The U.S. Geological Survey investigated the presence of pharmaceuticals, health-care products, and other organic-wastewater compounds-often referred to as "emerging contaminants"-entering Tinkers Creek, the largest tributary to the Cuyahoga River, which is the second largest tributary to Lake Erie in Ohio. The Tinkers Creek study evaluated the potential for these compounds to enter from obvious sources; specifically wastewater-treatment plants.

Tinkers Creek was chosen as a study site after biological surveys by the Ohio Environmental Protection Agency indicated that the numbers of fish in the population did not match the available habitat. When fish are not abundant enough to use the habitat available, it is normally a sign of impaired chemical quality of the water. However, chemical surveys done in conjunction with the biological surveys did not identify the usual chemical suspects. The Ohio Environmental Protection Agency then asked the USGS for help investigating whether emerging contaminants were having an effect on the fish population.

Polar organic chemical integrative sampler (POCIS) devices were used to mimic the exposure to chemicals aquatic organisms, such as fish, would experience while living in the stream. A POCIS device can accumulate trace to ultratrace concentrations of chemicals over a long-term exposure. The POCIS approach is proving to be more effective for these kinds of studies than traditional monitoring methods such as grab sampling.

In the Tinkers Creek study, the POCIS devices were set at 18 sites, including positions above and below the seven wastewater-treatment plants discharging to Tinkers Creek and its tributaries. Two streams without wastewater-treatment plants were selected as reference stations. Each reference stream is a tributary of the Cuyahoga River and in a more remote area than Tinkers Creek. The period of sampling lasted 28 days and began May 8, 2006. Analyses of the data are ongoing.