DETERMINATION OF HEAVY METALS (Co, Cu,Cd,Fe, Pb, Zn) IN SOME EDIBLE INSECTS AND FINGERLINGS IN DUTSIN-MA TOWN

Assessment of some carcinogenic (Cd and Pb) and non-carcenogenic (Co, Cu, Fe and Zn) heavy metals elements was carried out on fingerling, grasshopper, locust and termite. These organisms were selected for this study because they are regarded as alternative source of protein and recently as traditional medicine. Hence it became imperative to assess their human health risk. The result analyzed show that cobalt level ranges from 1.85±0.16 mg/kg to 9.03±0.54 mg/kg, copper from 18.56±0.01 mg/kg to 78.02±2.35 mg/kg, iron from is 176±12.55 mg/kg to 390.37±10.95 mg/kg, cadmium1 from74±0.00 mg/kg to 7.11±0.89 mg/kg, lead from 0.04±0.08 mg/kg to 1.14±0.49 mg/kg and zinc 244.15± 10.30 mg/kg to 281.48 ± 45.52 mg/kg. These were determined using atomic absorption spectrophotometer (AAS) and were compared with FAO/WHO standards. And all were above the recommended level except lead (Pb). Fingerling which is the only aquatic organism among the samples was found to contain higher amount of Co, Cu, Fe and Pb. It could be attributed to more interaction with its habitat and usually improper disposal of waste, use of fertlizers and manure among other things may be responsible for that. Hazard indices (HI) were all high and ranges from 5 to 9 and 16 to 31 for adults and children respectively. Cancer risk (TR) assessments of Cd and Pb were categorized as moderate and low respectively according NYSDOH. Public should therefore avoid eating these organisms because the heavy metals in them may bioaccumulate and manifest adversely.


INTRODUCTION
Heavy metals are persistent as contaminant in the air, water and soil and come to forefront of dangerous substances causing health hazard in human. Mining and smelting ferrous ores, the surface finishing industry, energy and fuel production, fertilizer and pesticide industries and applications are artificial causes of these problem (ZL He et al., 2005). Hence, the need to provide guidelines and specifications on many industrial activities so as to checkmate heavy metal pollution in the environment. This could be achieved through the use of cleaner technology which may involve change in raw material input, product formulation and the manufacturing technology. Banning the use of substances that are pollutants or their precursors should be enforce by international community. Heavy metal pollution was less pronounced prior to the technological age, it is mainly due to bush burning, flooding, weathering and volcanic eruptions (Tchounwou et al, 2012). Human activities contribute very little. The pollution that occurs due to it is less and affects only soil, being essential for agriculture. Plants grown in that soil as well as the animals including man that feeds on them tends to accumulate the heavy metals in their tissues with subsequent adverse effect being manifested. ( Bradl H, 2005). Some heavy metals like Cu, Co, Zn, Fe, and Mn are essential metals for enzymatic activity and many biological processes but only when they are present at low concentration (Tchounwou et al., 2012). However, Cd and Hg have no any beneficial role in the body of living organisms and even at low concentrations are toxic (Balali-Mood et al., 2021). Insects are the most widely spread group of organisms in the animal kingdom, making about 76% of known species of living animals (Ajai et al.,2013).Insects appear to be attractive, apart from being a source of food to many vertebrae animals, such as birds, reptiles, amphibians, insectivorous plant and other mammals (Banjo et al., 2010). Historically, they are traditionally part of human diet in Africa, Colombia, Venezuala, Asia and Latin America (Ruddle, 2006;Chavunduka, 2010). Grasshopper, termites, caterpillars and beetle grubs constitute the most important class of insects used as poor man protein in different parts of Nigeria (Banjo et al., 2006;Ifie and Emeruwa, 2011). Butterflies and grasshoppers also have ecological fidelity and are sensitive to environmental changes and quality. According to Chen and co-workers, 2008 these insects have been successfully used as bioindicators for environmental pollution and heavy metal contaminations near industrial states and even within urban areas. High amount of protein, vitamins and mineral contents are the main reasons for high consumption of insects as food (Ledger,2010).They also reduce serum cholesterol and serve as haemostatic agent which helps in tissue repairs and for accelerating the healing of wounds due to its chitin content (Defoliart, 2007;Goodman,2011). Even though insects consumption has many benefits but care must be taken in their processing to checkmate toxic, pathogens and other antinutritional substances present (Birgit and Oliver, 2013). Bioaccumulation of heavy metals in tissues mostly occurs from direct ingestion in food from the digestive tract. Depending on the toxicity and concentration of the metal present, this leads to malfunctioning of the affected organ or tissue. Some metals are highly toxic even in relatively low doses (Polechonska et al., 2007). The adverse effects caused are ionic and mineral imbalance, induce oxidative damage to cell structures, produces injury to DNA and induce cancer transformation (Tchounwou et al, 2012).

