The world has entered a new era of ‘water bankruptcy,’ U.N. report says
Researchers say this is not merely a temporary crisis, but a permanent failure that requires rethinking the world’s approach to water scarcity.
Iran’s Lake Urmia, once the largest lake in the Middle East, has dramatically shrunk due to prolonged drought, the damming of rivers feeding the lake, and extensive groundwater extraction in the surrounding area. (MORTEZA AMINOROAYAYI/Middle East Images/AFP via Getty Images)
Climate change, pollution and decades of overuse have pushed the world into a state of “water bankruptcy,” leaving essential sources of fresh water irreparably damaged and billions of people without enough water to meet their basic needs, United Nations experts declared on Tuesday.
In a sweeping report from United Nations University (UNU), the international agency’s research arm, scientists compared humanity to a person plunging into financial ruin. Not only does the world overspend its annual water “income” — the renewable flows that come from rain and snow — but it has also exhausted the long-term “savings” stored in underground aquifers, glaciers and ecosystems. At the same time, people are allowing pollution from human waste, agriculture and industrial operations to contaminate the dwindling fresh water that remains — like someone setting fire to the last few dollars in their wallet.
Signs of this emergency are alarming and abundant, said lead author Kaveh Madani, director of the UNU Institute for Water, Environment and Health. More than half of the world’s large lakes are shrinking. Roughly 70 percent of underground aquifers are in long-term decline. Large-scale droughts have become more frequent and pervasive, costing an average of $307 billion annually. Some 4.4 billion people face water scarcity for at least one month a year.
Madani and his colleagues argue that it’s not sufficient to refer to the situation as “water stress” or a “water crisis” — language often used by the U.N. and other international institutions — because the challenge will not go away anytime soon.
Human activities have already caused irreversible damage to many of the systems that generate, regulate and store fresh water, the report says. Rising temperatures, driven mostly by the burning of fossil fuels, have altered precipitation patterns and increased the rate of evaporation from landscapes. Deforestation and development have destroyed the ecosystems that filter and clean rainwater. Overextraction is causing the collapse of subterranean aquifers that store groundwater, reducing their capacity to become recharged. And melting mountain glaciers, which accumulated over centuries or millennia, will not grow back in a human lifetime.
“What appears on the surface as a crisis is, in fact, a new baseline,” the report authors write. “Some losses are now unavoidable, and the central task is to prevent further irreversible damage while reorganizing the system around a smaller hydrological budget.”
Existing policies are too narrowly focused on improving sanitation and drinking water and helping industries to become incrementally more efficient, the report says. Ahead of an upcoming United Nations water conference in the United Arab Emirates, it calls on leaders to declare a “global water bankruptcy” and adopt a new approach to managing the world’s dwindling supply of safe water. Otherwise, it warns, the world will slide deeper into a future of food shortages, disease outbreaks and water-fueled conflict.Ask The Post AIDive deeper
Madani, who was born in Tehran, became convinced of the need for a new approach to water management after watching a decades-old black-and-white video about shortages in the Iranian capital. The narrator referred to the situation as a “crisis” — the same language being used now to describe the multiyear drought that has threatened Tehran’s water supply and prompted President Masoud Pezeshkian to contemplate evacuating the city.
“How long can we call something like this crisis?” Madani said. “A crisis means a shock — it’s an anomaly that must be addressed urgently, but still you have hopes that the baseline can be restored.”
“I think it’s a big lie if you’re communicating to the public that this is a temporary situation,” he added. What Iran — and the world — are truly facing is “a postcrisis situation of failure.”
The water shortages in Iran — which experts have linked to human-caused climate change as well as surging demand and mismanagement of limited resources — have led to rationing, power cuts and increased food prices. The economic strain helped fuel the mass protest movement currently gripping the country, which in turn has prompted a brutal crackdown by government forces.
These issues increasingly affect countries of all sizes and income levels, said Melissa Scanlan, an environmental law expert and director of the Center for Water Policy at the University of Wisconsin at Milwaukee, who did not contribute to the report.
Major urban areas — from Cape Town, South Africa to Chennai, India to Mexico City — have teetered on the brink of “day zero” events, when water supplies fall so low that millions of people’s taps run dry. Pervasive droughts have caused spikes in the prices of foods such as Mediterranean olive oil and California vegetables, while saltwater contamination from rising seas has caused billions of dollars in damage to rice paddies and fruit farms in Vietnam. Large hydropower dams from Zambia to Nevada have seen reservoir levels fall so low they lose their ability to produce electricity. And some places have pumped so much water from their aquifers that their land is sinking — damaging infrastructure and making these areas more vulnerable to floods.Ask The Post AIDive deeper
“The global scope of the report is useful in showing repeat patterns,” Scanlan said. “It’s not just the Southern Hemisphere, it’s not just the Middle East. There is something larger at play in terms of how we’re treating water across the world.”
The report also shows how water problems are already wreaking economic and political havoc. Western U.S. states are locked in a years-long battle over the dwindling Colorado River. Egypt, Sudan and Ethiopia are at odds over a massive new dam on a major tributary of the Nile. Research shows that undocumented migration from Mexico to the United States increases amid warming-fueled droughts.
“Lack of water means lack of food,” Madani said. “It means famine, unemployment, chaos, revolution.”
A lot of this geopolitical turmoil comes down to what Madani calls a “mismatch between water availability and water consumption.” The laws, contracts and treaties that govern water use — such as the century-old compact determining allocation of the Colorado River — were based on a climate that no longer exists, she said. Farmers, cities and industrial water users trade blame over who is taking more than their fair share, without acknowledging that the overall pie has shrunk. Typical measures to address shortfalls, such as drilling deeper wells or diverting more water from rivers, can end up making the problem worse.
Much the way a company filing Chapter 11 bankruptcy must restructure operations, renegotiate contracts and create a new plan to pay debts, the world should reassess how much water is actually available and prioritize among competing claims, the U.N. report says. In some cases, that might involve limiting new development in water-stressed cities or restricting the growth of water-intensive industries. World leaders must also protect the forests, wetlands and other ecosystems that pay a crucial role in Earth’s water cycle.
The biggest challenges — and the biggest opportunity for change — lie in the agriculture sector, which accounts for 70 percent of humanity’s water usage, said Rabi Mohtar, a hydrologist who leads the Water-Energy-Food Nexus Research Group at Texas A&M University.
Governments may need to impose restrictions on irrigation and groundwater pumping or require farmers to shift to less-thirsty crops, he said. They should also implement regulations to prevent pesticides, fertilizers and other forms of agricultural runoff from polluting the shrinking water supply.
Mohtar, who was not involved in the U.N. report, expressed skepticism about the rhetorical value of declaring “water bankruptcy.” He worried that the terminology might discourage people from taking action, because it sends the message that humanity has already failed.
But he agreed with the basic premise that people have drastically exceeded the planet’s capacity to produce clean, fresh water.
“The time when we have abundance is over,” Mohtar said. “I would like to see accountability to every single drop.”
Rethinking the world’s approach to managing water will have far-reaching economic and social consequences, the U.N. report acknowledges. Arid nations might need to import food rather than trying to grow it themselves. Farmers in areas that can no longer support agriculture may need to pursue other livelihoods. If changes aren’t implemented in a manner that is equitable and inclusive, the report said, the world’s poorest and most vulnerable people will inevitably suffer the most.
Yet Madani emphasized that addressing the world’s water challenges will yield “co-benefits” in other areas. Restoring wetlands can help reduce dust storms, improving air quality and public health. Techniques to boost farmland’s ability to retain water also helps the soils absorb more carbon.
“In a fragmented world, water might be an excuse for bringing people together,” he said.
The world has entered an era of “global water bankruptcy” that is harming billions of people, a UN report has declared.
The overuse and pollution of water must be tackled urgently, the report’s lead author said, because no one knew when the whole system could collapse, with implications for peace and social cohesion.
