Recent advances in laboratory analytical techniques now allow scientists to detect organic compounds at very low concentrations, in the parts-per-billion to parts-per-trillion range. As detection limits have dropped and as scientists have begun to test for more and more chemicals, previously undetected organic chemicals are increasingly being found in streams, lakes and groundwater. These previously undetected chemicals, typically synthetic chemicals released from human activities on the land surface, are now popularly referred to as “emcons” or “emerging contaminants.”