Health risks of exposure to air pollutants among students in schools in the vicinities of coal mines

Abstract

Air pollution poses a serious threat to human health and the general ecosystem both in South Africa and globally. This is mostly caused by the mining and combustion of fossil fuels, such as coal. There are some known pollutants associated with coal mining and combustion that are emitted into the air, resulting in various health implications that affect children the most as they are the most vulnerable. In this study, the levels of certain air pollutants in schools in the vicinities of coal mines were assessed. A cross-sectional study design was adopted. Five schools were purposively selected for this study. Air samples were collected inside and outside the classrooms of each school. Radiello® passive air samplers were used to measure the levels of sulphur dioxide, nitrogen dioxide and ozone while filter pumps were employed for lead (Pb). Standard laboratory analytical methods were employed for the analysis. Estimates of the possible health risks resulting from exposure to airborne sulphur dioxide, nitrogen dioxide and ozone were performed using the United States Environmental Protection Agency Human Health Risk Assessment framework. The non-cancer risk of sulphur dioxide, nitrogen dioxide and ozone was determined using the hazard quotient. The results of this study revealed that sulphur dioxide, nitrogen dioxide and ozone were detected within and outside the classrooms at various levels. For example, the concentration of sulphur dioxide within the classroom ranged from 3.0 to 38 µg/m^3. Outside the classroom, sulphur dioxide levels detected were much higher ranging from 17 to 84 µg/m³. The results of the non-carcinogenic risks from exposure to nitrogen dioxide, sulphur dioxide and ozone via inhalation route were less than 1.0. The elevated levels of these pollutants in the vicinity of schools investigated should be a cause for concern for all the stakeholders in the education sector. Therefore, appropriate measures need to be taken urgently to safeguard the health of the concerned community.

Keywords

Air pollution classroom coal mining health risks students health risk assessment

Introduction

Over the past decades, there have been major developments in terms of advancements in technology and industrialisation throughout the world. These have further resulted in a rapid and increased urbanisation and population. The sudden influx and concentration of people in different parts of the world have meant that many resources are consumed. In addition, the large influx of people has impacted negatively on the environment, thereby resulting in various environmental challenges. One such problem is environmental pollution, which is primarily caused by the mining and combustion of fossil fuels, such as coal. This has further led to several other problems such as climate change and global warming. This environmental pollution is a serious issue all over the world, especially in the industrialised nations. This has posed a serious threat to human health, plants, animals and the earth’s ecological systems. Numerous studies have indicated that the combustion of fossil fuel, such as coal used for electricity generation in most countries is largely responsible for air pollution (Liu et al., 2001; Kampa and Carstanas, 2008; Liu et al., 2015; Younger, 2004). This fossil fuel combustion is reportedly the single largest pollutant accounting for 80% of anthropogenic greenhouse gas emissions (Akpan and Akpan, 2012; Quadrelli and Peterson, 2007). Importantly, these greenhouse gases are reported to be largely responsible for climate change and global warming (Akpan and Akpan, 2012; Barnard and Bhattacharya, 2011; Moore et al., 2008). All these problems are having a widespread effects on human health as well as on the ecological and societal systems (Hassan et al., 2016; Longobardi et al., 2016; Wardekker et al., 2012).

The World Health Organisation (WHO, 2016) reported that an estimated 6.5 million deaths are ascribed to urban outdoor air pollution annually. In India, for example, about 55% of Delhi’s population is reportedly directly affected by air pollution that can translate into 3000 ‘premature deaths’ annually due to air pollution-related diseases (Centre for Science and Environment, 2012).

South Africa’s experience regarding the issues of coal mining and combustion is similar to that reported in other countries. This is because South Africa largely depends on coal for electricity generation. According to ESKOM (the Electricity Supply Commission), this country produces about 224 million tonnes of marketable coal per year (ESKOM, 2016). This results in South Africa being known as one of the largest exporters of coal worldwide; in fact, it is the world’s fifth largest coal exporting country (Eberhard, 2011; ESKOM, 2016). In fact, this coal mining and combustion is responsible for the high levels of air pollution (Department of Environmental Affairs and Tourism, 2005). The country releases 170 million tons of carbon dioxide (CO₂) annually, about 0.7 million tons of nitrogen oxides and about 1.5 million tons of sulphur oxides into the environment through electricity generation (Lloyd, 2002). These unsustainable levels of pollutants released into the environment over the years have caused much harm to the health of people, especially those living in communities where these mines and power stations are situated (Wright et al., 2011). In fact, it is of grave concern that the most susceptible and neglected population ‘subject to serious health effects from air pollution may be those who live very near major exposure routes’ (Brugge et al., 2007). This view is in line with the air quality model report of WHO (2016) which indicated that ‘92% of the world’s population lives in places where air quality levels exceed recommended limits’.

According to Greenpeace Africa, an estimate of 2200 premature deaths per year is reported due to emissions from coal-fired power plants. This figure includes 200 deaths of young children (Baillie, 2015).

In all these incidences, it is to be noted that children in these polluted communities are reported to be the most vulnerable. Based on recent investigations, the environment in which they live and learn is highly polluted (Albers et al., 2015; Naidoo et al., 2013; WHO, 2017). They are more vulnerable to the effects of any environmental hazard exposure than any other segment of the society because their bodies are still fragile and their organs still developing (Millennium Ecosystem Assessment, 2005; WHO, 2017). The implications of the health problems resulting from air pollution are identified as the major reason for absenteeism among American school children (Meng et al., 2012; Park et al., 2002). In South Africa, absenteeism due to various health problems that result in hospital admission is also a major issue among school children in these polluted environments as indicated in the studies of both Albers et al. (2015) and Naidoo et al. (2013). In fact, it is reported that South African children are major victims of air pollution and this invariably happens within their homes and schools (Mathee, 2003). In their comparative study, Zwi et al. (1990) examined the respiratory health status of children living in this present study area (Mpumalanga Province) and other less polluted areas. The results revealed that children in the polluted areas were suffering from different respiratory problems such as a cough, asthma, wheezing and chest colds compared to the control group. The researchers went further and asserted that the reason for this was the fact that these children attended schools in a pollution exposed environment.

Air pollutants and health implications

Other than carbon monoxide (CO) and CO₂, coal contains several pollutants that are released into the air which invariably affect human health and the general ecosystem (Sabbioni et al., 1984). Examples of these pollutants, as investigated in this study, are ozone (O₃), sulphur dioxide (SO₂), nitrogen dioxide (NO₂) and lead (Pb). Several studies conducted in South Africa and other countries have indicated that exposure to these pollutants may be associated with serious diseases such as increased respiratory ailments, reduced lung function, nervous system damage in children, cardiovascular diseases, cancer in various forms and an increased number of deaths (Albers et al., 2015; Brunekree and Holgate, 2002; Burt et al., 2013; Dockery and Pope, 2002; Leonarte et al., 2009; Mathee, 2003; Okonkwo et al., 2001; Olaniyan et al., 2017; Stieb et al., 2002; Tang et al., 2008; Wright et al., 2011).

