Assessment of Environmental and Health Risks of Toxic Heavy Elements in the Dust Falling on Different Areas of Kirkuk

Abstract


Introduction
Dust is one of the main pollutants in the atmosphere and the accumulation of natural and anthropogenic solids, which harms human health (Lu et al ., 2015).The name Dust is given to any substance that spreads in the air, including dust particles, which include suspended load, smoke, fog, soot, consisting of organic and inorganic substances of terrestrial origin such as dust storms, factory smoke, bacteria, pollen, forest fires, volcanic vapors, as well as minutes of solid atmospheric dust, which remain suspended in the atmosphere for long periods and can move and spread with the movement of the wind and for long distances, showing a significant difference in size, shape, distribution and concentration (Iqbal, 1983).Airborne dust consists of very small particles of soil or rocks that have been lifted from the Earth's surface due to wind erosion and turbulence under atmospheric and soil conditions, therefore the chemical composition and changing physical properties of dust are effective and important factors for determining the origin of dust (McConnell et al., 2008;Awadh, 2022).
Natural erosion of soil, sand and rocks are the most common source of dust, pollen, microorganisms, plant material, dander (dead skin cells shed by animals).They are also part of the dust in the environment , dust emission is common in urban areas from large-scale industrial processes, the size of dust particles varies from visible to invisible , the smaller the particle, the longer it stays in the air and the more, Dust particles near the nose and mouth are passive when inhaled or swallowed easily, have an impact and very small dust particles penetrate deep into the lungs, while ultrafine particles can be absorbed directly into the bloodstream (Fussell et al.,2021).
Various mining operations are sources that release huge amounts of dust, especially in open-pit mining, topsoil removal, blasting operations, drilling on roads, handling chemical elements in factories, and other quantitative and qualitative aspects.The dust deposition rate and its chemical components are important for investigating dust pollution in a particular region (Awadh, 2012;Harrison, 2012).the world's dust sources are located in dry lowlands and areas with little vegetation, where the average rainfall is less than 200 mm.Iraq has vast expanses of Sandy Desert (about 40% of the total area of Iraq) and a significant percentage represents a source of airborne dust in the Middle East (Prospero et al., 2002), dust activity in the Tigris-Euphrates River basin begins in March and reaches its maximum in July and decreases significantly by September-November (Middleton, 1987).
It is estimated that metal dust emissions into the atmosphere are between 1000 and 3000 TG per year in the world and this dust can be transported to distant regions (d 'Almeida, 1987).Dust events are an important issue and a major problem that occur annually in the Middle East and the region, including Iraq, and that mineral dust is of great importance in influencing the chemical and physical composition of the atmosphere, (Lawrence et al.,2009),The province of Kirkuk has been divided into two sections according to Sissakian (1992).
The first section comprises the central, southern, and western areas, characterized by semi-flat lands, plateaus, and undulating hills that extend in a southeast-northwest direction.The second section is distinguished by its mountainous regions in the northeastern and southwestern parts of the province.The highest point is situated in the northeastern portion, while the lowest point lies in the southwestern region.In the study area, several exposed geological formations from the recent geological era exist, including the Fatha Formation, Anjana Formation, Muqdadiyah Formation, and Bai Hassan Formation.Additionally, there are recent deposits spanning various ages, ranging from the oldest to the most recent (Pliocene-Pleistocene-Middle Miocene).According to the data from the Meteorological Department in Kirkuk, the prevailing wind direction in Kirkuk is generally northeast, which can sometimes be accompanied by dust storms that transport pollutants and dust to other areas (Ali,2013).
The geochemistry of the soil in the city of Kirkuk is contaminated with elements, especially zinc, and lead (Awadh and Al-Hamdani, 2019;Al-Hamdani et al., 2016).The city of Kirkuk is one of the cities with high concentrations of heavy elements, as the increase of lead and cobalt elements was observed in the town as a result of dust storms and industrial cities (Ahmed et al., 2021).
The current study aims to find the levels of heavy metal concentrations in dust fallout at selected sites of Kirkuk governorate and environmental and health risks assessment.

