The two principal toxicity risk factors evaluated are the
SF for carcinogen risk characterization and the reference dose (
RfD) for non-carcinogen risk characterization (Li
et al. 2013; Bamuwuwamye
et al. 2017). The estimations of the magnitude, frequency, and duration of human exposure to each potentially toxic metal in the environment are reported as an
ADD and it is calculated using the following equation:
Here,
ADDi (mg/kg/day) is the average daily dose through ingestion of water,
Ci is the concentration of the metal (mg/L),
IR is the ingestion rate,
EF represents exposure frequency,
ED is exposure duration,
BW indicates body weight,
AT is the average time for non-carcinogens,
ET represents exposure time, and
CF is the conversion factor (Wongsasuluk
et al. 2016). Values of all the above parameters are presented in Table 2.
Table 2Standard values for calculating exposure assessment of trace metals in waters (USEPA 1989; Demir et al. 2015)
| Index
. | Name
. | Value
. | Unit
. |
|---|
| Ci | Concentration of metal in water | – | mg/L |
| IR | Water ingestion rate | 2 | L/day |
| Ef | Exposure frequency | 365 | Days/year |
| Ed | Exposure duration | 70 | Years |
| Bwt | Average body weight | 70 | kg |
| At | Averaging time | 25,550 | Days |
| Cf | Unit conversion factor | 1 × 10−3 | L/cm3 |
| RfDi | Cd = 0.0005; Cr = 1.5; Cu = 0.037; Ni = 0.020; Pb = 0.036; Zn = 0.3; Mn = 0.14; Fe = 0.7 | | |
| Index
. | Name
. | Value
. | Unit
. |
|---|
| Ci | Concentration of metal in water | – | mg/L |
| IR | Water ingestion rate | 2 | L/day |
| Ef | Exposure frequency | 365 | Days/year |
| Ed | Exposure duration | 70 | Years |
| Bwt | Average body weight | 70 | kg |
| At | Averaging time | 25,550 | Days |
| Cf | Unit conversion factor | 1 × 10−3 | L/cm3 |
| RfDi | Cd = 0.0005; Cr = 1.5; Cu = 0.037; Ni = 0.020; Pb = 0.036; Zn = 0.3; Mn = 0.14; Fe = 0.7 | | |
Here, ADDi (mg/kg/day) is the average daily dose through ingestion of water, Ci is the concentration of the metal (mg/L), IR is the ingestion rate, EF represents exposure frequency, ED is exposure duration, BW indicates body weight, AT is the average time for non-carcinogens, ET represents exposure time, and CF is the conversion factor (Wongsasuluk et al. 2016). Values of all the above parameters are presented in Table 2.