A large amount of evidence confirms
that ionizing radiation (such as UV radiation, X-rays, and charged atomic
particles), when delivered in high doses, increase the cancer risk in humans.
Though radiation induced cancer looks no different than regular cancer, the
connection is determined by the statistically higher cancer rates observed from
people exposed to radiation than the expected natural occurrence for cancer.
Though scientists have determined that high levels of radiation exposure and
cancer are connected, they don’t fully understand how the two are connected,
especially since cancer appears years after the initial exposure.
The way we calculate cancer risk due to low doses of radiation is perhaps more confusing than the odd but clear connection between high doses and cancer. Our knowledge about radiation-induced cancer is based mostly on studies from people who have received large doses, such as survivors of the attacks on Hiroshima and Nagasaki. However, these attacks released large neutron doses. Because neutrons have a large linear energy transfer (LET), they are relatively large in the scheme of ionizing radiation. Most of the radiation the average person is exposed to is low doses of low LET radiation.
The lack of data about how low level doses affect cancer risk means that scientists calculate the risk from the high doses. This is like saying “if use a crane to drop a car on a house, we can determine how many tiles we’ll knock off if we place a tricycle on a different house”. If this sounds like it doesn’t really correlate, it’s because it doesn’t. This is referred to as the Linear No-Threshold Relationship (LNT). LNT states that any amount of radiation is bad. However, studies have shown that the absence of radiation is detrimental to organisms. This is especially significant when you consider the concept of radiation hormesis, which states that low levels of radiation, just above background levels, might be beneficial and help to stimulate the activation of mechanisms that help repair DNA.
Overall, though we can predict cancer for high level doses, the calculation of radiation-induced cancer risk are inefficient for low level doses. Until we determine better methods, it’s better to be safe than sorry.
The way we calculate cancer risk due to low doses of radiation is perhaps more confusing than the odd but clear connection between high doses and cancer. Our knowledge about radiation-induced cancer is based mostly on studies from people who have received large doses, such as survivors of the attacks on Hiroshima and Nagasaki. However, these attacks released large neutron doses. Because neutrons have a large linear energy transfer (LET), they are relatively large in the scheme of ionizing radiation. Most of the radiation the average person is exposed to is low doses of low LET radiation.
The lack of data about how low level doses affect cancer risk means that scientists calculate the risk from the high doses. This is like saying “if use a crane to drop a car on a house, we can determine how many tiles we’ll knock off if we place a tricycle on a different house”. If this sounds like it doesn’t really correlate, it’s because it doesn’t. This is referred to as the Linear No-Threshold Relationship (LNT). LNT states that any amount of radiation is bad. However, studies have shown that the absence of radiation is detrimental to organisms. This is especially significant when you consider the concept of radiation hormesis, which states that low levels of radiation, just above background levels, might be beneficial and help to stimulate the activation of mechanisms that help repair DNA.
Overall, though we can predict cancer for high level doses, the calculation of radiation-induced cancer risk are inefficient for low level doses. Until we determine better methods, it’s better to be safe than sorry.
In your research have you come across any studies that are trying to help clear up how we calculate risks? I found this website that is a radiation risk assessment tool for lifetime risk to cancer using BEIR VII report data.
ReplyDeletehttps://irep.nci.nih.gov/radrat
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ReplyDeleteI get the point you're trying to make. That at low radiation levels, it is imprecise to assume this radiation caused the cancer in question. But, what exactly did you mean when you said neutrons are "relatively large in the scheme of ionizing radiation"?
ReplyDeleteI enjoyed reading your post. It's difficult to be able to put numbers to the amounts of radiation you can receive before getting cancer since there is no way to test it other than using data from accidents such as Hiroshima and Nagasaki. And even with that data there is never a definitive way of knowing if that cancer came from the radiation or some other unknown cause.
ReplyDeleteI know that at some point UF was involved in assessing risks from Chernobyl data as well, but I'm having a hard time finding any results from that.
DeleteIt's a bummer that we have to rely so heavily on data from accidents like these...
Great point about LNT. It seems like Hormesis might be a better way to measure the effects of low level radiation. Do you think it could be accepted as a model for low level radiation doses in the future
ReplyDeleteFortunately and unfortunately, the recent Fukushima nuclear accident and associated damages are a pretty good opportunity to study this topic. With recent technology and fresh results, the chances to learn from this accident could've been something to offset how terrible it was and the environmental damages. However, I did some reading on the stuff we learned about in Risk like the USS Ronald Reagan about Japanese responses to accidents and it seems the Navy and Japanese officials have been less than active in taking advantage of it. Its been 5 years since the accident and there is obviously an upwards trend in the amount of cancer in sailor post-deployment to help Japan. Hopefully we can use this as an unfortunate opportunity to gather data, since people generally don't voluntarily submit themselves to lethal levels of radiation.
ReplyDelete