Risk Assessment of Organochlorine Residues in Agricultural Crops Cultivated [2020] on/around Abandoned Tin Mine Areas in Jos South LGA, Plateau State, Nigeria

Abstract

Aims: To investigate the levels and the associated risks of 18 organochlorine residues in water, soil, sediment, and five vegetables cultivated on abandoned mine areas. Study Design:  Water, sediment, soil (at 0 -10cm, 11 – 20cn, 21 – 30cn) and vegetables samples were collected from the abandoned tin mine agricultural areas.  These subsamples were separately combined and mixed so that a portion taken of the composite was representative of each subsample. The representative fractions were then treated for analysis Place and Duration of Study: Samples were collected between February and May 2020 from the cultivated abandoned mine areas in Du, Jos - South Local Government Area, Plateau State, Nigeria, Methodology Liquid–liquid extractions methods were used for the extraction of pesticide residues from water, sediment, soil and vegetables. The organochlorine residues were determined by GC/MS. Results: The physico- chemical properties data obtained for the soils/sediment from abandoned mine sites in Jos South were very heterogeneous, hence, various behaviors of pesticide residues in different soil/sediment matrices. There were no significant differences (P= 0.05) in mean minerals among the various samples. The pesticides residues detected in water were b-endosulfan, p,p-DDD and methoxychlor. The residues recorded in water were above the WHO’s MRL and Federal Food, Drug and Cosmetic Act (FFDCA,) for drinking water.  Residues were also detected in sediment and soils samples. The 11 – 20cm subsoil accumulated the highest levels of the pesticide analyzed. The order of the accumulation of the OCP were; y-BHC>DDD>endrin>endrin ketone>a-endosulfan>b-endosulfan and of the sample type was water<surface soil<21-30cm subsoil<sediment<11-20cm subsoil. The results also showed the presence of OCPs in potato, tomato, cabbage, green beans, and green peppers. y-BHC  in potato, tomato and green pepper, endrin in tomato, endrin ketone in potato, tomato and green beans and d-BHC in cabbage had EDI higher levels than ADI and so their HQ greater than 1. The health risks indices (HRI) less than 1 in all other OCP residues were obtained for adults and children that would consume the vegetables except for y-BHC and endrin ketone in potato and tomato, d-BHC in cabbage, d- BHC in green pepper and green beans where the HRI is above 1 that poses health risk. There is however no significant difference (P=0.05) among vegetable types.  Positive correlation values ( 0.72, 0.83, 0.71, and 0.56) were  observed between endrin and lindane, endrin and heptachlor, endrin and DDT respectively. Conclusion: The consumption of vegetables that contained y-BHC, d-BHC, endrin and endrin ketone whose EDI and HQ were greater than 1 could pose non-carcinogenic health risks. Adults are likely to have less health risk from consuming these vegetables. The effective monitoring of pesticide residues in food items is required. There is also need to sensitize and educate the general public especially the end-users (farmers) on management practices of pesticides.