Transport of Oxygen As blood approaches the lungs, the carbon dioxide content declines, causing the pH to rise. Through the Bohr effect, this increase in pH enhances hemoglobin's affinity for oxygen, prompting hemoglobin to take up oxygen entering your blood from your lungs and deliver it to your tissues. As you breathe out, carbon dioxide levels in your blood rise, causing the pH to fall. Again through the Bohr effect, this decrease in pH reduces hemoglobin's affinity for oxygen, forcing it to release its bound oxygen back into your lungs where it can be exhaled with each breath. In conclusion, pH affects oxygen-binding to hemoglobin because as acidity increases so does the ability of hemoglobin to bind with oxygen.