The Environment and Health - Air pollution

Air pollutants can damage health in a number of ways. Even where little scientific proof links these pollutants to specific maladies, much statistical or circumstantial evidence suggests that air pollution can lead to various forms of respiratory disease. Some cases of air pollution outside the workplace and exclusive of nuclear radiation hazards have been documented.

Inversions

An inversion is a freak weather condition in which a mass of warm air rests like a lid on top of cooler air. The warm air traps the lower air and prevents the pollutants in it from being ventilated. The results can be deadly, as in 1948 in Donora, Pennsylvania. Situated in a valley, at the center of an industrial complex, the town found its air becoming more and more polluted over a six-day period, as daytime visibility dwindled to a few yards. Residents eventually had difficulty breathing; more than half of the valley's 14,000 inhabitants were coughing and gasping for breath. Thousands were hospitalized and twenty-two persons died. Physicians used adrenalin to keep older people alive.

Sulfur Dioxide

Sulfur dioxide enters the air from many sources. In the main, however, it is spewed into the atmosphere when heavy fuel oil and coal are burned to provide heat, generate electricity, and provide industrial power. Large cities are especially vulnerable because of their concentrations of heavy industry.

Sulfur dioxide apparently irritates the lungs and leads to a reduction of the lungs’ oxygen-handling capacity. Persons who are particularly susceptible to carbon and sulfur dioxide-filled smogs are those suffering from bronchial asthma, chronic bronchitis, and emphysema. The respiratory systems of such persons are already defective. In emphysema, for example, the elasticity of the air sacs in the lungs has progressively broken down, usually after prolonged infection or repeated bronchial irritation. Cigarette smoking can produce such irritation; the sulfur dioxide only worsens the situation.

Lead

Substantial evidence indicates that lead in the air can cause neurological harm and impair body chemistry and bone growth. Most airborne lead comes from combustion of solid waste, coal, and oils; emissions from iron and steel production and lead smelters; and tobacco smoke. Children are most immediately affected because they have fewer natural defenses against toxic absorption than adults. But adults too may feel the effects of such absorption. They may, for example, feel tired, cramped, or confused.

Because their bodies absorb and metabolize substances rapidly, children may have rates of lead absorption four times as high as those of adults. Workers in some industries, including the ceramic, glass, and lead industries, are also at risk. One study showed that 44 percent of the lead workers in two U.S. smelters suffered from clinical poisoning.

Specific effects of lead poisoning range across a broad spectrum. The formation of red blood cells may be inhibited even by low-level exposure to lead in the air. At higher levels, lead may cause anemia. In children, bone cell growth may be stunted; in pregnant women, lead may prevent the normal development of the fetal skeleton. But lead affects the brain primarily, in some cases interfering with motor skills, auditory development, memory, and the nervous system. Children with higher levels of lead absorption have been found to have serious learning disabilities. Fortunately, lead levels may fluctuate, and the lead in blood and soft tissue may pass out of the human system four to six weeks after exposure ends. But lead remains in bone for periods lasting as long as three decades.

Other Fuel Contaminants

Auto exhausts are major sources of air pollutants. Exhaust emissions may include nitrogen oxides, carbon monoxide, hydrocarbons, and soot. The latter is made up of visible particles of carbon suspended in the air.

Nitrogen oxides irritate the eyes and the respiratory tract. When nitrogen oxide and hydrocarbons mix in sunlight, they form other noxious substances in the typical photochemical smog that has a yellowish cast. The new ingredients include ozone , a poisonous form of oxygen, and peroxyacetyl nitrate (PAN), which is intensely irritating to the eyes. Los Angeles was the first city to experience these smogs; they now occur in many other cities as well.

Worst of all, auto exhaust hydrocarbons include varieties that are possible carcinogens , causes of cancer in susceptible individuals.

Acid Rain

While so-called acid rain has not been found to harm humans directly, scientists say it has begun to damage the natural food chain in certain regions. As industrial smokestacks emit pollutants, including sulfur and nitrogen oxides, these rise into the upper atmosphere. Mixed with water vapor and other substances, the airborne chemicals are changed by sunlight, becoming tiny acid droplets. The droplets fall to earth as rain or snow, raising the acid content of freshwater lakes and damaging trees and other plants. Under conditions of extreme acidity, fish populations have disappeared; where the food web is disrupted, aquatic animals, algae, and bacteria may dwindle in number. The effects of acid rain on crops and trees are less apparent but are thought to be harmful.

To some extent, acid rain is a geographic phenomenon in North America. Factories in the midwestera industrial belt throw off most of the pollutants, which are then carried east and north. Southeastern Canada and the northeastern and eastern regions of the United States are the areas primarily affected.

