Japanese officials issued a warning today about elevated levels of radiation in the tap water in Tokyo. Iodine levels were recorded at 210 Becquerels, over twice the recommended limit per liter for infants. Levels are still considered safe for adults—the adult limit is 300 Becquerels per liter. No warning has been issued for children, but this worries me. Younger children, especially, are much closer in size to an infant than an adult. Shouldn’t a forty pound child have a lower daily limit than a 110 pound adult (I’m adjusting for Japan, here).
Here’s what the CDC says (via the New York Times):
“If an adult and a child ingest the same amount of radioactive iodine the thyroid dose to a newborn will be 16 times higher than to an adult; for children under 1 year, 8 times the adult dose; for a 5-year-old, 4 times the adult dose.”
I’m no math whiz, and there are obviously many factors, but but doesn’t it sound like they should be telling kids not to drink the water, too?
Then there’s the problem of pregnant women. Studies of prior nuclear disasters have shown the fetus in utero to be supremely vulnerable to the effects of radiation during pregnancy. Experts have already expressed concern that the Japanese have not been doing enough to warn pregnant citizens about prenatal radiation risk.But now, it seems, they’re coming right out and telling pregnant women there is no risk:
“The Japanese daily Asahi Shimbun cited the Health Ministry as saying that drinking the water would hurt neither a pregnant woman nor her fetus, and that it was safe for bathing and other everyday activities.
But experts say that pregnant women, nursing mothers and fetuses, as well as children, face the greatest danger from radioactive iodine, which is taken in by the thryoid gland and can cause thyroid cancer…Pregnant women also take up more iodine-131 in the thyroid, especially during the first trimester. The iodine also crosses the placenta and reaches the fetus, and the fetal thyroid takes up more and more iodine as pregnancy progresses. During the first week after birth a baby’s thyroid activity increases up to fourfold and stays at that level for a few days so newborns are especially vulnerable. Women who are breastfeeding will secrete about a quarter of the iodine they ingest into their milk.”
Children’s risk is higher not only because of their smaller size, but because their thyroid glands are more active as they grow. Radiation exposure from the Chernobyl disaster caused an epidemic of thyroid cancer in people hwo were children at the time of the iodine exposure.