All life depends on water but the report found many societies had long been using water faster than it could be replenished annually in rivers and soils, as well as over-exploiting or destroying long-term stores of water in aquifers and wetlands.
This had led to water bankruptcy, the report said, with many human water systems past the point at which they could be restored to former levels. The climate crisis was exacerbating the problem by melting glaciers, which store water, and causing whiplashes between extremely dry and wet weather.
Prof Kaveh Madani, who led the report, said while not every basin and country was water bankrupt, the world was interconnected by trade and migration, and enough critical systems had crossed this threshold to fundamentally alter global water risk.
The result was a world in which 75% of people lived in countries classified as water-insecure or critically water-insecure and 2 billion people lived on ground that is sinking as groundwater aquifers collapse.
Conflicts over water had risen sharply since 2010, the report said, while major rivers, such as the Colorado, in the US, and the Murray-Darling system, in Australia, were failing to reach the sea, and “day zero” emergencies – when cities run out of water, such as in Chennai, India – were escalating. Half of the world’s large lakes had shrunk since the early 1990s, the report noted. Even damp nations, such as the UK, were at risk because of reliance on imports of water-dependent food and other products.
“This report tells an uncomfortable truth: many critical water systems are already bankrupt,” said Madani, of the UN University’s Institute for Water, Environment and Health. “It’s extremely urgent [because] no one knows exactly when the whole system would collapse.”
About 70% of fresh water taken by human withdrawals was used for agriculture, but Madani said: “Millions of farmers are trying to grow more food from shrinking, polluted or disappearing water sources. Water bankruptcy in India or Pakistan, for example, also means an impact on rice exports to a lot of places around the world.” More than half of global food was grown in areas where water storage was declining or unstable, the report said.
Madani said action to deal with water bankruptcy offered a chance to bring countries together in an increasingly fragmented world. “Water is a strategic, untapped opportunity to the world to create unity within and between nations. It is one of the very rare topics that left and right and north and south all agree on its importance.”https://interactive.guim.co.uk/datawrapper/embed/rksLJ/1/?dark=false
The UN report, which is based on a forthcoming paper in the peer-reviewed journal Water Resources Management, sets out how population growth, urbanisation and economic growth have increased water demand for agriculture, industry, energy and cities. “These pressures have produced a global pattern that is now unmistakable,” it said.
In some of the world’s most densely populated river basins, including the Indus, Yellow, and Tigris-Euphrates, the rivers were periodically drying up before reaching the ocean. “In many basins, the ‘normal’ to which crisis managers once hoped to return has effectively vanished,” the report said. Lakes were also shrinking, from Lake Urmia, in Iran, to the Salton Sea, in the US, and Lake Chad. Wildlife suffered as well as people, as humans “steal” water from nature, Madani said
The over-exploitation of groundwater was causing cities to subside around the world, with Rafsanjan, in Iran, sinking by 30cm a year; Tulare, in the US, by about 28cm a year, and Mexico City by about 21cm a year. Jakarta, Manila, Lagos and Kabul were other major cities affected. Among the most visible signs of this water bankruptcy, the report said, were the 700 sinkholes peppering the heavily farmed Konya plain in Turkey.
Cities, such as Tehran, Cape Town, São Paulo and Chennai, had all faced day zero water crises, the report noted, while the number of water-related conflicts around the world had risen from 20 in 2010 to more than 400 in 2024.skip past newsletter promotion
Humanity was also slashing the amount of water available by destroying natural stores, such as wetlands, and polluting waterways. Wetlands equal in size to the entire European Union had been erased in the past five decades, the report said.
The report calls for a fundamental reset of how water is protected and used around the world. This would include cutting the rights and claims to withdraw water to match today’s degraded supply, and transforming water-intensive sectors, such as agriculture and industry, via changes in crops, more efficient irrigation and less wasteful urban systems. The report emphasises support for communities whose livelihoods must change.
“Water bankruptcy management requires honesty, courage and political will,” said Madani. “We cannot rebuild vanished glaciers or reinflate acutely compacted aquifers. But we can prevent further losses, and redesign institutions to live within new hydrological limits.”
Tshilidzi Marwala, UN undersecretary general, said: “Water bankruptcy is becoming a driver of fragility, displacement and conflict. Managing it fairly is now central to maintaining peace, stability and social cohesion.”
The challenge of sustainable water management around the world was very real, said Prof Albert Van Dijk, at the Australian National University who was not part of the UN report, although, he added, he preferred the description of collapse, or systemic failure, over bankruptcy.
A recent water report led by Van Dijk highlighted the increasingly erratic climate. “Increased variability is as much a problem as scarcity,” he said. “Sometimes there’s more water available overall, but it increasingly arrives in bursts, at the wrong place and at the wrong time. This makes management genuinely harder. For example, dam reservoir levels need to be kept low to mitigate floods but high to ensure supply during droughts.”
Dr Jonathan Paul, at Royal Holloway, University of London, said: “The report lays bare humankind’s mistreatment of water [which] threatens the viability of ‘the water cycle’ as a concept.
“The elephant in the room, which is mentioned explicitly only once, is the role of massive and unequal population growth in driving so many of the manifestations of water bankruptcy,” he said. “Addressing this growth would be more useful than tinkering with outdated, non-inclusive, and top-down water resource management frameworks.”
image: Cover of the Global Water Bankruptcy Report (UNU)view more Credit: UNU-INWEH and Pyae Phyo Aung
UN Headquarters, New York – Amid chronic groundwater depletion, water overallocation, land and soil degradation, deforestation, and pollution, all compounded by global heating, a UN report today declared the dawn of an era of global water bankruptcy, inviting world leaders to facilitate “honest, science-based adaptation to a new reality.”
“Global Water Bankruptcy: Living Beyond Our Hydrological Means in the Post-Crisis Era,” argues that the familiar terms “water stressed” and “water crisis” fail to reflect today’s reality in many places: a post-crisis condition marked by irreversible losses of natural water capital and an inability to bounce back to historic baselines.
“This report tells an uncomfortable truth: many regions are living beyond their hydrological means, and many critical water systems are already bankrupt,” says lead author Kaveh Madani, Director of the UN University’s Institute for Water, Environment and Health (UNU-INWEH), known as ‘The UN’s Think Tank on Water.’
Expressed in financial terms, the report says many societies have not only overspent their annual renewable water “income” from rivers, soils, and snowpack, they have depleted long-term “savings” in aquifers, glaciers, wetlands, and other natural reservoirs.
This has resulted in a growing list of compacted aquifers, subsided land in deltas and coastal cities, vanished lakes and wetlands, and irreversibly lost biodiversity.
The UNU report is based on a peer-reviewed paper in the journal of Water Resources Management that formally defines water bankruptcy as
1) persistent over-withdrawal from surface and groundwater relative to renewable inflows and safe levels of depletion; and
2) the resulting irreversible or prohibitively costly loss of water-related natural capital.
By contrast:
“Water stress” reflects high pressure that remains reversible
“Water crisis” describes acute shocks that can be overcome
The report is issued prior to a high-level meeting in Dakar, Senegal (26–27 Jan.) to prepare the 2026 UN Water Conference, to be co-hosted by the United Arab Emirates and Senegal 2-4 Dec. in the UAE.
While not every basin and country is water-bankrupt, Madani says, “enough critical systems around the world have crossed these thresholds. These systems are interconnected through trade, migration, climate feedbacks, and geopolitical dependencies, so the global risk landscape is now fundamentally altered.”
Madani underlines the following four essential points:
Water cannot be protected if we allow the hydrological cycle, the climate, and the underlying natural capital that produces water to be interrupted or damaged. The world has an important and still largely untapped strategic opportunity to act.
Water is an issue that crosses traditional political boundaries. It belongs to north and south, and to left and right. For that reason, it can serve as a bridge to create trust and unity between and within nations. In the fragmented world we live in, water can become a powerful focus for cooperation and for aligning national security with international priorities.
