Introduction

In recent years, the environmental pollution by heavy metals has increased. Rapid industrial development, especially in developing countries, has caused serious soils contamination around the industries (Fakhri et al. 2018). Generally, heavy metals may release to the environment through industrial activities, fertilizers, pesticides, solid waste disposal, irrigation with effluents, sludge application, and automobile exhausts (Qasemi et al. 2018a, b; Kamani et al. 2017; Princewill and Adanma 2011; Afsharnia et al. 2018). Cement factories are one of the most common sources of pollutants including heavy metals. Actually, cement factories mainly contribute to environmental pollution by heavy metals through the emission of cement dusts and various gasses (Adejoh 2016; Maina et al. 2013; Rezaeian and Moghadam 2016). According to the studies, cement dust is a major source of released heavy metals and one of the most important sources of surrounding soil pollution in different countries, especially developing countries (Addo et al. 2012; Mandal and Voutchkov 2011). The most common metals in cement dust are Al, Be, Cr, Cu, Mn, Ni, Zn, As, Cd, Pb, and Hg (Adejoh 2016). Based on the findings of Khashman and Shawabkeh, the concentrations of Pb, Zn, and Cd were significantly higher in soils around the cement factory (Al-Khashman and Shawabkeh 2006). The results of Semhi et al. study also showed that the concentrations of heavy metals in the radius of 500–2000 m around a cement factory were higher (Hong-gui et al. 2012; Semhi et al. 2010). High accumulation of heavy metals in agricultural soils around a cement factory may result in increase of heavy metal uptake through food crops consumption and a great concern of potential health risk to human (Adejoh 2016). Pollution index methods for heavy metals have been widely used to evaluate the soil health quality (Zhong et al. 2010). The main objective of this study was to evaluate the soil pollution to heavy metals around a cement factory with geo-accumulation index (Igeo), pollution index (PI), and integrated pollution index (IPI) and to assess the related health risk.

Materials and methods

Study area

Doroud cement factory is located in southwest of Iran at Lorestan province (33˚29ʹN; 49˚4ʹE). Actually, the factory is located in the city centre and adjacent to residential areas. Figure 1 shows the location of the factory. The factory has three main units, which were established in 1959, 1969, and 1989, respectively. Also, the nominal capacity of cement production in these units is 400 ton/day, 1000 ton/day and 2500 ton/day, respectively. These units work in a dry method and can produce type I, type II, and type IV cement (Farhadi et al. 2017; Nourmoradi et al. 2016).

Fig. 1
figure 1

Location of Doroud cement factory

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Sample collection and preparation

All soil samples were taken around the cement factory at the direction of the dominant winds. Based on other studies, sampling was performed at intervals of 500 m, 1250 m, and 2000 m from the main factory site (Addo et al. 2012). Soil samplings were taken from depths of 0 to 10 cm and 10 to 20 cm from the soil surface. Before measuring the concentration of heavy metals, the samples were digested using an acidic solution (HCl: HNO3, in a 1:3 volume ratio) (Okoro et al. 2017) and prepared (Princewill and Adanma 2011). For digestion, 1 g of each soil sample was added to 10 ml nitric acid and 3 ml chloric acid and then heated until boiling. After that, the soil solution was prepared by processing the residue with 4 ml of hot HCl (5 Molar). The digested was filtered into 50 ml volumetric flask and diluted with double-distilled water. A triplicate digestion of each soil sample was carried out. A blank (digest without the soil sample) was also used to remove the errors relating to possible materials and method. Finally, the concentrations of heavy metals in the solution were quantified using an ICP-OES (Instrument Model: Varian VISTA-MPX) (Kamani et al. 2017).

Indices to assess soil enrichment with heavy metals in the study area

Generally, to assess the status the soils, there are several indices. Table 1 shows the most important indices for describing the soil contamination to heavy metals. There are two common ways to monitor a soil in terms of enrichment: Igeo and EF (Kamani et al. 2017; Qingjie et al. 2008). Igeo was developed by Müller indicating the degree of soil contamination. Muller has considered six classes for Igeo (Muller 1969) as shown in Table 1. There are two important indices describing the quality of the soil environment including PI and IPI (Malkoc et al. 2010). In this work, these indices were applied to assess the degree of metal pollution around the cement factory. Both these indicators have four degrees of pollution (Table 1).