People who live near combustion sources such as coal-fired plants are reported to be exposed to higher levels of any of these pollutants (Bryan and Loscalzo, 2017; Guarnieri and Balmes, 2014; Liu et al., 2012). For example, a comparative study was conducted in the US between people living in residential areas that were in proximity to coal-fired plants and those who were not in proximity to coal-fired plants. The results revealed an association between residential proximity to fuel-fired power plants and hospitalisation rate for respiratory diseases such as asthma compared with one that had no power plant (Liu et al., 2012). Another study conducted in South Africa in schools located around mine dumps indicated that these school children are exposed to high levels of air pollutants such as SO₂ inside their classrooms. These children were reported to have suffered from asthma attacks as a result of these pollutants (Nkosi et al., 2017).

Similarly, in South Africa, Albers et al. (2015) examined respiratory health implications and the associated risk factors in children living in two towns in Mpumalanga (Emalahleni and Middelburg) where air pollution levels are high. The result of this study indicated that these children were exposed to air pollution both in their schools and homes and as a result were diagnosed with various health problems which resulted in the absence of some students at certain times. Thirty-four per cent of the children had experienced a respiratory infection from their childhood up to the present time. About 16.5% of the children were diagnosed with bronchitis, asthma (7.1%), chest coughs (10.1%), 25% (phlegm), and others. Likewise, in Taiwan, studies among children in schools located around coal-fired plants revealed that exposure to arsenic might contribute to DNA damage, asthma and allergic rhinitis in children (Wong et al., 2005). In Oslo, Norway, on the other hand, long-term exposure to NO₂ has been reported to result in lung cancer among mine workers (Nafstad et al., 2003). Similarly, in Japan, school children exposed to NO₂ were also found to have suffered from respiratory illnesses (Shima and Adachi, 2000).

Mine workers exposed to SO₂ in the United States are invariably reported to die from chronic lung diseases (Bridbord et al., 1979). Studies on school going children have also reported an association between exposure to SO₂ and illnesses resulting in absenteeism in Korea (Park et al., 2002) and Europe (Sunyer et al., 2003). A study conducted in New Orleans revealed that a high concentration of Pb in the blood was responsible for an 89% increase in deaths from cardiac diseases (Menke et al., 2006). For children, Pb according to the US Centre for Disease Control and Prevention has been regarded as one of the most dangerous environmental threats (Hou et al., 2017). Recent studies have reported that exposure to Pb from soil, water and dust can lead to several health problems such as elevated blood Pb levels which lead to impaired cognitive development in children (Hou et al., 2017). Studies conducted in South Africa and various other places have also reported that exposure to Pb affects children’s IQ levels negatively (Heinze et al., 1998; Koller et al., 2014; Malcoe et al., 2002; Mathee, 2004; Schutz et al., 1997; Schwartz, 1994).

These chemicals may also affect pregnant women. For example, a research study conducted at the University of Southern California revealed that pregnant women who breathe air heavily polluted with O₃ are at risk of giving birth to children afflicted with intrauterine growth retardation (Salam et al., 2005). It is also reported that O₃ exposure is a major cause of absenteeism among school children in Southern California communities where about 83% experience upper respiratory illnesses (Gilliland et al., 2001).

Furthermore, these pollutants when deposited on the ground seep into the soil, thereby leading to the permanent degradation of the soil and also affects the pH of the soil (Čakmak et al., 2014; Cui et al., 2015; Hou et al., 2017). One of the studies conducted in Emalahleni has reported a high concentration of the different heavy metals, namely cobalt (Co), chromium (Cr), nickel (Ni) and Pb in the soils due to atmospheric deposition (Maya et al., 2015). These metals are reported to have contaminated and reduced the quality of the soil and damaged the plants (Maya et al., 2015).

In terms of agriculture, the best soil in the country is largely found in this area, which makes the province the largest producer and supplier of food in South Africa (Bureau for Food and Agricultural Policy, 2012). Unfortunately, due to coal mining activities, the quality of the soil has reduced drastically over the years. This has continued to affect the quality of agricultural produce negatively, thereby leading to increases in food prices all over the country (Bureau for Food and Agricultural Policy, 2012). Farmers in this area, for example, complained that the pollution had had a severe effect specifically on their maize crop thereby leading to the contamination and death of several tonnes of the crop and more tonnes will be lost in the future (Bureau for Food and Agricultural Policy, 2012).

High concentrations of these toxic elements in the soils with the acidic pH affect plants and pose a great risk to the health of people who consume the contaminated agricultural products (Ochieng et al., 2010). With regard to water quality, these pollutants coming from coal mines and power stations through atmospheric deposition and surface run-off have also caused serious degradation to South African water systems (Cloete et al., 2017; Zibret, 2013).

This has further resulted in acidification of the water and has affected the health of the people and animals that depended on the water for drinking (Bureau for Food and Agricultural Policy, 2012; Ochieng et al., 2010). Poor people who do not have the money to buy safe drinking water might have to depend on the contaminated water not even minding the effects this could have on their health (News24, 2012). A study conducted on a particular stream in Mpumalanga revealed contamination and mortality of aquatic bodies by various heavy metals such as Pb and cadmium (Cloete et al., 2017). It is to be noted that when these contaminated aquatic organisms such as fishes are consumed, they can pose a great danger to human health (Cloete et al., 2017; Ochieng et al., 2010). Studies have reported that ingestion of these metals (e.g. Pb) from soil, water and dust can lead to several health problems such as neurotoxicity, kidney toxicity, sterility, anaemia and hypertension (Hou et al., 2017).

The effects of pollution in this area are not only limited to humans but also animals in this area were also found to have been affected in various ways. For instance, farmers in this area have continuously complained about the severe pollution which is also affecting their cattle’s drinking water, which, in turn, affects milk production and quality. They also reported negative impacts on the fertility of their cattle and their inability to reproduce (Bench Mark Foundation, 2014).

Methods and materials

Research site

The study was conducted in the town of Emalahleni, which is situated on the Highveld of the Mpumalanga Province of South Africa. Emalahleni, formerly known as Witbank, means a place of coal. In the Mpumalanga Province (formerly known as the Eastern Transvaal Highveld), coal mining activities have been in existence as far back as the 18th century (Maya et al., 2015; Munnik et al., 2010).

