Background

Constituents of Emerging Concern (CECs) encompass any physical, chemical, biological, or radiological substance or matter in any environmental media that may pose a risk to human and/or ecological health, for which there is not currently published enforceable California or federal environmental or health standard, or the existing standard is evolving or being re-evaluated, and/or the presence, frequency of occurrence, source, fate and transport, and/or toxicology of which is not well understood, routinely monitored, and/or may lack analytical methods. CECs include a wide variety of constituents including per- and polyfluoroalkyl substances (PFAS), pharmaceuticals, personal care products (PCPs), flame retardants, disinfection by-products, certain urban pesticides, microplastics and nanomaterials, and numerous biological agents. CECs are increasingly being detected at low levels in surface water, and there is concern that these certain constituents have an impact on aquatic life (USEPA, 2021).

CECs may originate from a wide range of point and non-point sources and may be found in groundwater, surface water, drinking water, soil, sediment, dust, air, food, and biota. Once released to the environment, there is often limited information regarding the transport and fate of CECs in the environment. Due to the environmental persistence of some CECs, failure to respond to CECs in a timely manner may result in long-lasting impacts to California’s water resources and require extensive costs to mitigate damages such as those posed by exposures that affect wildlife and human health.

California’s environmental authority is unified under the California Environmental Protection Agency (CalEPA). The State Water Resources Control Board (State Water Board) is one of six agencies that are tasked with various environmental oversight, and each agency has a role about managing CECs in California. The State Water Board implements CEC monitoring and management strategies for permitted discharges and receiving waters. Several regional water quality control boards (Regional Water Boards) have monitored and continue to monitor for CECs in wastewater effluent, storm water runoff, and ambient water through pilot studies, Regional Monitoring Programs, and permit requirements. In addition, the State Water Board’s Division of Water Quality (DWQ), Division of Drinking Water (DDW), and Office of Information Management and Analysis (OIMA) have convened expert panels, funded research, and developed guidelines and regulations to monitor CECs in aquatic systems statewide. A CEC Program is currently in progress to develop a statewide CEC management strategy that will result in more coordinated efforts to address CECs in the environment.

USEPA 2021.