Comprehensive Evaluation of some Heavy Metals in Dust Deposited on Eucalyptus Tree Leaves and their Health Effects in Erbil City, Northern Iraq

Abstract


Introduction
Rapid industrialization and urbanization had resulted in serious environmental problems, including an increase in heavy metals in dust caused primarily by anthropogenic activities such as industrial discharge, fossil fuel combustion, tire wear, motor vehicle and brake pad wear, vehicle exhaust emissions, and construction activities, as well as additional natural sources (Fan et al., 2021;Yu et al., 2021).Dust storm, which is a natural phenomenon that happens over the world on large scale, they usually happen in dry land which consider as half of the world area (Awadh, 2023).Dust is the most pervasive and significant factor influencing human health and well-being (Yongming et al., 2006;Awadh, 2015), consisting of particulate or solid matter in the form of fine powder, lying on the ground or on the surface of objects, or being blown by mechanical or natural forces (Adekola and Dosumu, 2001).The dust is made up of a wide variety of organic and inorganic particles that have strong environmental indicator effects can adverse the urban communities (Awadh and Al-Hamdani, 2019).Its sources are natural sources (atmospheric deposition, and soil erosion) and human sources including industrial emissions, transportation, urban development, municipal emissions) (Torghabeh et al., 2019;Gupta et al., 2020).
Dust can provide information about the distribution level and fate of contaminants present on the surface, so it is considered as significant environmental media (Habib et al., 2012;Jassim et al., 2021).As the components of settled dust similar to the particles in the atmosphere, we used it as indictor of the contamination by using heavy metals in the atmosphere (Leung et al., 2008;Awadh, 2015).The term heavy metal is used in general for metal related to environmental pollution effects toxicity and health hazards to living organisms and human, which have been a subject of great concern, due to their toxicity, ability to accumulate in the human body via bioaccumulation, and longevity in the atmosphere (Ali et al., 2021;Mitra et al., 2022).
Exposure to polluted dust can endanger human health at several levels, ranging from allergic responses to cancer (Taiwo et al., 2020), including respiratory symptoms, worsening of chronic respiratory and cardiovascular disorders, and impaired lung function (Yu et al., 2022).HMs can enter the body by three main routes 1) ingestion 2) inhalation 3) dermal contact (Al-Shidi et al., 2020).
Monitoring of heavy metal is most important to assess their distribution with time and locations and indicator of the quality of urban ecological environment (Ramesh and Gopalsamy, 2021), the researcher had difficulty when they used equipment by setting an environmental station with skilled technicians and it only suitable for some selected area (Sharma and Uniyal, 2016(.Biomonitoring of air pollution using plant is the method of interest in recent time as it is cost-effective and environmentally friendly technique that substitute physical and chemical analytical method, Plant are greatly distributed in remote area, easy to access (Badamasi, 2017;Roy et al., 2020), because plants are stationary and they are constantly exposed to pollutants in the surrounding atmosphere , the effect of pollution often appears on plant leaves due to their abundance in large quantities and being the primary receptors for a large number of air pollutants which made them suitable bio-observatory (Pandit and Sharma, 2020).Eucalyptus fast growing and environmentally trees that able to reduce the pollution effect, which is highly valued because it plays essential role in controlling pollution and trapping dust (Nawaz et al., 2021).
There are few studies related to the evaluation of heavy metals concentrations in the dust accumulated on the leaves of plants.Harkko et al. (2021) studied the foliar dust and heavy metal deposit on leaves of urban tree in Budapest, Hungary.El-Khatib et al. (2020) investigated the bioaccumulation of heavy metal air pollutants by urban trees.
The primary goals of the current study are to evaluate the concentration of heavy metals (As, Cd, Co, Cu, Cr, Mn, Ni, Pb, V, and Zn) in dust collected from a Eucalyptus plant in Erbil.To assess the level of heavy metal pollution in the dust using contaminate factor (CF), Geo-accumulation Index (Igeo), Pollution Load Index (PLI), Enrichment Factor (EF), and to assess the Potential Ecological Risk Index.To evaluate the carcinogenic and non-carcinogenic human health risk.

