Respiratory health among adolescents living in the Highveld Air Pollution Priority Area in South Africa

Air pollution has long been a major environmental risk to human health [1]. Exposure to both outdoor and indoor air pollution can cause a wide range of respiratory illnesses, such as chronic obstructive pulmonary disease, asthma, bronchiolitis, wheezing, shortness of breath, and lung cancer [2, 3]. Long-term exposure to air pollution has also been found to be associated with cardiovascular diseases, nervous system dysfunctions, and cutaneous diseases [4‐6].

It is estimated that around 91% of the world’s population reside in places where concentrations of air pollutants exceed the World Health Organization (WHO) recommended guidelines [7]. Pollutants of importance include particulate matter with an aerodynamic diameter of less than 2.5 μm (PM_2.5) and less than 10 μm (PM₁₀), ozone (O₃), nitrogen dioxide (NO₂), and sulphur dioxide (SO₂).

The WHO provides recommended guidelines for these pollutants aimed to protect human health; for example, for PM_2.5 and PM₁₀ the guideline values are 10 μg/m³ and 20 μg/m³, respectively [7]. The South African National Ambient Air Quality Standards (NAAQS) [8] are less stringent than the WHO guidelines (see Supplementary Table S1). Given the South African climate and diverse natural activities such as veld fires, particularly in the semi-arid Highveld region which experiences dry winter months, the guideline for PM_2.5 values would not be realistic in the South African setting [9].

Outdoor pollution is mostly attributed to vehicles, power generation, building heating systems, agriculture / waste incineration, and industry, as well as natural sources such as pollen, windblown dust, plumes from volcanic eruptions and sea salt spray [7]. People in low- or middle-income countries may be reliant on highly-polluting solid fuels such as wood, coal, animal dung, and crop wastes for heating, cooking, and lighting, thereby causing indoor air pollution and increasing the air pollution-related disease burden [10‐12].

In November 2007, the Mpumalanga Highveld of South Africa was declared part of the Highveld Air Pollution Priority Area (HPA) by the South African government [13] since ambient air quality in major towns such as eMalahleni, Middelburg, Secunda, Standerton, Edenvale, Boksburg, and Benoni exceeded or were likely to exceed the South African National Ambient Air Quality Standards and that the area requires specific air quality management action to rectify the situation [13]. Satellite data suggests that Mpumalanga is one of the world’s largest air pollution hotspots, with sources including emissions being coal-fired power stations, petrochemical plants, metal smelters, and mines [9, 14, 15]. People living and working in these areas are exposed to air quality that is potentially harmful to their health and well-being [16, 17].

Children and adolescents are particularly vulnerable to environmental risks such as air pollution exposure, even at low levels, due to their developing organs such as lungs and the brain, immune system and metabolic functions, and time spent outdoors, e.g., walking to school or playing sport [18, 19]. Also, children inhale a higher volume of air per body weight than adults [20]. Evidence suggests that PM_2.5, PM₁₀, O₃ and NO₂ are associated with respiratory diseases such as asthma, lung function deficits and air way inflammation in children [19, 21]. However, there is limited research of potential relations between air quality and related respiratory health outcomes among adolescents in South Africa [22‐24].

The aim of the study was to understand adolescent respiratory health and associated risk factors among adolescents living in areas characterized by poor ambient air quality in the HPA. The aim was supported by two research objectives: 1) to determine the prevalence of adverse respiratory health outcomes among adolescents living in an air pollution hotspot; and 2) to consider household-related risk factors related to adverse respiratory health outcomes in the adolescents.

Our study considered the impact of air pollution on adolescent health in a highly air polluted area in South Africa. While we did not find strong evidence for associations between air pollution and respiratory health; a small effect was possible for duration of living in a polluted environment. This may also have been influenced by the relatively small sample size and that we merged towns that likely have different characteristics.

