How Clean is Our Air in KwaDukuza / iLembe? – A Preliminary 3 Year Trend Analysis

Summary

Communities Against Pollution’s Citizen Science Project carried out a preliminary analysis to characterise the ambient air quality and establish an empirical baseline for the KwaDukuza / iLembe districts of KwaZulu-Natal, South Africa. These districts are home to more than 780,000 inhabitants and devoid of government air quality monitoring stations. The study analysed the seasonal variations of PM_2.5 levels between 2023 and 2025, the impact of weather conditions, the seasonal agricultural crop residue burning patterns, and quantified the emissions of those burning practices. The air quality data was translated into infometrics that hopefully resonate with the public and lead to an improved understanding of the air quality. The study confirmed: there are seasonal variations in PM_2.5 levels, that the levels peak in winter, and these elevated levels are linked to crop residue burning and weather conditions. The study went on to suggest that without intervention, the health risks associated with agricultural burning and industrial emissions pose a serious threat to the environment, economic stability, and quality of life.

Introduction

Air pollution is now ranked as the second leading risk factor for death. ^[[i]] Long-term exposure to polluted air causes adverse health effects, such as weakening the human immune system, leading to respiratory diseases, and premature death. ^[[ii]] Furthermore, in the past decade, research has linked air pollution to negative economic impacts, including lost production and productivity. ^{[[iii]] [[iv]]}

As in other countries, coal-fired power plants, motor vehicles, industry, the use of domestic solid fuels for cooking and heating, waste incineration, and open biomass burning make up the main sources of air pollution emissions in South Africa.

Air pollutants fall into four main categories: ^[[v]] heavy metals, fine and coarse particulate matter, and trace gases. We can further subdivide these pollutants into primary and secondary categories. Primary pollutants include all forms of particulate matter (PM), volatile organic compounds (VOC), carbon monoxide (CO), and heavy metal emissions, such as lead, mercury, and cadmium, while secondary pollutants include surface-level ozone (O₃), nitrogen oxides (NO_x) and nitrous oxide (N₂O). One of the most harmful pollutants is PM_2.5 (particulate matter with a diameter of 2.5 micrometres (μg) or smaller), because these fine particles can penetrate deep into the lungs and have been linked to cardiovascular and respiratory organ damage, leading to cause-specific premature deaths. ^[[vi]] The duration of exposure, the concentration of pollutants, and an individual’s immunity levels significantly influence their respective health outcomes. Estimates suggest that PM_2.5 exposure contributed to 42,000 deaths in South Africa in 2023. ^[3]

This study focused on the questions: (a) Did PM_2.5 levels fluctuate on a seasonal basis between 2023 and 2025? (b) Is there a relationship between PM_2.5 level fluctuation and weather conditions and/or seasonal agricultural crop residue burning practices? (c) Can we quantify the emissions from agricultural crop residue burning practices? (d) Can we present the data in a format that resonates with the public and gives them a better understanding of the extent of the air pollution problem?

The main objectives of the Communities Against Pollution (CAP) citizen science study were to characterise the ambient air quality and establish an empirical baseline for the KwaDukuza / iLembe districts of KwaZulu-Natal, South Africa.

Materials and Methods 

Study Area Description

KwaDukuza / iLembe in KwaZulu-Natal, is a district devoid of government air quality monitors and home to over 780,000 residents. The district is located between Richards Bay and Durban, two major port cities, in the rapidly growing economic corridor. It is a well-established and popular tourism destination. It has numerous well-established residential estates and many others in development. KwaDukuza is considered one of South Africa’s leading growth nodes. Manufacturing, finance/business services, wholesale/retail trade, and the long-standing industrial sugar and paper milling operations are the main drivers of the district’s economy. Commercial farming, primarily under privately owned sugar cane, occupies large areas of land along the coast, while the hinterland is primarily a rural area with impoverished black communities that rely on subsistence farming for their livelihoods.

The N2 national highway transverses the study area and carries significant volumes of traffic. Areas located between 100 and 500 meters from major roads, act as significant pollution sinks for both exhaust emissions (such as soot and organics) and non-exhaust emissions (from brake and tyre wear, and road dust), generating considerably higher PM concentrations than their surroundings. ^[[i]] To ensure that the data represent ambient air conditions that are not directly affected by major roads, we selected monitors at least 1 km from the N2 and R102 motorways.

