Thank you.
I also appreciate the excellent testimony we've heard from all of you today. Thank you for that.
I'm going to try to pick up a few themes that haven't been discussed as much.
Dr. Grandvaux, first of all you talked about the need to improve air quality and how we can move towards matching what we have achieved in public health in water quality. I think one difficulty is arriving at standards. I wonder if you could reflect on that a little bit.
We know that there's already a tremendous variety in air quality, depending on the size and age of the building. How do we develop standards so we actually know what we're aiming for, rather than a more general improving air quality kind of question?