Figure 1
Map illustrating study sites Nkangala and Gert Sibande and the air quality monitoring stations within these sites.
Table 1
Summary of district municipality study sites, putative pollutant sources near air monitoring stations, and sampling periods.
| DISTRICT | AQ MONITORING STATION | POLLUTANT SOURCES | NUMBER OF STATIONS SAMPLED | SAMPLING PERIOD |
|---|---|---|---|---|
| Nkangala | Hendrina | Middle‑income residential; not in the vicinity of direct pollutant sources and no local domestic burning [24]. | 1 | 2010–2018 |
| Middelburg | Middle‑income residential; large industrial sources: Columbus Steel and Middelburg Ferrochrome, industries to the south and mine dumps to the northwest, no domestic fuel burning [24]. | 2 (MP and SAWS) | 2009–2018 | |
| eMalahleni | Low‑income site; domestic fuel burning, transport, and industrial and mining emissions [24]. | 1 | 2009–2018 | |
| Gert Sibande | Ermelo | Low‑income site; coal transportation trucks and domestic fuel burning [24]. | 1 | 2010–2018 |
| Secunda | Low‑income site; domestic fuel burning in the vicinity and Sasol plant to the east [24]. | 1 | 2009–2018 | |
| eMbalenhle | Low‑income site; domestic burning, secondary aerosols, wood and biomass burning, and industrial emissions [25]. | 3 | 2016–2018 |
[i] Note: MP: Mpumalanga Province; SAWS: South African Weather Service.
Table 2
Descriptive statistics of the daily mean death counts for Nkangala and Gert Sibande from 2009 to 2018.
| NKANGALA | GERT SIBANDE | |||
|---|---|---|---|---|
| DEATH COUNTS | MEAN ± SD | DEATH COUNTS | MEAN ± SD | |
| All‑cause mortality | 101,246 | 27.8 ± 7.2 | 104,971 | 28.8 ± 8.4 |
| Male | 52,959 | 3.9 ± 2.4 | 54,632 | 3.9 ± 2.5 |
| Female | 48,287 | 3.6 ± 2.1 | 50,339 | 3.7 ± 2.3 |
| 0–18 years old | 11,609 | 1.9 ± 1.1 | 14,219 | 2.3 ± 1.4 |
| 19–45 | 32,893 | 4.68 ± 2.5 | 37,988 | 5.3 ± 2.9 |
| 46–65 | 29,603 | 4.2 ± 2.2 | 28,666 | 4.0 ± 2.1 |
| >65 | 27,470 | 3.9 ± 2.0 | 24,384 | 3.5 ± 1.9 |
Table 3
The cause specific mortality counts for Nkangala and Gert Sibande from 2009 to 2018.
| HEALTH OUTCOME | NKANGALA | GERT SIBANDE | ||||
|---|---|---|---|---|---|---|
| TOTAL | MALE | FEMALE | TOTAL | MALE | FEMALE | |
| IHD* | 2,104 | 1,298 | 806 | 1,527 | 883 | 644 |
| Stroke* | 3,540 | 1,581 | 1,959 | 3,732 | 1,506 | 2,226 |
| LRI | 12,763 | 6,544 | 6,219 | 12,363 | 6,414 | 5,949 |
| COPD | 420 | 313 | 107 | 624 | 458 | 166 |
[i] *Numbers given are for those >25 years old.
Figure 2
Daily death count from 2009 to 2018 in (A) Nkangala and (B) Gert Sibande.
Table 4
South African National Ambient Air Quality Standards (SA NAAQS) and World Health Organization (WHO) air quality reference standards for PM2.5, NO2, and SO2.
| POLLUTANT | AVERAGING PERIOD | SA NAAQS* | WHO* | WHO 2021 | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 2009 | 2012 | 2016 – 2029 | AQG 2005 | IT‑1 | IT‑2 | IT‑3 | IT‑4 | |||
| PM2.5 | 24‑hour | ‑# | 65 | 40 | 25 | 75 | 50 | 37.5 | 25 | 15 |
| 1 year | ‑ | 25 | 20 | 10 | 35 | 25 | 15 | 10 | 5 | |
| NO2 | 1‑hour a | 200 | nc | nc | 200 | ‑ | ‑ | ‑ | ‑ | ‑ |
| 1 year | 40 | ‑ | ‑ | 40 | 40 | 30 | 20 | ‑ | 10 | |
| SO2 | 24‑hour | 125 | ‑ | ‑ | 20 | 125 | 50 | ‑ | ‑ | 40 |
[i] * All pollutant reference concentrations are in μg/m3.
