Physico-chemical and Heavy Metals Assessment of ‘nzu Clay’ and Its Effect on Hairs of Consumers

Physico-chemical and Heavy Metals Assessment of ‘nzu Clay’ and Its Effect on Hairs of Consumers

Chapter One

Aim and Objectives of the Study

This work aimed to evaluate the activity concentration of radionuclides, and physico-chemical properties of ‗Nzu clay‘ at the raw and processed stages and to assess the level of heavy metal exposure in ‗Nzu clay‘ addicts using biological samples (hair).

This aim was achieved through the following set objectives:

Ascertaining the physico-chemical parameters of ‗Nzu clay‘ (swelling power, dispersibility, bulk density, water absorption index, cation exchange capacity and pH);
determining the crystallographic particle size distribution of the raw and finished product of the clay using X-ray Diffraction(XRD);
determining the activity concentration of radioactive elements in ‗Nzu clay‘ using Hyper-pure Germanium Detector and
assessing the level of As, Cd, Cr, Cu, Pb, Ni, and Zn in ‗Nzu clay‘ samples and in the hair of addicted consumers (less than and above five (5) years) of the clay to compare with those of non-consumers of the

CHAPTER TWO

LITERATURE REVIEW

Kaolin

The name ―kaolin‖ is derived from the word Kau-Ling, or high ridge, the name given to a hill near Jau-chau Fu, China, where kaolin was first mined. Kaolin, commonly referred to as china clay, is a clay that consists mainly of kaolinite (85–95%) (Sepulveda et al., 1983; Bish, 1993).

Kaolinite, the main constituent of kaolin, is formed by rock weathering. It is white, grayish-white, or slightly colored. It is made up of tiny, thin, pseudo hexagonal, flexible sheets of triclinic crystal with a diameter of 0.2–12 μm. It has a density of 2.1–2.6 g/cm³. The cation exchange capacity of kaolinite is considerably less than that of montmorillonite, in the order of 2–10 meq/100 g, depending on the particle size, but the rate of the exchange reaction is rapid, almost instantaneous. The process of kaolin formation is called kaolinization (Grim, 1968; Farmer, 2000).

Kaolinite formation occurs in three ways:

Crumbling and transformation of rocks due to the effects of climatic factors(Zettlitz type);
transformation of rocks due to hydrothermal effects (Cornwall type)and
formation by climatic and hydrothermal effects (Mixedtype).

The type of clay mineral formed during the decay of rocks containing aluminium silicates is influenced by the climate, the aluminium/silicon ratio, and pH. Conditions conducive for kaolinite formation are strong dissolution of Ca²⁺, Mg²⁺ and K⁺ ions and the presence of H⁺ ions (pH 4–5) (Parker, 1988; Lee et al., 1999; Balan et al., 2014). It has number of properties relevant to medicine. However, is an excellent adsorbent and will adsorb not only lipids and proteins, but also viruses and bacteria (Lipson and Stotzky, 1983; Farmer, 1998; Frost et al., 2001; Balan et al., 2010).

Kaolin is used in a large number of different cosmetic products, such as eye shadows, blushers, face powders, mascaras, foundations, makeup bases and others. In 1998, kaolin was reported to be used in 509 different cosmetics in the USA, usually at concentrations between 5% and 30%, but reaching 84% in some paste masks (CIREP, 2003). Classification of kaolinite as member in the silicates family is shown in Fig 2.0

Organoleptic and Granulometric Properties of Edible Clays

Cation exchange capacity

The cation exchange capacity (CEC) is the amount of exchangeable cation per unit weight of dry soil that plays an important role in soil fertility, or the amount of negative charge in soil that is available to bind positively charged ions (cations). Hydrogen (H⁺) and aluminum (Al³⁺) ions are the predominant cation occupying the CEC in soils. It depends especially on the pH, clay mineral and on the soil organic matter content. Soil texture also influences the CEC of the clay. Higher quantities of clay and organic matter result to higher CEC. The CEC of a soil is a good indicator of the nutrient holding and buffer capacity of the soil, but in itself is not particularly useful for managing soil properties (James, 2001).

Amounts of negative and positive charges are both expressed in milliequivalents. A milliequivalent takes into account both the weight and the charge of the cation. One milliequivalent of negative charge on a clay particle is neutralized by one milliequivalent of cation.

The predominant clay mineral in most clay soils is kaolinite which has a CEC of 5 meq/100 g. Other clay minerals, such as smectite and vermiculite, have in excess of 100 meq/100 g CEC, but occur in limited amounts in some soils (Ngole et al., 2010).

