How safe is tap water to drink?
Domestic tap water should be clear, odourless and, according to the Water Industry Act 1991, “wholesome”.
To ensure that the water coming from your tap is the best possible quality and that strict safety limits are adhered to, water companies must test customers’ water quality in accordance with UK law, EU member state directives, and national standards and regulations.
Broadly speaking, drinking water is routinely tested for:
- chemicals e.g. nitrate and pesticides
- metals such e.g. lead, copper
- water taste and appearance
For micro-organisms such as the E.Coli bacteria, service reservoirs and water treatment works must follow national regulations and ensure that no E.Coli is present. EU law goes further to ensure that none of the same bacteria is present when you turn your tap on.
The level of contaminants allowed in drinking water, for it to be deemed safe, varies as to the particular contaminant.
Under national and European standards for example, from the water treatment facility to your tap your water supply should be completely free of E.Coli.
However, tiny amounts of more than 30 other chemical elements can be present, including arsenic, copper, cyanide, cadmium, chromium, fluoride, lead, nickel and mercury – along with pesticides.
Water companies test for contaminants using the following units of measurement:
1 milligram/litre (mg/l)
This means 1 part in 1,000,000 (or one part in a million).
1 microgram/litre (ug/l)
This represents 1 part in 1,000,000,000 (or one part in a billion).
There are many different ways that contaminants can enter drinking water. For example:
- Arsenic can get into water having been carried through the air by volcanoes (or by burning coal).
- Lead can be found in water if old homes still have lead pipes.
- Pesticides can be present due to rainwater touching sprayed crops and leaving fields through drainage.
Effectively, as part of the hydrological cycle, water is exposed to both natural processes and human activity.
Because of this, water companies can only provide you with water that is deemed safe to drink, within legal and regulatory frameworks and acceptable limits. But consumers also have a responsibility towards the quality of the water supplied to their homes.
According to the Drinking Water Inspectorate, ‘the part of the service pipe leading from the stop valve outside your property to the point where it enters your home is the responsibility of the owner’ along with, of course, all the plumbing inside your home.
Read on to find out more about the contaminants that may be present in your tap water.
Tiny traces of chemicals may be present in tap water. This may be because of natural and/or industrial processes, spills, erosion of water pipes or thanks to the by-products of modern farming practices as seen with pesticides.
The presence of certain chemicals in water is measured in micrograms per litre (µg/l) – parts per billion, or milligrams per litre (mg/l) – parts per million.
According to the Drinking Water Inspectorate, ‘the vast majority of… regulated chemicals are never found in drinking water in England and Wales at levels approaching or exceeding the standards’.
Nevertheless, the contaminants listed in the Water Supply (Water Quality) Regulations 2008 are below:
Although not conclusive, some studies have indicated a link between Alzheimer’s and aluminium. In Camelford, Cornwall, a historical 5-day treatment plant poisoning occurred. 20,000 people experienced short term nausea, vomiting and diarrhoea, ulcers, rashes and arthritic pain.
Ammonia has a toxic effect on healthy humans only if the intake becomes higher than the capacity to detoxify.
The International Agency for Research on Cancer (IARC) determined antimony trioxide as possibly cancer-causing. As well as water, antimony can get into the body from breathing factory dust or eating food.
Long-term exposure to arsenic can lead to skin, lung, and bladder cancer. Links to heart disease, low verbal IQ and long-term memory have also been reported. Short term exposure has seen vomiting, diarrhoea, abdominal pain and hair loss. In babies, reduced birth weights, miscarriages, premature birth have been known.
In 2018, the International Agency for Research on Cancer (IARC) pointed to evidence classifying benzene as cancer-causing. It can also cause acute myeloid leukaemia in adults, with links to non-Hodgkin lymphoma. Other suggested links include: Chronic lymphoid leukaemia, myelomas, chronic myeloid leukaemia, lung cancer, and acute myeloid leukaemia in children.
Benzo(a)pyrene is considered one of the most toxic PAHs. It’s among several classified by the International Agency for Research on Cancer (IARC) as cancer-causing.
