Assessment of BTX Concentration around Fuel Station in Eastern Province Kingdom of Saudi Arabia.

AIM: The aim of this study is to determine the benzene, toluene, and xylenes (BTX) concentration levels in and around fuel station and its expected health risks in the City of Dammam and Al-Khobar, Saudi Arabia.
METHOD: Forty fuel dispensing facilities were randomly selected on the basis of three different areas, residential, traffic intersection, and petrol pump locations (refueling stations). coconut shell charcoal cartridges were used for samples collection and portable Ambient Analyzer was used for measuring BTX (benzene, toluene, and xylenes) concentration.
RESULTS: Results show that the average concentration of benzene, toluene, and xylenes level around fuel stations was 10.30, 4.09, and 2.47 ppm, respectively. All means of concentration values of BTX around residential, traffic intersection, and fuel stations are exceeding the limits of air quality standards values (P < 0.01). The mean concentration of BTX around residential area, side street, and direct street was benzene 8, 12.2, and 11.5 ppm, toluene 2.5, 5.95, and 3.37 ppm, and xylenes 2, 2.13, and 2.7 ppm. Hazard Quotient (HQ) was more than >1 which showed that carcinogenic probability has increased those exposed to this toxic chemical.
CONCLUSION: Ambient concentration of BTX was high compare to neighboring residential area and 100 m from the fuel station which can negatively affect on health of several residences. The Environmental contamination associated with BTX in petrol fuel stations impulses the necessity of preventive programs to reduce further air quality deterioration and reduce the expected health risks. Copyright:

INTRODUCTION

Fuel stations are the main source of gasoline vapors’ emissions which is the major sources of air pollutants. In the atmosphere around fuel service station, there are various volatile aromatic hydrocarbons (VAHs) present due to emissions of vapors through activity such as dispensing and transportation of petrol.[12] The main components of VAHs are benzene, toluene, and xylenes which are called as BTX compounds.[3] In Saudi Arabia, fuel dispensing facilities are located around houses, schools, and hospitals particularly in urban areas of country.[1]

The common sources of emission of benzene, toluene, and xylenes compounds are the vehicles on the roads and fuel stations. Among BTX, xylene is the most dangerous to human health.[234] Fuel and gas products have high concentration BTX which emitted in the form of vapor in the environment. The common sources of these volatile organic compounds (VOCs) were gasoline vapor emission and motor vehicle exhaust.[5]

BTX also plays an important role in the atmospheric chemistry. It has been recognized as an important photochemical precursor for tropospheric ozone and second organic aerosols.[6]

Different studies found that the concentration of benzene was 89.09%, xylenes was 252%, and toluene was 239% in the fuel compared to normal threshold level.[7] Benzene and ethylbenzene are well-known carcinogens to human body.[8] Population which are living near the petrol pump stations were directly exposed to BTX. These toxic products are volatile organic compounds which are commonly called BTX.[9] These toxic compounds were classified as group 1 and 2b carcinogens.[10] Various studies were conducted in European countries to determine the organic compound emissions from gas stations and assessing control systems to prevent emissions[1112] and to study their expected health risks on workers.[13]

There are various health disorders due to exposure of these toxic organic compounds[14] such as neurological disorders, cancers, and teratogenic effects. The main route of entry is inhalation or ingestion. The most common health impact is leukemia, which is estimated that around 1 million people affected around the world and four types of leukemia diagnosed in their lifetime risk on exposure to 1 mg/m3 of benzene concentration.[15] In the occupational setting, health impacts of BTX are well known in oil industry. Association of BTX with cancer was proved in different studies.[161718]

A Saudi Arabia national law stipulates that benzene level in the fuel not exceed than 1 ppm per liter. The study sample was collected for finding the concentrations of BTX (benzene, toluene, and xylenes) from 40 fuel stations and to determine the expected health risks on the human being for exposure of BTX by using HQ.

MATERIAL AND METHODS

Study settings and study design

This is the cross-sectional study and forty petroleum fuel stations were randomly selected, 20 samples each from the city of Dammam and Khobar. Each station has residential, traffic intersection, and station area for measuring the concentration of BTX. through simple random sampling [Figure 1].

