Introduction

Air pollution consists of a mixture of particles, vapors, and gases (Geravandi et al. 2017; Goudarzi et al. 2017a). In recent years, anthropogenic air pollution, particularly development of industries (petroleum, gas, petrochemical), transportation, population growth, and dust storm (due to prolonged drought region) are the most critical factors threatening the humans and environment in Iran (Delfino et al. 2009; Dobaradaran et al. 2016; Elder et al. 2015; Fiala et al. 2001; Goudarzi et al. 2018; Hashemzadeh et al. 2017; Khaniabadi et al. 2017a; Neisi et al. 2016; Soleimani et al. 2013). Reducing its harmful effects and warnings to sensitive groups are one of the crucial government actions. Living in megacities with regard to breathing air pollutants can induce different health endpoints (Khaniabadi et al. 2017b). The consequences of air pollution on human health are a prominent issue addressed by several studies. Many studies conducted in cities across the USA, Europe, and Asia have reported the strong evidence regarding the deadly impact of air pollutants. Moreover, several recent studies have identified PAHs as a highly detrimental pollutant for human health (Chen et al. 2016; Goudarzi et al. 2017b; Liu et al. 2016). The main sources of emission PAHs are fossil-fuel combustion, petroleum refining, chemical manufacturing, coal, and dust storm (Alawi and Azeez 2017; Boonyatumanond et al. 2006; De Luca et al. 2005; Goudarzi et al. 2017b; Shen et al. 2014; Soclo et al. 2000; Wang et al. 2011). Some other studies state that the PAHs could increase ILCR in humans (Guerreiro et al. 2016; Hu et al. 2007; Kim et al. 2013; Pruneda-Álvarez et al. 2016; Tsai et al. 2001; Watanabe et al. 2009). Children are the most important group that can be influenced by PAHs’ exposure more than adults (Avagyan and Westerholm 2017; Chen and Liao 2006; Goudarzi et al. 2017b; Jerzynska et al. 2016; Oliveira et al. 2017; Perera et al. 2006). Allergic skin, thrombotic effects, decreased body weight, low IQ at age three, asthmatics, nausea, eye irritation, irritation, diarrhea, vomiting, impaired lung function, genotoxicity, and ILCR are the range of adverse health effects caused by PAHs’ exposure (Agency 2012; Alawi and Azeez 2016; Avagyan and Westerholm 2017; Balcıoğlu 2016; Boström et al. 2002; Chen and Liao 2006; Goudarzi et al. 2017b; Khaniabadi et al. 2017c; Kim et al. 2013; Kumar et al. 2016; Maragkidou et al. 2016; Tsai et al. 2001; Tseng et al. 2014). A series of studies have shown that smoking, inhalation, breathing exhaust fumes, and eating food contaminant are the primary factors transferring PAHs into the human body (Abdel-Shafy and Mansour 2016; Ali et al. 2016; Chetwittayachan et al. 2002; Hasanati et al. 2011; Hu et al. 2017; Kim et al. 2013; Oliveira et al. 2016; Rudel and Perovich 2009). Based on the report of an international organization, Ahvaz is one of the most polluted cities in the world. The pollution, of course, puts residents at risk of various health problems (Davar et al. 2014; Geravandi et al. 2015; Khaefi et al. 2016; Yari et al. 2016). In 2002, Boström et al. studied indicators, guidelines, and cancer risk assessment for PAHs (Boström et al. 2002). Furthermore, Chen et al. in 2006 assessed the exposure to environmental PAHs pollutants and its health risks for humans (Chen and Liao 2006). In a similar work, the quantification of carcinogenic risks related to the sources of particle-bound PAHs from Chengdu in China was studied by model-incremental lifetime cancer risk method (Liu et al. 2015). Moreover, Tseng et al. estimated the cancer risk attributed to incremental exposure to PAHs (Tseng et al. 2014).

Watanabe et al. in 2009, by epidemiologic data, compared ILCR computed for benzo[a]pyrene with lung cancer risk (Watanabe et al. 2009). Pankow et al. in 2007 evaluated risks of cancer for potentially reduced exposure product (Pankow et al. 2007). Alawi and Azeez in a wasteland in Iraq studied the effects of PAHs derived from Al-Ahdab oil field (Alawi and Azeez 2016). Kim et al. measured the level of airborne PAHs and its effects on human health (Kim et al. 2013). Furthermore, PAHs’ concentration in indoor dust samples in Kuwait and Jeddah was measured by Guirguis et al. (Ali et al. 2016).

