Nuclear weapons produce lethal levels of heat and blast, produce radiation and radioactive fallout, exterminate civilian populations, produce social disintegration, contaminate and destroy the food chain, and continue for decades after their use to induce health-related problems.
Even 20 years after detonation, nuclear weapons still have health effects.
The text says that decades after their use nuclear weapons continue to induce health-related problems. "Decades" [plural] includes 20 years; the model missed this.
( z1 affect :ARG0 ( z2 weapon :mod ( z3 nucleus ) ) :ARG1 ( z4 health ) :mod ( z5 still ) :time ( z6 after :op ( z7 detonate ) :quant ( z8 temporal-quantity :quant 20 :unit ( z9 year ) :mod ( z10 even ) ) ) )