[ii] #South Africa was only assigned a formal reference standard to fine particulate matter in 2012 [15].
[iii] a South Africa has a 1‑hour NO2 reference standard and does not have a 24‑hour reference standard [35], and even though WHO has a 24‑hour standard, the 1‑hour reference standard is used in this study as a comparison with the SA‑NAAQS as the 99th percentile at 4 exceedances per year [32]. ‘nc’ denotes ‘no change’ in regulations in the subsequent year.
Figure 3
Box plots of the average 24‑hour pollutant concentrations from air quality monitoring stations from 2009 to 2018 in Gert Sibande: (A) PM2.5 concentrations with reference standards shown in red lines, (B) SO2 concentrations and reference standards shown in red lines and Nkangala: (C) PM2.5 concentrations and reference standards shown with red lines (D) SO2 concentrations and the reference standards shown in red lines.
Figure 4
Annual average pollutant concentrations for PM2.5 and NO2 at AQ stations from Gert Sibande and Nkangala (2009–2018). Missing columns denote years that did not pass the data availability threshold of 70%.
Figure 5
Hazard quotients (HQ) for Nkangala with (A) 99th percentiles of the 24‑hour average exposure and (B) annual average PM2.5 exposure. Hazard quotients (HQ) for Gert Sibande with (C) 99th percentiles of the 24‑hour average exposure, and (D) annual average PM2.5 exposure, based on South African National Ambient Air Quality Standards (SA NAAQS) and WHO Air Quality Guidelines (WHO AQG).
Figure 6
Hazard quotients (HQ) for (A) annual average NO2 exposure in Nkangala and (B) Gert Sibande based on South African (2009) and WHO [32], (IT3) air quality guidelines.
Figure 7
Hazard quotients (HQ) for (A) 99th percentiles of the 24‑hour average exposure to SO2 in Nkangala with and (B) 99th percentiles of the 24‑hour average exposure to SO2 in Gert Sibande.
Table 5
Summary of the attributable mortality burden to outdoor air pollution in Nkangala and Gert Sibande.
| OUTCOME | YEAR | NKANGALA | GERT SIBANDE | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| AF (%) | DEATHS (FEMALE) | DEATHS (MALE) | TOTAL | % TOTAL BURDEN (% UI) | AF (%) | DEATHS (FEMALE) | DEATHS (MALE) | TOTAL | % TOTAL BURDEN (% UI) | ||
| LRI | 2009 | 14 | 146 | 148 | 293 | 2.4 (1.3–3.3) | 19 | 204 | 206 | 410 | 3.3 (2.0–4.5) |
| 2010 | 17 | 138 | 140 | 279 | 2.5 (1.4–3.4) | 19 | 206 | 213 | 419 | 3.7 (2.2–5.0) | |
| 2011 | 14 | 98 | 112 | 210 | 1.9 (1.1–2.7) | 19 | 146 | 169 | 315 | 2.9 (1.7–4.0) | |
| 2012 | 14 | 106 | 107 | 213 | 2.0 (1.1–2.8) | 19 | 134 | 138 | 272 | 2.6 (1.5–3.6) | |
| 2013 | 11 | 81 | 85 | 166 | 1.6 (0.9–2.3) | 14 | 96 | 106 | 202 | 2.0 (1.1–2.7) | |