Investment in water is also investment in mitigating climate change, biodiversity loss, and desertification. Water should not be treated only as a downstream sector affected by other environmental crises. On the contrary, targeted investment in water can address the immediate concerns of communities and nations while also advancing the objectives of the Rio Conventions (climate, biodiversity, desertification).
A renewed global emphasis on water could help reaccelerate stalled negotiations and potentially reenergize halted international processes. A practical and cooperative focus on water offers a way to connect urgent local needs with long-term global goals.
Hotspots
In the Middle East and North Africa region, high water stress, climate vulnerability, low agricultural productivity, energy-intensive desalination, and sand and dust storms intersect with complex political economies;
In parts of South Asia, groundwater-dependent agriculture and urbanization have produced chronic declines in water tables and local subsidence; and
In the American Southwest, the Colorado River and its reservoirs have become symbols of over-promised water.
A world in the red
Drawing on global datasets and recent scientific evidence, the report presents a stark statistical overview of trends, the overwhelming majority caused by humans:
50%: Large lakes worldwide that have lost water since the early 1990s (with 25% of humanity directly dependent on those lakes)
50%: Global domestic water now derived from groundwater
40%+: Irrigation water drawn from aquifers being steadily drained
70%: Major aquifers showing long-term decline
410 million hectares: Area ofnatural wetlands – almost equal in size to the entire European Union – erased in the past five decades
30%+: Global glacier mass lost since 1970, with entire low- and mid-latitude mountain ranges expected to lose functional glaciers altogether within decades
Dozens: Major rivers that now fail to reach the sea for parts of the year
50+ years: How long many river basins and aquifers have been overdrawing their accounts
100 million hectares: Cropland damaged by salinization alone
And the human consequences:
75%: Humanity in countries classified as water-insecure or critically water-insecure
2 billion: People living on sinking ground.
25 cm: Annual drop being experienced by some cities
4 billion: People facing severe water scarcity at least one month every year
170 million hectares: Irrigated cropland under high or very high water stress – equivalent to the areas of France, Spain, Germany, and Italy combined
US$5.1 trillion: Annual value of lost wetland ecosystem services
3 billion: People living in areas where total water storage is declining or unstable, with 50%+ of global food produced in those same stressed regions.
1.8 billion: People living under drought conditions in 2022–2023
US$307 billion: Current annual global cost of drought
2.2 billion: People who lack safely managed drinking water, while 3.5 billion lack safely managed sanitation
Says Madani: “Millions of farmers are trying to grow more food from shrinking, polluted, or disappearing water sources. Without rapid transitions toward water-smart agriculture, water bankruptcy will spread rapidly.”
A new diagnosis for a new era
A region can be flooded one year and still be water bankrupt, he adds, if long-term withdrawals exceed replenishment. In that sense, water bankruptcy is not about how wet or dry a place looks, but about balance, accounting, and sustainability.
Says Madani: As with global climate change or pandemics, a declaration of global water bankruptcy does not imply uniform impact everywhere, but that enough systems across regions and income levels have become insolvent and crossed irreversible thresholds to constitute a planetary-scale condition.
“Water bankruptcy is also global because its consequences travel,” Madani explains. “Agriculture accounts for the vast majority of freshwater use, and food systems are tightly interconnected through trade and prices. When water scarcity undermines farming in one region, the effects ripple through global markets, political stability, and food security elsewhere. This makes water bankruptcy not a series of isolated local crises, but a shared global risk that demands a new type of response: Bankruptcy management, not crisis management.”
A call to reset the global water agenda
The report warns that the current global water agenda – largely focused on drinking water, sanitation, and incremental efficiency improvements – is no longer fit for purpose in many places and calls for a new global water agenda that:
Formally recognizes the state of water bankruptcy
Recognizes water as both a constraint and an opportunity for meeting climate, biodiversity, and land commitments
Elevates water issues in climate, biodiversity, and desertification negotiations, development finance, and peacebuilding processes.
Embeds water-bankruptcy monitoring in global frameworks, using Earth observation, AI, and integrated modelling
Uses water as a catalyst to accelerate cooperation between the UN Member States
In practical terms, managing water bankruptcy requires governments to focus on the following priorities:
Prevent further irreversible damage such as wetland loss, destructive groundwater depletion, and uncontrolled pollution
Rebalance rights, claims, and expectations to match degraded carrying capacity
Support just transitions for communities whose livelihoods must change
Transform water-intensive sectors, including agriculture and industry, through crop shifts, irrigation reforms, and more efficient urban systems
Build institutions for continuous adaptation, with monitoring systems linked to threshold-based management
The report underlines that water bankruptcy is not merely a hydrological problem, but a justice issue with deep social and political implications requiring attention at the highest levels of government and multilateral cooperation. The burdens fall disproportionately on smallholder farmers, Indigenous Peoples, low-income urban residents, women and youth while the benefits of overuse often accrued to more powerful actors.
“Water bankruptcy is becoming a driver of fragility, displacement, and conflict,” says UN Under-Secretary-General Tshilidzi Marwala, Rector of UNU. “Managing it fairly – ensuring that vulnerable communities are protected and that unavoidable losses are shared equitably – is now central to maintaining peace, stability, and social cohesion.”
“Bankruptcy management requires honesty, courage, and political will,” Madani adds. “We cannot rebuild vanished glaciers or reinflate acutely compacted aquifers. But we can prevent further loss of our remaining natural capital, and redesign institutions to live within new hydrological limits.”
Upcoming milestones — the 2026 and 2028 UN Water Conferences, the end of the Water Action Decade in 2028, and the 2030 SDG deadline, for example — provide critical opportunities to implement this shift, he says.
“Despite its warnings, the report is not a statement of hopelessness,” adds Madani. “It is a call for honesty, realism, and transformation. Declaring bankruptcy is not about giving up — it is about starting fresh. By acknowledging the reality of water bankruptcy, we can finally make the hard choices that will protect people, economies, and ecosystems. The longer we delay, the deeper the deficit grows.”
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Report in brief
Media highlights
This report declares that the world has already entered the era of Global Water Bankruptcy. The condition is not a distant threat but a present reality. Many human water systems are now in a post-crisis failure state where past baselines can no longer be restored.
Global Water Bankruptcy is defined as a persistent post-crisis state of failure. In this state, long-term water use and pollution have exceeded renewable inflows and safe depletion limits. Key parts of the water system can no longer realistically be brought back to previous levels of supply and ecosystem function.
Terms such as water stress and water crisis are no longer sufficient descriptions of the world’s new water realities. Many rivers, lakes, aquifers, wetlands, and glaciers have been pushed beyond tipping points and cannot bounce back to past baselines. The language of temporary crisis is no longer accurate in many regions.
The global water cycle has moved beyond its safe planetary boundary. Together with climate, biodiversity, and land systems, freshwater has been pushed outside its safe operating space. The report concludes that the world is living beyond its hydrological means.
Billions of people are living with chronic water insecurity. Around 2.2 billion people still lack safely managed drinking water, 3.5 billion lack safely managed sanitation, and nearly 4 billion face severe water scarcity for at least one month each year. Almost three-quarters of the world’s population live in countries classified as water insecure or critically water insecure.
Surface waters and wetlands are shrinking on a massive scale. More than half of the world’s large lakes have lost water since the early 1990s, affecting about one-quarter of the global population that relies on them directly. Over the last five decades, humanity has lost roughly 410 million hectares of natural wetlands, almost the land area of the European Union. This includes about 177 million hectares of inland marshes and swamps, roughly the size of Libya or seven times the area of the United Kingdom. The loss of ecosystem services from these wetlands is valued at over US$5.1 trillion, similar to the combined GDP of around 135 of the world’s poorest countries.
Groundwater depletion and land subsidence show that hidden reserves are being exhausted. Around 70 percent of the world’s major aquifers show long-term declines. Land subsidence linked to groundwater over-pumping now affects more than 6 million square kilometers, almost 5 percent of the global land area, and nearly 2 billion people. This permanently reduces storage and increases flood risk in many cities, deltas, and coastal zones.
