1. The study found high methane concentrations in drinking water wells located within 1 km of active shale gas wells, which had a thermogenic isotopic fingerprint matching the Marcellus gas. Wells further than 1 km had lower methane concentrations and different isotopic compositions. 2. No evidence was found of chemical contamination of drinking water from shale gas operations. However, some data showed possible hydraulic connectivity between deep Marcellus formations and shallow aquifers in Pennsylvania. 3. Disposal of produced water into surface water poses significant risks of salinization, accumulation of toxins like barium and radionuclides, with impacts extending hundreds of meters downstream. Sustainable shale gas development needs to address environmental issues from