Figure 1

GIS MAP of Dammam and Khober

Risk assessment

Benzene inhalation was calculated through United State Envrionment Protection Agency’s (USEPA) condtions for occupational exposure. Exposure duration (ED) and exposure frequency (EF) values were derived from interview data and the inhalation uptake of 50% of all intake [exposure concentration (EC)]. Exposure was done by the calculation of inhalation intake (EC) at concentration of inhaled air benzene as the following formula: EC = exposure concentration or intake (μg/m3)

EC = (CA × ET × EF × ED)/AT

CA = benzene concentration (μg/m3)

ET = exposure time, hours/day = 8 h/day or longer exposure time depending on individual data of workers

EF = exposure frequency (5 days/week × 50 weeks/year) =250 days/year guided by the USEPA. ED = exposure duration (25 years), AT = averaging time = average time in hours per exposure period (25 years for general working period is equivalent to 219,150 h) and 70 years for lifetime cancer risk characterization (70 years × 365 days/year × 24 h/day = 613,200 h) guided by the USEPA[19]

Cancer risk characterization by comparison to inhalation unit cancer risk (IUR) was considered as the following: Cancer risk = IUR × EC

where IUR = 2.2 × 10−6 to 7.8 × 10−6 per 1 μg/m3

If the risk value > IUR or 2.2 × 10−6 to 7.8 × 10−6, that means an unacceptable risk concerning cancer.

If the risk value <2.2 × 10−6, that means an acceptable risk of cancer.

Non-cancer risk assessment is considered as the Hazard Quotients (HQ) calculation of non-cancer risk from chronic exposure to inhaled benzene, which was calculated by following the USEPA[19]

HQ (unitless) = EC/RfC

EC (μg/m3) = exposure concentration in air

Reference concentration (RfC) of benzene is 0.03 mg/m3 from the USEPA-IRIS.

Sampling and measurements

The concentration of BTX in air was checked during day work. Samples were collected at 1.5 m above ground about 2–3 m from the fuel pump by active sampling with a flow rate of 100 ml/min using SKC battery-operated air sampling pump model PCXR. The stratified random sampling was used for selection of fuel stations. BTX concentration levels were measured by using standard calibrated instrument. MIRAN SapphIRe Portable Ambient Analyzer was used for measuring BTX (Benzene, Toluene and Xylene).[18] It is placed at 1.5 m height. LOD ranges from 0.05 to 0.07 microgL (-1) and relative standard deviation ranges from 0.5% to 11.6% at concentrations 5 and 0.1 microgL (-1), respectively.

Data analysis was done on statistical packaging social science (SPSS) software. Results were presented in frequency tables. Descriptive statics, independent comparison T-test, correlation, and graphical presentation were used for data presentation. A hazard quotient (HQ) was calculated, which is the indicator of health hazard to the community. A value of hazard quotient (HQ) ≥1 indicates the risk of carcinogenic probability and value <1 indicates safe level.[19]

RESULTS

The mean concentration of BTX was found in the cities of Dammam and Khobar: benzene 10.3 (SD 2.5) (benzene TLV 0.5 ppm), toluene 4.09 (SD 2.1) (toluene TLV 20 ppm), and Xylene 2.47(SD 1.7) (Xylene TLV 100 ppm). Both toluene and xylene were within the normal TLV, but benzene found excessive allowed TLV in both cities; significant differences were found between the levels of toluene and xylene among fuel petrol stations in Dammam in comparison with Khobar fuel stations [Table 1, Figure 2].

Table 1

The Concentration of benzene, toluene, and xylene (BTEX) in fuel station

Concentration	**TLV	Dammam city		Al-Khobar city		P
		Mean	SD	Mean	SD
Benzene (ppm)	0.5 ppm	10.30	2.51	11.07	2.98	0.791
Toluene (ppm)	20 ppm	04.09	1.62	01.74	0.25	0.001*
Xylene (ppm)	100 ppm	02.47	0.59	03.97	0.89	0.006*

**(Threshold Limit Value) *P<0.01

Figure 2

Concentration of benzene, toluene, and xylene (BTX) in all selected fuel petrol stations at Dammam and Khobar cities

Mean levels of BTX [Table 2] concentration were found from petrol stations located at the residential area [8.0 ppm (SD 3.1)], side streets [12.2 ppm (SD 1.9)], and direct street [11.5 ppm (SD 1.3)] in Dammam and Khober. Benzene concentrations in all sites were found to be exceeding the TLV (0.5 ppm), while mean concentrations of Toluene and Xylene were within the TLV (20 ppm and 100 ppm, respectively) in all selected sites.