Water quality degradation further reduces usable water and accelerates bankruptcy. Growing loads of untreated wastewater, agricultural runoff, industrial pollution, and salinization are degrading rivers, lakes, and aquifers. Even where volumes appear sufficient on paper, the fraction of water that is safe for drinking, irrigation, and ecosystems continues to shrink.
The cryosphere is melting, eroding a critical long-term water buffer. The world has already lost more than 30 percent of its glacier mass since 1970. Some mountain ranges risk losing functional glaciers within decades, undermining water security for hundreds of millions of people who depend on rivers fed by glacier and snowmelt.
Farmers and food systems sit at the very heart of Global Water Bankruptcy. Roughly 70 percent of global freshwater withdrawals are used for agriculture, much of it in the Global South. Groundwater provides about 50 percent of domestic water use and over 40 percent of irrigation water worldwide. Both drinking water and food production now depend heavily on aquifers that are being depleted faster than they can realistically recharge.
Global food production is increasingly exposed to water decline and degradation. About 3 billion people and more than half of global food production are concentrated in areas where total water storage is already declining or unstable. More than 170 million hectares of irrigated cropland, about the combined land area of France, Spain, Germany, and Italy, are under high or very high water stress. Salinization has degraded roughly 82 million hectares of rainfed cropland and 24 million hectares of irrigated cropland, eroding yields in key global breadbaskets.
Drought impacts are becoming steadily more human-made and extremely costly. The report identifies a growing pattern of anthropogenic drought, meaning water deficits caused by overuse and degradation rather than natural variability alone. These impacts already cost around US$307 billion per year, more than the annual GDP of almost three-quarters of United Nations Member States.
Global Water Bankruptcy is also a justice, security, and political economy challenge. Without a deliberate commitment to equity, the costs of adjustment will fall disproportionately on farmers, rural communities, Indigenous Peoples, informal urban residents, women, youth, and other vulnerable groups. This imbalance increases the risk of social unrest and conflict in many regions.
Governments need to urgently shift from crisis management to bankruptcy management. The report calls for an end to short-term emergency thinking. Instead, it urges strategies that prevent further irreversible damage, reduce and reallocate demand, transform water-intensive sectors, tackle illegal withdrawals and pollution, and ensure just transitions for people whose livelihoods must change.
The current global water agenda is no longer fit for the Anthropocene. A narrow focus on drinking water, sanitation, and small efficiency gains will not be sufficient to resolve escalating water risks. In fact, that limited approach will increasingly compromise progress on climate action, biodiversity protection, land management, food security, and peace.
Water can be a bridge in a fragmented world. Every country, sector, and community depends on freshwater. Investing in water bankruptcy management therefore becomes an investment in climate stability, biodiversity protection, land restoration, food security, employment, and social harmony. This shared reliance offers practical common ground for cooperation between North and South and across political divides within nations.
World leaders are urged to use upcoming UN water milestones as decisive turning points. The report calls on governments and the UN system to use the 2026 and 2028 UN Water Conferences, the conclusion of the Water Action Decade in 2028, and the 2030 Sustainable Development Goal deadline to reset the global water agenda. It urges formal recognition of Global Water Bankruptcy, stronger monitoring and diagnostics, and a renewed effort to position water as a bridge for peace, climate action, biodiversity protection, and food security in an increasingly fragmented world.
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Key Policy Messages
The world is already in the state of “water bankruptcy”. In many basins and aquifers, long-term overuse and degradation mean that past hydrological and ecological baselines cannot realistically be restored. While not every basin or country is water-bankrupt, enough critical systems around the world have crossed these thresholds, and are interconnected through trade, migration, climate feedbacks, and geopolitical dependencies, that the global risk landscape is now fundamentally altered.
The familiar language of “water stress” and “water crisis” is no longer adequate. Stress describes high pressure that is still reversible. Crisis describes acute, time-bound shocks. Water bankruptcy must be recognized as a distinct post-crisis state, where accumulated damage and overshoot have undermined the system’s capacity to recover.
Water bankruptcy management must address insolvency and irreversibility. Unlike financial bankruptcy management, which deals only with insolvency, managing water bankruptcy is concerned with rebalancing demand and supply under conditions where returning to baseline conditions is no longer possible.
Anthropogenic drought is central to the world’s new water reality. Drought and water shortage are increasingly driven by human activities, over-allocation, groundwater depletion, land and soil degradation, deforestation, pollution, and climate change, rather than natural variability alone. Water bankruptcy is the outcome of long-term anthropogenic drought, not just bad luck with hydrological anomalies.
Water bankruptcy is about both quantity and quality. Declining stocks, polluted rivers, and degrading aquifers, and salinized soils mean that the truly usable fraction of available water is shrinking, even where total volumes may appear stable.
Managing water bankruptcy requires a shift from crisis management to bankruptcy management. The priority is no longer to “get back to normal”, but to prevent further irreversible damage, rebalance rights and claims within degraded carrying capacities, transform water-intensive sectors and development models, and support just transitions for those most affected.
Governance institutions must protect both water and its underlying natural capital. The existing institutions focus on protecting water as a good or service disregarding the natural capital that makes water available in the first place. Efforts to protect a product are ineffective when the processes that produce it are disrupted. Recognizing water bankruptcy calls for developing legal and governance institutions that can effectively protect not only water but also the hydrological cycle and natural capital that make its production possible.
Water bankruptcy is a justice and security issue. The costs of overshoot and irreversibility fall disproportionately on smallholder farmers, rural and Indigenous communities, informal urban residents, women, youth, and downstream users, while benefits have often accrued to more powerful actors. How societies manage water bankruptcy will shape social cohesion, political stability, and peace.
Water bankruptcy management combines mitigation with adaptation. While water crisis management paradigms seek to return the system to normal conditions through mitigation efforts only, water bankruptcy management focuses on restoring what is possible and preventing further damages through mitigation combined with adaptation to new normals and constraints.
Water can serve as a bridge in a fragmented world. Water can align national priorities with international priorities and improve cooperation between and within nations. Roughly 70% of global freshwater withdrawals are used for agriculture, much of it by farmers in the Global South. Elevating water in global policy debates can help rebuild trust between South and North but also within nations, between rural and urban, left and right constituencies.
Water must be recognized as an upstream sector. Most national and international policy agendas treat water as a downstream impact sector where investments are focused on mitigating the imposed problems and externalities. The world must recognize water as an upstream opportunity sector where investments have long-term benefits for peace, stability, security, equity, economy, health, and the environment.
Water is an effective medium to fulfill the global environmental agenda. Investments in addressing water bankruptcy deliver major co-benefits for the global efforts to address its environmental problems while addressing the national security concerns of the UN member states. Elevating water in the global policy agenda can renew international cooperation, increase the efficiency of environmental investments, and reaccelerate the halted progress of the three Rio Conventions to address climate change, biodiversity loss, and desertification.
A new global water agenda is urgently needed. Existing agendas and conventional water policies, focused mainly on WASH, incremental efficiency gains and generic IWRM guidelines, are not sufficient for the world’s current water reality. A fresh water agenda must be developed that takes Global Water Bankruptcy as a starting point and uses the 2026 and 2028 UN Water Conferences, the conclusion of the Water Action Decade in 2028, and the 2030 SDG 6 timeline as milestones for resetting how the world understands and governs water.
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Report Information
Global Water Bankruptcy: Living Beyond Our Hydrological Means in the Post-Crisis Era, United Nations University Institute for Water, Environment and Health (UNU-INWEH), Richmond Hill, Ontario, Canada, doi: 10.53328/INR26KAM001
Support Paper
Madani K. (2026) Water Bankruptcy: The Formal Definition, Water Resources Management.
