Humanitarian Health Action

FAQs: Japan nuclear concerns

September 2011


Water contamination

Can I drink the tap water in Japan?

  • Drinking tap water in Japan poses no immediate health risk
  • The Japanese authorities closely monitored the situation and issued advice, when needed, against consumption of tap water, including specific recommendations for infants. Essential hydration of infants should not be compromised in an attempt to reduce exposure to radionuclide contamination.
  • The standards adopted by the Japanese authorities for this emergency are precautionary. In the case of radioactive iodine the standard for adults is 300 Becquerels per litre in drinking-water. In the very unlikely scenario that drinking-water was contaminated and consumed for an entire year at this level, the additional radiation exposure from this water would be equivalent to natural background radiation during one year.
  • During the early phase of the emergency WHO urged people in the area to heed the advice of local authorities, as they have access to the latest measurements of radiation levels in water to compare against the standards for adults and children. Currently, restrictions of consumption of tap water have been lifted in all prefectures

Can radioactive contamination be removed from water?

  • Standard water treatment procedures may remove significant amounts of radioactive contaminants. Other options to reduce concentrations of radiation contaminants include controlled dilution of contaminated water with non-contaminated water.
  • Boiling water will not remove radioactive iodine.

Why do the guidance levels for radioactive Iodine-131 in drinking water vary?

The guidance levels found in different sets of recommendations vary because some apply to routine situations and others to emergency situations. The table below summarizes the guidance on radioactive Iodine-131 in drinking water and provides an indication of the equivalent exposure from routine activities.


Guideline name Advised maximum levels for radioactive activity in water (Bq/L) Approximate equivalent radiation exposure if consuming water at this activity level for a year
WHO Guidelines for Drinking-water Quality (1) 10 A New York - London flight
Japanese provisional (emergency) standard for adults (2) 300 One year's exposure to natural background radiation, or 10-15 chest X-rays
Japanese provisional (emergency) standard for infants (3) 100
IAEA Operational Intervention Level for nuclear emergencies (4) 3000 Not applicable. The advised maximum level should be used only to trigger action in the early stages of the emergency

(1) WHO Guidelines for Drinking-water Quality should not be taken as the reference point for nuclear emergencies because the levels set are extremely conservative, and designed to apply to lifetime routine intake.

(2) Provisional regulation values relating to limits on food and drink ingestion, established by the Japanese Food Sanitation Act, as indicated by the Nuclear Safety Commission of Japan. These standards are precautionary and have taken international guidance into consideration, including recommendations of the IAEA and the International Commission on Radiological Protection.

(3) As in (2) above, but applicable to drinking-water used to prepare baby food. This level is equivalent to the international guideline set by Codex Alimentarius for infant food.

(4) IAEA Safety Guide GSG-2 established Operational Intervention Levels (OILs) which would be the default international guidance levels for the early stage of an emergency.

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