Study Area
Erbil Governorate is Capital of Kurdistan Region of Iraq and located the northeastern of Iraq.The study area Erbil City its site within the longitude of 43°51'00-44°12'00 E and latitude 36°30'00-36°18'00 N. The Erbil City is located in the foothill zone that is part of the stable tectonic unit of the Iraqi Plateau.Geomorphologically, the region is flat with occasional low hills.From a stratigraphic point of view, the study area is covered by Quaternary and Pleistocene deposits dominated by clays, silts and sands (Jassim and Goff, 2006).The age of these sediments varies from the Pleistocene to the Holocene (Buday and Jassim, 1978).Quaternary deposits include settlement deposits, river terraces, polygenetic deposits, and floodplain deposits (Sissakian and Youkhana, 1987).Quaternary sediments incompatible with the Bai-Hassan Formation (Pliocene) and dominated by thick conglomerates alternating with shales, mudstones and sandstones (Buday, 1980).
The climate has a very important effect on dust blowing (Khosravi et al., 2019;Tao et al., 2022;Awadh, 2023).The climate of Erbil City is characterized by a semi-arid continental climate.According to Koppe climate classification, the city is tropical /subtropical semi-arid (Hassan, 2006).Erbil City climate is cool and rainy in winter and warm and dry in summer.The average climate of Erbil during 2013-2022 was temperature and precipitation was 16.6-28c° and 404 mm, respectively.The hottest two months were July &August the temperature can reach 43.8, Precipitation fall between November to April with light rain in October and may.The average wind speed experience mild seasonal variation over the course of the year.In the last decade it was 1.06-1.76,September was the mildest and December was wildest (The data was obtained from Meteorological, Organization & Seismology of Kurdistan Region of Iraq).

Sampling Collection
Thirty dust samples were collected from the leaf of the Eucalyptus trees during summer season (June and July 2022).The dust was sampled from the industrial, street, park (green area), and residential area.The sampling site's locations determined using the GPS.The description of the sampling points is shown in Table 1 and Fig. 2. Dust samples were collected according to the method (El-Khatib et al., 2020).The leaves were taking from the tree at high (1.5-2m) above the ground, we used polyethylene gloves to gather leaves and then stored them in plastic bags.Great care was taken in selecting leaves to avoid imperfections such as bird droppings, insect infestations and the use of pesticides.Leaves were randomly collected from the lower two-thirds of the tree canopy.The collected leaves were transported to the laboratory for washing and subsequent processing.

Sample Preparation
The dust adhering to the plant leaf surface was removed by washing the fresh leaves of the collected sample with distilled water, and the washing solution was filtrated using Whatman 42 ashless filter papers.The filter paper of each site with deposited dust was dried at ambient temperature in the clean air room for 24 hours to avoid contamination and to fix the weight of dust mass.

Sample Analysis
The analysis of heavy metal concentrations (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn) in dust samples was performed using the Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) technique at the Australian Laboratory Services (ALS) in Spain.

Pollution Assessment Methodology
The Geo-accumulation Index (Igeo), Contamination Factor (CF), Enrichment Factor (EF), Pollution Load Index (PLI), Potential Ecological Risk (Er), and Risk Index (RI) were utilized to evaluate the level of heavy metal pollution in the dust samples collected from all study sites within the area and to assess their ecological risk.In the absence of specific reference values for heavy metals in dust, the reference values for heavy metals in soil were employed to assess the pollution indices and ecological risk, following the methodology outlined by Kabata-pendias (2011).

Geo-Accumulation Index (Igeo)
The Geo-accumulation Index (Igeo), which was initially introduced by Müller in 1969, has become a widely utilized method for assessing the extent of metal pollution.In the context of our study, we employed the Igeo to evaluate the level of heavy metal pollution present in the collected dust samples.The expression used for Igeo in this study is as follows: (1) Where Cn is measured concentration of metal in dust, Bn background concentration of the metal In order to mitigate the potential impact of variations in background values arising from lithological differences in the sediment, a correction factor of 1.5 was introduced (Dat et al., 2021).Additionally, the Geo-accumulation Index (Igeo) was classified into seven distinct groups by Muller (1969) to facilitate the categorization of values, which are presented in Table 2. for reference and interpretation.

