Iodine detected in Tokyo tap water no major cause for concern

The detection of 210 becquerels of radioactive iodine per 1 kilogram of tap water at Kanamachi filtration plant in Katsushika Ward, Tokyo, has caused anxiety to Tokyo residents. The metropolitan government has advised residents of the capital's 23 wards and other areas who use water from the plant not to allow babies aged below the age of 1 to drink the tap water. However, questions remain as to whether the water is safe for bathing or whether infants older than 1 year of age can drink it. Compiled below are common questions and responses based on advice from experts.

Question: Why are only babies below the age of 1 subject to the ban?
Answer: Radioactive iodine has a tendency to collect in the thyroid. If children whose thyroids are developing rapidly ingest a massive amount of radioactive iodine, it is thought that it will increase the risk of cancer. The Nuclear Safety Commission of Japan (NSC) advises people including adults not to drink any water that contains more than 300 becquerels of radioactive iodine. Provisional regulations that the government has set under the Food Sanitation Law stipulate that infants below the age of 1 should not drink milk or water containing more than 100 becquerels of radioactive iodine or use such milk or water to dissolve milk powder. Based on the regulations, the government has urged the public not to allow babies to drink tap water containing more than 100 becquerels of radioactive iodine following radiation leaks at the Fukushima No. 1 Nuclear Power Plant that was heavily hit by the March 11 earthquake and tsunami.

Q: How about expecting mothers?
A: There is no upper limit on the amount of radioactive substances that babies in their mothers' wombs can absorb, and the metropolitan government has not urged pregnant women living in areas subject to the advisory not to drink tap water. An obstetrician says, "Under the current circumstances, it is desirable for expecting mothers to avoid drinking tap water in the affected areas. However, any stress mothers feel from struggling to obtain mineral water in short supply, will be more harmful to their health."

Q: Should we also avoid using tap water in these areas for bathing babies and brushing their teeth?
A: The Health, Labor and Welfare Ministry says this is not a problem. It is also fine to wash baby bottles and fruit for babies with tap water. Otsura Niwa, a Kyoto University professor emeritus of radiation biology, says, "Japan's standards are too strict in the first place. Even if babies are given tap water, their parents don't have to worry too much about it."

Q: Should mineral water be used to dissolve milk powder for babies?
A: Since milk powder contains minerals, babies could suffer from diarrhea if so-called "hard water" containing a massive amount of minerals was used to dissolve milk powder. If you want to use mineral water to dissolve milk powder, you should use "soft water."

Q: Can't radioactive substances be removed at tap water filtration plants?
A: Tap water filtration plants are designed to remove impurities and odor, but not radioactive substances. Takeo Samaki, Hosei University professor of science literacy, says that an advanced water treatment technology -- in which ozone gas is used to decompose impurities and activated charcoal is used to absorb organic matters in water -- is employed at the Kanamachi filtration plant. However, it is believed to be able to remove only a small portion of radioactive substances.

Q: Can radioactive substances be removed with water purifiers for household use or by boiling the water?
A: The structure of ordinary water purifiers for household use is similar to that of water filtration plants, so you shouldn't expect such devices to remove radioactive substances from tap water. It is also believed difficult to remove radioactive substances from water by boiling it.

Q: Will a similar advisory be issued for wider areas?
A: The Health, Labor and Welfare Ministry has instructed waterworks departments at local governments across the country to make announcements if more than 100 becquerels of radioactive iodine are detected in their tap water. Close attention should be paid to figures announced by local governments.

(Mainichi Japan) March 24, 2011