Coal Dust Exposure Characteristic and Impact on Respiratory Impairment from Coal Unloading Station in Palembang, South Sumatra, Indonesia

Coal hauling, loading, and transportation activities impacted the emergence of coal dust which is harmful to health. The coal dust exposed from coal unloading stations and coal waterway transportation has escaped attention. This study aimed to determine the characteristics of coal dust, the influence of climate parameters on the spread of coal dust, and its impact on the health of children under five in the exposed area. The coal dust characteristics and concentrations of PM PM 2.5 and PM 10 were analyzed from ten points spread across three mining companies (A, B, and C). The effect of climate parameters on PM 2.5 and PM 10 was tested statistically. The results of the chemical analysis revealed that coal dust was dominated by the high content of Si, Al, S, and Fe. The concentration of PM 2.5 and PM 10 is affected by wind speed. PM 2.5 and PM 10 can exceed the annual threshold value, which has caused a high incidence of respiratory problems in two sub-districts, namely Makrayu and Gandus.


INTRODUCTION
Coal is a reliable source of abundant energy and an asset for Indonesia. Coal has played an essential role in power generation and is a necessary fuel for producing steel, cement, and other industrial activities. Around 60% of the world's steel construction and 40% of power generation are currently powered by coal (Mahdevari and Shahriar, 2016). One of the important issues involved in coal mining operations is coal dust, which can cause a series of health problems (Yao et al., 2020). Almost all mining processes are accompanied by the appearance of coal dust (Shahan and Reed, 2019).
Fine particles are a concern, because the concentration of PM 2.5 and PM 10 has increased due to industrial developments and human activities, especially the particulate matter from coal dust which is harmful to health. Coal dust is the most significant hazard associated with mining activities (extraction processes, blasting operations, drilling, cutting, ore transport, or by mechanical means during handling) (Fan and Liu, 2021). Wind speed, moisture content, and mechanical handling are some of the factors associated with the amount of coal dust produced (Fabiano et al., 2014). Coal dust categorized as PM 2.5 and PM 10 is even smaller than that of fine coal, measuring <3 mm . Coal dust combines various heavy metals and toxic metals that harm human health due to long-term exposure. An inorganic multiplex mixture in coal dust consists of (C, H, O, N, Quartz, Cd, Fe, Br, Cu, Ni, Zn, Pb, Na, Ti, S, and Mg and their oxides, which vary according to particle size, type of and coal seams (Vasić et al., 2021).
In addition to domestic use, Indonesia imported coal to several countries through waterways (Pradono et al., 2019). Before shipping by ship, coal is stacked at the shipping station for a certain time before being loaded. The accumulation and transportation of coal while at the station have exposed coal dust to the air. So far, the coal dust highlighted is the coal dust in coal mining and power generation units. Meanwhile, no attention was paid to the area around the coal unloading station in the waterway. To the best of authors' knowledge, no study has investigated the coal dust characteristics and possible health effects of PM 2.5 and PM 10 from coal unloading stations. This study aimed to examine the characteristics of coal dust and its impact on the incidence of respiratory distress at the coal unloading station in Palembang. This work also examines the effect of climate parameters on the concentration of particulate matter.

MATERIALS AND METHODS
The coal dust was taken from a location adjacent to the coal unloading station on the banks of the Musi River, Palembang City, South Sumatra (3°01'02°S, 104°44'55'E). The coal dust comes from the coal stockpiles from three different companies, namely PT. A, PT. B and PT. C, hereinafter referred to as A, B, and C. The coal dust is carried by the wind to densely populated settlements across the river (3°01'01°S, 104°44 '43'E). The coal dust was collected by manual grab sampling method at the sampling point using a scoop and then placed into a plastic bag according to ISO 18283:2006. In detail, the research locations and sampling points are shown in Figure  1. The chemical analysis was carried out to determine the chemical composition of the coal dust using X-ray Fluorescence Spectroscopy (PANalytical Epsilon 3 XLE XRF).