About UNU-INWEH
The United Nations University Institute for Water, Environment and Health (UNU-INWEH) is one of 13 institutions that make up the United Nations University (UNU), the academic arm of the UN. Known as ‘The UN’s Think Tank on Water’, UNU-INWEH addresses critical water, environmental, and health challenges around the world. Through research, training, capacity development, and knowledge dissemination, the institute contributes to solving pressing global sustainability and human security issues of concern to the UN and its Member States.
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Drought can impact our health in many ways. Some health effects are short-term and can be directly observed and measured. Drought can also cause long-term public health issues.
Drought health impacts
Water
Reduced stream and river flows can increase the concentration of pollutants in water and cause stagnation. Higher water temperatures in lakes and reservoirs lead to reduced oxygen levels. These levels can affect fish and other aquatic life and water quality.
Runoff from drought-related wildfires can carry extra sediment, ash, charcoal, and woody debris to surface waters, killing fish and other aquatic life by decreasing oxygen levels in the water. Many parts of the United States depend on groundwater as a primary source of water. Over time, reduced precipitation and increased surface water evaporation mean groundwater supplies are not replenished at a typical rate.
Food and Nutrition
Drought can limit the growing season and create conditions that encourage insect and disease infestation in certain crops. Low crop yields can result in rising food prices and shortages, potentially leading to malnutrition.
Drought can also affect the health of livestock raised for food. During drought, livestock can become malnourished, diseased, and die.
Air Quality
The dusty, dry conditions and wildfires that often accompany drought can harm health. Fire and dry soil and vegetation increase the number of particulates that are suspended in the air, such as pollen, smoke, and fluorocarbons. These substances can irritate the bronchial passages and lungs, making chronic respiratory illnesses like asthma worse. This can also increase the risk for acute respiratory infections like bronchitis and bacterial pneumonia.
Other drought-related factors affect air quality, including the presence of airborne toxins originating from freshwater blooms of cyanobacteria. These toxins can become airborne and have been associated with lung irritation, which can lead to adverse health effects in certain populations.
Having water available for cleaning, sanitation, and hygiene reduces or controls many diseases. Drought conditions create the need to conserve water, but these conservation efforts should not get in the way of proper sanitation and hygiene.
Personal hygiene, cleaning, hand washing, and washing of fruits and vegetables can be done in a way that conserves water and also reduces health risks. Installing low-flow faucet aerators in businesses and homes is one example of how to reduce water consumption while maintaining hand washing and other healthy hygienic behaviors.
People who engage in water-related recreational activities during drought may be at increased risk for waterborne disease caused by bacteria, protozoa, and other contaminants such as chemicals and heavy metals. Exposure can occur through accidentally or intentionally swallowing water, direct contact of contaminants with mucous membranes, or breathing in contaminants.
Untreated surface water can be a health threat in drought conditions. In untreated surface waters, some pathogens, such as a type of amoeba (Naegleria fowleri), are more common during drought because low water levels may create warmer water temperatures that encourage their growth.
As the levels of surface waters used for boating, swimming, and fishing drop, the likelihood of injury increases. Low water levels in lakes can put people at risk for life-threatening injuries resulting from diving into shallow waters or striking objects that may not be immediately visible while boating. Low surface water levels can also expose potentially dangerous debris from the bottom of lakes, rivers, and ponds.
Increases in infectious disease can be a direct consequence of drought.
Viruses, protozoa, and bacteria can pollute both groundwater and surface water when rainfall decreases. People who get their drinking water from private wells may be at higher risk for drought-related infectious disease. Other groups also at increased risk include those who have underlying chronic conditions.
Acute respiratory and gastrointestinal illnesses are more easily spread from person to person when hand washing is compromised by a perceived or real lack of available water. During water shortages, the risk for infectious disease increases when hygiene is not maintained.
E. coli and Salmonella are examples of bacteria that can more readily contaminate food and cause infectious disease during drought. Food can serve as a vehicle for disease transmission during a drought because water shortages can cause farmers to use recycled water to irrigate their fields and process the food they grow. When used to grow crops, improperly treated water can cause a host of infectious diseases (such as those caused by toxin-producing E. coli and Salmonella), which can be life-threatening for people in high-risk groups. In addition, the likelihood of surface runoff, which can occur when rain fails to penetrate the dry and compacted soil that often accompanies drought, can cause the inadvertent contamination of crops.
Other infectious disease threats arise when drought leads to the contamination of surface waters and other types of water that are used for recreational purposes. When temperatures rise and rainfall declines, people are more likely to participate in water-related recreation. Persons exposed to contaminated recreational waters are more likely to become infected with pathogens that thrive in the shallow warm waters that exist during drought conditions.
Chronic Disease
Conditions associated with drought may negatively impact people who have certain chronic health conditions such as asthma and some immune disorders.
Drought-related changes in air quality, such as increased concentrations of air particulates and airborne toxins resulting from freshwater algal blooms, can irritate the eyes, lungs, and respiratory systems of persons with chronic respiratory conditions.
Changes in water quality, such as increased concentrations of contaminants, can threaten persons whose immune systems are compromised.
Diseases Transmitted by Insects and Animals
In periods of limited rainfall, both human and animal behavior can change in ways that increase the likelihood of other vectorborne diseases. For instance, during dry periods, wild animals are more likely to seek water in areas where humans live. These behaviors increase the likelihood of human contact with wildlife, the insects they host, and the diseases they carry.
Drought reduces the size of water bodies and causes them to become stagnant. This provides additional breeding grounds for certain types of mosquitoes (for example, Culex pipiens). Outbreaks of West Nile virus, which is transmitted to humans via mosquitoes, have occurred under such conditions. Inadequate water supply can cause people to collect rainwater. This can lead to collections of stagnant water that can become manmade mosquito breeding areas.
This chapter assesses observed and projected climate-induced changes in the water cycle, their current impacts and future risks on human and natural systems and the benefits and effectiveness of water-related adaptation efforts now and in the future.
Currently, roughly half of worlds ~8 billion people are estimated to experience severe water scarcity for at least some part of the year due to climatic and non-climatic factors (medium confidence1 ). Since the 1970s, 44% of all disaster events have been flood-related. Not surprisingly, a large share of adaptation interventions (~60%) are forged in response to water-related hazards (high confidence). {4.1, Box 4.1, 4.2.1.1, 4.2.1.2, 4.2.2, 4.2.4, 4.2.5, 4.2.6, 4.3.8, 4.6, 4.7}
Intensification of the hydrological cycle due to human-induced climate change is affecting physical aspects of water security (high confidence), thereby exacerbating existing water-related vulnerabilities caused by other socioeconomic factors. {4.2, 4.2.1.1, 4.2.1.2, 4.2.1.3, 4.2.2, 4.2.4, 4.2.5, 4.2.6, 4.3}
Extreme weather events causing highly impactful floods and droughts have become more likely and (or) more severe due to anthropogenic climate change (high confidence). {4.2.4, 4.2.5, Cross-Chapter Box DISASTER in Chapter 4}
There is increasing evidence of observed changes in the hydrological cycle on people and ecosystems. A significant share of those impacts are negative and felt disproportionately by already vulnerable communities (high confidence). {4.3.1, 4.3.2, 4.3.3, 4.3.4, 4.3.5, 4.3.6, 4.3.8}
Water-related risks are projected to increase with every degree of global warming (high confidence), and more vulnerable and exposed regions and peoples are projected to face greater risks (medium confidence). {Box 4.1, 4.4.1, 4.4.1.1, 4.4.4, 4.5.4, 4.5.5, 4.5.6, Box 4.2}
Drought and flood risks and societal damages are projected to increase with every degree of global warming (medium confidence). {4.4.4, 4.4.5, 4.4.7, 4.5.1, 4.5.2}
Limiting global warming to 1.5°C would reduce water-related risks across regions and sectors (high confidence). {4.4.2, 4.4.5, 4.5.2, 4.5.3, 4.5.4, 4.5.6, 4.5.7, 4.6.1, 4.7.2}
Observed water adaptation responses have multiple benefits (high confidence), yet evidence of effectiveness of adaptation in reducing climate risks is not clear due to methodological challenges (medium confidence). {4.6, 4.7.1, 4.7.3}
Future projected adaptations are effective in reducing risks to a varying extent (medium confidence), but effectiveness falls sharply beyond 2°C, emphasizing the need for limiting warming to 1.5°C (high confidence). {4.6, 4.7.2, 4.7.3}
Water security is critical for meeting Sustainable Development Goals (SDGs) and systems transitions needed for climate resilient development, yet many mitigation measures have a high water footprint which can compromise SDGs and adaptation outcomes (high confidence). {4.1, Box 4.4, 4.6, 4.6.2, 4.6.3, 4.7, 4.7.1, 4.7.4, 4.7.5.7}
A common set of enabling principles underpinned by strong political support can help meet the triple goals of water security, sustainable and climate resilient development (high confidence). {4.8, 4.8.3, 4.8.4., 4.8.5, 4.8.6, 4.8.7}
4.1 Centrality of Water Security in Climate Change and Climate Resilient Development
Water security is defined as ‘the capacity of a population to safeguard sustainable access to adequate quantities of acceptable quality water for sustaining livelihoods, human well-being, and socio-economic development, for ensuring protection against water-borne pollution and water-related disasters, and for preserving ecosystems in a climate of peace and political stability’ (Grey and Sadoff, 2007). Risks emanating from various aspects of water insecurity have emerged as a significant global challenge. The Global Risks Report by the World Economic Forum lists water crisis as one of the top five risks in all its reports since 2015 (WEF, 2015; WEF, 2016; WEF, 2017; WEF, 2018; WEF, 2019; WEF, 2020). Water also features prominently in the SDGs (Section 4.8) and plays a central role in various systems transitions needed for climate resilient development. Most SDGs cannot be met without access to adequate and safe water (Ait-Kadi, 2016; Mugagga, 2016). In addition, without adequate adaptation, future water-related impacts of climate change on various sectors of the economy are projected to lower the global GDP by mid-century, with higher projected losses expected in low- and middle-income countries (World Bank, 2017; GCA, 2019).
