After-Effects of a Nuclear Explosion – A Humanitarian Crisis

By Rakhee Sharma

April 14, 2023
mushroom like cloud of the first nuclear explosion named Trinity test
Footage of the first nuclear bomb test - "Trinity". Source: Atomic Archive

Have you ever heard about “The Unluckiest Man in the World”?

Meet Mr. Tsutomu Yamaguchi from Japan, the BBC featured Yamaguchi in its comedy program QI, referring to him as “The Unluckiest Man in the World”, as he survived two nuclear explosions, the second one occurred just after 2 days.

Besides Yamaguchi, Frano Selak is another (un)lucky man unrelated to the premise here (and there are probably a few more such).

You would argue if he survived such a tragedy twice, shouldn’t he be the luckiest person instead.

Apparently, surviving in this context is not a good experience as such, at the end, it could be argued both lucky and unlucky depending on how you look at it.

Yamaguchi saw the horrors of nuclear bomb explosion not once but twice, in Hiroshima and Nagasaki both, and lived to tell the tales.

With fresh conflicts brewing up between the nuclear superpowers and the destabilization of some of the nuclear states, the danger of a nuclear attack looms large on us.

In such an event, the medical needs of the injured and sick people would be enormous – fractures, rupture of the intestine, skin burns, retina burns, and hemorrhage will occur within seconds.

Millions of people would be severely wounded and they would have to be treated immediately but the medical facilities would have collapsed.

There would be chaos everywhere as the electronic equipment will stop working due to the electromagnetic pulse burst.

So it makes sense to be prepared instead of being oblivious to the lurking danger and scrolling through videos.


As the saying goes ‘A stitch in time saves nine’.

Nuclear Fallout – Consequences of a Nuclear Explosion

The two nuclear weapons that were dropped on Hiroshima and Nagasaki had an explosive power of 15-20 kilotons or KT, respectively, and the modern weapons today are at least 100 kilotons or higher.

A 100 kiloton bomb detonation over New York City would result in at least 5,00,000 – 6,00,000 fatalities, according to Nukemap[1].

Approximately 85% of the energy of a nuclear weapon produces air blast (and shock), and thermal energy (heat).

The remaining 15% of the energy is released as various types of nuclear radiation in the debris which is thrown far and wide. [2]

The ensuing nuclear fallout poses drastic effects on the human and animal population as well as the environment.

All surface water resources i.e., ponds, lakes, and rivers will be contaminated with radiation and rendered unfit for drinking.

Groundwater will be safe immediately after the event but over time the radioactivity will diffuse and contaminate them and will remain contaminated for the next 10-15 years.

The fission particles will be spread over the soil, agricultural fields, and plants, and as a result fish, grains, milk, and vegetables will all be contaminated[3].

Radioactive Iodine-131 when ingested gets concentrated in the thyroid gland, Strontium-90 is structurally similar to Calcium and gets absorbed in bones and teeth, especially in young children.

Even marine animals are negatively impacted by the fallout passing into the ocean waters; radiation from the fallout will stay in the soil, water, and land for years.

Moreover, the dust released by the explosion would cover the earth in a blanket of soot, blocking sunlight and lowering the global temperature.


The nuclear winter that will follow may reduce the global rainfall, impair agricultural production, and cause a shortage of food globally, also called “Nuclear Famine[4].

The ozone layer will be destroyed and there will be greater instances of skin cancer among the population.

That’s not the end; a nuclear winter is followed by a nuclear summer.

The emission of carbon dioxide and the decay of organic matter over the years will raise the level of greenhouse gases in the atmosphere raising the global temperature and increasing the sea level[5].

There will be widespread extinction of species and maybe the only survivors will be the insects like cockroaches, scorpions, fruit flies, et cetera, which can withstand radiation better than humans.

So what we are looking at is an annihilistic event.

Features of a Nuclear Explosion

When a nuclear bomb is detonated, the most characteristic event that follows is the creation of a large fireball.

Everything in close vicinity of this fireball vaporizes immediately, including soil and water.

This creates the mushroom cloud that is typical of a nuclear explosion, the radioactive debris mixes with the vaporized material and after cooling down condenses into dust and falls back onto the earth.

