Advancing One human-animal-environment Health for global health security: what does the evidence say?

In this Series paper, we review the contributions of One Health approaches (ie, at the human-animal-environment interface) to improve global health security across a range of health hazards and we summarise contemporary evidence of incremental benefits of a One Health approach. We assessed how One Health approaches were reported to the Food and Agricultural Organization of the UN, the World Organisation for Animal Health (WOAH, formerly OIE), and WHO, within the monitoring and assessment frameworks, including WHO International Health Regulations (2005) and WOAH Performance of Veterinary Services. We reviewed One Health theoretical foundations, methods, and case studies. Examples from joint health services and infrastructure, surveillance-response systems, surveillance of antimicrobial resistance, food safety and security, environmental hazards, water and sanitation, and zoonoses control clearly show incremental benefits of One Health approaches. One Health approaches appear to be most effective and sustainable in the prevention, preparedness, and early detection and investigation of evolving risks and hazards; the evidence base for their application is strongest in the control of endemic and neglected tropical diseases. For benefits to be maximised and extended, improved One Health operationalisation is needed by strengthening multisectoral coordination mechanisms at national, regional, and global levels.

Concept analysis of health system resilience.

BACKGROUND: There are several definitions of resilience in health systems, many of which share some characteristics, but no agreed-upon framework is universally accepted. Here, we review the concept of resilience, identifying its definitions, attributes, antecedents and consequences, and present the findings of a concept analysis of health system resilience. METHODS: We follow Schwarz-Barcott and Kim's hybrid model, which consists of three phases: theoretical, fieldwork and final analysis. We identified the concept definitions, attributes, antecedents and consequences of health system resilience and constructed an evidence-informed framework on the basis of the findings of this review. We searched PubMed, PsycINFO, CINAHL Complete, EBSCOhost-Academic Search and Premier databases and downloaded identified titles and abstracts on Covidence. We screened 3357 titles and removed duplicate and ineligible records; two reviewers then screened each title, and disagreements were resolved by discussion with the third reviewer. From the 130 eligible manuscripts, we identified the definitions, attributes, antecedents and consequences using a pre-defined data extraction form. RESULTS: Resilience antecedents are decentralization, available funds, investments and resources, staff environment and motivation, integration and networking and finally, diversification of staff. The attributes are the availability of resources and funds, adaptive capacity, transformative capacity, learning and advocacy and progressive leadership. The consequences of health system resilience are improved health system performance, a balanced governance structure, improved expenditure and financial management of health and maintenance of health services that support universal health coverage (UHC) throughout crises. CONCLUSION: A resilient health system maintains quality healthcare through times of crisis. During the coronavirus disease 2019 (COVID-19) epidemic, several seemingly robust health systems were strained under the increased demand, and services were disrupted. As such, elements of resilience should be integrated into the functions of a health system to ensure standardized and consistent service quality and delivery. We offer a systematic, evidence-informed method for identifying the attributes of health system resilience, intending to eventually be used to develop a measuring tool to evaluate a country's health system resilience performance.

Reviewing essential public health functions in the Eastern Mediterranean Region post COVID-19 pandemic: a foundation for system resilience.

The COVID-19 pandemic exposed vulnerabilities in many health systems worldwide with profound implications for health and society. The public health challenges experienced during the pandemic have highlighted the importance of resilient health systems, that can adapt and transform to meet the population's evolving health needs. Essential public health functions (EPHFs) offer a holistic, integrated and sustainable approach to public health by contributing to achieving several health priorities and goals. In recent years, there has been a focused effort to conceptualise and define the EPHFs. In this paper, we describe the collaborative approach undertaken by the WHO Eastern Mediterranean Region (EMR) and UK Health Security Agency and present the findings and results of the revised EPHFs, in view of lessons learnt from the COVID-19 pandemic and the current priorities for countries across the EMR. This included conducting a desktop review, a gap and bottleneck analysis and stakeholder consultation to arrive at the revised EPHF model including four enablers and nine core functions, including a new function: public health services. The EPHFs will offer countries a complementary and synergistic approach to strengthen health systems and public health capacities and contribute to the region's ability to effectively respond to future health challenges and emergencies. By focusing on the EPHFs, countries can work towards ensuring health security as an integral goal for the health system besides universal health coverage, thus strengthening and building more resilient and equitable health systems.

