Why is research hazardous to the villagers?

I got that by clicking on that green and purple mask on the left of the Name, Skill, Action window.

And what does it mean when some of my villagers are weakened even if there's food?

wow - never realized that clicking the mask would do anything - that's cool

concerning the reserch: maybe not every result returned is favorable - they could find diseases, hurt themselver on tools they're using, develop a hayfever with all the flower they're carrying around....

They become weakened by injuring themselves (this applies to the more hazardous occupations of researching and building, but not the others), starvation, and sickness. Events can also sometimes weaken one or more villagers. Sickness, if uncured by a doctor, can keep weakening a villager until they die. Industrial injuries usually heal over a period of time.

Research is hazardous due to several reasons. One would be the flumes they are taking in while researching. Another would be getting chemical spills touching the exposed skin. I have not seen any of my researchers every ware gloves, eye protection or any sort of facemask, so it has to be very dangerous.

I really meant if it really affects the villagers health... is that because some villagers are weakened by research?

I'm aware that the villagers can be weakened due to hunger or untreated illness...

Thanks for the prompt replies

Yes, it really affects their health. They will get injured at the table. Each time they get injured, their health bar will decrease. If they get injured several times in a short time period, they will get to the weakened state.