Table 1 Formulas used in this study (Rezaei et al. 2018; Ghaderpoori et al. 2018a, b; Chen et al. 2005; Hosseini et al. 2016; Ravankhah et al. 2016; Wan et al. 2016)
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Health-risk assessment

The health-risk assessment of heavy metals in the soil is a multi-step process and categorized into carcinogenic and non-carcinogenic effects (Qasemi et al. 2018a, b; Ghaderpoori et al. 2018a, b; Jafari et al. 2017). In both the carcinogenicity and non-carcinogenicity risk assessments, all three routes of human exposure to heavy metals (i.e. oral ingestion, inhalation, and dermal absorption) are considered. In this work, the health-risk assessment of the heavy metal in the soil was evaluated based on the USEPA method (Keramati et al. 2018; Karim 2011; Ravankhah et al. 2016). The equations used to calculate the health-risk assessment are shown in Table 1. The input variables and their values for calculating the health-risk assessment through oral ingestion, inhalation, and dermal absorption are also presented in Tables 2 and 3, respectively.

Table 2 Parameters applied in exposure assessment model (Wan et al. 2016)
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Table 3 The reference RfD and SF of heavy metals (Wan et al. 2016)
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Statistical analysis

Data obtained in this study were evaluated using statistical analyses to determine the distribution of data obtained from One-Sample Kolmogorov–Smirnov test. Determination of the relationship between heavy metals concentration and distance from the source of contamination was performed using Analysis of variance (ANOVA).

Results and discussion

The results of measuring the concentration of heavy metals based on the distance from the source and the sampling depths are shown in Table 4. The results showed that the average concentrations of chromium, nickel, copper, lead and zinc in the top soil around the cement factory were 115.77, 139.07, 80.47, 56.27, and 135.73 mg/kg, respectively. In this study, the highest concentration was related to nickel. Also, the results showed that the concentration of heavy metals in the soil top layer, 0–10 cm, was significantly higher than that of the depth of 10–20 cm, (Pvalue< 0.05). The findings of Olowoyo et al. showed that the concentration of heavy metals measured at depth of 0–15 cm is higher than that of depth of 15–30 cm (Olowoyo et al. 2015). Also, the Khashman et al. results showed that the concentration of heavy metals, especially zinc metal, was higher at the yaer of 0–19 cm, in the soils around a cement factory (Kashem et al. 2007). The results of Okoro et al. showed that in the soil around a cement factory in Ewekoro, the order of mean concentrations of the heavy metals content in the three soil samples was Fe > Zn > Mn > Cr > Cu > Pb (Okoro et al. 2017). Based on the results of these studies, it can be said that the existence of industries such as the cement plant can significantly increase the concentration of heavy metals in the surrounding soil. Similar results were reported by Mandal et al. and Princewill et al. (Mandal and Voutchkov 2011; Princewill and Adanma 2011). The findings of Addo et al. indicated that the concentration of most heavy metals was above the background and critical limits for soil and vegetation, respectively (Addo et al. 2012). To understand the complexity of the distribution of heavy metals in the soil around the cement factory, mathematical models of geo-accumulation index, pollution index, and integrated pollution index were applied (Addo et al. 2012). The results of the various calculated indices are shown in Table 5. The results of the geo-accumulation index are shown in Table 5A. The Igeo mean values for Cr, Cu, Ni, Pb, and Zn in the soil around the cement factory were − 0.31, 0.1, 0.14, 0.54, and 0.06, respectively. The lowest and highest average values of Igeo were calculated for Cr and Pb, respectively. According to Table 1, Igeo classification for Cu, Ni, Pb, and Zn was as uncontaminated to moderately contaminate. Igeo classification for Cr was uncontaminated. The findings of this study showed that Igeo classification for the soil samples varies from metal-to-metal and site-to-site. These changes were also reported in Okoro et al. (Okoro et al. 2017). In the present work, to further assess the contamination levels of the heavy metals, the pollution index and the integrated pollution index were also used. The results of the calculated PI and IPI in the soil around the cement factory are illustrated in Table 5B. The PI mean values for of Cr, Cu, Ni, Pb, and Zn were 1.26, 4.97, 1.71 to 3.31, and 2.03, respectively. The lowest and highest mean values of PI were for Cr and Cu, respectively. According to Table 1, PI classifications for Cr, Cu, Ni, Pb, and Zn were moderate, considerable, moderate, considerable, and moderate, respectively.