Table 2

The concentration of benzene, toluene, and xylene (BTEX) in different sites adjacent to fuel stations in cities of Dammam and Khobar

Sites near to fuel station	Benzene			Toluene			Xylene
	TLV 0.5 ppm			TLV 20 ppm			TLV 100 ppm
	Mean ppm	Max.ppm	Min.ppm	Mean ppm	Max.ppm	Min.ppm	Mean ppm	Max.ppm	Min.ppm
Residential n=8	8.0	10.40	05.60	2.5	03.61	01.40	2.0	02.80	01.20
Side street n=10	12.2	18.99	11.91	5.95	13.64	02.22	2.13	04.35	00.20
Direct street n=6	11.5	13.80	09.20	3.37	04.77	01.46	2.70	02.83	02.10

Mean difference of BTX [Table 3] concentration among different sites and P value show a statistically significant difference.

Table 3

Concentration of benzene, toluene, and xylene (BTEX) in different areas of fuel stations at Khobar city

Areas	t-test	Mean	P
Residential, Side street, and direct street	8.13	10.56	0.05

The evaluation of the hazard quotient (HQ) [Table 4] for BTX among different sites shows that there is risk of carcinogenic effect to the nearby community living near to fuel station.

Table 4

The hazard quotient (HQ) for benzene, toluene, and xylenes

Areas	Benzene	Toluene	Xylenes
Residential	1.76	10.48	11.75
Side Street	2.34	12.77	11.89
Direct Street	3.45	13.87	12.23

An HQ > 1 is considered an adverse carcinogenic effect of concern

In the mean difference of meteorological factors such as [Table 5] temperature, humidity, and wind speed around the fuel stations, only wind speed was statistically significant (P value < 0.05).

Table 5

Comparison between mean levels of meteorological factor in fuel stations located in side street and direct street

Characteristics	Mean	P
Temperature (°C)	23.27	0.14
Humidity (%)	42.81	0.03
Wind speed (m/s)	4.137	0.00
BTX (Side Street) Mean (SD)	10.25±1.25	0.05
BTX (Direct Street) Mean (SD)	9.52±1.05	0.04

**P<0.01

DISCUSSION

The results of the present study show that the concentration levels of benzene, toluene, ethylbenzene, and xylene in both cities were high at fuel station and around the fuel stations. Hazards quotient value indicated that there is a risk probability of cancers to nearby living population.

The result of this study found that concentration of benzene (10.30 ± 1.88 ppm) was high in environment compared to standard limit (0.5 ppm over 8-h exposure)[20] which is standard by USA Occupational Safety and Health Administration (OSHA) and the American Conference of Governmental Industrial Hygiene (ACGIH).[21]

Previous studies found that mean concentration levels of benzene, toluene, and xylenes were high in Thailand,[22] Brazil,[23] and northern India.[24]

Hazard ratio in this study found greater than 1, which indicates the increased risk of cancer and also highlights the increased potential toxic and carcinogenic risks to which the people in the eastern province exposed to through toxic compounds of fuel such as BTX and its alkyl derivatives, which are harmful to human health because of their toxic, mutagenic, or carcinogenic properties; the same results were produced by the previous study.[25] These results were consistent with the previous study conducted in north India[26] and in Brazil.[27]

The relationships between the overall concentrations of BTX and traffic volume were found to be cofactors for elevated values for BTX in fuel petrol stations in both Dammam and Khobar. Similar studies conducted in Algeria and Brazil indicated that the levels of BTX and air pollution gases may be also affected by the atmospheric condition, the traffic density, and different activities in gas stations.[2829]

In addition, the National Institute for Occupational Safety and Health (NIOSH)-issued guidelines for BTX As 0.1,100 and 100 ppm respectively.[22] These findings are in accordance with recent studies which revealed that apart from the increasing vehicular traffic, another major cause of worry is unacceptably high concentrations of air quality gases and BTX in and around refueling stations.[2324]

The presence of BTX in the fuel/gas products is a high risk for human health specifically benzene compounds.[25] The results of this study found that benzene concentration present in the fuel/gas products was higher than the standard level.

CONCLUSION

The results of this study showed that BTX concentrations in the ambient air of fuel stations were higher than the average values in fuel station areas and near to fuel satiation areas, and HQ values were also greater than 1 which showed that the risk probability of cancer among resident was high. Therefore, effective intervention is needed to prevent harmful health effects.

Ethical approval and Consent to participate

The study was approved by Imam Abdul Rehman Bin Faisal University Ethical Committee, Saudi Arabia. The ethical document no is 2345.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.