The recent dramatic rise in the use of hydraulic fracturing for natural gas raises concerns that chemicals used in this process may contaminate surface and ground water. As demand increases for alternative energy sources, well proliferation has increased and is moving into locations within crucial water basins that supply fresh water for millions. Hydraulic fracturing involves injecting millions of gallons of water and hundreds of chemicals into the ground under high pressure. A portion will return to the surface, and is typically disposed of by injecting it back into the ground, spreading it over large areas, or storing it in large evaporation pits that may not adequately contain it. In 2005, the process of hydraulic fracturing was added as an exemption to the Safe Drinking Water Act, reducing the ability to regulate and study the impacts of this process on the environment. At the same time, there has been an increase of areas reporting contamination of local water supplies.Preliminary research has shown that dozens of the chemicals used in this process have endocrine disrupting activity, creating the potential for widespread contamination of water supplies with mixtures of these chemicals. The goal of this preliminary study is to compare the hormonal activity in surface and ground water as well as sediment samples collected in drilling-dense region and drilling-sparse areas of Colorado. Water will be tested for estrogen, androgen, thyroid, and progesterone receptor agonist and antagonist activity using MCF-7 and HepG-2 cell lines that have been transfected with hormone responsive reporter genes. A baseline of hormonal activity will be established from samples taken from drilling-sparse areas. Once we have that in place, we can more accurately determine if samples taken from drilling-dense areas show altered hormonal activity. Samples of surface and ground water will also be taken periodically from sites with new well production. This will provide a timeline to ascertain whether or not the water composition changes substantially throughout the entire drilling process.The implications of this are important as drilling extends into areas where potential drinking water contamination could be an even larger problem. The Marcellus Shale is one such area, covering a large portion of many northeastern states. This area is of high concern, as it includes the Delaware River Basin, supplying water to the entire greater New York City area. It has been suggested that citizens living near drilling of this type have experienced significant changes to their surface and drinking water. However, as there is currently no legislation controlling this process, there has been little to no scientific research done in this area. This study looks to gain preliminary information on the subject to better direct future research in this area. (poster)