Bulk density

The bulk density of a powder is the ratio of the mass of an untapped powder sample to its volume including the contribution of the interparticulate void volume. Hence, the bulk density depends on both the density of powder particles and the spatial arrangement of particles in the powder bed. The bulk density is expressed in grams per cubic centimeter (g/cm³), although the international unit is kilogram per cubic meter (1 g/cm³ = 1000 kg/m³), because the measurements are made using cylinders. It may also be expressed in grams per cubic centimetre (g/cm³).

The bulking properties of a powder are dependent upon the preparation, treatment and storage of the sample. The particles can be packed to have a range of bulk densities and moreover, the slightest disturbance of the powder bed may result in a changed bulk density.

The bulk density of a powder is determined by measuring the volume of a known mass of powder sample that may have been passed through a sieve into a graduated cylinder. The bulk density of soil depends greatly on the mineral make up of soil and degree of compaction, soil high in organics and some friable clay may have a bulk density well less than 1 g/cm³ (Miller and Donahue, 1990).

CHAPTER THREE

MATERIALS

List of Apparatus/equipments Top load (Denver instrumentXP-600)

Baird and Tatlock Auto bench centrifuge (weigh in excess of 18.14kg) Analytical weighing balance (Sartorium ED224S, max 220g; d=0.1mg) Jenway pH meter (3505)

Sension 5 Conductivity meter (Hach product) England Hotplate; Jenwang 1000, England

Reciprocating shaker; Line instruments,Inc 3527 AAS – VARIA AA2404FS, England

Hiper Pure Gammanium detector, by Canberra; model GC8023, S/N9744

X-Ray Diffractory machine; Bruker-AXS-type D8 ADVANCE diffractometer, with Cu Ka1 radiation (wavelength 1.5406λ),

Colony Counting Machine; STUART-Scientific Sc5, UK Autoclave; Astell ASB300 England

Incubator; Gallankamp IH-150 England

Hot air oven; D-91126 Schwabach FRG, Germany

List of reagent Calcium chloridedihydrate

Sodium hydrogen tetraoxophosphate (V1)

Anhydrous Magnesium tetraoxosulphate (V1) Potassium chloride

Anhydrous Potassium hydrogen tetraoxophosphate (V1) Sodium chloride

D-Glucose

Phenol red sodium salt Saline Solution

CHAPTER FOUR

RESULTS

Table 4.1 shows some physicochemical parameters of ‗Nzu clay‘ samples, these include: the cation exchange capacity (CEC), bulk density, dispersibility, water absorption index, swelling power and pH of raw and finished clay samples obtained from sites 1 and 2 of hill side in Ozanogogo, Ika south LGA of Delta State and site 3 from Uzella river, Owan west LGA, Edo state.

Table 4.2 shows correlation between similar physiochemical properties of the various sampling sites; site 1R, site 2R are sample codes for raw ‗Nzu clay‘ obtained from two

(2) hill site in Ozanogogo, Ika south LGA of Delta State. Site 1F, site 2F are processed/finished clay from same sites, while site 3F is sample code for ‗Nzu clay‘ obtained from Uzella river, Owan west LGA, Edo state.

CHAPTER FIVE

DISCUSSION

Physicochemical Parameters of the Raw and Processed/Finished ‘Nzuclay’ Samples

The physicochemical parameters of the raw and process ‗Nzu clay‘ samples are presented in Table 4.1. The cation exchange capacity of the raw and finished/processed sample of the ‗Nzu clay‘ from site1 has a mean value of 10.800 ± 0.424 and 10.250 ± 1.202meq/100 g, respectively. This indicates that the processing of the clay which includes salting and heating does not have any significant effect on the ‗Nzu clay‘ samples from site1. Samples from site 2 have a mean value of 10.200 ± 0.989meq/100 g and 9.870 ± 0.671meq/100 g for the raw and finished/processed ‗Nzu clay‘ respectively. This indicates that processing have a significant effect on the cation exchange capacity of the clay samples from site 2 as ions are affected by the processing temperature causing a reduction in the CEC of the processed ‗Nzu clay‘.

The cation exchange capacity of ‗Nzu clay‘ from site 3 has a mean value of 9.725 ± 0.035meq/100 g. This compare significantly to the CEC in finished ‗Nzu clay‘ from site

Raw ‗Nzu clay‘ from site 1 has the highest cation exchange capacity while the processed/finished clay from site 3 have the lowest cation exchange capacity (Table 4.1). The predominant clay mineral in most soil is kaolinite which has a standard CEC value of 5 meq/100 g (James, 2001). The mean CEC value of ‗Nzu Clay‘ in this study exceeds 5 meq/100 Hence, the tendency to exchange its cation with the minerals in the body is high; this is also an index of its high adsorptive capacity for cations and ability to enrich the host with cations.