Contamination Factor (CF (
The Contamination Factor (CF) is used to calculate the degree of pollution with heavy metal (Hakason,1980), through the following equation: (2) where (Cn) sample is the amount of heavy metal in the dust, and (Bn) background value is the amount of heavy metal.Hakanson (1980) divided the contamination factor (CF) into four categories, Table 3.

Pollution Load Index (PLI)
Pollution load index (PLI) is used to estimate heavy metal contamination sites in dust.The value of the PLI was determined using the following equation by Thomas et al. (1980).

PLI= √(N&CF1×CF2×CF3…CF) n
(3) Where N is the number of metals studied and CF is the contamination factor calculated in eq. ( 2)

Enrichment factor (EF)
The (EF) is a reference point to differentiate between natural and human metal sources and is calculated to assess the degree of contamination.EF was first calculated by (Bud-Menard and Chesselet in 1979) and calculated using the equation: Where (Cn/Fe) sample represents the ratio of heavy metals to iron in the dust of the field, and (Bn/Fe) sample represents the ratio of background metals to background reference metals.Because it is one of the geochemical metals distinguished by its abundance in the environment, Fe was chosen as a reference metal (Chandrasekaran et al., 2015).If the value of EF is less than 1, it means that heavy metals are produced by natural weathering or from raw materials, while if the value of EF is greater than 1, heavy metals are produced by industry or human activity.(Yang et al., 2019) Five pollutants are suggested for enrichment factors (EF) by (Sutherland, 2000) listed in Table 5.The potential ecological risk index is usually used to calculate the potential toxic effects of heavy metals on sediments, dust and soils (Hakanson 1980;Hu et al. 2018).This methodology provides a calculation of the harmful ecological effects of heavy metals in dust (Saeedi et al., 2012).This index can be calculated with the following equation: Where Er is the Ecological Risk Index of heavy metal, Ti is the toxic-response aspect for each of a given toxic metal (Zn= Mn=1, Cr=V=2, Ni=Pb=Cu=Co=5, Cd=30, and As=10).(Wang et al., 2018), Er is revealed as potential ecological risk, CF is referred as contamination factor.There are five categories of Er and four categories of RI listed in Table 6.

Health Risks Assessment
The U.S. Environmental Protection Agency (USEPA) methods were used to assess the risk of heavy metal cancer and non-cancer in the dust in the research area.The daily average dose of metals (ADD), ingestion, inhaled, and skin pathways is calculated using the following equations (USEPA 1996(USEPA , 2001)).7.

Non-carcinogenic risk assessment
To evaluate the risk of non-carcinogenic health from exposure to heavy metals from dust in the city of Erbil.The Hazard quotient (HQ), hazard index (HI) Calculated for studying heavy metal, the noncarcinogenic risk assessments (HQ) can be calculated by dividing the average daily dose of three routes (ADD) by the specific reference dose (RFD) (mg/kg daily) and (HI) by the summation of HQ for the three path ways as shown in the USEPA 1989 formula.

HI=∫HQ
(11) When the values of HQ and HI< 1, it refers that no significant risk of non-carcinogenic effects is occur.On contrary, there is a chance that non-carcinogenic effects may occur when HQ and HI >1, and the probability increase with increasing the value of HQ and HI.
The RFD Ing, RFDInh, and RFDDer values were obtained from Shabbaj et al. (2018) and Rahman et al. (2019) and listed in the Table 8 below.

Carcinogenic risk assessment
The risk of carcinogenesis is the probability that individuals will develop any type of cancer after exposure to carcinogenic hazards throughout their lives (Zheng et al., 2010).Calculated using the following equations (USEPA1989): Where ADD CA is the average daily dose for three pathways of exposure, (SF) is the cancer slope factor (mg•kg−1 day−1).TCR is the sum of carcinogenic risk (CR) for three pathways.In general, the USEPA recommends If CR, TCR <1 ×10-6 can be regarded as negligible, where CR, TCR>1×10-4 is likely to harmful to human beings.The acceptable or tolerable risk for regulatory purposes is within the range of 1×10 -6 -1×10 -4 .The cancer slope factor (SF) references used in this study are obtained from (Ferria-Baptista and De Miguel, 2005;Aminiyan et al., 2018) listed in Table 9.

