Earlier this month it was announced that fluoride will be added to the water supplies of millions more Britons under Government plans to improve dental health.
While the mineral has been added to water supplies in parts of the UK for decades – and NHS and experts including chief medical officer Sir Chris Whitty insist it is inherently safe – the plans are not without controversy and have attracted unfounded internet conspiracy theories.
So what’s the truth about fluoride’s health benefits and drawbacks? And what else is lurking in our tap water in the UK? Could it be doing any harm?
Our interactive graphic below shows the key chemicals and even pathogens we might unknowingly drink every day.
The specific level of substances detected varied across the country and represent only minute traces per litre. Of the thousands of tests conducted only a small fraction returned a positive result above threshold levels.
This graphic shows the potentially concerning chemicals, metals and pathogens that could be lurking in your tap water. Blue bars indicate the levels allowed of each substance per litre while red bars show the number of times this level was breached in English public water supplies in 2022.
Fluoride is abundantly safe at the levels most consume. Yet it’s still a huge source of controversy.
Adding it to drinking water is a flashpoint issue in the US, with presidential hopeful Robert F. Kennedy Jr even labelling it ‘neurotoxic’ and vowing to remove it from drinking supplies if elected.
Britain isn’t immune to these sentiments. Both the Green Party and Tories have opposed it in the past, partly in response to pressure from local communities.
Some studies have previously linked fluoridation to cases of Down’s syndrome in babies, and rates of kidney stones and even some cancers.
However, the NHS and experts like Sir Chris Whitty say these claims are ‘exaggerated and unevidenced’.
Outlandish conspiracy theories touting fluoride as a plot by the global elite to depopulate the world or that it is being used for mind control purposes are also frequently spread online.
Only one health issue has been definitely linked to fluoride: a problem called fluorosis. Dental fluorosis is the most common form and occurs when a child’s teeth are exposed to too much of the mineral while developing.
This leads to fine, pearly white lines or flecking appearing on the surface of the teeth.
Severe cases can cause the tooth’s enamel to become pitted or discoloured, however health officials say this is incredibly rare in the UK.
A more extreme version is skeletal fluorosis, but this typically occurs in areas where fluoride levels are naturally high, rather than places where it is artificially added.
The risk of fluorosis is one of the reasons why the World Health Organization (WHO) recommends fluoride in drinking supply shouldn’t go above 1.5 mg/L, a limit also set in the UK.
In the UK, excess fluoride of any source is removed in drinking water as part of the treatment process to bring it to at most the standard 1.5mg/L level.
Some 6.1million people in England, about one in 10, currently receive fluoridated water.
More than six million people in England, about one in 10, currently receive fluoridated water.
However, this is set to change with the Government vowing to add fluoride into the supplies of another 1.6million people, with further expansions planned for the future.
Latest data from the Government’s Drinking Water Inspectorate (DWI), which monitors drinking water supplies to ensure they meet safety parameters, shows there were zero fluoride breaches for public water supplies in 2022.
Public water is what the vast majority of the population in England receive because it is supplied by water companies.
However, 1.4 per cent of tests for private water supplies, those provided on site in rural areas, such as farms, as well as some hotels and resorts, breached UK fluoride restrictions.
The safety of private water supplies is the responsibility of the area’s relevant local authority.
Professor Alan Boobis, a toxicology expert at Imperial College London and government advisor, said levels of fluoride in water in the UK are not a health concern.
‘I do not believe that there are any specific health concerns from exposure to fluoride at the safety standard levels,’ he said.
However, he added that he didn’t believe universal fluoridation of water supplies in Britain is needed to prevent dental problems as background levels are high enough to achieve sufficient benefit.
Professor James Caulson, a toxicology expert at Cardiff University, agreed that levels of fluoride in water are of little cause for concern.
‘Patients exposed to doses of less than 5mg/kg body weight are unlikely to show features of toxicity (350 mg for an adult).
‘Daily doses of 20 to 80 mg over 10 to 20 years are associated with chronic fluorosis (staining of the teeth).
‘The upper limit of 1.5 mg/L (equivalent to 0.06 mg/kg for a 70 kg adult drinking three litres a day) is likely to be protective.’
However, he added that when considering these figures, drinking water is not the only source of many substances and people can consume more through their diet for example.