Water quality has been closely related to human health 1 ever since John Snow linked a cholera outbreak in London to contaminated water in 1855.2Vibriocholerae in water still plays a big role in the annual 1.4-4.3 million cholera cases that continue to occur globally. 3 The SARS-CoV-2 virus, which caused the COVID-19 pandemic, also enters the water cycle, as some COVID-19 patients shed the virus with their stool. 4 Although SARS-CoV-2 has been detected in wastewater, and in surface water receiving untreated wastewater, 5 so far there has been no evidence for presence of viable or infectious virus particles in wastewater, or for water as a transmission source. 6 Instead, the European Union launched a study, coordinated by its Joint Research Council and linked to the World Water Quality Alliance, to explore the potential of wastewater-based virus remnants as a sentinel monitoring concept.
But pathogens are not the only problem. Water is contaminated in a number of other ways that can threaten human health. The toxic compound arsenic is widely present in groundwater and can lead to skin, vascular and nervous system disorders, and cancer. 7 Recent estimates show that 94-220 million people are exposed to high arsenic concentrations in groundwater. 8 Similarly, fluoride, nitrate, heavy metals, and salinity in (ground)water pose human health risks.
Biotoxins formed by some cyanobacteria are a particular nuisance because bloom-forming species accumulate at the water surface, requiring closure of bathing sites and drinking water intakes. 9 As well, a large number of organic micropollutants coming from manufacturing and agriculture pose a health risk to the population. 10These organic micropollutants can have a variety of impacts, such as disruption of endocrine, reproductive and immune systems. They can also cause cancer and diabetes as well as thyroid and behavioural problems . 11
More recently recognized contaminants influencing human health include antimicrobial resistant microorganisms (AMR), microplastics 12or nanomaterials. AMR are a concern worldwide 13because infections from them are often difficult to treat. Although the role of water in the spread of AMR is not yet quantified, its importance has been recognized. 14
The potential health risks from microplastics seem obvious, but knowledge of the extent to which they affect human health is limited. 15And, though recent focus has largely been on the marine realm, UNEP will soon publish guidance on monitoring and addressing plastics in freshwater. 16
Water quality is related to human health through exposure. People are exposed to water in many different ways, depending on their location, livelihood, culture, wealth, gender etc. The most common exposure ways can be summarized as drinking, bathing, ingestion during domestic use, eating irrigated vegetables, rice (or rice products) or aquatic plants (such as water spinach), eating contaminated fish and shellfish, and skin contact. These exposure pathways highlight that the quality of ground, surface and coastal waters is relevant to human health.
In an earlier assessment, Snapshot of the World’s Water Quality, 17faecal coliforms were the contaminant included to represent human-health impacts. The assessment concluded that the rural population at risk of health problems, which is defined as those in contact with water contaminated with high concentrations of faecal coliforms, could be up to hundreds of millions of people in Latin America, Africa and Asia. 18While this was an important realization, faecal coliform concentrations do not usually correlate very well with pathogen concentrations, as they can grow in the water body, 19and many more contaminants can have human-health impacts. Therefore, this current assessment incorporates more water quality variables and exposure routes to assess the impact of water quality on human health.
Results
To evaluate the direct and indirect impacts of water quality on human health, we developed a non-exhaustive overview (see Table 3.1). This showed that there are a large number of direct and indirect links between water quality and human health, as well as interrelations between water quality variables, their sources, state, impacts and response. For example, pathogens and nitrate have to some extent the same sources and, therefore, potentially similar response options. But quantitative evidence for the links between water quality and human health are still largely lacking at continental or larger scales.
The global freshwater quality database GEMStat has data for a number of contaminants, but these data vary in space and time. For example, faecal coliform data are available for 6,451 stations across the world, while Escherichia coli data are available from 3,790 stations in North America, South America, Japan, and New Zealand. Data for Salmonella are available for 62 stations along rivers in Europe, but only for a few years in the early 1990s. For arsenic, many heavy metals, nutrients and organic micropollutants some data are available in GEMStat. Here we do not evaluate these data, because they are scattered and recent data for health are scarce. Instead, we report on potential data analyses that have been performed.
Table 3.1The influence of water quality on human health. This list is non-exhaustive, as no detailed literature has been performed. The colour coding is blue for GEMStat or other large-scale databases; red for remote sensing; yellow for modelling; and green for a combination of GEMStat and modelling. Dark colours are for surface water, light colours for groundwater.
Abstract Background Pollutants including metals/metalloids, nitrate, disinfection byproducts, and volatile organic compounds contaminate federally regulated community water systems (CWS) and unregulated domestic wells across the United States. Exposures and associated health effects, particularly at levels below regulatory limits, are understudied.
Objective We described drinking water sources and exposures for the California Teachers Study (CTS), a prospective cohort of female California teachers and administrators.
Methods Participants’ geocoded addresses at enrollment (1995–1996) were linked to CWS service area boundaries and monitoring data (N = 115,206, 92%); we computed average (1990–2015) concentrations of arsenic, uranium, nitrate, gross alpha (GA), five haloacetic acids (HAA5), total trihalomethanes (TTHM), trichloroethylene (TCE), and tetrachloroethylene (PCE). We used generalized linear regression to estimate geometric mean ratios of CWS exposures across demographic subgroups and neighborhood characteristics. Self-reported drinking water source and consumption at follow-up (2017–2019) were also described.