Concentrations of Heavy Metal
The descriptive statistics for the heavy metals and the global soil average are presented in Table 10.The average concentration of heavy metals in dust collected in the study area exceeded the reference value except for V.The concentration of heavy metals in all samples is in descending order: Mn > Zn > Ni > Cr > Cu >V > Pb > Co > As >Cd.The values of Zn (45.55%),Pb (44.29%),As (34.51%), Cu (28.41%) and Cd (23.12%) are higher than those of Co, Cr, Ni, Mn, and V suggesting that these values may be affected by external factors such as anthropogenic activity (Shi et al., 2007).

Arsenic (As)
The concentrations of As in the research area range from 7.57 ppm to 27.30 ppm, with a mean value of 9.93 ppm.The As concentrations in dust collected from parks, residential areas, streets and industrial areas are descending in the following order: industrial > residential > street > park, (Fig. 3).Arsenic enters the environment through several human-related and agricultural activities, such as mining, metal smelting, fossil fuel combustion, and the use of agricultural pesticides.(Chung et al., 2014) 4. 1.2. Cadmium (Cd) 4.1.3.Cobalt )Co( The concentration of Co in the research area ranges from13.40 to 19.10 ppm, with a mean value of16.76 ppm.The Co concentration in dust collected from parks, residential, streets and industrial sites and take the following descending order park> residential> industry> street (Fig. 3).Cobalt enters the environment from natural sources and anthropogenic sources include the burning of fossil fuels, mining and smelting of cobalt ores, processing of cobalt blends, phosphate fertilizers, in industrial area which may be blown by wind and causes the elevation of the concentration of Co in other part of the study area (Zadnipyany et al., 2017).

Chromium (Cr)
The concentration of Cr in the research area ranges from 69 ppm to 95.20 ppm, with a mean value of 86.22 ppm.The Cr concentration in dust collected from parks, residential, streets and industrial sites take the following descending order: industrial> residential> Street> park (Fig. 3).Cr occurs naturally, being set up in different environmental divisions.Expansive use of Cr by industry for it several uses similar as tanning, textile dyeing, chrome plating, manufacturing of various alloys as corrosion inhibitions and wood treatment, probably the reason behind the elevation of its concentration in the study area (Zhitkovich, 2011).

Copper (Cu)
The concentration of Cu in the research area ranges from 39.90 ppm to 112 ppm, with a mean value of 63.51 ppm.The Cu concentration in dust collected from park, residential, street and industrial sites is taken in the following descending order: industry > street > residential > park, (Fig. 3).probably the elevation of concentration of Cu in these area due to both natural and anthropogenic sources, including brake peds of vehicles, exhaust from both gasoline and diesel-powered vehicles, and Cu is released during activities such as metal processing and melting in addition to being present in building materials (Aguilera et al., 2021).

Manganese (Mn)
The concentration of Mn in the research area ranges from 467 ppm to 599 ppm, with a mean value of 539.16 ppm.The Mn concentrations in dust collected from park, residential, street and industrial sites, and take the following descending order: Industry> street> residential> park (Fig. 3).The sources of Mn include the mining, manufacturing, and welding sectors; higher ambient Mn concentrations have been seen close to Mn-producing companies, despite Mn being naturally present in soil, rocks, and water.May be the reason behind elevation concentration of Mn is anthropogenic sources especially industrial activity and the traffic in these areas.(Wu et al., 2022).

Nikel (Ni)
The concentration of Ni in the research area ranges from 97 ppm to 136 ppm, with a mean value of 121.95 ppm.The concentrations in dust collected from park, residential, street and industrial sites and take the following descending order: Park> Residential> street> Industry (Fig. 3).Ni is widespread in the environment, by natural and anthropogenic sources.It is released into atmosphere from diesel oil, fuel oil and coal combustion, waste incineration, and fertilizer industry (Cempel and Nikel, 2006).

Lead (Pb)
The concentration of Pb in the research area ranges from 20.50 ppm to 90.50 ppm, with a mean value of 39.19 ppm.The Pb concentrations in dust collected from park, residential, street and industrial sites are listed in decreasing order as follows: Residential > street > park > industry (Fig. 3).even though only trace amounts of lead are found naturally.Road dust and soil that has been carried by the wind may contain lead that is present naturally as well as lead that has come from industrial sources such the production of leadacid batteries, burning leaded fuel, and the deterioration of paint (Sarker et al., 2023).

