Grantee Research Project Results
Final Report: Real-Time Analysis of Aerosol-Phase Plastic Additives in a Coastal Marine Environment in California
EPA Grant Number: R840424Title: Real-Time Analysis of Aerosol-Phase Plastic Additives in a Coastal Marine Environment in California
Investigators: Slade, Jonathan H
Institution: University of California San Diego
EPA Project Officer: Chung, Serena
Project Period: May 1, 2022 through April 30, 2025
Project Amount: $399,464
RFA: Measurement and Monitoring Methods for Air Toxics and Contaminants of Emerging Concern in the Atmosphere (2021) RFA Text | Recipients Lists
Research Category: Early Career Awards , Air Quality and Air Toxics
Objective:
Plastics and other chemical additives are commonly found in everyday products like sunscreens, pharmaceuticals, and household items. When these products are discarded, they can wash into rivers and oceans, where they may remain for weeks or months. Until recently, most research believed that these pollutants mainly posed risks through water exposure. However, the ocean also produces sea spray aerosols—tiny airborne particles created when waves break and bubbles burst at the surface. This raises an important but unanswered question: can wastewater-borne and plastic-related pollutants be transferred from the ocean into the air that people breathe?
To answer that question, this EPA-supported project focused on coastal field measurements of paired water and aerosol samples in San Diego using advanced real-time and offline mass spectrometry techniques. Our main goal was to understand how pollutants transfer between the ocean and the atmosphere, and what this means for air quality in coastal communities. Additional field and laboratory measurements were conducted to assess instrument limitations and how pollutants transform once airborne. We used an online mass spectrometer for real-time measurements, specifically an extractive electrospray ionization high-resolution mass spectrometer (EESI-HRMS). At the same time, we collected aerosol filter samples and seawater samples, which were analyzed offline using high-performance liquid chromatography with linear ion trap Orbitrap tandem mass spectrometry. The three main objectives of this project were:
- Continuous online measurement and quantification of plastic additives in the aerosol phase with extractive electrospray ionization high-resolution mass spectrometry (EESI-HRMS) during summer and winter at a coastal site to evaluate seasonal and diel profiles;
- Quantify the targeted plastic additives in collected seawater and twice-daily high-volume aerosol filter samples employing Orbitrap LC-ESI-MS2; and
- Apply molecular networking and statistical analysis of the compositional data along with wave height, wind speed, biological activity, rainfall, and river discharge rates to assess drivers and conditions under which plastic additives become airborne.
Summary/Accomplishments (Outputs/Outcomes):
Our team provided the first direct evidence that wastewater-borne chemicals are found in coastal air (Cooper et al., 2025 in Science Advances). We found that pollutants such as sunscreen chemicals (oxybenzone, octinoxate), pharmaceuticals (carbamazepine), illicit drugs (methamphetamine, heroin), and tire additives (dibenzylamine) are present in sea spray aerosols at concentrations, in some cases, similar to those of well-known air pollutants, including polycyclic aromatic hydrocarbons (PAHs).
A key discovery was the detection of benzoylecgonine, a byproduct of cocaine, as a reliable chemical marker for wastewater pollution in the air. This compound occurs in sewage but isn't linked to direct emissions into the atmosphere. Finding it in aerosols clearly indicates that sewage-related pollution is being released into the air. We were able to link its presence in the air to sea spray aerosol emissions connected to polluted wastewater inputs from the Tijuana River.
Our laboratory experiments demonstrate that when pollutants transfer from water to aerosols, their chemistry undergoes considerable changes (Cooper et al., 2024, in ACS ES&T Air). For example, oxybenzone, a common sunscreen ingredient, breaks down 100–1000 times faster in aerosols than in seawater. While oxybenzone can persist for days in surface waters, it decomposes within minutes once airborne. Even more concerning, this change produces byproducts such as benzophenone and benzoic acid, which are thought to be more toxic than the original chemical. This finding emphasizes that aerosols are not merely passive carriers of pollutants but serve as active chemical reactors capable of forming new, potentially more harmful compounds.
