Really? Tell him to start wearing a face mask. The air he's breathing right now has more "particles" than vapor--please send him the results of the USC study (below):
Here are all the data from the USC study, including Compounds, Outdoor air, e-Cigarette, and normal cigarette.
http://www.rsc.org/suppdata/em/c4/c4em00415a/c4em00415a1.pdf
For your convenience, listed below are the amounts of Cr, Ni, Pb, Zn and Al in outdoor air vs e-cigarette vapor:
Cr: 5.53 vs 4.22
Ni: 5.57 vs 6.14 (+/-2.9)
Pb: 13.28 vs 9.85
Zn: 54.31 vs 56.08 (+/- 21 [sic])
Al: 333.27 (±62.93) vs 161.43 (±71.35)
So, vapor is actually healthier, per this study, than the air we breathe here in SoCal.
So does the carpet in his office. And his bookcases. And the exhaust fumes from his car. Tons of formaldehyde and who knows what else.
Of course we will. As people live longer, eat unhealthy food and don't exercise, heart disease and cancer rates will keep going up.
Dual use is better than exclusive use of combustible tobacco products.