By Phred Dvorak
A year after the nuclear accident in Fukushima caused a global scare about Japanese food safety, the country is trying to reassure the consuming public with stricter new standards on radiation contamination coming into effect this Sunday.
Livestock from Fukushima prefecture last July, after high cesium levels were detected in the prefecture’s beef.
The new rules tighten the country’s already tight limits on permissible levels of radioactive cesium — the most common source of long-term contamination after last year’s accident — in everything from drinking water to milk and meat.
The limit for drinking water will fall to one-twentieth of what it had been. For most foods, the new level will be one-fifth the old limits. Japan’s new standards will also include a separate, lower level for food given to infants, who, researchers say, are the most vulnerable to the effects of radiation.
Figuring out how much radiation is safe in food is a murky process. Scientists measure the radioactive content by tracking how many times each second radioactive energy is released by the cesium inside the food, a unit called a becquerel. After that, health authorities decide how much radioactive exposure their populations will tolerate annually from food, and how much exposure they’ll likely get from other sources.
The acceptable level assesses the anticipated physical impact of radiation. There’s also a lot of wiggle room to adjust assumptions to account for how worried people seem to be about it. The authorities then figure out how much contaminated food would have to be eaten, every day, to reach that level.
Japan’s new permissible level for drinking water, 10 becquerels per kilogram, is lower than that for milk, at 50 becquerels per kilogram, since the government assumes people will drink more water than milk.
Japan’s health ministry says the new standards bring Japan in line with some of the strictest recommendations from international bodies. The U.S. and European Union each have their own standards that permit considerably higher levels of radioactive cesium than Japan does. Their rules vary widely – both in how food categories should be grouped and in levels of radiation permissible. U.S. food-safety restrictions wouldn’t go into effect, for instance, until 1,200 becquerels of radioactive cesium had been detected per kilogram. The EU’s standard for radiation in food in the case of future nuclear accidents has one limit for liquids — 1,000 becquerels per kilogram — and another for other kinds of foods — 1,250 becquerels per kilogram.
Scientists say all those limits are far below levels of contamination where they can see any evidence of an effect on health.