The emerging science around water contamination can feel alarming. In November 2023 the Drinking Water Inspectorate (DWI), which is responsible for regulating the public water supply companies in England and Wales, detected 11,853 samples of water which contain potentially harmful “forever chemicals”.
Labelled this because they never break down, poly and perfluorinated alkyl substances – PFAS for short – have tainted our humble tap water. There are thought to be more than 4700 types of PFAS and studies have found that some PFAS are associated with a higher risk of fertility problems, cancer and thyroid disease.
Sadly, it’s not as simple as reaching for bottled mineral or spring water instead. A new study by the University of Columbia found that a bottle of water can contain a quarter of a million pieces of plastic. Scientists have created a new category called nanoplastics to refer to the plastic pollution that happens when microplastics break down even further.
“People are doing their best to try and keep us safe but we have contaminated things on a greater scale than we really realised,” says Dr David Megson, a senior lecturer in chemistry and environmental forensics at Manchester Metropolitan University.
“It’s only now that we’re starting to understand the science behind these things as we’ve been struggling to get the mechanisms for testing PFAS in place.”
With water contamination causing concern whether we drink it from the tap or a bottle, what’s the best option?
Boudicca Fox-Leonard: "The emerging science around water contamination can feel alarming." Photo / Stephen Parker
It’s a debate that Dr Megson has with himself constantly. “It’s a minefield,” he says. “And you’ve got to be careful not to put people off drinking water.” So what are our options?
Affectionately known by many as “council pop”, each water company responsible for tap water in the UK is held to the same guidelines.
“There are strict regulations on what happens to our drinking water, but depending on your area and the water company they use a variety of processes,” says Dr Charlotte Lloyd, an environmental chemist at the University of Bristol. There are a list of pollutants and chemicals that water companies test for, however, what concerns Dr Lloyd are the unknown chemicals.
“There are regulations on what is deemed safe, but we could argue whether the numbers are right and the list is long enough. There are lots of things we don’t measure either because we don’t know they are there or they are not on the list. I think we need to constantly review what’s on the list.”
The current Drinking Water Directive, which is available on the UK Drinking Water Inspectorate website, lists the chemicals which are monitored. “But there are interesting clauses such as for pesticides where it says that the list of pesticides monitored should include those that they think are relevant for that supply area – meaning that they are only monitoring the correct things if they have checked regularly to see what is there.”
In some areas (not all as it depends on the natural levels of fluoride in the source water) extra fluoride is added to water supplies (up to 1 milligram per litre) to increase intake and prevent tooth decay. While links to poor cognitive development in children might seem concerning, Dr Lloyd says fluoride levels in tap water are closely monitored by water companies as instructed by the DWI.
The legal limit for fluoride in drinking water is 1.5 milligram per litre. However a harmful dose would be much higher, says Dr Lloyd. “There is much more fluoride in toothpaste for example.”
Oestrogen is an example of a whole range of chemicals that makes its way into our waters which could potentially cause problems. “There are many types of oestrogens, both synthetic (like that used in the contraceptive pill) and a range of natural sources as well,” explains Dr Lloyd. “There are also many chemicals which are referred to as “endocrine disrupting”, these are chemicals which mimic the behaviour of hormones in our body – things like bis-phenol A and phthalates (both plastic additives) – and so can have similar effects to oestrogens in the water.”
Some of these will be removed during water treatment, but low levels are likely to still prevail. “In terms of the safe drinking water limit and hormones, these will be set according to our best current knowledge about safe limits for intake of these compounds,” says Dr Lloyd.
What it doesn’t necessarily reflect is what happens if this low level intake builds up over time and starts having detrimental impacts. A 2009 study by Brunel University found male fish were being affected by anti-androgens, used in a number of medicines including cancer treatments and pesticides used in agriculture, and warned that it could also be contributing to a reduction in human sperm counts, which have fallen in the past 50 years.
Another growing area of concern is trihalomethanes (THMs), the name for disinfection byproducts, which have been linked to bladder cancer. “These are compounds that are formed during the water treatment process. We use chlorine in order to disinfect the water for drinking and this can impact on the organic matter in the water.
“Waters which contain high concentrations of organic matter, this could be natural from waters that drain peatlands for example, or areas where there is organic pollution from sources such as agriculture or sewage, you have higher potential for the creation of carcinogenic by-products during the drinking water treatment process.”
This sounds alarming, yet, says Dr Lloyd: “In a global context our drinking water is still good. There is no need to panic.”
Tap water will usually have a residual concentration of chlorine in it to ensure that it is safe. While the amount will be deemed safe, it might affect taste. Filtering can help with this.
Regionality does make a difference, says Dr Megson. London and the South East is a hard water area, and that can affect taste more than anything else. Filtering might help to make it more palatable.
“I have quite a lot of faith in the water where I am geographically in Manchester, because it comes from a reservoir. If I lived in London I would be filtering. The water in that region comes partly from underlying aquifers [groundwater under London] and those areas have been shown to have problems with PFAS. Those water companies know about it and are blending their water to make it as safe as possible.”
Some choose to filter their water to improve the taste. Photo / 123rf
Many of Dr Lloyd’s colleagues filter their water, although she admits to not being organised enough. “A fellow chemist and colleague has an activated carbon filter on his kitchen tap.” This will help take out some of the trihalomethanes left in the water.
While filter jugs made out of plastic may also reduce contaminants, the plastic itself is a concern. “You can get glass jugs now, but for most there’s still always some element of the filter that passes the water through plastic.”
Again it is a choice of choosing the best of the worst options. Although if you do decide to use a plastic filter jug, Dr Megson cautions against ever putting it in the dishwasher.
Hard and soft water: What’s the difference?
