Heavy metals in tap water: a concerning reality

In the game of 7 families that comprises the various contaminants present in tap water, we present to you the family of heavy metals.

Let us begin with the term itself: why “heavy”? This qualifier refers to the high density of these metals compared to water. By definition, a metal is considered heavy when it has a density greater than 5 g/cm³. This characteristic gives them a certain inertia in the environment, but also a capacity 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, mercury, cadmium, and arsenic. Although they are naturally present in the environment, their accumulation in drinking water can cause issues. These substances, in small doses, can infiltrate our daily lives and lead to serious health consequences. But where do they come from?

How do heavy metals end up in tap water?

So, how do these heavy metals appear in our drinking water?

• Industrial and agricultural pollution: discharges from factories and certain pesticides rich in heavy metals contaminate our groundwater.
• Old pipes: the lead from aging pipes deteriorates and ends up in your glass of water.
• Environmental residues: rainwater that washes over polluted areas can carry these elements into the water supply networks.

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

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

Do you want to know if your water is contaminated? Here are some solutions to find out:

• Consult water quality reports: each municipality publishes regular analyses on water quality. These reports are often available online or upon request at the town hall. To learn more, check our article:
  Tap water quality in France: we tell you everything you need to know
• Use home test kits: available in stores or online, these tests allow you to detect the presence of heavy metals such as lead or copper. Although they are not as precise as laboratory analyses, they provide a quick indication.
• Contact a certified laboratory: for accurate results, you can take a sample of your water and send it to a specialized laboratory. This option is more expensive but very reliable.
• Check your pipes: if you live in an old building, have your pipes examined by a professional. Old lead pipes are a major source of contamination.

What are the legal limits for heavy metal concentrations?

In France, tap water is one of the most monitored foods by health authorities. The concentrations of heavy metals are therefore meticulously inspected. Strict standards define the maximum allowable concentrations of heavy metals in drinking water to protect public health. Here are the main limits set by regulations:

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

These values are monitored through regular analyses conducted by health authorities. In case of exceedance, corrective measures are implemented to ensure 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 identified risks by category:

• Lead: often originating from old pipes, even in very low doses, it can lead to neurological problems, particularly in children.
• Mercury: it affects the nervous system and kidneys.
• Cadmium: it is known to cause kidney disorders and increase the risk of osteoporosis.
• Arsenic: recognized as a carcinogen, it can also be responsible for cardiovascular diseases.
• Nickel: Often linked to certain pipes, nickel can cause allergic reactions.
• Chrome: Chromium VI, particularly toxic, requires increased monitoring.

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

The main sources of lead and how to reduce them?

But while the concentrations of heavy metals are indeed well monitored at the exit of the distribution network, the path from the network to your glass of water is still conducive to contamination, particularly by lead.

Indeed, old lead pipes in certain homes remain a major source of contamination. In many old buildings, these conduits continue to exist, releasing lead into the water, especially when the pipes are damaged or when water stagnates.

To reduce exposure to lead, here are some practical tips:

• Let cold water run: Before consuming tap water, let it run for one or two minutes, especially after a period of inactivity in the pipes.
• Do not use hot water for cooking: Avoid consuming hot tap water, as it dissolves more lead.
• Replace lead pipes: If possible, consider modernizing your installations. Subsidies may be available to encourage this type of work.

Can heavy metals be removed from tap water?

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

Some solutions, such as filter jugs, claim to eliminate them, but their effectiveness remains highly debated. The activated carbon filters present in these jugs, for example, are commonly used to remove chlorine, pesticides, and certain heavy metals. However, they do not eliminate bacteria, viruses, or all heavy metals. This article from Que Choisir will tell you more: https://www.quechoisir.org/actualite-carafes-filtrantes-inutiles-voire-pire-n25672/

But again, there is activated carbon and activated carbon… The quality differences of filters using this process vary greatly depending on the source of the carbon. And the one found in filter jugs is generally of poor quality.

More advanced systems, such as reverse osmosis, are more effective. This process uses a semi-permeable membrane to remove unwanted particles present in the water, including heavy metals and nitrates. However, it is expensive, requires sufficient water pressure to operate, and generates a certain amount of wastewater during the filtration process. Finally, while osmosis systems are effective in their filtration process, paradoxically, they are too effective! Indeed, in addition to contaminants, they also remove beneficial minerals such as magnesium or calcium!

See our article: A water osmosis system, for what use?

Ceramic filters, on the other hand, are effective in removing microorganisms and certain impurities, but their ability to retain heavy metals depends on their specific design.
Finally, distillation systems can effectively eliminate dissolved salts, heavy metals, and certain chemicals. However, they consume a lot of energy to heat the water and do not remove volatile organic compounds that may evaporate with the water.

Conclusion: caution and vigilance

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