Results Medians (interquartile ranges) of average concentrations of all contaminants were below regulatory limits: arsenic: 1.03 (0.54,1.71) µg/L, uranium: 3.48 (1.01,6.18) µg/L, GA: 2.21 (1.32,3.67) pCi/L, nitrate: 0.54 (0.20,1.97) mg/L, HAA5: 8.67 (2.98,14.70) µg/L, and TTHM: 12.86 (4.58,21.95) µg/L. Among those who lived within a CWS boundary and self-reported drinking water information (2017–2019), approximately 74% self-reported their water source as municipal, 15% bottled, 2% private well, 4% other, and 5% did not know/missing. Spatially linked water source was largely consistent with self-reported source at follow-up (2017–2019). Relative to non-Hispanic white participants, average arsenic, uranium, GA, and nitrate concentrations were higher for Black, Hispanic and Native American participants. Relative to participants living in census block groups in the lowest socioeconomic status (SES) quartile, participants in higher SES quartiles had lower arsenic/uranium/GA/nitrate, and higher HAA5/TTHM. Non-metropolitan participants had higher arsenic/uranium/nitrate, and metropolitan participants had higher HAA5/TTHM.
Impact Though average water contaminant levels were mostly below regulatory limits in this large cohort of California women, we observed heterogeneity in exposures across sociodemographic subgroups and neighborhood characteristics. These data will be used to support future assessments of drinking water exposures and disease risk.
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Human health implications of metal pollution in the Betwa-Yamuna river system, India: evidence from Monte Carlo risk modelling Article Open access 11 January 2026 Introduction Drinking water represents an important source of exposure to inorganics (e.g., arsenic and nitrate), radionuclides (uranium, alpha particles), disinfection byproducts (DBPs), and volatile organic compounds (VOCs) for populations in the United States (U.S.) and worldwide [1]. Approximately 90% of the U.S. population is served by public water systems, and 10% by private wells [2]. In California, approximately 95% of the population is served by public water systems [3]. Public water systems include at least 15 service connections or serve at least 25 people; community water systems (CWS) are a type of public water system that serve the same population year-round [2]. Public water systems are regulated by the U.S. Environmental Protection Agency (EPA) under the Safe Drinking Water Act [4]. The contaminants we evaluated are regulated through federally enforceable maximum contaminant levels (MCLs), which were determined based on economic and technical feasibility, treatment technologies, cost-benefit analysis, and public health benefit for specific health endpoints [4]. States generally have primacy over enforcement of federal drinking water regulations. Notably, the MCL goal, a non-enforceable standard based solely on risk to health, is 0 µg/l for arsenic, uranium, alpha particles, trichloroethylene (TCE), tetrachloroethylene (PCE), bromodichloromethane, bromoform, and dichloroacetic acid, as there is no known safe level of exposure to these contaminants [4]. Private wells are not federally regulated or monitored.
Nitrate is a common contaminant of drinking water supplies in agricultural areas, due to use of nitrogen fertilizers and concentrated animal feeding operation waste [5, 6]. Atmospheric deposition, erosion of natural deposits, and septic tank or sewage leakage contribute to nitrate contamination in rural and urban areas [4]. Geogenic arsenic occurs in groundwater across the U.S., with regional differences due to climatic and geological factors; arid climates can cause evaporative concentration of arsenic in shallow groundwater supplies and lead to high levels, such as in the San Joaquin Valley of California [7,8,9,10]. Mining and historical arsenical pesticide use are anthropogenic sources of arsenic contamination in water supplies [8]. Uranium is present in different rock types and is leached from host mineral phases to surface and ground water supplies; uranium mining/milling and mobilization of uranium via nitrate fertilizer use are anthropogenic sources of uranium contamination [11,12,13,14,15]. Uranium and other radionuclides can decay and release alpha radiation, often quantified as total gross alpha for monitoring compliance purposes. DBPs are formed by the reaction of chlorine and bromine with natural organic compounds during the disinfection of water supplies to treat pathogens [16]. DBPs are commonly found in public water supplies across the U.S., with the highest concentrations observed in those reliant on surface water or shallow groundwater [16]. While over 700 DBPs have been identified, the most abundant classes are trihalomethanes (THMs, which include the chemicals chloroform, dibromochloromethane, bromodichloromethane, and bromoform, and regulated as the sum total, TTHM), and haloacetic acids (HAA5, regulated as the sum of dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, bromoacetic acid, and dibromoacetic acid) [4, 17, 18]. The VOCs TCE and PCE are solvents used in dry cleaning, metal degreasing, textile, art, and industrial processes, and may be found in some consumer products [19]. Toxic waste disposal sites, sometimes recognized as Superfund sites under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), are anthropogenic sources of inorganic arsenic, uranium, TCE, and PCE in groundwater [12, 19,20,21,22,23,24].
Numerous studies implicate one or more of these drinking water contaminants in adverse health effects, including cancer, cardiovascular disease, reproductive and developmental toxicity, nephrotoxicity, and other adverse health conditions [1, 16, 20, 25,26,27,28,29,30,31,32,33,34,35,36,37,38,39]. Inorganic arsenic is classified by the International Agency for Research on Cancer (IARC) as a cause of cancers of the bladder, lung, and skin, and is associated with increased risk of cancers of the kidney, liver, and prostate [26]. Inorganic arsenic is also a potent toxicant associated with numerous adverse health outcomes, including cardiovascular disease, hypertension, and reproductive disorders [26, 31, 32]. Uranium exposure through drinking water is associated with renal damage and nephrotoxicity, and an increased risk of colorectal, breast, kidney, prostate, and total cancer [20, 27, 33]. Nitrate is classified by IARC as a probable human carcinogen when ingested under conditions that result in the endogenous formation of N-nitroso-compounds, most of which are animal carcinogens [28, 34]. Cancers of the stomach, colon, bladder, kidney, ovary, and thyroid, and thyroid disease are associated with elevated nitrate ingested from drinking water; however, the number of studies of most cancer sites is limited [29, 35]. Higher intake of DBPs through drinking water is associated with increased bladder cancer risk, and a limited number of studies suggest DBP exposures are potential risk factors for colon, rectum, and endometrial cancer [16, 36]. TCE is classified as carcinogenic to humans based on kidney cancer, and PCE (Group 2A) as probably carcinogenic to humans based on bladder cancer evidence [30]. Occupational studies also support adverse developmental, neurological, and hepatotoxic effects of TCE and PCE exposures [19]. Assessment of long-term drinking water contaminant exposures and associated health risks have traditionally been limited by the lack of water quality data that could be assigned to individuals in epidemiologic cohorts; understanding large-scale water quality data at the level of consumer intake is a critical research gap [40]. Additionally, there are relatively few cohort studies evaluating drinking water exposures at levels below the MCLs and World Health Organization guidelines that are commonly experienced by the general U.S. population [1]. Inequalities in CWS arsenic, uranium, and nitrate exposures by sociodemographic characteristics such as, race and ethnicity, income, education, region, and rurality/urbanicity have been documented [41, 42]. Few studies have evaluated sociodemographic inequalities in DBP and TCE/PCE exposures in the United States.
Our primary objective for this study was to describe exposure to regulated, frequently detected and measured contaminants in drinking water in the California Teachers Study (CTS), a large prospective cohort of women. We described the spatial linkage of participants’ residences to their drinking water source and corresponding estimates of contaminant concentrations. For a subset, we evaluated the agreement between address-assigned and self-reported drinking water source and described the daily intake of tap water and CWS contaminants. Additionally, we examined inequalities in CWS exposures across sociodemographic groups.
Throughout the fall, Harvard Chan faculty will share evidence-based recommendations on urgent public health issues facing the next U.S. administration. Ronnie Levin, instructor in the Department of Environmental Health, offered her thoughts on policies that could address contamination in the country’s drinking water supply.
Q: Why is drinking water quality a pressing public health issue?
A: The U.S. has arguably the best and most reliable drinking water in the world, and that’s because we’ve spent a lot of money and time getting it in that shape. On the other hand, our drinking water is not risk-free. It’s not perfectly safe—it can contain lead, nitrate, PFAS, arsenic, and uranium, as examples. In addition, there are racial and ethnic disparities in contaminant exposures, so not everybody gets the same quality of drinking water.
Q: What are the biggest challenges facing the next administration around improving drinking water quality?
A: A hundred years ago, we sunk a lot of money into water treatment and infrastructure, but then we stopped putting in that kind of investment. Now our water systems are severely aging and deteriorated, and we haven’t continued to maintain the older ones. And when we build new ones, they’re not always as well designed as the old ones.