Professor Caulson added that specific figures can change for children and those with health conditions.
The main risk from lead in drinking water comes from the historical use of the metal in pipes before the dangers were realised in the 1970s.
Lead poisoning is a concern both in the immediate and the long term, especially for children.
The heavy metal is known to adversely impact mental development effecting their IQ later in life and is also suspected of increasing behavioural problems.
Lead poisoning can also lead to heart and kidney disease as well as contribute to high blood pressure in adults.
This level was found to have been breached 59 times across England in 2022, the majority (17) from Thames Water.
Professor Boobis said: ‘Exceedance of the safety standard for lead would only be of concern if this continued for some time, as lead builds up in the body over years, before it reaches levels adverse to health.
‘Of course, if the exceedance was substantial this would be of concern even short-term.’
Dubbed ‘forever chemicals’ for their ability to persist in the environment for years, these are a family of man-made compounds famed for their durability and stain resistant properties.
They have been used in a host of products from nonstick cookware, to clothes, packaging, cosmetics and even children’s toys.
But studies have since linked the chemicals to a variety of cancers, blood disorders, fertility problems and birth defects.
While these links are not definitive and research is ongoing, part of the concern is because PFAS are so ubiquitous in modern life and persist so long in the environment they could infiltrate water supplies, further increasing exposure.
The DWI currently sets a limit of 0.1μg/L for PFAS in UK tap water, with the body running a specific programme testing for levels in British water supplies.
It states: ‘The DWI is working closely with the UK Health Security Agency, the Environment Agency and Government, to adopt the most up to date information regarding standards and toxicology.’
It continues: ‘We are also carrying out our own research on analytical methods, and risk assessment to inform our decision making.’
Professor Boobis said unlike many of the other substances measured in British drinking supplies, research about the health impact of PFAS, and by extension the safe limit to consume, is ongoing, making it hard to calculate safe exposure limits.
That being said, he added: ‘PFAS take some time, years, to accumulate to maximum levels in the body.
‘Hence, the duration over which levels exceed the safety standards is important.
‘Personally, I do not worry about PFAS in my drinking water, but I can well understand that others will be concerned’.
Pesticides, chemicals made to kill unwanted weeds and vermin, can enter British water supplies via runoff from gardens and farms as well as other sources.
Given they are designed to kill and harm – unlike many of the substances listed – it’s unsurprising limits of pesticide content in water are strict.
The DWI sets a limit of 0.5μg/L for the total of amount of all pesticides in tap water, but this is set to 0.1μg/L for some specific types.
This latter limit was breached three times in 2022, all by water supplied by Northumbrian, Essex and Suffolk Water Ltd.
They related to the herbicides metazachlor and propyzamide, both chemicals commonly used in the farming of rapeseed.
While levels in water may sound concerning, Professor Boobis said the standard set is very safe with the DWI looking at a detection rate, where a substance can be spotted, not the safety limit for human exposure.
‘The safe levels based on health effects are both more than four orders of magnitude greater than the safety standard levels in water,’ he said.
‘Hence, there is no basis for concern over traces of these pesticides in water.’
Bacteria normally found in our guts can sometimes be found in tap water.
Both types measured by regulators (E.coli and Enterococci) can, in theory, make people ill, though for most people this is usually mild.
Instead their presence is normally measured as an indicator that water supplies may have been contaminated by human faecal matter.
As such the DWI sets the limit as 0 bacterium per 100ml, meaning that, at least in principle, no such bacteria should ever be detected in home supplies.
This isn’t the case though, with 27 breaches detected in 2022. The vast majority (12) were from Severn Trent Water, which supplies 4.5million homes and businesses in the Midlands.
And at least 5,577 Britons on private supplies drank water contaminated with faecal matter in 2022.
Professor Paul Hunter, a renowned infectious diseases expert from the University of East Anglia and who has advised the WHO on standards for drinking water, said these pathogens are unlikely to make a Briton ill but are good indicators of contamination.
‘They are generally not hazardous in themselves but are an indication that the water could have been contaminated by faecal matter,’ he said.
‘There are some types of E. coli that can cause potentially severe diarrhoea, but the most common type of this often wouldn’t show as a positive even if present.
‘So the presence of an indicator E. coli or Enterococcus does not mean that disease-causing bacteria are present just that we cannot say they are absent.
