SCIENCE SPOTLIGHT: Pharmaceuticals, pesticides, and contaminants of emerging concern in wastewater discharges to San Francisco Bay

The issue of water quality in the Delta has become increasingly important in recent years. The drought has made the water quality conditions worse, leading to several harmful algal bloom events. While we have regulations in place for certain aspects of water quality, such as salinity and mercury, there is a growing interest in developing new regulations to address the occurrence of harmful algal blooms and other unregulated chemicals that we have limited knowledge about. These chemicals, called contaminants of emerging concern or CECs, include pharmaceuticals that end up in our wastewater treatment system, pesticides and herbicides with constantly evolving formulations, and even personal care products like sunscreens. Research is actively being conducted to understand how these contaminants of emerging concern may impact both aquatic life and humans.

Studies have found that certain pharmaceuticals can cause physiological abnormalities in fish and amphibians or have adverse reproductive effects on aquatic wildlife.  Studies are also looking at other ways these chemicals might alter the behavior of aquatic organisms, such as becoming more susceptible to predation or less successful at feeding.

Researchers often establish ecotoxicological thresholds for CECs so that below those thresholds, there are no substantial adverse effects on aquatic life.  These thresholds become important to try to maintain concentrations below in our natural waterways.

“Overall, this body of work is struggling to keep up with the dynamic nature of the industries that are producing these chemicals, and monitoring of CECs is not something that’s routinely done,” said Dr. Larsen.  “That’s why these contaminants feature prominently in the Science Action Agenda in our action 5E, which is to quantify spatial and temporal patterns and trends of chemical contaminants and evaluate ecosystem effects through monitoring, modeling, and laboratory studies.  Galvanizing more studies and synthesis about water quality overall is also an objective behind the selection of water quality as a theme for the 2024 Bay-Delta Science Conference.”

In this spotlighted article, Pharmaceuticals, pesticides, and ultraviolet filters in wastewater discharges to San Francisco Bay as drivers of ecotoxicity, a research group from Stanford and SFEI undertook a study of some of the least well-monitored CECs in the wastewater treatment plant outfall to the San Francisco Bay.  They sampled the effluent (or what’s coming out of the wastewater treatment plants) from six of the major wastewater treatment plants shown on the map.

The researchers tested for 21 different contaminants that fell into three categories:

  • Chemicals in sunscreen, including the chemical oxybenzone, which is banned in sunscreens that are used and sold in Hawaii because of known harm to marine life and reefs;
  • household pesticides, including those that are present in pet flea and tick products, which then enter the wastewater treatment plant system when pets are bathed, and also foggers that are used in people’s houses; and
  • pharmaceuticals.

The researchers then used a hydrodynamic model of the bay to figure out how much those chemicals in the wastewater treatment plant effluent would get diluted in the environment.  And they learned through these models that the least amount of dilution would occur in the South Bay.  They next compared the expected diluted concentrations of the chemicals there to known ecotoxicological thresholds to determine whether they would potentially pose a threat to aquatic ecosystems.

“What they found is that the 21 CECs that they tracked were pervasive in the wastewater treatment plant outflow that they sampled,” said Dr. Larsen.  “Out of the 21 CECs, 11 were detected in at least 70% of the samples, so a large majority with three of the pharmaceuticals and one of the urban pesticides found in 100% of the samples.  Two of the high detect CECs were sunscreen chemicals, and four of them were urban pesticides.”

“Out of the eleven high detect CECs, six exceeded ecotoxicological thresholds at concentrations that were present in the effluent, including the sunscreen chemical oxybenzone, the one that’s banned in Hawaii, and four urban pesticides.  Accounting for the dilution in the San Francisco Bay, imidacloprid, which is a pesticide to control fleas and ticks in pets, would be present in concentrations over two times the ecotoxicological limit, and one pharmaceutical would be present at a concentration approximately equal to the threshold.”

These results were specific to the San Francisco Bay, but Dr. Larsen noted they wouldn’t likely be that different if the sampling were done with wastewater treatment plant effluent being discharged into the Delta.  It underscores the need for more studies like this to be conducted in the Delta.

The researchers suggested that the pesticide concentrations could be reduced by about half by treating the effluent with ozone and ozonation treatment, which has been shown to diminish concentrations of that particular pesticide.  However, that would likely be expensive.

Chair Virginia Madueño asked about microplastics.