In addition, science has moved on—we’ve found things in our drinking water that we thought weren’t bad, like PFAS, that turn out to be biologically active at very low levels. Lead, arsenic, and nitrate cause health effects at lower levels than we knew when we set the standards decades ago. We now need to catch up.
Ronnie Levin. Photo: Kent Dayton Q: What are your top policy recommendations to address drinking water quality?
A: There’s been recent progress toward reducing lead in drinking water. On Oct. 8, the Environmental Protection Agency (EPA) announced a rule that requires all lead pipes in U.S. water systems to be replaced within the next decade, lowers the current level for taking action to reduce lead exposure from 15 to 10 parts per billion, and also implements several other policies to reduce exposure to lead from drinking water. If the rule is implemented and enforced, millions of people will have cleaner, safer water. Importantly, it will particularly enhance environmental protection among disadvantaged and low-income populations, which have been disproportionately impacted by lead-contaminated water.
There are several other contaminants I’d like to see the government address. PFAS are a class of thousands of chemicals that are in all kinds of consumer products. We don’t even know all of them, because industry keeps tweaking them to be different and cheaper, and industry doesn’t have to report how they get used. There are PFAS everywhere, contaminating water, soil, air, and food, and they build up in people and the environment over time.
We don’t know a lot about the thousands of different PFAS because it takes years to do studies, and we haven’t known about them for that many years. But research so far has suggested that PFAS are associated with a host of biological changes, even at very low levels. PFAS exposure has been linked with many adverse health outcomes, such as decreased immune system function, thyroid disease, and kidney and testicular cancers.
The EPA recently set regulations for six PFAS chemicals, ones that we know are the easiest to measure and are associated with numerous health effects. Many people are researching PFAS, but industry is constantly altering the formulations for new and different applications, and so there’s no way to stop this train. But the EPA’s efforts are really good news.
Another issue that the EPA needs to address is revising the standard for arsenic in drinking water. We’ve known that arsenic is a poison for a really long time, and that’s actually what makes it so useful—we use it in chemotherapies, pesticides, and herbicides. It has a lot of other useful applications, like in paints and glassmaking. But arsenic has negative health effects across the board, including cardiovascular harms, liver damage, neurotoxicity, and reproductive toxicity.
The arsenic limit for drinking water—which was set in 2001 at 10 parts per billion—is probably an order of magnitude too high. It was looking like the EPA might propose lowering the arsenic standard in the next few years, but with the change in administration, that likelihood is looking dim. There’s a lot of resistance from industry and water utilities, but I think taking action on arsenic will be easier than regulating so many different types of PFAS, which is going to take a lot longer.
As for the EPA’s nitrate standard, it is dangerously high, and violations of the nitrate standard are the most common health-based violations of drinking water standards.
In general, the EPA is behind in keeping the drinking water standards up to date with the current scientific literature. Setting standards is a laborious process and, in addition, there is tremendous pushback from the “drinking water industry”—public water systems, which are often cities themselves, or semi-governmental agencies like the Massachusetts Water Resources Authority, which oversees water systems in the Boston metropolitan area. There are 50,000 active public water systems in the U.S., and there is a lot of complaining from those systems about the difficulty and expense of meeting stricter standards.
Q: What’s the evidence supporting those recommendations?
A: My colleagues and I wrote a 2023 review article about the exposure risks of a wide range of drinking water contaminants, including PFAS, arsenic, and more. In that article, we cited a number of studies linking these chemicals to health harms:
A 2023 meta-analysis of over a dozen different studies found that several types of PFAS may lower the body’s ability to produce antibodies after receiving vaccines, particularly for diphtheria, rubella, and tetanus. A 2022 meta-analysis of over 100 rodent and human epidemiological studies identified a link between PFAS exposure and liver injury. A 2013 study followed almost 4,000 individuals for around two decades, and found that higher arsenic levels in urine were associated with increased mortality from lung, prostate, and pancreatic cancers. A 2015 meta-analysis of over a dozen studies identified a link between arsenic exposure and adverse pregnancy outcomes and infant mortality. A 2021 study analyzed nationwide data collected by the Centers for Disease Control and Prevention, finding that an increased level of arsenic in urine was associated with heart disease mortality. Q: What do you hope can be accomplished to improve drinking water quality in the next four years?
A: Addressing both PFAS and arsenic will be difficult and expensive, and also take a lot of political will. The Supreme Court has tied the EPA’s hands through decisions such as eliminating the Chevron deference, which called for deferring to federal agencies for their judgments where federal law is silent or unclear, and the 2023 Sackett v. EPA case, which limited the agency’s power to regulate wetlands and waterways. The EPA can’t just issue regulations, it has to get laws passed through Congress, which is much harder to do. It used to be that the courts would defer to the EPA, but now the agency is going to have to make a much stronger case for regulations.
Regarding lead, now that the Biden administration has finalized the new lead pipe rule the government needs to make sure that the rule is implemented and enforced.
We have to regain a commitment to protecting human health and the environment, and clean drinking water should be a top priority. We have a lot of hard work to do.
Microplastics (MPs), defined as plastic particles smaller than 5 mm, are an emerging global environmental and health concern due to their pervasive presence in aquatic ecosystems. This systematic review synthesizes data on the distribution, shapes, materials, and sizes of MPs in various water sources, including lakes, rivers, seas, tap water, and bottled water, between 2014 and 2024. Results reveal that river water constitutes the largest share of studies on MP pollution (30%), followed by lake water (24%), sea water (19%), bottled water (17%), and tap water (11%), reflecting their critical roles in MP transport and accumulation. Seasonal analysis indicates that MP concentrations peak in the wet season (38%), followed by the dry (32%) and transitional (30%) seasons. Spatially, China leads MP research globally (19%), followed by the USA (7.8%) and India (5.9%). MPs are predominantly composed of polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), with fibers and fragments being the most common shapes. Sub-millimeter MPs (<1 mm) dominate globally, with significant variations driven by anthropogenic activities, industrial discharge, and environmental factors such as rainfall and temperature. The study highlights critical gaps in understanding the long-term ecological and health impacts of MPs, emphasizing the need for standardized methodologies, improved waste management, and innovative mitigation strategies. This review underscores the urgency of addressing microplastic pollution through global collaboration and stricter regulatory measures.
The growing intrusion of microplastics (MPs) into water supply networks, exacerbated by their physicochemical features that facilitate their movement in water and enable microbial attachment, represents an under-recognized but rising threat to public health. The present work is a scooping review that synthesized recent studies to explore the roles of MPs as dynamic pollutants that not only contaminate water sources and distribution systems but also interact with bacterial contaminants in ways that intensify health threats. In accordance with SDG 6 (Clean Water and Sanitation), we examined the sources and fate of MPs in water distribution networks, their mechanisms of transportation, and their function as surfaces for bacterial attachment and biofilm development. We paid attention to how MPs can carry harmful bacteria and store genes that make bacteria resistant to antibiotics, which could help these bacteria survive and spread throughout the water distribution system, an issue related to SDG 3 (Good Health and Well-being). These microplastic-associated biofilms called plastisphere can compromise water quality assessments, escape conventional water treatment procedures, and aggravate the distribution of antimicrobial resistance. Furthermore, we highlight the limits of existing detection and monitoring methods for MPs and related bacterial threats in water. We ascertain serious knowledge gaps in understanding the long-term behaviour of MPs in real-world water distribution conditions, particularly under variable hydraulic and environmental stresses. Addressing these gaps require imminent research focus on in situ studies of MP-bacterial interactions, innovative molecular and sensing machineries, risk valuation models that integrate microbial and genetic information (SDG 9: Industry, Innovation, and Infrastructure). Interdisciplinary collaborations among environmental microbiologists, water engineers, and public health workers could also help to develop a standardized, high-resolution detection protocols.
GET WET! 