This radioactive dust that falls back on the earth is called nuclear fallout, which can be carried far away by the wind and blast force impacting even places hundreds of kilometers away from the detonation site.

There are about 200 different isotopes in the air after a nuke goes off and they all decay at different rates.

Some of these isotopes with a short half-life decay quickly and their radiation wears off in a short time, while some others with a longer half-life continue emitting radiations for a greater time and pose a health risk for those in close vicinity.

Predictions of the amount and levels of the radioactive fallout are difficult because of several factors, which include the yield and design of the weapon, the height of the explosion, the nature of the surface beneath the point of burst, and the meteorological conditions, such as wind direction and speed.

How Loud is a Nuclear Bomb Explosion?

A sound level meter set 250 feet away from test sites peaked at 210 decibels. At the source, the level is reported to be from 240 to 280 dB+. It is said that the sound alone is enough to kill a human being, so if the bomb doesn’t kill you, the noise will[6].

How Fast is a Nuclear Bomb Explosion?

The explosion’s blast wave wind at sea level may exceed one thousand km/h, or ~300 m/s, approaching the speed of sound in the air. The atmospheric pressure wave resulting from the TSAR Bomba explosion was recorded three times in New Zealand and had an average wave speed estimated at 303 m/s.

What was the Largest Nuclear Bomb Explosion?

TSAR Bomba is the Western nickname for the Soviet RDS-220 (РДС-220) hydrogen bomb (code name Vanya) detonated by the Soviet Union on October 30, 1961, is the largest nuclear device ever detonated and the most powerful man-made explosion in history. With a yield of 50 megatons of TNT, Tsar Bomba was the culmination of several hydrogen bomb tests conducted throughout this time by both the Soviet Union and the United States[7].

Nuclear Bomb Damage Range

The air blast from a 1 KT detonation could cause 50% mortality from flying glass shards, to individuals within an approximate radius of 0.17 miles or 0.275 km, or 275 m. This radius increases to approximately 0.3 miles or 0.59 km or 590 m for a 10 KT detonation. Other effects such as the blast-heat, radiation and et cetera have a different shorter impact range[8]. In the TSAR Bomba test everything within three dozen miles of the impact was vaporized, but severe damage extended to 150 miles or ~242 km radius.

Effects of Radiation Due to Nuclear Explosion on the Human Body

There are some atoms in nature like Uranium and Polonium which is also the fissile material used as fuel in nuclear bombs, that are highly unstable because the forces in their nucleus are not balanced.

Such atoms have either an excess of neutrons or protons in the nucleus and to attain stability they eject these particles.

Hence they undergo radioactive decay and in the process release their internal energy in the form of ionizing or non-ionizing radiations.


Radiation can be in the form of high-speed charged particles or electromagnetic waves.

Non-Ionizing radiation does not have sufficient energy to ionize atoms or molecules like air, water, and living tissues and is considered to be harmless to the human body.

It can heat substances and exposure to intense, direct amounts of this type of radiation can cause damage to tissues due to burns.

The thermal burns after the blast are a result of non-ionizing radiation, for example, microwaves.

Ionizing radiations, on the other hand, are quite energetic and can easily knock electrons out of the orbit of atoms, upsetting the normal proton/electron balance and giving the target atom a resultant net charge.

Types of Ionizing Radiations

Different radiation has different energy ranges and wavelengths:

  • Alpha radiation particles consist of 2-2 neutrons-protons, absorbed very quickly by matter and lose their energy within a short distance causing considerable damage to tissues.
  • Beta radiation consists of fast-moving electrons ejected from the nucleus of an atom, much smaller than alpha particles but can penetrate human tissue, but not so deeply.
  • Gamma radiation is energy is emitted in the form of electromagnetic (EM) waves after the ejection of an alpha or beta particle from the nucleus, its exposure is very harmful as it penetrates deep into human tissues.
  • X-rays are also a form of EM radiation but they are prepared by artificial means and not from radioactive substances.
  • Neutron particle radiation when neutrons (uncharged particles) are ejected from the nucleus during nuclear fission or some other processes; interacts strongly with biological tissues and are very penetrating like gamma particles.

