## 3 Results and Discussion
### Health Risk Assessment of OCPs in Water Samples  
Underground water i.e., pressure pumped and hand pumped water is mostly used for drinking purposes in the Charsadda district. A health risk assessment model [42] was used to calculate health risks from underground drinking water for adults and children. Some OCPs were present and some were not detected in the underground water samples of Charsadda district. The health risk levels caused due to OCPs were calculated for the maximum values of contaminants present in the underground drinking water for adults and children.  
Table 1 showed the summary statistics for the health risks that may be associated with OCP contaminants present in the water samples of the Charsadda district. For adults, the cancer risk from surface water ranged from 0 to 0.96 \(\times\) 10\({}^{-6}\) for \(\gamma\)-BHC, 0 to 15.53 \(\times\) 10\({}^{-6}\) for heptachlor and 0 to 7.61 \(\times\) 10\({}^{-6}\) for allorin. The cancer risk for surface water from 4,4\({}^{\prime}\)-DDE and dieldrin ranged from 0 to 0.16 \(\times\) 10\({}^{-6}\) and 0 to 8.69 \(\times\) 10\({}^{-6}\), respectively.  
Similarly, for children, the cancer risk from surface water due to \(\gamma\)-BHC, heptachlor and allorin ranged from 0 to 2.05 \(\times\) 10\({}^{-6}\), 0 to 33.29 \(\times\) 10\({}^{-6}\) and 0 to 16.30 \(\times\) 10\({}^{-6}\), respectively.  
However, the cancer risk from surface water ranged from 0 to 0.47 \(\times\) 10\({}^{-6}\) for 4,4\({}^{\prime}\)-DDE and 0 to 14.25 \(\times\) 10\({}^{-6}\) for dieldrin. In most of the water samples, the cancer risk from heptachlor, allorin and dieldrin for adults and children was negligible, however, in a few samples it was higher than the acceptable risk level (1 \(\times\) 10\({}^{-6}\)) recommended for carcinogens by the US EPA. The concentrations of these OCPs in the water samples indicates that, in most of the Charsadda district, the water may not pose any serious cancer risk to the local population, especially to children, and that the majority of the water samples in the area were suitable for drinking. However, it is essential to prevent new input sources of these OCPs in the surface and underground water to ensure safe drinking water.  
Cancer risk due to each pollutant in the water samples from Charsadda district was in the order of heptachlor \(>\) allorin \(>\) dieldrin. In all the water samples from Charsadda district, the cancer risk from \(\alpha\)-BHC, \(\beta\)-BHC, endosulfan I, 4,4-DDE, endrin, 4,4\({}^{\prime}\)-DDT, endrin aldehyde, endrin ketone, \(\gamma\)-chlordane, \(\alpha\)-chlordane, 4,4\({}^{\prime}\)-DDE, endosulfan sulfate and methoxychlor was either not detected, or lower than the acceptable risk level (1 \(\times\) 10\({}^{-6}\)) recommended for carcinogens by US EPA.  
The hazard quotients were also estimated according to the assessment model for individuals based on the maximum contamination value of OCPs in water samples from Charsadda district. When the ratio of HQ increases above 1, then it may have adverse effects on human health [45]. The non-carcinogenic risks from heptachlor, aldrin and dieldrin in the water samples from Charsadda district for children was somewhat higher than 1, which is the value recommended by US EPA, 1986. The non-carcinogenic risk from each pollutant in the water samples of the Charsadda district was in the order of heptachlor > aldrin > dieldrin > \(\gamma\)-BHC. Non-carcinogenic risk from \(\alpha\)-BHC, \(\beta\)-BHC, endosulfan I, 4, 4-DDE, endrin, 4, 4'-DDT, endrin aldehyde, endrin ketone, \(\gamma\)-chlordane, \(\alpha\)-chlordane, 4,4'-DDE, endosulfan sulfate and methoxychlor was not found in water samples from Charsadda district.