Coal dust characteristics
The elemental composition of the coal dust particulate matter collected in three sampling sites is summarized in Table 1. The elemental analysis of the coal dust shows that silica has the highest concentration in the three places. The coal dust from PT. B has the largest number of sulfur-rich (S-rich) particles. Sulfate in PM 2.5 is commonly identifi ed as a secondary aerosol marker associated with long-distance transport ( Figure 2. Coal morphology of the three coal companies carried out at 10 locations directly opposite the coal unloading station (Figure 3). On the basis of the results of a survey at ten observation points, it was found that there was a lot of coal dust stuck to the walls of residents' houses, and residents submitted complaints. Figure 4 shows the results of measurements of the PM 2.5 and PM 10 concentrations at ten sampling points of areas exposed to coal dust. The content of PM 2.5 and PM 10 was found to be highest at sampling points 6 and 7, which are directly opposite PT B and C. Meanwhile, the area directly opposite PT A also has a relatively high content of PM 2.5 and PM 10 . However, all points show that PM 2.5 and PM 10 are still within the regulatory threshold in Indonesia. Of the ten sampling points, points 6 and 7 have the highest concentrations for both PM 2.5 and PM 10 . Although the PM 2.5 concentration is still below the 24-hour Indonesian national ambient air standard (65 g/m 3 ) (Kusuma et al., 2019), assuming that the sampling can represent the average annual PM 2.5 level, then the concentration will exceed the Indonesian annual average ambient air quality standard (15 g/m 3 ) and WHO guidelines (10 g/m 3 ) (Lestiani et al., 2015).
Exposure to PM 2.5 bound metals can cause severe carcinogenic or non-carcinogenic toxicity in humans depending on various factors, such as exposure concentration, duration, and   Table 1. The dust-related sources are identified in the coarse fraction and are characterized by crustal elements, including Ca, Mg, Si, Al, Fe, and Ti. This source is generated locally from the distribution of coal from the delivery station to the temporary coal storage stockpile and loading to barges. The elements found in dust-related sources can also be associated with the resuspended dust generated from coal transportation to shipping areas. The concentrations of Al, Si, S, and Fe are the main components. All of these components are probably emissions from coal.

Effect of climate parameters on coal dust and PM concentration
The mass concentration of particulate matter (PM) is closely related to climate parameters, which will affect the diffusion of PM. Figures  5-7 show the average wind speed, temperature, and relative humidity at ten sampling points. The daily average wind speed is different at each point, ranging from 3.53 to 5.20 m/s ( Figure  5). The average daily temperature ranged from 28.7 to 32.4°C (Figure 6), and the average relative humidity value varied from 68.4 to 73.1% (Figure 7). Spearman correlation was applied to identify the effect of climate parameters on particulate matter, the results of which are summarized in Table 2. Table 2 shows the relationship between climate parameters and PM concentrations. Wind speed has a significant effect on PM 2.5 with pvalue = 0.001 < 0.05. Wind speed and PM 2.5 have a very strong positive correlation with a correlation coefficient of 0.879. The same is also found in the PM 10 . Wind speed has a significant effect on PM 10 with p-value = 0.022 < 0.05. The two variables have a strong positive correlation  with a correlation coefficient of 0.709. For every unit increase in wind speed, it will increase 0.879 PM 2.5 concentration and 0.709 PM 10 concentration. Strong winds cause the rate of transfer of coal dust to increase. Temperature and relative humidity are negatively correlated to both PM 2.5 and PM 10 . Every unit increase in temperature will decrease the PM 2.5 concentration by 0.987 and the PM 10 concentration by 0.487. Furthermore, for every unit increase in relative humidity, it will decrease the PM 2.5 concentration by 0.960 and the PM 10 concentration by 0.544.

Incidence of respiratory distress
There are two sub-districts directly opposite the coal station. The study continued by identifying the incidence of respiratory disease in children under five, which became a problem in the two districts. Figure 8 shows the total incidence of respiratory disorders in the last ten years compiled from two first-level health care facilities. Before the COVID-19 pandemic (2012-2019), numerous cases of respiratory disorders were recorded in the two sub-districts. The highest   number of cases reached 4576 patients in the Makrayu sub-district. The incidence of respiratory disorders decreased when Covid-19 hit in 2020. This was made possible due to restrictions on people's movements, especially toddlers, because the learning activities in schools are based online. Thus, the intensity of activities outside the home is greatly reduced.
Children are more active outdoors than adults, so they are more susceptible to the exposure to polluted air. In addition, children have immune systems and lung function which are not fully developed. Environmental pollution that causes respiratory health problems in children is more significant, especially in developing countries, and this happens because it is accompanied by poor nutrition. The particulate matter from coal dust can cause decreased lung development in children, asthma, and lung and even heart disease (Liu et al., 2019).

CONCLUSIONS
The analysis of the coal dust at the coal unloading station has been carried out. The coal dust is dominated by the elements Si, Al, S, and Fe. The concentrations of PM 2.5 and PM 10 in the exposed coal dust are still below the daily threshold but have the potential to exceed the annual threshold. Wind speed has a significant effect on the spread of PM 2.5 and PM 10 . There are cases of high respiratory distress that occur in the toddlers in the coal dust distribution area.