Seasonal field campaigns revealed that ultraviolet (UV) filters, such as octocrylene, were more abundant in seawater and aerosols during the summer, consistent with higher sunscreen use and wastewater inputs (manuscript in progress). They also showed that the viscosity and physical state of sea spray aerosols vary with season and environment. In winter, particles are more viscous (semi-solid), while in summer they tend to be more liquid-like (manuscript in progress). Liquid particles enable chemicals and oxidants to diffuse and react more quickly, increasing the likelihood of pollutant transformation and human exposure. These findings suggest that summer months may represent periods of heightened risk, as both pollutant emissions and aerosol reactivity are at their peak.
The project evaluated the use of real-time mass spectrometry (EESI-HRMS) to monitor aerosol pollutants in the field continuously. While the instrument successfully detected major sea spray organics, its sensitivity was not enough to quantify trace pollutants above background levels in ambient marine air. It was also affected by the relative humidity and viscosity of the aerosol during collection (Kruse et al., 2024, in Analytical Chemistry). Additionally, although this method can differentiate isobaric compounds, it cannot distinguish isomers, including oxybenzone and bisphenol-A, species detected in aerosol samples using offline mass spectrometry. Instead, quantitative results were obtained using Orbitrap LC-MS/MS on seawater and filter samples. This reveals a significant technical limitation and underscores the ongoing need to develop improved real-time detection techniques.
Two new perspective articles resulting from this work outlined the atmospheric chemical transformations of airborne plastics and plastic chemical residues (Zhang, Slade, Ault, and Chan, 2025, in Environmental Science and Technology) and a framework for real-time and continuous monitoring of airborne plastics and other CECs (Cooper, Rogers, Wiggin, and Slade, 2023, in Environmental Science and Technology). The publication of the results in Science Advances (Cooper et al., 2025) generated widespread media attention and tangible policy outcomes, including contributing to the body of work that led to the adoption of new legislation in the California State Legislature to improve wastewater treatment infrastructure in the South Bay region of San Diego. The work helped motivate a new memorandum of understanding between the EPA and the Mexican government to strengthen wastewater treatment across the U.S.–Mexico border. The research was featured in dozens of outlets, including The Los Angeles Times, San Diego Union-Tribune, Chemical & Engineering News (C&EN), KPBS, NBC, ABC, CNN, The Hindu, The Tribune, and Smart Water Magazine. A UC San Diego public webinar and interviews with KPBS Midday Edition further helped explain the findings to the public. This response illustrates how federally funded research can drive both scientific discovery and prompt immediate environmental action, ensuring that results are effectively translated into enhanced protection for communities.
Journal Articles on this Report : 5 Displayed | Download in RIS Format
| Other project views: | All 13 publications | 5 publications in selected types | All 5 journal articles |
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Cooper AW, Rogers MM, Wiggin KJ, Slade JH. We need a “Keeling curve” approach for contaminants of emerging concern. Environmental Science & Technology 2023;57:10147–50. |
R840424 (2022) R840424 (Final) |
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Cooper A, Shenkiryk A, Chin H, Morris M, Mehndiratta L, Roundtree K, Tafuri T, Slade JH. Photoinitiated degradation kinetics of the organic UV filter oxybenzone in solutions and aerosols: Impacts of salt, photosensitizers, and the medium. ACS ES&T Air. 2024;1(11):1430-41. |
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Zhang Y, Slade JH, Ault AP, Chan AWH. An atmospheric chemistry perspective on airborne micro-and nanoplastic particles. Environmental Science & Technology. 2025;59(16):7810-9. |
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Kruse SM, Tumminello PR, Moore AN, Lee C, Prather KA, Slade JH. Effects of relative humidity and phase on the molecular detection of nascent sea spray aerosol using extractive electrospray ionization. Analytical Chemistry. 2024;96(31):12901-7. |
R840424 (2023) R840424 (Final) |
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Cooper A, Cancelada L, Torres RR, Belcher K, Small M, Belda-Ferre P, Morris C, Mitts B, Dinasquet J, Knight R, Slade JH, Prather KA. Identifying wastewater chemicals in coastal aerosols. Science Advances. 2025;11(22):eads9476. |
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Supplemental Keywords:
plastics, additives, aerosol, marine, mass spectrometryRelevant Websites:
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.