Vanadium (V)
The concentration of V in the research area ranges from 49.70 ppm to 68.50 ppm, with a mean value of 58.06 ppm.The V concentrations in dust collected from park, residential, street and industrial sites and take the following descending order: Park > Residential > street > Industry, Fig. 3. Vanadium is present in the atmosphere due to both natural and human-made causes.The natural source includes dust continental and volcanic emissions and marine atmospheric mist, as continental dust represents the largest source in the air, followed by marine aerosols, while volcanic emissions represent a small part compared to these two sources (Tchounwou et al., 2014) or released into surface environment through the combustion of fossil fuels, mining, and used of phosphate fertilizers (Orecchio et al., 2016).

Zinc (Zn)
The concentration of Zn in the research area ranges from 155 ppm to 696 ppm, with a mean value of 320.13 ppm.The Zn concentrations in dust collected from park, residential, street and industrial sites and take the following descending order as: Industry > street > residential > park, (Fig. 3).The largest humanmade sources of Zn are those related to metal production, including waste incineration, phosphate fertilizer use, consumption of fuel, and cement production.Other sources include brake linings and tire wear related to traffic, all of which may increase the concentration of Zn in the study area (Councell et al., 2004).

Igeo Accumulation Index
The outcome revealed that Ni> Zn > Cu > Cd > Co >Cr > As > Pb > Mn > V, Table 11. is the order of Igeo for all sites for the measured heavy metal in descending order.The dust collected from Park and Residential areas is classified by the Igeo category as being unpolluted for As, Cd, Cr, Cu, Mn, Pb, and V, while being unpolluted to moderately polluted for Co and moderately polluted for Zn and Ni.In dust collected from street locations, the Igeo category of As, Cd, Co, Cr, Mn, Pb, and V is unpolluted, but Cu is unpolluted to moderately polluted and Ni, Zn is moderately polluted.In dust collected from industrial locations, the Igeo category of Cr, Mn, and V is unpolluted, whereas As, Cd, Co, Cu, and Pb are unpolluted to moderately polluted, Ni moderately pollution and Zn moderately to high pollution.

Enrichment Factor (EF)
The obtained result shows the order of EF for the measured heavy metal in all sites as follows descending sequence: Zn> Ni> Cu> Cd> Co> As> Cr> Pb> Mn> V (Table 11).According to the classification of EF, the EF category of As, Cd, Co, Cr, Cu, Mn, Pb, and V, in dust collected from park, residential and street sites is deficient to minimal enrichment, while Ni is moderate enrichment and EF category for Zn is moderate enrichment in park and residential, while significant enrichment in street.The category for Co, Cr, Mn, and V in dust sample from industry sites deficiency to minimal enrichment, while As, Cd, Cu, Ni, Pb is moderate enrichment.The EF category for Zn is significant enrichment.

Contamination Factor (CF)
The current result of CF values for measured heavy metal in a dust sample in Erbil City is listed in Table 11.Exhibited that the contamination level with V is low contamination, while the contamination level by As, Cd, Co, Cr, Cu, Mn, and Pb is moderate, while the obtain result showed that dust samples are considerably contaminated by Ni and Zn.

Pollution Load Index (PLI)
The PLI value for all heavy metal in all sampling sites were more than 1.Based on the classification of Hakanson (1980), the sampling sites are polluted, as shown in Table 12.