CHAPTER SIX

SUMMARY, CONCLUSION ANDRECOMMENDATION

Summary

This study indicates that there was significant difference in the concentration of the analyzed metals at (P < 0.05) between the raw ‗Nzu clay‘ and the processed/finished‗Nzu clay‘ as there was disparity in the physico-chemical parameters determined in the clay. The bulk density (g/cm³) of raw and processed/finished ‗Nzu clay‘ had a mean value of 0.72 ± 0.212 and 0.915 ± 0.120 respectively, showing increase in bulk density of the processed clay. Dispersibility (%) in the raw and processed/finished clay was 80.00 ± 1.414 and 74.750 ± 3.880, respectively. This showed decrease in the dispersibility of the processed/finished clay. Water absorption and swelling power of processed/finished ‗Nzu clay‘ obtained from Uzella river have the highest values 2.230 ± 0.000 and 2.070 ± 0.000 respectively. The pH of the raw and processed/finished ‗Nzu clay‘ was 5.150 ± 0.494 and .500 ± 0.141 respectively, showing increased acidity in the clay.

The mean value of CEC of the raw and processed/finished clay range from 9.725 ± 0.035 meq/100 g to 10.80±0.424 meq/100g. This indicates that processing condition have no significant effect at (P < 0.05) on the cation exchange capacity of the clay as ions are unaffected by the processing temperature of the processed ‗Nzu clay‘. There is correlation between the physicochemical parameters at range 98.8% to 100% as shown in (table 4.1)

The concentration of heavy metals in the processed/ finished ‗Nzu clay‘ obtained from the hill side in Ozanogogo, Ika South LGA and Uzella river, Owan West LGA, Edo State had mean ± SEM (mgkg^-1) value of Cd as 1.86 ± 0.03 and 3.83 ± 0.14 respectively, Cr 41.57 ± 2.07 and 65.8 ± 2.50 respectively, Cu 27.56 ± 0.78 mgkg^-1, and 10.10 ± 0.61mgkg^-1respectively, Ni 7.53 ± 0.30 and 4.13 ± 1.00 respectively, Zn 22.47 ± 1.52 and 10.27 ± 1.79 respectively. Heavy metals in the clay samples obtained from the hill and water side exceed the allowance limit for standard soil by (DPR-EGASPIN, 2002) (Table 4.3).

The hair of the addicts of ‗Nzu clay‘ analyzed using Atomic Absorption Spectroscopy, revealed that the addicts of the clay for above 5 yr have the mean value of As being 25.60 ± 1.1mgkg^-1, Cd 4.35 ± 0.82, Cr 112.47 ± 22.9, Cu 4.04 ± 0.72, Ni 7.62 ± 1.46, Pb 2.99 ± 0.68 and Zn 0.17 ± 0.22; while the addicts of the clay for less than 5yr had the mean value for As being 22.44 ± 0.39 mgkg^-1, Cd 2.59 ± 0.09, Cr 66.06 ± 3.18, Cu 0.52 ± 0.38, Ni 3.95 ± 0.08, Pb 1.14 ± 0.04, and Zn 0.12 ± 0.03. This shows increased variation in the concentration of the heavy metals studied at (P < 0.05) as the years of consumption of the clay increased. All the addicts and non addicts of the clay have concentration of the heavy metals in the levels that exceed the recommended dietary allowance in solid food by FAO/WHO and NAFDAC as shown in Table 4.4.

The levels of radioactive elements in the raw ‗Nzu clay‘ indicated that the lowest activity concentration (Bq/kg) of ⁴⁰K, from site 2 was 54.45 ± 32.45,²³⁸U from the clay of site 1 recorded 21.35 ± 6.28 and ²³²Th from the clay of site 1 at Ozanogogo was 26.83 ± 13.94. Furthermore, the processed/finished clay have higher activity concentration (Bq/kg) of ⁴⁰K being 127.60 ± 14.7 from site 1, site 3F (Uzella river) ²³⁸U 38.75 ± 4.67 and site 1 ²³²Th 44.51 ± 1.16. These values indicate that ⁴⁰K had the highest activity concentration (Bq/kg) of 127.60 ± 14.7 in the edible clay samples, while ²³⁸U and ²³²Th had values that are close in range 38.75 ± 4.67 and 44.51 ± 1.16 respectively. The radionuclides detected in ‗Nzu Clay‘ were all lower in levels than the worldwide average values 400, 35 and 30 for ⁴⁰K, ²³⁸U and ²³²Th respectively as stated by (UNSCEAR, 2000).

