Analytical Determination of Heavy Metals in Various Dokha and Shisha Products, and Related Health Implications

Determination of Heavy Metals in Various and Products, and Abstract Objective: In this present study twelve metals were analyzed in various Dokha and Shisha products. The analysis was carried out using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). All the metals were found in each sample and at various concentrations. Furthermore, the concentration of various heavy metals with e-cigarette is compared in the discussion. Results: Dokha tobacco contained very high metal concentrations compared to Shisha and Marlboro brand cigarette tobaccos. The highest level of aluminum(Al) (421.235 μg/g), boron(B) (219.815 μg/g), Cobalt(Co) (25.050 μg/g), copper(Cu) (24.000 μg/g), lead(Pb) (468.620 μg/g), and zinc(Zn) (342.740 μg/g), were found in Alward Alahmar Green Dokha tobacco. Due to the significant toxicity of these metals, it is very important to control and quantify their concentrations in the tobaccos.


Introduction
Tobacco is available in the market legally although it is harmful to humans [1]. During smoking, a complex mixture of compounds is inhaled into the respiratory system affecting different organs. In digestive tract. Heavy metal poisoning is considered a medical emergency, and the patient should be taken to a hospital emergency room. Heavy metals concentrations in Dokha and Shisha tobacco products have not been extensively studied in the Middle East.
Tobacco leaves are rich sources of toxic heavy metals as metals get preferentially enriched in the tobacco leaves during plant growth [3,4]. The use of tobacco products always puts an impact/influence on the health of smokers directly as well as non-smokers via passive smoking and adds heavy metal content to the environment [5,6].
Dokha is commonly smoked out of an elongated wooden pipe called a Midwakh (alternatively spelled 'Medwakh').
Hookah is a water pipe used to smoke Shisha tobacco mixture in which charcoal heated air passes through a water-filled chamber [7][8][9][10]. According to a World Health Organization advisory, a typical one-hour session of hookah smoking exposes the user to 100 to 200 times the volume of smoke inhaled from a single cigarette.
Even after passing through water, tobacco smoke still contains high levels of toxic compounds including carbon monoxide, heavy metals, and cancer-causing chemicals (carcinogens) [11]. The traditional Midwakh pipes have no filters so large amount of toxic heavy metals can easily enter the lungs [12]. The content of metals in tobacco varies a lot and it depends on several factors such as soil type and pH genotype, use of some metal-containing pesticides, fertilizers, etc. Some of the metals such as iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) are important micronutrients and they are also very important for plant growth and yield [13,14].
While soil factors have a large impact on the bioavailability of metals to plants, different species or varieties grown on the same soil can have different metal uptake [15].
However, other metals such as lead, cadmium, and nickel are not important for the plant growth but they can cause serious health and ecological problems, and several toxic metals as carcinogens. Cadmium (Cd), chromium (Cr), arsenic (As), beryllium (Be) and nickel (Ni) are classified as group 1 human carcinogens [16]. In shisha, the concentration of toxic elements per portion smoked is diluted by the molasses and glycerin. It is noted that the

Sample Collection and Storage
Dokha and Shisha samples analyzed during this study such as "TURBO" Dhoka, "Alward Alahmar" Dhoka, "Yusuf Redha" Dokha, Shisha "Arguilla Premium Natural", "MAZAYA" and "Al Fakher" Shisha samples were purchased from different stores. All samples were assigned an identification number and logged into a database.
They were sealed in plastic bags and stored at 27 °C in their original packaging until tested.

Chemical Reagents and Preparation
Analytical Reagent (A.R.) grade chemicals and reagents used for the preparation of concentrated Hydrochloric acid (HCl) A.R (37%), concentrated Nitric acid (HNO3) A.R (65%) were purchased from Sigma-Aldrich. ICP multi-element standard solution IV, (23 elements in diluted nitric acid) 1000 mg was used to prepare the calibration standards used in determining the heavy metal concentration in the samples. To dilute the standard solution deionized water was used.

Instrument and Apparatus
Inductively Coupled Plasma ICP-OES (Varian-VISTA MPX) was used to determine the concentration of heavy metals. Ceramic pestle and mortar used for grinding and homogenizing the tobacco samples. Digital analytical balance (Scientech with model no SA210), and Whatman No. 42 filters (ash less-Germany) were used for weighing, and filtering the samples, respectively. All Glassware were soaked in 5% nitric acid for 24 h, washed with deionized water, and dried to ensure that any contamination from glassware does not occur.

Preparation of Tobacco Samples
The samples were air dried on clean watch glass and care was taken to avoid influence by dust during air drying. The dried leaves were ground using mortar and pestle and sieved with mesh sieve.

Acid Digestion of Tobacco Samples
In this present work, the solid samples were digested using acid digestion method. Digestion with acid or acid mixtures has long been the traditional method for the determination of metals in plants. It is very strong acid digestion that will dissolve all elements that could become environmentally available. About 0.2 g of ground tobacco leaves was weighed into a clean 125 mL Erlenmeyer flask.
A 10 mL mixture of HNO 3 (65%) and HCl (37%) with a ratio of 4:1 (v/v) were added and allowed to digest by heating the vessel in a water bath-shaker for 12 h at 100 •C. The mixture was finally heated strongly to a medium heat for 3 minutes and allowed to cool.
The solution was filtered using 9 cm diameter Whatman (No.

Analysis of Standard Reference Materials
All samples were analyzed for Al, B, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn concentrations. Moreover, the precision, accuracy, and reproducibility of results for every run was started with a control, blank and testing several quality controls (QC) solutions.

Results
Our research provided information related to possible toxic heavy metals present in Dokha and Shisha products locally sold in UAE market. The metal concentrations in various tobacco samples are presented in Table 1     Apple Shisha" (24.155 µg/g); whereas the highest level was found in "Alward Alahmar Green Dokha" (468.620 µg/g).
From the results shown in Table 1, "Alward Alahmar Green Dokha" had the highest content of Al, B, Co, Cu, Pb, and Zn. This dokha product was found to be the most hazardous compared to the other analyzed tobacco samples.
"TURBO Dokha Premium-1" was found to contain the highest level of cadmium (58.460 µg/g), whereas the cadmium level did not  to the popular suppliers. Awareness on the heavy metals content in "Dokha" and other tobaccos and their related health implications must be publicized in order to reduce the number of smokers and to aim for a healthy society. In order to regulate the heavy metals content of tobacco and to protect smokers from heavy metals exposure international legislation should be passed.

Heavy Metal and E-Cigarettes
In conclusion, awareness on the heavy metals content in "Dokha" and other tobaccos and their related health implications must be publicized in order to reduce the number of smokers and to aim for a healthy society. In order to regulate the heavy metals content of tobacco and to protect smokers from heavy metals exposure international legislation should be passed.

Limitations
The main limitation of our study is the inability of measuring all the types of "Midwakh" in the market.

Ethics Approval and Consent to Participate
No ethics approval needed since no human participants are involved.

Consent for Publication
Not applicable. All authors have read and approved the manuscript.