The type of radiation which is most harmful to the body will depend upon whether the exposure is internal or external.

Non-ionizing and ionizing radiation have different wavelengths, which directly relate to their energy. Credits: Adriana Vargas/IAEA

Alpha particles are the most harmful internal hazard because they have the highest energy but have low penetration.

If the exposure is external, the gamma rays being the most penetrating will be the most harmful.

Alpha and beta radiations can be stopped by layers of the clothing and hence prove to be of less toxicity immediately after the blast, but once they enter the food chain, they can cause havoc inside the metabolic system.

The impact of radiation on living tissue is complicated by the type of radiation and by the type of tissues.


The functions of living tissue are carried out by molecules, that is, combinations of different types of atoms united by chemical bonds.

For example, our skin, which is epithelial tissue, is made up of keratin protein.

There’s a difference between the amount of radiation that a radioactive material emits and the amount of radiation that the human body absorbs, different units are used to measure them.

The radiation that is absorbed by the body is measured in a unit called Gray (Gy).

To cause death within hours of radiation exposure, the dose needs to be very high, 10 Gy or higher, while 4-5 Gy will kill within 60 days, and less than 1.5-2 Gy will not be lethal in the short term[9].

Proteins are polymers of amino acids, and amino acids in turn are composed of atoms like carbon, hydrogen, nitrogen, and oxygen held to one another through various bonds.

The proper functioning of these molecules depends upon their composition and also their structure.

Altering chemical bonds may change their stability and lead to various complications.

We are Actually Exposed to Radiation All the Time

It’s usually overlooked but we are exposed to background radiation throughout our life.

Traces of radioactive materials like Uranium, Iodine, and Potassium can be found in building materials so we are exposed to radiation even though we are indoors.

Radon and Thoron are radioactive gasses formed by the decomposition of radioactive minerals found in the soil which enter our body through inhalation.

Trace amounts of radioactive minerals are also found in food and water.

Do you know when you eat a banana, carrot, or potato you are actually eating some radioactivity too!

In fact, on average we are exposed to about 0.33 mSv or 33 mrem (roentgen equivalent man or rem and sieverts or Sv are used to measure the relative biological damage in the human body, which depends on the type of radiation) of cosmic radiation or 11% of a person’s yearly exposure due to all-natural sources of radiation.

The yearly amount of cosmic radiation received is similar to the amount of radiation from three chest x-rays[10].

Effects on Humans Close to the Nuclear Blast Site

A person who has not been able to find a shelter during the detonation is exposed to a high dose of penetrating radiation(0.7-50 Gy) in a very short period, resulting in  Acute Radiation Syndrome (ARS)[11].

This level of radiation would be like getting the radiation from 18,000 chest X-rays distributed over your entire body in this short period, the symptoms appear within minutes to days of exposure.

The initial heat wave when the temperature touches approximately 7000°C, causes thermal burns which cause the skin to peel off immediately exposing the underneath flesh.


Skin damage includes swelling, itching, redness, and ulcers which may show immediately or be delayed by days.

People who are burned by direct exposure to heat rays within 10 miles of the hypocenter may suffer from Keloids 3-4 weeks after the burns start to heal.

Keloids are formed when the scar tissue covering the healed burns begins to swell and grow abnormally.

This happens because the muscle repair process fails to terminate the synthesis of newer fibrous tissue and hence these painful tissue masses appear.

keloid scars on a humans back
Keloid Scars. Source: Nuclear Physics Weebly

Acute exposure also results in loss of appetite, fatigue, fever, nausea, vomiting, diarrhea, and possibly even seizures and coma, people may also experience temporary hair loss.

Even consumption of water by the heavily injured is discouraged because according to some doctors, intake of water increases the blood flow which can increase the bleeding rate in the gravely wounded people, hastening their death.

Changes at the Molecular Level During Acute Radiation Syndrome?

Ionizing radiation has the greatest deleterious effects on the rapidly dividing cells of the body like the bone marrow, gastrointestinal tract, cells of the reproductive system, and hair cells.