Materials and Methods
The study area represents the center of the city of Kirkuk, which is located in northern Iraq, 255 km from the capital Baghdad towards the northeast, along the Latitude 35° 46' 81" and longitude 39° 22' 44", with an area of 9679 km 2 (3737 Square mile), surrounded by the north, northeast and northwest Mount Bur range, with an altitude of 300 m above sea level, Dust samples were collected during the months when frequent dust storms occurred (Fig. 1).They were collected from May 2022 to January 2023, taking into account the weather conditions on rainy days.Samples were collected from 8 stations located in different areas.Bottles with the same specifications as those used by the meteorological authority were employed.Basins were positioned at elevated locations above building surfaces, and the samples were gathered in polyethylene bags.The geographical coordinates of the locations were determined using the Global Positioning System.
A trough, 22 cm in length and 13 cm in width, was placed at a height of 3 meters above building surfaces, with a metal bracket placed over the trough to prevent bird droppings from falling into it.A total of 8 stations were established and distributed throughout the city (Table 1).Heavy element analyses of the dust samples were conducted at the Faculty of Geoengineering, Ankara University, Turkey.

Contamination Factor (CF)
Contamination factor is a task performance used to help understand environmental impacts and The coefficient of contamination is calculated according to the equation described by (Hakanson, 1980), where the ratio of the concentration of the element in the samples to the ratio of the concentration of the reference element (Table 2).

CF=(CSample)/ (CBackground)
(1) Csample represents: the measured concentration of the element in the sample for the location of the study area Cbackground represents the concentration of the reference element in the Earth's crust (Wedepohle, 1995).

Enrichment Factor (EF)
It is a widely used measure to determine how much the presence of an element in the sampling medium has increased relative to the average natural abundance due to human activity (Loska et al., 2005), assessing the presence and depth of deposition of anthropogenic pollutants and requires the selection of both the reference element and its natural background, which can strongly influence the calculation results (Bern et al., 2019), and some heavy elements are used as reference elements, the most important of which are the most used as references are Rb, Fe, Al, and Mn according to Loring et al. (1995), rubidium was used as a reference element and the equation was used by the method (Sakan et al., 2009) (Table 2).EF=(Cn/Rb)sample/(Cn/Rb)reference (2) Sample(Cn/Rb) : Represents the ratio of the concentration of the elementin the analyzed model of the study area to the concentration of the element rubidium in the models of the study area Reference Cn/Rb represents the ratio of the concentration of the reference element to the concentration of the reference element rubidium (Wedepohle, 1995)

Degree of Contamination
To facilitate the control of pollution, Hakanson (1980) proposed to perform a diagnosis called the degree of contamination, where it represents the total CF of each sample and classified the degree of contamination into four categories (Table 2).

Health Transactions
To assess the health risk of falling dust, the three tracks were relied on for health assessment due to their periodic exposure, including these tracks (inhalation, skin contact, ingestion), this is done by applying equations 4, 5 and 6 according to EPA (2004) (Table 3).

