Different pollution evaluation indices, including the enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CFi), degree of contamination (Cd), pollution load index (PLI), and, potential ecological risk evaluation index (PERI) were used in this study to assess the degree of pollution, details presented in Table 2 and pollution/risk evaluation category are given in Table S2.

Pollution evaluation indices.

Table 1
Evaluation indicesEquationExplanationReference
Enrichment factor (EF)EF=(CxMFe)sample(CxMFe)background (1)(Cx/ MFe) sample = the ratio of the concentration of toxic metals (Cx) to that of iron (MFe) in the soil sample(CM/CFe) background = the same reference ratio in the pre-industrial sampleChakraborty et al. [42] (link), Islam et al. [7] (link), Sutherland [43]
Geo-accumulation index (Igeo)Igeo=Log2Cxi1.5×Bxi (2)Cxi = the studied toxic metal concentration of the ith parameterBxi = the geochemical background value of the toxic metal of the ith parameter in the preindustrial soil samples of the study areaMuller [44] , Islam et al. [45] (link)
Contamination factor (CFi)CFi=CxiBxi (3)Hakanson [46] (link)
Degree of contamination (Cd)Cd=∑i=1nCFi (4)Cd = the degree of contaminationHakanson [46] (link)
The pollution load index (PLI)PLI=CFi1×CFi2×CFi3…………×CFinn(5)n = number of studied metalsTomlinson et al. [47] (link)
Potential ecological risk evaluation index (PERI)Eri=Tri×CFi,PERI=∑i=1nEri (6)Eri = the particular metal-induced ecological risk index of the ith parameterTri = the biological toxic factor of the ith parameterThe study used the Tri value of As, Ni, Pb, Cd, Cr, and Cu as 10, 6, 5, 30, 2, and 5, respectivelyHakanson [46] (link)

Human health risks assessment methods via ingestion, dermal contact and inhalation exposure routes.

Table 2
Assessment approachesEquation
Chronic daily intake (CDI) (mg/kg/day)CDIingest=CS×IRS×EF×EDBW×AT×CF(7)CDIdermal=CS×SA×AF×ABS×EF×EDBW×AT×CF(8)CDIinhale=CS×InhR×EF×EDPEF×BW×AT (9)
Hazard quotient (HQ)HQingest=CDIingestRfD (10)HQdermal=CDIdermalRfD(11)HQinhale=CDIinhaleRfD(12)
Hazard index (HI)HI=∑HQ=HQingest+HQdermal+HQinhale(13)
Carcinogenic risk (CR)CRingest=CDIingest×CSFi (14)CRdermal=CDIdermal×CSFi (15)CRinhale=CDIinhale×CSFi (16)Lifetime cancer risk=CRingest+CRdermal+CRinhale (17)
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