Mix-ups and disagreements over radiation measurements are adding to confusion about the extent of contamination in Japan due to the accident at the Fukushima No. 1 nuclear power plant.
Mix-ups and disagreements over radiation measurements are adding to confusion about the extent of contamination in Japan due to the accident at the Fukushima No. 1 nuclear power plant.On Dec. 15, Japan Broadcasting Corp. (NHK) ran a segment admitting inaccuracies in a report about levels of radioactive cesium in the food of seven families around Japan.NHK said defects in measuring equipment and confusion about the inclusion of background radiation had contributed to overstating of the families’ exposure. The program makers were dealing with tiny levels of radiation with methods that have minimal detectable levels of between 3 and 8 becquerels per kilogram, increasing the risk of error.In October, the Yokohama city government announced that levels of radioactive strontium at 129 becquerels and 59 becquerels per kilogram were detected from sediment in a gutter.But the following month, the science and technology ministry announced its own findings, saying no strontium 89, which has a half-life of 50 days, was detected and that only a maximum of 1.1 becquerels of strontium 90 was present. The scientists behind the two conflicting measurements are still at odds. Ministry officials, using a different measurement technique from the original Yokohama tests, concluded that the strontium found could be explained as the result of past atmospheric nuclear testing. The Isotope Research Institute, which conducted the test for the Yokohama city government, used new technology to return results that would normally take three weeks in a day but officials for the institute maintained that another analytical method had confirmed the presence of strontium.While the science and technology ministry pointed to the possibility that radioactive lead had been mixed with the sample, the institute said it had excluded the possibility of contamination from lead and that no gamma rays from lead had been detected. Reports on the Internet also stated in October that milk with levels of cesium exceeding 1,000 becquerels per kilogram had been discovered. Milk manufacturers were flooded with inquiries, but the measurement was later found to have been a mistake. In fact, no cesium was present in the samples."It is not easy to measure radiation," said Ryugo Hayano, a physics professor at the University of Tokyo. "There is insufficient understanding that it is different from getting on a scale and obtaining an immediate accurate weight measurement. A lack of knowledge and experience on the part of testing agencies has led to testing errors and confusion."Detecting strontium is particularly difficult, with very few agencies capable of producing accurate measurements.But some businesses eager to cash in on the public interest in radiation levels are wasting no time in getting into the market for food, water and soil tests. Internet searches turn up several companies charging for such services."After the nuclear accident, companies with no experience in radiation testing have bought measurement equipment and entered the radiation testing sector," said an official with one testing company. "It is difficult to determine if strict quality control is being enforced."Agencies that measure air and water pollution and those that test for chemical contaminants such as dioxins have to register with prefectural governments, but there is currently no official registration system for radiation testing agencies.While there are international standards for testing agencies and procedures to ensure the accuracy of measurement equipment, many of the agencies now active in Japan have no certification.