Results and Discussion
The ranges of concentrations of the copper element ranged by an average of 38.29 µg/kg and by a range of 27.30 -66.30µg/kg (Table 4. It was noted that some stations were higher than the permissible limits (WHO), as it appeared in the sample P1 in the freedom zone by 35.5 µg/kg, which is higher than its concentration in the Earth's crust and higher than the global determinants (WHO).The percentage in the sampleP2 in the Qadisiya area shows that less than its concentration of global determinants in the samples P3, and P4.The residential area and the military district appeared at a percentage of 38.7 µg/kg and38.6 µg/kg and was higher than the global determinants.The sample P5 in the Baghdad Road area appeared at a percentage of 27.3 µg/kg was lower than the global determinants, and appeared in the sample P6 which represents the Arafah area.The percentage of 32.6 µg/kg was also higher than the global determinants.In the area of the Central District in the sample P7 was the highest percentage of all stations, as it appeared at 66.3 µg/kg, as it was much higher than all stations, and the area is located in the south-west of the city, it may be affected in the industrial area located south of the city, which leads to a high concentration and transmission rate through dust, and this is consistent with (Lou et al., 2022(, noting that industrial cities are the source of the rise of heavy elements in urban cities, and also appeared in the sample (P8) by (37.5 µg/kg) and was higher than the global determinants (Table 4).
The source of pollution by this element may be due to the main sources of pollution in the city and This is one of the sources that leads to an increase in its concentration, and it is also considered to be the area that is a source of natural rocks that are rich and move to the atmosphere through the storm, and sulfide ore is the most widespread and is rich in the element copper (Zhang et al., 2022;Ekmekyapar et al., 2015) (Table 4).The ranges of Lead concentration ranged by an average of (28.9 µg/kg) and by a range of 34.5-22.5 µg/kg (Table 4), as it appeared at all stations higher than its concentration in the Earth's crust and higher than its concentration in the global determinants, the stations that were all higher than the global determinants in rather similar proportions promise that this is areas with congestion and areas close to the streets and may be due to the combustion of fossil fuels (coal and the previous use of leaded gasoline), It could have an industrial source and be transmitted within the city through dust (Awadh and Al-Hamdani, 2019).The use of mineral fertilizers and the use of sewage sludge, etc it is considered a source of lead and the reason for its increased concentration (Ahlberg et al., 2006), and contaminated soil containing high levels of lead may be the result of activity.When dust storms occur, leadcontaminated sand particles are lifted into the atmosphere, industrial emissions, Human Factors and vehicles (Wang et al., 2006;Darvishi Boloorani et al., 2023) (Table 4).
The concentration of cobalt reached an average of 34.3 µg/kg and a range of 51.5-16.9µg/kg (Table 4).The concentrations of all stations were higher than the average in the Earth's crust and global determinants table, the source of high levels of cobalt element concentration in the city of Kirkuk may be due to the burning of waste randomly within cities where waste is burned inside the city of Kirkuk daily and randomly, which leads to a rise in the concentration of cobalt (Meugenie et al., 2023;Wippich et al., 2022) (Table 4).
Also the ranges of cadmium concentration ranged at a rate of 0.72 ppm and in a range of 0.9-0.5 µg/kg (Table 4) all stations were in the relatively convergent range and higher than its concentration in the Earth's crust and global determinants table, and in the sample P5, which represents the area of the Wasati neighborhood and sample P7, which represents the area of Baghdad road back by 0.5 µg/kg, equal to the Earth's crust and a slight increase with the global determinants, and the source of cadmium its concentration in the rest of the stations is increased human or economic activities and insufficient fuel disposal procedures and waste incineration processes, which can increase pollution by heavy elements in urban areas (Kovǎ et al., 2022;Badeenezhad et al., 2022) (Table 4).
Arsenic ranged on average 3.1 µg/kg and in the range of 4.6-1.6 µg/kg, as they were all higher than their concentration in the Earth's crust and from the global determinants (Table 4).They were the lowest percentages in the samples P1, and P2), which represent the freedom area and the Qadisiya area and were lower than the global determinants and the highest percentage appeared in the sample P7 by 4.6 µg/kg, which represents the area of its concentration in the Earth's crust and global determinants may have been influenced by industrial activity or influenced by its location to the southwest (Cao et al., 2009), and the second highest percentages appeared in the samples P3, P4, P5, P6, and P8.In this study, the measuring the acid function of the falling dust, the percentage was (7.9-10.5 µg/kg) as arsenic concentration increases in these acidic environments (Parth et al., 2011) (Table 4) Zinc was at a rate of (407 µg/kg) and in a range of (864-161 µg/kg) Table ( 4), all of them were higher than their concentration in the Earth's crust, and appeared in the samples P1, P2, P3, P6, and P7, which is the area of freedom, Qadisiya, Iskan, Arafa and Al-Wasti below the global limits, and in the rest of the samples P4, P5, and P8, which are the areas of Askari district, Baghdad road, and Ronaki were higher than the limits allowed in the global limits (Table 4).The higher concentration in dust may be due to the higher concentration in urban soil (Awadh and Al-Hamdani, 2019).The increase in pollution may be due to high concentrations of zinc from human sources causing an increase in high concentrations are the use of agricultural fertilizers, pesticides, industrial waste, sewage residues, and waste (Eisa, 2015) (Table 4).