Exposure to large amounts of boron over a short period of time can affect the stomach, intestines, liver, kidney, and brain and can eventually lead to death.
If ingested, bromate can cause nausea, vomiting, abdominal pain, and diarrhoea. It can also cause the kidneys to stop producing urine, varying degrees of central nervous system depression, red blood cell disorder, and fluid in the lungs. Although most of these effects are reversible, irreversible effects include renal failure and deafness.
The International Agency for Research on Cancer (IARC) has said that cadmium and its compounds cause cancer. It is primarily associated with lung, prostate, and kidney cancers, and recently pancreatic cancer. It has also been associated with breast and urinary bladder cancer. Although, it is rarely detected in drinking water, most likely present due to plumbing fittings.
Healthy individuals can tolerate the intake of large quantities of chloride provided that there is an accompanying intake of fresh water. Little is known about the effect of prolonged intake of large amounts of chloride in the diet.
Of its different forms, Chromium VI causes skin problems, lung and nose cancer.
Clostridium Perfringens bacteria cause food poisoning. Like many poisonings, symptoms include intense abdominal cramps and diarrhoea.
Faecal coliform and E-Coli are sub-groups of total coliform bacteria. If coliform bacteria are present in drinking water, then disease-causing organisms may also be present.
Colony count tests are very important, and if missed, disease and illness-causing bacteria can go undetected in drinking water.
Corrosion in drinking water can make it go blue. The Drinking Water Inspectorate says it’s rare and only occurs when copper plumbing is relatively new. Although usually disappearing when the tap is run, copper can be toxic. Long-term high-level exposure can cause liver damage and gastrointestinal symptoms.
Copper can be toxic. Long-term high-level exposure can cause liver damage and gastrointestinal symptoms. Although rare, Wilson’s disease is a genetic disorder which stops the body removing excess copper. It affects the liver, kidneys, brain and corneas of the eyes. If untreated, Wison’s disease can cause severe brain damage, liver failure or even death.
The Drinking Water Inspectorate says that cyanide could be present in surface water after specific industrial contamination. Cyanide has been used as a poison, causing certain death to those who take it.
In 1999, the International Agency for Research on Cancer (IARC) classified 1,2-dichloroethane as possibly cancer-causing. The Drinking Water Inspectorate says you can remove it with special water treatment.
Some E-Coli strains are beneficial (digesting food), while others are harmful. Certain strains can even be deadly. If found in drinking water, it must be removed immediately.
Minerals picked up by conductivity testing can be harmful to human health, especially in high concentrations.
Fever, chills, fatigue, headache, abdominal pain, pain or burning when you urinate, nausea, vomiting, chest pain when you breathe, stiff neck and bleeding gums
Excessive exposure to fluoride in pregnancy can lower a child’s IQ. When growing up it can lead to dental fluorosis causing while flecks, browning and corrosion. Fluoride can also damage nerve tissue and disrupts the body’s hormones. It can harm the thyroid gland and calcify the pineal gland which is believed to help regulate the body’s sleep and waking cycles.
Alpha particles cannot enter the body through your skin, but if they get inside you then they can cause extreme harm. The particles are large and heavy, and are much more dangerous than other forms of radiation. They cause cancer in humans.
8,000 times smaller than Alpha particles, they can penetrate skin and cause spontaneous mutation in DNA.
Although essential for human health, too much iron can lead to constipation, nausea, diarrhoea and vomiting. In extreme cases: liver disease, heart attacks and death.
Lead can disrupt the nervous system and destroy nerve tissues. It can accumulate in the body over time and heavy exposure might cause death. Children and unborn babies are the most vulnerable. It’s been linked to autism, reproductive problems and prostate cancer in men. The World Health Organisation says that no level of lead is acceptable in a child’s blood.
A small amount of manganese is essential to stay healthy. However, at high levels it can cause damage to the brain and affect the nervous system. In children, studies have suggested extremely high levels may affect brain development.
