OCCURRENCE OF ORGANOCHLORINE PESTICIDES IN SOILS AND FOODS FROM COTTON FIELDS AND RELATED HEALTH RISKS IN THE HAMBOL REGION (CÔTE D’IVOIRE)

Organochlorine pesticides derived from the chlorination of cyclic and/or aromatic hydrocarbons. But, due to their persistence in the environment and their bioaccumulation in the body leading health problems, they were banned from using.They have been widely used around the world in agriculture and public health in particular in Côte d’Ivoire. This study was aimed to determine the concentrations of organochlorine pesticides residues in soils and crops from Hambol region (Côte d’Ivoire) and to evaluate the potential carcinogenic risk based on the concentrations found.Organochlorine pesticides residues were determined in soils and crops in cotton fields by using an HPLC. Soil samples analysed showed the presence of five organochlorine pesticide residues namely DDT (ND - 0.39 µg/kg), lindane (ND - 0.972 µg/kg), α-endosulfan (ND - 0.481 µg/kg), β-endosulfan (ND - 0.435 µg/kg) and sulfate-endosulfan (ND - 0.44 µg/kg). In crop samples, no pesticides were detected. The concentrations of detected organochlorines in soil samples were less than United States and FAO maximum residues limits for agricultural soils. The cancer risk assessment and hazard quotient values are under 10 -6 and 1. The risks related to farmer exposure to DDT and lindane from soil via ingestion, inhalation and dermal route is negligible. objective this study was to assessment the concentration of organochlorine pesticides residues in soil and crops samples from cotton growing area and the health risk related the soil contamination. Five pesticides (lindane, DDT, α and β-endosulfan and sulfate-endosulfan) were detected with a frequency of 80% in all soil samples analysed, but not in crops samples. The concentrations found in soil samples were under United States and FAO maximum residues limits for agricultural soils. The cancer risk assessment and hazard quotient values are respectively below 10 -6 and 1. The risks related to farmer exposure to DDT and lindane from soil via ingestion,


ISSN: 2320-5407
Int. J. Adv. Res. 8 (12), 411-420 412 Indeed, cotton is one of the most parasitized plants in the world (attacked by more than 500 species of insect pests in Africa) (FIRCA, 2015). In the absence of protection, production losses can be as high as 70% (Sarr et al., 2016). Several pesticides have been used in cotton fields, including organochlorine pesticides that persist in the soil and can be transferred to the plants especially accumulating in the underground parts. Thus, the use of land, where organochlorines have been applied, for the production of food crops; could constitute a health risk.
Hambol region is part of the Ivorian cotton basin and production areas for food crops such as yams, cassava and groundnuts.
The objective of this study is to assess organochlorine pesticides residues in soils and crops from Hambol and to evaluate the potential carcinogenic risk based on the concentrations found.

Figure 1:-Study area representation.
Sampling: Collection and pre-treatment of soil samples: Samples were taken from two types of cotton fields: historical and current cotton fields. A total of 15 soil samples were taken from the entire field at a depth range from 0 to 30 cm using the method described by Mawussi (2008). All portions of soil collected were mixed together to form a sample of at least 500 g per site which was wrapped in aluminium foil, placed in a freezer bag and transported to the laboratory in a cooler for analysis. The samples were dried at room temperature for 2 days, then sieved with a 2 mm sieve, wrapped with aluminium foil and placed in freezer bags and stored in the freezer at -18°C pending chromatographic analysis.

Collection of crop samples:
Crop samples were collected at the same time as soil samples using the method described by Aïkpo et al. (2016). Mature tubers were removed from the stalk, separated from the top, cleaned (to remove roots and adsorbed soil) and separated from the pedicle (so as to retain a pseudo cone corresponding to the central portion of the tuber). For the groundnut samples, the pods were just pulled from the plants and cleaned. A minimum portion of 200g was wrapped 413 in aluminium foil and then bagged 1 litre freezer bags. The samples were placed in situ in a cooler and then frozen in the laboratory waiting analysis.

Physicochemical and particle size characterization of soil samples:
On the dry and sieved samples (at 2mm), different parameters were determined.
Water pH and KCl pH were determined by the AFNOR method using a pH meter in a soil suspension diluted at 1:5 (volume fraction) in water (pH H2O ) and in a potassium chloride solution at 1 mol/L (pH KCl ) (AFNOR, 2005). After treatment of the samples with ammonium acetate, the cations Ca 2+ , Mg 2+ and K + were determined with the atomic absorption spectrometer. Total nitrogen was determined by the classical Kjeldahl method (Bremner, 1965), and organic carbon by the Walkley-Black method (Walkley, 1947). The organic matter content was determined by multiplying the organic carbon content by 1.72. Physical analysis in five particle size fractions (clay, fine and coarse silts, fine and coarse sands) was carried out by the Bouyoucos method (Bouyoucos, 1951). The USDA (United State Department of Agriculture) texture triangle was used for the classification of soil texture.

