Heavy metals in tap water: a worrying reality

In the game of the 7 families that make up the different contaminants present in tap water, we present the family of heavy metals.

Let's start with the term itself: why 'heavy'? This term refers to the high density of these metals in relation to water. By definition, a metal is said to be heavy when it has a density greater than 5 g/cm³.. This characteristic gives them a certain inertia in the environment, but also an ability to accumulate in living organisms. This explains why they can pose long-term problems when present in our drinking water.

Heavy metals include elements such as lead, the mercury, the cadmium or thearsenic. Although they occur naturally in the environment, their accumulation in drinking water can cause problems. In small doses, these substances can infiltrate our daily lives and have serious consequences for our health. But where do they come from?

How do heavy metals end up in tap water?

So how do these heavy metals make their appearance in our drinking water?

Industrial and agricultural pollution: factory waste and certain pesticides rich in heavy metals contaminate our water tables.
Old pipes : Lead from ageing pipes degrades and ends up in your glass of water.
Environmental residues : rainwater washing over polluted areas can carry these elements into water supply networks.

In other words, it's not the water itself that's the problem, but everything it encounters along the way.

How can I tell if my tap water contains heavy metals?

Want to know if your water is contaminated? Here are a few ways to find out:

View water quality reports : Each local authority publishes regular water quality analyses. These reports are often available online or on request from the town hall. To find out more, read our article :
Tap water quality in France: we tell you everything you need to know
Use home-made test kits: Available commercially or online, these tests can detect the presence of heavy metals such as lead or copper. Although they are not as accurate as laboratory analyses, they provide a rapid indication.
Use a certified laboratory: For accurate results, you can take a sample of your water and send it to a specialist laboratory. This option is more expensive, but very reliable.
Check your pipes: if you live in an old home, have your pipes examined by a professional. Old lead pipes are a major source of contamination.

What are the legal concentration limits for heavy metals?

In France, tap water is one of the foods most closely monitored by the health authorities. Visit concentrations in heavy metals are of course scrupulously inspected. From strict standards define the maximum permitted concentrations of heavy metals in drinking water, in order to protect public health. Here are the main limits set by the regulations:

Lead (Pb): 10 micrograms per litre (µg/L).
Mercury (Hg): 1 µg/L.
Cadmium (Cd): 5 µg/L.
Arsenic (As): 10 µg/L.
Nickel (Ni): 20 µg/L.
Chromium (Cr): 25 µg/L (with a tolerance of up to 50 µg/L until 2035).

These values are monitored using regular analyses carried out by the health authorities. If levels are exceeded, corrective measures are implemented to guarantee consumer safety.

Health impacts: should we be concerned?

Protecting yourself against the presence of heavy metals in tap water is essential for your health. Here are the risks identified by category:

Lead : It often comes from old pipes, and even very small doses can cause neurological problems, particularly in children.
Mercury : it affects the nervous system and kidneys.
Cadmium : it is known to cause kidney problems and increase the risk of osteoporosis.
Arsenic : recognised as a carcinogen, it can also cause cardiovascular disease.
Nickel : Often linked to certain pipes, nickel can cause allergic reactions.
Chromium : Chromium VI, which is particularly toxic, requires closer monitoring.

The effects are often invisible in the short term, but accumulate over time. Did you say sneaky?

The main sources of lead and how can they be reduced?

But while concentrations of heavy metals are indeed well monitored at the end of the distribution network, the fact remains that the journey from the network to your glass of water is still open to contamination, particularly by lead.

That's right, old lead pipes are still a major source of contamination. In many older homesHowever, these pipes continue to exist, releasing lead into the water, especially when the pipes are damaged or the water stagnates.

To reduce exposure to lead, here are a few practical tips:

Run the cold water: Before drinking tap water, let it run for a minute or two, especially after a period of inactivity in the pipes.
Do not use hot water for cooking: Avoid drinking hot tap water, as it dissolves more lead.
Replace lead pipes : If possible, consider modernising your installations. Grants may be available to encourage this type of work.

Can heavy metals be removed from tap water?

Ah, the big question. Unfortunately, it's not as easy as boiling water. Heavy metals resist conventional methods domestic purification.

Some solutions, such as filter jugsThey claim to eliminate them, but their effectiveness remains highly debated. Filters with activated carbon present in these carafes, for example, are commonly used to eliminate the chlorinepesticides and certain heavy metals. However, it is important to note that they do not eliminate bacteria, viruses or heavy metals. This article from Que Choisir will tell you more: https://www.quechoisir.org/actualite-carafes-filtrantes-inutiles-voire-pire-n25672/

But then again, there's activated carbon and activated carbon... The differences in the quality of filters using this process vary greatly depending on the source of the carbon. And the charcoal found in filter carafes is generally of poor quality.

More advanced systems, such as thereverse osmosisare more effective. This process uses a semi-permeable membrane to remove unwanted particles from the water, including heavy metals and nitrates. However, it is expensiverequires sufficient water pressure to operate and generates a certain amount of electricity.wasted water during the filtration process. Finally, although osmosis systems are efficient in their filtration process, they are paradoxically too efficient! In fact, in addition to the contaminants, they also remove good minerals such as magnesium or calcium!

See our article: What is a water osmosis unit used for?

The ceramic filtersare effective at eliminating micro-organisms and certain impurities, but their ability to retain heavy metals depends on their specific design. Finally, the distillation systems can effectively remove dissolved salts, heavy metals and certain chemicals. However, it is important to note that they consume a lot of energy to heat water and do not remove volatile organic compounds that can evaporate with the water.

Conclusion: caution and vigilance

Tap water in France is generally of good quality, but the potential presence of heavy metals is not to be taken lightly. Adopt the right reflexes, equip yourself properly and don't hesitate to check your pipes. After all, water is life!

Article written on 27/12/2024 by Saadi Brahmi - CEO Solable - As a sustainable technology innovator, I am committed to pushing back the boundaries of technology to transform and enrich our interaction with the environment.