Radiation is among the most comprehensively understood health risks. We have been investigating the effects of radiation for more than a century. Therefore, we possess considerable knowledge regarding how ionizing radiation interacts with living tissues. It is established that high doses of radiation can be fatal.
Furthermore, we understand that it can lead to cancer. It is also known to potentially harm a fetus at various stages of pregnancy. Although we have not observed this in humans, it is recognized that radiation can induce hereditary effects in laboratory animals.
However, similar to other toxins, the dose is what determines the poison. You may recall from a previous discussion that we are continuously exposed to a certain level of radiation from our natural surroundings. Thus,
not every exposure is anticipated to result in harm. The critical factors are the amount of exposure and the level of radiation we encounter; it is the dose that influences potential health outcomes.
How does radiation damage living tissue
How does radiation harm living tissue? Ionizing radiation has the ability to disrupt bonds in molecules, affecting any type of molecule. Within the cell, it performs the same action. Similar to other toxins, our genetic material, DNA, becomes the main target, and radiation can inflict damage on DNA either directly through interaction with the molecule or indirectly. Given that our cells contain a significant amount of water molecules, radiation interacts with water, leading to the breakdown of these molecules, which in turn generates free radicals that can harm our DNA. This represents an indirect mechanism of damage.
This is the process by which ionizing radiation can injure our cells. Therefore, what occurs after a cell has been exposed to radiation?
How does radiation damage cells
If the DNA is damaged, it has the ability to repair itself accurately to its original state prior to the damage, allowing the cell to restore its normal function and continue its life.
Another possibility is that the repair process may go awry, resulting in an incorrect repair. Consequently, the cell may become altered, which could eventually lead to the development of a cancerous cell. This presents a potential risk. Alternatively, following damage, the cell may undergo death. In fact, this outcome can be beneficial; if only a limited number of cells perish, the overall function of the tissue remains intact, thereby reducing the risk of a misrepaired cell causing future harm. However, if the damage is extensive, with a high dose leading to a significant number of cell deaths, the function of the organ becomes compromised, which is detrimental. This situation can result in organ failure. Thus, these are the three possible outcomes.
Effects of radiation
In addition to the dose we previously discussed – radiation dose – the health effects of radiation are also influenced by the dose rate; that is, the speed at which the dose is administered to the body. Therefore, if the same dose is administered over an extended duration, the resulting effect would not be as severe as if the entire dose were delivered in a single instance. Furthermore, the specific area of the body that is irradiated plays a significant role. If a dose is targeted only at a specific part of the body, the health impact is less severe compared to exposure of the entire body. Individual sensitivity is another factor to consider. Children and young adults exhibit greater sensitivity to the long-term effects of radiation due to their developing tissues and rapidly dividing cells, coupled with a longer lifespan that allows for the potential development of cancer later in life. Consequently, children and young adults are more vulnerable in this regard. Additionally, even among individuals of the same age, there is variability in sensitivity to radiation. Now, to gain a general understanding of the range.
Range of health effects
When examining the health effects associated with varying doses of radiation, from very high to very low, we can analyze three distinct scenarios. In the case of a high radiation dose that is administered to the entire body over a brief period, the likely outcome is death. The individual is expected to die, potentially within a few days; in instances of extremely high doses, this could occur within just a few hours. Furthermore, it may take several weeks following a phase of severe illness characterized by internal bleeding and infections.
In contrast, with a moderate dose of radiation, the individual would experience radiation sickness, with symptoms manifesting. However, there is a significant chance of survival, which improves with the provision of prompt medical care. Those who survive exposure to this moderate level of radiation will face an elevated risk of developing cancer later in life, exceeding the risk typically observed in the general population.
Conversely, if the radiation dose is low, the individual will not experience radiation sickness, and there will be no immediate health effects or symptoms. Additionally, it is unlikely that any observable health effects will arise later in life. Nevertheless, statistically, there remains a higher-than-average risk of developing cancer over time, meaning that the individual will carry a slight risk of cancer throughout their life. In cases of extremely low doses, this marginal increase in cancer risk is so minimal that it becomes immeasurable, rendering it practically non-existent. Therefore, in terms of potential health effects, the risk associated with very low radiation exposure is negligible.
Doses
The effects of radiation are contingent upon the dose, which must be assessed within its context. This chart illustrates typical doses from common exposures, such as air travel, chest X-rays, or CT scans, in comparison to the annual natural background radiation we receive.
Additionally, you will observe the 50 percent survival dose. This is the amount of radiation that would provide a 50 percent probability of survival, meaning the individual would have a 50 percent chance of overcoming radiation sickness.
This specific dose is 4,000 millisieverts, which is comparable to undergoing 400 CT scans consecutively or receiving 1,300 years’ worth of natural background radiation in a single instance. I understand that these dose figures can be quite overwhelming.
Pinto Beans
It may still seem somewhat abstract. Therefore, allow me to illustrate in another manner what these doses would represent. Rather than using millisieverts, let us consider pinto beans as a unit of radiation. This is for those of you who appreciate radiation units – I share that interest as well, but for the purpose of this lecture, I will equate one pinto bean to 10 microsieverts, or one millirem. Thus, a pinto bean corresponds to 10 microsieverts or one millirem. I will refrain from discussing dose further; instead, I will focus on pinto beans.
As we have discussed in previous segments, we are exposed to a certain amount of radiation from our natural background each year, which totals 300 pinto beans. I will place this in a jar. Therefore, it is one-third full. This represents the average amount of radiation we receive from our natural environment annually. Additionally, keep in mind that this dose is received daily. Hence, the rate is equivalent to one pinto bean per day, which we obtain solely from our natural surroundings.
Now, on one of these days, you may require a CT scan. When you do, the amount of radiation you will receive is approximately this many pinto beans. For instance, around 1,000 pinto beans for an abdominal CT scan. This quantity is roughly three times the previous amount. Therefore, it equates to three years’ worth of natural background radiation in a single CT scan. Furthermore, remember that you are gaining benefits from this – do not forget that this dose provides advantages. Let us not overlook that aspect. If a second test is necessary, you will, of course, receive a second dose, and so forth. This is a part of our daily existence. This is what we experience and accumulate over time.
At what point, then, will we observe any clinically noticeable effects in an individual who has received radiation, or pinto beans? Very well, this is the quantity here.
This is the number of pinto beans required to begin observing effects in a person. An individual who receives this many pinto beans would still not exhibit radiation sickness, would not display any symptoms, and would not feel any different. However, if you were to take a blood sample from this individual, you would notice.
Now, this person will have a higher risk of cancer developing later in life. So, he carries that risk with him. There will be a slight increase in cancer risk for this person, but there will be no clinical manifestation that can be observed. So, at what point are we going to see clinical?
At what point are we going to see the effects of radiation exposure? That would be about two of these jugs– we’re going to start getting to the territory of developing radiation sickness. About two of these jugs, but it is still not lethal. To get to the 50 percent survival dose, we need ten of these jugs. So, ten of these jugs, if a person received ten of these,
would have a 50 percent chance of survival. The reason I wanted to show you this is to illustrate the difference between doses in our daily lives that we’re exposed to and
the type of doses that can actually do us harm. Because we can measure radiation, and because we can understand its health effects, we can work safely around it. And also, we can take practical
measures to limit our radiation exposure. And I’m going to talk about those in a different segment.
Source:
https://www.cdc.gov/radiation-emergencies/php/training/rad-basics.html
https://en.wikipedia.org/wiki/Radiation
https://www.cdc.gov/radiation-health/about/health-effects-of-radiation.html
