I wouldn't be surprised if chronic inhalation of natural lemon or pine scent were unhealthy too. Limonene can cause skin irritation for example. Plants generall

I wouldn't be surprised if chronic inhalation of natural lemon or pine scent were unhealthy too. Limonene can cause skin irritation for example. Plants generally evolved essential oils to avoid being eaten, it kind of makes sense that inhaling them might be unhealthy.