This is because, in rapidly dividing cells, any change in the DNA gets copied into all the cells which are arising from the parent cell.

Hence, the effect is more pronounced, on the other hand, any change in the DNA of a non-dividing cell fails to replicate itself and has minimal damage[12].

Now let’s try to understand why these symptoms occur after radiation exposure.

Blood Cell Damage Due to Radiation

Bone marrow is the cradle of the blood cells and therefore any exposure of bone marrow to radiation harms the blood corpuscles as well.

To understand the correlation, a study was conducted in which sample RBCs were subjected to increasing doses of gamma radiation[13].


The result was astonishing and revealed that radiation can damage the erythrocyte membrane by changing the protein structure and altering the membrane permeability which causes the RBC membrane to rupture causing the death of the RBCs.

Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) studies of the irradiated RBCs revealed that by the 42nd day of exposure, 76% of RBCs in the sample studied had lost their normal morphology.

This explains the reason for the occurrence of anemia in the blast victims.

Subsequent studies with other blood components i.e., platelets and WBCs were carried out, platelet levels were found to be abnormally low.

Platelets carry out coagulation of blood and any decrease in their count results in hemorrhage and internal as well as external bleeding.

Remember how Dengue patients suffer from hemorrhagic rashes when their platelet count gets too low?

WBC (White Blood Cell) count also showed a downslide. Ionizing radiations were found to impair T cell activation .T lymphocytes are a type of WBC which are responsible for destroying infected host cells and play an important role in keeping our immune system healthy[14].

Loss in the activity of T cells causes the immune system to fail and the body is prone to infect microorganisms.

A person may suffer from reduced immunity for up to 10 years after radiation exposure and during this period, the victim suffers from frequent infections, anemia, fever, and poor health.

We can compare this situation to the dreaded disease AIDS where the infecting HIV destroys the T cells and compromises the immune system.

Muscle Damage After a Nuclear Fallout

One of the effects of nuclear exposure is muscle atrophy in which a person suffers from weakness of limbs, impaired mobility, and reduced quality of life.

Studies have shown that Myogenic Stem cells, also called satellite cells, contribute to muscle growth and repair.


Ionizing radiation depletes the satellite cells in the bone marrow and hence the muscle cells are no longer repaired and the person suffers from an increased disability[15]

Intestinal Epithelium Damage Due to Ionizing Radiation

Intestinal epithelium – IR damages the epithelial cells and the stem cells located in the intestinal crypts.

The intestinal villus which is concerned with the absorption of digested food from the intestine fails to repair itself because of the loss of the stem cells; the person suffers from poor appetite, diarrhea, nausea, and vomiting[16].

Ionizing Radiation Damages the Reproductive System

In the case of the reproductive system, IR destroys the germinal epithelium of the testis and ovaries which form the sperms and ovum, respectively.

In women, it affects not only the ovaries but also causes irreparable damage to the uterus leading to sterility[17].

Any change in the genetic material is carried forward to the progenies and it was speculated earlier that there would be greater chances of offspring of blast victims suffering from malignancies.

However, numerous studies with the survivors of Hiroshima and Nagasaki have so far shown that the instance of cancer in the progenies of the victim is almost the same as in people living in any other area.

Heart and Nerve cell Damage

Ionizing Radiation can also destroy the heart cells and nerve cells resulting in seizures, convulsions, respiratory distress, coma, and death.

However, since neurons are not rapidly dividing cells, they are not as sensitive to cell death caused by radiation and require a dose of 50 Gy or more[18].

Situation 3-5 Years After the Nuclear Blast

Experiments with the fruit fly Drosophila melanogaster in 1927 revealed that radiation has a mutagenic effect.

Hence, when the atomic weapons were detonated over the Japanese cities, it was a well-known fact that the survivors would be subjected to large-scale mutations the effect of which is visible only after a few years.

Radiations Will Cause Cell Mutations in Humans

DNA contains the genetic information of the organism and is composed of thousands of nucleotides linked to one another through chemical bonds.


These nucleotides, like amino acids, are made up of molecules of carbon, nitrogen, hydrogen, etc.

IR may knock out electrons from these atoms of the DNA itself or of the neighboring molecules.

