INTRODUCTION:

Heavy metals have recently become an increasing ecological catastrophe and a major concern in terms of environmental pollution due to their persistence and resistance to biodegradation. For this reason, most researchers focus on toxic metal contamination, notably because of its potential consequences for the environment and human health¹.

There are several ways that heavy metals enter the soil, including through aerosols produced by the burning of fossil fuels, metal smelting, and other human activities, as well as through urban and industrial waste. Excessive use of manure, micronutrients (inorganic) fertilizers, herbicides, insecticides, tannery, mining, and other causes of heavy metal poisoning have been identified by researchers in recent years as contributing to soil contamination^1,2. Soil contamination with heavy metals can have a negative impact on plant physiological development and agricultural production quality, as well as posing a serious threat to human health through the food chain^3,4. The primary way in which people are exposed to dangerous metals is by chain transfer from soil to plants². At larger concentrations, certain heavy metals are extremely hazardous, while others are essential for the healthy physiological growth of plants and other living organisms⁵. The rise in heavy metal content is mostly attributable to the usage of fertilizers, pesticides, compost manures, and contaminated water for irrigation. The toxic metals are subsequently absorbed and bioaccumulated in large amounts by plants cultivated in soil tainted with toxic metals, which ultimately puts food quality and safety at risk².

Vegetables are a vital component of the human diet and are the edible sections of plants⁶. Vegetables can be eaten raw or prepared with extra spices. They are an essential component of the human diet because of their additional protective nutritional value, which includes trace elements, vitamins, minerals, proteins, and carbohydrates⁷. Regretfully, despite their nutritional benefits, leafy greens aid in the entry of heavy metals into the food chain through human consumption⁷. Because organic manures and inorganic fertilizers are used excessively in the soils used to grow these vegetables, the plants absorb a lot of heavy metals⁷. As a result, it is now essential to monitor heavy metals in agricultural soils, irrigation water, and food crops. Additionally, it is essential to examine the consumption of food crops with high heavy metal content in order to detect any possible threats to human health. People eat a variety of vegetables, including watercress and lettuce, which are popular in Syrian cities either raw or cooked. For this reason, the primary aim of this work is to determine the concentrations of Pb and Cd. Additionally, the chosen plants will have their potential environmental risk index for the harmful metals assessed.

MATERIALS AND METHODS:

Reagents:

All the reagents used were of analytical grade. Double distilled water was used for dilution and preparation of reagents and standards. All glassware and plastic containers used were washed with liquid soap, rinsed with water, soaked in 2% nitric acid for 24 Hrs, cleaned thoroughly with double distilled water and dried in such a manner to ensure that any contamination does not occur.

Study area:

The study was conducted in several areas in Damascus and its countryside (Ibn Al-Nafis and Eastern Ghouta). The studied areas were selected based on a study conducted in the Department of Toxicology, Faculty of Pharmacy, Damascus University, in which these minerals were studied in agricultural soils cultivated with these vegetables.

Sample collection:

Lettuce and watercress samples were collected in October 2021 and April 2022 from the studied areas where samples were taken randomly. The vegetable samples (edible parts) were collected and stored in labelled zippered polyethylene (PE) bags and taken to the Central Laboratory Directorate of the Ministry of Local Administration and Environment for further processing. Details of vegetable samples are given in Table 1.

Table 1. Details of vegetable samples

S. No	Common name	Botanical name	Edible part	Family
1	Lettuce	Lactuca sativa L.	Leaves	Asteraceae
2	Watercress	Nasturtium officinale R. Br.	Leaves	Brassicaceae

Sample treatment:

The collected fresh vegetable samples were washed thoroughly with tap water then with distilled water to remove dust and impurities. The cleaned samples were sliced into small pieces and air-dried in the open air for a week to eliminate excess moisture. The dried vegetable samples were ground into a fine powder using an electric mixer, then packed in polyethylene containers, with a label attached to each sample. The powdered samples were then preserved at room temperature until further analysis.