‘You could probably drink water with quite a few indicator bacteria in it without getting sick. But the indicators are present you could not rule it out.’
He added that another aspect that can muddy the data is often people contaminate their own tap water by accidently touching a tap opening while washing their hands after going to the toilet.
This puts the bacteria right at the opening of the tap and, therefore, isn’t an indicator that the supply itself is contaminated.
Professor Hunter added that British drinking water is, overall, very safe and the fact that only 27 tests came back positive, out of the 150,000-plus carried out, was, in fact, a ‘good’ result.
Minute traces of drugs have been found in raw water, the liquid that eventually becomes tap water.
This includes over-the-counter painkillers like ibuprofen and naproxen which were recorded at an average level of 0.01μg/L across England. Some places recorded levels as high as 0.24μg/L, however.
For comparison, typical ibuprofen pills are between 200-600mg each, and there is 1000μg in a single mg.
No data on levels of drugs in tap water was available.
While normally filtered out by processing, animal life like freshwater shrimp and fly larvae can occasionally enter the British tap water network.
Most of these organisms are microscopic and not visible to the naked eye though some animals are large enough that they can be seen if people look carefully enough.
They pose no danger to human health and in fact are often an indicator of ‘good quality’ water.
This chemical, most commonly encountered in swimming pools, is added to drinking water for the same reason – to keep it clean.
Chlorine is a disinfectant, meaning it kills potentially dangerous pathogens, like those mentioned above, that could otherwise make their way into British tap water.
A strict limit of 2mg/L is imposed on chlorine levels in tap water in the UK as this is considered safe.
Zero breaches in chlorine levels were recorded England in 2022.
Even if this was breached, experts consider it unlikely Britons would consume water with high levels of the chemical.
This is because the chemical has a particularly strong taste and smell, which would naturally alert a thirsty person that something was wrong with the water.
Professor Caulson said while chlorine can cause mild irritation, the level it would do is about 15 times higher than that typically found in drinking water.
Another metal, that similar to lead, can leach into tap water by its use in pipes.
Humans actually need a small amount of copper each day for health reasons but too much can make you very ill.
Symptoms of ingesting too much copper include stomach pain, nausea, vomiting, diarrhoea and can also trigger blue/green discolouration of the skin and hair.
These symptoms usually disappear once exposure to copper contaminated water stops.
The DWI set the copper limit in tap water at 2mg/L. This was breached twice in 2022.
Arsenic is one of the more frightening sounding substances that can appear in your water, albeit in trace quantities.
Arsenic, which occurs naturally in some water sources, is highly toxic to humans but is safe to consume at incredibly low levels.
The immediate effects of arsenic poisoning include vomiting, abdominal pain and diarrhoea.
In extreme cases, this is followed by a numbness and tingling of the limbs, muscle cramping and then death.
Arsenic exposure also carries longer term health concerns as it is known carcinogen, a substance that can cause cancer.
This generally takes the form of skin cancer, though it can also cause the disease to appear in the bladder and lungs.
Long-term exposure to arsenic in drinking water can also cause cardiovascular disease, developmental delays and cognitive problems in children.
The permitted level of arsenic in drinking water in the UK is 10 μg/L, a WHO standard.
This was breached once in 2022, by South East Water.
Although more commonly associated with murder mysteries and spy thrillers, cyanide can make its way into water supplies.
It mainly enters water as a consequence of industrial runoff.
Cyanide poisoning is extremely rapid and potentially deadly, with the chemical disrupting the body’s ability to use life-giving oxygen.
Exposure to small amounts of cyanide carries a host of symptoms including chest pain/tightness, confusion/dizziness and excitement, eye pain/tearing, breathing difficulties, headache, nausea or vomiting and abnormal heart rate.
Ingesting large amounts of cyanide is potentially deadly.
While incredibly dangerous, ingesting a tiny amount of cyanide is unlikely to do you harm, with your body able to process it before it causes any damage.
Due to its high toxicity, the amount of cyanide permitted in UK drinking water is incredibly low, just 50μg/L.
Zero cyanide breaches in UK tap water were detected in 2022.
Iron, when consumed as part of healthy diet, forms a crucial role in making red blood cells, which carry life-giving oxygen around the body.
However, too much can be bad for you and consuming over 20mg a day can cause constipation, nausea and vomiting and a stomach ache.
