Objective

The overall objective of the project is to evaluate the exposure of a healthy population of water-associated bird species to per- and polyfluoroalkyl substances (PFAS) within Peters Canyon Wash, downstream in San Diego Creek, and in off-channel wetlands. The project team will evaluate whether modeling risk from PFAS in bird eggs and fish, combined with existing laboratory-derived toxicity reference values (TRVs), reflects ongoing field monitoring indicating these birds are not impacted due to PFAS (or other chemicals). The project team will focus on bird species at a high trophic level, high site fidelity, and that forage within a small range during nesting. The study takes advantage of a store of bird eggs collected for active total maximum daily load monitoring for the County of Orange for over 10 years. Eggs were collected from breeding birds, including grebes (Aechmophorus and piedbilled [Podilymbus podiceps] grebes), shorebirds (American avocets [Recurvirostra americana] and black-necked stilts [Himantopus mexicanus]), and other water-associated bird species such as American coots (Fulica americana). The study will help address several outstanding data gaps on field ecology studies; specifically, this project will evaluate the accuracy of existing PFAS TRV with a population of healthy birds.

Technical Approach

Consistent with the project objectives, the approach uses two distinct technical tasks to assess PFAS toxicity to birds from analyzing PFAS in eggs of up to four species of aquatic birds representing three feeding guilds (i.e., omnivores, invertivores, and piscivores) and prey fish. The tasks are:

Analysis of Archived Samples: PFAS analyses will be conducted on archived egg samples from up to four bird species collected over three nesting periods. Egg samples will be from water-associated bird species that are: (1) high on the food chain, (2) have high site fidelity, and (3) forage within a small range during nesting. Archived homogenized whole-body composite fish tissue samples co-located in space and time with a subset of the egg samples also will be analyzed.

Validation of TRV: Homogenized whole egg PFAS concentrations will be compared to laboratory-determined egg PFAS TRVs to field-validate the existing TRVs. Fish PFAS concentrations will be used in existing dietary risk models to evaluate laboratory determined dietary PFAS TRVs. Risk conclusions determined using TRVs will be compared to field monitoring conclusions that breeding bird populations downstream are healthy.

Benefits

This project will aid understanding of PFAS impact and transport near the military facilities Marine Corps Air Station (MCAS) Tustin and El Toro, and re-emphasize the ecological health of local bird populations. Results will aid risk assessments in the watershed and provide insights for other Department of Defense (DoD) facilities. Repurposing previously collected samples extends their use and provides significant cost savings. Basic questions that may be answered include: (1) whether PFAS from MCAS Tustin and El Toro are detectable in Peters Canyon Wash (also known as Peters Canyon Channel) and downstream samples, and (2) whether PFAS are detectable in the main dietary items of nesting birds downstream. If PFAS are detected in samples adjacent to MCAS Tustin, this study will determine changes in concentrations from upstream to downstream in dietary items (fish). Finally, the data will be used to determine the level of risk of adverse effects that PFAS pose to birds in the watershed. This project is expected to demonstrate that eggs of selected bird species are an effective method of monitoring exposure and assessing the potential adverse population-level effects on birds. Results from this study will be transferable to other DoD locations where PFAS are expected to be present. (Project Completion – 2024)