Exposure to wastewater-related pathogens results in millions of cases of illness and an economic burden of 12 billion US dollars annually worldwide. Since 90% of the world?s household wastewater enters the environment without being disinfected, coastal beaches are often polluted by wastewater, which can greatly impact the health of those that swim and play at the beach.  Despite scientific advancements, coastal water quality monitoring approaches rely on outdated compliance practices that do not accurately identify public health risks.

This project directly measured pathogen concentrations, assessed sources of fecal pollution, and identified behaviors and other factors that put individuals at risk of illness from coastal water use at a tropical beach in Costa Rica. These data were used to demonstrate the utility of a holistic beach water quality management approach as a viable and effective alternative method for managing swimmer-associated health risks in tropical regions. This holistic management approach combined sanitary surveys, targeted water quality analyses of pathogens and indicators of fecal pollution, and quantitative microbial risk assessment (estimated risk to human health from fecal pathogens) that incorporated ethnographic and epidemiological studies. Our study demonstrates how advancing local understanding and building knowledge regarding risk from coastal recreation can, when coupled with appropriate technological and social interventions, improve microbial water quality management and public health at a local, regional, and even global level. This innovative study advanced the goals of the NSF Coastal SEES program by identifying practices that expose people to fecal pathogens at beaches, improving sustainable tropical water management approaches, and recommending economically- and socially-feasible interventions to minimize human health risks. 

Using the polluted Costa Rican Jac? beach as a model system, this project made great strides in filling knowledge gaps associated with characterizing microbial quality in the tropics. Through short-term, intensive water quality sampling at our tropical study site, we determined that domestic wastewater pollution was prevalent year-round; yet, different pathogen types were most prevalent at different times of the year (rainy vs dry season) and varied between years. Given that no single indicator best correlated with pathogens, our results suggest that best practice is to use multiple indicators as surrogates for pathogen presence in tropical recreational waters. Our short-term sampling, combined with an analysis of over a decade of water quality data from the Costa Rican National Water Laboratory, identified that environmental factors explained less than 27% of microbial water quality data and indicated rainfall as a highly influential environmental factor at the study site. To collect the data necessary to demonstrate our beach management approach, we simultaneously executed water quality, ethnographic, and epidemiology studies to understand the relationship between swimming-related illness and beach water quality. This component of the research involved 160 water quality samples, >5,000 epidemiological interviews, 500 behavioral observations, and semi-structured interviews with over 80 different stakeholders. Through stakeholder interviews, mass balance wastewater models, and quantitative microbial risk assessment, we proposed a novel methodology for sanitation selection for urbanizing tropical beaches that identified the sanitation options that could sufficiently reduce pathogens and nutrients in coastal waters to foster safer conditions by using our study site as a case study.

This project provided strategies to enhance coastal water management to maintain or achieve low risk of illness for beachgoers worldwide by identifying improved household-wastewater pollution indicators for tropical regions, implementing an emerging holistic approach to water quality management, and incorporating the critical roles that human activities and perception play in mitigating risk of illness from microbial contaminants. In collaboration with identified governmental and non-governmental stakeholders, the recommended societal changes were strategically communicated to individuals locally and regionally. The results of the project were shared with key stakeholders in a series of online and in-person report-back events. Participants provided valuable feedback on the process of reporting-back the results, as well as opinions regarding the results themselves, through an online questionnaire. This integral step in the research process enhances international and cross-disciplinary collaborations using methods that encourage participation from all stakeholders.

To date, this project has resulted in a total of 22 peer-reviewed publications and 27 presentations. This project engaged many different stakeholders including community members, national governments, and international organizations in order to effectively initiate improvements in coastal water management. Community and K-12 education were promoted through the creation of coastal water quality outreach videos and a bilingual project blog. The interdisciplinary research community dedicated to improving coastal water quality was expanded through the training of 7 graduate students, 6 undergraduate students, and 4 postdoctoral researchers. Thirty undergraduate students from Costa Rican universities gained significant research experiences and we provided six months of training in molecular biology procedures for our Costa Rican government partners in advanced water quality laboratory methods, which improved their analytical capabilities and facilitated their SARS-CoV-2 wastewater surveillance program.

Last Modified: 02/07/2023
Modified by: Maryann R Cairns