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Int J Env Health Eng 2022,  11:19

Cancer and Noncancer Risk Assessment for Workers Exposed to the Chemical Pollutants in Ahvaz Gas Stations, Iran

1 Department of Occupational Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran; Department of Health, Safety, and Environment, OICO Occupational Health Expert, Azar Oilfield, Ilam, Iran
2 Department of Occupational Health and Safety at Work, School of Public Health and Safety, Shahid Beheshti University of Medical Sciences, Tehran, Iran
3 Department of Occupational Health Engineering, School of Public Health, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran
4 Department of Toxicology and Pharmacology, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
5 Department of Epidemiology and Biostatistics, School of Public Health, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran

Date of Submission31-Jan-2022
Date of Decision11-May-2022
Date of Acceptance28-May-2022
Date of Web Publication13-Dec-2022

Correspondence Address:
Dr. Farideh Golbabaei
Department of Occupational Health Engineering, School of Public Health, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijehe.ijehe_5_22

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Aim: This article evaluates the health risk of occupational exposure to BTEX compounds, cancer risk, and noncancer risk analysis among gas station workers. Materials and Methods: This cross-sectional research evaluates pollutants rank of risk released at Ahvaz stations in Iran. We have collected 96 samples of workers exposed to BTEX and eight samples for control in the ambient air. The National Institute for Occupational Safety and Health (NIOSH) recommended BTEX method numbers 1500 and 1501 for sampling and analysis. To evaluate the risk assessment of pollutants, we utilized a semi-quantitative method offered by Singapore's Occupational Safety and Health Division. Results: The average benzene concentration in the operators' breathing zone (1.202 0.83 ppm) was greater than the threshold limit values-time weighted average (TLVs-TWA) (P < 0.05). Other contaminants had concentrations that were lower than the ACGIH's TLV-TWA (P < 0.05). In gas stations, benzene has a very high danger ranking among chemical compounds. Toluene, ethyl benzene, and xylene in the employees' breathing zone posed a modest risk. The average cancer risk for benzene-exposed operators, head shift workers, and supervisors was calculated to be 4.46 × 10−3, 2.90 × 10−3, and 2.08 × 10−3, respectively. The risk of cancer is projected to be higher than the tolerable level of 10-6. Conclusion: In unique, long-term exposure to benzene has been linked to an increased risk of cancer and toxic effects, and a health-risk assessment can provide useful information about current workplace contaminants.

Keywords: Benzene, BTEX, cancer risk assessment, gas station, risk analysis, volatile organic compounds

How to cite this article:
Askari A, Abadi AS, Golbabaei F, Jafarzadeh E, Aazam K. Cancer and Noncancer Risk Assessment for Workers Exposed to the Chemical Pollutants in Ahvaz Gas Stations, Iran. Int J Env Health Eng 2022;11:19

How to cite this URL:
Askari A, Abadi AS, Golbabaei F, Jafarzadeh E, Aazam K. Cancer and Noncancer Risk Assessment for Workers Exposed to the Chemical Pollutants in Ahvaz Gas Stations, Iran. Int J Env Health Eng [serial online] 2022 [cited 2023 May 29];11:19. Available from:

