Professor Chris Whitty urges UDG conference to rethink sewerage risks to public health

29 January 2026

Speaking at the annual conference of CIWEM’s Urban Drainage Group, the chief medical officer for England looked to past successes as a guide to future resilience

When Professor Chris Whitty spoke at the Urban Drainage Group (UDG) Annual Conference in November 2025, his message to engineers and water professionals was deliberately blunt. “The principal reason we’re all here actually is to protect public health,” he said. “And that’s something we can sometimes overlook.”

For Whitty, chief medical officer for England and a practising consultant epidemiologist, sewerage and drainage are not secondary environmental services or quality-of-life add-ons. They are, historically and still today, among the most powerful public health interventions ever devised. His wide-ranging address traced that argument from 19th-century cholera outbreaks to contemporary debates about storm overflows, wastewater treatment standards and the emerging risks from pathogens and chemicals in rivers.

Sewerage as the foundation of public health

Modern public health, Whitty reminded his audience, was born out of crises in urban sanitation. Cholera, the archetypal waterborne disease, first reached pandemic scale in 1817 and has killed tens of millions of people worldwide since. In the UK, the 1854 outbreak in London saw very high mortality rates in some areas, prompting John Snow’s famous intervention at the Broad Street pump.

The scale of those epidemics forced cities to act. “Manchester, Liverpool, Birmingham – that’s why chief medical officers were appointed by municipalities,” Whitty said, noting that the post of chief medical officer for England soon followed. “I owe my job to the same thing that all of you owe your job to. We all started in the same place.”

“Death's Dispensary: Open to the Poor, Gratis, by Permission of the Parish”

What made cholera and similar diseases so devastating was their mode of transmission. Faecal-oral pathogens are uniquely effective, Whitty explained, because they can spread without direct contact between people. “Essentially something goes out of the backside of one person and into the mouth of another,” he said, allowing infection to travel “many miles downriver” or through water supply systems.

The solution was, and remains, engineering. The vast investment in sewerage systems from the mid-19th century onwards was justified on public health grounds, Whitty argued. “People sometimes forget that, but that is the central aim of sewerage and drainage. All other aims are secondary.” Above all, sewerage exists “to separate human faeces from the water people drink”.

The results have been dramatic. In high-income countries, waterborne and water-washed infections are now rare – but, as Whitty stressed, this is a relatively recent achievement, and not one that can be taken for granted.

Where pathogens enter rivers today

Turning to the present, Whitty highlighted two main routes by which human pathogens reach rivers in England. The first – storm overflows – is well known and politically charged. The second, he suggested, has received far less public attention: discharges from wastewater treatment works that are operating normally and within their permits.

“What became clear to me,” he said, after discussions with engineers and hydrologists, “was there’s a huge amount we don’t actually know.” In many cases, there is limited evidence on how effectively specific pathogens are reduced as sewage passes through treatment works. Much of the underlying science and engineering dates back decades.

As a result, the sector is “to some extent operating blind”. During low-flow conditions, when rivers provide less dilution, a higher proportion of pathogens in watercourses may come from treated effluent rather than storm overflows. Crucially, these conditions coincide with the times when people are most likely to be exposed. “These tend to be the times of year when the great majority of children and adults tend to use water environments,” Whitty noted, particularly during summer.

Climate change and population growth add to the challenge. Lower river flows combined with increasing wastewater volumes mean concentrations of pathogens are likely to rise. “This problem is not going to get better over time,” Whitty said. “It’s going to get bigger over time.”

Chemicals, accumulation and uncertainty

Whitty was careful to distinguish between infectious risks and chemical risks in water. Chemicals, he said, generally follow the principle that “the dose makes the poison”. Unlike infections, harm usually increases in a roughly linear way with exposure, and chemicals do not transmit from person to person.

However, that does not make them benign. Whitty highlighted growing concern about cumulative exposure to chemicals, microplastics and nanoplastics, some of which enter the human body via water. “We really are in our infancy of understanding what the effects of these chemicals over time is,” he said. They may turn out to be relatively harmless – or they may be contributing to inflammatory diseases, including cardiovascular disease and dementia.

The risk, Whitty warned, is hindsight. “The danger is we’ll get to a point where we realise that this was a harm… and wish we’d done something about it previously.”

Proportionate engineering and a policy opportunity

For Whitty, the key question is not whether engineering solutions exist. Filtration, disinfection and advanced treatment technologies are well understood. The challenge is proportionality. “My thesis to you is, I think we have currently got a system that is not proportionate to the risk.”

Some interventions involve high capital costs, others ongoing operational costs, and some address both pathogens and chemicals simultaneously. Deciding which to pursue requires better evidence and clearer objectives – including explicit public health goals.

Here, Whitty aligned himself with the recent Cunliffe Review of the water sector, which recommended that public health considerations be more firmly embedded in regulatory frameworks. This emphasis is increasingly reflected in the government’s direction of travel. England’s recently published Environment Improvement Plan acknowledges “growing concern about the potential public health risks associated with exposure to a range of contaminants being released into natural waterways” and commits to strengthening health protections within water regulation. Commitments include research into faecal-oral disease risks from treated wastewater, investment in storm overflow reductions, and a forthcoming plan to address PFAS and other persistent chemicals.

Whitty welcomed the surge in public and political attention on water. It is, he said, both a threat – risking “overwrought public discourse” – and an opportunity. “This is a moment where we can re-look at the infectious risks and indeed the chemical risks and say, look, the public really does care about this.”

But that window may not stay open. Public concern can be fleeting, and poorly targeted action risks wasting resources. “The danger is otherwise we end up either not doing anything because we don’t have good enough data, or we end up doing a whole bunch of stuff because there's a very strong political will to do it and it turns out to be not a proportionate or effective way to deal with the problems.”

The important work beneath our feet

Whitty closed with a reminder of scale and perspective. “Drainage, sewerage and drinking water engineering are the most important public health interventions,” he said. “Arguably historically, the only thing which comes close is vaccination.”

The reason Britain can sustain its dense cities, he argued, lies beneath them. Invisible networks of pipes and treatment works have quietly prevented the faecal-oral diseases that once shaped urban life. “You are doing some of the most important public health work in the country,” Whitty told his audience.

His challenge to the sector was clear: to ensure that public health once again sits at the heart of decisions about sewerage, investment and regulation – not as an afterthought, but as the primary purpose it has always served.

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Jo Caird is editor of The Environment