Thousands of families are unknowingly drinking tap water laced with lead putting them at risk of long-term health damage, The Mail on Sunday can reveal.
Once widely used in both domestic plumbing and public water mains, lead piping was banned in 1970 after mounting evidence showed the toxic metal could leach into drinking water. By then, studies had already linked lead exposure to developmental delays, behavioural issues and reduced IQ in children - as well as high blood pressure, kidney damage and an increased risk of heart attack and stroke in adults.
Since then, safer alternatives such as copper and plastic have become standard - but millions of homes may still have hidden lead pipes, silently putting residents in danger.
Around six million properties built before the 1970 ban still have internal lead piping. Meanwhile, water companies are replacing ageing mains at such a slow pace that it could take more than 1,000 years to remove all piping with the toxic metal, a Government report has said.
Experts warn this represents a serious threat to public health. Late last year the UK Health and Security Agency (UKHSA) reported a worrying rise in children being admitted to hospital with lead poisoning. Concerned doctors at the time said the likely cause in many cases was lead-contaminated drinking water.
In response, this newspaper launched an investigation to uncover just how many families are being exposed to dangerous levels of lead.
Environmental Information Requests to 16 of the UK's water companies revealed a shocking 2,500 properties over the past three years had levels that posed a risk to human health.
These reports are generated when concerned homeowners ask firms to test their tap water.
Mother-of-one Deborah White, 58, sought the test after finding lead piping in her home. She suffers from persistent headaches, digestive problems and muscle pain.
Our analysis has shown that there are lead contamination hotspots in cities such as Leeds, Brighton and Southampton.
For most breaches, the lead concentration was found to be ten times the legal limit - and in some cases far more. Health damage can occur after consuming water with much lower levels.
These incidents have, until now, not been made public.
We can also reveal that UKHSA has issued 160 'do not drink tap water' orders due to lead contamination over the past three years.
This occurs when water company mains testing - which must be carried out as a legal obligation - finds an issue.
Our analysis has shown that there are lead contamination hotspots in cities such as Leeds, Brighton and Southampton.
We contacted a number of those affected across the UK.
One woman from Fife discovered she had lead levels in her blood at twice the safety limit, after tests at her GP.
Deborah White, 58, sought the test after finding lead piping in her home. She suffers from persistent headaches, digestive problems and muscle pain - symptoms that can be linked to lead exposure.
A mother-of-one in Hertfordshire said she believes tap water in her 1960s home, which tested positive for high lead levels, led to her three-year-old daughter suffering learning difficulties. The lead mains were discovered during renovations and she sought testing from the local water company, which confirmed contamination.
Blood tests showed her then-newborn had elevated lead levels. Three years on, she believes they are starting to see the consequences.
'We have seen development issues with her, doctors have said she likely has ADHD, which we believe is down to the lead,' she said. 'It has also been really challenging in terms of her education. She just isn't picking things up as quickly as others.'
The mother fears that drinking tap water while she was pregnant impacted her daughter while still in the womb.
Brighton-based Shalim Ahmed, 45, says he fears for his children's health after finding lead pipes in his home. It meant they had been drinking contaminated water for a decade.
'You hear about this in other parts of the world but you don't think that it is still an issue here,' says the father of three. 'I was shocked when I found out and I am scared about the impact it may have had.'
Others have paid thousands to remove lead piping - and those who could not afford to do so rely on bottled water. The 2,500 cases uncovered by this newspaper may be just the tip of the iceberg, as they only represent instances where homeowners have actively requested lead testing.
Water contaminated by lead looks, smells and tastes no different from ordinary tap water, and experts claim thousands more families may be drinking water with dangerously high lead levels.
Dr Wayne Carter, head of the Clinical Toxicology Research Group at the University of Nottingham, said: 'The bottom line is that lead is toxic and there is no safe level of exposure.'
'So, the fact the tests show that water in people's homes is still above the legal limit is real concern.' More than 200 children were admitted to hospital in 2023 while suffering from lead poisoning, according to the UKHSA.
The condition occurs when the metal begins to build up in the brain and other organs. The report stated that 6 per cent of these cases were because of lead pipes.
Despite this, doctors do not routinely test for lead in the blood and a screening programme for children aged one to five was rejected in 2018. The UK National Screening Committee explained the decision by stating the prevalence of 'elevated levels' of lead was 'low'.
Professor Alan Emond, a specialist in children's health at the University of Bristol, believes this was a missed opportunity.