  Introduction Top

Many people worldwide are in contact with various chemicals in different jobs. Exposure to these substances can lead to multiple health effects.[1] World Health Organization (WHO) statistic evaluations indicate that 4 million worldwide people employ in the chemical industries.[2] Many compounds play a role in the emergence of air pollution. Essential air pollutants are among these VOCs. Solvents are used in various vocations and sectors, including the petrochemical industry, printing industry, and refinery.[3] VOCs are also some chemical compounds released evaporative throughout different fossil fuel processing stages.[4] Gasoline is a complex combination of 50 different hydrocarbons with a concentration of about 1% and trivial amounts of other materials. Gasoline hydrocarbons have 3–12 carbons. The gasoline index formula is C6H18, and its average molecular weight is about 113. Gasoline composition varies in different seasons and from one refinery to another.[5] The health effects of acute exposure to Gasoline via breathing, swallowing, and skin (less than 14 days) are irritation in the place of vulnerability.[6] For example, temporary nerve damage includes headaches, nausea, dizziness, and drowsiness during the refueling process or sudden discharge of car tank vapors and inhalation from gasoline spills at the fuel station.[7] VOCs are an essential part of gasoline compounds and pollutants in the air. According to research, BTEX compounds, which include benzene, toluene, ethylbenzene, and xylene, are index compounds that are constantly present alongside each other and are detrimental to human health, even at low doses.[8] The BTX has adverse health effects, including hematological[9] and neurological systems.[10] Benzene is classified as a human and animal definitive carcinogen by the International Agency for Research on Cancer (IRAC).[11] According to Lerner et al., (2012) benzene had the highest concentration among the 23 VOCs detected in employees' breathing zones.[12] Leukemia can be caused by long-term exposure to benzene.[13] Tiwari et al. (2009) conducted research and their purpose was to study the environmental concentration of VOCs in the vicinity of the industrial petrochemical area of Yokohama, Japan. The research results showed that BTEX had the highest concentration.[14] Gariazzo et al. (2004) conducted research. Their purpose was to study the analysis of VOCs around an oil refinery in Italy. The research results showed that BTEX had the highest concentration.[15] The study by Jafari et al. (2007) demonstrated that, among BTX compounds, the cancer risk of benzene in the gas station was higher than the standard level recommended by EPA.[16] The increase of gasoline distribution in fueling stations during recent years has resulted in the high exposure of workers of these stations to gasoline compounds.[17] Epidemiological studies show that the death rate from cancer among gas station workers is significant.[18] The risk assessment and cancer risk analysis of chemical substances are essential for implementing appropriate programs to reduce the rate of worker's exposure.[19] For decision-making about control measures and protecting workers against the adverse effects of chemical substances, it is necessary to evaluate health risks from exposure to these substances.[20] The risk evaluation process is the primary solution and key for evaluating risks related to environmental and occupational exposures to chemical substances.[21] There are more than 3000 active gas stations in Iran, which pose a significant risk to the workers in this industry sector. Considering the dangers of exposure to chemicals and increasing their use in daily life, the present study was conducted to investigate the health, cancer, and non-cancer risks of BTEX in gas stations in Ahvaz.

  Materials and Methods Top

Sample size determining

This investigation was cross-sectional research conducted during the spring of 2018 to assess the rank of pollutants risk releases in Ahvaz gas stations. We applied the study[22] results to calculate the required number of samples to estimate the amount of BTEX in gas stations. The mentioned research reported the standard deviation (SD) of ethylene benzene SD = 6.4 ppm; therefore, considering the 95% confidence coefficient and d = 2 ppm for accuracy (wrong estimation limit), the sample size was calculated from Eq. 1.

N is the number of samples

{INSIDE:1]is confidence coefficient 95% =1.96

δ^2 is SD

d is accuracy

Considering the 20% probability of sampling error, the minimum number of required samples in this study was 48. Furthermore, for the present study, considering that the urban divisions of Ahvaz at the time of the survey included eight municipal areas, we randomly selected a gas station from each region. As a result, according to [Table 1], 104 samples were collected from the gas stations surveyed. To organize workers exposed to chemical pollutants, we divided personnel based on job descriptions into three different jobs, including operators, head shifts, and supervisors. For the ambient air of gas stations, we collected 104 samples (64 samples for operators, 16 samples for head shifts, 16 samples for supervisors, and eight samples for blank (control). Before participating in the study, all participants signed a consent form. Based on a similar study, exposure to pollution for more than 3 h/day is considered inclusion criteria in the present investigation.[23]
Table 1: Samples size

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BTEX analysis and sampling method

We used 1501 method numbers from the National Institute for Occupational Safety and Health (NIOSH) to sample and evaluate BTEX. We also used Coconut shell charcoal (100/50 mg) to collect BTEX air samples in the employees' breathing zones. Inline, a representative sampler calibrated the micropump (SKC 222 model series) at a flow rate of 0.1 L/min before personal sampling. After collecting the samples, we extracted the analyte with CS2 (1 ml). Finally, the Gas Chromatography-Flame Ionization Detector VARIAN CP-3800 was utilized to identify and quantify chemical substances. In the next step, to calculate the concentration of pollutants in workers' breathing zone, we used Eq. 2. Table reference doses are expressed in this method.