About 45 collieries and 12 power stations are situated on the Highveld of the Mpumalanga Province and most of these are concentrated in the town of Emalahleni (Yende, 2016). In fact, about 220 million tons of coal are mined in Mpumalanga per year, which is equivalent to around 90% of South Africa’s annual total coal mine yield (Baillie, 2015). Emalahleni is a coal mining town that also supplies the coal to neighbouring power stations for electricity generation. In addition, there are a number of smelting companies around the mines which use the coal in the foundries (Maya et al., 2015). The Department of Environmental Affairs declared this air pollution hotspot a Highveld priority area in terms of the National Environmental Management: Air Quality Act 39 of 2004 (Department of Environmental Affairs, 2011; Munnik et al., 2010). Air pollution in this area is characterised by a mixture of different toxic substances such as hydrocarbons and greenhouse gases at high concentrations (Pone et al., 2007). In fact, several reports have indicated that Witbank (Emalahleni) has the highest concentrations of these various pollutants in the atmosphere and the dirtiest air in the world (Maya et al., 2015; Munnik et al., 2010; Zibret, 2013). All these factors have had negative effects on this environment, the health of people and the general ecosystem as well (Zibret, 2013). In fact, conversations with a number of the town’s residents revealed that almost every evening one would notice smog emanating from the coal-fired plants and several other industries. Furthermore, a conversation with one of the selected schools’ principals revealed that there were approximately 15 mines in the general vicinity of her school and sometimes when it is windy, the coal dust blows into the classrooms (Olufemi, 2011, personal communication).

Furthermore, due to the development as a result of industrialisation that brought increased job opportunities, Emalahleni has doubled its population in the last 10 years (South African Cities Network, 2014).

Sampling procedures

There are about 25 schools in this local municipality. When selecting the sample, the researcher contacted the local Department of Education who indicated that schools that were within the coal mining and combustion precinct would be the most appropriate to choose. Five schools that were closest to the coal mines and coal-fired plants were chosen. After the schools were selected, the researcher approached the principal in each school to explain what needed to be done. In order to maintain the anonymity of the schools, these were identified as School A, School B, School C, School D and School E.

Collection of air samples

The aim of collecting air samples was twofold. First, we hypothesised that compounds such as NO₂, SO₂, O₃ and Pb would be readily available in the air. The hypothesis was based on the fact that the schools were in the proximity of the coal mines and the allied industries. Furthermore, this hypothesis is influenced by the 2005 WHO Air Quality Guidelines (WHO, 2005) designed to offer global guidance on reducing the health impact of air pollution (Millennium Ecosystem Assessment, 2005; WHO, 2011). Specifically, Radiello cartridges (samplers) measuring the presence of NO₂, SO₂, O₃ and a filter measuring the presence of Pb were used. Second, the levels or densities of each of the identified compounds in the air within the vicinity of the participating schools were established. Four samplers were set up in each school. Two types of samplers were put in the classrooms, and two were put outside the classrooms (on the school premises). One sampler was used to collect both NO₂ and SO₂. The other sampler was used to collect only O₃. The first setting up of equipment and sample collection for NO₂, SO₂ and O₃ commenced on 5 June 2012. The O₃ samples were taken for analysis after seven days. Two weeks were allocated for the sampling of NO₂ and SO₂. Accordingly, for these two compounds, the collection period was 5–19 June 2012. To collect Pb, sampling pumps with filters were used over a period of seven days (12–19 June 2012). In this instance, two sampling pumps were set up at two schools, namely School C and School E. The pumps were connected to an electricity power source and the filters were fixed onto the mouth of each pump. The filters were then used to collect air particles from the school environment. Upon collection of the equipment at School E on the seventh day, it was evident that the pump had been tampered with. However, the equipment at School C was intact.

Quality control

Quality control involves the use of certain procedures to verify that the analytical methodology used for sample analysis fulfils the requirements for quality. In this work, the following quality control measures were taken:

Method blanks were analysed to monitor possible contamination.

Samples were analysed in duplicates to monitor precision.

Specifically, the Radiello samplers for the air analysis were sealed in plastic tubes and were then stored and transported in ice coolers from the sampling site to the laboratory. Each sample was labelled clearly and this was recorded in a quality log book. For quality process in the laboratory, samples were received and kept in the refrigerator until analysis. The air samples were prepared with the blank Radiello sample that was not exposed to the field to check. In addition, the quality control procedure for the air sampling and monitoring carried out in this research work included preventative maintenance of equipment and calibration of equipment.

Analysis of samples

In sum, 10 Radiello cartridges were collected for the determination of NO₂ and SO₂. In addition, 10 cartridges were collected for the determination of O₃. Concurrently, one filter was collected for the analysis of Pb (the other one was tempered with at School E). During the testing for the presence of NO₂ and SO₂, initially, the extraction of the cartridges was performed with diluted hydrogen peroxide. The main analysis after the extraction involved the use of ion chromatography. On the other hand, O₃ was determined by spectrophotometric analysis in accordance with the method published by Radiello®. Finally, to test for the presence of Pb the exposed filter was initially subjected to acid digestion followed by graphite furnace atomic absorption spectroscopy.

Human health risk assessment (HHRA)

The HHRA framework is useful for estimating the human health risk that could occur from exposure to a known pollutant (Thabethe et al., 2014). It is predictive and uses existing exposure data to measure the health effects of human exposure to a particular pollutant (Briggs et al., 1996). Human exposure was explained in terms of the average daily dose (ADD) and was computed using equation (1)

{ADD}_{inh} = \frac{C * InhR * EF * ED}{BW * AT}

(1)

where ADD is the ADD of the pollutants; C is the concentration of NO₂, SO₂ and O₃ in ambient air (µg/m³); ED is the exposure duration (days), BW is the body weight of the exposed group (kg); AT is the averaging time (days); InhR is the inhalation rate (m³/day) and EF is the exposure frequency (days/year). An EF of 350 days per year was used to calculate the lifetime exposure of human receptors (both child and adult receptors) with the assumption that the entire population in the study area spends a maximum of 14 days away from the study area (US EPA, 1991). The values of these parameters were obtained from the literature, as shown in Table 1.

Table 1.

Recommended values in equations of the daily exposure dose of NO₂, SO₂ and O₃.

Parameter	Definition	Value for age categories	Reference
Parameter	Definition	Adult (19–75 yrs)	Reference
EF	Exposure frequency (days/year)	350	Morakinyo et al. (2017) US EPA (1997)
ED	Exposure duration (years)	30	Matooane and Diab (2003) US EPA (1997)
AT	Averaging time (days); AT = ED × 365 days	10,950	Matooane and Diab (2003) US EPA (1997)
BW	Body weight (kg)	71.8	Matooane and Diab (2003)
InhR	Inhalation rate (m³/day)	21.4	US EPA (1997)

The non-cancer risks of NO₂, SO₂ and O₃ for the study population adults were estimated using the hazard quotient (HQ). The HQ measures the presence or absence of adverse health effects due to exposure to a pollutant (Muller et al., 2003; US EPA, 1997). It is defined by dividing the ADD from each exposure route by a definite reference dose (RfD)

H Q = \frac{A D D}{R f D}

(2)

RfD is the maximum daily exposure limit allowable for humans (Li et al., 2014: 845). For this present study, the 24-hour NO₂ (188 µg/m³), SO₂ (125 µg/m³) and the 8-hour O₃ (120 µg/m³) as stipulated by the national ambient air quality standard for South Africa and the South Africa standards – Air Quality Act (Act 39 of 2004) were used.

