Health Risk Assessment and Determination of Some Heavy Metals in Commonly Consumed Traditional Herbal Preparations in Northeast Ethiopia

Background. Most traditional medicines were prepared from plant origins. *ese plants could be contaminated by heavy metals, pesticides, and/or toxins. *erefore, the aim of the present study was to determine the level of heavy metals such as lead (Pb), cadmium (Cd), chromium (Cr), and copper (Cu) in frequently used traditional herbal preparations sold in Northeast Ethiopia and to estimate their health risks associated with their daily intake.Methods. A total of 6 traditional herbal preparations were randomly collected from local herbal shops of Dessie and Kombolcha town, Northeast Ethiopia. *e samples were prepared for analysis by wet digestion method using nitric acid and hydrochloric acid treatment. *e accuracy of the method was analyzed by the spike recovery test. Determination of Pb, Cd, Cr, and Cu by microwave plasma atomic emission spectroscopy was made in herbal preparations traditionally used in Dessie and Kombolcha town, Northeast Ethiopia. By calculating estimated daily intake (EDI), hazard quotients (HQ), and Hazard Index (HI) of metals, the health risk associated with the consumption of the analyzed herbal preparations was also evaluated. Results.*e levels of heavymetals were in the range of 3.0–3.92mg/kg for Pb, 5.35–10.7mg/kg for Cr, and 0.815–12.3mg/kg for Cu. However, cadmium was not detected in any of the traditional herbal preparations. *is study revealed that the level of Pb and Cu in all analyzed samples was within the WHO maximum permissible limit of 10mg/kg and 40mg/kg, respectively. *e level of Cr in all traditional herbal preparations was beyond the WHO maximum permissible limit (2mg/kg). From the health point of view, the HQ value of Cr for KD-03 and KD-04 is greater than 1, suggesting potential health risk. Furthermore, the HI value had revealed that the consumption of KD-02, KD-03, and KD-04 samples had the potential of posing health risks to consumers over long-term consumption of herbal preparations. Conclusion. *is study showed that most of the metal concentration levels in the herbal products were within the WHO maximum permissible limits. However, all samples had Cr levels above the WHO maximum permissible limit. Based on the results of this study, there would be a noncarcinogenic health risk to the consumer associated with the consumption of some herbal preparations marketed in Northeast Ethiopia.


