Blather, rinse, repeat

Well, there's also Radon, lead (knock on wood), VOCs, formaldehyde... the first two are the most nasty... the last two not so much, but they are common because some "wood" and particle-board furniture and fabric/insulation materials outgas/offgas them. I can't remember all the effects of these pollutants, but of course they may affect animals differently from humans.

Trying to think of what else. Are birds OK with essential oils?