Sample digestion:

(1) g of each sample was weighed into a flask, then dried and digested using the wet-oxidation procedure⁸. (10) ml of concentrated nitric acid (Panreac, 65%) and (3) ml of hydrogen peroxide (Avonchem, 30%) was added in each sample. The mixture was heated using an electric heater to reach 100-130° until the brown fumes disappeared and the digestion process was complete. The final solution was diluted with double distilled water and filtered using Whatman filter paper (No.41). The samples have been numbered and are ready for reading in graphite furnace atomic absorption spectrophotometer⁹

Analysis of samples:

The samples were analysed by GF-AAS to determine the heavy metals concentration^10,11. Working conditions of GF-AAS are shown in (Table 2).

Table 2. Instrument operating conditions for the determination of heavy metals in samples by GF-AAS.

Element

Wavelength

(nm)

Lamp current

(mA)

Slit width

(nm)

Detection limit

(μg/L)

283.3

7.5

1.3

0.3

228.8

7.5

1.3

0.01

All standards and samples were analysed in triplicates. The value of heavy metals concentration in vegetable samples (mg/L) was applied into following equation Eq. (1) to obtain the actual concentration of heavy metals present in the samples (mg/kg).

Heavy metal concentration in vegetable samples,

(1)

where, C = Heavy metal concentration in vegetable samples (mg/L); A = Final volume of diluted sample; W = weight of sample (g).

RESULT:

Lead and cadmium concentrations in lettuces samples:

The mean concentrations of heavy metals in the selected lettuce samples collected are presented in (Table3). Results are expressed as the average of the three replicate analyses.

· The concentrations of lead in lettuce samples were ranged between 0.0026 to 0.06411 mg/kg. All studied samples remained below the acceptable upper limit (0.3mg/kg) according to FAO2019.

· The concentrations of cadmium in lettuce samples were ranged between 0.081 to 0.587mg/kg. Ten samples exceeded the acceptable upper limit of 0.2 mg/kg according to FAO2019.

Table 3. The mean concentration of heavy metals (Mean± SD, n = 20, mg/kg dry weight) in lettuce samples.

Cd	Pb
0.1377±0.002	0.0114±0.0003
0.177±0.002	0.0037±0.0002
0.112±0.001	0.0114±0.0002
0.332±0.002	0.0041±0.0002
0.144±0.003	0.0148±0.0002
0.287±0.002	0.0552±0.0002
0.445±0.003	0.0202±0.0002
0.354±0.003	0.0036±0.0003
0.131±0.003	0.0071±0.0002
0.587±0.003	0.0641±0.0003
0.083±0.002	0.0150±0.0002
0.162±0.002	0.0200±0.0001
0.081±0.002	0.0122±0.0002
0.197±0.002	0.0158±0.0003
0.160±0.002	0.0465±0.0003
0.297±0.002	0.0110±0.0003
0.255±0.002	0.029±0.0003
0.341±0.002	0.002±0.0002
0.265±0.002	0.0105±0.0003
0.480±0.002	0.0061±0.0002

Lead and cadmium concentrations in watercress samples:

The mean concentrations of heavy metals in the selected watercress samples collected are presented in (Table4). Results are expressed as the average of the three replicate analyses.

· The concentrations of lead in watercress samples were ranged between 0.0418 to 1.1395mg/kg. Five samples exceeded the acceptable upper limit of 0.3 mg/kg according to FAO2019.

· The concentrations of cadmium in watercress samples were ranged between 0.227 to 1.791mg/kg. All studied samples were above the acceptable upper limits of 0.2mg/kg according to FAO2019.

Table 4. The mean concentration of heavy metals (Mean± SD, n = 20, mg/kg dry weight) in watercress samples.