Environmental Transactions
After applying the equation 2 of the enrichment factor, where the rate of enrichment of the falling dust with heavy elements was shown sequentially at Zn >Pb>As>Cu>Cd>Co.The rate of enrichment of Zn in the falling dust reached an average of 7.6 µg/kg and a range of 2.8-15.9µg/kg, where it is generally located in the classification Significant enrichment and the lowest rate of enrichment (2.8 µg/kg) in the sample P2.The highest rate of enrichment 15.9 µg/kg in the sample P5, the Pb enrichment rate in the falling dust reached an average of 2.2 µg/kg and in the range of 1.6-2.7 µg/kg, where it is generally within the classification (moderate enrichment).
The lowest enrichment rate was 1.6 µg/kg in the sample P3 and the highest enrichment rate was 2.7 µg/kg in the sample P3.The As enrichment rate in the falling dust reached an average of 2.2 µg/kg and in the range of 1.2-3.4µg/kg, where it falls within the Moderate enrichment.Rating and the lowest rate was 1.2 µg/kg in the sample P2 and the highest rate was 3.4 µg/kg in the sample P7.The enrichment rate of the Cu element reached an average of 1.9 µg/kg and a range of 1.3-3.3µg/kg, where it generally falls within the Deficiency to minimum enrichment rating and the lowest enrichment rate was 1.3 µg/kg in the sample P5 and the highest enrichment rate 3.3 µg/kg in the sample P7.
The Cd element in the falling dust reached an average of 91.6 µg/kg and a range of 1.1-2.2µg/kg, where it falls within the deficiency to minimal enrichment rating.The lowest rate was 1.1 µg/kg in the sample P5 and the highest rate was 2.2 µg/kg in the sample P1.The Co element's enrichment rate reached an average of 1.6 µg/kg and a range of 0.8-2.3µg/kg, and it falls within the deficiency to minimal enrichment and the lowest singing rate was (0.8 µg/kg in the sample P7 and the highest singing rate in the sample P8 (Table 5).After applying the Contamination factor equation 1, the values of the pollution factor for heavy elements in the falling dust were obtained and the results were compared with the pollution factor classification, where the results were the Contamination factor for heavy elements in descending sequence as follows: Zn> Pb> As> Cu> Cd> Co.The Contamination factor rate for the element Zn in the falling dust reached an average of 6.5 µg/kg) and a range of 2.4-13.2µg/kg, where it falls within the Very high Contamination factor classification.The lowest rate was 2.4 µg/kg in the sample P6 the highest rate 13.2 µg/kg in the sample P5, and the rate of element Pb in the falling dust was at a rate of 2µg/kg and in the range of 1.5-2.4µg/kg, where it falls within the classification Moderate Contamination factor.The lowest rate was 1.5 µg/kg in the sample P6 and the highest rate was 2.4 µg/kg in the sample P8.The rate of element As in the falling dust was at a rate of 1.8 µg/kg and in the range of 0.9-2.7 µg/kg, where it falls within the classification Moderate Contamination factor.The lowest rate 1.8 µg/kg is located in the sample P1 and the highest rate 2.7 µg/kg) is located in the sample P7.The rate of the Cu element in the falling dust reached an average of 1.5 µg/kg and in the range of 1-2.6 where it falls within the classification moderate contamination factor.The lowest rate 1 µg/kg was located in the sample P5 and the highest rate 2.6 µg/kg is located in the sample P7.The Cd element in the dust reached the lowest rate 1 µg/kg is located in the sample P7 and the highest rate 1.8 µg/kg is located in the sample P2.The rate of the element Co in the dust falling at a rate of 1.4 µg/kg and a range of 0.7-2.1 µg/kg is located in the classification Moderate Contamination factor and the lowest rate 0.7 µg/kg is located in the sample P7 and the highest rate 2.1 µg/kg is located in the sample P4 (Table 6).59 After applying the equation 3, the degree of contamination of heavy elements in the falling dust was obtained, where they appeared at a rate of 20.9 µg/kg and in a range of 14.7-28.4,where they generally fall into the classification Considerable contamination factor except for sample P1 and sample P6 falls into the classification Moderate Contamination factor ( Table 7 ).The hazard ratio (HQ) is used as a mathematical equation, the ratio of possible exposure to heavy elements is determined relative to the reference value of the permissible exposure of that element from one route so that it does not have health effects (EPA, 2004) if the result is less than one, it means no possible health effects of the element and if it is greater than one.HQ=ADD/RFD (7) Where ADD represents the daily dose rate of the elements and Rfd represents the reference dose for a given route (Table 7).
Hazard Hazard index (HI) is calculated by summing the hazard quotient (HQ) and for the three pathways ( inhalation , ingestion , skin contact) (Zhang et al., 2019) the following equation is used HI=∑(HQing+HQinh+HQdermal) (8) 3.5 × 10 −3 3.52 × 10 −3 5.25 × 10 −4 Zn 3 × 10 −1 3 × 10 −1 6 × 10 −2 By applying the equations7 and 8, the hazard quotient and hazard index of the elements studied were calculated in dust models and it appeared that all the elements were less than this means there is no non-carcinogenic health risk, except for two elements As and Pb, where they were greater than 1, and this means there is a non-carcinogenic health risk, including the Children category (Table 8).

