Towards the outbreak tail, what is the public opinion about wastewater surveillance in the United States?

The American public holds opinions on a wide variety of health topics, ranging from smoking and vaccinations to policy issues such as healthcare reforms (Jacobs & Mettler 2011; Duch et al. 2018; Al-Jayyousi et al. 2021; Haeder 2021; Findling et al. 2022; Wright et al. 2022). The public's awareness and beliefs can be shaped by highly contextual nuances, such as personal experiences, and are influenced by sources of information, such as media outlets (Benelli 2003; Xia et al. 2022; Goidel et al. 2023). In addition, a community's trust in and acceptance of work, such as wastewater surveillance, may change over time, emphasizing the importance of ongoing assessments of trust and acceptability of the continued health surveillance towards the end of the coronavirus disease 2019 (COVID-19) pandemic public health emergency. The social license around this topic can be affected by spillover effects from politicization and association with public health interventions, such as lockdowns, as well as trust in policies and responses by federal, state, and local public health agencies (Cooper et al. 2022; SteelFisher et al. 2023). During 2022–2023, there was a change in public confidence and trust in a variety of health system actors, including doctors, public health leaders, and medical research scientists (Del Ponte et al. 2023). Changes in public health surveillance methods have also occurred owing to the COVID-19 pandemic, including the rapid growth of widespread wastewater surveillance (Clark et al. 2024). Only a few studies have attempted to evaluate the public acceptance of wastewater surveillance to address health issues (Hill et al. 2022; Holm et al. 2022; LaJoie et al. 2022; Riback et al. 2023). Support for public health wastewater surveillance by wastewater treatment plant operators in New York is directly associated with their operational capacity to collect samples (Hill et al. 2022), while residents from the city of Louisville, Kentucky (Holm et al. 2022), and formerly incarcerated individuals (Riback et al. 2023) were generally supportive of wastewater surveillance for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Our earlier nationwide survey (LaJoie et al. 2022) found strong support for using wastewater to surveil diseases (92%), environmental toxins (92%), and terrorist threats (88%), and that an entire-community scale of surveillance was the most acceptable. However, these studies collected data during the peak of the pandemic and thus are of limited value to public policy and decision-makers in the post-pandemic period.

For wastewater surveillance, the intersection of scientific ethics and the public's privacy rights are both important and complex because of the absence of national and international regulations (World Health Organization 2017; Gable et al. 2020; Hrudey et al. 2021; Bowes et al. 2023). Moreover, public notice and input (Whitford & Yates 2023) are usually not provided or sought before conducting wastewater surveillance. Additionally, no clear model for public health surveillance is available to be used in situations where opting out of community surveillance due to individual privacy preferences conflicts with public health interests. A useful example of this is the tobacco regulation. Although smoking and the use of tobacco products are largely perceived as personal choices, over the past 70 years, we have witnessed a shift from unawareness that smoking causes lung cancer to the acceptance of scientific evidence to support regulations that limit the sale and use of tobacco products (United States 1964; Marshall 2016; Duch et al. 2018). Following the United States (1964) Surgeon General's report on Smoking and Health, public opinion polling captured changing attitudes towards smoking. Before the report was issued, only 50% of Americans believed that smoking was a serious health concern. By 1986, 86% of Americans agreed that secondhand smoke was a problem (United States 1964; Marshall 2016; Duch et al. 2018). This shift in attitude has led to policy changes; the confluence of accepted scientific evidence and supportive public opinion is now enshrined in tobacco regulations meant to preserve community and individual health. Monitoring the pulse of American attitudes toward topics that can influence policy actions is important, and a gap exists regarding what ethical or privacy concerns may be pertinent to wastewater surveillance and other types of public health surveillance during non-crisis periods.

This study aims to fill this gap by comparing public opinion during the peak of the COVID-19 pandemic and towards the tail of the outbreak in the United States. Specifically, we investigated across categories of awareness and knowledge, support for or opposition to surveillance, and privacy concerns and attitudes. We also considered evidence from media mentions. Considering the decrease in the severity and mortality rate of COVID-19 (Marziano et al. 2023) and the increasing polarization and politicization of the field of public health (Findling et al. 2022) from 2022 to 2023, changes in public opinion were expected regarding wastewater surveillance. Based on the survey, this study derived key insights and recommendations to inform policies and practices for public health-focused wastewater surveillance boundaries in the post-pandemic period.

Data for the total monthly mentions of ‘wastewater’ or ‘sewer’ and related terms in popular United States media were obtained from Cision U.S. Inc. (2023), for the period of July 2021–May 2023. Assessed media mentions included any combination of the terms ‘sewage’, ‘sewage + COVID’, ‘sewage + monitoring’, ‘wastewater’, ‘wastewater + COVID’, ‘wastewater + monitoring’, or ‘wastewater + surveillance’.

