Well, being in the health industry, and knowing what's happening in regard to antibiotic resistance in bacteria, I'd talk about use of disinfectants and antiseptics in the home environment, and the potential impact on bacterial resistance. You could change the world by reducing the likelihood of more antiobitic resistant "superbugs" as the media calls them, by making the home environment less disinfectant/antiseptic ridden.
I can provide some real interesting website links if you are interested in this.
Cheers
Mick, the anti-disinfectant fanatic.