“Microplastics are equally worthy of our consideration as a scientific community in that microplastics in the ocean could be moved into the Bay and the Delta through tidal action … One of the big challenges that I see for the science community is there are just so many of these contaminants, and the effects are so diverse.  Researchers now are looking at the effects on different life stages of fish that we regulate for, but there are very likely to be impacts that are much wider-ranging than those species-specific or life stage-specific impact.  This is why it is a science action, as it is a huge issue right now.  Our role as a science program is to continue to perform synthesis of those studies where they exist and to encourage additional studies through funding work, through our Delta research awards solicitation, for which projects are required to be responsive to the Science Action Agenda, and then sponsoring specific workshops or like in this case, where the Bay Delta science conference will have a water quality theme.  I expect this as a topic that will come up quite a lot.  I know that the Delta Independent Science Board also has some interest in looking into a future review that focuses on water quality and contaminants of emerging concern.  So that’s something we’ll see more discussion about in the future.”

Activities of the Delta Science Program

Social Science Community of Practice quarterly meeting:  The meeting featured a presentation by researchers from Washington State University on how the Puget Sound Partnership is integrating social science across its organization.  There was also a discussion of how they’re attempting to monitor human well-being in that region.  They also discussed the analysis of socio-economic indicators.  Representatives from the Collaborative Science and Adaptive Management Program attended and requested the Community of Practice to provide feedback on adding socio-economic analyses to their Delta smelt structured decision-making project.

NCEAS Working Group on Integrating Social Science Data:  The Delta Science Program regularly contracts with the  National Center for Environmental Analysis and Synthesis or NCEAS to provide training and synthesis support for agency staff and academics across the Bay Delta to conduct research that addresses big picture questions for which the answers often lie within and across many disparate data sets; this requires synthesis.  Two years ago, the Science Program sponsored an NCEAS working group to evaluate drivers of the estuarine food web based on decades of monitoring data.

Over the past summer and fall, the Science Program sponsored another working group to conduct research that integrates the human dimensions of the Delta into management decision-making.  The workgroup includes staff from the Council, Department of Water Resources, State Water Resources Control Board, the California EPA, Office of Environmental Health Hazard Assessment, California Department of Fish and Wildlife, San Francisco Estuary Partnership, and academic participants from UC Davis and UC Merced.  The training NCEAS conducted consisted of three one-week workshops that provided instruction on how to implement open data science.  The working group is continuing to work on two research syntheses:  (1) to understand how restoration benefits are distributed across the Bay-Delta in a way that considers social vulnerability and the benefits and burdens of restoration, and (2) to understand the risks and benefits of levees to vulnerable populations across the Delta.

Delta Science Funding Proposal Solicitation:  The upcoming proposal is expected to be released by the end of the year.  This round of funding will emphasize participatory research that engages the communities in the research process.  To help connect potential researchers with Tribes or community-based organizations, the Delta Science Program conducted a survey to help researchers connect with California Native American tribes or community-based organizations.  The intention was to generate new partnerships that will contribute proposals to the forthcoming solicitation.

California Sea Grant state policy fellows:  The Council is recruiting five state policy fellows who will work within the adaptive management units, collaborative science and peer review unit, science funding team, science communication, synthesis, and decision support unit in the Planning and Performance Division.

Delta Collaboratory: Lessons learned from other systems

It’s been a long-standing priority of the Delta Stewardship Council and the Delta Science Program to establish a modeling collaboratory, which is defined as a set of shared modeling resources, best practices, and support personnel that facilitate complex decision-making under deep uncertainty.

Former Delta Lead Scientist Dr. Peter Goodwin has established a collaboratory for the Chesapeake Bay.  They recently held a Global Collaboratory Summit to gather thoughts on the advancement of their collaboratory, but also to look more broadly beyond the boundaries of the Chesapeake and explore some of the challenges that they hold in common with other ecosystems like the Delta.  The Summit was attended by Dr. Steve Culberson, Lead Scientist for the Interagency Ecological Program (IEP).

Dr. Culberson shared his takeaways with the Council.  The collaboratory effort in Maryland has broad support from the University of Maryland and several state agencies, which is key for gaining legislative support.  To remain credible and relevant, the collaboratory must utilize the latest in computational and data visualization techniques and the required supporting infrastructure, which requires funding. It is a highly collaborative and interactive enterprise where participants strive for increased understanding and shared progress.

“The word that I used when asked for my impression of the collaboratory was acculturation,” said Dr. Culberson.  “It very much speaks to my previous experiences, which is you have to understand what it is people are coming to you to solve, how they are normally doing it within their communities already, and you have to meet them there.  So even though we’re talking about substantial infrastructure investments, I think what we’re really talking about is, is finding a culture where these collaborative modeling exercises can exist and know that they have support.”

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