It can even be fatal, but this is generally a risk only for children who gain access to iron supplements and consume them in a short period of time.
In the UK, tap water is restricted to only having an iron level of 200μg/L.
This was breached 81 times in 2022, the majority of which was for United Utilities (27), which provides water in the North East of England.
Iron being in water generally isn’t considered a health risk however, as when present in high levels it turns the water a ruddy brown colour, generally putting people off drinking it.
The main risk from nickel exposure in drinking water actually isn’t from ingesting it but from rubbing it on your skin.
Water containing high levels of nickel can trigger contact dermatitis, a type of skin irritation becoming itchy, blistered, dry and cracked.
Nickel usually enters tap water at the home due to the use of the metal in plumbing fittings and plating on taps.
People can be advised to flush out any standing water in their taps which might have been in contact with the fitting for an extended time if they experience skin irritation after washing.
While nickel is toxic if ingested at high levels the amount in tap water, even at the levels that trigger contact dermatitis, is considered too low for this to be a realistic risk.
The acceptable nickel level in the UK is 20μg/L.
This was breached 43 times in 2022, with Northumbrian, Essex and Suffolk Water accounting for the majority of any water supplier (8).
You may be familiar with nitrates and nitrites from a furore of these chemicals being in foods like processed meats and potentially being linked to cancers.
Nitrates or nitrites are used in processed meat to help increase the shelf-life of cold cuts, and give ham its alluringly tangy taste and fresh, pink hue.
Nitrate is also found naturally in vegetables, with the highest concentrations occurring in leafy vegetables like spinach and lettuce.
As they can be located in the soil, either naturally or via fertiliser, they can also leech into water supplies, and by extension tap water.
However, experts say any cancer concerns relating to these substances in tap water are unnecessary.
The carcinogenic concerns relate to a separate compound called nitrosamines created when nitrates or nitrites encounter proteins or heat, such as frying up some bacon.
Therefore, the levels in water, which are low anyway, aren’t considered enough to trigger health concerns for cancer specifically.
Levels of nitrate and nitrite in water are carefully monitored.
Methaemoglobinaemia, also called ‘blue baby syndrome’, is an extremely rare and potentially fatal condition that can occur when a very young child ingests too much nitrate.
Upon doing so it is converted into nitrite in the child’s stomach where upon being absorbed by the body interferes with the distribution of oxygen turning a baby ‘blue’.
There have been no cases of methaemoglobinaemia reported in the UK since the 1950s, with the last case being seen in child who drank from a private well, not a public water supply.
Acceptable levels of nitrate in drinking water in the UK is 50mg/L whereas for nitrites it’s 10-times smaller just 0.5mg/L.
No breaches were recorded for the former in 2022 but nitrite levels were exceeded thrice.
Professor Gunter Kuhnle, a food scientist based at Reading University, said the levels of nitrates and nitrites in water ‘don’t raise any cause for concern’.
Of all substances in tap water listed, tritium is likely to be one most Britons have never heard of, but it’s one with an explosive history.
Tritium is a rare and radioactive isotope that is a byproduct of nuclear explosions and nuclear reactors.
It does also occur naturally from rare chemical interactions in the upper atmosphere in addition to man-made activities which cause it to leech into water supplies.
The Chernobyl and Fukushima meltdowns are considered to have unleashed a large amount of tritium into the environment, in addition to the small but more regular leaks from nuclear power generation.
While it naturally decays levels of global tritium are considered higher than normal in part because of the legacy of nuclear bomb testing over the past century, levels that will take many years to return to normal.
Estimates on when this will happen vary, some have said levels should return to ‘normal’ by as early as 2030, whereas others put it at 2098.
As with any radioactive substance the main concern surrounding tritium is cancer.
However, while debate on the exact risk is debated, the levels in water are considered low enough to not be a risk to human health.
This is partly because the human body regularly ‘flushes’ out water meaning tritium does not stay in the body long enough to do damage.
Concerns about tritium exposure usually relate to specific nuclear accidents or events which may cause a high level of exposure in a short period of time.
In the UK levels of tritium in water is set at 100Bq/L. Bq is short for Becquerel a unit of measurement for amounts of radioactive substances.
No breaches of the 100Bq/L limit were recorded in England in 2022.