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The correlations between different districts were as follows: sig = 0.14 between districts 1 and 2, sig = 0.89 between 1 and 3, sig = 0.001 between 1 and 4, 5, and 6, confirming that surface water organic matter is the primary driver of HAA concentrations. The water treatment plants are located in districts 1, 2, and 3. In these districts, most of the required water is supplied from surface water with storage reservoirs used when necessary. The estimation of the carcinogenic and non-carcinogenic health risk assessment of HAAs via consumption of tap water is shown in Table 3. The mean concentrations of DCAA in six districts and in spring, summer and fall seasons were measured as 22.01, 14.95, and 23.65 μg L−1, respectively. Also, the mean concentrations of TCAA in spring, summer, and fall seasons were determined as 10.31, 9.98, and 12.99 μg L−1, respectively. Based on the mean concentrations of DCAA and TCAA, the EDI, RfD, HQ, and ELCR were estimated (the calculation has been explained in the section ‘Daily intake and health risk assessment’). For the non-carcinogenic risk assessment, the HQ of DCAA and TCAA in the target groups was calculated to be less than 1, which indicates that it is unlikely even for sensitive populations to experience adverse health effects. The HQ values for DCAA in infants, children, teenagers, and adults in spring were 0.523, 0.275, 0.220, and 0.165, respectively. The HQ values for TCAA in infants, children, teenagers, and adults in spring were 0.049, 0.026, 0.021, and 0.015, respectively. The HQ values for DCAA were found to be more than TCAA in all of the target groups and also it was found that the HQ in fall seasons was higher than in other seasons.

Table 3

Estimation of carcinogenic and non-carcinogenic health risk assessment of HAAs in the water supply of Tehran

 HAAs
DCAA
TCAA
SpringSummerFallSpringSummerFall
Detected mean concentration [μg/L] 22.01 14.95 23.65 10.31 9.98 12.99 
EDIa 
 Infant (<2 yr) 2.091 1.420 2.247 0.979 0.948 1.234 
 Children (2–6 yr) 1.101 0.748 1.183 0.516 0.499 0.650 
 Teenagers (6–12 yr) 0.880 0.598 0.946 0.412 0.399 0.520 
 Adults (≥16 yr) 0.660 0.449 0.710 0.309 0.299 0.390 
RfDb 4 4 4 20 20 20 
HQc 
 Infant (<2 yr) 0.523 0.355 0.562 0.049 0.047 0.062 
 Children (2–6 yr) 0.275 0.187 0.296 0.026 0.025 0.032 
 Teenagers (6–12 yr) 0.220 0.150 0.237 0.021 0.020 0.026 
 Adults (≥16 yr) 0.165 0.112 0.177 0.015 0.015 0.019 
Drinking water unit riskd 1.4 × 106 1.4 × 106 1.4 × 106 2 × 106 2 × 106 2 × 106 
ELCRe 3.08 × 105 2.09 × 105 3.31 × 105 2 × 105 2 × 105 2 × 105 
 HAAs
DCAA
TCAA
SpringSummerFallSpringSummerFall
Detected mean concentration [μg/L] 22.01 14.95 23.65 10.31 9.98 12.99 
EDIa 
 Infant (<2 yr) 2.091 1.420 2.247 0.979 0.948 1.234 
 Children (2–6 yr) 1.101 0.748 1.183 0.516 0.499 0.650 
 Teenagers (6–12 yr) 0.880 0.598 0.946 0.412 0.399 0.520 
 Adults (≥16 yr) 0.660 0.449 0.710 0.309 0.299 0.390 
RfDb 4 4 4 20 20 20 
HQc 
 Infant (<2 yr) 0.523 0.355 0.562 0.049 0.047 0.062 
 Children (2–6 yr) 0.275 0.187 0.296 0.026 0.025 0.032 
 Teenagers (6–12 yr) 0.220 0.150 0.237 0.021 0.020 0.026 
 Adults (≥16 yr) 0.165 0.112 0.177 0.015 0.015 0.019 
Drinking water unit riskd 1.4 × 106 1.4 × 106 1.4 × 106 2 × 106 2 × 106 2 × 106 
ELCRe 3.08 × 105 2.09 × 105 3.31 × 105 2 × 105 2 × 105 2 × 105 

aEstimated daily intake via drinking water (EDI: μg/kg bodyweight/day).

bIRIS RfD chronic non-carcinogenic effect risk (RfD, μg/kg bw/day). The TCAA oral RfD is 0.02 mg (kg-day)−1 and oral RfD of 0.0004 mg (kg-day)−1 for DCAA.

cHazard quotient (HQ): ratio of EDI to RfD.

dDrinking water unit risk (μg L−1) (EPA, IRIS).

eExcess lifetime cancer risk (ELCR).

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