HEAVY METAL CONTENT AND ASSOCIATED HEALTH RISKS IN SELECTED ENERGY DRINKS SOLD IN BIRNIN KEBBI, NIGERIA

nergy drinks are sold worldwide because they boost physical and mental performance. However, studies show that some of them contain high levels of heavy metals, prompting a safety evaluation of all brands of energy drinks. This study evaluated the safety of three brands of energy drinks (Fearless, Monster, and Power Horse) sold in Birnin Kebbi, Nigeria, with regard to heavy metal concentrations. The heavy metals evaluated are iron (Fe), copper (Cu), cadmium (Cd), zinc (Zn), and lead (Pb). Samples of the energy drinks were subjected to atomic absorption spectroscopy, and the results were compared with the World Health Organization standards for drinks. The average daily intake (ADI), hazard quotient (HQ), and carcinogenic risk (CR) of the heavy metals were also calculated. The levels of Fe, Cu, and Cd were above the permissible limits in all the energy drinks, while zinc (Zn) and lead (Pb) were below the permissible limits. The ADI of the heavy metals in the three energy drinks was within the recommended limits. However, the HQ and CR of Cd in all the energy drinks and Pb in Power Horse were beyond the recommended limits (HQ > 1 and CR > 10). This suggests that the three energy drinks sold and consumed in Birnin Kebbi may pose health hazards. There is a need to sensitize consumers in the city about the occurrence and risk of heavy metals in energy drinks.


E
Energy drinks refer to beverages that contain, besides calories, caffeine in combination with other presumed energyenhancing ingredients such as taurine, herbal extracts, and B-vitamins (Hardy et al., 2017). Energy drinks first appeared in Europe and Asia in the 1960s in response to consumer demand for a dietary supplement that would result in increased energy (Erdmann et al., 2021). Taisho Pharmaceuticals, a Japanese company, introduced Lipovitan D, one of the earliest energy drinks, in 1962, and it continues to dominate the Japanese market today. Energy drinks are part of the functional beverage category, which also includes sports and nutraceutical drinks (Alsunni, 2015). Heavy metals such as copper (Cu), iron (Fe), manganese (Mn), zinc (Zn), lead (Pb), and cadmium (Cd) can be found in energy drinks (Kilic et al., 2018;Golam et al., 2021).
Heavy metal contamination in energy drinks and other foods is frequently caused by environmental and industrial contamination (Izah et al., 2017). Plant materials are commonly used as an active ingredient in beverage manufacture.
For example, plant-based hops and cereals are used in the production of beer, and the soil in which they are grown may be contaminated by pesticides and fertilizers that may contain traces of heavy metals (Ubuoh et al., 2013). During manufacturing and packaging, energy drinks may also become contaminated (Magomya et al., 2015). Heavy metals are classified into two categories: essential and non-essential. Essential heavy metals are important for human health and the health of other living organisms (Izah et al., 2016). However, essential heavy metals can be harmful to living organisms if their concentration exceeds the organism's tolerated limit (Izah et al., 2016). Even at low concentrations, non-essential heavy metals may be hazardous to the body's cells. High levels of heavy metals can cause biological pathways in the blood, colon, liver, kidney, skin, and cardiovascular systems to malfunction. Individual reactions to heavy metal exposure can be influenced by nutritional status, metabolic rate, the integrity of detoxification pathways, the route and degree of heavy metal exposure, and age (Ogunlana et al., 2015).
Thus, assessment of heavy metals in various brands of energy drinks sold in every locality is necessary to ensure consumer safety (Magomya et al., 2015). To the best of our knowledge, no study has evaluated the levels of heavy metals in various brands of energy drinks sold in Birnin Kebbi, Nigeria. This study, therefore, assessed the levels and health risk of heavy metals in three brands of energy drinks (Fearless, Monster, and Power Horse) sold in Birnin Kebbi, Nigeria.

DESCRIPTION OF STUDY AREA
This study was conducted in Birnin Kebbi, Northwestern Nigeria. Birnin Kebbi is the capital of Kebbi State and the administrative center of the Gwandu Emirate, located at latitude 12° 27' 57.8808" N and longitude 4° 11' 58.2864" E (World Atlas, 2015). The city had an estimated population of 125,594 in 2007. Kebbi is dominated by the Hausa and Fulani tribes (The World Gazetteer, 2007). Kebbi State was created out of the old Sokoto State in 1991. The state is divided into four emirates (Gwandu, Argungu, Yauri, and Zuru) and twenty-one local government areas .
The natural vegetation of the state is an intermix of Sudan and the Guinea Savannah. However, long-term anthropogenic activities have changed the natural vegetation of the area. On average, Birnin Kebbi has a monthly and annual rainfall of 112.21 mm and 787.53 mm, respectively, with rainy seasons spanning through April and October, and reaching peak periods in June, July, August, and September. The average temperature is 260 C, but could rise above 400 C in the peak of the hot season (March-July) and fall as low as 210 C during harmattan, between December and February .

SAMPLE COLLECTION
Ten (10) samples each of Fearless, Monster, and Power Horse energy drinks (a total of 30) were randomly purchased every other week in Birnin Kebbi between March 2021 and April 2021. In between the mentioned months, four field samplings were made, resulting in the overall collection of 120 samples of the energy drinks. The batch numbers of the samples of each brand of energy drink differed from one sampling week to another. The selection of the three brands of energy drinks was based on the most popular brands consumed by high and low-income earners in Nigeria. Samples were stored in almost the same conditions, similar to those of retail shops before heavy metal analysis.