Determination of pesticide residues in soil and crop Samples: Chemical reagents:
The reagents used are all HPLC grade. Methanol and N-hexane were purchased from VWR. Acetonitrile and dichloromethane were purchased from CARLO ERBA.
Sample treatment and pesticides extraction: 50 g of soil, finely crushed with a porcelain mortar and sieved on a 0.5 mm mesh sieve, was taken and introduced into an Erlenmeyer flask. Then 100 ml of dichloromethane was added and the mixture was vortex homogenised for 1 hour. The homogenization was followed by filtration on Whatman paper with a diameter 90 mm and the filtrate was evaporated dry with BUTCHI brand rotavapor at a temperature of 40°C. The dry residue was recovered with 5 ml of hexane and transferred to a vial for injection by HPLC.
Pesticide residues were extracted, in the same manner as with the soil samples, from 50 g of crushed cassava, yam or groundnut in a blender.

Detection and quantification of pesticide residues:
Pesticide residues analysis was performed using a SHIMADZU high performance liquid chromatograph coupled with a SPD-20A UV/VIS detector.The columns used were Spherisorb S5ODS2 250 x 4, 6 mm ID with a wateracetonitrile mobile phase (10: 90 v/v) for DDT and endosulfan and C18 type, 300 mm x 3.9 mm x 5 µm with a water-acetonitrile mobile phase (50: 50 v/v) for lindane. The analytical conditions were as follows: wavelength 254 nm (DDT and lindane) and 273 nm (endosulfan), oven temperature 30°C, flow rate 1 ml/min, gradient mode, analysis time 15 min, injection volume 20 µl for DDT and endosulfan and 10 µl for lindane.

Statistical analysis:
Excel and STATISTICA version 7.1 software were used to generate the averages. A one-factor analysis of variance (ANOVA) was used to show significant differences and similarities between physico-chemical characteristics and between pesticide concentrations found. The significant means obtained were separated by the Newman-Keuls test at a significance level of 5%.

Health risk assessment of DDT and lindane in the soil:
Human routes exposure to soil contaminants are: direct ingestion of substrate particles, dermal absorption of particles adhering to exposed skin, and inhalation of resuspended particles through the mouth and nose.

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In this study, the health risk associated with soil contaminants was assessed by determining the ILCR for carcinogenic effects and the hazard quotient (HQ) for non-carcinogenic effects by calculating the LADD. The equations described by the United States Environmental Protection Agency (USEPA) were used in the calculations (USEPA, 1989(USEPA, , 2002(USEPA, , 2009. In equation (1), LADDing is the average daily lifetime intake by ingestion in mg/kg/day, C is the concentration of the contaminant in the soil in mg/kg, IngR is the soil ingestion rate in mg/day, EF is the frequency of exposure in day/year, ED is the duration of exposure in years, ET is the exposure time in hours/day, CF is the conversion factor in kg/mg, BW is the average body weight in kg, AT is the average time in hours. LADDinh=(C×InhR×EF×ED×ET×AFinh)/(PEF×AT) (2) In equation (2), LADDinh is the lifetime average daily inhalation dose in mg/kg/day, C is the concentration of the contaminant in soil in mg/kg, InhR is the soil inhalation rate in m 3 /day, AFinh is the absorption factor for the lungs, PEF is the particulate emission factor in m 3 /kg.
In equation (3), LADDderm is the lifetime average daily dose by ingestion in mg/kg/day, SA is the exposed skin surface area in cm 2 , AF is the dermal soil adhesion factor in mg/cm 2 , ABS is the dermal absorption factor (specific to each contaminant), GIABS is the fraction of the contaminant absorbed from the gastro-intestinal tract (specific to each contaminant).
The exposure parameters used for the assessment of carcinogenic health risks and those specific to individual pesticides are listed in Tables 1 and 2.  Results and Discussion:-Physicochemical and particle size characteristics of soil samples: The physicochemical characteristics of the soil samples are listed in Table 3. The carbon and organic matter contents vary respectively from 0.483% to 1.59% and from 0.831% to 2.735% with averages of 0.92±0.29% and 1.59±0.51%. It should be noted that there is a significant difference (p < 0.05) between the averages of the carbon and organic matter rates of the different samples.The Newman-Keuls test, used to compare averages, showed a significant difference between the averages of carbon and organic matter levels at the different sites.
The organic nitrogen contents are between 0.05% and 0.137% with an average value of 0.08±0.02%. There is a significant difference (p < 0.05) between the average nitrogen content of the different samples.The Newman-Keuls test used revealed a significant difference in total nitrogen between Dabakala and Niakara. Particle size analysis of the samples identified 5 (five) fractions, specifically clay, fine silt, coarse silt, fine sand and coarse sand. The percentages of clay, silt and sand in the soil samples vary respectively from 3.25% to 15.5% with an average of 8.1±3.55%, from 10.29% to 56.95% with an average of 24.51±12.24% and from 36.05% to 84.96% with an average of 65.80±14.45%. Based on the USDA textural classification, the results obtained show that the soils are mainly silty-sand and sandy-silt textured. Regardless of the fraction considered, there is no significant difference between the percentages of the grain size fractions in the samples.  letters (a, b) are not significantly different (p >0.05) while using ANOVA and test of Newman-Keuls

