Ingestion of I-131 and U-238. Which is worse?

Hello
Definitely the I-131. This has a shorter half-life (8.30 days) and is a Beta emitter than U-238 (4.5 billion years) and is an Alpha emitter. The shorter half life means it has a higher emission rate and overall activity. Beta radiation (electrons) also have a greater penetration than alpha radiation (He atoms).

According to http://en.wikipedia.org/wiki/I-131, the following health effects are noted:
"When 131I is present in high levels in the environment from radioactive fallout, it is absorbed by the body and may cause damage to the thyroid. This can be mitigated by taking iodine supplements, raising the total amount of iodine in the body and therefore reducing uptake and retention in tissues and lowering the relative proportion of radioactive iodine. Such supplements were distributed to the population living nearest to the Chernobyl nuclear power plant after the disaster.

The primary risk of concern associated with exposure to 131I in fallout is the chance occurrence of radiogenic thyroid cancer in later life. Other risks include the possibility of non-cancerous growths and thyroiditis. Within the USA, the highest 131I fallout doses occurred during the 1950's and early 1960's to children who consumed fresh sources of milk contaminated as the result of above ground testing of nuclear weapons.[1]"

According to http://www.janes.com/defence/news/jdw/dutoxic010112_1_n.shtml, the damage from U-238 is limited to kidney tubules, if it can make it there.

Overall, though, the I-131 is more likely to pose a health risk.

Dr. M
105813

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