Un-segregated waste disposal: an alarming threat of antimicrobials in surface and ground water sources in Delhi. 
Exposure of active pharmaceutical compounds (APCs) to the environment during human use is of potential importance in the emergence of drug resistance, changing soil microbiota and their residual effect on living organisms.  Thus, this study aimed to assess the extent of exposure of APCs in the hydrologic cycle in and around New Delhi.  This study analyzed the presence of 28 drugs from different classes in the surface water (river Yamuna) and aquifers collected from 48 places in Delhi (within the radius of 40 km).  The collected water samples were quantified for APCs content using LC-MS/MS.  This study revealed that aquifers are extensively affected in most areas based on the accumulation of APCs in water resources to the levels > 0.01 μg/L. Interestingly, a geographical plot of total APCs studied indicated clustering in aquifers with such high levels closer to an unscientific landfill.  This 30-year-old un-segregated landfill is found to drain leachate into surface water that had high APCs.  This study further revealed that apart from therapeutic usage, the main source of ecological exposure could be due to the disposal of unused and expired pharmaceutical compounds into landfills.  For the first time, this study revealed the existence of antimicrobial agents and other APCs in the aquifers of Delhi with levels > 0.1 μg/L, which is a matter of serious concern in terms of multi-drug resistance and other environmental perils.  This study warrants the enforcement of regulations for the disposal of unused/expired APCs in high-density population areas.