by Mona Jhaveri - May 16, 2022

The nuclear age officially began in 1945, when the first nuclear weapons were tested in the United States and then used in warfare against Japan. Since then, the effects of nuclear radiation on human health have been extensively studied, particularly in populations exposed to high levels of radiation from nuclear accidents or nuclear bomb testing.

The 21st century brings new uncertainties and rising tensions between nuclear-armed countries. In particular, the possibility of nuclear war has again become a major concern for global security. While the chances of an all-out nuclear conflict are relatively low, even a limited nuclear exchange could have devastating consequences for both the direct victims and those living in the aftermath.

In this blog post, we explore the potential long-term effects of nuclear war on the global population, with an emphasis on cancer rates and mortality.

Nuclear weapons, a breakdown

A nuclear weapon is any device that uses nuclear fission or nuclear fusion to create an explosion.

Nuclear fission is the process of splitting a heavy nucleus (the center part of an atom) into smaller nuclei, releasing energy in the process. This can be done using either an internal or external trigger.

Nuclear fusion is the process of combining two lighter nuclei to form a heavier nucleus, also releasing energy. This process can only be done using an external trigger, such as a nuclear bomb.

Both fission and fusion reactions release large amounts of energy in the form of heat and radiation.

  • A nuclear bomb that uses fission as its primary mechanism is sometimes called an atomic bomb or A-bomb.
  • A nuclear bomb that uses fusion as its primary mechanism is sometimes called a hydrogen bomb or H-bomb.

The two bombs dropped on Hiroshima and Nagasaki in 1945 were both A-bombs.

Effects of a nuclear explosion

Here is a rough outline of what happens when a nuclear weapon detonates, in chronological order:

  1. A large fireball forms in the very center of the explosion, reaching temperatures of up to several million degrees.
  2. The fireball rapidly expands outward, vaporizing everything in its path, including water and soil. This is how the well-known mushroom cloud is formed, the head of which is mostly filled with radioactive particles (but also smoke, soot, dust, and other debris).
  3. The shock wave from the nuclear blast reaches even further than the fireball, causing extensive damage to buildings, infrastructure, and human bodies.
  4. The explosion also emits large amounts of ionizing radiation, which can cause burns, damage internal organs, and be fatal.

All of this happens in just a matter of seconds. When the fireball cools down and dissipates, radioactive fallout is left behind, which can contaminate the environment and cause worldwide long-term health effects.

Medical effects

There are several stages to the medical effects of nuclear detonation:

  • The initial phase is the period immediately following the explosion (1-2 weeks). The main type of sustained injuries are thermal and blast injuries. About 10% of deaths also occur from extremely high levels of ionizing radiation.
  • The intermediate stage is the period from 3-8 weeks after the explosion. People that have been exposed to levels of radiation slightly lower than those that are immediately fatal will start to experience a range of symptoms known as acute radiation syndrome (ARS) or radiation sickness. These include nausea, vomiting, diarrhea, headache, and fever. ARS can also cause more serious effects such as damage to the gastrointestinal tract, skin burns, hair loss, and brain damage.
  • The late phase is the period from 8-20 weeks after the explosion. Until this point, those who have survived might experience some improvements in their symptoms, but they are also at risk for developing long-term effects.
  • The delayed phase is from 20 weeks to years after the explosion. The delayed effects of radiation exposure include an increased risk of cancer and infertility, subfertility, blood diseases, and more.

Cancer and nuclear explosions

Is there a link between nuclear explosions and increased cancer rates? What happens years, even decades, after a nuclear bomb is dropped?

To answer these questions, we must look at data from the few instances where nuclear weapons have been used in warfare: the bombings of Hiroshima and Nagasaki in 1945.

About ten years after the horrific events, Japanese physicians began to notice an increase in cancer rates among the survivors.

Two tumor registries were established – one in Hiroshima in 1957 and one in Nagasaki in 1958 – to keep track of the health effects of the bombings. Numerous studies concluded that there is a direct link between radiation exposure from a nuclear bomb and an increased risk of developing cancer.

