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Spaghetti Scenarios · Global risk

Catastrophic nanotechnology

Molecule-sized machines that slip out of control: the best-known image is of nanorobots copying themselves until they consume everything in their path. That idea never left the page. What does exist are materials made at the scale of millionths of a millimetre, and equally small plastic fragments, that are already reaching the human body and whose effects are still poorly understood.

Self-copying nanorobots still do not exist; plastic in tiny particles is already being measured in brains, placentas and arteries.

Nano-bio-AI convergence

2024

year in which the Nobel Prize in Chemistry rewarded computer design of new proteins and the prediction of their shape with artificial intelligence. Since 2006, DNA has also been folded to build shapes of about 100 nanometres.

Sources: Real Academia Sueca de Ciencias ↗ · Nature ↗

What was imagined and what was proven

The most famous threat never got past theory; the measured risks arrived by another route.

  1. 1959A physicist suggests in a lecture that matter could be manipulated atom by atom: "there's plenty of room at the bottom".
  2. 1981The scanning tunnelling microscope is invented, making it possible to see atoms one by one. Its creators receive the Nobel Prize in Physics in 1986.
  3. 1986A book imagines molecular assemblers able to copy themselves and warns that, out of control, they could wipe out the biosphere: the idea of "grey goo" is born.
  4. 1989Researchers write three letters with 35 xenon atoms placed one by one, at 4 degrees above absolute zero.
  5. 2004The idea's author writes that self-copying is unnecessary and that dangerous self-replicating nanomachines should be prohibited. A scientific review finds no evidence they will exist.
  6. 2016Nobel Prize in Chemistry for the first molecular machines: rings, axles and motors made of a single molecule that move when they receive energy.
  7. 2020The European Union begins requiring specific safety data for the nano forms of each chemical substance.
  8. 2022The European Union updates its definition of nanomaterial and withdraws titanium dioxide from food because damage to genetic material cannot be ruled out.
  9. 2024Plastic is measured in all 62 placentas of one study and in the artery plaques of patients who later suffer more heart attacks, strokes or deaths.
  10. 2025Brain samples contain 7 to 30 times more plastic than liver or kidney. In November, other specialists question the method.
  11. 2025Volume production begins of chips from the so-called "2 nm" generation, with a new type of nanosheet transistor.

Sources: Reino Unido ↗ · Real Academia Sueca de Ciencias 1986 ↗ · Anchor Press/Doubleday ↗ · Robert A. Freitas Jr. ↗ · IBM Research ↗ · Nature ↗ · Nanotechnology ↗ · Real Academia Sueca de Ciencias 2016 ↗ · Diario Oficial de la Unión Europea 1 ↗ · Diario Oficial de la Unión Europea 2 ↗ · EFSA ↗ · Diario Oficial de la Unión Europea 3 ↗ · Garcia et al. ↗ · Marfella et al. ↗ · Nature Medicine 1 ↗ · Nature Medicine 2 ↗ · TSMC ↗ · IEEE Spectrum ↗

How small is a nanometre

Size of some things, in nanometres (millionths of a millimetre). Six orders of magnitude separate an atom from a sheet of paper, so the scale is logarithmic.

Gold atom0.3 nm
Width of DNA2.5 nm
Limit of "nano"100 nm
Plastic fragments found in the brainup to 200 nm long
Most measure under 200 nm long and 40 nm wide.
Red blood cell7,000 nm
Width of a hair80,000 nm
Thickness of a sheet of paper100,000 nm

Logarithmic scale: each step is ten times the previous one.

Chips of the so-called "2 nm" generation do not have 2-nanometre parts: it is a commercial name and their real features are considerably larger.

Sources: EE. UU. ↗ · Reino Unido ↗ · Diario Oficial de la Unión Europea ↗ · Nature Medicine ↗ · IEEE Spectrum ↗

Plastic measured in human tissue

Micrograms of plastic per gram of tissue (central value of each group of samples). The brain accumulates far more than other organs, and more in 2024 than in 2016.

Placenta63.4 µg/g
Testis299 µg/g
Kidney (2024)404 µg/g
Liver (2024)433 µg/g
Brain (2016)3,345 µg/g
Brain (2024)4,917 µg/g
Brain with dementia (2019–2024)26,076 µg/g
Only 12 cases. The authors do not attribute dementia to plastic: a diseased brain might retain more of it.

Logarithmic scale: each step is ten times the previous one.

Samples from deceased people in the United States. The method measures the mass of plastic, not the number of particles, and in 2025 other specialists questioned its reliability. The placenta and testis figures come from earlier studies cited by the same paper.

Sources: Nature Medicine 1 ↗ · Nature Medicine 2 ↗ · Garcia et al. ↗

Plastic in the arteries

58 out of 100 in every 100 patients operated on to clear an artery in the neck had plastic in the plaque blocking it. Over the following 34 months, their risk of heart attack, stroke or death was 4.5 times that of those without it.

Study of 257 patients followed for almost three years. It shows an association; it does not prove plastic is the cause.

Source: Marfella et al. ↗

What the rules already set

50%of particles must measure between 1 and 100 nanometres for a material to count as nano in the European Union
2020year since which specific safety data have been required for each nano form of a substance
2022year titanium dioxide, with up to half of its particles nano-sized, was removed from the list of food additives

These are European Union rules. There is no global register of nanomaterials and no international exposure limit for nanoplastics.

Sources: Diario Oficial de la Unión Europea 1 ↗ · Diario Oficial de la Unión Europea 2 ↗ · EFSA ↗ · Diario Oficial de la Unión Europea 3 ↗

Scenario profile

ImpactMajor (4)
NegligibleMinorModerateMajorCatastrophic
ProbabilityUncertain
RemoteUnlikelyPossibleVery likelyAlmost certainUncertain: there is not enough basis to rate it
Confidence in the evidenceLow
LowMediumHigh
WhenDecades
Where it leadsGrows / Stagnates depending on response
ReversibilityPartially reversible

Catastrophic nanotechnology

Impact
Major (4)
Probability
Uncertain
Timeframe
Decades
Score
N/A
Confidence
Low
Reversibility
Partially reversible

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.

  • Molecular assembly and self-replication
  • Regulation of nanomaterials
  • Human exposure to nanoplastics
  • Nano-bio-AI convergence

Possible human action

  • Prohibit the design of autonomous machines able to copy themselves
  • Assess the safety of each nanomaterial before it is sold
  • Measure human exposure with common, verifiable methods
  • Monitor the merging of nanotechnology, synthetic biology and artificial intelligence