In the previous study at animal scale lab, detrimental impacts of PM10 on many parameters including iNOS and eNOS mRNA expression levels, electrocardiogram parameters, blood pressure and oxidative stress were examined (Dianat et al. 2016a; Dianat et al. 2016b). The purpose of this study was to explore the association between cancer risk and PAHs originated from particulate in the ambient air of Ahvaz, southwest of Iran, during 2017.

Materials and methods

Methods

This cross-sectional study was carried out during 2017, in (S1) industrial, (S2) high traffic, and (S3) residential areas of Ahvaz. An active sampling system was used for measuring PAHs’ concentration within a specific period to cover autumn and winter.

Sampling

Samples were taken using Omni sampler (Bgi instruments USA Company; 231 model) equipped with polytetrafluoroethylene (PTFE) filters (8*10 in. Whatman, the USA) (Fig. 1). The flow rate of sampling was 5 l/s. Before sampling, the polytetrafluoroethylene was placed in an oven at 104 °C for 2 h.

Fig. 1
figure 1

Schematic of the sampling used in this study

Full size image

Standard preparation and analysis

Air sampling was carried out at the same time of the day before and 24 h. After sampling, each of chosen filter loading samples was divided into four parts. One fourth of the exposed PTFE filter was cut into pieces and put in a Teflon container. The concentrated extract was cleaned up using a florisil column, according to the NIOSH 5515 method (Hassanvand et al. 2015). At the next stage, a mixture of nitric acid %5, distilled water, 5 mL methanol (ratio of 1–1 V%), and 5 mL dichloromethane (ratio of 1–1 V%) was added to it. The resultant solution was stored in a clean and sterile plastic bottle at 4 °C until further analyses. Finally, 1.5 mL resultant solution was picked up and thrown in Vaile for injection of GC-MS (7890N, AGILENT & MS 5975C, MODE). A fused silica capillary column (HP5-MS 30 m × 0.25 mm × 0.25 μm) was used for separation. The injected volume for PAHs was 3 and 2  μL/splitless, respectively. The temperature program of the injector was 230 °C. Helium was used as a carrier gas at 1–2 mL/min. The oven temperature was programmed from 80 °C (held for 2 min) and raised to 285 °C @ 7 °C/min (held for 4 min).

Method validation procedure

A linearity regression function for PAHs in the air samples was set up according to calibration measurement. The good linearity was observed in the detected range. The correlation coefficients (R2) were found to be 0.99, 0.98, 0.94, 0.97, 0.98, 0.98, 97, 0.96, 0.96, 0.95, 0.99, 0.97, 0.98, 0.99, 0.99, and 0.99 for naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene, benzo[ghi]perylene, and indeno[1,2,3-cd]pyrene, respectively (Abdel-Shafy and Mansour 2016). In this study, the method of validation for analysis of urine samples was the limit of quantification (LOQ), determination of the limit of detection (LOD), precision, matrix effect, accuracy, recovery, and the calibration curve. The calibration curve showed a significant correlation with the linear regression profile (R2 = 0.99) (Abdel-Shafy and Mansour 2016). The average PAHs recovery efficiency ranged from 59 to 120%. In addition, the identification time of the 16 original combinations of PAHs ranged from 5.13 to 23.14 min. Moreover, the efficiency of PAHs recovery was extraction and analysis methods by determination of the standard deviation of 500, 1000, and 2000 μg/L spiked samples.

Description of study area

The experiment took place in three distinct areas of Ahvaz including industrial (31° 29′ N, 48° 72′ E), high traffic (31° 32′ N, 48° 69′ E), and residential areas (31° 42′ N, 48° 39′ E) (Geravandi et al. 2015; Goudarzi et al. 2015, 2016; Khaefi et al. 2017; Nashibi et al. 2017; Neisi et al. 2016). Locations of air samples are shown in Fig. 2.

