In far east where mask wearing is habitual, I have not heard that they suffer any increased health problems. You can dissect the effectiveness of masks on a scientific level as much as you want. But on a practical level I think what has happened is that the pros have outweighed the cons which is why the government stance has changed. We are increasing our understanding of covid transmission all the time and so its not just droplet but fine aerosol suspended now. In other words the invisible vapour of our breath. Thats what the mask does...arrests the vapour.