Yeah, I wondered about that, too... the article specifically mentions the involvement of water (hydrolysis) in the process of micropaticle formation, but the splatter guard is of course exposed to the steam coming from the food, and some of that condenses and drops back on the food, so not using these plastic splatter guards is probably indicated. Covering the container with an inverted plate (making sure to leave some space for steam pressure to exscape) is probably better. I'm going to do that from now.