A comprehensive study of human risk associated with PAHs in fish and sediments in Bushehr, north of the Persian Gulf

Description and sampling of the study area

To determine PAH pollution in Bushehr Province, a comprehensive study was conducted on sediment and Indian halibut samples. For this purpose, five cities and islands with high levels of oil pollution and industrial activities (petrochemical and gas industries) were selected throughout Busher Province in southeastern Iran. In general, a total of 20 samples were randomly collected from 20 different stations along the coast of Bushehr province from January 2019 to February 2019, including Asaluyeh, Kangan, Khark, Emam Hasan and Bushehr (Fig. 1). The geographical location of selected stations is shown in Fig. 1. The sediment samples were collected based on a five-point sampling approach with a length of 10 m. Briefly, at each station, five sediment samples were collected from four corners and the center with a depth of 5 cm. Generally, 3 kg of sediment samples were immediately placed in a precleaned glass container with a polytetrafluoroethylene screw cap and immediately transported to the laboratory.

The fish samples were 20 native fish samples, which are among the most commercially exploited fish along the Persian Gulf coast, and were caught by trawling in various cities and islands mentioned above. The fish samples were immediately stored in a cooler and taken to the laboratory for further analysis. The fish samples were then washed with distilled water and prepared to extract PAHs from their edible parts. The edible parts of the fish samples were then placed in the oven at 80 °C for 18 hours. The dried samples were pulverized for PAH extraction and further analysis¹⁹.

PAH extraction from sediment and fish samples

The extraction of PAHs from sediment samples was carried out according to the following procedure: 250 mL of dichloromethane-n-hexane (1:1) was added to 10 g of each freeze-dried sediment and then the mixture was placed in a Soxhlet for 8 h. The residue was concentrated to 15 ml using a rotary evaporator. To remove sulfur, active copper (2-3 g) was added to the residue and the mixture was filtered for 24 hours. The residue was passed from a column containing 10 g of silica, 10 g of active alumina and 2 g of anhydrous sodium sulfate. The mixture was again concentrated to 5 ml and poured into graduated vials. Once the solvent was completely evaporated, 1 mL of acetonitrile was added to the sample for high-performance liquid chromatography (HPLC) injection²⁰. In the case of PAHs in fish samples, 5 g of dried edible part of Indian halibut was carefully mixed with 5 mL of KOH (50%) and 75 mL of methanol. The mixture was placed in a Soxhlet for 4 hours. After transferring the liquid phase to the separatory funnel, 100 mL of n-hexane was added and shaken vigorously for 3 minutes. The methanol-KOH solution was evacuated and then the hexane phase was also washed with 50 mL of methanol-water solution (8:1) and 50 mL of water. Samples were passed from the column and contained 15 g of silica, 10 g of active alumina and 1 g of anhydrous sodium sulfate. 1 mL of n-hexane was added to each sample to prepare for further analysis and gas chromatography (GC) analysis.

Analytical analysis

The measurement of various PAH components in the samples was carried out using gas chromatography-mass spectrometry (GC 6890, AGILENT, MS 5973N, mode EI, detector:MS).

In general, the concentrations are 16 different aromatic compounds: acenaphthylene, naphthalene, acenaphthene, phenanthrene, anthracene, fluoranthene, fluorene, pyrene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)anthracene, benzo(a) pyrene, indeno(1,2,3,cd)pyrene, benzo(ghi)perylene, dibenz(a,h)anthracene were analyzed according to the EPA method at 350°C²¹ and National Standard of Iran (19,238)²².

Risk assessment

The daily dietary intake (DDI) values of PAHs from Indian halibut ingestion were calculated assuming an average weight of 70 kg for adults using Eq. estimated. (1)¹¹,

$$ {\text{DDI }}\left( {{\text{mg}}/{\text{Tag}}} \right) \, = {\text{ Ci }} \times {\text{ IR} }, $$

(1)

Ci is the PAH concentration in mg/kg and IFR is the intake rate (kg/day). The toxicity and carcinogenicity of the high molecular weight PAHs compared to BaP were determined by the toxicity equivalent quotient (TEQ). This quotient is related to the value of each congener that causes a change in the human DNA. The carcinogenic BaP equivalent (TEQ) for the individual PAHs in sediment and fish samples was calculated according to Eq. calculated. (2)¹⁹.

$$ {\text{TEQ }} = \, \sum {\left( {{\text{TEFn }} \times {\text{ Ci}}} \right)} , $$

(2)

where Ci = concentration of the individual PAHs in the sample sediments and Indian halibut (mg.kg).^-1 dw) and TEFn is the toxic equivalence factor for individual PAHs.

The incremental lifetime cancer risk (ILCR) assesses the health risk from exposure to PAHs according to the USEPA standard. The main routes of human exposure to sediment PAHs include (a) inhalation, (b) ingestion, and (c) skin contact, with the age groups being children (1–11 years) and adults (18–70 years). The following equations: (3), (4), (5) were applied to evaluate the incremental lifetime cancer risk (ILCR) from PAHs in the sediments²³.

$${\text{ILCR}}\left({\text{Ingestion}}\right)= \frac{\sum TEQ . \left\{{CSF}_{ingestion} ({BW/70)}^\frac{1}{3}\right\}. ED. EF. {IR}_{Recording}}{BW . AT . {10}^{6}},$$

(3)

$${\text{ILCR}}\left({\text{Inhalation}}\right)= \frac{\sum TEQ . \left\{{CSF}_{Inhalation} ({BW/70)}^\frac{1}{3}\right\}. ED. EF. {IR}_{Inhalation}}{BW . AT . BEF},$$

(4)

$${\text{ILCR}}\left(\mathrm{Skin Contact}\right)= \frac{\sum TEQ . \left\{{CSF}_{\mathrm{Dermal \,\,contact}} ({BW/70)}^\frac{1}{3}\right\}. SECTION . AF. SAT. EF. ED}{BW . AT . {10}^{6}}.$$

(5)

Furthermore, the increased cancer risk of PAHs due to Indian halibut ingestion was estimated using Eq. estimated. (6)¹¹.

$$ {\text{Excessive cancer risk }}\left( {{\text{ECR}}} \right) \, = \, \Sigma {\text{Q }} \times {\text{ B }}\ left ( {\text{A}} \right){\text{ Pteq }} \times {\text{ IFR }} \times {\text{ ED}}/\left( {{\text{BW }} \ times {\text{ ATn}}} \right). $$

(6)

The human risk model parameters in the sediment and Indian halibut samples are listed in Tables 1 and 2, respectively.

Table 1 Components of the health risk model on the sediment samples.

Table 2 Parameters of the health risk model in the Indian halibut samples.

Data analysis

The SPSS-23 software was used to statistically analyze the results. Results were presented as mean ± standard deviation (SD). The correlation between the data was tested using Pearson correlation coefficient and analysis of variance (ANOVA). The value of P < 0.05 was significant.

Ethics statements

We declare that this study was carried out in accordance with the ARRIVE (Animal Research: Reporting of In Vivo Experiments) guidelines and in compliance with its basic principles and guidelines. We followed the necessary steps outlined in the ARRIVE guidelines to minimize suffering and ensure appropriate care and welfare of the laboratory animals. We have described the methods and procedures of the animal experiments in detail and comprehensively reported relevant statistical analyzes and data. The method of this study was approved by the Ethics Committee of Bushehr Branch, Islamic Azad University, Bushehr, Iran, and the animal experiments were approved by the Ethics Committee of Bushehr Branch, Islamic Azad University, Bushehr, Iran (16-11 8458 , 1400/02/05).