Concentrations of organochlorine pesticide residues in soil and crop samples:
The analysis of soil samples showed the presence of five (5) organochlorine pesticides namely lindane, DDT, (α andβ)-endosulfan and its metabolite sulfate-endosulfan. They were detected at a frequency of 80% in all samples analysed ( Table 4).The analysis of variance applied to the results showed that there was no significant difference (p>0.05) between the different means of pesticide concentration detected in soil samples at the different sites (Table  5). Following the analysis of crop samples, no pesticide residues were detected in yam, cassava and groundnut under the same analytical conditions ( Table 6). The concentration of organochlorines in the roots depends largely on the concentration in the soil (Mikes et al., 2009). The more polluted the soil is, the more likely root and tuber crops will be contaminated. It also depends on the type of soil on which roots and tubers are grown. Pesticides are easily adsorbed on soils rich in organic matter or clay, which makes them poorly available to plants (Calvet et al., 2005;Woignier et al., 2015). According to (Hassine et al., 2008), soils with organic matter contents below 5% are not very rich. With organic matter contents obtained in our study, we could conclude that soils are poor in organic matter. Thus this poverty would justify a low retention of pesticides, resulting in low soil pollution and consequently less contaminated plants.
Furthermore, the sensitivity of the analytical technique for the detection of compounds and the extraction method could explain why no pesticide residues were detected in the samples. Pesticide concentrations in food crops would therefore be below the detection limits in the method used or the extraction method used is not adequate. The choice of extraction method depends on the physicochemical properties of the compounds of interest and the sample matrix 417 (Durovic et Dorevic, 2011). Selective extraction improves sensitivity levels of analyte detection (Fontanals et al., 2007).    Table 7 presents the LADD, ILCR and HQ values calculated for the different pathways of farmer exposure to DDT and lindane in soil for the different zones. The total cancer risk value (ƩILCR) related to lindane exposure is higher than that of DDT in Dabakala and Niakara, and these values are roughly equal. Regarding the hazard quotient that defines the risk of non-cancer adverse effects, it is also higher for lindane in both areas. For each pesticide (DDT and lindane), the cancer risk is found to decrease as follows: ILCR ingestion > ILCR dermal > ILCR inhalation. ILCR values (ILCR ingestion, ILCR dermal, ILCR inhalation and ∑ILCR) are all below 10 -6 . According to the ATSDR, cancer risk can be classified into different ranges: very low risk value≤10 -6 , low risk 10 -6 ≤value≤10 -4 , moderate risk 10 -4 ≤value≤10 -3 , high risk 10 -3 ≤value≤10 -1 , very high risk value≥10 -1 (ATSDR, 1995). Regarding the risk of non-cancer adverse effects, HQ <1 which would mean that DDT and lindane in soil would not cause noncancer adverse effects to farmers (Yahaya, 2017).
The risks related to farmer exposure to DDT and lindane from soil via ingestion, inhalation and dermal route is negligible.

Conclusion:-
The objective of this study was to assessment the concentration of organochlorine pesticides residues in soil and crops samples from cotton growing area and the health risk related the soil contamination. Five pesticides (lindane, DDT, α and β-endosulfan and sulfate-endosulfan) were detected with a frequency of 80% in all soil samples analysed, but not in crops samples. The concentrations found in soil samples were under United States and FAO maximum residues limits for agricultural soils. The cancer risk assessment and hazard quotient values are respectively below 10 -6 and 1. The risks related to farmer exposure to DDT and lindane from soil via ingestion, inhalation and dermal route is negligible.