Introduction

Hygiene encompasses a diverse set of behaviours aimed at reducing the risk of disease transmission, spanning domestic and institutional settings. Modifying these behaviours can reduce the multiple exposure routes important for disease transmission through hands, food, and surfaces. Inadequate hygiene remains a major contributor to the global burden of disease: poor hand hygiene was linked with nearly three-quarters of a million deaths from diarrheal disease and acute respiratory infections in 2019 [1]. Inadequate food hygiene is a major source of the estimated 600 million cases of foodborne illness and 420,000 deaths in 2010, the last year for which global estimates are available [2]. Studies in healthcare and public settings have shown how specific pathogens move through environments via high-touch surfaces and a lack of robust hygiene protocols [3].

Climate change poses an escalating threat to population health. Over half of known human pathogenic diseases are aggravated by climatic factors, due to the alteration of behaviour, range, and longevity of vectors, hosts and reservoirs, and increased propagation of viruses, bacteria, and protozoa [4,5]. As these disease pressures rise, effective hygiene practices become increasingly critical to reduce infectious and chemical risks [6].

However, the same climatic changes that heighten the need for hygiene also undermine the infrastructure, resources and services that enable it. Slow-onset events, such as drought and land degradation, and acute shocks, such as floods and cyclones, are undermining water and sanitation systems and disrupting critical supply chains [7–12]. Climate change is reducing overall water availability, for example, through the reduction of glaciers and snowpack that are crucial for freshwater supply [13]. Seasonal and annual rainfall patterns are becoming less predictable, contributing to household water scarcity and heightened perceptions of insecurity that drive changes in household water use [14–16]. Without reliable access to water and sanitation services or hygiene products, the likelihood of unsafe hygiene behaviours and disease exposure increases, further exacerbating the health risks posed by climate change [1,12].

Climate hazards threaten all aspects of hygiene. Shifts in water resources and service reliability can trigger coping mechanisms that have direct implications for hygiene and health. Reduced water availability often forces households to prioritise water use for drinking and cooking over hygiene needs, reducing handwashing, bathing, or cleaning [17–23]. Households may also use more contaminated sources for washing, cleaning, or food preparation [24–26]. Water scarcity can decrease the frequency of handwashing and bathing, heightening risks of enteric and dermatological infections [19,27,28]. In coastal areas, saltwater intrusion further limits freshwater availability, increasing reliance on brackish water for household cleaning and bathing [29,30].

Alongside these slow-onset challenges, extreme weather events, such as floods and storms, can also reduce household access to water by damaging infrastructure. This can drive behaviours such as reduced hygiene and washing or laundering in contaminated waters [31,32]. Menstruating women and girls face specific challenges during disasters due to compounded barriers in accessing water and sanitation services or hygiene products [33–35]. People with disabilities may be at greater risk because of existing vulnerabilities and limited ability to express their hygiene needs or access safety information [36,37]. Floods and cyclones can also destroy or overwhelm sanitation facilities, leading to increased open defecation or faecal contamination of the home environment [38,39]. Households are also exposed to pathogens and chemical pollutants through contamination of surfaces and stagnant water left behind from floods [40–43].

Food hygiene is similarly threatened. Changes in ambient temperature, precipitation, and humidity affect food safety during storage and preparation, facilitating the growth of and spread of foodborne pathogens and toxins [44,45]. Ocean warming, climate-driven acidification, and shifts in salinity and precipitation alter the biochemical properties of water, impacting microflora and the persistence and patterns of pathogenic bacteria, harmful algal blooms, and chemical contaminants in foods [46–48]. Extreme weather events can damage or contaminate household food storage facilities, increasing the risk of cross-contamination and outbreaks of foodborne illness.

Research on the role of climate determinants in population health is increasing [49,50], supported by national adaptation plans and strategic research agendas that emphasise actions to reduce the impacts of climate change [51,52]. Recent frameworks, including the National Academies of Medicine’s research agenda [53], the European Commission’s Strategic Research and Innovation Agenda on Health and Climate Change [54], and the National Institute of Health’s Climate Change and Health Initiative [55], identify priority domains such as health impacts, adaptation and mitigation, infrastructure and capacity, and evidence-to-policy translation. The World Health Organization’s (WHO) latest global research agenda on climate change and health similarly highlights these domains, with a strong emphasis on equity and action priorities. While water and sanitation services are recognised as a critical component across these agendas, hygiene, encompassing behaviours, services and enabling determinants, remains comparatively under-specified [56].