Leukemia is the most common type of cancer among those exposed to radiation from the bombings. On average, an A-bomb survivor has a 46% higher risk of developing leukemia than someone not exposed to radiation.

In terms of solid cancers (not blood cancers), there is an average 10% higher risk of developing cancer for those exposed to radiation from the bombings. The most common types of solid cancers among A-bomb survivors are stomach cancer, breast cancer, and lung cancer.

It’s important to note that the same increase of cancer risk in a survivor depends on multiple factors, such as the level of radiation exposure, age, and sex. It is also important to emphasize that there is no ‘safe dose’ of radiation – any amount of radiation exposure comes with some risk of developing cancer.

What about nuclear testing?

In addition to the two times nuclear weapons have been used in warfare, there has also been a long history of atomic testing.

From 1945 to 1980, there were over 500 above-ground nuclear tests conducted by various countries. These nuclear tests resulted in large amounts of radioactive fallout – radioactive particles that get swept up into the atmosphere and can be carried long distances by wind. Even though nuclear test sites are located in very remote areas, the radioactive fallout from these tests has been found in every corner of the globe.

Many countries have since signed treaties banning above-ground nuclear testing because of the potential health risks associated with radioactive fallout. The most recent treaty – the Comprehensive Nuclear Test Ban Treaty – was signed in 1996 and ratified by 170 countries. 

Despite the treaties, there have been a few instances of nuclear testing since 1996, such as the 1998 Pakistan nuclear test and a series of North Korea nuclear tests.

But what exactly is the cancer risk of open-air nuclear weapons testing?

Cancer and nuclear testing

Large radioactive particles tend to settle locally, meaning anywhere between 30-300 miles from the nuclear detonation site. Smaller particles, however, can be carried long distances by wind and eventually settle all over the world.

The CDC estimates that, in 1951, when nuclear testing was in full swing, every single person (and living being) in the United States received a dose of radiation from testing fallout.

There are several ways an average person can be exposed to radioactive fallout from a nuclear test explosion:

  • By breathing in contaminated air
  • By eating contaminated food (especially milk, meat, and plants) and drinking contaminated water
  • By coming into direct skin contact with contaminated air or contaminated ground

As mentioned above, there is no amount of radiation or radioactive material that is completely safe. Any level of exposure comes with some risk of developing cancer.

The International Agency for Cancer Research (IARC) has classified ionizing radiation as a Group 1 carcinogen, which means that there is sufficient evidence that it causes cancer in humans.

But what is the risk of developing cancer from nuclear fallout?

Nevada Test Site data

The most detailed and comprehensive research on this matter was conducted at and around the Nevada Test Site (NTS), a southwestern United States location used for exactly 100 nuclear tests from 1951 to 1962.

These nuclear tests resulted in large amounts of radioactive fallout, which was carried by wind and eventually settled all over the US (and the rest of the world).

In 1997, the National Cancer Institute (NCI) released a report that looked at the cancer rates of people exposed to nuclear testing fallout from the NTS.

The report found that people exposed to NTS fallout had an increased risk of developing thyroid cancer, leukemia, and other solid cancers (aside from thyroid cancer).

Here are the most significant predictions regarding the total number of excess cases of cancer:

  • Thyroid cancer: 49,000 excess cases
  • Leukemia: 1,800 excess deaths (not cases)
  • Other solid cancers: 22,000 excess cases

The report also found that the risk of developing cancer from nuclear testing fallout was higher in children and young adults than in older adults. This is because children and young adults are more sensitive to the effects of radiation than older adults, and the fact that they will live longer means that they have a longer time frame in which they can develop cancer.

It should be noted that the NCI report only looked at data from people who were living in the US at the time of the nuclear tests (1951-1957).

How long does it take for cancer to develop?

It can take anywhere from a few years to several decades for cancer to develop after radiation exposure.

This means that the full extent of the health effects of nuclear testing fallout will not be known for many years to come.

In the meantime, it is important to keep track of cancer rates in people exposed to nuclear testing to understand the long-term effects of radiation exposure better.

Cancer in a nuclear winter

‘Nuclear winter’ is a theoretical scenario in which the smoke and debris from a nuclear war would block out the sun, causing the Earth’s average temperature to drop dramatically (at least by 10 degrees Celsius, or 50 degrees Fahrenheit).