'Any exposure to lead in children will have an impact,' he said. 'We know that lead exposure early in childhood can have an effect on development as it can get stored in bones and leaches out over time, affecting the brain. Lead exposure has an impact on cognition, behaviour and can impact a child's results at school.'
A review of more than 2,500 studies published this month in the journal Ecotoxicology And Environmental Safety found exposure to lead, even at low levels, was linked to behavioural and developmental issues.
Professor Emond said: 'The issue in the UK at the moment is we simply do not know how big a problem this is across the country.'
Professor Alastair Hay, a toxicology expert at the University of Leeds, explained: 'For every microgram of lead in the blood, there's a measurable drop in a child's IQ. Pregnant women are particularly vulnerable, as lead crosses the placenta and can affect the developing foetus.'
Low-level lead exposure is not only an issue for children. A 2018 study of 14,000 adults in the US published in the Lancet found that 18% of all deaths, 28% of cardiovascular disease deaths and 37% of heart disease cases could be attributed to high lead levels.
The UK may be falling behind other countries on the issue.
The recommended maximum allowable amount of lead in British water is ten micrograms per litre, which has been the World Health Organisation's guidance since 1993. The US lowered its limit to zero as it believes there is no safe amount of lead for humans.
Last year, then US president Joe Biden announced a £2 billion plan to replace all lead pipes in the next decade. Meanwhile, the EU has halved its legal lead limit to five micrograms per litre.
'We need to be looking to drive the level down to zero,' said Professor Hay. 'Following the EU in halving the level would halve the level in the blood which would minimise the impact on children. The issue is that in the UK these things get pushed back and overlooked.'
Dealing with the problem is not simple in Britain because the pipework that supplies clean water is shared between water companies and property owners.
Despite replacements now being carried out, research has suggested that a quarter of pipes (three million) are still lead.
The UK's Drinking Water Inspectorate has found that, unless the pace increases, it will take until the year 3273 for the country's drinking water to be lead-free.
'Given the known health problems associated with lead, there is no justification for having lead pipes,' says Professor Emond.
As well as mains inside the home, any piping in the property boundary - which transports water from the street to the house - is the homeowner's responsibility. And in many cases, these are lead.
'If your home was constructed before 1970 there is a really good chance that you have lead pipes somewhere on your property,' says Dr Jeremy Auerbach, an expert in urban geography at University College Dublin. 'Yet we don't discuss it, young parents aren't aware and it can have disastrous consequences - it is a silent public health crisis.'
Water companies try to mitigate the risk by treating the supply with orthophosphate, a lead 'antidote'. However, this doesn't eliminate lead in the water.
'Particularly with ageing pipework, which is more likely to crack, treating the water is not enough to prevent lead in tap water. The pipes need to be replaced,' adds Dr Auerbach.
Homes across the country are still at risk of contaminated tap water despite the water regulator Ofwat allowing firms to raise £186 million by hiking bills to tackle the issue. Some companies, such as United Utilities in the North West, have schemes to help homeowners replace the pipes they own.
But the likes of Madeleine Marsh, 42, have had to spend vast sums removing lead piping.
The accountant moved into her three-bed house in Southampton in 2019 and found she had lead pipes. Southern Water said it was not its responsibility.
'When my partner said he wanted to get the water tested, I said don't be ridiculous,' recalled Madeleine. 'We have kids now so feel fortunate that we spotted it when we did, but it cost £4,000 which was a lot of money to have to spend.'
Dr Carter said: 'This is not about drinking one glass of contaminated water, but the effect that long-term, low-level lead exposure can have, and water companies need to be testing more pro-actively to ensure regulations are met.'
Campaigner Tim Pye, from the Lead Exposure and Poisoning Prevention Alliance, said: 'It's a shocking situation - in some homes, levels have been found to be over 100 times too high, and one 230 times too high.'
The group is calling for a change in the law to ensure landlords are responsible for removing internal lead pipes.
It has also been calling for a national screening programme for lead exposure in children. A pilot scheme was launched last September in Yorkshire, with the UKHSA to present its findings next year.
A Drinking Water Inspectorate spokesman said: 'Drinking water in England is among the most-tightly regulated and best quality in the world. Water companies consistently meet stringent regulatory standards for drinking water, with 99.97 per cent of samples complying with regulatory standards in 2023.'
'Lead plumbing in public buildings and domestic premises remains a measurable risk to public health, and more work is needed to address legacy issues of lead in pipework and plumbing. Presence of lead as demonstrated by compliance must be addressed in future planning; action is needed.'