What happens to oxygen levels as altitude increases?

As altitude increases, the concentration of oxygen in the atmosphere decreases. This occurs because the atmospheric pressure drops with elevation, leading to a reduction in the overall density of air molecules, including oxygen. Although the proportion of oxygen in the air remains roughly the same at higher altitudes (about 21% of the atmosphere), the total number of air molecules decreases, which results in lower partial pressure of oxygen. Consequently, individuals at high altitudes may experience difficulty in breathing due to this reduced availability of oxygen, which can lead to altitude sickness if the body does not acclimatize properly. This phenomenon is well-documented in both atmospheric science and physiology, making it essential to understand the relationship between altitude and oxygen levels.