I copy and pasted your code.
Added a main function:

void main(){
level_load(NULL);
effect_create(vector(1000,0,0));
while(1){
DEBUG_VAR(num_particles,100);
wait(1);
}
}

So I could see if it was working and there doesn't seem to be any issues with the code...

You don't happen to call the function "effect_create(some_vector)" multiple times (like in a while loop) do you? because that would spam create entities that all produce particles.

EDIT: I see you posted again....I may change this post.