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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.

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INDOOR AIR POLLUTION

Children spend substantial amounts of time indoors, at home and at school in particular. One study estimated that children are indoors, especially at home, 85 percent of the day -time spent indoors decreasing with age.[109] Awareness about indoor air quality has increased considerably in the last fifteen years, particularly with the development of more energy-efficient homes and buildings that have reduced rates of exchange between indoor and outdoor air. Some of the typical indoor air pollutants include environmental tobacco smoke, wood smoke containing particulates, carbon monoxide, and volatile organic compounds, nitrogen oxides (from unvented gas-burning stoves and heaters), respirable particles (from cooking fumes and household dust), formaldehyde (from pressed wood products and furniture, environmental tobacco smoke, urea-formaldehyde foam insulation, and permanent-press fabrics), and volatile organic compounds (from paint, paint strippers, solvents, wood preservatives, aerosol sprays, cleansers and disinfectants, moth repellents and other pesticides, and air fresheners).

Studies have found that levels of certain pollutants are far greater indoors than outdoors. With volatile organic chemicals, indoor personal exposures were typically two to five times outdoor levels.[110] For highest personal exposures, such as during or after paint stripping, solvent levels may be a thousand times background outdoor levels.[111] The EPA's Total Exposure Assessment Methodology (TEAM) studies have shown that for 18 chemicals, median indoor air concentrations ranged from two to twenty times higher inside homes than outdoors.[112] Persons wearing or storing freshly dry-cleaned clothes had significantly higher exposures to tetrachloroethylene, and persons using mothballs and bathroom toilet deodorants had greatly increased exposures to paradichlorobenzene.[113] Another TEAM study showed that exposure to chloroform is mainly due to the chlorination of drinking water and that inhalation exposure during a shower is comparable to drinking two liters of tap water a day.[114]

The EPA does not have authority to regulate indoor air quality directly (although it can control some sources of indoor air pollution such as airborne releases of volatile organic chemicals from drinking water). No federal law requires the Agency to establish indoor air quality standards. To date, the EPA's efforts to improve indoor air quality have focused primarily on research, coordination between different federal agencies, and public education. The potential risks to children from indoor air pollutants are significant. Clearly the federal government needs to take more action, including setting standards to limit airborne releases of chemicals from products used indoors such as pressed wood products and furniture, paints, solvents, paint strippers, cleansers, and disinfectants.

Our Children At Risk : The Five Worst Environmental Threats to Their Health. By Lawrie Mott, David Fore, Jennifer Curtis, Gina Solomon. November 1997. Print version, $14.00. Order print copies .

last revised 11/25/1997