Over the last decade, researchers and government agencies have begun to collect occurrence, fate, and toxicity data for a number of chemicals. Some of these chemicals have been classified as contaminants of emerging concern (CECs), often due to due to their high volume use, potential for toxicity in non-target species, and the increasing number of studies that report their occurrence in the environment. CECs can be broadly defined as synthetic or naturally occurring chemicals that are not regulated or commonly monitored in the environment but have the potential to enter the environment and cause adverse ecological or human health impacts.
The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) has been investigating CECs since 2001 and developed a formal workgroup to address the issue in 2006. The RMP Emerging Contaminants Workgroup (ECWG) includes representatives from RMP stakeholder groups, regional scientists, and an advisory panel of expert researchers that work together to address the workgroup’s guiding management question – Which CECs have the potential to adversely impact beneficial uses in San Francisco Bay? The overarching goal of the ECWG is to develop cost-effective strategies to identify and monitor CECs to minimize impacts to the Bay. The RMP has generated one of the world’s most comprehensive datasets for CECs in an estuarine ecosystem. CECs investigated to date include poly- and perfluorinated alkyl substances (PFASs), alkylphenols, current use pesticides, pharmaceuticals and personal care products (PPCPs), and flame retardants including polybrominated diphenyl ethers (PBDEs) and their replacements.
This strategy document was developed as part of a continuous effort to refine approaches for supporting the management of CECs in San Francisco Bay. The strategy is consistent with recommendations from the California State Water Resources Control Board’s nationally- recognized expert panel on monitoring CECs in the State’s aquatic systems. The RMP CEC strategy described herein consists of three major elements.
First, for CECs known to occur in the Bay, the RMP has evaluated relative risk using a tiered risk and management action framework (Section 2.2). This risk-based framework guides future monitoring proposals for each of these contaminants (Section 3.0), the results of which may provide key data to update initial evaluations of potential risk. The criteria listed below were used for placement in each tier.
Tier I (Possible Concern) – Uncertainty in measured or predicted Bay concentrations or in toxicity thresholds suggests uncertainty in the level of effect on Bay wildlife. CECs in Tier I include: alternative flame retardants (BEH-TEBP, EH-TBB, DBDPE, PBEB, BTBPE, HBB, DP, TDCPP, TCEP, TCPP, TBEP, TPhP, other organophosphates); bisphenol A; bis(2-ethylhexyl) phthalate (BEHP or DEHP) and butylbenzyl phthalate (BBzP); poly- and perfluorinated alkyl substances (PFASs) other than PFOS; short-chain chlorinated paraffins; other pesticides; and single-walled carbon nanotubes.
Tier II (Low Concern) – Bay occurrence data or predicted environmental concentrations (PECs) suggest a high probability of no effect on Bay wildlife (i.e., Bay concentrations are well below toxicity thresholds and potential toxicity to wildlife is sufficiently characterized). CECs in Tier II include: pyrethroids; many PPCPs; hexabromocyclododecane (HBCD); and polybrominated dioxins and furans (PBDD/Fs).
Tier III (Moderate Concern) – Bay occurrence data suggest a high probability of a low level effect on Bay wildlife (e.g., frequent detection at concentrations greater than the predicted no effect concentration (PNEC) or no observed effect concentration (NOEC) but less than EC10, the effect concentration where 10% of the population exhibit a response, or another low level effects threshold). CECs in Tier III include: PFOS; fipronil; nonylphenols and nonylphenol ethoxylates; and PBDEs.
Tier IV (High Concern) – Bay occurrence data suggest a high probability of a moderate or high level effect on Bay wildlife (e.g., frequent detection at concentrations greater than the EC10 or another effects threshold). No CECs are currently assigned to Tier IV for the Bay.
The second element of the RMP CEC strategy involves review of the scientific literature and other CEC aquatic monitoring programs as a means of identifying new CECs for which no Bay occurrence data yet exist (Section 4.0). Initial monitoring to establish the presence of these newly identified CECs in the Bay is needed to evaluate the risks they may pose.
Finally, the third element of the strategy consists of non-targeted monitoring. The RMP has launched two types of non-targeted monitoring projects. The first, involving broadscan analyses of Bay biota samples, is designed to identify previously unknown CECs present in Bay organisms (Section 5.1). The other is expected to establish a bioassay useful for identifying the presence of contaminants with estrogenic effects (Section 5.2).
The RMP’s multi-faceted approach to addressing the challenge of CECs is designed to be flexible and adaptive to new data from both internal and external sources. Based on the strategy, a five-year plan indicating research priorities is outlined (Section 6.0).
It is anticipated that this special study will be conducted each year to insure the RMP is incorporating the most recent scientific findings regarding the monitoring of CECs in the Bay.
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