| 2014 | 14 | 99 | 111 | 210 | 2.0 (1.1–2.8) | 14 | 75 | 85 | 160 | 1.5 (0.8–2.1) | |
| 2015 | 14 | 87 | 97 | 184 | 1.8 (1.0–2.4) | 14 | 68 | 77 | 146 | 1.4 (0.8–1.9) | |
| 2016 | 14 | 83 | 88 | 171 | 1.6 (0.9–2.3) | 14 | 57 | 65 | 123 | 1.2 (0.6–1.6) | |
| 2018 | 14 | 57 | 53 | 109 | 1.5 (0.9–2.2) | 17 | 51 | 54 | 105 | 1.5 (0.9–2.1) | |
| IHD (>25 years old) | 2009 | 27 | 23 | 40 | 63 | 0.5 (0.5–1.0) | 35 | 26 | 40 | 66 | 0.5 (0.4–0.7) |
| 2010 | 31 | 17 | 42 | 59 | 0.5 (0.5–0.9) | 35 | 27 | 37 | 64 | 0.5 (0.5–0.8) | |
| 2011 | 27 | 24 | 45 | 69 | 0.6 (0.6–1.3) | 35 | 25 | 35 | 61 | 0.5 (0.5–0.9) | |
| 2012 | 27 | 26 | 41 | 67 | 0.6 (0.6–1.3) | 35 | 23 | 31 | 54 | 0.5 (0.5–0.8) | |
| 2013 | 21 | 19 | 32 | 51 | 0.5 (0.5–1.0) | 27 | 13 | 24 | 37 | 0.4 (0.4–0.7) | |
| 2014 | 27 | 33 | 40 | 72 | 0.7 (0.7–1.3) | 27 | 19 | 23 | 42 | 0.4 (0.4–0.8) | |
| 2015 | 27 | 25 | 43 | 68 | 0.6 (0.6–1.3) | 27 | 15 | 23 | 38 | 0.4 (0.4–0.8) | |
| 2016 | 27 | 27 | 35 | 63 | 0.6 (0.6–1.3) | 27 | 24 | 27 | 51 | 0.5 (0.5–1.0) | |
| 2018 | 27 | 17 | 26 | 43 | 0.6 (0.6–1.3) | 31 | 27 | 35 | 61 | 0.9 (0.9–1.5) | |
| Stroke (>25 years old) | 2009 | 46 | 118 | 88 | 206 | 1.7 (1.1–1.9) | 54 | 170 | 117 | 287 | 2.0 (1.5–2.2) |
| 2010 | 50 | 102 | 89 | 191 | 1.7 (1.1–1.9) | 54 | 142 | 105 | 248 | 1.9 (1.4–2.1) | |
| 2011 | 46 | 109 | 89 | 198 | 1.8 (1.3–2.1) | 54 | 150 | 106 | 256 | 2.2 (1.6–2.5) | |
| 2012 | 46 | 92 | 76 | 169 | 1.6 (1.1–1.9) | 54 | 135 | 71 | 206 | 1.9 (1.4–2.1) | |
| 2013 | 40 | 81 | 64 | 145 | 1.4 (0.9–1.7) | 46 | 116 | 76 | 192 | 1.8 (1.3–2.1) | |
| 2014 | 46 | 109 | 88 | 197 | 1.9 (1.3–2.2) | 46 | 112 | 78 | 189 | 1.8 (1.3–2.1) | |
| 2015 | 46 | 111 | 84 | 194 | 1.9 (1.3–2.2) | 46 | 105 | 71 | 176 | 1.8 (1.3–2.1) | |
| 2016 | 46 | 103 | 85 | 188 | 1.8 (1.3–2.1) | 46 | 110 | 63 | 172 | 1.8 (1.3–2.1) | |
| 2018 | 46 | 68 | 59 | 127 | 1.8 (1.3–2.1) | 50 | 79 | 69 | 148 | 2.1 (1.5–2.4) | |
| COPD | 2009 | 19 | 2 | 6 | 9 | 0.07 (0.05–0.08) | 26 | 4 | 13 | 17 | 0.11 (0.08–0.13) |
| 2010 | 22 | 3 | 8 | 11 | 0.09 (0.07–0.11) | 26 | 4 | 12 | 16 | 0.12 (0.08–0.14) | |
| 2011 | 19 | 2 | 7 | 9 | 0.08 (0.05–0.10) | 26 | 6 | 13 | 19 | 0.16 (0.11–0.19) | |
| 2012 | 19 | 2 | 8 | 10 | 0.09 (0.07–0.11) | 26 | 6 | 14 | 21 | 0.19 (0.13–0.22) | |
| 2013 | 15 | 1 | 7 | 8 | 0.08 (0.05–0.10) | 19 | 2 | 11 | 13 | 0.13 (0.09–0.15) | |
| 2014 | 19 | 2 | 7 | 9 | 0.09 (0.07–0.11) | 19 | 3 | 9 | 13 | 0.12 (0.08–0.15) | |
| 2015 | 19 | 3 | 6 | 9 | 0.08 (0.05–0.10) | 19 | 4 | 12 | 16 | 0.16 (0.11–0.19) | |
| 2016 | 19 | 3 | 5 | 8 | 0.08 (0.05–0.10) | 19 | 2 | 8 | 11 | 0.11 (0.08–0.13) | |
| 2018 | 19 | 2 | 3 | 5 | 0.08 (0.05–0.10) | 22 | 5 | 9 | 14 | 0.20 (0.14–0.23) | |