Of the eleven available stations, we selected two, CAP / PLE west of the N2 and CAP / ECE east of the N2 (marked with red stars Fig 1 below). These locations were specifically chosen because they offered ambient air conditions free from direct influence by industry, traffic, or other common sources of air pollution. It is worth noting that the CAP network has also strategically placed some air quality monitors in locations designed to record specific emissions, such as those from waste burning near informal settlements.

Fig 1 AQ Monitors CAP / PLE and CAP / ECE (Red Stars)

Air Pollution and Meteorological Data

The study accessed data from the CAP’s independent air quality monitoring network, which includes several air quality monitors across KwaZulu-Natal, Gauteng, Western Cape, and Mauritius. We downloaded data in Comma Separated Version (CSV) format for the two selected monitors in KwaDukuza, KwaZulu Natal: CAP / PLE and CAP / ECE. These datasets cover the period from January 2023 to February 2026 and are available in different temporal resolutions. The downloaded information included measurements of PM_2.5 and PM₁₀, along with meteorological variables such as ambient temperature and relative humidity.

Before proceeding with the analysis, the data underwent quality checks, where gaps and outliers were identified and removed. Furthermore, a correction algorithm developed by the US Environmental Protection Agency for low-cost monitors was applied to mitigate the overestimation of readings, particularly under conditions of high pollution or high humidity.

The predominant weather systems in Southern Africa during the winter months are subtropical anticyclones (highs) that shift towards the equator. These, combined with semi-permanent upper-air high pressure, typically result in dry and stable weather across most of the region from May to August. These meteorological conditions often form subsidence inversions, which essentially trap air pollutants and cause haze at several hotspots across various regions. ^[[i]]

We used the South African Sugarcane Research Institute’s metrological data for the Gledhow Mill as it is located closest to the CAP / PLE and CAP / ECE monitors. Fig 2 below shows the monthly rainfall recorded at the mill from 2023 to 2025. ^[[i]]

Fig 2 Monthly Rainfall Gledhow Mill

The total rainfall recorded for 2023, 2024, and 2025 was 1,055.10mm, 834.50mm and 1,097.50mm respectively, with 2025 being the wettest year. We also considered the monthly Mean Temperature, Mean Relative Humidity, and Wind Run Reports, with 2024 recording the highest wind runs.

Burn Emissions Analysis

Agricultural crop residue burning is a common global practice, offering an economical and efficient way to manage biomass residue. The process facilitates harvesting and planting, while also aiding pest and weed control. The crop residue burning in KwaZulu-Natal occurs mainly from Apr to Oct.

Over the past few decades, researchers have amassed a substantial body of information on biomass burning emissions, primarily through the efforts of the International Geosphere-Biosphere Programme and International Global Atmospheric Chemistry. This extensive research provides detailed data crucial for estimating fire emissions. To calculate emissions from agricultural crop residue burning, we applied emission factors to the historical average yield of sugarcane processed at three local sugar mills: Maidstone, Gledhow, and Darnall. Our calculations utilised the following equation: Emissions (E) = Area burnt (A) [hectares (ha)] × Fuel loading or biomass per hectare (F) [kilograms per hectare] × Combustion fraction of biomass consumed by fire (C) × Emission factor (e) [grams per kilogram], which represents the mass of PM_2.5 and another compounds emitted per unit of biomass burned.

Tangible Health Metric

Air pollution includes fine particulate matter, PM_2.5, which, like tobacco smoke, can penetrate deeply into the lungs. Researchers at Berkeley Earth ^[[i]] developed a tool that translates fine particulate PM_2.5 concentrations in the air into an equivalent number of cigarettes smoked daily. It converts the abstract μg/m³ number into a tangible health metric that resonates with the public and in concepts that most people can easily recognise.

Equation applied: Daily average PM_2.5 concentration (μg/m³) / 22 = Cigarettes per day. Put another way, 1 cigarette is equivalent to PM_2.5 air pollution at a level of 22 μg/m³ for 24 hours.