C: Pollutant concentration (mg/m3)

Wf: Analyte discovered in the sample's front

Wb: The analyte found in the sample back

Bf: In the blank front, average media is used

Bb: Standard media in the blank back

V: Sample of air volume (L)

The pollutant concentration in Eq. 2 is given in the form mg/m3, which, at a vapor pressure of 760 mmHg, is converted (ppm) using Eq. 3

M: Pollutant molecular weight

The total time required to collect all samples was 288 h (3 h/sample); to calculate the time-weight average (TWA), we utilized Eq. 4.


C: Concentration of exposure (ppm)

T: Corresponding exposure time (hr.)

Health risk evaluation method

Based on the following steps to determine health risks due to exposure to pollutants, we used the semi-quantities methods presented by the Singapore Occupational Health Department.[24]

Hazard rating

The method proposed by the Singapore Department of Occupational Health recommends that the hazard rate be calculated according to the toxic effects of the chemicals or through the lethal dose (LD50) and lethal concentration (LC50) of the substances. However, in this study, we used the reliable American Conference of Governmental Industrial Hygienists (ACGIH) classification regarding the possible carcinogenicity of chemicals to determine the hazard rate (HR). ACGIH has divided substances into five groups based on their carcinogenic potential. This grouping includes A1 (definitely carcinogenic) to A5 (non-carcinogenic) [Table 2].
Table 2: Pollutants hazard rating

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Exposure rating

We determined the weekly exposure rate (ER) (ppm or mg/m3) using the results of measuring and analyzing pollutants based on NIOSH 1501 in the workers breathing zone and using Eq. 5.

E: Weekly exposure (ppm or mg/m3)

F: Number of times per week that you are exposed (no. per week)

D: Exposure's average duration (hours)

M: Exposure magnitude (ppm or mg/m3)

W: Week's average number of working hours (40 h)

[Table 3] determines the ER by comparing weekly exposure (E) with the permissible exposure limit.
Table 3: Exposure rating

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Risk level calculation

Risk levels calculated by using Eq. 6.


HR = Hazard rating on the scale of 1 to 5 [Table 2].

ER = Exposure rating on the scale of 1 to 5 [Table 3].

Risk ranking evaluation

The risk rating scaling of 1 to 5 is increasing in magnitude. A rating of 1 implies negligible risk, and a rating of 5 means very high risk. This ranking will enable the prioritization of action plans to reduce the risk of exposure. Risk ranking determines according to [Table 4].
Table 4: Risk rating

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Cancer and noncancer risk assessment

Prolonged exposure to benzene leads to leukemia. On the other hand, benzene can cause cancer even at low concentrations.[25] Therefore, cancer risk analysis is vital to identify hazardous substances and prioritize risk rankings in the workplace. Chronic daily intake (CDI) for cancer risk assessment due to benzene among job groups was illustrated by Eq. 7.

Cancer risk = CDI × CSFi.[7]

CA: Contaminates Concentration in air (mg/m3)

IR: Inhalation Rate (for adults 0.875 m3/h)

BW: Body Weight (for average person's 60.54 Kg)

ET: Exposure Time (8 h for workers)

EF: Exposure Frequency per year (350 days/year)

ED: Exposure Duration (30 years for individuals)

AT: Average Time (70 years × 365 days for carcinogenesis or ED × 365 for noncancer)

Carcinogenic effects of more than 10 − 6 were deemed concerning, whereas a value of 10 − 6 was deemed acceptable.

We used the hazard quotient (HQ) parameter for the noncancer situation assessment is represented in Eq. 8.

Rfc: Exposure concentration (μg/m3 or ppb)

HQ 1 denotes adverse noncarcinogenic effects of concern; an HQ of 1 was deemed an acceptable level.