MATERIALS AND METHODS Study Area
Dutsin-ma town is on the latitude of 12.4545⁰N and a longitude of 7.4977⁰E with altitude of 543.267m. It has a dam called Dutsin-Ma Dam apart from having tributaries to Zobe Dam which is very close. Hence farming, fishing and irrigation are the main agricultural activities in the area. Cattle rearing by Fulani along the river bank is also very common.

Chemicals and Reagents
All the chemicals and reagents were of analytical grade and were purchased from Sigma Aldrich or Merck (Germany).

Sample preparation
Samples were dried to a constant weight in an oven before been pounded to powdered form using a porcelain pestle and mortar, and then sieved, labelled and stored (Sadi, et al 2021). It was further treated by taken 1 g each of the powdered sample into 100ml beaker followed by the addition of concentrated HNO3, H2SO4 and 37% HClO4. The mixture was placed on a hot plate at 80⁰C and heated in a fume cupboard (Blessing et al., 2020). The heating was stopped after the appearance of white fumes and when the solution became clear, signaling complete digestion (Ahmed et al, 2015). It was then allowed to cool, and then filtered using Whatman No.1 filter paper into a 100 ml standard flask, and then added up to the mark with deionsed water, and then taken for AAS analysis.

Statistical Analysis
The data obtained was analyzed using IBM SPSS Statistics Software Version 23 and the results were expressed as Mean ± Standard deviation (SD). Average concentration of the metal in the samples was compared using one-way analysis of variance (ANOVA), confidence level of 95% and significance level of 0.01 ( Sadi et al.,2021).

Health risk assessment
The long term effects of these heavy metals due to consumption of these edible insects and the fingerling was

