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Nutrition and daily life

Water safety: drinking water, ice and boiling

Water matters as much as food, and germs can travel in it too. During treatment the water you drink, the ice you use and the water you cook with should be safe. This section explains which water counts as safe.

Last updated: ~1 min read
A kettle at a rolling boil.
Figure 1.Boiling — Water safety: drinking water, ice and boiling

01Short answer

For drinking, use water your team considers safe: sealed bottled water, or water brought to a rolling boil for at least 1 minute and cooled. Avoid water from wells, springs, rivers and untested sources. Make ice from safe water too, and avoid iced drinks in cafés and on the street. Home water filters do not always remove germs. Use the same water for brushing teeth if your team advises it. Keep jugs and kettles clean.

02Simple explanation

Sealed bottled or boiled.

No well or spring water.

Ice from safe water too.

A filter is not always enough.

03Scientific explanation

WHO: contaminated drinking water spreads diarrhoea, typhoid and hepatitis A; a rolling boil reliably kills germs.

WHO: foodborne illness is more severe in people with weakened immunity; the five keys are keep clean, separate, cook thoroughly, keep food at safe temperatures, and use safe water and raw materials.

04What happens in the body?

Tap water

Safe in some cities and not in others; ask your team for local advice.

Bottled water and a clean glass.
Figure 2.A sealed bottle — Water safety: drinking water, ice and boiling

Travel

In unfamiliar places drink only sealed bottled water.

Well water aside, boiled water in front.
Figure 3.Well water aside — Water safety: drinking water, ice and boiling

Neutropenia

When neutrophils are low, even ordinary germs can cause serious infection, which is why the rules are stricter.

General rules

This section is part of the general food-safety rules in “Handwashing: the simplest protection” and “Eggs and dairy: safe choices” and “Food safety: four simple rules”.

05Safety: four steps

Check, swap the risky, prepare properly, use in time.

Check — Date and condition.1CheckDate and condition.
Swap — A safe choice.2SwapA safe choice.
Prepare — Clean and thorough.3PrepareClean and thorough.
In time — No delay.4In timeNo delay.
CleanHands and surfaces.
CookGerms die.
ColdGrowth slows.

06Key points at a glance

TopicIn brief
Tap waterSafe in some cities and not in others; ask your team for local advice.
TravelIn unfamiliar places drink only sealed bottled water.
NeutropeniaWhen neutrophils are low, even ordinary germs can cause serious infection, which is why the rules are stricter.
General rulesThis section is part of the general food-safety rules in “Handwashing: the simplest protection” and “Eggs and dairy: safe choices” and “Food safety: four simple rules”.

07Key terms

Rolling boil
Continuous boiling with large bubbles.
Cryptosporidium
A waterborne parasite resistant to chlorine.
Foodborne infection
An infection spread through food or water.
Neutropenia
Low neutrophils.

08Key points

  • A safe source.
  • Ice matters too.
  • When in doubt, boil.
  • When in doubt, throw it out.
  • Call if you have a fever.

09Frequently asked questions

Is mineral water OK?

In a sealed bottle, usually yes.

Is a filter enough?

Not every filter; unless it is proven to remove germs, boil.

Are these rules for ever?

No. They are usually relaxed as blood counts recover; your team will say.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. Is mineral water OK?

  2. Is a filter enough?

  3. Are these rules for ever?

My questions

12Sources

  1. World Health Organization. Drinking-water fact sheet
  2. World Health Organization. Five Keys to Safer Food manual
  3. World Health Organization. Food safety fact sheet
  4. U.S. Food and Drug Administration. Safe Food Handling
  5. National Cancer Institute. Eating Hints: Before, During, and After Cancer Treatment
  6. NIH Office of Dietary Supplements. Vitamin D Fact Sheet
  7. MedlinePlus (U.S. National Library of Medicine). Nutrition
  8. NHS. Vitamins and minerals
  9. MedlinePlus (U.S. National Library of Medicine). Ferritin Blood Test
  10. World Cancer Research Fund. Cancer Prevention Recommendations
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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