Monitoring Strategies for Chemicals of Emerging Concern (CECs) in California’s Aquatic Ecosystems

Although thousands of substances can now be detected in the environment, a small percentage of known chemicals – approximately 200 — are currently regulated and/or routinely monitored in California receiving waters.  The much larger group of chemicals that remain largely unregulated and/or unmonitored in the aquatic environment, known as chemicals of emerging concern (CECs), may originate from a wide range of point and non-point sources. Upon discharge to receiving waters, CECs that are readily soluble in water will remain in the dissolved (aqueous) phase and provide a route of exposure to aquatic life. A smaller subset of CECs that are hydrophobic will associate with particles, where they may remain suspended in the water column or accumulate in sediments and ultimately in tissues of aquatic and terrestrial biota. The larger concern is that exposure to aqueous, sediment and tissue CECs may affect wildlife and humans.

In response, the California Water Resources Control Board (State Water Board) in conjunction with the David and Lucile Packard Foundation and a group of stakeholder advisors tasked a group of leading scientists to address the issues associated with CECs in the State’s aquatic systems that receive discharge of treated municipal wastewater effluent and stormwater. The group was charged to identify potential sources and evaluate the fate and effects of CECs, and ultimately to provide guidance for developing monitoring programs that assess those chemicals with the highest potential to cause effects in the State’s receiving waters.

Seven experts in chemistry, biochemistry, toxicology, chemical and risk assessment, engineering and coastal and marine environmental health science were convened as the CEC Ecosystems Panel (“Panel”) in October 2009. The Panel held six in?person meetings to formulate their approach and recommendations, while soliciting input from stakeholders and the public. This report provides the results from the Panel’s deliberations, including four products intended to assist the State in developing a monitoring process for CECs based on sound, up-to-date scientific principles.