Background
It is estimated that about 70-80% of the world's population relies on nonconventional medicine, mainly of herbal origin. However; owing to the nature and sources of herbal medicines, they are sometimes contaminated with arsenic, heavy metals (lead, mercury, cadmium, and chromium), pesticides, and/or toxins, resulting in multiorgan damage to the consumers [1].
Traditional and complementary medicine is an important and often underestimated health resource with many applications, especially in the prevention and management of chronic diseases and in meeting the health needs of aging populations [2]. Ethiopia is known for its rich tradition of herbal medicine. Herbs are traditionally used for the treatment and prevention of diseases such as stomach pain, headache, diabetes, hypertension, rheumatism, and many others [3]. ere has been an increasing concern over the safety and toxicity of natural herbal formulations available on the market. In general, herbal preparations can be contaminated during growing, harvesting, and processing. Sources of heavy metal contamination in herbal preparations could be linked to water used in irrigation, polluted soils, fertilizers and pesticides, industrial emissions, transportation, and harvesting and storage processes [3,4]. Metals such as zinc, iron, manganese, and copper are essential elements since they play an important role in biological systems and only become harmful at high concentrations, whereas mercury, lead, arsenic, chromium, and cadmium are nonessential elements as they are toxic, even at low concentration levels [5]. In general, the toxicity of heavy metals is due to the chemical reactivity of the ions with cellular structural proteins, enzymes, and membrane systems [6]. Metals are nonbiodegradable and are cumulative in nature rendering them persistent pollutants [7].
e safety and quality of medicinal herbal products have become a major concern for health authorities, pharmaceutical industries, and the general public. e toxicity of herbal plants may be related to contaminants such as pesticides, microbes, heavy metals, chemical toxins, and adulterants [3,8]. Apart from affordability and availability, the advocates of herbal products believe that they are safe and harmless because of their natural origin without any scientific evaluation. But, most of the herbal products contain a toxic concentration of heavy metals. Heavy metals like lead, cadmium, and chromium are lethal and toxic to humans even at lower concentrations [9][10][11]. Previous studies conducted globally showed that herbal preparations contain heavy metals beyond the World Health Organization (WHO) maximum permissible limit. For example, a study in Nigeria showed that 100% of the samples analyzed contained cadmium above the WHO permissible limits (0.3 mg/kg) and 33% of the samples contained lead above the WHO permissible limits (10 mg/kg) [12]. A study in the United Arab Emirates also suggested that most of the analyzed herbs contained unsafe levels of heavy metals that exceeded the WHO permissible limits (3). A similar study done in North Gondar, Ethiopia, on ten selected medicinal plants indicated that arsenic (20%), cadmium (70%), and lead (30%) were found to contain concentrations above the WHO maximum permissible limit [13].
Among the analytical techniques available for quantifying trace elements in environmental samples, inductively coupled plasma optical emission spectrometry (ICP-OES) is the most powerful and popular technique. It allows multielement analysis with good detection capabilities, wide working ranges, and high sensitivity with relatively high freedom from nonspectral interference [14].
Herbal preparations are becoming widely used in Dessie and Kombolcha town, Northeast Ethiopia, to treat several ailments such as cough, diarrhea, fever, sexually transmitted diseases, sexual impotency, hypertension, cancer, and diabetes. However, there is currently no national policy to guide the regulation and monitoring of the quality and safety of traditional herbal preparations in Ethiopia. erefore, very limited information is available on the safety of herbal preparations sold in the Ethiopian market. Hence, the objective of this study was to assess the level of heavy metals (Pb, Cd, Cr, and Cu) in herbal preparations sold in Northeast Ethiopia and to estimate their health risks associated with their daily intake. , porcelain/ceramic mortar and pestle, grade A volumetric flasks of 50 ml, 100 ml, 500 ml, and 1000 ml (Pyrex, USA), grade A volumetric pipette of 0.5 ml, 1 ml, and 5 ml and a beaker of different sizes (Pyrex, USA), Teflon beaker (plastic wear PTFE beaker, UK), and vortex shaker (Mfr, S1-S1-p236, USA) were used for a multielemental analysis of heavy metals.

Chemicals and Reagents.
Analytical grade chemicals and reagents were used throughout the experiment. Chemicals and reagents used for this particular experiment were hydrochloric acid (37%, Sigma Aldrich product of USA), nitric acid (70%, Sigma Aldrich product of USA), and ultrapure water (Milli-Q TM water system Darmstadt, Germany) used for standard solution preparation. Distilled water and stock solution of standard Pb, Cd, Cr, and Cu (BDH, Chemicals, Ltd., Merck, England) were obtained from the Ethiopian Public Health Institute (EPHI) laboratory, Addis Ababa, Ethiopia.

Study Area and Period.
e study was conducted in Dessie and Kombolcha town, South Wollo zone, Amhara region, Northeast Ethiopia, from October 2019 to July 2020. South Wollo zone is one of the six zones of the Amhara region, Northeast Ethiopia. Dessie, the capital city of South Wollo zone, is 401 km far from Addis Ababa, the capital city of Ethiopia, and 540 km far from Bahir Dar, the capital city of Amhara regional state. Kombolcha is an industrial town in the east Amhara region, Northeast Ethiopia, and is located 18 km far from Dessie town. e major natural vegetation of the study areas is characterized by grassland (grazing areas) and small forests containing mainly acacia trees and shrub species. A large part of the study area is covered with agricultural farm areas. e study areas were selected because traditional herbal products were commonly used by the community to treat chronic diseases such as hypertension, diabetes mellitus, and cancer. According to the city administrative health office report, there are 29 officially licensed traditional practitioners in Dessie and Kombolcha town during this study.