Statistics analysis

We used the Statistical Package for the Social Science (SPSS) version 23 to analyze the collected data. Finally, to compare the mean concentration of measured pollutants (BTEX) with the threshold limit value (TLV) t-test exam was performed, and for significance evaluation, the considered P-value was <0.05.

  Results Top

Exposure rate to BTEX

We have measured 104 VOCs samples in selected gas stations, 64 related to the operators. The average TWA of benzene, toluene, ethyl benzene, and xylene in the operators breathing zone were 1.202 ± 0.83, 0.381 ± 0.36, 0.461 ± 0.29, and 0.036 ± 0.04 ppm, respectively [Table 5] and [Figure 1].
Figure 1: Worker's BTEX exposure level compared with TLV. TLV: Threshold limit value

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Table 5: Exposure levels of benzene, toluene, ethylbenzene, and xylene, in workers of gas stations

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Altogether 16 samples were measured from VOCs for the head shifts. Benzene, toluene, ethyl benzene, and xylene concentration average in head shifts breathing zone were 0.465 ± 0.14,0.296 ± 0.40,0.243 ± 0.14, and 0.126 ± 0.22 ppm, respectively [Table 5] and [Figure 1].

Furthermore, we have measured 16 samples from the VOCs of the supervisors. The average TWA of benzene, toluene, and ethyl benzene in the supervisors breathing zone were 0.336 ± 0.15, 0.103 ± 0.14, 0.239 ± 0.15, and 0.035 ± 0.03 ppm, respectively [Table 5] and [Figure 1].

The average content of benzene (1.202 0.83) in the breathing zone of operators was greater than the ACGIH's recommended TLVs-TWA (P < 0.05) for the three work categories evaluated. For all analyzed work groups, average toluene, ethyl benzene, and xylene concentrations were significantly lower than the TLV-TWA suggested by the ACGIH (P < 0.05).

Health risk evaluation

The risk evaluation and ranking of contaminants for exposure to gas station personnel is shown in [Table 4]. Benzene discovered across chemical components posed a very high risk to operators, as well as a high risk to each of the three employment groups surveyed. In all investigated job groups, the rank of risk for toluene, ethyl benzene, and xylene in the worker's breathing zone was low [Table 6] and [Figure 2].
Figure 2: Job group's risk rating

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Table 6: Health risk assessment results according to pollutants concentrations

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Cancer and noncancer risk assessment

We used the Chronic Daily Intake (CDI) to calculate cancer risk and the Exposure Concentration (EC) applied to determine the non-cancer risk. [Table 7] shows the level of cancer risk and non-cancer risk among gas station workers. Results show that the mean cancer risk for the operators was more than other groups (4.46 ×10-3), and in all discussed job groups, the cancer risk was higher than the acceptable limit of 10-6. The CDI for the operators was 0.163 (mg/kg/day). In addition, the non-cancer risk for the operators calculated more than the other groups and in all investigated groups was higher than the acceptable level (HQ ≤1). The EC for the operators was 12.62 (mg/m3).
Table 7: Benzene, toluene, ethylbenzene, and xylene's lifetime cancer risk and noncancer risk assessments