Table 4 The concentration of heavy metals based on the distance from the source and the sampling depth
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Table 5 Assessment of pollution levels of heavy metals based on different indices
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The results of One-Sample Kolmogorov–Smirnov test showed that the concentration of heavy metals measured around the cement factory has a normal distribution (Pvalue > 0.05), so that the parametric tests were used for its analysis. Table 6 presents the results of the ANOVA test. Based on Table 6, there is a significant relationship between the concentrations of Pb, Cr, Ni, Zn, and Cu with distance from the source of pollution (cement factory).

Table 6 The results of the ANOVA test
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Health-risk assessment relating to soil metals was conducted in two parts of non-carcinogenicity and carcinogenicity effects. The daily intakes of heavy metals in ingestion, inhalation, and dental contact pathways are shown in Table 7. The concentration of heavy metals in one region depends on various factors. Industry type is one of the most important soil contamination factors in a region and the degree of contamination varies based on industry activity. From environmental point, cement factory is one of the most important industries that can adversely affect the environment and human health (Darivasi et al. 2016). The rate and degree of contamination to heavy metals may also change significantly by the distance from the main factory site. Olowoyo et al. showed a significant difference in the concentrations of heavy metals in different directions (Olowoyo et al. 2015). The results of present study showed that the dominant wind direction has the highest concentration of heavy metals in the soil top. According to the USEPA standard, the background concentrations of Cr, Cu, Ni, Pb, and Zn are 100, 30, 40, 888, and 50 mg/kg, respectively. Comparing the results of this study with USEPA standard, it was revealed that the concentrations of all the measured metals were higher. Therefore, health-risk assessment studies should be considered. The results of Darivasi et al. showed that the concentration of heavy metals in soil around Neka cement factory was higher than the standard values (Darivasi et al. 2016). As the distance from the factory increased, the concentration of heavy metals was significantly reduced. Therefore, the highest concentration is always observed around the factory. The daily intakes of heavy metals via ingestion, inhalation, and dental contact pathways are shown in Table 7. In ingestion pathway, the highest and lowest daily intakes of metals were found for Zn (9.44 × 10− 6 mg/kg) and Pb (3.82 × 10− 6 mg/kg). In oral inhalation pathway, for non-carcinogenicity, the highest and lowest daily intakes of metals were found for Cu (1.39 × 10− 9 mg/kg) and Pb (5.62 × 10− 10 mg/kg). In inhalation pathway, for carcinogenicity, the highest and lowest daily intakes of metals were for Cu (9.92 × 10− 10 mg/kg) and Pb (4.01 × 10− 10 mg/kg). In the dermal contact pathway, the highest and lowest daily intakes of metals were found for Zn (2.88 × 10− 7 mg/kg) and Pb (1.16 × 10− 7 mg/kg). Based on the results, the daily intake rate of all the elements in the oral ingestion route was greater than the inhalation and dermal contact. The mean of daily intake rates of metals for all the three pathways for Cr, Cu, Ni, Pb, and Zn was 8.1 × 10− 6, 9.73 × 10− 7, 5.63 × 10− 6, 3.94 × 10− 6, and 9.5 × 10− 6, respectively. To evaluate the non-carcinogenic health effects of heavy metals, HQ was determined. If HQ is greater than 1, it reflects harmful health effects on human health (Karim 2011). The HQ values of heavy metals by oral ingestion, inhalation, and dental contact pathways are shown in Table 8. Based on the results (Table 8), the HQ value of all metals in all studied sampling points was less than 1. In the ingestion pathway, the highest and lowest daily intakes of metals were found for Cr (2.62 × 10− 3 mg/kg) and Zn (3.07 × 10− 5 mg/kg). In the inhalation pathway, the highest and lowest daily intakes of metals were found on Cr (4.04 × 10− 5 mg/kg) and Zn (4.52 × 10− 9 mg/kg). In the dermal contact pathway, the highest and lowest daily intake of metals was found for Cr (3.99 × 10− 3 mg/kg) and Zn (4.68 × 10− 6 mg/kg). Based on the results, the HQ values of all the elements in the ingestion route were greater than the inhalation and dermal contact. The mean of HQ values of metals for the total of three pathways for Cr, Cu, Ni, Pb, and Zn was 6.65 × 10− 6, 2.6 × 10− 4, 3.04 × 10− 4, 1.31 × 10− 3, and 3.54 × 10− 5, respectively. The results of the non-carcinogenicity health-risk assessment, HI, for the total three pathways for each individual metal are shown in Table 8. Some heavy metals, in addition to non-carcinogenic effects, can also have carcinogenic effects such as Cd, As, Cr, Ni, and Co (Kamunda et al. 2016). The HI index is used to calculate the carcinogenic effects of heavy metals (Table 1). The HI value ranges for chromium and nickel were 1.9 × 10− 8–5.88 × 10− 8 and 6.65 × 10− 6–2.6 × 10− 4, respectively. According to the results of this study, the carcinogenic risk of chromium and nickel was less than 1 × 10− 6. The findings of Chabukdhara et al. study showed that in an industrial soil sample, the highest HI value was related to chromium, nickel, lead and cadmium (Chabukdhara and Nema 2013). The risk of carcinogenicity of the heavy metals was less than the recommended limit set by the USEPA. The results of the health-risk assessment of heavy metals in the surface soil of the study area reflect the fact that the risk of carcinogenicity of these metals provides serious doubts about the health of children and adults. Despite the fact that less attention has been paid to the entry of heavy elements through inhalation, oral ingestion, and dermal contact, these routes can be very important and have high potential risk (Ravankhah et al. 2016). In short, in this research the health-risk assessment of heavy metals in the soil top around the cement factory was carried out by the proposed method of the US Environmental Protection Agency. This method generally identifies the potential health risks and the high risk of health that does not imply a health hazard and, if there is spatial data on health hazards at large scale, it may be possible to check their compliance with the health risks assessment.