An HQ of 1.0 is the benchmark of safety. An HQ that is <1.0 indicates an insignificant or ‘negligible risk, that is, the pollutant under scrutiny is not likely to induce adverse health effects, even to a sensitive individual. An HQ > 1.0 indicates that there may be some levels’ of risks to sensitive individuals as a result of exposure (US EPA, 1989).

Results

Before presenting the results of this present study, it is perhaps prudent to highlight South Africa’s acceptable levels of the pollutants reported here. Table 2 shows the national ambient air quality standards for NO₂, SO₂, O₃ and Pb as proposed by the Department of Environmental Affairs (RSA) (2004).

Table 2.

National ambient air quality standards for NO₂, SO₂, O₃ and Pb.

	Averaging period	Density (µg/m³)
NO₂
	1 hour	200
	1 year	40
SO₂
	10 minute	500
	1 hour	350
	24 hours	125
	1 year	50
O₃
	8 hours	120
Pb
	1 year	0.5

Source: Adapted from Department of Environmental Affairs, RSA (2004).

It should be explained that it is difficult to argue for the actual benchmarking with the national ambient air quality standards (Department of Environmental Affairs, 2004) and the (WHO, 2011) values as the averaging periods differed. All one can do is to extrapolate using the given values; however, a disadvantage of doing that would be speculative in nature. The compounds detected in the air were NO₂, SO₂ and O₃. When presenting the results, all the calculations in respect of the determination of NO₂, SO₂ and O₃ concentrations were based on an average ambient temperature that was obtained from the South African Weather Service. Table 3 shows the concentrations depicting of NO₂, SO₂ and O₃ in the air in the vicinity of the schools. The values were provided here to give a better picture of how the pollutants may affect teaching and learning in schools.

Table 3.

Concentrations of NO₂, SO₂ and O₃ measured inside and outside the classrooms in each school.

School	Location	Sample ID	NO₂	SO₂	O₃
School	Location	Sample ID	(µg/m³)
School A		O-12-1680	19	4.8	40
School B		O-12-1691	20	3.0	10
School C	Inside	O-12-1693	20	6.0	30
School D		O-12-1695	26	38	26
School E		O-12-1697	28	8.8	18
School A		O-12-1690	9.9	17	110
School B		O-12-1692	24	20	82
School C	Outside	O-12-1694	19	17	110
School D		O-12-1696	24	84	66
School E		O-12-1698	27	31	75

It is observable from the table that the concentrations of NO₂ within the classrooms ranged between 19 and 28 µg/m³, while the levels obtained outside the classroom ranged from 9.9 to 27 µg/m³. In fact, the results show that NO₂ concentrations within and outside the classrooms were relatively constant. According to the WHO (2011), the recommended values for exposure to NO₂ should be at a rate of 40 µg/m³ on an annual mean and 200 µg/m³ on a 10-minute mean. It needs to be explained that an x-hour mean is calculated every hour and averages the values for x hours. Consequently, a 10-minute mean entails exposure to the indicated amount of 200 µg/m³ in 10 minute. Both within and outside the classrooms, learners in this study were exposed to relatively low levels of NO₂ (see Table 2).

In terms of SO₂, the concentrations within the classroom ranged between 3.0 and 38 µg/m³ while outside the classrooms, they ranged from 17 to 84 µg/m³. These results indicate that the amounts of SO₂ were extremely high within the classrooms of School D. The recommended exposure values to SO₂ should be at a rate of 20 µg/m³ on a 24-hour mean and 500 µg/m³ on a 10-minute mean (WHO, 2011). It may be observed from Table 2 that the SO₂ levels within the classrooms were well below the recommended levels with the exception of school D. Outside the classroom, however, the levels were at the threshold limit for School B, while they were high for School E and School D, respectively. In terms of O₃, the concentrations ranged between 10 and 40 µg/m³ within the classroom while it was between 75 and 110 µg/m³ outside the classroom. According to WHO (2011), it is recommended that the acceptable levels of exposure to O₃ should be at 100 µg/m³, on an 8-hour mean. The results presented in Table 2 show that in all the schools, the exposure levels to O₃ were acceptable inside the classrooms. However, they were beyond the acceptable limit outside the classrooms in School A and School C.

As indicated previously, the filter for Pb placed at School E was found to be tampered with. In fact, the filter did not take any particulate material, so no results could be reported from it. However, a Pb reading could be assessed from the filter placed at School C. With respect to the presence of Pb, atomic absorption spectroscopy was used after acid digestion of the exposed filter. The results indicated that the Pb density was <0.007 µg/m³.

The results of the analysis for non-carcinogenic risks from exposure to NO₂, SO₂ and O₃ via the inhalation route are presented in Table 4. All the HQ values of adults for all the studied schools are less than 1.0. This finding is consistent with the outcome of a study conducted by Morakinyo et al. (2017) where they determined the HHRA of sub-10 µm and gaseous pollutants in an industrial area.

Table 4.

HQ values for NO₂, SO₂ and O₃.

Schools		HQ
Schools		NO₂	SO₂	O₃
School A	Indoor	1.0E-03	5.1E-04	4.5E-03
School A	Outdoor	7.0E-04	1.8E-03	1.2E-02
School B	Indoor	1.4E-03	3.2E-04	1.1E-03
School B	Outdoor	1.7E-03	2.1E-03	9.2E-03
School C	Indoor	1.4E-03	6.4E-04	3.3E-03
School C	Outdoor	1.4E-03	1.8E-03	1.2E-02
School D	Indoor	1.8E-03	4.1E-03	2.9E-03
School D	Outdoor	1.7E-03	9.0E-03	7.3E-03
School E	Indoor	2.0E-03	9.4E-04	2.0E-03
School E	Outdoor	1.9E-03	3.3E-03	8.4E-03

HQ: hazard quotient.

An HQ of less than 1 signifies that the concentration of NO₂, SO₂ and O₃ will likely pose no threat to public health. This implies a negligible risk, even to a sensitive individual. However, recent epidemiological studies have revealed that exposure to low levels of NO₂ could increase emergency room hospitalisation for acute and obstructive lung diseases in the general population (Chen et al., 2012; Santus et al., 2012). ‘It has even been previously established that no level of exposure to O₃ is safe since health risk has been found to be associated with O₃ even at concentrations below the recommended standards’ (OECD, 2008).

