The Demon Rat (1992)

In a bleak near future the world has really gone to seed due to severe pollution. Toxic smog, acid rain, and grotesquely mutated animals are all direct results of this environmental decay. Ruthless industrialist Roberto Cervantes makes matters worse by illegally dumping plutonium. School teacher Irina and professor Axel try to stop Cervantes, and a giant lethal humanoid rat runs amok in Irina's house.