You can believe whatever you want, but most systems of justice recognize things like proportionality and imminence.
While a nearby coal power plant is likely to harm your health, it's unlikely to kill you, so killing someone over it would be disproportional.
Also, even if it were going to kill you, it's not going to kill you right now, so shooting on sight instead of exhausting other avenues would be avoidable and hence not self-defense or justifiable.
Most people would sympathize with you as a victim of this coal plant, but find you guilty of a crime.
While a nearby coal power plant is likely to harm your health, it's unlikely to kill you, so killing someone over it would be disproportional.
Also, even if it were going to kill you, it's not going to kill you right now, so shooting on sight instead of exhausting other avenues would be avoidable and hence not self-defense or justifiable.
Most people would sympathize with you as a victim of this coal plant, but find you guilty of a crime.