Wednesday, March 23, 2011

Tokyo Water Alert

The confluence of partial information and incomplete understanding of hazards continues in Japan. Japanese officials warned people not to give tap water to infants because of a rise in radioactive iodine 131 readings. This has caused a rush on bottled water and questions why the warning only applies to infants.

As Chernobyl proved, children and their thyroids are very susceptible to damage from radioactive iodine 131. The 2005 UN report on Chernobyl listed almost 4,000 children and adolescents suffering thyroid cancer after that accident. Of these cases only nine died. So caution in regards to young children is a neccesary and prudent thing for the Japanese government to do.

What is the reading that has prompted this warning from the Japanese? Readings of 210 and 190 bequerels per liter. What the heck is a bequerel[Bq]? It is a unit of measurement in the System Internationale, the older measurement unit is called a Curie[Ci]. Both measure the amount of ionizing radiation released by a material - Alpha, Beta, Gamma, and Neutron particles. The US FDA takes a very conservative outlook when it comes to infant food and contamination, the FDA assumes 100% of the infant's food is contaminated and that assumption is then factored into a formula that determines the reading in Bq/Kg used to determine safety levels. For non-infants, the assumption is 30% contamination.

FDA Guidelines on Imported Food:
Table 1
Levels of concern (LOCS) for radionuclide activity concentration in imported food from CPG sec. 560.750 Radionuclides in Imported Foods -- Levels of Concern (CPG 7119.14) which have been superceded by derived intervention levels (DILs).(a) Radionuclide Group LOCs (Bq/kg)
A. Infant Food
Iodine-131 - 55 Bq/Kg
Cesium-134 + Cesium-137 - 370 Bq/Kg
B. Other Food
Iodine-131 - 300 Bq/Kg
Cesium-134 + Cesium-137 - 370 Bq/Kg

FDA Guidelines on Domestic Commerce and Food
Table 2
Derived intervention levels (DILS) in the new CPG for food in domestic commerce and food offered for import(a,b). These values, which are included in CPG sec. 560.750 Guidance Levels for Radionuclides in Domestic and Imported Foods (CPG 7119.14), supercede levels of concern (LOCS) in CPG sec. 560.750 Radionuclides in Imported Foods -- Levels of Concern (CPG 7119.14). Radionuclide Group DIL (Bq/kg)
Strontium-90 - 160 Bq/Kg
Iodine-131 - 170 Bq/Kg
Cesium-134 + Cesium-137 - 1200 Bq/Kg
Plutonium-238 + Plutonium-239 + Americium-241 - 2 Bq/Kg

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