Hygiene does feature in a limited number of climate adaptation strategies and research agendas. In 2024, WHO and UNICEF released a joint review identifying new indicators to enhance national and global monitoring of climate-resilient WASH, including monitoring of hygiene-related infrastructure and behavioural elements [57,58]. Similarly, guidance on climate-resilient WASH from UNICEF acknowledges the need to change behaviours as well as address infrastructure [59]. In Europe, there are new frameworks assessing the emerging climate-related risks to food safety, including fungal toxins and seafood contamination, and identifying vulnerabilities in the microbiological safety of food under scenarios of extreme weather, supply chain disruption and changing production practice [60]. Meanwhile, WHO’s hand hygiene research agenda for 2023–2030 and related initiatives mention the potential of behaviour change to enhance hygiene under climate stress in both domestic and institutional settings [61–63].

Understanding the interplay between climate hazards, hygiene practices, and health outcomes is challenging due to the complex, multi-sectoral, and context-specific pathways involved. Factors such as social norms, poor infrastructure resilience, service delivery models, and the lack of prioritisation of adaptation undermine action. This highlights why dedicated research is urgently needed to move beyond acknowledging the problem to identifying specific, evidence-based priorities for action.

This study sought to identify consensus-based research priorities at the intersection of climate change, hygiene, health, and well-being. By systematically identifying and ranking key research gaps through global expert engagement, the aim is to guide future research investments, inform policy and support programming that is responsive to the climate-driven hygiene challenges faced by diverse communities. These priorities are intended to ensure that research efforts align with the needs articulated by national and local practitioners, policymakers and researchers working across disciplines and sectors.

Methods

Step 1. Question identification

The scope of the research questions and research prioritisation exercise was agreed upon by the study team at the outset (Table 1).

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Table 1. Scope of the research prioritisation exercise.

https://doi.org/10.1371/journal.pclm.0000907.t001

An initial set of potential questions was identified through a rapid scoping review and key informant interviews. Full details on these methods are provided in Tables A and B in S1 Appendix. A total of 116 peer-reviewed manuscripts and 55 key informant interviews formed this initial dataset. The study team reviewed manuscripts and interview transcripts and extracted relevant research questions related to any combination of the intersection of climate change, hygiene, health, and well-being.

The study team screened, de-duplicated and refined questions to ensure relevance to study aims. Questions were organised to address climate impact drivers and specific climate hazards following the Intergovernmental Panel on Climate Change (IPCC) framework. Climate impact drivers include changing precipitation patterns, prolonged dry spells or intensified rainfall, sea level rise, which contributes to inundation, coastal change, and increased salinisation, rising average temperatures, reduced soil moisture, and increased atmospheric humidity. Climate-related hazards are specific weather or climate events, and include hydrometeorological hazards (floods, tropical cyclones, heavy rainfall events); temperature extremes (heatwaves and cold waves), and compound events, like concurrent drought (meteorological and hydrological) [65–67].

We further organised the research questions by three broad hygiene domains [68,69], drawing on definitions of behaviour from the Capability, Opportunity and Motivation Behaviour (COM-B) model [70]. We defined personal hygiene as behaviours focused on maintaining the cleanliness of the body to support health and well-being. Examples include bathing, handwashing, toilet use, menstrual hygiene, hygiene material access, and incontinence care. We defined domestic hygiene as behaviours that clean and sanitise the household and peri-domestic environment. Examples include washing clothes and bedding; cleaning the toilet, floor, and surfaces; water storage practices; domestic animal, livestock, and vector habitat management; post-flood cleaning; and managing solid waste. We defined food hygiene as behaviours related to safe food handling. This includes food storage, food preparation and washing, cross-contamination prevention in the home, and ensuring food safety from preparation to consumption.

Results

A total of 141 people from 46 countries completed the online survey (Fig 1), representing a diverse cross-section of stakeholders, including academic institutions, international and local non-governmental organisations (NGOs), multilateral agencies, and government bodies, and reflecting a broad set of geographic and disciplinary perspectives (Tables B and C in S2 Appendix).

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Fig 1. Geographic distribution of survey respondents.

https://doi.org/10.1371/journal.pclm.0000907.g001

The top 20 highest-ranked research questions, shown in Table 2, achieved consistently high weighted RPS ranging from 75–100%, indicating high consensus on their importance. These questions spanned the hygiene domains and reflected a range of climate-impact drivers and hazards, including water scarcity, extreme weather events, and rising temperatures.

