Determination Of The Concentrations,Potential Sources And Health Risks Of Heavy Metals In Selected Medicinal Plants From Awash River Basin,Ethiopia

Traditional medicinal plants have been used in all over the world since ancient time.However,currently,environmental pollution particularly heavy metals cause serious problems on the quality and safety of medicinal plants.In Ethiopia,more than 80%of the population relies on traditional medicinal plants.Even though traditional medicinal plants are highly used,there is a shortage of research done on heavy metal concentration on traditional plants in the country.Thus,this study was aimed to determine the concentration,potential sources and evaluate the risks of heavy metals in selected medicinal plants from the Awash River Basin,Ethiopia.The recorded mean concentration of heavy metals in the plants were 1.934,0.023,0.023,0.045,0.129,ND,0.025,ND and 0.009 mg/kg in Xanthium strumarium L.(Asteraceae),0.834,0.036,0.024,0.021,0.090,ND 0.002,0.001 and 0.016 mg/kg in Ficus exasperata Vahl(Moraceae),1.603,0.018,0.019,0.025,0.133,0.005,0.006,0.002 and 0.012 mg/kg in Persicaria attenuata(R.Br)Sojak(Polygonaceae)and 0.557,0.010,0.010,0.024,0.098,ND,0.012,0.020 and 0.004 mg/kg in Kanahia laniflora(Forssk.)R.Br.(Asclepiadaceae)for Al,Cr,Ni,Cu,Zn,As,Cd,Hg and Pb,respectively.One sample t-test was applied to determine the statistical difference of heavy metal concentrations within and between plant species at a=0.05 significant level.The obtained result indicated that Al,Cr,Ni,Cu,Zn and Pb showed a significant difference,whereas As,Cd and Hg did not indicate a significant difference between plants species at ?=0.05.Pearson,s correlation analysis indicated that there was a strong positive correlation between Al-Ni(r=0.927**)and Zn-Cu(r=0.764**)at a=0.01 significant level.Principal Component Analysis(PCA)point out that the sources of heavy metals in the plants were associated with anthropogenic factors.The sampling adequacy and Sphericity was evaluated using Kaiser-Meyer-Olkin(KMO)and Bartlett's test.The mean concentrations of all elements except Cd in Xanthium strumarium L.(Asteraceae)and Pb in Ficus exasperata Vahl(Moraceae)were below the permissible limit of FAO/WHO(2001/2005).The health risks of heavy metals in the plants were evaluated using estimated daily intake(DIM),target hazard quotient(THQ),health risk index(HI)and cancer risk(CR).The result showed that the estimated daily intake for all elements except Al in Xanthium strumarium L.and Persicaria attenuata R.Br.Sojak were below the oral reference dose of elements established by USEPA for both adult and children.Target hazard quotient(THQ)of all elements except Al in all plant species were within the permissible limit for both adult and children.Hazard index(HI)for all plants were greater than(>1)which indicates that there could be the potential non-cancer risk from consuming these plants.However,the obtained result for cancer risk indicated,all values were within an acceptable range of carcinogenic risk.This implies consumptions of these plants are safe with respect to cancer risks,while unsafe in response to non-cancer risk.