Computations and Results

Fig 3 below shows a series of plots for PM_2.5 pollutants at CAP / PLE and CAP / ECE for the period Jan 2025 to Dec 2025. The recorded annual averages for 2025 were 11.30 µm and 10.70 µm respectively.  The two monitors are approximately 4.75 km apart, CAP / PLE is located west and CAP / ECE is located east of the N2. The data from the two monitors show strong similarities. The small variation in the mean could be due to the local hyper-local microclimate.  CAP / ECE is located 1.6 km from the high-water mark at an elevation of 96 m above sea level on the primary coastal dune and CAP / PLE is located 3.9 km from the high-water mark at an elevation of 43 m above sea level in a valley behind the primary dune. Note, we could only compare the two monitors for 2025, because of the dates of their installation, the CAP and PLE monitor was installed in Mar 2023 and the CAP and ECE monitor in Dec 2024.

Fig 3 CAP / PLE and CAP / ECE for the period Jan 2025 to Dec 2025

Fig 4 below shows a series of plots for PM_2.5 pollutants at CAP / PLE for the period Jan 2023 to Dec 2025. The recorded annual average for 2023, 2024, and 2025 was 17.40 µm, 16.8 µm, and 11.20 µm respectively.  By contrast the WHO recommended guideline annual average is 5 µm. ^[[i]]

Fig 4. CAP / PLE for the period Jan 2023 to Dec 2025

Fig 5 below shows a series of plots for PM_2.5 pollutants at CAP / PLE focusing on the winter months 2023, 2024, and 2025.

Fig 5 CAP / PLE winter months 2023, 2024, and 2025.

The winter averages, shown in Fig 5, for 2023, 2024, and 2025 were 28.00 µm, 32.00 µm, and 20.80 µm respectively.  By contrast the WHO recommended guideline annual average is 5 µm. This equates to 5.6, 6.4, and 4.16 times the annual WHO Guideline, respectively. The WHO recommended guideline 24-hour average is 15 µm, the level of pollution at this site exceeded the recommended WHO level for the entire 276 days (Jun to Aug x 3).

We took a closer look at diurnal patterns for Jun through to Aug, and many days show patterns of elevated PM_2.5 levels early in morning or late at night, e.g. Fig 6. below, the times when elevated levels were observed, which is consistent with the South African Sugarcane Research Institute’s (SASRI) guidelines for burning sugarcane, aimed at avoiding high daytime temperatures and windy conditions that create runaway fire risks.

Fig 6 24-hours 28 Jul 205 showing elevated PM_2.5 pattern

Fig 7 below shows a series of plots for PM_2.5 pollutants at CAP / PLE focusing on the summer months 2023, 2024, and 2025. The recorded summer averages for 2023, 2024, and 2025 was 6.70 µm, 6.5 µm, and 5.10 µm respectively. The ambient air quality for the summer months almost falls within the WHO recommended guideline annual average is 5 µm and therefore brings down the overall average.

Fig 7 CAP / PLE summer months 2023, 2024, and 2025.

Estimation of Emissions from Agricultural Crop Residue Burning

The study area is situated in a semi-rural area where agricultural activities play a significant role in the local economy. The primary crop farmed is sugarcane and seasonal agricultural crop residue burning is widely practiced, as a quick and low-cost method for harvesting and clearing fields between planting cycles.

It is well documented that agricultural crop residue burning releases numerous other pollutants, such as greenhouse gases (GHG), CO₂, N₂O, CH₄, and PM₁₀, other gases like carbon monoxide (CO), sulphur oxides (SO_x) nitrogen oxides (NO_x), and may include up to 18 polycyclic aromatic hydrocarbons and 37 volatile organic compounds, including the compounds found in pesticides, herbicides, and fungicides used by the agricultural industry. ^[[i]]

The 2023 – 2024 season saw a total of 15,231,000 tonnes of sugar cane being processing by all the sugar mills in KwaZulu-Natal, which we estimate corresponds to approximately 205,674 hectares of harvested cane. The two mills at Maidstone and Gledhow, in the study area, processed 2,799,916 tonnes of cane, equivalent to approximately 37,809 hectares of harvested cane. ^{[[ii]]  [[iii]]}

Fig 3 above shows that there is a sharp increase in air pollution between April and September, which coincides with the time of the harvest and burning of crop residues. To quantify these emissions, we estimated the number of hectares of sugarcane needed to reach the values crushed at the mills. District Assumptions see Fig 8 below.