Discussion

In this study, the levels of certain air pollutants in schools in the vicinity of coal mines were assessed. The results of this study revealed that pollutants such as SO₂, NO₂, O₃ and Pb were indeed present in the vicinity of the schools. The reality is that exposure to these pollutants may result in harmful health effects (either short term or long term) even when present at low levels (Norman et al., 2007).

For example, exposure to SO₂ can affect the respiratory system and the functioning of the lungs. Problems arising from this exposure are associated with coughing, mucus secretion, aggravation of asthma and chronic bronchitis that ‘make people more prone to infections of the respiratory tract’ (WHO, 2011). SO₂ is also reported to be the main cause of irritations of the eyes (Norman et al., 2007; WHO, 2011). The fact that concentrations of SO₂ in some of the study schools were high is a cause for concern. This finding is similar to a study conducted in Montreal, Canada, where it was reported that increased emissions of SO₂ resulted in the prevalence of asthma among children who live and attend school in proximity to petroleum refineries (Deger et al., 2012).

With regard to NO₂, concentrations inside and outside the classrooms were at levels between 19 and 28 µg/m³. This may look innocuous when compared to the WHO (2011) guidelines of 40 µg/m³ on an annual mean, but the point is that it was present within the school environment. This corresponds with a study conducted in Helsinki, Finland where the levels of NO₂ both inside and outside the school were at minimal levels compared with the recommended guidelines (Mukala, 1999). Furthermore, the authors affirm that both short- and long-term exposure to this pollutant resulted in respiratory health problems such as coughing among the children (Mukala, 1999). In this present study, the main issue, however, is prolonged exposure to NO₂ by the community. In fact, epidemiological studies have shown that symptoms of bronchitis in asthmatic children increase proportionately with long-term exposure to NO₂ (WHO, 2011).

The results pertaining to O₃ show that in all the schools, the exposure levels were acceptable within the classrooms. However, they were beyond the acceptable limit outside the classrooms in School A and School C. For instance, O₃ is reported to be responsible for breathing problems. A study conducted in New York reported a similar finding where increased levels of ambient O₃ resulted in chronic asthma and hospital admissions among exposed children (Lin et al., 2008). However, it is generally reported that O₃ may trigger asthma, reduce lung function and cause lung diseases (WHO, 2011).

In this study, the level of Pb measured at School C was found to be < 0.007 µg/m³. This level of Pb could be low when compared with the recommended limits. In the US, for example, the recommended air quality level for Pb is 1.5 µg/m³ for a maximum quarterly calendar average (the United States Environmental Protection Agency, 2012). In fact, the WHO (2004) recommended value is 0.5–1.0 µg/m³ on an annual mean.

A positive aspect of the Pb value in this study is that when compared with other studies, the level was low. A study conducted in the Western Cape Province of South Africa reported high levels of Pb in the air of the school environment. In that particular study, it was found that children were at risk of excessive exposure to environmental Pb and over 90% of their blood had levels of 10 µg/m³ (Mathee et al., 2006). Similarly, a Nigerian study reported high levels of Pb in the air of the school environment and also in the urine of children in both urban and rural schools, which were above the recommended WHO AQGs (Esimai and Awotoye, 2009).

It may be argued, however, that the concentrations of some of the air pollutants reported in this study were at minimal levels. The problem here, though, is prolonged exposure. For instance, learners starting in Grade 8 in one of the schools are likely to be exposed to the pollutants for the next five years if they are to study there until Grade 12. The compounded effect of this exposure is a cause for concern. Therefore, it is critical that better environmental pollution management systems should be implemented by the mines and the allied industry. This could be achieved by these entities assisting in ensuring that there is a marked decrease in the amounts of the pollutants they churn out. Major reductions will certainly assist learners and educators breathing pollution-free air. With regard to this issue, it is argued that an important issue is the fact that health benefits accrue in the long run from improvements in environmental management (Remoundou and Koundouri, 2009). For example, in Europe, it has been shown that a considerable reduction in pollutants such as SO₂ has been observed in the last decade (Devalia et al., 1993).

Conclusions

This study assessed the levels of certain air pollutants in schools in the vicinities of coal mines. The study was conducted in a coal mining town wherein there are also coal-fired electricity generating power stations and ferro-metal foundries. Four different compounds (SO₂, NO₂, O₃ and Pb) were investigated.

The findings revealed that pollutants were present in the air in the vicinity of the selected schools in this study. A source of concern with regard to the pollutants identified here is the fact that they are responsible for a number of harmful effects. Some of the harmful effects of these pollutants were outlined in this study.

It may be possible that these school children are aware that some of their health problems may be linked to the pollution in their environment but the fact remains that they have no control over the problem. The main conclusion in this study relates to the fact that the presence of pollutants in the schools is a source for concern.

Significantly, Section 24 of the Constitution of the Republic of South Africa Act 108 0f 1996 states that

…everyone has a right.

to an environment that is not harmful to their health and well-being; and

to have the environment protected for the benefit of the present and future generations, through reasonable legislative and other measures that – (i) Prevents pollution and ecological degradation; (ii) Promote conservation; and(iii) Secure ecologically sustainable development, and the use of natural resources while promoting justifiable economic and social development. (Goolam, 2000: 124)

It is evident that what the people are experiencing in the polluted areas is a complete departure from what has been stated in the constitution.

It is extremely crucial that the environment in which these children live and learn is safe in terms of their health. This statement is in line with the World Health Organisation reports

…the physical, social and intellectual development of children requires an environment, which is both protected and protective of their health. A growing number of diseases in children are linked to unsafe environments in which they live, play, learn and grow. (Pityana, 2001: 323)

Recommendations

The results of this study warrant that certain recommendations should be made. Globally, environmental issues are becoming more serious every passing day. It is important, therefore, that future generations should not inherit polluted or completely destroyed environments. In this study, the levels of certain air pollutants in schools in the vicinities of coal mines were assessed. Based on the results of this study, it was shown that air pollutants were present inside the selected schools. It is recommended, therefore, that a monitoring equipment be stationed around the schools to manage the air quality. A crucial aspect of air quality management is the continuous monitoring of air quality data. Monitoring of the quality of the air provides an avenue for specifying the scientific basis for policy formulation and measurement of compliance with a stipulated guideline for enforcement purposes.

Not only that we want to recommend that learners and the educators should undergo medical check-ups from time to time. This is because, while it may be argued that the levels of some of these pollutants as reported in this study were not that high, exposed members of the concerned community nonetheless spend most part of their lives in the schools. The presence of learners and their educators in this environment on a daily basis means that they are vulnerable to the pollution effects of these compounds. For instance, while it may appear that the level of Pb found in the air in this study was not too high, this could still cause major health problems for children. The Pb content may be a problem with children because it is reported that ‘… even small exposures are associated with reduced IQ, increased ADHD and other health problems in children… No safe blood-lead level for children has been identified’ (Young, 2012). The fact that their schools are sited around these industries makes this issue even more urgent because they are exposed to these chemicals on a daily basis. The situation is critical because the majority of these children were born and grow up in this polluted environment. If they are to be exposed to these chemicals until adulthood, then their health prospects are really compromised.