HEAVY METAL ANALYSIS
The heavy metals in the samples were analyzed as described by Yahaya et al. (2012). Exactly 15 ml of each sample was added to 15 ml of distilled water and 15 ml of concentrated nitric acid in a beaker. The beaker was heated gently till the total volume was reduced to about 15ml to break the complex bonds and release the sample into solution. Red fumes were observed, indicating the release of nitric acid. The solution was filtered into another beaker, made up to 50 ml with distilled water and mixed thoroughly. The samples were left to settle before being analyzed for zinc (Zn), cadmium (Cd), lead (Pb), copper (Cu), and iron (Fe) using the PG-990 atomic absorption spectrophotometer (AAS).

QUALITY ASSURANCE AND CONTROL
Glassware and plastic materials were washed with detergent solution and rinsed with deionized water. The materials were thereafter sterilized with 10% nitric acid and rinsed again with deionized water. To ensure the accuracy of all values, the background contamination of the samples was checked by analyzing black samples after analyzing five samples, and all analyses were replicated three times. The reproducibility of the values was at a 95% confidence level. All the chemicals used were of high analytical grade.

HUMAN HEALTH RISK ASSESSMENT
The health risk of daily consumption of the energy drinks was calculated from the average daily intake (ADI), hazard quotient (HQ), and carcinogenic risk (CR) of the heavy metals in the drinks.

AVERAGE DAILY INTAKE
Equation 1 was used to calculate the average daily intake (ADI) of heavy metals from the drinks (Magomya et al., 2015). Table 1 shows the standard values for calculating the ADI of heavy metals (Yahaya et al., 2021). Oral reference doses for Zn, Cu, Pb, Fe, and Cd are shown in Table 2

HAZARD QUOTIENT
The hazard quotient (HQ) of oral exposure to heavy metals in the energy drinks was calculated using equation 2 (Masok et al., 2017). Table 1 shows the standard values for calculating the HQ of oral exposure to heavy metals (Yahaya et al., 2021). A hazard quotient of 1 or lower means that adverse non cancer effects are unlikely, and thus it can be considered to have a negligible hazard (Adepoju and Ojo, 2014).
From equation 2, HQ is the hazard quotient of daily ingestion of heavy metals, Cdrink represents the concentration of a heavy metal in an energy drink, IR shows the ingestion rate per unit time, EF indicates the exposure frequency, ED reveals the exposure duration, AT is the average time, BW indicates the body weight, and RfD (oral) denotes the oral reference dose.

CARCINOGENIC RISK
The CR of oral exposure to heavy metals in the energy drinks was calculated using equation 3 (Iwuanyanwu and Chioma, 2017). Standard values for calculating the CR of exposure to heavy metals are shown in Table 3 (Masok et al., 2017). The range of CR that is acceptable or tolerable is ≤ 10 -6 (USEPA, 2011).

CR = CSF × ADI
Equation 3 From equation 3, CSF is the cancer slope factor.

DATA ANALYSIS
Data obtained from various energy drink samples were presented as mean ± standard deviation (SD). The average daily intake (ADI), hazard quotient (HQ), and carcinogenic risk (CR) were calculated.

HEALTH RISK ASSESSMENT OF THE ENERGY DRINKS
The average daily intake (ADI) of heavy metals from the energy drinks is shown in Table 6. Compared with the recommended limits (RDI), the ADI of all the evaluated heavy metals was within the recommended limits.  Table 5 shows that samples of the three brands of energy drinks contained non-permissible levels of two or more of the evaluated heavy metals (Cu, Pb, Fe, and Cd), except Zn. This suggests that daily consumption of the energy drinks might predispose consumers to health hazards. Excessive levels of heavy metals can cause many health problems, including impairment of mental and neurological functions, neurotransmitter production and utilization, and alter numerous metabolic processes (Balali-Mood et al., 2021). The result of the current study is consistent with that of Salako et al. (2016), who detected permissible levels of Zn in samples of Schappes energy drink purchased in Lagos, Nigeria. The result is also in line with those of Izah et al. (2017) and Udota and Umuodofia (2011), who reported high concentrations of heavy metals including Cu and Cd above the recommended limits in certain energy drinks in Nigeria. Moreover, the result is consistent with Magomya et al. (2015), who detected permissible levels of Pb in some alcoholic and non-alcoholic beverages purchased in Nigeria.
Tables 7 and 8 further show that the hazard quotient (HQ) and carcinogenic risk (CR) of Cd in all the energy drinks as well as Pb in Power Horse were beyond the recommended limits. This finding again proved that energy drinks can induce toxicity. Because the risk was calculated using life expectancy, it may be more dangerous to consumers who live beyond the average life expectancy of Nigerians (55 years). The finding also indicates that Cd and Pb pose more risk to consumers than other evaluated heavy metals. Cadmium is highly toxic and exposure to the heavy metal can cause cancer and target the body's cardiovascular, renal, gastrointestinal, neurological, reproductive, and respiratory systems (Kim et al., 2020). Abnormal levels of Pb may cause high blood pressure, vitamin D and calcium metabolism imbalances, neurological disorders, and multi-organ damage (Popoola et al., 2019). Although the HQ of other heavy metals was within the permissible range, in strict toxicological terms, there is no safe level for heavy metals. These heavy metals can combine additively and pose a significant risk to those who are exposed (Yahaya et al., 2021).

RECOMMENDATIONS
Based on the findings of this study, the following are recommended:  Consumers should be sensitized on the occurrence and risk of heavy metals in energy drinks.
 Agencies responsible for monitoring the safety of food and drinks, such as the National Agency for Food and Drug Administration and Control (NAFDAC), should compel the producers of energy drinks to do quality control.
 Similar studies are needed to ascertain the health safety of other energy drinks.      Values were expressed in mg/L, RDI = Recommended daily intake (mg/L); WHO = World Health Organization