The mode of ionization of DNA may be Direct or Indirect; the direct method takes place within 0.000000000000001 of a second[19].

However, the indirect mode is more common in which instead of ionizing atoms of DNA itself, the radiation ionizes the water molecules in the close vicinity of the DNA molecule inside the nucleus.

Disruption of a molecule of water results in the generation of highly reactive oxygen species (ROS) like hydroxyl ions (OH), superoxide ions (O2-), etc, also known as free radicals.

Biological effect of X-ray (ionizing radiation) on human tissue. Source: Stereotactic Radiotherapy for the Management of Refractory Ventricular Tachycardia: Promise and Future Directions

A free radical creates oxidative stress inside the cells and reacts very strongly with other molecules as the radical tries to restore the atoms to their stable state.

Free radicals drift for a much greater time before the antioxidants remove them.

This results in a higher probability of DNA and other molecules like lipids and proteins getting ionized.

All of these collisions and ionizations take place very quickly, in less than a second, and result in the mutation of DNA.

What Happens After Cell Mutation?

A mutation is a heritable change in the DNA sequence of an organism which means a person’s entire future generation will be affected by this mutation.

Any error during the process of DNA duplication or exposure of DNA to mutagens or viruses can alter the nucleotide sequence and change the entire code.

Since each code carried by DNA is highly specific for a different protein, any change in the code can alter the protein in terms of its structure or composition.

The altered protein being biologically different is metabolically inactive and hence there occurs a gap in the efficient functioning of the cell.


Any mutation in the DNA is dealt with in 3 ways:

  • The DNA repair mechanisms consisting of a host of enzymes like DNA polymerases, Ogg1, Apex2, etc., repair any alteration in the DNA sequence or structure. The cell can then carry out its function normally under such circumstances.
  • The cell damage is not repaired or is incorrectly repaired, so the cell is changed. Mutated cells are mostly repaired or eliminated but some survive and if their descendant cells are additionally mutated or the level of gene expression changes, the possibility of developing cancer cells increases. 
  • There is too much damage to the cell, and the cell is eliminated through programmed cell death or apoptosis. Apoptosis ensures that the fallout from this type of implosion does not spread far and limits the toxicity to the cell itself.
dna damage due to human cell mutation
Cells Mutation in Humans. Credits: MOE

However, widespread cell death, such as that caused by very high radiation doses, can lead to organ failure and, ultimately, death.

Survival of a mutated cell is very harmful to the body.

The cells with mutation exhibit various morphological and biochemical features like altered membrane permeability, increased glycolysis, and loss of contact inhibition.

These cells may also show metastatic properties which means they spread from the primary site of origin to form secondary tumors.

Most cancers will appear decades after exposure but leukemia having a low latency (˂ 5yrs) is quite prevalent.

In Hiroshima and Nagasaki, leukemia incidence increased during the late 1940s and reached a peak in the mid-1950s before decreasing to a lower but still elevated level[20].

The risk of cancer of the breast, esophagus, colon, and lung also rose, particularly in people exposed to high levels of radiation. Even today, radiation-related illness and death are seen among the now-elderly survivors.

Accumulation of low doses of radiation still lingering in the atmosphere is said to be the key factor responsible.

How to Prepare to Survive a Nuclear Explosion?

  • Identify shelter locations in advance where you can take shelter; the best locations are underground and in the middle of large buildings.
  • Stay away from doors and windows.
  • Outdoor areas and vehicles do not provide adequate shelter.
  • Carry an emergency supply kit which includes bottled water, packaged foods, and emergency medicines.
  • Get inside before the fallout arrives, which may take 10-20 mins to arrive depending on the wind, snow, etc.
  • The highest outdoor radiation levels from fallout occur immediately after the fallout arrives and then decrease with time.
  • Remove your outer layer of contaminated clothing to remove fallout and radiation from your body and take a shower with soap and water.
  • If a shower is not possible, wipe with a clean wet cloth and discard the cloth in a plastic bag.
  • It is safe to eat or drink packaged food items that were inside a building. Do not consume food or liquids that were outdoors uncovered.
  • Under certain conditions, such as for pregnant, breastfeeding, and under 40 years of age, KI (potassium iodide) tablets are recommended. It is most effective if taken shortly before or right after contamination with radioactive iodine.