The mean absorbed dose rate by the ‗Nzu Clay‘ was calculated to be 48.86 nGy/h, this is within the world average which is 60nGy/h according to (UNSCEAR, 2000). The mean value of the Annual Gonadal Equivalent Dose (AGED) in the ‗Nzu Clay‘ was 207.1Sv/y, which is relatively high and could pose risk to the activity of the bone marrow and the bone surface cells. The values of the radium equivalent activity index, representative Gamma Index (Iyr), external hazard index (Hex) and internal hazard index (Hin) were less than unity, this indicated that there is a negligible health hazard in consuming the

‗Nzu Clay‘ from Ozanogogo.

X-ray diffraction of ‗Nzu Clay‘ sample on CuK_α in the 2θ region, glancing angle 15º – 75º in the raw and finished ‗Nzu Clay‘ investigated for the mineralogy reveals that the

‗Nzu clay‘ is dominantly composed of the mineral kaolinite, compound name; aluminium silicate hydroxide (Al₂Si₂O₅(OH) ₄) and quartz, silicon (IV) oxide (SiO₂).

Conclusion

‗Nzu clay‘ obtained from the hill of two sites in Ozanogogo, Ika South LGA, Delta State and one site in Uzella river, Owan West LGA Edo State revealed that the health risk could result from the high levels of some studied heavy metals that were above the threshold limits. Heavy metal contaminant in ‗Nzu clay‘ obtained from the water side were in the order of Zn ˃ Pb ˃ Cu ˃ Ni ˃ Cr ˃ Cd; while in the ‗Nzu clay‘ from the hill side had the metals in the order: Cr ˃ Cu ˃ Zn ˃ Pb ˃ Ni ˃ Cd. Heavy metals obtained from the hill and water side had exceeded the tolerable limit in soil (WHO, 2010) and (DPR, 2002).

Results derived from analysis on the hair of the addicts greater than 5yr and less than 5yr in comparison with those in the non-addicts show discrepancies at (P < 0.05), the heavy metal concentrations in addicts greater than 5yr were higher than the concentration of heavy metals in addicts less than 5yr, while addicts of the clay less than 5yr have higher concentration of heavy metals than the non addicts. As, Cd Cr Cu Ni Pb were all higher in concentrations than the permissible limit set by WHO/NAFDAC, except for Zn which was lower than the permissible limit of 15 mgkg^-1 by WHO/NAFDAC and does not reflect bioaccumulation which may be as a result of the essentiality of Zn in the human body and the CEC of the clay.

Radioactive elements ⁴⁰K, ²³⁸U and ²³²Th in the ‗Nzu clay‘ are within the tolerable limit of 400, 35 and 30 Bq/Kg respectively by (UNSCEAR, 2000).The calculated mean value of health hazard indexes; absorbed dose rate, annual gonadal equivalent dose (AGED), radium equivalent activity index, representative Gamma Index (Iyr), external hazard index (Hex) and internal hazard index (Hin) were all within the world mean range. However, continuous consumption of the clay over the years can be biomagnified which may result to risk of fatal cancerous growth in organs of addicts of the clay.

Most of the clay samples obtained from the three sites were predominantly a mixture of the mineral kaolinite Al₂Si₂O₅(OH)₄ and quartz, SiO₂. The presence of the minerals;

Kaolinite and Quartz may account for the reason why ‗Nzu clay‘ have a unique flavor and taste which appeals to the appetite than the other clays with other minerals such as halloysite, illite, mica, bentonite and feldspar that are not ingested by man. All the clay samples varied in texture, aroma, taste and colour.

This study shows that most of these elements in the clays are far above the WHO standard which could lead to toxicity of the body and result to result to gastrointestinal disorder, kidney failure, reduced pregnancy length, intelligence decline in children, brain disorder and even death.

Recommendation

The recommendations made from the findings of the study are:

Further research should be carried out on the concentration of heavy metals in addicts of ‗Nzu clay‘ using blood and nails as bioindicator to compare with findings made from using hair as bioindicator in this
Mines should not be located where these edible clays are naturally sited or processed to avoid exposure to harmful
The study also recommends that the consumption of ‗Nzu clay‘ be continually banned and the ban enforced by the law enforcement agencies such as NAFDAC, ministry of environment and ministry of health, since the presumed benefits is out-weighed by the high levels of toxic heavy metals in the clay and in the hair of the addicted consumers likewise the microbial

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