Multisectoral action towards sustainable development goal 3.d and building health systems resilience during and beyond COVID-19: Findings from an INTOSAI development initiative and World Health Organization collaboration.

This article is part of the Research Topic 'Health Systems Recovery in the Context of COVID-19 and Protracted Conflict'. As the world faces global health crises such as pandemics, epidemics, climate change and evolving disease burdens and population demographics, building strong and resilient public health systems is of critical importance. The need for an integrated approach to building health system resilience; the widening of inequalities; and fears of vulnerable populations being left behind are critical issues that require Supreme Audit Institutions (SAIs) enquiry as independent public oversight bodies. Each country has a Supreme Audit Institution with a remit to audit public funds as an effective, accountable, and inclusive institution. Government audits are key components of effective public financial management and Good Governance. SAIs contribute to the quality of government engagement and better state-society relations through their work. As SAIs provide independent external oversight and contribute to follow up and review of national targets linked to the Sustainable Development Goals (SDGs) in their respective countries, they can play an important role in national recovery efforts. WHO and INTOSAI Development Initiative (IDI) have been collaborating in facilitating SAIs' audits of strong and resilient national public health systems linked to the national target of SDG 3.d in 40 countries across Africa, Americas, Asia and Oceania between 2021 and 2022. This paper aims to convey key lessons learned from the joint multisectoral collaboration for facilitating the 3.d audits that can contribute to building health systems resilience in ongoing recovery efforts. The collaboration included facilitation of the audits through professional education and audit support using a health systems resilience framework. The 3.d audits are performance audits and follow IDI's SDG Audit Model (ISAM). Following the ISAM implies that the SAI should focus on a whole-of-government approach, policy coherence and integration, and assess both government efforts at 'leaving no one behind' and multi-stakeholder engagement in implementing the chosen national SDG target linked to 3.d. WHO's Health Systems Resilience team has supported IDI and SAIs by delivering training sessions and reviewing working papers and draft reports of the SAIs from a health systems resilience perspective. IDI has provided the technical expertise on performance audits through its technical team and through in-kind contributions from mentors from many SAIs in the regions participating in the audit. In the 3.d audit, SAIs can ask how governments are acting to enhance capacity in some or all of the following, depending on their own national context and risk: forecasting, preventing and preparing for public health emergencies (PHEs) and threatsadapting, absorbing and responding to PHEs and threatsmaintaining essential health services in all contexts (including during emergencies/crises). The audits are expected to highlight current capacities of health systems resilience; the extent to which a whole-of-government approach and policy coherence have been utilised; and government efforts related to multistakeholder engagement and leaving no one behind in building health systems resilience related to progressing towards achieving the national target linked to 3.d by 2030. An overall positive achievement noted was that undertaking a complex health audit in the middle of a pandemic is possible and can contribute to building health systems resilience and recovery efforts. In their review of audit plans, draft summaries, and other work by the SAIs, both WHO and IDI have observed that SAIs have used the training and supplementary materials and applied various parts of it in their audits. This collaboration also demonstrates key considerations needed for successful partnership across multisectoral partners at global, regional and national levels. Such considerations can be applied in different contexts, including socioeconomic and health system recovery, to ensure whole-of-society and whole-of-government action in building health systems resilience and monitoring and evaluation to maintain and accelerate progress towards the national target linked to SDG3.d, health security and universal health coverage (UHC), as well as broader socioeconomic development.

A novel approach to utilizing the essential public health functions in Ireland's health system recovery and reform.