Fig. 2
figure 2

Locations of air samples (S1: industrial, S2: high traffic, S3: residential)

Full size image

Estimation of incremental lifetime cancer risk (ILCR) due to polycyclic aromatic hydrocarbons

PAHs enter the body by ingestion, inhalation, and dermal contact and induce health risks. To determine ILCR, lifetime average daily dose was calculated for PAH-exposed adults (Agency 2012; Kaur et al. 2013). LADD and ILCR were calculated based on following equation (Kaur et al. 2013; Liu et al. 2015; Shen et al. 2014):

$$ LADD=\frac{C\times IR\times EF\times ED}{BW\times AT} $$
(1)
$$ ILCR= LADD\times \left\{ CSF\times \left(\frac{BW}{70}\right)\right.\times cf $$
(2)

where LADD is lifetime average daily dose (mg/kg/day); C is BaP exposure concentration (mg/m3); IR is inhalation rate (m3/day) (= 0.6 m3/h in this study); EF is exposure frequency (= 365 days/year in this study); ED is exposure duration (= 25 years for adults in this study); BW is body weight (kg) (= 50–70 kg in this study); AT is an averaging time (days) following US EPA (70 years or 25,550 days); CF is a conversion factor (10−3); ILCR is incremental lifetime cancer risk; and CSF is cancer slope factor (mg/kg/day)−1 (Kaur et al. 2013; Pankow et al. 2007; Shen et al. 2014; Tseng et al. 2014; Watanabe et al. 2009).

According to some studies and EPA report, the recommended amount of CSF for BaP by inhalation is 0.13 (Kaur et al. 2013).

Results

The characteristics of PAHs

This study assessed the PAHs’ exposure-associated cancer risk among individuals living in three distinct areas of Ahvaz, southwest of Iran, during 2017. The total of 16 PAHs (naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, pyrene, fluoranthene, benzo(a)ant, chrysene, b(b)f, b(k)f, b(a)p, dbenzo[ah]anthracene, indeno[123 cd]pyrene, and benzo[ghi]perylene) in the outdoor air of Ahvaz are shown in Table 1.

Table 1 Level of PAHs in three distinct areas during winter and autumn
Full size table

Based on World Health Organization (WHO) report, the standard inhalation rates of benzo(a)pyrene and other PAHs for general population living in residential, high traffic, and industrial areas are 0.4, 0.7, and 1.5 ng m−3, respectively (Abdel-Shafy and Mansour 2016; Harrison et al. 2009; Lioy et al. 1988; Organization 2010). In this study, the lowest and highest levels of PAHs were observed in residential and industrial areas (Table 2). In addition, the average levels of PAHs in industrial, high traffic, and residential areas were 8.44 ± 3.37, 7.11 ± 2.64, and 5.52 ± 1.63 ng m−3, respectively (Table 2).

Table 2 Distribution of PAHs (ng/m3) in outdoor air in autumn and winter, according to the locations
Full size table

The concentration of 16 PAHs varied in a range of 1.84 to 14.76 ng m−3 (mean 7.02 ng m−3). In addition, B(k)F and anthracene had the lowest and highest average concentration (Table 2).

Incremental lifetime cancer risk

Carcinogenic and mutagenic effects of BaP, the best known of PAHs, have been already investigated (Nisbet and LaGoy 1992; Tseng et al. 2014). In a dose-response relationship of risk assessment, toxic equivalency factors (TEFs) are used for various pollutants to a given well-known toxic chemical (Nisbet and LaGoy 1992; Van den Berg et al. 1998). The relative carcinogenic effects of 16 typical PAHs have been estimated by TEFs. Cancer risk for a 70-year lifetime exposure is estimated through combining the unit risk of BaP, 8.7 × 10–5 (ng/m3)−1, and the corresponding PAHs in the target environments (Liu et al. 2015; Tseng et al. 2014).

Different amounts of BaPeq (TEQ) (ng/m3) (average amount in warm-cold seasons), ILCR, and LADD in adults were calculated based on the level of PAHs in industrial, high traffic, and residential areas, as summarized in Table 3. Incremental lifetime cancer risk is the first attempt that evaluated the potential cancer risk of human exposure to polycyclic aromatic hydrocarbons in the ambient air by using three different TEQ methods. Human activities and exposure to PAHs in urban region lay an important role in governing potential cancer risk of the human. In this study, the average values of ILCR of individuals living in three distinct areas of Ahvaz as estimated by three different TEQs were 6.7 and 8.9, for autumn and winter, respectively (Table 3).

Table 3 BaPeq (TEQ), LADD, and ILCR for the autumn and winter season
Full size table

Figures 3 and 4 present the level of BaP concentration in industrial, high traffic, and residential areas during warm-cold seasons. From these findings, poor air quality condition in Ahvaz is due to the higher BaP concentration compared to WHO guideline (1 ng/m3).