We found that adolescents lived in households that mainly relied on electricity for cooking and heating, although about 10% of adolescents reported that coal was used for heating. Half of the adolescents reported the presence of environmental tobacco smoke in the home. Evidence suggests that exposure to environmental tobacco smoke is associated with childhood upper and lower respiratory tract infection, wheezing and asthma [32]. A Chinese study found that indoor tobacco smoke and respiratory illness (pneumonia, common cold, croup and dry night cough) were significantly associated in children aged 3–8 years with ORs ranging from 1.06 to 1.95 [33]. An increased frequency in asthma was found in high school students aged 11–16 years exposed to environmental tobacco smoke (OR = 1.08, 95% CI, 1.05–1.12) and cigarette smoking (OR = 1.29, 95% CI, 1.17–1.42) in Taiwan [34]. A study in Greece showed that adolescents aged 13–15 years living with mothers who smoke had double the exhaled carbon monoxide compared to non-smoking families [35].

The most common self-reported respiratory health outcomes were allergies, frequent cough, wheezing chest, and doctor-diagnosed hay fever. All of these outcomes have been associated with exposure to air pollution [36‐40]. Regarding hay fever, the timing of the study is an important consideration. Most respondents were recruited in September (56%), October (34%) and November (10%) which are austral spring months. These months are associated with high pollen counts in Mpumalanga [41] and this may have influenced the proportion of adolescents reporting allergies and hay fever.

Ambient air pollution levels in the study area were generally above national and international limits, specifically for PM_2.5, PM₁₀ and O₃. This was unsurprising given the location of the two study areas in the HPA. Previous studies have found similar air pollution levels in HPA [17, 42]. Although a quantitative comparison between the sites, it is important to note that the Embalenhle (SAWS) and Embalenhle (Sasol) sites had exceedances of the NAAQS for PM daily and annually for every time data was available, except the Embalenhle (Sasol) PM₁₀ averages in 2019, compared to Club, which did not have as many exceedances.

A statistically significant association between the number of years that the adolescent had lived in the area (both areas combined) and the presence of respiratory illnesses was found. Given the ambient air quality findings for the study area, particularly PM and O₃, that exceeded limits set to protect human health, this association is reason for concern.

While ambient air quality management is a definitely a priority for this area, primary interventions may also be helpful. Ensuring regular waste collection to prevent waste burning and increasing household income, especially in a study area such as ours where reliance on social grants was relatively high, have been shown to potentially be important for people living in Embalenhle [43].

While this study sample was relatively small, it is the first of its kind to consider self-reported adolescent respiratory health among individuals living in the highly polluted HPA and thus provides valuable baseline data. Some limitations were identified. Schools were not randomly selected, however, are considered to be representative of the schools in the area. Moreover, the small sample size contributed to the risk of underreporting. The adolescent survey asked for ‘ever’ occurrence of respiratory health outcomes, rather than ‘in the past two weeks or past year’. This may have led to over-representation of occurrence, but we deemed this a more reliable measure than asking young people to recall different time periods. We did not ask about certain dwelling characteristics that may also influence household air pollution exposure, which could have contributed to exposure misclassification. For example, ventilation and roof type should be included in more detailed assessments of household air pollution exposure. Our study was conducted during spring; had the study been conducted during winter different fuel sources for heating and cooking may have been given by the adolescents. Household fuel use patterns are known to differ by season [44] hence a repeated cross-sectional or long-term study of fuel use patterns in different seasons would be important for future studies.

Our study provides information on self-reported health outcomes among individuals living in a highly polluted environment in a peri-urban environment for adolescents. Given the specific air pollution concerns for the area, peri-urban nature of the location, and the small sample size, these results cannot be generalised to urban or rural communities, or to children of other age groups. Similar studies in communities in different settings, and involving adolescents and children of different age groups, would be of considerable interest. There is a need for interdisciplinary research that speaks to intersections between multiple systems [45] including the natural environment, physical health, and the uniqueness of both the South African context and adolescence as a life stage.

Our results suggest that adolescents living in areas located within the HPA are adversely affected by air pollution, in particular O₃ and PM. It is essential that we work towards meeting the NAAQS in this area to protect adolescent health. Future research should investigate long-term exposure and health outcomes among adolescents living in the HPA given the risk factor findings here.