On the part of the mining industries, we recommend that they should adopt the best environmental practices or the best available operations to reduce the environmental problems resulting from their operations. The government also should adopt the ‘polluter pay policy’ to serve as a deterrent for unwanted pollution of the environment by the mining companies. All these precautions are necessary to achieve a higher level of environmental equity.

If the people polluting the environment today in the past had been educated about pollution and how it could pose a great danger to human health and the general ecosystem, we would not have been encountering all these problems today. Therefore, there is an urgent need to begin to educate these young people about the environment and how to protect and preserve it in order to prevent future problems.

It has been realised that South Africa, like other nations, is already in the process of shifting from the use of non-renewable to renewable sources of energy. Therefore, it is recommended that the government should speed this process up in order to combat the pollution resulting from the use of coal.

Finally, the government is advised that it should not site schools close to polluting industries in the future and, if possible, existing schools should be relocated.

Footnotes

Acknowledgements

We would like to thank Brian Cowan and Andreas Trüe of the Consulting and Analytical Services of the Council for Scientific and Industrial Research (CSIR) for their contribution with regard to both the data collection and analysis of this work.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was financially supported by the office of the Dean of Humanities, the Tshwane University of Technology, Pretoria, South Africa.

References

Akpan

(2012) The contribution of energy consumption to climate change: A Feasible policy direction. International Journal of Energy Economics and Policy 2(1): 21–33.

Albers

Wright

Voyi

KVV

, et al. (2015) Household fuel use and child respiratory ill health in two towns in Mpumalanga. South African Medical Journal 105(7): 573–577.

Baillie

(2015) Poisoned people, Greenpeace Africa. Available at: http://www.greenpeace.org/africa/en/campaigns/Climate-change/coal-testimonies/ (accessed 23 January 2018).

Barnard

Bhattacharya

(2011) Power Generation from Coal: Ongoing Developments and Outlook. International Energy Agency Information Paper No. 2011/14. Paris: OECD Publishing.

Bench Mark Foundation (2014) Coal Mining in South Africa Is Threatening Food Security. Media Statement by the Bench Marks Foundation. Johannesburg: Bench Mark Foundation.

Bridbord

Costello

Gamble

, et al. (1979) Occupational safety and health implications of increased coal utilization. Environmental Health Perspectives 33: 285–302.

Briggs

Corvalan

Nurminen

(1996) Linkage Methods for Environmental Health Analysis: General Guidelines. Geneva: World Health Organisation.

Brugge

Durant

Rioux

(2007) Near-highway pollutants in motor vehicle exhaust: A review of epidemiologic evidence of cardiac and pulmonary health risks. Environmental Health 6: 23.

Brunekree

Holgate

(2002) Air pollution and health. Lancet 360: 1233–1242.

10.

Bryan

Loscalzo

(2017) Nitrite and Nitrate in Human Health and Disease. Cham: Springer International Publishing.

11.

Bureau for Food and Agricultural Policy (2012) Evaluating the Impact of Coal Mining on Agriculture in the Delmas, Ogies and Leandra District: A Focus on Maize Production. Pretoria: Bureau for Food and Agricultural Policy (BFAP).

12.

Burt

Orris

Buchanan

(2013) Scientific Evidence of Health Effects from Coal Use in Energy Generation. Chicago: University of Illinois.

13.

Čakmak

Beloica

Perоvić

, et al. (2014) Atmospheric deposition effects on agricultural soil acidification state – Key study: Krupanj municipality. Archives of Environmental Protection 40(2): 137–148.

14.

Centre for Science and Environment (2012) 55% Delhi population directly hit by air pollution. The Times of India, 1 March, 1. Available at: http://articles.timesofindia.indiatimes.com/2012-03 01/pollution/31113127_1_airpollution-pollution-level-air-quality (accessed 12 March 2012).

15.

Chen

Samoli

Wong

(2012) Associations between short-term exposure to nitrogen dioxide and mortality in 17 Chinese cities: The China Air Pollution and Health Effects Study (CAPES). Environmental International 45: 32–38.

16.

Cloete

Shaddock

Nel

(2017) The use of two microbiotests to evaluate the toxicity of sediment from Mpumalanga, South Africa. Water South Africa 43(3): 409–412.

17.

Cui

Zhou

Peng

, et al. (2015) Effects of atmospheric deposition nitrogen flux and its composition on soil solution chemistry from a red soil farmland, southeast China. Environmental Science Process & Impacts 17(12): 2082–2091.

18.

Deger

Plante

Jacques

, et al. (2012) Active and uncontrolled asthma among children exposed to air stack emissions of sulphur dioxide from petroleum refineries in Montreal, Quebec: A cross-sectional study. Canadian Respiratory Journal 19(2): 97–102.

19.

Department of Environmental Affairs (2011) Highveld Priority Area Air Quality Management Plan. Pretoria: Department of Environmental affairs.

20.

Department of Environmental Affairs (RSA) (2004) Government Gazette: National Environmental Management: Air Quality Act No. 39 of 2004, 534 (32 816). Pretoria: Department of Environmental Affairs.

21.

Department of Environmental Affairs and Tourism (2005) Sustainable Development: South Africa Country Report of the Fourteenth Session of the United Nations Commission. Pretoria: Department of Environmental Affairs.

22.

Devalia

Sapsford

Cundel

, et al. (1993) Human bronchial epithelial cell dysfunction following in vitro exposure to nitrogen dioxide. European Respiratory Journal 6: 1308–1316.

23.

Dockery

Pope

III (2002) Outdoor particulates. In: Steenland

Savitz

(eds) Topics in Environmental Epidemiology. New York: Oxford University Press, pp.119–166.

24.

Eberhard

(2011) The Future of South African Coal: Market, Investment and Policy Challenges. Stanford, CA: Program on Energy and Sustainable Development.

25.

Esimai

Awotoye

(2009) Estimation of lead in urine of school children in South Western Nigeria and effect of ascorbic intervention. African Journal of Environmental Science and Technology 3: 370–375.

26.

ESKOM (Electricity Supply Commission) (2016) Coal in South Africa. Facts sheet. Available at: http://www.eskom.co.za/AboutElectricity/FactsFigures/Documents/CO0007CoalSARev14.pdf (accessed 31 March 2016).

27.

Gilliland

Berhane

Rappaport

, et al. (2001) The effects of ambient air pollution on school absenteeism due to respiratory illnesses. Epidemiology 12: 43–54.

28.

Goolam

(2000) Recent environmental legislation in South Africa. Journal of African Law 44(1): 124–128.

