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Report on the Investigation of Shimadzu NOx Monitor Mis-measurement

April 7, 2006

In order to investigate the possible under-measurement issue of the nitrogen oxide (NOx) monitors made by Shimadzu Corporation, the Ministry of the Environment (MOE) set up a special committee for assessing the reliability of the air pollution monitoring equipment. (The committee is chaired by Prof. Kazuhiko Sakamoto at Saitama University Graduate School). The committee recently compiled and released a report of the investigation. The results were as follows:

The report concluded that when measured by the Shimadzu monitors, the value of nitrogen dioxide was likely to be lower than the actual value, because the Shimadzu monitors lacked an optical filter that has to be employed as specified by the MOE's “Manual for Continuous Monitoring of the Air Pollution," and were thus unable to remove the influence of factors interfering with the measurement.

However, the impact that the monitor had on its measurements was minor, the report said. The committee conducted parallel measurements using the Shimadzu monitor and other makers'monitors, and came to the conclusion that the impact was smaller than was anticipated by MOE last December. The result reaffirmed the MOE's first prediction that there was only a small possibility of the Shimadzu monitors' under-measurements affecting the judgment on the environmental quality standards achievement, and that, even if the measurements did affect the judgment, the degree of the influence was minor.

It should be noted that the data measured by the Shimadzu monitor at each monitoring station should basically be considered reference values. It is since the level of interference factors around the monitoring stations was unknown, and therefore the influence cannot be shown quantitatively.

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