This study is a one-year follow-up of a previous study (LaJoie et al. 2022) on wastewater-based epidemiology, privacy concerns surrounding the collection of wastewater samples, and the use of acquired data, along with privacy awareness from an online survey conducted in the winter of 2023. Using our 2022 nationwide wastewater surveillance opinion survey as the baseline (hereafter referred to as Wave 1), we repeated the survey in 2023 (hereafter referred to as Wave 2) near the end of the national pandemic emergency to evaluate changes in opinions and attitudes. For Waves 1 and 2, the recruitment matrix and data collection instrument (Supplementary Table S1) were unchanged. Qualtrics XM (Provo UT USA, 2023) was contracted to recruit prescreened participants from their research panels, comprising individuals who had previously volunteered to participate in online research studies. Potential participants were randomly recruited via an email invitation by Qualtrics, who applied a stratified recruitment process to ensure that our sample quota mirrored the United States population in terms of race, ethnicity, non-rural residency, and English speaking. Sampling continued until the desired quotas for each stratum were satisfied (Miller et al. 2020; Douglas et al. 2023). The survey was limited to adults in the United States (over 18 years old) and English-speaking urban and suburban residents; the survey excluded rural residents. Qualtrics prescreened and removed potential participants from rural areas before sending survey invitations. Additionally, the survey asked respondents to self-identify whether they lived in mostly urban, suburban, or rural areas as part of the demographic question block. Excluding rural participants was necessary because rural areas are less likely to be included in wastewater surveillance owing to their higher reliance on individual septic systems rather than community-wide shared piped sewer systems (Holm et al. 2023). Survey respondents received compensation from Qualtrics valued at 10 USD.

Wave 1 data was collected in January and February 2022, and Wave 2 data was collected in February and March 2023. We removed approximately 60 obvious duplicate IP Addresses from Wave 2 that were the same as those in Wave 1.

An 80-item questionnaire comprised of a click-through consent and prompts that investigated knowledge, awareness, and support or opposition to public health surveillance practices, the privacy attitudes questionnaire (PAQ) (Chignell et al. 2003; Giang et al. 2023), and demographic questions. The survey responses were Likert type, rank ordering, select one, and choose all. The PAQ considers privacy a psychometric construct, which is limited to the real (physical) world and the digital realm. Four attitudes related to privacy were explored in the PAQ: exposure, monitoring, protection, and willingness to share information. The PAQ is not specific to public health or sewer surveillance but assesses general privacy limitations.

To determine the strength of awareness, knowledge, and support or opposition to wastewater surveillance, we collapsed the upper two categories of the Likert-type rating scale; for example, ‘agree’ or ‘strongly agree’ was merged into one category ‘agree’. The PAQ scores were computed as a sum (Chignell et al. 2003). To check for statistically significant differences between our study and the 2022 public opinion, the Mann–Whitney U test was conducted using R version 4.3.1 and R Studio 2023.06.1 (R Core Team 2021), and a p-value of 0.05 was considered statistically significant.

The University of Louisville Institutional Review Board approved this project as Human Subjects Research (IRB number: 21.0877). Informed consent was obtained from the participants by clicking through the preamble to the online survey instrument.

Two cohorts' data from a large nationwide sample provided insights into public opinion on wastewater surveillance as a public health tool during the end stage of the COVID-19 public health emergency (Wave 1 survey responses, N = 3,083; Wave 2 survey responses, N = 2,936). In both waves, more respondents were female, white, older, college-educated, and earned less than 40,000 USD. In addition, approximately 70% of the respondents described their living environments as mostly suburban and approximately 30% as urban in 2022 and 2023 (Supplementary Table S2).

Knowledge about how sewer surveillance could be used was measured using three questions: (1) could COVID-19 be detected in sewage? (Correct answer: yes); (2) could sewer monitoring determine which person (or persons) in a household had COVID-19? (Correct answer: no); and (3) which of the five stated assessment methods could most quickly detect COVID-19 in a community? (Correct answer: sewer monitoring). Answers were summed to produce a knowledge score between 0 (none correct) and 3 (all correct). Overall, respondents maintained low knowledge of sewer monitoring with only 17% answering all three questions correctly in both 2022 and 2023. Notably, again in 2023, 47% of the survey respondents incorrectly believed that sewer monitoring could determine which individual in a household had COVID-19, a figure that remained largely unchanged from 2022 (48%).

The PAQ assesses the respondents' tolerance for exposure and monitoring, desire for protection, and willingness to share information (Chignell et al. 2003; Giang et al. 2023). Lower scores indicated higher levels of privacy concerns across the four domains. The mean scores in 2023 were 24.0/50 (48%) for personal information, 21.7/45 (48%) for exposure, 27.7/45 (62%) for monitoring, and 31.4/40 (79%) for protection. There was a significant difference (2022 versus 2023; p-value < 0.05) between the waves for exposure, monitoring, and personal information. The level of concern regarding protection remained unchanged (2022 versus 2023; p-value = 0.97), possibly indicating individuals' actions to safeguard themselves from intrusion. Overall, protection garnered the lowest level of concern, aligning with the widespread support for wastewater surveillance activities related to the threat of terrorism in other areas of our survey.