Conclusions
The concentrations of toxic heavy elements in the dust of the study area exceeded the global limits (WHO) and were higher than its concentration in the Earth's crust ,The reason for this can be attributed to the nearby industrial cities, some of which are in close proximity to the city.These include oil companies that are spread around the city, refineries, the cement plant, and the industrial district.
A significant increase in zinc concentration was observed in the samples of the study area, especially in the sample P5 and P4.
The results of the dust enrichment factor in the study area showed that the zinc element falls into the category of significant enrichment, whereas the lead and arsenic elements appeared, they fell into the category (of moderate enrichment).
The results of the Contamination factor showed that the element zinc is among the high pollution, as well as the rest of the elements that were studied, such as lead, copper, cobalt, cadmium and arsenic, as these elements fall into the category of medium pollution.The degree of contamination of heavy elements was obtained in the falling dust, where they generally fall into the classification Considerable contamination except for the sample P1 and the sample (P6) fall into the classification Moderate Contamination.The results of the hazard quotient and hazard index of the studied elements appeared in the dust models and it seemed that all the elements were less than this means that there are no noncarcinogenic health risks, except for the two elements arsenic and lead, as they were greater than 1, which means there are non-carcinogenic health risks and include the Children category.

Fig. 1 .
Fig. 1.Locations of the study area and samples

Table 1 .
Locations and coordinates of samples in the study area

Table 2 .
Divisions of the CF,Cdeg, and EF

Table 3 .
Standard values used to assess the health risk in the study area for adults and children according to(EPA,2004)

Table 4 .
Concentrations of elements in the study area

Table 5 .
Rate the enrichment factor for the study area

Table 6 .
Contamination factor values for the study area

Table 7 .
Values of the degree of contamination of the study area

Table 7 .
Standard or reference values (RFD) used in risk assessment(USEPA,1989)

Table 8 .
Hazard quotient and hazard index values for heavy elements in falling dust, including both categories adults and children