The FDA announced on March, 30 that results from a screening sample taken March 25 from Spokane, Wash. detected 0.8 pCi/L of iodine-131, which is more than 5,000 times lower than the Derived Intervention Level (DIL) set by the U.S. Food and Drug Administration.
In light of that and the eventual elevation of levels as the Fukushima reactor continues to spew radioactive materials into the atmosphere, I have compiled the information below. This information will be updated as events warrant. Check the end of this article for updates and new links.
Internal exposure by ingestion of radioactive iodine (I-131 ) occurs when persons eat food that is contaminated with the fallout. The oral pathway is the main route of internal I-131 exposure for people. Milk is the major source of internal exposure. I-131 is radioactive, has an 8.03 day half-life, and emits beta and gamma radiation.
The thyroid gland is the critical organ for I-131 exposure. Essentially all of the iodine entering the body quickly becomes systemic (EPA 1988), with approximately 30% depositing in the thyroid. Dietary intake of iodine before exposure is important because a relative iodine deficiency increases the thyroid uptake of I-131.
After cow’s graze on grass that has been contaminated by radioactive fallout, glands in the cow’s udder concentrate the radioactive iodine and release it into the milk. Goat’s milk and sheep’s milk contain approximately 10 times the concentration of radioiodine found in cow’s milk.
After exposure, the most critical dietary information needed is the amount and type of milk and milk products consumed, their I-131 concentrations, and the time they were consumed relative to the time of the release.
Inhalation, especially near releases of I-131 in the absence of rain, is another route of internal exposure. However, doses to humans from inhalation and from ingestion of plants, animals, or water are usually small in comparison. Figure 1 shows the exposure pathways of I-131 from the environment to humans.
FDA RADIOACTIVE CONTAMINATION OF HUMAN
FOOD AND ANIMAL FEEDS GUIDELINES
“A temporary embargo to prevent the introduction into commerce of food from a contaminated area should be considered when the amount of contamination equals or exceeds the DILs or when the presence of contamination is confirmed, but the concentrations are not yet known. The temporary embargo would continue until measurements confirm that concentrations are below the DILs.
Normal food production and processing procedures that could reduce the amount of radioactive contamination in or on the food could be simple, (such as holding to allow for radioactive decay, or removal of surface contamination by brushing, washing, or peeling) or could be complex. The blending of contaminated food with uncontaminated food is not permitted because this is a violation of the Federal Food, Drug and Cosmetic Act (FDA 1991).”
Natural Sources of Iodine
Normally, your body stores between 20 to 30 mg of iodine, most of which is kept in the thyroid gland. While iodine deficiency was a problem in the early 20th century, the inclusion of iodine in iodized salt has nearly eradicated the problem. Also, because it is often added to animal feed, iodine is passed onto humans through cow’s milk.
Iodine-131 may not be the only concern in the future if the slightly heavier and longer-lasting isotopes experienced after Chernobyl make it across the Pacific. The food monitoring results from FDA and others following the Chernobyl accident support the conclusion that I-131, Sr-90, Cs-134 and Cs-137 are the principal radio-nuclides that contribute to radiation dose by ingestion following a nuclear reactor accident, but that Ru-103 and Ru-l06 also should be included.
LATEST EPA RADNET MILK INFO:
Radiation from Japan has been detected in drinking water in 13 more American cities, and for the first time cesium-137 has been found in American milk—in Montpelier, Vermont, according to data released by the Environmental Protection Agency late Friday. The sample contained 1.9 picoCuries per liter of cesium-137, which is under EPA’s 3.0 picoCuries per liter standard.
Milk samples from Phoenix and Los Angeles contained iodine-131 at levels roughly equal to the maximum contaminant level permitted by EPA, the data shows. The Phoenix sample contained 3.2 picoCuries per liter of iodine-131. The Los Angeles sample contained 2.9.
The EPA maximum contaminant level is 3.0, but this is a conservative standard designed to minimize exposure over a lifetime, so EPA does not consider these levels to pose a health threat.
Airborne contamination continues to cross the western states, the new data shows, and Boise has seen the highest concentrations of radioactive isotopes in rain so far.
A rainwater sample collected in Boise on March 27 contained 390 picocures per liter of iodine-131, plus 41 of cesium-134 and 36 of cesium-137. EPA released this result for the first time yesterday. Typically several days pass between sample collection and data release because of the time required to collect, transport and analyze the samples.