Currently, no existing precedent regarding health privacy in the context of wastewater surveillance is available. Participation is not entirely voluntary; individuals within the community do not have the option to opt out of surveillance to preserve their privacy. Because the goal of surveillance is to monitor health across a population while preserving individual anonymity, authorization comes from health officials and local governments with broad authority to act and regulate to protect public health and welfare. Individuals who feel ethically obliged, perhaps out of altruism, to allow their health information to be used for research typically exhibit certain associated characteristics, such as trust in the system and healthcare providers (Raj et al. 2020). In the context of wastewater surveillance, the assumption that altruism or generosity contributes to what is being flushed into the sewer implies that privacy, particularly at the household scale, should not be sacrificed automatically. Furthermore, no established precedent for community health surveillance of this nature exists, which typically does not involve the regular gathering of public opinion or the provision of notice to gather input regarding sampling acceptance. In contrast, customers can ‘opt-in’ to other public health surveillance at restaurants and pools, via a choice to utilize those businesses or not. In addition, health surveillance results at businesses are often prominently displayed in the form of grades or notices of violations. Alternatively, wastewater results are often shared via online dashboards, which can be difficult for the public to interpret (Naughton et al. 2023). Perhaps the most comparable concerns arise from recent discussions regarding privacy and artificial intelligence systems for face recognition (Whitford & Yates 2023). Face recognition technology also has a regulatory gap concerning privacy and oversight; individuals may not be aware when their data is being collected, and often an individual does not have an option to opt out of community surveillance (Whitford & Yates 2023).

Our research results, gathered through a 2023 online public opinion survey conducted towards the end of the national pandemic emergency, should influence policies and best practices for public health-focused wastewater surveillance post-pandemic. Our analysis presents an opportunity to learn boundaries regarding what is acceptable to target and at what appropriate geographic scales. A few salient recommendations are as follows:

• 1. Public education is needed. Currently, there is no anti-wastewater surveillance movement on its scope or scale. However, it is still important to take action to increase public awareness and buy-in. Potential activities include geotargeted public education campaigns in areas where knowledge and awareness are low, as well as inclusion in school environmental education and health curricula.

• 2. Wastewater surveillance is supported at levels comparable with other public health surveillance activities. As with pool and restaurant inspections, health departments should establish standard policies and funding for wastewater surveillance.

• 3. Support extends beyond global health threats and infectious diseases. Toxins and terrorist threats offer opportunities to expand wastewater surveillance with high levels of public support.

• 4. Support is conditional. Surveillance targets, such as pathogens, toxins, biological and chemical terrorist threats, and illegal activities, are generally considered acceptable. Sampling for lifestyle behaviors, such as alcohol consumption and eating patterns, is generally not accepted.

• 5. There is an overall concern about anonymity. Sampling is most supported when the catchment size ensures full anonymity for households. We infer that the public does not want wastewater surveillance for individual human genetic monitoring.

Despite many strengths, this study had some limitations. First, the study was conducted only in the United States. Outside the United States, public opinion may differ regarding this subject, and such studies would be valuable. Second, our invitation to participate excluded rural communities, which may vary given the differing public health dynamics in rural areas compared with more urban regions. Finally, Wave 2 contained a small set of respondents from Wave 1 (N = 66). Although these participants, identified through IP addresses, were removed to allow inferential statistical tests, there is always the possibility that some respondents used different IP addresses (e.g., home and work) or a VPN across the years.

This research survey of two different cohorts over time revealed public support for wastewater surveillance for public health purposes. Given that our survey delves into wastewater testing for more than just COVID-19, it provides a thorough public opinion on wastewater surveillance in the United States beyond the pandemic. This support is conditional and best understood through the lens of the COVID-19 pandemic, during which the value proposition of public protection was popularized. The survey consistently showed high acceptance for the expansion of wastewater surveillance as a standard complement to public health tools in other areas of public health protection; however, wastewater surveillance does not receive the public pushback that other COVID-19-related health system actors have witnessed. The future of wastewater surveillance presents a rich case study involving public knowledge, scientific boundaries, and privacy concerns.

Conceptualization, Methodology, Project administration, and Supervision: T.S.; Formal analysis and Writing – original draft: R.H.H.; Writing – review and editing: R.H.H., L.B.A., H.D.N., A.S.L., and T.S.

This work was supported by grants from the James Graham Brown Foundation and Owsley Brown II Family Foundation. The funders had no role in the study design, data collection and analysis, decision to publish, or manuscript preparation.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.