Nuclear weapons are bad because their effects extend far beyond the initial explosion, causing mass civilian death, long-term radiation illness, global famine, and environmental damage that persists for decades. No other weapon created by humans can kill billions of people in a matter of hours or alter the planet’s climate for years afterward. As of January 2025, an estimated 12,241 nuclear warheads exist worldwide, with roughly 2,100 kept on high alert and ready to launch at any moment.
The Blast Destroys Everything for Miles
A nuclear detonation produces a pressure wave that radiates outward at supersonic speed. Just 1 pound per square inch (psi) of overpressure is enough to shatter windows across a wide radius. At 5 psi, concrete walls and buildings collapse entirely. A modern warhead is hundreds of times more powerful than the bombs dropped on Hiroshima and Nagasaki, meaning these destruction thresholds extend for miles from the detonation point. Within that zone, virtually every structure is flattened and virtually every person is killed.
The blast is followed by a thermal pulse, a flash of heat intense enough to ignite fires across a vast area. These fires can merge into a single massive firestorm that consumes all available oxygen and fuel. People far enough from the blast to survive the pressure wave can still die from burns or building collapse caused by the heat and subsequent fires.
Radiation Sickness Kills in Stages
Survivors near the blast zone face a slower threat: acute radiation syndrome. The severity depends on the dose absorbed. At moderate exposures, the body’s blood cell production drops sharply over the following weeks, leaving a person unable to fight infection or stop bleeding. Nausea and vomiting begin within hours, followed by a deceptive period where symptoms temporarily ease before the full illness sets in. At this level, roughly half of exposed people die within 60 days without intensive medical care.
At higher doses, radiation destroys the lining of the digestive tract. Severe diarrhea, dehydration, and systemic infection follow rapidly. At approximately 10 gray (a unit measuring absorbed radiation), the fatality rate reaches 100 percent, with death occurring within two weeks. There is no effective treatment at this level. In a real nuclear attack, hospitals within the affected area would be destroyed or overwhelmed, meaning even treatable radiation injuries would go untreated for most people.
Cancer Risks That Last a Lifetime
Studies of atomic bomb survivors from Hiroshima and Nagasaki provide the clearest picture of long-term health effects. Among those who survived the initial blast and acute radiation, excess leukemia deaths appeared within just a few years. Of 315 leukemia deaths tracked in the long-running Life Span Study, an estimated 45 percent were directly attributable to radiation exposure. Solid cancers followed, with statistically significant increases in cancers of the bladder, breast, lung, brain, thyroid, colon, esophagus, stomach, liver, and ovary.
The risk doesn’t require high doses. Researchers found a significant dose-response relationship even in the lowest exposure range studied, from 0 to 0.15 gray, meaning there was no clear “safe” threshold below which cancer risk disappeared. Some survivors continued to develop radiation-linked blood disorders 40 to 60 years after exposure, underscoring how far into the future the health consequences reach.
Radioactive Fallout Contaminates Food for Decades
A nuclear explosion lofts radioactive debris into the atmosphere, which then settles over a wide area as fallout. The most dangerous long-lived contaminants are strontium-90 and cesium-137, both of which have half-lives of about 30 years. That means they remain hazardous for well over a century before decaying to negligible levels.
These isotopes enter the food chain through multiple routes. They settle directly onto crops, are absorbed through plant roots from contaminated soil, and accumulate in the meat and milk of animals grazing on contaminated vegetation. The primary way people are exposed is not through breathing in fallout particles but through eating contaminated food. In the aftermath of a nuclear war, vast agricultural regions would become unsafe for food production for generations.
Global Famine Could Kill Billions
The consequences of nuclear war are not limited to the countries involved. The fires ignited by nuclear strikes would inject massive amounts of soot into the upper atmosphere, where it would spread globally and block sunlight. Climate models show that a full-scale war between the United States and Russia could drop global average temperatures by more than 8°C (about 14°F), plunging the planet into what scientists call nuclear winter. Sunlight would be significantly reduced for months to years.
The agricultural impact would be catastrophic. Even a relatively limited nuclear exchange (producing around 5 million tons of soot) would reduce global crop calorie production by 7 percent in the first five years. A large-scale war producing 150 million tons of soot would destroy roughly 90 percent of global crop production within three to four years. A 2022 study published in Nature Food estimated that a war between India and Pakistan could put more than 2 billion people at risk of famine, while a U.S.-Russia war could endanger more than 5 billion. Most of those deaths would occur in countries that had nothing to do with the conflict, in Africa, South America, and Southeast Asia, where food reserves are thinnest.
The Scale of Today’s Arsenals
Nine countries possess nuclear weapons. The United States and Russia together hold almost 90 percent of the global total. Of the roughly 12,241 warheads in existence as of January 2025, about 9,614 are in active military stockpiles. Around 3,912 are deployed on missiles and aircraft, ready to be used. The remaining stockpiled warheads sit in central storage but could be loaded and launched within days or weeks.
The roughly 2,100 warheads kept on high operational alert are the most concerning from a safety standpoint. These are mounted on ballistic missiles that can be launched within minutes of a presidential order. This posture exists because both the U.S. and Russia maintain a “launch on warning” capability, designed to retaliate before incoming missiles arrive. The compressed decision-making timeline, sometimes as short as 10 to 15 minutes, means a false alarm or miscommunication could trigger a launch before anyone fully verifies the threat. This has nearly happened more than once during the Cold War.
Why International Law Now Prohibits Them
The Treaty on the Prohibition of Nuclear Weapons, which entered into force in 2021, makes nuclear weapons illegal under international law for the countries that have joined it. The treaty emerged directly from a growing international focus on the humanitarian consequences of any nuclear weapon use. It requires member states to assist individuals affected by nuclear weapon use or testing, and to undertake environmental cleanup of contaminated areas.
None of the nine nuclear-armed states have signed the treaty, which limits its immediate practical effect. But it establishes a legal norm that classifies nuclear weapons alongside chemical and biological weapons as fundamentally unacceptable. The core argument is straightforward: no military objective can justify a weapon whose effects are indiscriminate, whose radiation cannot be contained to a battlefield, and whose climatic consequences threaten the food supply of the entire planet.