Sample Collection.
A total of six traditional herbal preparations frequently used in the treatment of hypertension, diabetes mellitus, malaria, sexual dysfunction, kidney, and GI problems in Dessie and Kombolcha town, Northeast Ethiopia, were included in this study. Herbal samples were commercially available in powder form in plastic containers. About 150 g of each herbal preparation was purchased randomly from six different herbal shops of Dessie and Kombolcha town from February 1 to 21, 2020. Each collected sample was randomly coded from KD-01 to KD-02 and was stored in polyethylene bags for further analysis [15]. e experimental work for the determination of heavy metals was conducted at the food and drug quality control laboratory of the Ethiopian Public Health Institution (EPHI), Addis Ababa, Ethiopia. Sample code, the composition of herbal preparations, their traditional use, and collection areas are summarized in Table 1.

Sample Digestion and Analysis.
About 150 g of each sample of traditional herbal products was accurately weighed and powdered and homogenized using mortar and pestle. Pyrex grade A volumetric flask glass with standard taper stopper was used for preserving homogenized sample. e six samples were analyzed for their toxic metals concentrations. e digestion of the samples was carried out using the wet digestion method described by Alhusban et al. [16]. From the homogenized powder of herbal preparations, about 1 g of each sample was accurately weighed and transferred to a 50.0 mL Teflon beaker. e sample solution was heated for 1 h at 110°C using a vacuum oven. en, 10 mL of aqua regia solution (a mixture of HNO 3 (70%) and HCl (37%) in (1 : 3) v/v) ratio) was added to a beaker, and the sample solution was heated for 2 h at 240°C until all the samples dissolved completely and a clear and colorless solution was obtained. After digestion was complete, the sample solution was allowed to cool in the air, and 30 mL of distilled water was added. en, the solution was filtered using Whatman filter paper and diluted to 50.0 mL with distilled water. Finally, the concentration of Pb, Cd, Cr, and Cu in each sample was determined using microwave plasma atomic emission spectroscopy. All experiments were carried out in triplicate for precision and accuracy of the results, and blank solutions (containing the only mixture of HNO 3 and HCl) were also prepared following the same procedure used for the samples.

Calibration Curve Procedure.
A pure analytical grade reference standard metal containing 1000 mg/L stock solution of Pb, Cd, Cr, and Cu was obtained from the Ethiopian Public Health Institution. en, 10 ml of stock solution was diluted to 100 mL with water for each metal. Finally, from this intermediate solution (100 mg/L), five working standard solutions of 1, 5, 10, 15, and 20 mg/L were prepared. e calibration curve was constructed by plotting the standard concentration of each heavy metal against the emission intensity of heavy metals. Calibration curve regression equation and their respective correlation coefficients (R 2 ) are presented in Table 2. e concentration of the heavy metals in each sample was determined using linear regression equations obtained from the calibration curve. e concentration of heavy metals in 1 g of each sample in terms of mg/kg was determined using the following equation: where V is the final volume (50 ml) of the digested sample solution and Wt is the initial weight (1 g) of the sample measured for analysis.

Recovery
Test. e accuracy of the method was assessed by spiking herbal samples (1 g) with known amounts of standard metals (1 ppm), and the percentage recovery was calculated. e results were obtained as the average of three replicates of each sample. e results showed the validity of the employed methods and good repeatability for the analysis of herbal samples. As shown in Table 2, the percentage of recovery values ranged from 81.8% to 117.5%. e percent recovery was determined according to the following equation: percent recovery � concentration of spiked sample − concentration of unspiked sample conc. of known spike added × 100.
2.2.6. Health Risk Assessment of Heavy Metals. e risk of intake of heavy metal contaminated herbal preparations to human health was evaluated based on estimated daily intake (EDI) of metal, hazard quotient (HQ), and Hazard Index (HI). e daily intake dose (EDI) was calculated to estimate the average daily metals loading into the body system of a specified bodyweight of a consumer. e value of EDI was determined by the following equation [17][18][19]: where C metal (mg/kg) is an average weighted heavy metal content in traditional herbal preparations, IR (ingestion rate) is the average daily consumption of herbal preparations (ram/day person), and BW is the average body weight (kg). Average daily consumption of herbal preparations (KD-02-KD-06) for an adult is 20 g/person/day while for KD-01 samples it was 10 g/person/day of dry weight. e average bodyweights of adults were considered 65 kg [20]. Hazard Quotient (HQ) is used to assess the noncarcinogenic risk to humans from long-term exposure to heavy metals from vegetables, medicinal plants, and fruits. If HQ is <1, this means that no potential health effects are expected from exposure, while HQ > 1 signifies that there are potential health risks due to exposure. e HQ is calculated as a fraction of the determined dose to the reference dose as shown in the following equation [18,[21][22][23]: where EDI is the average herbal preparations intake per day (mg/kg/day) and RfD is the oral reference dose of the metal (mg/kg/day). RfD is an approximation of daily tolerable exposure to which a person is expected to have without any significant risk of harmful effects during a lifetime. RfD for Pb, Cu, Cd, and Cr is 0.004 mg/kg/day, 0.04 mg/kg/day, 0.001 mg/kg/day, and 0.003 mg/kg/day, respectively (14). Hazard Index (HI) helps to evaluate the overall noncarcinogenic risk to human health through more than one heavy metal. Exposure to more than one pollutant results in additive effects. It is the sum of the hazardous quotient (HQ) of all heavy metals as described in the following equation: [18,19,[22][23][24].
If HQ < 1, there is a possibility of adverse effects on human health [23,24].

