effects of air pollutants

Air pollution operates on a variety of scales, from the personal to the global and has serious consequences for the environment and human health. Although 90 percent of the total pollutant load of the atmosphere comes from natural sources (volcanoes, sea spray, pollen, dust, fires), the remaining 10 percent (from agricultural, industrial, and urban sources) are emitted where people live, work, and play. Anthropogenic emissions are also the most toxic. Adverse effects of any pollutant can be estimated from the interaction of several factors, including the toxicity of the agent, its concentration, length of exposure, and the biological vigor of the receptor.

Adverse effects = f (toxicity, concentration, exposure time, biological vigor)

personal

Our lungs are our personal link to the atmosphere. It is here that polluted air excercises its most devastating health effects. In a pollution-filled environment, toxicity, concentration, and exposure time are maximized. Those most at risk include infants, the elderly, and those already at risk for lung disease. Mortality and morbidity statistics should remind us of our social responsibility concerning clean air legislation.

People spend the vast majority of their time indoors where pollution levels may be 10 to 40 times higher than outdoors. Asbestos, Radon, carbon monoxide, and secondhand tobacco smoke are just a few of the airborne toxic pollutants that we encounter in high concentrations indoors.

local/urban

The immense amount of particulates, chemicals, and waste heat in highly populated urban areas can cause significant meteorological changes. Temperature inversions can cause stagnant conditions for periods ranging from several hours to several days. Urban heat islands have emerged along with the growth of cities. Polluted air over cities can contain as many as 1 million cloud condensation nuclei and can change precipitation patterns downwind.

The effects of factory and smokestack emissions was noted in England by John Evelyn as early as the 17th century. The term "acid rain" was coined by the British chemist Robert Angus Smith in his book, Air and Rain: The Beginnings of a Chemical Climatology (1872). In the industrial town of Donora, Pennsylvania, 20 deaths and widespread respiratory illness resulted from an air pollution incident in 1948. Four years later, in London, 445 deaths were directly attributed to a five-day acid fog event. Perhaps as many as 4000 more suffered chronic, and eventually fatal illnesses. Los Angeles is notorious for its photochemical smog, a complex chemical soup caused by the interaction of auto emissions and sunlight. Many different chemicals and sources contribute to its formation, but the most widely-known component is ozone (O₃).

regional

Acid deposition is also a regional or trans-boundary pollution issue. Emissions from anthropogenic sources account for about 70 percent of the sulfur and 88 percent of the NO_x in the United States.These chemicals are highly soluble in water, producing sulfuric acid and nitric acid, respectively. They increase the acidity of the rainwater which leads to physical consequences, like the deterioration of buildings, as well as natural consequences. There is some evidence that this contaminated rain has raised the acidity of rivers and lakes killing the less tolerant freshwater fish and invertebrates. It has also increased the acidity of soil in forests, which destroys their plant life. Overall, air pollution causes serious meteorological, biological, and physical consequences.

The following equations explain how NO_x and SO₂ are converted to ions, in the presence of photochemical oxidants that dissolve readily in rain and clouds.

SO₂ + (1/2)O₂ + H₂O ----> 2H⁺ + SO₄ ^2-

NO + NO₂ + O₂ + H₂O ----> 2H⁺ + 2NO₃^-

-occur over hours or days-

This process creates nitric acid (HNO₃) and sulfuric acid (H₂SO₄) which lower the pH of precipitation. Rain is slightly acidic to begin with having a pH of about 5.6 (not neutral 7.0) due to natural amounts of carbon dioxide in the air combining with moisture to form carbonic acid. In some highly affected areas, the pH can be as low as 3.5 which is considered highly acidic and can be dangerous forms of life in the area.
Oxides of sulfur and nitrogen can also reach the ground in dry form, such as a gas or an aerosol. Plants then either absorb them or they combine with surface water and form acid in both cases. This type of deposition occurs relatively close to the pollution source; whereas, the traditional acid rain can fall miles and miles away from the tall stacks which emit the pollutants.
The SO₂ and the NO_x, which give rise to acid deposition, are emitted almost entirely by manmade sources. Although small amounts are emitted naturally by volcanoes or vegetation decay, the vast majority is released from coal burning mills or power plants. In the United States, a majority of these plants are located in the Midwest, but, because the pollution travels far through the atmosphere, the acid deposition occurs in the Northeast. Also, due to atmospheric movement, this problem, in essence, has urban causes with rural effects. Particularly, it destroys crops in farming areas and reduces their yield. Generally, acid rain disrupts entire forest ecosystems by soaking the soil with toxic chemicals that contaminate the ground water, and it disrupts lacustral ecosystems by polluting the lake enough to make it sterile. Most aquatic insects, algae, and plankton cannot tolerate water with a pH below 5.0. These organisms are at the base of the food chain; therefore, their survival effects the survival of all other aquatic organisms. A pH below 5.0 can also result in reproductive failures in fish and amphibians, which results in a disappearance of these creatures from the ecosystem.
Due to the atmospheric transport of pollutants over a wide area, acid rain has become a transboundary, therefore, international problem. For example, chemicals from Eastern Europe are causing a decrease in the pH of lakes in southern Scandinavia. Also, pollutants from major U. S. cities have crossed the border and caused environmental problems in Canada. This issue gained public attention during the mid 1980s, but, at the time, President Ronald Reagan did not take any active steps in improving the situation. He wanted more research to be done of the issue, which culminated in the National Acid Precipitation Assessment Program (NAPAP). Currently, many different programs are monitoring a range of sites throughout the world to assess amounts of acid precipitation and the damage it causes.

global 

Air pollution can (theoretically) contribute to global climate change in a few different ways. Large amounts of carbon dioxide (CO₂) in the atmosphere can lead to global warming due to the greenhouse effect. Specifically, the sun's heat will enter our atmosphere, but it will not be able to escape, creating an atmosphere like that of a greenhouse. A significant rise in temperature will lead to the melting of polar ice caps. This event will then cause a rise in sea level, and the oceans will submerge major coastal cities. Conversely, the impenetrable amount of particulates in the air may block out the sun and its heat causing global cooling. This phenomenon would provoke an ice age that would lower the sea level leaving coastal fisheries and ports stranded.

health effects

The many different chemicals permeating our air are not only irritating, but they can cause an increase in health problems for the entire exposed population. Each chemical is linked to specific health related problems, whether they are instantaneous or detrimental over a long period of time. Specifically, these are the most damaging chemicals and the problems that they cause.

CO	poor reflexes (the CO attaches to the hemoglobin in the bloodstream taking the place of oxygen) ringing in the ears headaches dizziness nausea breathing difficulties drowsiness reduced work capacity comatose state (can lead to death)
Pb	kidney damage reproductive system damage nervous system damage (including brain disfunction, and altered neurophysical behaviors)
NOx	increased risk of viral infections lung irritation (including pulmonary fibrosis and emphysema) higher respiratory illness rates airway resistance some chest tightness eye burning headache
O3	respiratory system damage (lung damage from free radicals) reduced mental capacity damage to cell lining (especially in nasal passages) reduces effectiveness of the immune system (lowers the resistance to infectious diseases) headaches eye irritations chest discomfort breathing difficulties chronic lung diseases (including asthma and emphysema) nausea
SO2	aggravates heart and lung disease increases the risk for respiratory illnesses (including chronic bronchitis, asthma, pulmonary emphysema) cancer (may not show for decades after exposure)
PM10	respiratory illnesses (including chronic bronchitis, increased asthma attacks, pulmonary emphysema) aggravates heart disease