 The study found that wearing a face mask can cause changes in breathing patterns, but these changes are not harmful. When worn during light work, there was no effect on blood gasses. However, when worn during moderate or heavy exercise, the mask caused a slight decrease in blood oxygen levels, but this did not pose any health risks. This article was authored by Ike Maximilian Marek, Vera Van Kampen, Burji Jetkant, and others.