Table 7 The daily intake of heavy metals in ingestion, inhalation, and dental contact pathways
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Table 8 The HQ values of heavy metals in ingestion, inhalation, and dental contact pathways
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Conclusion

In this study, the health-risk assessment of heavy metals in the soils around the Doroud cement factory was studied. Both carcinogenic and non-carcinogenic effects were investigated. All calculations were performed based on the proposed method of the US Environmental Protection Agency. All samplings were performed at intervals of 500 m, 1250 m, and 2000 m. Soil samplings were taken from depths of 0–10 cm and 10–20 cm. To assess the condition of the soil, there were several indices such as geo-accumulation index, pollution index, and integrated pollution index. The study results showed that the concentration of heavy metals in the soil top was significantly higher than that of the lower depths of soil. The results also showed that the dominant wind direction affected the high concentration of heavy metals in the soil top around the plant. Comparison of heavy metal concentrations measured in this study with US EPA standard showed that concentrations of all metals were higher than the standard. Based on the results, the HQ values of all the elements intakes via ingestion route were greater than the inhalation and dermal contact pathways. The mean of HQ values through all three pathways for Cr, Cu, Ni, Pb, and Zn was 6.65 × 10− 6, 2.6 × 10− 4, 3.04 × 10− 4, 1.31 × 10− 3, and 3.54 × 10− 5, respectively. According to the results of this study, the carcinogenic risk of chromium and nickel was less than 1 × 10− 6.