This article is part of the Research Topic 'Health Systems Recovery in the Context of COVID-19 and Protracted Conflict.' The COVID-19 pandemic presented a challenge to health systems and exposed weaknesses in public health capacities globally. As Ireland looks to recovery, strengthening public health capacities to support health systems resilience has been identified as a priority. The Essential Public Health Functions (EPHFs) provide an integrated approach to health systems strengthening with allied sectors and their operationalization supports health systems and multi-sectoral engagement to meet population needs and anticipate evolving demands. The Health Systems Resilience team (World Health Organization, HQ) in collaboration with the Department of Health (Ireland) developed a novel approach to the assessment of the EPHFs in Ireland. The approach involved a strategic and focused review of the delivery and consideration of EPHFs in relation to policy and planning, infrastructure, service delivery, coordination and integration, monitoring and evaluation and learning. Informed by a literature review and key document search, key stakeholder mapping and key informant interviews, lessons learned from experience with COVID-19 nationally and internationally, strengths as well as potential areas of improvement to optimize delivery of EPHFs were identified. Mapping of the EPHFs in Ireland revealed that there is evidence of delivery of all 12 EPHFs to varying degrees; however a number of challenges were identified, as well as numerous strengths and opportunities. Recommendations to optimize the delivery of EPHFs in Ireland include to integrate and coordinate EPHFs, increase the visibility of the public health agenda, leverage existing mechanisms, recognize and develop the workforce, and address issues with the Health Information System. There is a public health reform process currently underway in Ireland, with some of these recommendations already being addressed. The findings of this process can help further inform and support the reform process. Given the current focus on strengthening public health capacities globally, the findings in Ireland have applicability and relevance in other WHO regions and member states for health systems recovery and building back better, fairer and more resilient health systems.

Corrigendum: A novel approach to utilizing the essential public health functions in Ireland's health system recovery and reform.

[This corrects the article DOI: 10.3389/fpubh.2023.1074356.].

Liberia health system's journey to long-term recovery and resilience post-Ebola: a case study of an exemplary multi-year collaboration.

This article is part of the Research Topic 'Health Systems Recovery in the Context of COVID-19 and Protracted Conflict' Liberia is one of the three countries worst hit by the 2014-2016 West Africa Ebola Virus disease (EVD) outbreak, during which it recorded over 10,000 cases, including health workers. Estimates suggest that the non-EVD morbidity and mortality resulting from the collapse of the health system exceeded the direct impact of EVD. Lessons from the outbreak were clear, not only for Liberia but also for the regional and global communities: that building health system resilience through an integrated approach is an investment in population health and wellbeing, as well as economic security and national development. It is therefore no surprise that Liberia made recovery and resilience a national priority from the time the outbreak waned in 2015. The recovery agenda provided the platform for stakeholders to work toward the restoration of the pre-outbreak baseline of health system functions while aiming to build a higher level of resilience, informed by lessons from the Ebola crises. Based on the co-authors' experiences of on-the-ground country-support work, this study sought to provide an overview of the Liberia Health Service Resilience project (2018-2023) funded by KOICA, and propose a set of recommendations for national authorities and donors, derived from the authors' perceptions of best practices and key challenges associated with the project. We used both quantitative and qualitative approaches to generate the data represented in this study by reviewing published and unpublished technical and operational documents, and datasets derived through situational and needs assessments and routine monitoring and evaluation activities. This project has contributed to the implementation of the Liberia Investment Plan for Building a Resilient Health System and the successful response to the COVID-19 outbreak in Liberia. Although limited in scope, the Health Service Resilience project has demonstrated that health system resilience could be operationalized by applying a catchment and integrated approach and encouraging multi-sectoral collaboration, partnership, local ownership, and promoting the Primary Health Care approach. Principles applied in this pilot could guide the operationalization of health system resilience efforts in other resource-limited settings similar to Liberia and beyond.

Developing technical support and strategic dialogue at the country level to achieve Primary Health Care-based health systems beyond the COVID-19 era.

This article is part of the Research Topic 'Health Systems Recovery in the Context of COVID-19 and Protracted Conflict'. Pursuing the objectives of the Declaration of Alma-Ata for Primary Health Care (PHC), the World Health Organization (WHO) and global health partners are supporting national authorities to improve governance to build resilient and integrated health systems, including recovery from public health stressors, through the long-term deployment of WHO country senior health policy advisers under the Universal Health Coverage Partnership (UHC Partnership). For over a decade, the UHC Partnership has progressively reinforced, via a flexible and bottom-up approach, the WHO's strategic and technical leadership on Universal Health Coverage, with more than 130 health policy advisers deployed in WHO Country and Regional Offices. This workforce has been described as a crucial asset by WHO Regional and Country Offices in the integration of health systems to enhance their resilience, enabling the WHO offices to strengthen their support of PHC and Universal Health Coverage to Ministries of Health and other national authorities as well as global health partners. Health policy advisers aim to build the technical capacities of national authorities, in order to lead health policy cycles and generate political commitment, evidence, and dialogue for policy-making processes, while creating synergies and harmonization between stakeholders. The policy dialogue at the country level has been instrumental in ensuring a whole-of-society and whole-of-government approach, beyond the health sector, through community engagement and multisectoral actions. Relying on the lessons learned during the 2014-2016 Ebola outbreak in West Africa and in fragile, conflict-affected, and vulnerable settings, health policy advisers played a key role during the COVID-19 pandemic to support countries in health systems response and early recovery. They brought together technical resources to contribute to the COVID-19 response and to ensure the continuity of essential health services, through a PHC approach in health emergencies. This policy and practice review, including from the following country experiences: Colombia, Islamic Republic of Iran, Lao PDR, South Sudan, Timor-Leste, and Ukraine, provides operational and inner perspectives on strategic and technical leadership provided by WHO to assist Member States in strengthening PHC and essential public health functions for resilient health systems. It aims to demonstrate and advise lessons and good practices for other countries in strengthening their health systems.

