Issues: Health

HOW LUNGS WORK

At rest, an infant's metabolic rate and air intake is about twice that of an adult.^[10] A forty-five pound child inhales over 9,000 liters of air per day.^[11] In so doing, the child brings oxygen into the body and eliminates carbon dioxide and other unneeded gases. When a child's respiratory system works well, air ultimately reaches tiny air sacs nestled in the lungs, which in turn deliver oxygen to red blood cells. These sacs, called alveoli, are where the body exchanges precious oxygen for spent carbon dioxide.

On its way to the alveoli, air passes through the nose and mouth, down the throat to the pharynx, and then through the windpipe, or trachea. At this point, the air will move through a system of branching airways of bronchi and bronchioles, and then finally to the alveoli themselves. Air passes across the alveolar walls, which are laced with tiny pulmonary capillaries that carry blood cells that take up the oxygen and unload carbon dioxide and other gases. When a breath is exhaled, the cycle is complete.

A healthy child's respiratory system is replete with filtering structures that protect the fragile composition of the deep lung. In addition to warming and humidifying the air, the nose, mouth, and upper airways remove the very largest particles from the airstream. Delicate microscopic, hairlike structures called cilia line the trachea, bronchi, and bronchioles. These cilia propel small particles and pollutants deposited on a moving layer of mucus upwards to the epiglottis, where the mucus is swallowed or expectorated.

Problems arise when air pollutants such as ozone, nitrogen dioxide, and particulate matter enter the respiratory system and damage these filtering structures. The passages swell and narrow, constricting the movement of air into and out of the deep structures of the lung. Common air pollutants such as particulate matter can pass into the deep structures of the lung unhindered. When this happens, the risk of pneumonia and other respiratory infections increases. Coughing, wheezing, sore throats, shortness of breath, and exacerbation of asthma can arise when pollutants settle upon and are absorbed by the delicate membranes of the respiratory tract. The normal function of a child's lungs, as well as his or her ability to exercise, can be diminished when exposed to pollutants over time.