There is no cure for mercury poisoning, other than to reduce your exposure. It can cause brain damage, blindness, nerve damage, cognitive disability, impairment of motor functions, headaches, weakness, muscle atrophy, tremors, mood swings, memory loss, and skin rashes.
The International Agency for Research on Cancer (IARC) has determined nickel compounds cancer-causing. Some people suffer allergic reactions through skin contact. Earrings, bracelets, wristwatches and keys can cause irritation.
High concentrations can be an issue for infants. Blue baby syndrome (methaemoglobinaemia) is potentially fatal. A suggested link between colon, kidney, stomach, thyroid and ovarian cancer is also reported.
Like nitrates, nitrites are also thought to be a likely cause of cancer: glioma, thyroid and gastric cancers.
Whether smelly water proves harmful depends on what is causing the smell. Many bacteria are relatively harmless, but the odour could be caused by any number of more sinister sources.
There are 9 pesticides classified as causing cancer in humans, or probably/possibly doing so, with Pentachlorophenol being the most serious group 1 carcinogen.
Exposure to high pH can cause irritation to the eyes and skin. Low pH can result in similar effects, below 4, eye redness and irritation has been reported, and when less than 2.5, damage to certain tissues is irreversible. Corrosion of pipes can cause indirect effects.
Around 20 PAHs are on the IARC cancer classification list, including Benzo(a)pyrene, one of the most toxic polycyclic aromatic hydrocarbons. It is considered one of the most toxic, capable of causing lung, skin and bladder cancer.
Most exposure comes from breathing in radon decay when drinking water is exposed to the air. Breathing in radon can cause lung cancer and drinking it can cause other internal organ cancers. The US EPA estimates radon to cause 168 cancer deaths per year.
In 1991 the International Agency for Research on Cancer classified chlorinated drinking water as Group 3. Agents in Group 3 have not been cleared as non-cancerous or safe overall, but often means that further research is needed.
Too much selenium could be toxic to cells and may cause cancer. The World Health Organisation reported a case of toxic selenium in drinking water. A family was exposed for three months to well water high in selenium. They suffered the loss of hair, weakened nails and mental health symptoms.
Too much sodium in the body raises blood pressure, putting a strain on your heart, increasing risk of osteoporosis, stomach cancer and kidney disease. Acute effects of sodium can include nausea, convulsions, vomiting, muscular twitching and rigidity, and cerebral and pulmonary oedema.
Various studies indicate a laxative effect from tap water containing higher level of sulphate.
A number of potentially harmful pollutants can change the taste of your drinking water: bacteria, copper leaching from the pipes, mercury, lead, arsenic, iron to name a few.
The effects of drinking water contaminated over a short period may result in stomach pain, diarrhoea, sickness, breathing difficulties, headache, dizziness, coordination problems, confusion and tiredness. Liver and kidney damage can also occur. It is suspected of causing non-hodgkin lymphoma.
TOC does not directly create a health risk. However, in cases when non-oxygenated water is produced, toxic salts may be formed.
Trichloroethene can cause burning in the mouth, stomach pain, nausea and vomiting, headaches and dizziness followed by drowsiness and loss of coordination. In severe cases, abnormal heartbeat and comas are possible. Causes kidney cancer, liver cancer and non-Hodgkin lymphoma.
Tap water is the main exposure source of Bromodichloromethane, as it is formed from chlorine reacting with other matter in the water. It is suspected of causing cancer of the liver and kidney.
Tritium is harmful because it emits ionizing radiation. This kind of radiation has the potential to slightly increase the likelihood of cancer in someone’s lifetime. Tritium has leaked from 48 of the 65 nuclear sites in the US. In one case, leaking water contained 2,800 times the UK permitted limit.
Excessive turbidity can make water taste and look unappealing. It can also create shelter for pathogens and lead to waterborne bacteria, which can cause a variety of diseases.
It is not possible for the drinking water drawn from your tap to be perfectly pure and free of potentially harmful contaminants.
