Excretion by the lungs
The primary function of the lungs is to supply oxygen rich air to the bloodstream and to remove gases produced by cellular metabolism-such as carbon dioxide-from the bloodstream. The exchange of gases occurs between the alveoli of the lungs and the extensive capillary system associated with them. Gas exchange is by passive diffusion; it occurs as a result of a concentration gradient for each gas between the air and the blood.
Excretion of volatile toxic gases, such as those associated with organic compounds, occurs in the lungs. The transfer of gases from the blood to the lungs is influenced by concentration gradients and by their solubility in water. Ethylene-which is only slightly soluble in water-will readily diffuse from the blood into the lungs and will therefore be easily removed.