The concentration of certain minerals is what creates the “hardness” of water. Surface water tends to be soft, containing fewer minerals, and acidic by nature, while groundwater tends to be harder. Hard water tends to contain higher levels of calcium and magnesium. While some people complain this gives the water a chalky mouthfeel, it can actually be beneficial for you and there are no serious adverse health risks associated with drinking hard water.
Soft water, meanwhile, tends to have higher concentrations of sodium, which is a bigger concern for people with high blood pressure. A costly solution to this is to use a reverse osmosis system that is effective at removing or reducing sodium.
Is bottled water better for our health?
In 2022, the bottled water market was worth £2.07 billion ($4.29 billion), with Highland Spring water the most frequently selected brand.
There are three distinct types of water that may be “bottled” as identified by Defra (the Department for Environment, Food and Rural Affairs): natural mineral water, spring water and bottled drinking water. Regulation is the responsibility of local authorities where the water is sourced.
If the bottled water is from outside the UK it must be compliant with the compositional and safety standards of the country of destination. Natural mineral water from outside the UK, cannot be marketed as such unless it is recognised by the relevant UK authority; Defra, Food Standards Scotland and Food Standards Agency in Wales.
Mineral water
This is water that has filtered down through rocks, purifying it and adding minerals naturally, which is then taken directly from deep underground by boreholes drilled far into the ground and bottled at source; it certainly sounds healthier and tastier than London’s much recycled tap water.
However, despite the perception that mineral water is pristine and uncontaminated, Dr Lloyd says: “It is likely that the science is just not there at the moment to confirm if there is contamination of mineral waters with PFAS.”
In the wake of new research finding microplastics in water bottles, experts have unpacked the science behind drinking water. Photo / 123rf
To meet requirements of the definition, all UK mineral water must contain consistent mineral composition including calcium, magnesium, potassium and sulphates and use only five permitted treatments to improve the water: filtration or decanting; removal of free carbon dioxide; adding carbon dioxide to produce sparkling natural mineral water; ozone-enriched air oxidation to separate compounds of iron, manganese, sulphur and arsenic from water when they occur naturally at source; and activated alumina to remove fluoride.
It takes two years to be officially recognised as mineral water through a local authority, during which time it is repeatedly analysed.
“They will be continually testing their source to make sure nothing is getting into that ground water source, and there will be a list of things they have to look for. But if it’s not on the list it won’t be tested for because it is expensive to test,” says Dr Lloyd.
Her work looking at river pollution hasn’t convinced her that springs are guaranteed to be contaminate-free.
“What we see from river water is that there are chemicals that are human derived in every river, even in the most pristine stream we still find plastic chemicals. When you think about groundwater, where a lot of spring water will come from, there’s no guarantee that those springs are any cleaner than our processed water. Of course there are regulations and they have to be tested but I wouldn’t say they are any cleaner or any better.”
In the United States, a 2020 study by Consumer Reports found toxic PFAS chemicals in several popular water brands, especially carbonated ones.
Finding true mineral water is difficult in our polluted world. “The best water is probably buried in Antarctica, stuff that’s been locked away for thousands of years where we’ve not had a chance to contaminate it,” says Dr Megson. “And the last thing I would recommend is going there, digging up the ice and using it for our drinking water.”
Spring water
Similar to mineral water, the term spring is used to refer to water collected directly from a natural source, typically far underground in natural aquifers where the spring water rises to the surface. Unlike natural mineral water, there is no formal recognition process required for spring water, although it must still be registered with the local authority.
Many natural mineral waters begin their lives as spring waters trading as such during the two-year testing period. Unlike natural mineral waters, spring waters may undergo permitted treatments.
Bottled water
A bottle of water that is labelled neither as spring or natural mineral water is called table water. Table water may come from more than one source and may include the public water supply. In 2004 Coca-Cola faced ridicule after its Dasani branded bottled water was revealed as being treated tap water from Sidcup, Kent. It was after a batch was contaminated with levels of bromate, a suspected human carcinogen that the brand was withdrawn from the market.
Bottled water can be treated to meet the compositional and microbiological requirements of the regulations.
Water bottled in plastic is often at risk of contamination from different chemicals. Photo / 123rf
Some companies may also add mineral salts to their waters to replace those minerals lost during treatments or to enhance those which already exist.
An example might be a can of water that extols the virtues of added magnesium, calcium and potassium: “I would be asking to know where this water comes from and what they’re doing to it. It wouldn’t seduce me,” says Dr Lloyd.
The plastic problem
Approximately 85 per cent of bottles used for bottled water were made from plastic in 2019.
Even if your mineral water does come from an unpolluted source, if you buy it in plastic, Dr Megson says that causes its own problems.
“When it goes through that processing system a lot of them have polytetrafluoroethylene (PTFE) plastic that’s made out of fluorinated chains that are very similar to PFAS. So you can have PFAS leaking into your nice, fresh spring water from your bottling manufacturer process. It’s very difficult to be free.”
Dr Megson states that you should avoid reusing plastic bottles, and certainly not put them in a dishwasher or leave them in the sun, as this causes the plastic to degrade.
“All those chemicals are coming out and contaminating your water.”
While glass is better, Dr Megson is sceptical of spending vast amounts of money on brands such as Voss from Norway.
“From a sustainability perspective we already have the infrastructure for our tap water and it’s heavily regulated to get us down to minimum safe levels. I don’t think we should be importing our drinking water.”
Both Dr Megson and Dr Lloyd favour carrying metal water bottles and drinking tap water.
“When it comes to bottled water there’s no evidence that it’s any cleaner than our processed tap water,” says Dr Lloyd. “I would certainly be concerned about drinking water that comes in plastic, personally. There will be places in the world where they have to rely on bottled water but in this country we are not in that situation.”