  1. Internation Campaign to Abolish Nuclear Weapons (ICANW), ‘How destructive are today’s nuclear weapons?’, n.d,[]
  2. Atomic Archive, ’The Energy from a Nuclear Weapon’ n.d,[]
  3. Wikipedia, ‘Nuclear fallout’, 1 Mar 2023, “Within the first few months of the nuclear exchange the nuclear fallout will continue to develop and detriment the environment. Dust, smoke, and radioactive particles will fall hundreds of kilometers downwind of the explosion point and pollute surface water supplies”,[]
  4. Wikipedia, ‘Nuclear Famine’, 17 December 2022, “it is predicted that billions of survivors in the aftermath of nuclear war, even in non-combatant countries, may experience a dwindling food supply (…) which plunges survivors into “massive levels of malnutrition and starvation”,[]
  5. Wikipedia, ‘Nuclear Winter’, 5 February 2023, “A ‘nuclear summer’ is a hypothesized scenario in which, after a nuclear winter caused by aerosols inserted into the atmosphere that would prevent sunlight from reaching lower levels or the surface, has abated, a greenhouse effect then occurs due to carbon dioxide released by combustion and methane released from the decay of the organic matter and methane from dead organic matter and corpses that froze during the nuclear winter”,[]
  6. Wayne Staab, ‘Loudest Sound’, Hearing Health and Technology Matters, 22 November 2016[]
  7. Atomic Heritage Foundation’, ‘Tsar Bomba’, 8 August 2014[]
  8. Washington State Department of Health, ‘Nuclear Weapon Detonation‘, July 2002, p.[2][]
  9. Keith Baverstock, ‘Explainer: How much radiation is harmful‘, 6 September 2013, “To cause death within hours of exposure to radiation, the dose needs to be very high, 10Gy or higher, while 4-5Gy will kill within 60 days, and less than 1.5-2Gy will not be lethal in the short term. However all doses, no matter how small, carry a finite risk of cancer and other diseases.”,[]
  10. Centers for Disease Control and Prevention, ‘Radiation from Space (Cosmic Radiation)’, 7 December 2015[]
  11. Centers for Disease Control and Prevention, ‘Acute Radiation Syndrome: A Fact Sheet for Clinicians’, 4 April 2018[]
  12. István Turai et al, ‘Medical response to radiation incidents and radio nuclear threats’, The BMJ, 6 March 2004,[]
  13. Deyi Xu et al, ‘Study of damage to red blood cells exposed to different doses of γ-ray irradiation’, Blood Transfus, July 2012,[]
  14. Heng-Hong Li et al., ‘Ionizing Radiation Impairs T Cell Activation by Affecting Metabolic Reprogramming’, Int J Biol Sci, May 2015,[]
  15. J D Rosenblatt  et al., ‘Satellite cell activity is required for hypertrophy of overloaded adult rat skeletal muscle’, Muscle Nerve, Jun 1994,[]
  16. Abobakr K Shadad et al., ‘Gastrointestinal Radiation Injury: Symptoms, Risk Factors and Mechanisms’, World J. Gastroenterol, Jan 2014,[]
  17. Roberto Marci et al., ‘Radiations and female fertility’, Reproductive Biology and Endocrinology, December 2018,[]
  18. Centers for Disease Control and Prevention, ‘Acute Radiation Syndrome: A Fact Sheet for Clinicians’, 4 April 2018, “the full syndrome will usually occur with a dose greater than approximately 50 Gy (5000 rads) although some symptoms may occur as low as 20 Gy or 2000 rads”[]
  19. The Advisory Committee on Human Radiation Experiments (ACHRE), ‘How Does Radiation Affect Humans?’, n.d, ”If this electron comes from the DNA itself or from a neighboring molecule and directly strikes and disrupts the DNA molecule, the effect is called direct action. This initial ionization takes place very quickly, in about 0.000000000000001 of a second”[]
  20. ICRC, The effects of nuclear weapons on human health, 19 Mar 2013,[]