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Spaghetti Scenarios · Global risk

Terrorism with weapons of mass destruction

A terrorist group obtains a chemical, biological, radiological or nuclear weapon and uses it against a city. The best-known case, sarin gas on the Tokyo subway in 1995, killed 13 people and injured thousands; the fear is that a group could obtain more powerful materials, capable of causing mass deaths, panic and years of clean-up.

Since 1993, 4,626 cases of nuclear or radioactive material out of control have been recorded. Declared chemical weapons have been destroyed, but remnants still need checking.

Nuclear or radioactive material out of control

236

incidents reported in 2025 by 34 countries: thefts, losses, illegal sales or discoveries of nuclear or radioactive material. They total 4,626 since 1993.

■ About 180 a year since 2008; the 2025 rise is due to old cases reported late

Source: OIEA ↗

Trafficking for illicit purposes

6

confirmed incidents of trafficking or malicious use in 2025 (359 since 1993). They include 13 cases with highly enriched uranium; the last one involving kilograms of weapons-usable material was in 1994.

■ At historically low levels: between 2 and 8 a year since 2017

Source: OIEA ↗

Uncontrolled chemical weapons remnants

Over 100

sites in Syria may have been part of the former chemical weapons programme and must be checked, with possibly large quantities of undeclared agents. Inspectors have visited 20 since March 2025.

▲ Since 2025 the new Syrian government has cooperated with inspectors; in July 2026 it regained its rights under the treaty

Sources: OPAQ 1 ↗ · OPAQ 2 ↗

Deaths from terrorism

5,582

people died in terrorist attacks in 2025, the lowest figure since 2007. More than half were in Africa's Sahel.

▲ 28% fewer than in 2024; the peak was 10,882 in 2015

Source: IEP ↗

Nuclear and radioactive material out of control, 1993–2025

Incidents reported each year by countries. The lower line counts only cases of trafficking or malicious use. Move the slider to see each year.

050100150200250300199320002007201520252366
  • All incidents236incidents in 2025
  • Trafficking or malicious use6incidents in 2025

The 2006–2007 jump is due to a change in one country's reporting practice, and the 2025 jump to old cases reported late. More detectors at borders and scrapyards also increased reporting.

Source: OIEA ↗

The 4,626 incidents reported since 1993

Most are control failures —lost sources, contaminated scrap, unauthorised shipments—, not attempts to build a weapon. But one in thirteen involved trafficking or malicious use.

  • Trafficking or malicious use359
  • Unknown intent (almost all thefts or losses)1,120
  • Unrelated to trafficking or malicious use3,147

More than half of thefts occurred during authorised transport of the material (almost 70% in the past decade).

Source: OIEA ↗

The attacks that did happen

13 deadand more than 5,800 injured by sarin gas on the Tokyo subway (1995)
5 deadand 17 sickened by anthrax letters in the United States (2001)
~50 shellsof artillery, several filled with mustard gas, fired by Islamic State at Marea, Syria (2015)

All three used chemical or biological agents.

Sources: Agencia de Inteligencia de Seguridad Pública ↗ · FBI ↗ · Consejo de Seguridad de la ONU ↗

Deaths from terrorism worldwide

People killed in terrorist attacks, selected years. Almost all in countries at war or in conflict.

2015 (peak)10,882
20238,654
20247,714
20255,582
The lowest figure since 2007

Only 1% of 2025 deaths occurred outside conflict-affected countries. These figures do not distinguish the type of weapon.

Source: IEP ↗

Attacks and rules

The best-known attacks and the agreements created to keep terrorists out.

  1. Mar. 1995A cult releases sarin gas on three Tokyo subway lines: 13 dead and more than 5,800 injured.
  2. 1997The convention banning chemical weapons enters into force.
  3. 2001Anthrax letters in the U.S. mail: 5 dead and 17 sickened, the worst biological attack in the country's history.
  4. Apr. 2004The UN Security Council forbids all countries from supporting in any way non-state groups seeking nuclear, chemical or biological weapons.
  5. Jul. 2007The international convention against nuclear terrorism enters into force.
  6. Aug. 2015Islamic State uses mustard gas against the Syrian town of Marea, according to a joint UN investigation.
  7. May 2016The obligation to protect nuclear material also within each country (use, storage and transport) and to punish sabotage enters into force.
  8. Jul. 2023The destruction of all declared chemical stockpiles is verified: more than 72,000 tonnes.
  9. Today · October 2026
  10. 2025–2026After the fall of Syria's former government, inspectors begin checking more than 100 sites of its chemical programme; in July 2026 Syria regains its rights under the treaty.in progress
  11. Nov. 2032The current mandate of the UN committee that monitors countries' compliance with the 2004 resolution expires.planned

Sources: Agencia de Inteligencia de Seguridad Pública ↗ · OPAQ 1 ↗ · FBI ↗ · Consejo de Seguridad de la ONU 2026 ↗ · Colección de Tratados de la ONU ↗ · Consejo de Seguridad de la ONU 2016 ↗ · World Nuclear News ↗ · OPAQ 2 ↗ · OPAQ 3 ↗

Scenario profile

ImpactModerate (3)
NegligibleMinorModerateMajorCatastrophic
ProbabilityUncertain
RemoteUnlikelyPossibleVery likelyAlmost certainUncertain: there is not enough basis to rate it
Confidence in the evidenceMedium for the mechanism; low for the probability
LowMediumHigh
WhenCan happen at any time
Where it leadsGrows / Stagnates depending on response
ReversibilityReversible: damage would be local or regional, although cleaning up a contaminated area can take years

Terrorism with weapons of mass destruction

Impact
Moderate (3)
Probability
Uncertain
Timeframe
Can happen at any time
Score
N/A
Confidence
Medium for the mechanism; low for the probability
Reversibility
Reversible: damage would be local or regional, although cleaning up a contaminated area can take years

Trajectory, timeframe, confidence, reversibility and human action: proposed by the research, because the catalogue does not define them yet. Impact and probability are the catalogue's.

Signals to watch

Proposed by the research: the profile does not define its signals yet.

  • Nuclear or radioactive material out of control
  • Trafficking for illicit purposes
  • Uncontrolled chemical weapons remnants
  • Deaths from terrorism
  • Agreements against weapons of mass destruction

Possible human action

  • Secure and track radioactive sources, especially during transport
  • Finish destroying the remnants of chemical arsenals (Syria)
  • Detectors at borders and in metal recycling
  • Share information between countries on thefts and trafficking