Fig 8 Study Area’s Harvested Cane

Using the harvest figure of 37,809.08 ha in Fig 8 we computed the primary PM_2.5 emissions using an equation E = A F C e, in this equation, E is the emission of PM_2.5 and other compounds, A is the burnt area [hectares (ha)], F is the fuel loading or the biomass per hectare (kilograms per hectare), C is the fraction of biomass consumed by the fire (unitless), and e is the emission factor (grams per kilogram), which is the mass of PM_2.5 and other compounds emitted from burning a unit of biomass. A previous work estimated the fuel loading at 10,648 kg/ha (Range 8,967 to 15,692 kg/ha), a combustion fraction of 0.65, and the emission factor for primary PM_2.5 4.35 g/kg (Range 3.9 to 4.99 g/kg). ^[[i]

Fig 9 Study Area’s Estimated Emissions

The emission calculations in Fig. 9 show the values per hectare of PM_2.5, CO₂, SO₂, PM₁₀, CH₄, and NO₂ on the first row and the overall emissions for the study area in the second row.

We also calculated the emissions from sugarcane industry throughout KwaZulu-Natal 2023/2024, season and we found that the total emissions were approximately 2.70 million tonnes of air pollution. No data was available for stack emissions from the local sugar mills, so we could not include it in this study.

Health Metrics

Although graphs and statistics are useful communication tools, data is often quoted out of context, can lead to incorrect conclusions and confuse some people due to their limited data literacy. We felt it was necessary to transform some of the data into language that resonates with the public and makes it easier to visualise.

Fig 5 above shows the air pollution levels average for the 92 days of the winter months 2023, 2024, and 2025 at 28.00 µm, 32.00 µm, and 20.80 µm respectively.

By applying the Berkeley Earth equation, the daily average PM_2.5 concentration (μg/m³) divided by 22 = the equivalent number of cigarettes “smoked” per day, we computed how may cigarettes each person in the study area “smoked”.

Everyone in the study area unwittingly smoked 117 cigarettes (1.27 per day) in the 2023 winter months, 134 cigarettes (1.45 per day) in the 2024 winter months, and 87 cigarettes (0.95 per day) in 2025 the winter months.

As there was a substantial decrease in the number of cigarettes smoked, we examined whether there was any correlation between weather conditions and the decrease in the number of cigarettes in 2025, and it was noted that 2025 recorded the highest rainfall.

Correlation – PM_2.5 levels and Weather

Fig. 10 overleaf, illustrates the statistical relationship where one variable (rainfall) rises while another (PM_2.5) falls.

By examining the rainfall and PM_2.5 data, we discovered that there are strong negative Pearson’s correlations of r = -0.8444 and r = -0.8375 for CAP / PLE and CAP / ECE, respectively.

Fig 10 statistical relationship Rainfall and PM_2.5

The R² (coefficient of determination) R² = 0.7130 and R² = 0.7015 for CAP / PLE and CAP / ECE, respectively, further indicating a strong, relationship between the rainfall and PM_2.5 variables.

These findings are in line with other studies ^[[i]] which show that rain lowers PM_2.5 levels though the process of washout or scavenging, where falling raindrops collide with and capture airborne particles, dragging them to the ground. This process acts as a natural scrubber, reducing aerosol concentrations, soot, and smoke particles.

Discussion

The government’s failure to provide air quality monitoring services in the area was the catalyst for the study. CAP in collaboration with some of the affected communities identified several air pollution hotspots and together they are documenting their exposure to these emissions. The study measured and assessed the ambient air quality at two sites, CAP / PLE and CAP / ECE, with a focus on PM_2.5 levels. This research is part of an ongoing community science project, and it is hoped that our data will help the communities identify the causes of local air pollution.