Cd	Pb
1.217±0.002	0.0772±0.0002
1.791±0.003	0.1431±0.0003
0.658±0.003	0.3362±0.0002
1.071±0.003	0.0418±0.0002
1.112±0.002	0.1738±0.0003
0.904±0.002	0.2922±0.0002
1.06±0.025	0.1782±0.0002
0.982±0.002	0.1475±0.0002
0.768±0.002	0.265±0.003
0.460±0.002	0.2922±0.0002
0.472±0.002	0.06413±0.0002
0.409±0.002	0.0729±0.0002
1.082±0.002	1.1395±0.0002
0.226±0.002	0.9419±0.0002
0.355±0.004	0.187±0.002
0.724±0.003	0.0465±0.0002
0.457±0.002	0.3668±0.0002
0.930±0.003	0.7532±0.0002
0.576±0.003	0.2352±0.0002
0.506±0.002	0.0553±0.0002

DISCUSSION:

Plants obtain their content of heavy metals from the surrounding medium (soil, water, and air). The content of this medium of heavy metals is due to the basic mineral content, in addition to what human activities contribute to increasing this content in the surrounding medium.

The results of the Cd and Pb concentration in the studied samples are summarized in (table5) and (table6)

Table 5. Results of descriptive statistics of Cd and Pb in lettuce samples estimated in mg/kg.

Lettuce	Min value	Max value	Average	Standard deviation	Number of samples
Cd	0.081	0.587	0.2513	0.1398	20
Pb	0.0026	0.0641	0.0181	0.0175	20

Table 6. Results of descriptive statistics of Cd and Pb in watercress samples estimated in mg/kg.

Watercress	Min value	Max value	Average	Standard deviation	Number of samples
Cd	0.227	1.791	0.788	0.3781	20
Pb	0.0418	1.1395	0.2904	0.3052	20

(Figure1) shows the chart of the mean concentration of Pb in the studied samples.

Figure 1. The mean concentration of Pb in the studied samples.

(Figure2) shows the chart of the mean concentration of Cd in the studied samples.

Figure 2. The mean concentration of Cd in the studied samples.

The presence of cadmium in the samples of cultivated vegetables is attributed to its widespread use in nearby industries, such as the production of batteries, tanning, dyeing, and the use of phosphate fertilizers¹².

In addition to irrigating the crops with sewage water that contains high concentration of Cd and Pb, or using contaminated water directly which exposes the soils and plants to these metals, Cd can be absorbed easily by crops¹³. The metals may also be distributed over great distances due to their extensive application in numerous local industries, as stated in references^14,15, which is a result of industrial human activity.

The risk of exposure to Cadmium is higher on people who live close to sources of cadmium pollution, as chronic exposure of cadmium leads to anaemia, insomnia, high pressure, and kidney disorders¹⁶.

Lead presence is explained by the growth of plants next to public roads. Where the percentage of lead in the atmosphere and soil rises due to the presence of traces of lead compounds that are added to the fuel of cars and vehicles, noting that the levels of lead in the soil and plants adjacent to transportation roads are directly related to the intensity of traffic on the roads¹⁷. In addition, heavy metals accumulate in the soil, including lead and are likely to pose a threat to plant and animal production and human health, and this is confirmed by the study conducted by Onder et al.¹⁸. Lead toxicity is known to cause musculoskeletal, renal, ocular, neurological, immunological, reproductive, and developmental effects¹⁹.

CONCLUSION:

The study showed that lead exceeded the maximum permissible limits in some watercress samples, while it was within the acceptable range according to FAO2019 in lettuce samples. But heavy metals, including lead, accumulate year after year in the soil, which can pose a threat to plant production and human health. And the presence of toxic cadmium metal in concentrations exceeding the maximum limits allowed by FAO 2019 in all watercress samples and some lettuce samples, can be directed towards the role of vegetables in increasing the intake of this metal in the human body.

CONFLICT OF INTEREST:

The authors have no conflicts of interest regarding this investigation.

REFERENCE:

1. Nikhil TH, et al. Qualitative Estimation of Heavy Metals in Water of Rewalsar Lake. Asian Journal of Pharmaceutical Analysis. 2024; 14(3): 151-4.

2. Abdulsahib HT, et al. Removal of Heavy metals from Wastewater by Novel Adsorbent based on Chitosan and Lignin. Research Journal of Science and Technology. 2015; 7(1): 35-46.

