One main disadvantage is that oxygen must be present, and this type of respiration is not possible for species that live in environments without oxygen. Another disadvantage is that it takes longer times to release energy, compared to anaerobic respiration which occurs quickly. It also requires a large amount of oxygen, as 95% of the oxygen humans consume is used during respiration. Lastly, ROS such as hydrogen peroxide and superoxide anion are believed to be byproducts of aerobic respiration, resulting in harmful effects on DNA, lipid, and protein.