Data
Analysis. All quality control measures were taken including calibration check measures, determination of recovery test, and replicate analysis of samples. e data were analyzed using SPSS version 23. e results were expressed as mean ± standard deviation (mg/kg, dry weight) of triplicate analysis.

Determination of Heavy Metals in Herbal Preparations.
e results of this study showed that heavy metals (Pb, Cr, and Cu) were present in varying concentrations in the six herbal preparations commonly used in Northeast Ethiopia. e average concentration of heavy metals in traditional herbal preparations was shown in Table 3. e concentration of lead in herbal samples ranged from 3.30 ± 0.8 to 3.92 ± 0.8 mg/kg (Table 3). e highest and the lowest concentrations were found in KD-06 and KD-01 samples which were used by traditional healers to treat hypertension and sexual impotency, respectively. e WHO maximum permissible limit for lead in traditional herbal preparations is 10 mg/kg [25]. Hence, all samples analyzed were within this permissible limit. Maghrabi reported similar results from different samples of herbal drugs marketed in Saudi Arabia, with the levels of Pb below the WHO permissible limit [26]. However, contrary to this finding, the concentration of lead above the WHO maximum permissible limit was reported in previous studies [12,[27][28][29][30]. Lead is one of the most toxic heavy metals and progressive exposure may cause poor muscle coordination, gastrointestinal symptoms, brain and kidney damage, hearing and vision impairments, and reproductive defects. Lead bioaccumulates in biological tissues; patients who use medicinal herbs with even low concentrations of Pb over a long period of time might be at risk of chronic Pb toxicity and should be monitored for any signs of lead poisoning [3,8,31]. e WHO maximum permissible limit of cadmium in traditional herbal products is 0.3 mg/kg [25]. Cadmium was not detected in any of traditional herbal preparations, i.e.,  below the detection limit of the instrument (0.00028 mg/L) ( Table 3). Similar findings have been reported in Jordan [16] and Bangladsh [32]. However, high levels of cadmium above the WHO permissible limit have been reported in South Africa [29], Iran [28], and Nigeria [12,33]. An intake of high levels of cadmium is known to be very toxic and carcinogenic. Its ingestion at lower levels can accumulate in the kidneys, resulting in renal tract impairment, lung damage, and fragile bones [6,9,29]. In this study, the concentration of chromium was found in the range of 5.35 ± 0.65-10.70 ± 0.27 mg/kg (Table 3). e highest amount was reported in the KD-01 sample while the lowest amount was reported in the KD-05 sample. e level of chromium in herbal products was above the WHO recommended permissible limits (2 mg/kg) [25].
is might be due to contamination of the raw materials used in manufacturing and contamination during the harvesting and manufacturing process of herbal plants. Similar results of high levels of chromium have been reported in a study conducted in South Africa. Exposure to high levels of chromium can result in respiratory tract problems, lung cancer, dermatitis, and permanent nose damage [29]. e health risk due to metal contamination, in general, depends on the average daily dietary intake. Chromium is lethal and toxic to humans even at lower concentrations. e concentration range of copper in tested samples was 0.81 ± 0.08-12.3 ± 0.33 mg/kg as shown in Table 3. e maximum concentration was reported in the KD-01 sample while the minimum amount was reported in the KD-06 sample preparation. is result revealed that the concentration of copper in all traditional herbal products was found below the WHO permissible limit (40 mg/kg) [25]. Similar results were reported in Brazil [24], Nigeria [9], and Ghana [27]. Copper is an essential element for the human metabolic system. It regulates various biological processes like redox reactions, energy production, connective tissue formation, iron metabolism, and synthesis of neurotransmitters [9]. However, chronic exposure to a high concentration of copper causes irritation of nasal mucosa, vomiting, nausea, diarrhea, kidney, and liver damage [9,30].