3. Moumita SI, et al. Agricultural Soil Contaminated by Heavy Metals Exposed by the Byproducts of Durgapur Thermal Power Station, Durgapur, W.B. Asian J. Research Chem. 2012; 5(6): 742-747.

4. Rajeshwari BM, Patil S. Heavy Metals Status in Soils of Ballari District using Atomic Absorption Spectroscopy (AAS). Asian Journal of Research in Chemistry. 2018; 11(4): 701-4.

5. Livleen SH, Namarta J. A review on soil heavy metals contamination: effects, sources and remedies. TIDEE: TERI Information Digest on Energy and Environment. 2022 Mar 1; 21(1): 83-.

6. Nikita SH, Jasvinder K. Chemical Examination of Heavy Metals of the Drinking Water in the Ramgarh Area, Mahwa, Rajasthan. Asian Journal of Research in Chemistry. 2025; 18(3): 129-4.

7. Kalpana PA, et al. Evaluation of heavy metals in selected medicinal plants and their corresponding soils collected from environmentally diverse locations of India. Research Journal of Pharmacy and Technology. 2018; 11(8): 3489-93.

8. Kholis NO, et al. Biosorption of Heavy Metals Cu2+, Cd2+, and Pb2+ by Chitosan and Powder from Capiz shell (Placuna placenta). Research Journal of Pharmacy and Technology. 2025; 18(5): 2155-3.

9. Anastácio MV. Determination of Trace Metals in Fruit Juices selected by ASAE using Atomic Absorption Spectroscopy (master’s thesis, Universidade de Lisboa (Portugal).2016.

10. Venugopal NVS., et al. Trace Element Levels in Fruits and Vegetable by using Atomic Absorption Spectrophotometer (AAS). Asian Journal of Research in Chemistry. 2011; 4(11): 1769-1771.

11. Bais SK, et al. Comparative evaluation of heavy metals in marketed haematinic herbal formulations by atomic absorption spectroscopy. Asian Journal of Pharmaceutical Analysis. 2014; 4(1): 11-6.

12. Adepoju-Bello AA, et al. Analysis of some selected toxic metals in registered herbal products manufactured in Nigeria. African Journal of Biotechnology. 2012; 11(26): 6918-22.

13. Yap CK, et al. Effects of metal- contamination soils on the accumulation heavy metals in different parts of centellaasiatica: Alaborayory Study. Sains Malaysiana. 2010; 39(3): 347-352.

14. Bais SK, et al. Comparative Evaluation of Heavy Metals in Marketed Haematinic Herbal Formulations by Atomic Absorption Spectroscopy. Asian J. Pharm. Ana. 2014; 4(1): 11-16.

15. Sor AL, et al. Concentrations of heavy metals in farmland soils from selected oil bearing communities in Gokana, Rivers State, Nigeria. Int. J. Res. Sci. Innovation. 2020; 7(5): 173-80.

16. Fatima G, et al. Cadmium in human diseases: It’s more than just a mere metal. Indian Journal of Clinical Biochemistry. 2019; 34(4): 371-8.

17. Nofianti KA, et al. Biosorption of Heavy Metals Cu2+, Cd2+, and Pb2+ by Chitosan and Powder from Capiz shell (Placuna placenta). Research Journal of Pharmacy and Technology. 2025; 18(5): 2155-63.

18. Safa W. AZ. Study of Heavy Metals and their effects on Oxidant / Antioxidant Status in Workers of fuel Station in Hilla city-Iraq. Research J. Pharm. and Tech. 2018; 11(1): 312-316.

19. Ahsan ME, et al. Assessment of heavy metals from pangasius and tilapia aquaculture in Bangladesh and human consumption risk. Aquaculture International. 2022; 30(3): 1407-34.

Received on 08.08.2025 Revised on 10.11.2025

Accepted on 17.01.2026 Published on 10.02.2026

Available online from February 16, 2026

Research J. Pharmacy and Technology. 2026;19(2):542-546.

DOI: 10.52711/0974-360X.2026.00079

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Creative Commons License.