Effects of Air Pollutants - Health Effects

Exposure to air pollution is associated with numerous effects on human health, including pulmonary, cardiac, vascular, and neurological impairments. The health effects vary greatly from person to person. High-risk groups such as the elderly, infants, pregnant women, and sufferers from chronic heart and lung diseases are more susceptible to air pollution. Children are at greater risk because they are generally more active outdoors and their lungs are still developing. Exposure to air pollution can cause both acute (short-term) and chronic (long-term) health effects. Acute effects are usually immediate and often reversible when exposure to the pollutant ends. Some acute health effects include eye irritation, headaches, and nausea. Chronic effects are usually not immediate and tend not to be reversible when exposure to the pollutant ends. Some chronic health effects include decreased lung capacity and lung cancer resulting from long-term exposure to toxic air pollutants. The scientific techniques for assessing health impacts of air pollution include air pollutant monitoring, exposure assessment, dosimetry, toxicology, and epidemiology.

Figure:Health Effects caused by Air Pollution

Although in humans pollutants can affect the skin, eyes and other body systems, they affect primarily the respiratory system. Air is breathed in through the nose, which acts as the primary filtering system of the body. The small hairs and the warm, humid conditions in the nose effectively remove the larger pollutant particles. The air then passes through the pharynx, esophagus, and larynx before reaching the top of the trachea. The trachea divides into two parts, the left and the right bronchi. Each bronchi subdivides into increasingly smaller compartments. The smallest compartments of the bronchi are called bronchioles, which contain millions of air sacs called alveoli. Together, the bronchioles and alveoli make up the lungs.

Both gaseous and particulate air pollutants can have negative effects on the lungs. Solid particles can settle on the walls of the trachea, bronchi, and bronchioles. Most of these particles are removed from the lungs through the cleansing (sweeping) action of "cilia", small hairlike outgrowths of cells, located on the walls of the lungs. This is what occurs when you cough or sneeze.

A cough or sneeze transports the particles to the mouth. The particles are removed subsequently from the body when they are swallowed or expelled. However, extremely small particles may reach the alveoli, where it takes weeks, months, or even years for the body to remove the particles. Gaseous air pollutants may also affect the function of the lungs by slowing the action of the cilia. Continuous breathing of polluted air can slow the normal cleansing action of the lungs and result in more particles reaching the lower portions of the lung.

Figure:Human respiratory system

In Table 1 we summarize the sources, health and welfare effects for the Criteria Pollutants. Hazardous air pollutants may cause other less common but potentially hazardous health effects, including cancer and damage to the immune system, and neurological, reproductive and developmental problems. Acute exposure to some hazardous air pollutants can cause immediate death.

Human health effects associated with indoor air pollution are: headaches, tiredness, dizziness, nausea, and throat irritation. More serious effects include cancer and exacerbation of chronic respiratory diseases, such as asthma. Radon is estimated to be the second leading cause of lung cancer in the U.S. Environmental tobacco smoke causes eye, nose and throat irritation, and is a carcinogen. Asthma, particularly in children, is associated with poor indoor air quality.