Better yet are the time bombs which only manifest down the line. Like EE2 and fertility. If Gen 0 is blasted with a dose of EE2, subsequent generations have a continuous drop in fertility each generation despite themselves never being exposed. 

 that seems a bit hyperbolic; what is the route to causing fertility disuption? What I've heard that makes sense is that stuff like Ethinylestradiol are extremely stable and break down very slowly. Which is a problem, but not an unsolvable one. 

 Transgenerational epigenetic inheritance