A synthesis of concepts of resilience to inform operationalization of health systems resilience in recovery from disruptive public health events including COVID-19.

This article is part of the Research Topic 'Health Systems Recovery in the Context of COVID-19 and Protracted Conflict' Health systems resilience has become a ubiquitous concept as countries respond to and recover from crises such as the COVID-19 pandemic, war and conflict, natural disasters, and economic stressors inter alia. However, the operational scope and definition of health systems resilience to inform health systems recovery and the building back better agenda have not been elaborated in the literature and discourse to date. When widely used terms and their operational definitions appear nebulous or are not consistently used, it can perpetuate misalignment between stakeholders and investments. This can hinder progress in integrated approaches such as strengthening primary health care (PHC) and the essential public health functions (EPHFs) in health and allied sectors as well as hinder progress toward key global objectives such as recovering and sustaining progress toward universal health coverage (UHC), health security, healthier populations, and the Sustainable Development Goals (SDGs). This paper represents a conceptual synthesis based on 45 documents drawn from peer-reviewed papers and gray literature sources and supplemented by unpublished data drawn from the extensive operational experience of the co-authors in the application of health systems resilience at country level. The results present a synthesis of global understanding of the concept of resilience in the context of health systems. We report on different aspects of health systems resilience and conclude by proposing a clear operational definition of health systems resilience that can be readily applied by different stakeholders to inform current global recovery and beyond.

Towards applying the essential public health functions for building health systems resilience: A renewed list and key enablers for operationalization.

The COVID-19 pandemic, climate change-related events, protracted conflicts, economic stressors and other health challenges, call for strong public health orientation and leadership in health system strengthening and policies. Applying the essential public health functions (EPHFs) represents a holistic operational approach to public health, which is considered to be an integrated, sustainable, and cost-effective means for supporting universal health coverage, health security and improved population health and wellbeing. As a core component of the Primary Health Care (PHC) Operational Framework, EPHFs also support the continuum of health services from health promotion and protection, disease prevention to treatment, rehabilitation, and palliative services. Comprehensive delivery of EPHFs through PHC-oriented health systems with multisectoral participation is therefore vital to meet population health needs, tackle public health threats and build resilience. In this perspective, we present a renewed EPHF list consisting of twelve functions as a reference to foster country-level operationalisation, based on available authoritative lists and global practices. EPHFs are presented as a conceptual bridge between prevailing siloed efforts in health systems and allied sectors. We also highlight key enablers to support effective implementation of EPHFs, including high-level political commitment, clear national structures for institutional stewardship on EPHFs, multisectoral accountability and systematic assessment. As countries seek to transform health systems in the context of recovery from COVID-19 and other public health emergencies, the renewed EPHF list and enablers can inform public health reform, PHC strengthening, and more integrated recovery efforts to build resilient health systems capable of managing complex health challenges for all people.

COVID-19 Preparedness and Response Plans from 106 countries: a review from a health systems resilience perspective.

