Published in Nature Cities, the study revealed the problem worsened following changes to the housing market triggered by the 2008 global crash. Since 2017 it has been “expanding in scope and severity” to impact several US cities, including Portland (OR), Phoenix, Houston, Atlanta, Dallas-Fort Worth, and Philadelphia, as well as large urban areas such as Los Angeles, New York City and San Francisco.

The researchers from King’s College London and the University of Arizona also found that “people of color” were disproportionally affected by a lack of household water, a situation defined as ‘plumbing poverty’, in 12 of the 15 largest cities.

For the USA to meet the United Nations goal for everyone to have access to safe drinking water, sanitation and hygiene would require massive change in housing conditions and social infrastructures.

Lead researcher Professor Katie Meehan, professor of environmental justice at King’s College London, said: “It’s alarming how many US cities, including those thought of as affluent and growing, are now home to more people living in situations of extreme poverty, namely without access to running water.

“Our research is the first effort to track these changes over time, starting in the 1970s and noting a dramatic urbanization of plumbing poverty in the 1990s and sharp acceleration triggered by the 2008 crash, and the current housing and cost-of-living crisis.

She added: “Far too many people, especially “people of color”, are now in such extreme poverty they’re being pushed into homes that do not meet the basic standard for human dignity and life.”

Meehan said people can find themselves living without running water because of a host of reasons and, in most cases, people are working but not earning enough. Some households might have been disconnected from water service after falling behind with bills or had to “downgrade” to housing without any water access because other expenses take priority. Others might be tenants in homes that have been poorly maintained and cannot afford to move out; some might be living in buildings such as sheds or warehouses; while others could be homeless.

Lucy Everitt, a PhD student at King’s College London who was part of the research team, said water service shut-offs are a hidden problem across US cities.

“New York City tops the ‘worst offenders’ list for the total number of households in a US metro without running water,” she said. “Despite this, the municipal Water Board issued more than 2400 shutoff notices in March of this year alone to properties behind in their payments. Because our analysis tracks the status of running water in households, as measured by the US Census, we anticipate that we are capturing many thousands of households whose access is denied by their inability to pay.”

The authors recommend reforms so that the US Census Bureau can improve its collection of nationwide data about household water access and the extent of water service shutoffs, to monitor and meet Sustainable Development Goals. They also argue that local water utilities and water boards must overhaul low-income assistance programmes in light of the expanding cost-of-living and housing expenses, which are inhibiting people’s ability to pay for water services.