Fig. 3
figure 3

Comparison of the level of Bap concentration with standard level in industrial, high traffic, and residential areas during the winter

Full size image
Fig. 4
figure 4

Comparison of the level of Bap concentration with standard level in industrial, high traffic, and residential areas during the autumn

Full size image

Discussion

This study explored the association between cancer risk and the PAHs’ concentration in the ambient air of Ahvaz, southwest of Iran, during 2017. As a result of production and emission of air pollutants, particularly PAHs, from industries and vehicles, health endpoints such cardiovascular disease, repository disease, and cancer risk are increasing among people living in industrial cities. Consequently, closer attention to decrease air pollutants through viable solutions is of the essence. All survey participants, living in three distinct areas of Ahvaz, were exposed to a higher level of PAHs compared to WHO air quality guidelines and region standard values (Abdel-Shafy and Mansour 2016; Harrison et al. 2009; Lioy et al. 1988; Neisi et al. 2016; Organization 2010; Tchounwou et al. 2012; Zhang et al. 2014). The high concentration of PAHs may occur when using them as a catalyst in oil, gas, and petrochemical industries. In addition, the petrogenic and pyrogenic sources of PAHs could be the reason for PAHs’ variations in ambient air of Ahvaz. The higher this ratio, the greater the contributions from combustion phenomena (oil, coal, gasoline, and gas oil) in the formation of these compounds. Balcıoğlu et al. studied the potential effects of PAHs in marine foods on human and suggested it as a risk for human health (Balcıoğlu 2016). Our study results, as well, identified PAHs as a substantial threat to human. Similar to our study, Rezaei et al. observed a higher level of exposure to PAHs during the cold season (Rezaei et al. 2015). It is worth mentioning that the temperature inversion occurs predominantly in autumn and winter and also demand sharply rises for heating fuels, crude oil, and natural gas in cold season, ultimately leading to higher refinery operation as well as higher level of PAHs’ concentration emission.

To evaluate the health risk of PAHs, BaP (BaPeq) method was used. Consequently, BaPeq (TEQ) was calculated by multiplying toxic equivalency factors (TEFs) in each PAH component. The total levels of BaP in winter and autumn were found to be 8.96 and 6.702 ng/m3, respectively. Moreover, BaP (about 76% of total BaP concentration) has the highest level of BaPeq (Table 3). The source and distribution of BaP are quite diverse. The assessment of ILCR of PAHs is mainly based on laboratory tests and epidemiologic work. ILCR and LADD for adult residents of Ahvaz in warm-cold seasons are given in Table 3. ILCR in autumn and winter, in our study, was 0.04718 and 0.06307, respectively. According to EPA guidelines, the acceptable ILCR is considered to be between 0.0001 and 0.00001 (Tseng et al. 2014; Watanabe et al. 2009). The results of this study disclosed the importance of ILCR and showed the higher ILCR than EPA guidelines among our study participants. In addition, results showed that people living in industrial and high traffic areas had higher ILCR compared to those living in a residential area; however, a comprehensive epidemiologic study is required to affirm our study results. The lower ILCR than EPA standard in China has been reported (Liu et al. 2015). Furthermore, a substantially higher ILCR (0.00435) than EPA standard has been reported for carbon black manufacturing workers exposed to PAHs (Tsai et al. 2001).

The comparison of the present study to the present existing studies and guidelines reveals that the city of Ahvaz due to its neighborhood and affiliation with the oil, gas, petrochemical, steel, and piping industries have a high concentration of air pollutants, particularly PAHs, which can increase ILCR as well as various health hazards among residents.

Limitations and strengths

We ran the study for two seasons just because of limited time for instruments. Observed trends may not be representative of a wider population because this study had a small sample size. Therefore, further studies should be implemented to investigate all areas of Ahvaz as well as other industrial cities in a longer period. Also, we can reduce citizenship exposure to hazardous contents of particulates by compressive enterprises in the field of industries and transportation patterns.

Conclusion

Health endpoints associated with exposure to noxious pollutants, particularly PAHs, are increasing among residents of large industrial cities, underlining the pressing need for governmental action to decrease the level of those health-threatening pollutants. Results showed that average amount of heavy metal was 7–8 times higher than the standard value. In addition, it appears reasonable to the high levels of PAHs observed in Ahvaz, Iran, were attributed to petroleum and gas industries, demographic, and climate characteristics of this city. The high concentration of PAHs in the air of large industrial cities primarily arises from industrialization, urbanization and climate change, and high consumption of fossil fuels.

Finally, careful monitoring, application of modern automobiles, developing the green area, and controlling the emission of PAHs will have important impacts on decreasing amount of these dangerous pollutants.