In the above equations, CDI is the chronic daily intake (mg/kg·day), HQ is the health risk index,
Cw is the pollutant concentration (mg/L), IR is the drinking water consumption per capita (L/day), EF is the exposure frequency (days/year), ED is the exposure duration (year), BW is the body weight (kg/person), and AT (days) is the average time. The calculation of AT for carcinogenic risk is as follows: 70 × AT = 365 and for non-carcinogenic risk as follows: AT = 365 × ED (Mesdaghinia
et al. 2016; Nikbakht
et al. 2017). The values of the cancer slope factor (CSF), reference dose (RfD), and other assumptions due to exposure to heavy metals through drinking water are shown in Table 1. The hazard index (HI) is obtained from the sum of HQ related to the seven studied metals. Equation (
4) was used to calculate carcinogenic risk:
Table 1CSF values, RfD, and other assumptions for exposure to heavy metals through drinking water (Tirkey et al. 2017; Mohammadi et al. 2019; Radfarda et al. 2019; Lorestani et al. 2020; Maleki & Jari 2021)
| Exposure factors
. | Unit
. | Values
. |
|---|
| Adults
. | Teenager
. | Children
. |
|---|
| ED | years | 40 | 13 | 4 |
| EF | days/year | 365 | 365 | 365 |
| IR | L/day | 2.5 | 2 | 0.78 |
| AT for carcinogens | years | 25,550 | 25,550 | 25,550 |
| AT for non-carcinogens | days | 14,600 | 4,745 | 1,460 |
| BW | kg | 80 | 50 | 15 |
| RfD | mg/kg/day | Fe = 0.7, Cu = 0.04, Mn = 0.024, Zn = 0.3, Cr = 0.003, Pb = 0.0035, As = 0.0003 |
| CSF | mg/kg/day | Cr = 0.19, As = 1.5 |
| Exposure factors
. | Unit
. | Values
. |
|---|
| Adults
. | Teenager
. | Children
. |
|---|
| ED | years | 40 | 13 | 4 |
| EF | days/year | 365 | 365 | 365 |
| IR | L/day | 2.5 | 2 | 0.78 |
| AT for carcinogens | years | 25,550 | 25,550 | 25,550 |
| AT for non-carcinogens | days | 14,600 | 4,745 | 1,460 |
| BW | kg | 80 | 50 | 15 |
| RfD | mg/kg/day | Fe = 0.7, Cu = 0.04, Mn = 0.024, Zn = 0.3, Cr = 0.003, Pb = 0.0035, As = 0.0003 |
| CSF | mg/kg/day | Cr = 0.19, As = 1.5 |
(4)