Final answer:
Carbon monoxide decreases the affinity of hemoglobin for oxygen.
Step-by-step explanation:
One effect of carbon monoxide is to decrease the affinity of hemoglobin for oxygen. Carbon monoxide has a greater affinity for hemoglobin than oxygen, so when carbon monoxide is present, it binds to hemoglobin preferentially over oxygen. This prevents oxygen from binding to hemoglobin and reduces the amount of oxygen transported through the body.