First insight into the occurrence, spatial distribution, sources, and risks assessment of antibiotics in groundwater from major urban-rural settings of Pakistan.

Antibiotics contamination in the water environment is a high priority global concern. Growing levels of antibiotics in freshwater resources, especially groundwater, due to anthropogenic sources such as pharmaceutical and veterinary applications, are alarming. The present study aims to investigate the occurrence, spatial distribution, source apportionment, ecological, and human health risks of antibiotics (n = 23) in groundwater samples (n = 144) of highly populated cities of Pakistan. The elevated level of antibiotics was detected in Faisalabad with the mean concentrations of 13.8 ng/L, followed by Gujrat (7.8 ng/L), Lahore (4.04 ng/L), Quetta 3.9 ng/L, Rawalpindi/Islamabad (2.29 ng/L), and Peshawar (2.03 ng/L), respectively. Out of 23 investigated antibiotics, tigecycline and ciprofloxacin were predominantly present in groundwater with average concentrations of 21.3 ng/L and 18.2 ng/L, respectively. The spatial distribution analyses revealed that among the targeted cities, Faisalabad, an industrial hub of the country, had the most polluted groundwater with dominant classes of antibiotics including quinolones (except flumequine), ß-Lactams, tetracyclines, sulfonamides, and amphenicols, implying an elevated consumption of human and veterinary drugs in the city. The occurrence of targeted antibiotics varied greatly among cities (p < 0.05). PCA-MLR analysis confirmed domestic discharge (31%), animal husbandry (19%), and pharmaceutical/hospital discharge (48%) as the chief contributors to antibiotics contamination in groundwater of Faisalabad. The risk quotient (RQ) values of targeted antibiotics were reported as 1.16E-07 to 1.03E-02, and demonstrated that antibiotics pose no risks to human health, while hazard quotient (HQ) values were observed as 09.5E-05 to 6.6E-01, and only ciprofloxacin, flumequine, oxytetracycline, and sulfamethoxazole revealed moderate to low ecological risks to water species (0.1 < HQ < 1). Since, no detailed study has been conducted to evaluate the antibiotics' contamination in groundwater of Pakistan, this robust investigation provides a way forward to further explore the environmental and human health implications of antibiotics in major urban-rural settings in the region.