Results showed elevated ambient PM_2.5 concentrations during the winter seasons when the burring of agricultural crop residue occurs, reaffirming findings of other studies. ^{[[i]] [[ii]]} The winter averages for 2023, 2024, and 2025 were 28.00 µm, 32.00 µm, and 20.80 µm respectively. The concentrations measured over 92 days each season were well above the WHO recommended annual concentrations of 15 µm.

Furthermore, the highest 24-hour average level of PM_2.5 peaked at 95.23 μg/m³. According to the South African Air Quality Standard, ^[[i]] this level is 2.38 times the maximum 24-hour average exposure. Those standards also state that 24-hour average exposures should not exceed 40 µg/m³ more than four times per annum; in 2024 the 24-hour average exposure limit was exceeded 16 times, which is 4 times the maximum allowable.

We considered various factors that could contribute to the increase in ambient concentrations of PM_2.5 in the study area. Generally, the key sources of pollution include manufacturing industries, motor vehicles, and agricultural activities. However, for this study, we selected monitors that were less likely to measure emissions from manufacturing industries and motor vehicles.

Some of the factors that may contribute to the elevated ambient particulate matter concentrations include the utilisation of solid fuels to warm low-income homes during winter. Residents often use solid fuels like wood and coal for heating because they are cheap and easily accessible, and these fuels are likely to be a source of residential emissions. Another possible source is open waste burning within informal settlement environments, which contaminates the immediate near-surface environment. The choice of monitors should have largely eliminated these factors.

A significant factor is that farmers in the study area commonly burn their agricultural crop residues from April to October. The study’s trend analysis shows elevated levels from April to September with peaks from June to August. Which leads us to conclude that the most likely cause of the elevated PM_2.5 levels during this period is the agricultural burning practice. Crop residue burning regularly exceeds the South African Air Quality Standard maximum 24-hour average exposure levels. This practice adds a substantial air pollution load to the ambient air in the study area and directly impacts on human health.

Air pollutants emitted into the atmosphere may travel distances ranging from several metres to thousands of kilometres. ^[[ii]] Given that sugar farming contributes a significant amount of air pollution per season, it is reasonable to believe that air pollutant drift from other sugar growing districts may also impact the study area, depending on the wind direction and other meteorological conditions.

Meteorological conditions significantly influence PM_2.5 levels and inversion layers are common over the study area during winter (June and July). The calm conditions which accompany these inversion layers result in low dispersion rates, which raise near-surface concentrations of PM and other air pollutants because they linger for a considerable time.

While not covered in this study, it is important to note that the combustion of bagasse and fossil fuels at sugar mills produces several hazardous pollutants, such as PM, SO₂, and NOₓ. These emissions also pose a threat to public health and contribute to global warming. Long-term exposure to these pollutants has been associated with an increase in chronic cardiovascular and respiratory diseases and can exacerbate neurological disorders. ^[[iii]]

By applying the equation E = A F C e, the study computed the estimated air pollution emissions from the burning of agricultural crop residue based on sugar production figures during the 2023/2024 seasons at the KwaZulu-Natal sugar mills. We estimated that the sugar industry contributes at least 2.27 million tonnes of air pollution per annum. We also estimated that the two mills in the study area produce 417,033 tonnes of air pollution per annum.

The PM emission estimates in the Fig. 7 above only account for primary PM_2.5; however, secondary PM_2.5 also occurs within the smoke plumes and further degrades air quality. Studies have found that total PM_2.5 can be as high as seven times the primary PM_2.5 found in smoke from agricultural crop fires after several hours of aging. For this study, we considered a 3-fold value. This means that total secondary PM_2.5 could reach 18,577 tonnes for the industry, pushing total emissions to 2.29 million tonnes. Secondary PM_2.5 emissions added a further 3,415 tonnes in the study area, pushing total emissions to 420,448 tonnes. Moving this tonnage would require more than 14,000 30-ton pantechnicon trucks, the equivalent of a line of back-to-back pantechnicons all the way from Ballito to Richards Bay and back, (approximately 252km).