Scientists have studied this scenario extensively, and there is evidence that it could happen.

A nuclear winter would have devastating effects on the environment and human health.

In terms of cancer, a nuclear winter would likely lead to an increase in the incidence of certain types of cancer, as well as a drastic reduction in the survival rates of people who have cancer.

Let’s explore these scenarios in more detail.

Increase in cancer incidence rates

There are a few primary reasons why cancer incidence rates would increase in a nuclear winter.

  • Ionizing radiation – We’ve already established that ionizing radiation is a known carcinogen, which would be present in high levels in a nuclear winter.
  • Ozone depletion – Ozone is a gas layer protecting the Earth from ultraviolet radiation. In the event of a nuclear device detonation, the ozone layer would be broken down, especially in the area where the explosion occurred. This would result in more ultraviolet radiation reaching the Earth’s surface, and this radiation is known to cause skin cancer.
  • Polluted air – All the soot, smoke, dust, and debris from a nuclear war would create a polluted air environment. This pollution has been linked to an increased risk of lung cancer, throat cancer, and similar cancer types.

Of course, the fact that there would be a severe lack of food, water, and medical supplies would also contribute to an increase in cancer rates.

Reduced cancer survival rates

In addition to the increase in cancer incidence rates, the survival rates of people who have cancer would also be reduced in a nuclear winter. Here’s why:

  • Lack of food and drinkable water

One of the main hypotheses of why a nuclear winter would occur is that the smoke and debris from the nuclear explosions would rise into the stratosphere and block out the sun.

This would cause a drastic reduction in the amount of sunlight that reaches the Earth’s surface, which would lead to a decrease in crop yields.

A decrease in crop yields would mean that there would be less food available for people to eat, leading to malnutrition.

Malnutrition has been linked to many health problems, one of which is an increased cancer risk.

In addition, the contaminated water supplies would also lead to dehydration, which would further increase the risk of cancer.

  • Lack of medical supplies and treatment

In a nuclear winter, there would also be a lack of medical supplies and treatment. This is because the infrastructure needed to produce and distribute these items would be destroyed by nuclear explosions.

This would mean that people who have cancer would not be able to get the treatment they need, leading to a decrease in their survival rates. Just take a look at how the COVID-19 pandemic affected cancer care. In a nuclear conflict, the situation would be much worse.

Of course, there would be a general decrease in the quality of life, contributing to the reduced survival rates of people with cancer.

Does it matter whether nuclear war is big or small?

What constitutes a ‘big’ or ‘small’ nuclear war? Would global effects be less serious if a conflict arises only between two countries with small nuclear arsenals?

This is unlikely.

Even a ‘small’ nuclear war could have devastating effects on the environment and human health. This is one of the main reasons why nuclear weapons are so dangerous.

It is worth noting that the effects of a nuclear war would depend on some factors, such as the number of atomic weapons used, the yield of the weapons, the altitude at which they are detonated, the weather conditions, and so on.

However, it is safe to say that no nuclear war would be ‘small’ enough to not cause serious harm to the environment and human health.


It is well-established in science that ionizing radiation causes cancer. The third-largest source is nuclear weapons detonations, mostly from weapons testing. No amount of radiation can be labeled as ‘safe,’ and the risk of cancer rises with increasing levels of exposure.

A nuclear war would cause a significant increase in the levels of ionizing radiation, both from the detonations themselves and from the fallout that would result. This would lead to a rise in cancer incidence rates and reduced survival rates for people who have cancer.

The effects of a nuclear war would be felt long after the conflict had ended, and they would be felt by people who were not even alive at the time of the war. This is one of the many reasons why nuclear weapons are so dangerous.

It is important to remember the potential consequences of nuclear war in these uncertain times and do everything we can to prevent such a conflict from happening.

At the same time, we must not give up on our fight against cancer. Only by finding effective cures for this disease will we be able to reduce the number of people who die from it each year.

This is our challenge, and it is one that we must face together. Donate now to support the advancement of cancer-fighting innovations and help us win this war.

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