Health Risk Assessment of Heavy Metals.
Health risk estimation based on the estimated daily intake (EDI) of the heavy metal contaminant is one of the vital health risk assessment tools. It takes into account the frequency and duration of exposure and the bodyweight of the exposed persons. In general, health risk due to metal contamination depends on the average daily dietary intake [17]. e EDI for Cd, Pb, Cr, and Cu was within the tolerable daily intake reference limits for KD-01, KD-02, KD-05, and KD-06. e EDI for Cr was determined to be higher than the tolerable daily intake reference limit for KD-03 and KD-04 (Table 4). e noncarcinogenic risk of heavy metals in the herbal preparations was calculated by the HQ, and the results are shown in Table 5. HQ for noncarcinogenic effects measures the long-term exposure of the heavy metal contaminants present in the herbal preparations. If the HQ value is less than 1, then the exposed consumers are assumed to be safe, and if the HQ value is equal to or higher than 1, it is considered as a level of concern or poses a health risk [18,19,34]. e findings showed that the HQ values for Cd, Pb, Cr, and Cu were all less than 1, suggesting the consumption of these herbal preparations (KD-01-KD-06) poses no health risk due to these metals. However, the HQ of Cr for KD-03 (1.08) and KD-04 (1.04) is greater than 1, suggesting that the long-term exposure to KD-03 and KD-04 samples poses a health risk due to overexposure to chromium (VI) ( Table 5).
If the HI value of any heavy metals in herbal preparations is less than 1, it implies that the exposed population is unlikely to experience any adverse health effect in their lifetime. However, if the HQ is equal to or higher than 1, there is a potential health risk to the exposed population [22,35,36].
e HI values for KD-01, KD-05, and KD-06 were less than 1. is indicates that the combined effects of the heavy metal contaminants present in a particular herbal preparation pose no health risk in the long term for both adults. e HI for KD-02, KD-03, and KD-04 was higher than 1 probably due to a high daily intake of Cr in this herbal preparation. is indicates that long-term exposure to KD-02, KD-03, and KD-04 samples poses potential noncarcinogenic adverse health effects. Chromium (VI) is lethal and toxic to humans even at lower concentrations.

Conclusion
is study aimed to determine the level of heavy metals (Pb, Cd, Cr, and Cu) in widely used traditional herbal preparations sold in Dessie and Kombolcha town, Northeast Ethiopia. e results of this study indicated that most of the heavy metals (Pb and Cu) were found within the WHO permissible limits. Cadmium was not detected in all of the samples analyzed. However, all of the analyzed samples contained unsafe levels of Cr that exceeded the WHO permissible limits. From the health point of view, the HQ value of Cr for KD-03 and KD-04 is greater than 1, suggesting potential health risk. e HI value has revealed that the consumption of KD-02, KD-03, and KD-04 samples had the potential of posing health risks to consumers over longterm consumption of herbal preparations. Based on the results of this study, there would be a noncarcinogenic health risk to the consumer associated with the consumption of some herbal preparations marketed in Northeast Ethiopia. Consequently, a continuous and strict regulatory control is required to ensure the safety of herbal preparations marketed in the study area.

Data Availability
All data are included within the article.

Conflicts of Interest
e authors declare no conflicts of interest.