RESULTS AND DISCUSSION
The concentrations of the heavy metals determined were carried out in triplicate and presented in mg/kg as mean ± SD in Table 1 below: As can be seen from Table 2, above the mean and standard deviation gotten from ANOVA, confidence level of 95% and significance level of 0.01 were displayed. The concentration of cobalt varies from 1.85±0.16 to 9.03±0.54 mg/kg. Fingerling samples have the highest value (9.03±0.54 mg/kg) with termite being the least (1.85±0.16 mg/kg). This is due to higher transfer factor in aquatic habitat than in soil and air. The same trend was also observed in copper. Here it ranges from 18.56±0.01 to 78.02±2.35 and it is quite lower than that reported by Ajai (2013). Copper despite being an essential micronutrient that is used by human body for production of blood but when in an amount greater than recommended by WHO/FAO cause adverse effects to kidney, liver, stomarch and aneamia (Raymond A.Wuana1 and Felix E. Okieimen,2011). Concentration of iron in termite and fingerling are 176±12.55 and 390.37±10.95 mg/kg respectively. It is lower compared to those reported by Ajai (2013) and Bodenheimer (2005) which was 574.75±30.75 to 205.30±32.45 mg/kg and 320 to 747 mg/kg respectively. Iron is an essential micronutrient needed by the body for oxygen transportation as a component of hemoglobin molecule in red blood cells but tends to be harmful when present above the FAO/WHO recommended limit, due to the formation of free radicals which damage the liver (Ekpo et al., 2010). Cadmium concentrations were found to be 1.74±0.00 to 7.11±0.89 mg/kg. Grasshopper has the highest value, while that of fingerling is slightly lower that the value reported by Blessing et al 2020. Differences in the habitat and feeding mode may be responsible for these variation as rightly pointed out by Ajai et al., 2013. Cadmium despite having uses such as in batteries, pigments, metal coatings, electroplating and effects (Sabine Martin and Wendy Griswold 2009); rarely occurs naturally in soil and minerals such as sulphide, sulphate, carbonate, chloride, and hydroxide salts as well as in water. High levels of Cd in water, air, and soil can occur following industrial activities which may result in substantial human exposure to Cd (Mahdi Balali-Mood, 2021). Moreover, the ingestion of contaminated food will cause major exposure to Cd. International Agency for Research on Cancer (IARC) categorized it as human carcinogenic (Group 1) (Kim et al, 2020). The mechanism of its toxicity is through production of dispositional tolerance by binding to metallothionein (MT) protein (Mahdi Balali-Mood, 2021). This complex formed is very toxic for the kidney. Cadmium also mimic the function and behaviour of essential metals such as zinc and iron in the body (Schaefer et al, 2020). Cdinduced liver injury may be associated with the disturbance of calcium (Ca) homeostasis (Chen et al.,2019). Like cadmium, lead is also carcinogenic (Sultana et al., 2017). Its concentration ranges from 1.14±0.49 to 0.04±0.08 mg/kg. As can be seen from Table2, fingerling samples were found to contain the highest amount of detected heavy metals. These values are lower than those reported by Blessing et al.,2020. Lead can adversely affect every organ and system in the body. Acute effects in adults include decreased performance in some tests that measure functions of the nervous system; weakness in fingers, wrists, or ankles; small increases in blood pressure; and anemia.While chronic effects damage brain and kidney, miscarriage and even death (Sabine Martin and Wendy Griswold ,2009). Zinc is one of the nutrient elements needed by human body for proper functioning when present in small amount (Sadi et al.,2021).Grasshopper contains 281.48 ± 45.52 mg/kg, locust 274.74±79.39 mg/kg, termite 259.34±16.10 mg/kg and fingerling with the least value of 244.15± 10.30 mg/kg. They were higher than that reported by Ajai et al., 2013. Among these, only zinc concentration show very little variation in all the four insects. This could be associated with the abundant amount of zinc present in the soil of the studied area. Differences in the geographical locations is the main attribute of these variations apart from inter-elemental interactions (Quin,2005).

Human health risk assessment
Estimated daily intake (EDI), Target hazard quotient (THQ), Hazard index (HI) and Target cancer risk (TR) values of metals through the consumption of these insects and fingerling are given in Table 3 below:

Estimated daily intake ( EDI )of heavy metals
The daily intake of heavy metals by human beings determine their toxicity level .The EDI of carcinogenic and noncarcinogenic heavy metals for samples of the study area is listed in Table 3.The values computed were very for all samples and all metals except Pb. Iron as the element with the highest EDI value and in all cases fingerling contains the highest value. Besides EDI of heavy metals in children was found to be higher than in adult as observed. Hence, the need for health risk concern for consuming these insects and the fingerling.

Target Hazard Quotient (THQ )
THQ takes care of only one heavy metal despite the fact that many heavy metals could be present in a particular food as shown by the result of this study. This necessitate the need to evaluate hazard index(HI), which the summation of all metals THQs (Javed and Usmani, 2016).The non-cancer risk ( THQ and HI ) values should be less than 1 otherwise there is need for alerting for public health concern. (Islam et al., 2014;Zodape 2014). From the table 3 all the samples show a high risk level ( HI >1 ) for both adults and children. Iron, zinc and copper contributed greatly to this high level.

Target Cancer Risk ( TR )
This parameter measures the cancer risk of the concerned of the heavy metal.Cd and Pb are potent carcinogenic agents according USEPA,2012.The TR is low if are described as low if ≤ 10 -6 , moderate ranges from 10 -4 to 10 -3 , high 10 -3 to 10 -1 and very high is ≥ 10 -1 ( NYSDOH,2007).TR is similar to THQ as an estimated lifetime cancer risk but not an exact estimate of expected cancers(Javed and Usmani ,2016).It is an upper limit probability that individuals exposed to the toxicant may develop cancer (Sultana et al.,2017).From the