Coronavirus disease (COVID-19) has exposed long-standing fragmentation in health systems strengthening efforts for health security and universal health coverage while these objectives are largely interdependent and complementary. In this prevailing background, we reviewed countries' COVID-19 Preparedness and Response Plans (CPRPs) to assess the extent of integration of non-COVID-19 essential health service continuity considerations alongside emergency response activities. We searched for COVID-19 planning documents from governments and ministries of health, World Health Organization (WHO) country offices and United Nations (UN) country teams. We developed document review protocols using global guidance from the WHO and UN and the health systems resilience literature. After screening, we analysed 154 CPRPs from 106 countries. The majority of plans had a high degree of alignment with pillars of emergency response such as surveillance (99%), laboratory systems (96%) and COVID-19-specific case management (97%). Less than half considered maintaining essential health services (47%); 41% designated a mechanism for health system-wide participation in emergency planning; 34% considered subnational service delivery; 95% contained infection prevention and control (IPC) activities and 29% considered quality of care; and 24% were budgeted for and 7% contained monitoring and evaluation of essential health services. To improve, ongoing and future emergency planning should proactively include proportionate activities, resources and monitoring for essential health services to reduce excess mortality and morbidity. Specifically, this entails strengthening subnational health services with local stakeholder engagement in planning; ensuring a dedicated focus in emergency operations structures to maintain health systems resilience for non-emergency health services; considering all domains of quality in health services along with IPC; and building resilient monitoring capacity for timely and reliable tracking of health systems functionality including service utilization and health outcomes. An integrated approach to planning should be pursued as health systems recover from COVID-19 disruptions and take actions to build back better.

On the resilience of health systems: A methodological exploration across countries in the WHO African Region.

The need for resilient health systems is recognized as important for the attainment of health outcomes, given the current shocks to health services. Resilience has been defined as the capacity to "prepare and effectively respond to crises; maintain core functions; and, informed by lessons learnt, reorganize if conditions require it". There is however a recognized dichotomy between its conceptualization in literature, and its application in practice. We propose two mutually reinforcing categories of resilience, representing resilience targeted at potentially known shocks, and the inherent health system resilience, needed to respond to unpredictable shock events. We determined capacities for each of these categories, and explored this methodological proposition by computing country-specific scores against each capacity, for the 47 Member States of the WHO African Region. We assessed face validity of the computed index, to ensure derived values were representative of the different elements of resilience, and were predictive of health outcomes, and computed bias-corrected non-parametric confidence intervals of the emergency preparedness and response (EPR) and inherent system resilience (ISR) sub-indices, as well as the overall resilience index, using 1000 bootstrap replicates. We also explored the internal consistency and scale reliability of the index, by calculating Cronbach alphas for the various proposed capacities and their corresponding attributes. We computed overall resilience to be 48.4 out of a possible 100 in the 47 assessed countries, with generally lower levels of ISR. For ISR, the capacities were weakest for transformation capacity, followed by mobilization of resources, awareness of own capacities, self-regulation and finally diversity of services respectively. This paper aims to contribute to the growing body of empirical evidence on health systems and service resilience, which is of great importance to the functionality and performance of health systems, particularly in the context of COVID-19. It provides a methodological reflection for monitoring health system resilience, revealing areas of improvement in the provision of essential health services during shock events, and builds a case for the need for mechanisms, at country level, that address both specific and non-specific shocks to the health system, ultimately for the attainment of improved health outcomes.

Building the evidence base for global health policy: the need to strengthen institutional networks, geographical representation and global collaboration.

National public health institutes and WHO collaborating centres, and their global networks, are a key resource to support public health system strengthening with essential public health functions and generate evidence for health policy central to national health and socioeconomic development. The COVID-19 pandemic has laid bare global inequities in public health capacities, made urgent the need to examine sources of global knowledge and understand how to better invest in and use public health institutes and their capacities. This analysis paper incorporates experiences and perspectives from the WHO and International Association of Public Health Associations including the ongoing pandemic and work conducted in the UK-WHO 'Tackling Deadly Diseases in Africa Programme'. We acknowledge geographical disparities in public health capacities both within and across countries and regions, provide examples of novel ways of working for global health actors, and define the challenging environment in which public health authorities operate. We identify four incentives for all countries to invest in public health and strengthen institutions: (1) transparency and trust; (2) socioeconomic dividends; (3) collective health protection and (4) knowledge sharing and equity. By pursuing shared priorities; enabling voices from low-resource settings to be more equitably heard; facilitating collaboration and learning within and across regions, we articulate actionable next steps to develop and better harness public health institutes and international networks.

The global pool of simulation exercise materials in health emergency preparedness and response: a scoping review with a health system perspective.

