How often can you boil water?

Do you boil the water in your kettle until it runs out, or do you change it after every cup? If you search online for whether you can reboil cooled water, you’ll find that the answers vary quite a bit. From reassurances to frightening messages: it turns out to be a frequently asked question.

Dangerous Toxins

One story going around is that the composition of water is said to be changed when cooled water is boiled again. Hazardous substances such as arsenic, nitrates and fluoride would collect in the water. Nitrates exposed to high temperatures can cause cancer and a high intake of arsenic can also cause serious health problems. Excessive fluoride intake increases the risk of neurological problems and children may experience cognitive delays. That doesn’t sound pleasant at all.

arsenic poisoning

But whether the toxins are also dangerous in the amount you can find in the water is the question. It turns out: if you really want to get acute arsenic poisoning, according to Australian scientists a person weighing 75 kilograms should ingest about 0.45 grams of arsenic. A liter of water would contain only 50 to 100 micrograms of the harmful substance (that is one millionth of a gram). A cup filled with arsenic would then equal 10,000 liters of boiled water. It is of course impossible to drink that many liters of water in one sitting.

Nitrates

The amounts of nitrates and fluoride can also be questioned. In the case of nitrates, they can only become harmful when exposed to high temperatures, but another requirement is that the water should already be polluted. Becoming in the Netherlands high demands to the quality of drinking water, minimizing the risk of pollution by nitrates.

Fluoride

The same is true for fluoride. In the Netherlands, the maximum amount allowed fluoride in water 1.1 milligrams per liter. Only a much higher amount (think: 2 to 10 milligrams per litre) can human health be endangered, according to the study. American research.

Toxic enough?

So: can you boil cooled water again? Yes, that’s possible. In the Netherlands, the drinking water is clean enough for this. The toxins can collect in the water, but only with an ingestion of 10,000 liters of re-boiled water is there a risk of poisoning. So you can just put that water on again.

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