stored securely using Google Cloud Storage. Hourly averaged PM2.5 data was categorized by seasons (Summer, Autumn, Winter, Spring) and analyzed to calculate seasonal and daily averages. A health risk assessment was performed using the United States Environmental Protection Agency's (USEPA) framework, iv focusing on inhalation exposure for adults (65+) and children (6-12). Hazard Quotients (HQ) for PM2.5 were calculated, with a threshold of 1 indicating a negligible risk. A pairwise statistical analysis using a one-way Analysis of Variance (ANOVA) at a 95% confidence interval was conducted to determine significant differences in PM2.5 emissions between seasons. Results: The study analyzed seasonal variations in PM2.5 concentrations in Steve Tshwete, showing that environmental factors play a significant role in air quality. Winter had the highest PM2.5 levels (30.24 μg/m³), driven by heating emissions, temperature inversions, low rainfall (12.3 mm), and low humidity (59%), which limited secondary aerosol formation. Spring saw a decrease in PM2.5 (19.14 μg/m³) due to higher temperatures (18.17°C), increased rainfall (62 mm), and higher humidity (70.67%), promoting pollutant dispersion and washout, though agricultural activities may still influence levels. Summer recorded the lowest concentrations (10.4 μg/m³) because of high rainfall (114.33 mm), higher temperatures (21.1°C), and humidity (79.33%), enhancing pollutant dispersion. Autumn showed a moderate increase in PM2.5 (15.78 μg/m³) due to decreased rainfall (53 mm) and cooler temperatures (17.6°C), leading to more stable conditions that hindered pollutant dispersion. The study found significantly elevated cancer risk (CR) values associated with long-term exposure to PM2.5 concentrations averaging 14 μg/m³. The CR for children was 6.9 × 10⁻³ (equivalent to 6.9 in 1,000), while for the elderly it reached 2.1 × 10⁻² (or 2.1 in 100). These values far exceed the typical regulatory thresholds for acceptable cancer risk, which range from 1 × 10⁻⁶ to 1 × 10⁻⁴, indicating an unacceptably high potential for lifetime cancer development, particularly among older individuals. Non-carcinogenic health risks were also found to be concerning. The Hazard Quotient (HQ) values were 2.014 for children and 2.46 for the elderly, both exceeding the safety threshold of 1. This indicates that the exposed populations are subject to pollutant levels more than twice the reference concentration considered safe, suggesting a heightened likelihood of adverse health effects beyond cancer. These may include respiratory, cardiovascular, or neurological conditions, particularly in sensitive groups. Conclusion: This study highlights air quality concerns in Steve Tshwete, where PM2.5 levels often exceed World Health Organization (WHO) and National Ambient Air Quality Standards (NAAQS) guidelines, posing health risks. Seasonal trends show higher PM2.5 in July, linked to dry conditions and agricultural burning, while lower levels are observed in January due to rainfall and reduced activity. Diurnal patterns reveal peak pollution during the day, v emphasizing the need for targeted interventions. Wind pattern analysis and continuous monitoring are essential for identifying pollution sources. Although health risks are within acceptable limits, adults face higher risks due to longer exposure, while children remain more vulnerable. Stricter regulations on agricultural burning, industrial monitoring, and public awareness campaigns are necessary to mitigate these risks, especially during high-risk months like July.