29.

Guarnieri

Balmes

(2014) Outdoor air pollution and asthma. Lancet 383(9928): 1581–1592.

30.

Hassan

Hashim

(2016) Impact of climate change on air quality and public health in urban areas. Asia Pacific Journal of Public Health 28(2S): 38S–48S.

31.

Heinze

Gross

Stehle

, et al. (1998) Assessment of lead exposure in school children from Jakarta. Environmental Health Perspectives 106: 499–501.

32.

Hou

O’Connor

Nathanail

, et al. (2017) Integrated GIS and multivariate statistical analysis for regional scale assessment of heavy metal soil contamination: A critical review. Environmental Pollution 231: 1188–1200.

33.

Kampa

Carstanas

(2008) Human health effects of air pollution. Environmental Pollution 151: 362–367.

34.

Koller

Brown

Spurgeon

, et al. (2004) Recent developments in low-level lead exposure and intellectual impairment in children. Environmental Health Perspectives 112 (9): 987–994.

35.

Leonarte

Ballester

Tenías

, et al. (2009) Sources of indoor air pollution and respiratory health in preschool children. Journal of Environmental and Public Health 2009: 1–19.

36.

van der Kuijp

(2014) A review of soil heavy metal pollution from mines in China: Pollution and health risk assessment. Science of the Total Environment 468–469: 843–853.

37.

Lin

Liu

, et al. (2008) Chronic exposure to ambient ozone and asthma hospital admissions among children. Environmental Health Perspectives 116(12): 1725–1730.

38.

Liu

Peng

Yang

, et al. (2001) Sulphur in coal and its environmental impact from Yanzhou mining district, China. Chinese Journal of Geochemistry 20(3): 274–281.

39.

Liu

Lessner

Carpenter

(2012) Association between residential proximity to fuel-fired power plants and hospitalization rate for respiratory diseases. Environmental Health Perspectives 120(6): 807–810.

40.

Liu

Chen

, et al. (2015) Coal mine air pollution and number of children hospitalizations because of respiratory tract infection: A time series analysis. Journal of Environmental and Public Health 2015: 1–7.

41.

Lloyd

(2002) Coal Mining and the Environment. Cape Town: Energy Research Institute, University of Cape Town.

42.

Longobardi

Montenegro

Beltrami

, et al. (2016) Deforestation induced climate change: Effects of spatial scale. PLoS One 11(4): e0153357.

43.

Malcoe

Lynch

Keger

, et al. (2002) Lead sources, behaviors, and socioeconomic factors in relation to blood lead of Native American and white children: A community-based assessment of a former mining area. Environmental Health Perspectives 110: 221–231.

44.

Mathee

(2003) Children are major victims of environmental pollution in South Africa. Science in Africa – Africa’s first on-line science magazine. Available at: http://www.scienceinafrica.co.za/2003/june/child.htm (accessed 27 February 2012).

45.

Mathee

(2014) Towards the prevention of lead exposure in South Africa: Contemporary and emerging challenges. NeuroToxicology 45: 220–223.

46.

Mathee

Röllin

Von Schirnding

, et al. (2006) Reductions in blood lead levels among school children following the introduction of unleaded petrol in South Africa. Environmental Research 100: 319–322.

47.

Matooane

Diab

(2003) Health risk assessment for sulphur dioxide pollution in South Durban, South Africa. Archives of Environmental Health 58(12): 763–770.

48.

Maya

Musekiwa

Mthembi1

, et al. (2015) Remote sensing and geochemistry techniques for the assessment of coal mining pollution, Emalahleni (Witbank), Mpumalanga. South African Journal of Geomatics 4(2): 174–188.

49.

Meng

Babey

Wolstein

(2012) Asthma-related school absenteeism and school concentration of low-income students in California. Preventing Chronic Diseases 9(5): 1–8.

50.

Menke

Muntner

Batuman

, et al. (2006) Blood lead below 0.48 micromol/L (10 microg/dL) and mortality among US adults. Circulation 114: 1388–1394.

51.

Moore

Stanitski

Jurs

(2008) Chemistry: The Molecular Science, Volume. 3rd ed. Ottawa: Cengage Learning.

52.

Millennium Ecosystem Assessment. (2005). Ecosystems and Human Well-being: Synthesis. Washington, DC: World Resources Institute, Island Press.

53.

Morakinyo

Adebowale

Mokgobu

, et al. (2017) Health risk of inhalation exposure to sub-10 µm particulate matter and gaseous pollutants in an urban-industrial area in South Africa: An ecological study. BMJ Open 7(3):1–10.

54.

Mukala

(1999) Personal Exposure to Nitrogen Dioxide and Health Effects Among Preschool Children. Academic Dissertation, Faculty of Medicine, University of Helsinki. National Public Health Institute (KTL), Helsinki, Finland.

55.

Muller

Diab

Binedell

, et al. (2003) Health risk assessment of kerosene usage in an informal settlement in Durban, South Africa. Atmospheric Environment 37: 2015–2022.

56.

Munnik

Hochmann

Hlabane

, et al. (2010) The Social and Environmental Consequences of Coal Mining in South Africa: A Case Study. Cape Town: Environmental Monitoring Group.

57.

Nafstad

Haheim

Oftedal

, et al. (2003) Lung cancer and air pollution: A 27 year follow up of 16 209 Norwegian men. Thorax 58: 1071–1076.

58.

Naidoo

Robins

Batterman

, et al. (2013) Ambient pollution and respiratory outcomes among school children in Durban, South Africa. South African Journal of Child Health 7(4): 127–134.

59.

News24 (2012) Poor residents forced to drink dirty water. News24, 2 February. Available at: https://www.news24.com/southafrica/news/poor-residents-forced-to-drink-dirty-water-20120216 (accessed 15 January 2018).

60.

Nkosi

Wichmann

Voyi

(2017) Indoor and outdoor PM10 levels at schools located near mine dumps in Gauteng and North West Provinces, South Africa. BMC Public Health 17(42): 1–7.

61.

Norman

Cairncross

Witi

, et al. (2007) South African comparative risk assessment collaborating group estimating the burden of disease attributable to urban outdoor air pollution in South Africa in 2000. South African Medical Journal 97(7): 782–787.

62.

Ochieng

Seanego

Nkwonta

(2010) Impacts of mining on water resources in South Africa: A review. Scientific Research and Essays 5(22): 3351–3357.

63.

OECD (2008) OECD Environmental outlook to 2030. Organization for Economic Co-operation and Development. Available at: http://www.sourceoecd.org (accessed 20 November 2017).

64.

Okonkwo

Salia

Lwenje

, et al. (2001) Determination of urinary lead in school children in Manzini, Swaziland, Southern Africa. The Environmentalist 21: 205–209.

65.