Potential Ecological Risk (Er) and Risk Index (RI)
As listed in Table 11.ecological risk index Er of heavy metal (As, Co, Cr, Cu, Mn, Ni, Pb, V, Zn) is < 40 indicating to low potential ecological risk in all sites, while for the Cd metal indicating moderate environmental risk.The Risk Index (RI) for the studied heavy metal is < 150 indicating low ecological risk of heavy metal in dust in the study area (Table 12).13).
The obtained results showed that the ingestion pathway was the major exposure pathway of the majority of heavy metals children and adult followed by dermal pathway and inhalation pathway.The percentage of contribution to HI (Total risk of non-carcinogenic exposure) from HQIng, HQInh and HQDer in same order was 87%, 12% and 1% for children and 86%, 5% and 9% for adults indicating that ingestion was the main pathway exposure to the measure heavy metal in the dust of Erbil City for adults and children.The HIchildren is more than HIadult suggesting that children have more prevalence harmful effect from the heavy metals in the urban dust.The HQ and HI values are less than 1 (Table 13).indicating that there is no non-carcinogenic risk posed by the measured heavy metals on the adults and children in the selected study area.The values of the Cancer Risk (CR) and Total Cancer Risk (TCR) from exposure to As, Cd, Co, Cr, Ni, and Pb in dust were collected in the study area though ingestion, dermal and inhalation pathway and listed in Table 14.The result For CR in both inhalation and dermal pathway from all sampling sites of all heavy metal (As, Cd, Co, Cr, Pb, and Ni) for adult and child are all lower than the limit 1×10-6 Which indicate no significant carcinogenic health risk in study area, except CR dermal for AS child was acceptable or tolerated , CR ingestion for Cr and As both adult and children were between 1×10-4 and 1×10-6 shown tolerated or acceptable range , CR ingestion for Pb both children and adult were less than 1 ×10-6 which indicates to no carcinogenic health risk .TCR for As and Cr both children and adults shown tolerated or acceptable range, TCR for Cd ,Co, Pb, and both adult and children shown no significant health risk .

Conclusions
The mean value of As, Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn concentrations in dust collected from the leaves of the Eucalyptus plant in Erbil surpassed the reference value except V. (Igeo), (CF), (EF) indicates that the study area was unpolluted with most of the measured heavy metals and polluted with Ni and Zn.All heavy metals showed low ecological risk potential for (Er) except Cd, while (RI) indicates low ecological risk for all heavy metals.Ingestion was the most common method of exposure to both carcinogenic and non-carcinogenic heavy metals, followed by dermal and inhalation pathways.hazard quotient (HQ) and hazard index (HI) indicate all heavy metals have no non-carcinogenic effect.The cancer risk (CR) and total cancer risk (TCR) values for Cd, Co, Ni, and Pb were below permissible levels, whereas As and Cr were within acceptable ranges.
Where ADDIng, ADDInh and AD Dermal are the main daily absorption of metal (mg/kg.day)through ingestion, inhalation and skin absorption.The parameters values used to assess the health risk through different routes are listed in Table

Fig. 3 .
Fig. 3. Heavy metals of the dust samples from Erbil City.

Table 1 .
Coordinates of the collected dust samples in Erbil City Locations of the dust sampling sites in Erbil City.

Table 4 .
Classification grade of PLI.

Table 6 .
Ecological Risk factor (Er), and Potential Ecological Risk Index (RI) classification.

Table 7 .
The exposure parameters, used for health risk assessment through different exposure pathways * Value use for this particular research

Table 8 .
RFD values for non-carcinogenic risk of heavy metal for different exposure routes.

Table 9 .
SF values for carcinogenic risk of heavy metals.

Table 10 .
Descriptive statistics of heavy metals concentrations (ppm) in dust of the study area

Table 11 .
The descriptive statistics of values of Igeo, CF, EF and Er of heavy metals in dust of the study area.

Table 12 .
PLI and RI values of heavy metals in dust of the study area.The value of non-carcinogenic risk for heavy metals As, Cd, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn in dust from study area shows that the average hazard quotient (HQ) result for heavy metal to children and adult follow this descending order: As> Cr> Mn> Pb> V> Ni > Cu> Zn > Co> Cd for HQIng, Mn> Cr > Co> As> Cu> Pb> V> Ni> Zn> Cd for HQInh, and As > Cr > V > Mn > Pb> Cd > Ni > Zn > Cu > Co for HQDer.The Hazard index (HI) result takes the descending order As > Cr > Mn > Pb > V > Ni > Cu > Zn > Co> Cd for HIchildren, and As > Cr> Mn> Pb> V> Ni> Cu> Co> Zn > Cd for HIadult (Table

Table 13 .
Hazard quotient (HQ) and hazard index (HI) of heavy metals for children and adult

Table 14 .
cancer risk value (CR) and total cancer risk (TCR) of heavy metal for children and adult