The researchers found that almost all of the studies exceeded that standardFace masks may raise the risk of stillbirths, testicular dysfunction and cognitive decline in children, 'explosive' new research suggests. They point out that CO2 also contributes to oxidative stress, which can affect cognition and cause testicular issues in men. But the study could not conclusively prove that the masks were directly responsible for any of these complications. One mask study conducted in Germany, researchers measured the CO2 concentration of air behind surgical masks worn by 15 healthy men. In total, the researchers looked at studies dating back from the start of the scientific databases they searched until November 30, 2021.