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Table 2. Top 20 research priorities on climate change, hygiene, and health.

https://doi.org/10.1371/journal.pclm.0000907.t002

The top-ranked questions revealed a clear emphasis on building the foundational evidence base at the intersection of climate change, hygiene, and health. A substantial majority (75%) of the top 20 questions focused on descriptive research, aiming to better characterise the burden of infectious diseases linked to climate-related hazards, understand existing hygiene practices and coping strategies, and identify barriers to maintaining safe hygiene under climate stress. Examples include exploring how household water scarcity, drought, and precipitation variability affect infectious disease burdens through impacts on hygiene behaviours (Q2, Q3, Q9, Q15) and assessing how extreme weather events disrupt hygiene practices (Q14, Q18) or the capability of people with disabilities to maintain personal hygiene (Q8). Other descriptive questions addressed contamination pathways, such as the role of solid waste in spreading pathogens and pollutants during floods (Q5), and the determinants of hygiene behaviours in the context of extreme weather events (Q13, Q16, Q19).

One fifth (20%) of the top-ranked questions related to delivery, focusing on how to provide practical support measures and preparedness messaging to protect health during climate hazards. Examples included identifying effective hygiene promotion actions before or during extreme weather events (Q1, Q11), tailoring support for people with disabilities (Q6), and developing communication strategies to promote safe hygiene during higher temperatures (Q10) and extreme weather events (Q20). Only a single (5%) question fell under development, exploring how to adapt or refine existing hygiene interventions (Q7). This included assessing whether tailored approaches are needed for hygiene promotion in water-scarce or drought-prone settings.

Across the top 20, climate hazards were a dominant focus, appearing in 11 questions. Many sought to understand immediate disruptions from floods, cyclones, and other extreme weather events on hygiene behaviours; the cascading and long-term impacts from damaged infrastructure; and the impact of chronic service disruptions (Q5, Q11, Q16, Q19). Reduced rainfall and water availability emerged as the most prominent climate impact driver of interest, while there were relatively few prioritised questions focusing on high temperatures or heavy rainfall as direct hygiene-related health risks (Q2, Q7). However, some priorities addressed heat- and humidity-related effects, including their influence on water use for hygiene (Q10, Q17) and on pathogen dynamics across water, food, and domestic surfaces (Q4, Q12, Q20).

The rank order list of all 57 research questions and questions stratified by organisational affiliation or region of focus can be found in the S3 Appendix and S4 Appendix. These stratified rankings indicate some variation by organisation type and region, potentially reflecting differences in institutional roles, mandates, and contextual focus, and are presented in the supplementary material for further consideration by readers. All data, R code, and associated files required to replicate the findings of this study are publicly available on LSHTM Data Compass: https://datacompass.lshtm.ac.uk/id/eprint/5008/ (https://doi.org/10.17037/DATA.00005008).

Discussion

This work complements and strengthens other global initiatives to identify evidence needs on the links between climate and health. By explicitly focusing on hygiene, a domain often underrepresented in climate-health discussions, this exercise fills a critical gap and provides actionable priorities to guide investments and research strategies over the next decade. By applying a structured, consensus-driven CHNRI process, our study has identified these priorities through a transparent and credible process that relies on extensive engagement [72]. Taken together, this prioritisation provides a clear, stakeholder-informed roadmap for funders, researchers, and policymakers seeking to support the most critical research needs at this intersection [73]. By directing attention and resources to these priorities, the sector can build the evidence base needed to inform adaptive strategies, strengthen hygiene promotion, and safeguard health against the accelerating impacts of climate change.

The findings underline the importance of multidisciplinary and cross-sector collaboration [74]. Climate change, hygiene, and health are interlinked through complex pathways that span environmental systems, infrastructure, human behaviour, and social determinants. Addressing the identified research gaps will require integrating expertise across public health, water and sanitation service delivery, climate science, behavioural research, and policy. Such collaboration is essential to design resilient interventions that are both scientifically grounded and practically feasible, ensuring that adaptation efforts meaningfully protect population health in an increasingly unstable climate [75].