Simulation Exercises (SimEx) are an established tool in defence and allied security sectors, applied extensively in health security initiatives under national or international legislative requirements, particularly the International Health Regulations (2005). There is, however, a paucity of information on SimEx application to test the functionality of health systems alongside emergency preparedness, response and recovery. Given the important implications health services resilience has for the protection and improvement of human life, this scoping review was undertaken to determine how the publicly available body of existing global SimEx materials considers health systems, together with health security functions in the event of disruptive emergencies. The global review identified 668 articles from literature and 73 products from institutional sources. Relevant screening identified 51 materials suitable to examine from a health system lens using the six health system building blocks as per the WHO Health System Framework. Eight materials were identified for further examination of their ability to test health system functionality from a resilience perspective. SimEx are an effective approach used extensively within health security and emergency response sectors but is not yet adequately used to test health system resilience. Currently available SimEx materials lack an integrated health system perspective and have a limited focus on the quality of services delivered within the context of response to a public health emergency. The materials do not focus on the ability of systems to effectively maintain core services during response. Without adjustment of the scope and focus, currently available SimEx materials do not have the capacity to test health systems to support the development of resilient health systems. Dedicated SimEx materials are urgently needed to fill this gap and harness their potential as an operational tool to contribute to improvements in health systems. They can act as effective global goods to allow testing of different functional aspects of health systems and service delivery alongside emergency preparedness and response. The work was conducted within the scope of the Tackling Deadly Diseases in Africa Programme, funded by the UK Department for International Development, which seeks to strengthen collaboration between the health system and health security clusters to promote health security and build resilient health systems.

Developing a multisectoral National Action Plan for Health Security (NAPHS) to implement the International Health Regulations (IHR 2005) in Tanzania.

The Ebola outbreak in West Africa precipitated a renewed momentum to ensure global health security through the expedited and full implementation of the International Health Regulations (IHR) (2005) in all WHO member states. The updated IHR (2005) Monitoring and Evaluation Framework was shared with Member States in 2015 with one mandatory component, that is, States Parties annual reporting to the World Health Assembly (WHA) on compliance and three voluntary components: Joint External Evaluation (JEE), After Action Reviews and Simulation Exercises. In February 2016, Tanzania, was the first country globally to volunteer to do a JEE and the first to use the recommendations for priority actions from the JEE to develop a National Action Plan for Health Security (NAPHS) by February 2017. The JEE demonstrated that within the majority of the 47 indicators within the 19 technical areas, Tanzania had either 'limited capacity' or 'developed capacity'. None had 'sustainable capacity'. With JEE recommendations for priority actions, recommendations from other relevant assessments and complementary objectives, Tanzania developed the NAPHS through a nationwide consultative and participatory process. The 5-year cost estimate came out to approximately US$86.6 million (22 million for prevent, 50 million for detect, 4.8 million for respond and 9.2 million for other IHR hazards and points of entry). However, with the inclusion of vaccines for zoonotic diseases in animals increases the cost sevenfold. The importance of strong country ownership and committed leadership were identified as instrumental for the development of operationally focused NAPHS that are aligned with broader national plans across multiple sectors. Key lessons learnt by Tanzania can help guide and encourage other countries to translate their JEE priority actions into a realistic costed NAPHS for funding and implementation for IHR (2005).

The impact of PFOS on health in the general population: a review.

Perfluorooctane sulphonate (PFOS) is a persistent organic pollutant that is toxic, bioaccumulative and undergoes wide transportation across all environmental media. It has been widely detected in environmental samples but there is limited information about the health effects on humans from environmental exposure. This paper presents the findings of a review of the literature on the impact of PFOS on the health of the general population. Fifteen relevant epidemiological studies were identified that looked at the association between human PFOS exposure and a range of health related outcomes. Small but statistically significant associations have been reported with PFOS and total cholesterol, glucose metabolism, body mass index (BMI), thyroid function, infertility, breast feeding, uric acid and attention deficit/hyperactivity disorder (ADHD). The true significance of these findings is uncertain due to the inconsistencies in some of the study results and the limitations of the literature. The majority of studies were cross-sectional and considered surrogate markers of health (e.g. cholesterol levels). The available literature is also limited in ascertaining the link between PFOS concentrations in the environment, exposure pathways and health effects. We conclude that the current evidence is inconclusive and further large-scale prospective cohort studies would be useful to assess the association between environmental exposure to PFOS, appropriate biomarkers (e.g. serum levels of PFOS) and health outcomes.