Indoor Air Pollution

Reports of illness associated with office and other nonresidential buildings have given rise to what has been termed the “sick building syndrome.” The causes of this syndrome, or complex of symptoms, have not been completely and precisely explained. Among the possible explanations are the following:

1. • Building ventilation has been reduced to conserve energy, with the result that ventilation is simply inadequate
2. • Indoor air has become contaminated by emissions from the building fabric and associated systems, furnishings, office equipment, or maintenance materials
3. • Entrainment or cross contamination has taken place, with contaminants generated in a different part of the building or in a separate building drawn in by an air-handling system
4. • Bioeffluents, or volatile human substances, spread throughout a building, polluting the air with pyruvic acid, lactic acid, acetalde-hyde, butyric acid, carbon dioxide, and other body effluents
5. • Combustion byproducts from smoking tobacco have produced substances, smoke included, that contaminate indoor air
6. • Microorganisms or airborne particles from molds, dust mites, and other sources cause such illnesses as Legionnaires Disease

A common tendency has been to identify a public building's heating, ventilating, and air conditioning (HVAC) system as the cause of indoor air pollution. But that conclusion may be premature and overly nonspecific. The symptoms described by persons affected by the sick building syndrome should be studied closely. At least four separate illnesses have been isolated according to their symptoms and causes. Hypersensitivity Pneumonitis and Humidifier Fever usually produce such symptoms as coughing, wheezing, chest tightness, muscular aches, chills, headache, fever, and fatigue. While these conditions are rarely fatal, Legionnaires Disease, produced by the bacterum Legionella pneumonophilae, is notable because of its 15 to 20 percent mortality rate. Both Legionnaires Disease and the relatively less serious Pontiac Fever are identified by their pneumonia-like symptoms.

Carbon Monoxide

Carbon monoxide poisoning is one of the most common dangers of modern living. A colorless, odorless and tasteless gas produced whenever organic, or carbon-containing, substances burn, carbon monoxide can be lethal in poorly-ventilated spaces. The gas rapidly combines with hemoglobin to replace oxygen in the blood. The heart and the brain are most vulnerable, since they rely heavily on oxygen to function properly, and symptoms generally mimic those associated with impaired heart or brain functions: shortness of breath, nausea, headache, fatigue, weakness, dizziness, irritability, and reduced ability to concentrate. During winter is when most deaths attributed to carbon-monoxide poisoning occur, primarily due to clogged furnace exhaust systems and doors and windows too tightly sealed against the cold. Other common sources are tobacco smoke, motor vehicle exhaust, house fires, wood-burning stoves and fireplaces, factory machines with gas-powered engines, charcoal-burning barbecues, kerosene heaters and water heaters that run on gas or oil. Improvements in ventilation systems and public warnings to consumers have lowered the number of carbon monoxide deaths in recent years. In addition, most hardware stores sell carbon monoxide detection devices that sound an alarm when unsafe levels of carbon monoxide are reached. Many cities now require all homeowners and landlords to install them.

Secondhand Smoke

While it has long been established that cigarettes are harmful to smokers, only in the last two decades has research begun to establish the risks of cigarette smoke to non-smokers, those who passively inhale “second-hand” smoke. In 1986, the Surgeon General's Report examined the smoke inhaled directly by smokers and the smoke passively inhaled by nearby nonsmokers, concluding that the chemical composition of both types of smoke was similar enough to warrant further study and to issue a preliminary warning about the potential dangers. Since then, a heated debate has raged. While some research has linked passive smoking to an increased risk of diseases, including lung cancer, other research indicates a negligible effect. Despite the frequent contradictions in data, public opinion has sided with nonsmokers who fear potential harm from environmental tobacco smoke. Fewer and fewer public places even allow smoking and many places, including New York City, Boston, and the state of California have legislatively declared most public spaces to be smoke-free environments.

The only exception to the debate on the risks of passive smoking are very young children exposed to passive smoke. Studies have proven that pregnant women who smoke not only increase their risk of miscarriage and stillbirth, but also risk delivering infants with low birth-weight who, as a result, are highly susceptible to health and development problems. Infants and toddlers of smoking parents have an increased incidence of bronchitis and pneumonia and are much more likely to be hospitalized for respiratory infections than children of nonsmoking parents.

Household Chemicals

Depending on its location, structural characteristics, and other factors, the typical home may have as many as 350 or more organic chemical pollutants in its interior air. Household chemical products like spray paints, insecticides, and furniture polish disperse tiny (and toxic) droplets into the air, adding the propellant to the chemicals in the basic product. Among the hazard-producing chemicals, some solvents in particular are known or suspected carcinogens. One of the worst is methylene chloride, found in paint sprays and paint strippers and in some hair sprays and insecticides. Product labels may identify methylene chloride as a “chlorinated solution” or as “aromatic hydrocarbons.”

Radon

After cigarette smoking, say scientists, the second leading cause of lung cancer may be radon gas. Considered by many to be the most dangerous of all indoor air pollutants, radon, a naturally occurring radioactive gas, diffuses out of the ground into houses that happen to be built above subsurface sources.

Invading homes, according to the U.S. Environmental Protection Agency, radon causes between 5,000 and 20,000 lung cancer deaths annually. The gas breaks down into unstable elements called “radon daughters”; these become attached to particles of dust or other matter floating in the air. If breathed in, the radon daughters lodge in the linings of the lungs. Radioactive decay takes place almost at once, with the daughters emitting alpha particles that damage the adjacent lung cells, sometimes causing cancer.

Private homes can be tested for radon and, if hazardous levels are found, can be equipped with ventilation or other equipment to remove the health threat. A charcoal-based detector is available. Finally, many firms can conduct home radon checks for a fee.