Roaches are building immunity to bug spray

(CNN) - You've probably heard cockroaches can survive a nuclear bomb.

Roaches are becoming harder to kill, a recent study has determined. (Source: CNN/file)

While that’s not scientifically proven, scientists at Purdue University discovered German cockroaches are becoming resistant to insecticides.

Even more horrifying: They can become cross-resistant to chemicals to which they haven’t even been exposed.

They pass those immunities onto their offspring, creating new generations of evolved super-roaches.

Researchers worry this will some day make it difficult - or impossible - to control the bugs with chemicals alone.

They say the best thing to do is combine preventative measures like sanitation and physical methods like traps with insecticides.

Copyright 2019 CNN. All rights reserved.