Olaniyan

Jeebhay

Röösli

, et al. (2017) A prospective cohort study on ambient air pollution and respiratory morbidities including childhood asthma in adolescents from the Western Cape Province. Study protocol. BMC Public Health 17(712): 1–13.

66.

Park

Lee

, et al. (2002) Association of air pollution with school absenteeism due to illness. Archives of Pediatrics & Adolescent Medicine 156: 1235–1239.

67.

Pityana

(2001) 3rd Economic and Social Rights Report. 1999/2000 executive summary. Johannesburg: South African Human Rights Commission.

68.

Pone

JDN

Hein

KAA

Stracher

, et al. (2007) The spontaneous combustion of coal and its by-products in Witbank and Sasolburg coalfields of South Africa. International Journal of Coal Geology 72: 124–140.

69.

Quadrelli

Peterson

(2007) The energy–climate challenge: Recent trends in CO2 emissions from fuel combustion. Energy Policy 35(11): 5938–5952.

70.

Remoundou

Koundouri

(2009) Environmental effects on public health: An economic perspective. International Journal of Environmental Research and Public Health 6: 2160–2178.

71.

Sabbioni

Goetz

Bignoli

(1984) Health and environmental implications of trace metals released from coal-fired power plants: An assessment study of the situation in the European Community. Science Total Environment 40: 141–154.

72.

Salam

Millstein

, et al. (2005) Birth outcomes and prenatal exposure to ozone, carbon monoxide, and particulate matter: Results from the children’s health study. Environmental Health Perspectives 113: 1638–1644.

73.

Santus

Russo

Madonini

, et al. (2012) How air pollution influences clinical management of respiratory diseases. A case-crossover study in Milan. Respiratory Research 13: 95.

74.

Schutz

Barregard

Sallsten

, et al. (1997) Blood lead in Uruguayan children and possible sources of exposure. Environmental Research 74: 17–23.

75.

Schwartz

(1994) Low-level lead exposure and children’s I.Q: A meta-analysis and search for a threshold. Environmental Research 65: 42–55.

76.

Shima

Adachi

(2000) Effect of outdoor and indoor nitrogen dioxide on respiratory symptoms in school children. International Journal of Epidemiology 29: 862–870.

77.

South African Cities Network (SACN) (2014) EMALAHLENI. SACN Final report. Available at: http://www.sacities.net/wp-content/uploads/2015/10/Emalahleni-final-report-author-tc.pdf (accessed 21 January 2018).

78.

Stieb

Judek

Burnett

(2002) Meta-analysis of time-series studies of air pollution and mortality: Effects of gases and particles and the influence of cause of death, age, and season. Journal Air Waste Management Association 52: 470–484.

79.

Sunyer

Atkinson

Ballester

, et al. (2003) Respiratory effects of sulphur dioxide: A hierarchical multicity analysis in the APHEA 2 study. Journal of Occupational and Environmental Medicine 60: e2.

80.

Tang

Liu

, et al. (2008) Effects of prenatal exposure to coal-burning pollutants on children’s development in China. Environmental Health Perspectives 16(5): 674–679.

81.

Thabethe

NDL

Engelbrecht

Wright

, et al. (2014) Human health risks posed by exposure to PM10 for four life stages in a low socio-economic community in South Africa. Pan African Medical Journal 18: 206.

82.

United States Environmental Protection Agency (1989) Risk assessment guidance for superfund, Vol 1: Human health evaluation manual (Part A). Available at: http://www.epa.gov/superfund/programs/risk/ragsa (accessed 20 June 2015).

83.

United States Environmental Protection Agency (1991) Risk assessment guidance for superfund, vol. I: Human health evaluation manual. Part B. Development of risk based preliminary remediation goals (interim), PB92-963333. Publication 9285.7-01B. Washington, DC: US Environmental Protection Agency, Office of Emergency and Remedial Response.

84.

United States Environmental Protection Agency (1997) Exposure factors Handbook. Available at: http://www.epa.gov/ncea/expofac.htm (accessed 20 June 2015).

85.

United States Environmental Protection Agency (2012) Lead (Pb) air quality data update 2005–2006 design values. Available at: http://www.epa.gov/airtrends/dv_pb_2005_2006.html (accessed 5 January 2012).

86.

Wardekker

De Jong

Van Bree

, et al. (2012) Health risks of climate change: An assessment of uncertainties and its implications for adaptation policies. Environmental Health 11(67): 1–16.

87.

Wong

Kuo

Hsu

, et al. (2005) Increased levels of 8-hydroxy-2′-deoxyguanosine attributable to carcinogenic metal exposure among school children. Environmental Health Perspectives 113(10): 1386–1390.

88.

World Health Organisation (WHO) (2004) Health topics: WHO ambient air quality guidelines. Available at: http://www.searo.who.int/EN/Section3144289htm (accessed 17 May 2012).

89.

World Health Organisation (WHO) (2005) Air Quality Guidelines Global Update 2005. World Health Organisation, Denmark, Europe.

90.

World Health Organisation (WHO) (2011) Air quality and health. Fact sheet no. 313. Available at: http://www.who.int/mediacentre/factsheets/fs313/en/index.html (accessed 28 March 2012).

91.

World Health Organization (WHO) (2016) WHO releases country estimates on air pollution exposure and health impact. Available at: http://www.who.int/mediacentre/news/releases/2016/air-pollution-estimates/en/ (accessed 24 January 2018).

92.

World Health Organisation (WHO) (2017) The cost of a polluted environment: 1.7 million child deaths a year, says WHO. Available at: http://www.who.int/mediacentre/news/releases/2017/pollution-child-death/en/ (accessed 17 January 2018).

93.

World Health Organisation (WHO) (2018) Air Pollution. Geneva: World Health Organisation. Available at: http://www.who.int/airpollution/en/ (accessed 12 January 2018).

94.

Wright

Oosthuizen

John

, et al. (2011) Air quality and human health among a low income community in the Highveld priority area. Clean Air Journal 20(1): 12–20.

95.

Yende

(2016) How coal is making us sick. News24, 11 December. Available at: https://www.news24.com/SouthAfrica/News/how-coal-is-making-us-sick-20161210.

96.

Young

(2012) ‘Senate digs into ‘ghost factory’ risk: Effect of lead on kids is explored’. USA Today, 13 July, 3A.

97.

Younger

(2004) Environmental impacts of coal mining and associated wastes: A geochemical perspective. Geological Society, London Special Publications 236: 169–209.

98.

Zibret

(2013) Witbank air, dirtiest in the world. News24, 25 April 2013. Available at: https://www.news24.com/Green/News/Witbank-air-dirtiest-in-the-world-20130425 (accessed 15 January 2018).

99.

Zwi

Davies

Becklake

, et al. (1990) Respiratory health status of children in the eastern Transvaal Highveld. South African Medical Journal 78(11): 647–653.