Numerous studies show that respirable PM_2.5 particles, pose a considerable risk to human health, with some research demonstrating that the health of workers and communities adjacent to sugar cane plantations are particularly affected. ^[[i]] We have shown that workers and communities in the study area are exposed to thousands of tonnes of PM_2.5 from agricultural crop residue burning each season. The acute short-term inhalation of pollutants from this residue burning can induce lung function challenges that can exacerbate conditions such as ischaemic heart disease and asthma.

Most gaseous pollutants are invisible to humans, and individual PM particles are so small that we can hardly see them with the naked eye, but collectively they create the brown smudge and haze we see on the horizon in winter in the study area.

Research and public awareness efforts commonly use key comparisons, such as equating pollution exposure to smoking, measuring impacts on life expectancy, and using visual analogies. To make the data more relatable we selected comparisons that would translate complex environmental data into everyday concepts to highlight the severity of poor air quality.

People generally accept that smoking is bad for their health. Therefore, a comparison between air pollution and smoking helps us understand the potential harm that exposure to poor air quality can cause. But unlike cigarettes, air pollution is almost impossible to avoid.

In the winter months of 2023, 2024, and 2025, we estimate that everyone in the study area unwittingly “smoked” 117 cigarettes (1.27 per day), 134 cigarettes (1.45 per day), and 87 cigarettes (0.95 per day), respectively.

The annual average PM_2.5 exposures translates to everyone in the study area unknowingly “smoking” 289 cigarettes (0.79 per day) in 2023, 279 cigarettes (0.76 per day) in 2024, and 186 cigarettes (0.51 per day) in 2025.

Conclusion

The study showed that: (a) there were seasonal variations for PM_2.5, levels between 2023 and 2025, (b) agricultural crop residue burning practices and meteorological factors influenced ambient pollutant concentrations, (c) agricultural crop residue burn emissions can be quantified and they add approximately 420,448 tonnes per annum of air pollution emissions to the study area, (d) Comparisons between air pollution exposure and smoking, effects on life expectancy, and visual analogies are generally used in research and public awareness campaigns. We selected the smoking analogy because it is a more tangible health metric within our communities.

The KZN North Coast, particularly the Ballito and Salt Rock areas, is experiencing exponential residential and commercial growth with large influxes of people. This is dramatically changing the semi-rural landscape to peri-urban one, characterised by rapid urbanisation, where agricultural and natural land is converted into a mix of residential, industrial, and infrastructure uses. The trajectory of current crop residue burning practices and mill emissions, if unchanged, will further stress the ecological balance, degrade air, soil, and water quality, and increase the economic burden on environmental and health systems. The emissions will also affect the tourism industry, our rights to an environment not harmful to our health, and other agricultural productivity, underscoring the interconnectedness of environmental health and economic stability.

The government and international regulatory bodies must act with urgency, fostering collaborations which encourage environmentally responsible practices and hold infringing industries accountable. The sugar industry must align its emissions with the global sustainability goals which will lead to a significant improvement of the environmental and public health.

The existence of CAP’s independent air quality monitoring network in the study area and region presents an opportunity to increase community awareness and a way to educate the public about the negative impacts of air pollution on human health.

CAP recommends the creation of community-based air quality advocacy forums, where industry could engage with communities to find collaborative solutions to monitoring emissions and advocating for better industrial and farming practices.

Author

Paolo Del Fabbro Co-Founder Communities Against Pollution (CAP)

Declaration of Competing Interest

The author declares that he has no known competing interest or personal association or relationships that could have influenced the direction of the study.

Funding

The study did not receive any funding.

Availability of data and materials

Data will be made available upon reasonable request.

Acknowledgements

The author thanks the collaborative efforts between Richards Bay Clean Air Association (RBCAA), Dolphin Coast Rate Payers Association (DOCRRA), and Eco-Sud (Mauritius), which gave Communities Against Pollution (CAP) access to ambient air quality data from low cost AirGradient monitors placed at several sites in KwaDukuza (15), Richards Bay (10), Gauteng (6), Western Cape (1), and Mauritius (6). These monitors record PM_2.5, CO₂, VOCs, and NO_x.

The author also thanks the South African Sugarcane Research Institute (SASRI) for giving him access to their meteorological data.

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