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  Discussion Top

Risk assessment utilizes different methods to rank chemical dangers, such as qualitative, semi-quantitative, and quantitative techniques.[24],[25],[26],[27],[28] The IARC studies show that many people worldwide have exposure to various chemical substances in different jobs. Exposure to these substances can cause various health effects for individuals.[29],[30],[31] For example, long-term exposure to different levels of pollutant concentration can raise cancer risk.[32] In addition, the use of fossil fuels in various industries[33] can result in the release of a variety of substances into the atmosphere.[34] The concentration of xylene in the worker's breathing zone was found to be lower in this study than in the other VOC concentrations investigated. The average concentration of benzene, on the other hand, was higher than in the other pollutants. Among the three employment groups surveyed, the average concentration of benzene in the operator's group breathing zone significantly greater than the TLV-TWA indicated by ACGIH. At the same time, other pollutant concentrations were lower than the TLV. It can consider VOCs vapor pressure as the leading cause for the distribution of substances in the workspace.[35] Oil and its related industries have a strategic and vital role in the country. According to the IRAC statistic report, people's number employed in petroleum is 400000 to 500000. Many employees in these industries imply the importance of further investigation on the subject of harmful factors in the workplaces,[36] including chemical factors. This research results show that benzene's risk rating was 5, showing a very high and high rank of risk. On the other hand, the benzene-related risk is higher than other pollutants among the noted substances. Rinsky shows the relationship between benzene and leukemia in different concentrations[37] Coline et al. showed that benzene can result in leukemia even in trivial amounts. Thus, we suggest corrective actions and adequate training to reduce exposure time to hazardous pollutants. Based on the toxicity of benzene vapors and the high concentration of pollutants, the first option is to eliminate this compound, but in terms of the process, it is impossible to eliminate benzene from gasoline because the BTEXs are important compounds used to increase engine efficiency.[38] Nowadays, Floren is introduced as a substance to substitute the BTEX compounds in gasoline to significantly increase engine efficiency. The addition of this substance to gasoline significantly decreases gasoline pollutants, including benzene.[18] Of course, research about this substance is in the early stages and has not found a complete application yet.[38] As a result, to substitute this substance with fewer dangerous ones to reduce hazard rate and exposure time. Furthermore, we propose a respiratory protection program to manage very high risk and a four-year periodical evaluation to control low risk.[39] We recommend a four-year periodical evaluation for low-risk levels because the risk for toluene, ethyl benzene, and xylene was 3, indicating a low rank of danger. Furthermore, from the results mentioned in [Table 6] and [Table 7], it can be inferred that among the three job groups studied, the health risk for the operators is higher than the other groups. It is necessary to mention that workers' exposure time to pollutants is different, so operators have the highest exposure per week with an average of 84 h. In contrast, head shifts and supervisors have the lowest exposure to pollutants, with 40 h per week. Thus, exposure time can justify obtained risk ranks for different jobs. Estimation of carcinogenic risk of chemical substances in gas stations showed that operators have the highest risk with a risk score of 4.46 × 10− 3, and supervisors have the lowest risk of cancer affliction with a risk score of 2.08 × 10− 3, in other words, 4.46 and 2.08 cancer per 1000, i.e., higher than the acceptable limit of 10-6. Therefore, cancer risk due to exposure to dangerous substances should not be more than 1.1 people per 100,000.[40] The average cancer risk of benzene was higher than 10-6 in the study of Harati et al.(2020)[40] also Tunsaringkarn et al.(2012).[41] In addition, Yimrungruang et al.(2008) stated that Benzene is one of the VOCs that has the potential to cause cancer.[40] As a result, long-term VOC exposure may cause changes in complete blood counts.[27],[42] The noncancer risk for BTEX in this study was higher than the acceptable level (HQ 1). Individual habits and nonoccupational lifestyle, on the other hand, can cause cancer. However, some risk factors, including individual habits and nonoccupational lifestyle, can cause cancer.

  Conclusion Top

We consider cancer risk analysis for benzene in our study because there was no appropriate method available for other pollutants. According to ACGIH and IARC substances Carcinogenesis classification, benzene is classified as a definitive human carcinogen. This research demonstrated that risk assessment and cancer risk analysis approaches utilized during the design phase can lead to methods to improve workplace conditions and provide valuable data for decision-making, prioritizing hazards, and maintaining programs. However, we can significantly decrease the risk of exposure to these compounds using control measures such as reducing work shift time, installing the vapors recycling system, periodic maintenance of fuel distribution equipment, and designing a particular chamber for the worker.

Financial support and sponsorship

This investigation has received support from the Department of Occupational Health Engineering, School of Public Health, Tehran University of Medical Sciences, Department of Health Safety Environment Ahvaz National Iranian Oil Products, Distribution Company, and Oil Industries' Commissioning and Operation Company (OICO) R and D Department. The authors further thank the people who participated in this study.

Ethics Code

The research Ethics Committee approved this study of Tehran University Medical of Sciences, Tehran, Iran (No: 32610). Informed consent was obtained from all participants, and each one received a code to be unknown.

Conflicts of interest

There are no conflicts of interest.

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]


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