With this option removed, there is a growing concern that homeowners may be tempted to burn the leaves in their yards. Leaf smoke also contains carbon monoxide. If inhaled, these microscopic particles can reach the deepest regions of the lung and remain there for months or even years. Breathing particulate matter can increase the chances of respiratory infection, reduce the volume of air inhaled and impair the lungs' ability to use that air. Particulate matter can also trigger asthma attacks in some people.
Hydrocarbons are chemicals that can exist as both gases and solid particles.
Because leaves are often moist and burn without proper air circulation, they often burn poorly, producing high levels of hydrocarbons. Some of these hydrocarbons, such as aldehydes and ketones, cause irritation of the eyes, nose, throat, and lungs. A substantial portion of the hydrocarbons in leaf smoke consists of polynuclear aromatic hydrocarbons, some of which are known carcinogens. Carbon monoxide is absorbed into the bloodstream through the lungs and combines with red blood cells. This reduces the amount of oxygen the red blood cells can absorb and supply to body tissues.