The strong leaning toward descriptive research underscores that the field remains at a stage where robust empirical data on exposure pathways, disease burdens, and behavioural responses are urgently needed [76,77]. This foundational understanding appears to be viewed by experts as essential before effective interventions and large-scale programmatic adjustments can be designed and tested. The relatively smaller number of delivery and development-focused questions suggests that while there is recognition of the need to adapt hygiene strategies to climate realities, there is still limited evidence to inform how best to operationalise these adaptations. However, the presence of high-ranking delivery questions, such as those on preparedness strategies and messaging during extreme weather, points to an emerging readiness to move toward implementation research in some areas [78].

Equity concerns were evident across the priorities. Several top-ranked questions explicitly addressed the compounded vulnerabilities faced by people with disabilities, women and girls managing menstrual hygiene, and communities confronting multiple overlapping climate hazards. This aligns with broader calls in climate and health research to centre the experiences of groups who disproportionately bear the impacts of climate change and to design interventions that do not exacerbate existing inequalities [37].

Consistent with patterns observed in other climate-health research agendas [49,50,53–55], our findings show a stronger priority given to climate-related hazards, such as extreme weather events, than on slow-onset changes such as chronic heat exposure or progressive water salinisation. In our prioritisation, 11 of the top 20 questions addressed the impacts of floods, cyclones, and storms on hygiene behaviours, infrastructure, and domestic environments. These events are highly visible, cause acute disruption, and frequently trigger disaster response, making them more salient to policymakers, the media, and the public than gradual climatic shifts [79]. Similarly, much of the climate–health evidence base focuses on water-related pathways (e.g., floods, droughts, water scarcity) because these have direct, well-recognised links to health outcomes and can be more readily measured and modelled than other drivers such as land degradation, biodiversity loss, or shifting disease ecologies [50,76]. Water insecurity was another dominant theme in our results, with reduced rainfall and drought highly ranked research priorities, often linked to changes in water use for hygiene and consequent impacts on disease burden. The less visible, slow-onset hazards and their long-term implications for hygiene, however, remain important, and our findings demonstrate the need to expand research and intervention portfolios to address the full spectrum of climate change-related risks.

The research questions that emerged from this process are necessarily broad and require further specification and contextualization before they are readily translated into research protocols. It is important to note that our research prioritisation process did not differentiate between research questions that reflect a lack of data or information around a specific topic and questions that reflect a lack of knowledge about a specific evidence base. For example, the links between climate hazards and infectious disease burden were the second-highest prioritised research question in our exercise. There are multiple reviews, both estimating climate-related infectious disease burden [80] and infectious disease transmission pathways related to climate change [81], but these studies may not explicitly include hygiene in their discussion of potential transmission pathways or prevention strategies. Addressing research questions related to climate, hygiene, and health will require structured engagement with existing scientific evidence to extract relevant insights and findings. Changing water use practices was our third highest-ranked research question. Multiple studies describe context-specific individual and household changes in water use and water prioritisation in the context of water scarcity [82–84], and the research gaps may reflect a lack of evidence synthesis. There is a wide range of evidence synthesis methods [85] that should be explored for their potential relevance to addressing the stated research priorities.

Conclusions

This research prioritisation exercise has identified critical knowledge gaps at the intersection of climate change, hygiene, and health, emphasising the urgent need for multi-sectoral action. The findings highlight the necessity of integrating hygiene promotion into climate preparedness, addressing water scarcity impacts on hygiene behaviours, and investigating climate-driven disease transmission pathways. Despite growing recognition of these links, hygiene remains underrepresented in climate change research and policy, underscoring the importance of targeted funding and interdisciplinary collaboration. Without a more comprehensive evidence base, effective public health strategies and climate adaptation efforts will be limited. Strengthening research collaboration across disciplines, geographies, and sectors is essential to ensuring that adaptations and climate change resilience efforts are evidence-based, context-specific, and equitable.

Supporting information

Acknowledgments

This research agenda was supported by six technical advisors:

• Akanksha Marphatia (London School of Hygiene & Tropical Medicine, UK)

• Belen Torondel-Lopez (London School of Hygiene & Tropical Medicine, UK)

• Julia Sobolik (London School of Hygiene & Tropical Medicine, UK)

• Karen Levy (University of Washington, USA)

• Kondwani Chidziwisano (Malawi University of Business and Applied Sciences (MUBAS), Malawi)

• Oliver Cumming (London School of Hygiene & Tropical Medicine, UK)

The study team would like to acknowledge and thank the survey respondents, interviewees, and all observers who provided time and feedback throughout this process, particularly in identifying, developing, and refining the research questions. Throughout the entire process, numerous experts provided their time and input to shape this research agenda.