A lot depends upon what quantities you use it in, as with most everything.
At 1.8% (18,000 ppm) , glutaraldehyde is a rather potent surgical grade disinfectant, and kills everything it touches.
At >1ppm, it breaks down rather readily into carbon, and doesn't kill much of anything.
Similarly, replacing air with water drowns mammals.
Having small quantities of water evaporated in air aids their breathing.
Of course, there are those who don't like glut, and there are plants that have a hard time with even 1ppm of the stuff (vals, anacharis). However, most plants benefit from it unless there's CO2 injection going on.