Although high by comparison with some countries, today’s UK drinking water standards still allow for very small amounts of contaminants to get into the system, despite complex treatment processes.
Of the contaminants regularly tested for in the UK, more than a third have been identified as being cancer-causing in humans by the International Agency for Research on Cancer (IARC).
The water-borne contaminants, as tested for by the Drinking Water Inspectorate, from which the IARC has identified links to cancer, are listed in alphabetical order below:
- Antimony (antimony trioxide)
- Causes acute myeloid leukaemia in adults
- Positive associations also observed with non-Hodgkin lymphoma, chronic lymphoid leukaemia, multiple myeloma, chronic myeloid leukaemia, acute myeloid leukaemia in children and lung cancer
- Bromodichloromethane (BDCM)
- Primarily associated with human lung, prostate, and kidney cancers, and recently pancreatic cancer. Also associated with cancers of the breast and urinary bladder.
• Chromium (VI) compounds are carcinogenic
• Chromium (VI) compounds cause lung cancer. Positive associations also observed with exposure and cancer of nose and nasal sinuses.
- Dibromochloromethane (also known as DBCM and chlorodibromomethane)
- Lead (inorganic)
- Lead (organic)
- Nickel (compounds)
- Nickel (elemental)
- Bromate (specifically Potassium Bromate)
- Selenium (and selenium compounds)
- Trichloroethene (also known as trichloroethylene)
- Causes kidney cancer. Correlations also observed with exposure and non-Hodgkin lymphoma and liver cancer
- Tetrachloromethane (also known as carbon tetrachloride)
- Vinyl chloride
- Causes liver cancers: angiosarcoma of the liver and hepatocellular carcinoma
- Also potentially associated with brain cancer, lymphoma, leukaemia, and soft tissue cancers.
The Natural History Museum has described microplastics as the one of the greatest manmade disasters of our time.
They have been found all over the world – even in Arctic snow and seemingly have the ability to get into the atmosphere and travel around the planet, making microplastics as ubiquitous as water itself.
What are microplastics?
Microplastics are tiny pieces of plastic, smaller than 5mm. They are divided into two types: primary and secondary microplastics.
Primary microplastics can include microbeads in shower gels and nylon in clothing, while secondary microplastics often break down from larger plastics due to sunlight and weathering.
But microplastics from all kinds of synthetic products are a worldwide problem. Research by the not-for-profit Orb Media found that 83 per cent of waters sampled had microscopic plastic fibres in them. In the US, that figure was 94 per cent and in Europe, 72 per cent.
The University of Hull reviewed six studies on microplastics in tap water, and reported the highest concentration of microplastics to be 628 fragments of plastic per litre of tap water. They estimated this as being equivalent to a human adult consuming 458,000 pieces of microplastic per year – or a credit card a week! That can’t be good for you.
While the presence of plastic throughout the planet is not in doubt, our understanding about the effects of microplastics on the environment, wildlife and human health continues to be less clear. More research is needed. According to the US Library of Medicine, microplastics both absorb and give off chemicals and harmful pollutants. These are said to include persistent organic pollutants (POPs), polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs).
A 2020 paper suggested that microplastic may be involved in disrupting the immune system, creating inflammation, generating abnormal tissue growth, or damaging the brain or nervous system.
The World Health Organisation has also echoed the need for greater knowledge while at the same time, calling for the rise in global plastic pollution to be stopped.
What is clear is that microplastics do collect in the human body. A 2020 study of deceased people’s organs uncovered dozens of types of microplastic. BPA, which has been associated with cancer, was detected in all of the samples, which were taken from organs such as the lungs, kidney and liver.
Meanwhile, research by the University of Newcastle, Australia, revealed in 2019 that on average, people globally can consume 5 grams of plastic per week and 250 grams per year – and that the largest source for ingesting microplastics is through bottled and tap water.
Before this, in 2018, scientists in Austria discovered microplastics in human faeces. Up to 9 different types of plastic were identified across eight study participants, who came from countries like the UK, Netherlands, Austria, Italy, Poland, Russia and Japan.