Effects of Air polloution on Animals

Effects of Air polloution

Animals

Direct

Animals are exposed to air pollutants via three pathways: 1) inhalation of gases or small particles, 2) ingestion of particles suspended in food or water, or 3) absorption of gases through the skin. In general, only softbodied invertebrates (e.g. earthworms), or animals with thin, moist skin (e.g. amphibians) are affected by the absorption of pollutants. An individual's response to a pollutant varies greatly and depends on the type of pollutant involved, the duration and time of exposure, and the amount taken up by the animal. Factors such as the individual's age, sex, health, and reproductive condition also play a role in its response. For example, a young animal may be injured by a short episode of extremely high pollutant concentration, while an adult of the same species may have little, if any, response to long-term exposure to the same pollutant at slightly lower concentrations. There is also a great deal of variability between animal classes, species, and even genotypes, in terms of the level of tolerance to a particular pollutant.

In this section, the pollutants of concern have been divided into three broad categories: gases, such as ozone and hydrogen sulfide; non-acidic particulates and toxins, like metals, fluoride compounds, and organic and synthetic chemicals; and acidifying agents, specifically nitrates and sulfates. Each category is discussed in detail below.

Indirect

In addition to affecting individual animals or populations directly, air pollutants also affect wildlife indirectly by causing changes in the ecosystem. Vegetation affords cover for protection from predators and weather, provides breeding and nesting habitat, and also serves as a food source. Therefore, any change in vegetation could indirectly affect animal populations. For example, the northern parula warbler (Parula americana) requires a certain type of lichen for nesting material. These Usnea sp. lichens are extremely sensitive to increased sulfur dioxide levels. It has been shown that as sulfur dioxide levels have increased in the eastern United States, the lichen species have decreased, and along with the lichen decline, parula warbler distribution has been reduced. Without the lichens crucial for nesting material, the warbler is at a reproductive disadvantage when competing with those species that build their nests from other materials.

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Many studies have found that invertebrates show a preference for, or are better able to establish themselves in, air pollution-injured vegetation Results of a fumigation experiment show that monarch butterflies (Danaus plexippus) prefer to feed on ozone-fumigated milkweed versus those plants grown in charcoal-filtered air. The report stated that the butterfly larvae developed faster when feeding on fumigated plants. The cardenolides, toxins in the plants that make monarch butterflies unpalatable to insectivorous birds, showed variable responses to ozone fumigation. However, significant premature senescence of leaves was observed in ozone-treated plants compared to controls. In addition to the possibility that ozone changes the nutritional value of leaves, there is also concern that eggs laid on ozone-injured leaves will not have time to develop if the leaves fall off prematurely. Consequently, the long-term effects of feeding on ozone-injured plants on the growth, reproduction, and population dynamics of monarch butterflies are unknown.

Fluoride and heavy metals can accumulate in the soil to levels that are toxic to soil invertebrates. Programs have shown that biological activity rates and invertebrate community structure and biomass decrease in metal-polluted soils. Species sensitive to metals are replaced by ones that are more metal-tolerant. For example, softbodied species such as earthworms and nematodes seem to be more readily affected by elevated metal concentrations. Invertebrates play an important role in forest floor litter decomposition. In a study near an aluminum reduction plant, litter accumulation near the facility was abnormally high. It was suggested that emissions from the plant were causing fluoride to build up in the soil to levels that were toxic to litter decomposers. As forest floor litter builds up, mineral release is delayed, and the availability of nutrients to plants is reduced. Herbivores are ultimately affected when they are faced with a decrease in the quantity or quality of their food supply.

Although birds and mammals are not directly affected by water acidification, they are indirectly affected by changes in the quantity and quality of their food resources. Piscivorous birds and mammals--such as common loons (Gavia immer), osprey (Pandion haliaetus), and river otters (Lutra canadensis)--encounter a decreased food supply when pH levels fall to a point where fish reproduction ceases. The same is true for waterfowl that feed on invertebrates. One study found that black duck (Anas rubripes) ducklings raised on control wetlands survived better and gained more weight than did ducklings raised on experimentally-acidified wetlands. Blood samples taken from the ducklings revealed that those raised on the acidified wetlands had characteristics consistent with undernutrition. In addition to a decrease in invertebrate availability, there may have been a decline in the nutritional value of the invertebrates that were eaten. In fact, another study found that invertebrates collected from acidic lakes had less caloric content and lower calcium levels than invertebrates collected from circumneutral pH lakes. Although little research has been done on the effects of acidification on species other than waterfowl, population decline has also been documented in dippers (Cinclus cinclus), a passerine species that feeds on stream invertebrates. The study found a 70 to 80 percent decline in dipper populations along one stream, over a 20 year period, that coincided with a drop in stream pH of 1.7 units.

Calcium is an essential element for both mammals and birds. An adequate dietary supply is particularly crucial during reproduction. Birds need calcium for the proper formation of eggshells and for skeletal growth of hatchlings, and mammals need calcium for skeletal development of fetuses in utero. Many invertebrate species that contain high concentrations of calcium, such as mollusks and crustaceans, are very sensitive to pH levels and are among the first to disappear during the acidification of wetlands. A pH of 6.0 seems to be a threshold value for many of these species. In addition, the invertebrates that do remain contain less calcium than those found in non-acidified waters. Therefore, the reproductive success of animals breeding in, and near, acidified wetlands may be negatively affected by decreased calcium availability.

Health

Almost all chemicals find their way into the air. But many are released in such small amounts that they are not a health concern. Some substances are so common and widespread they build up in the air and become a hazard to human health.

Exposure to air pollution can make your eyes water, irritate your nose, mouth and throat, and make you cough and sneeze. But more important, it can also worsen and may cause lung disease like asthma, bronchitis and emphysema. In some cases, it can even contribute to the premature death of people with heart and lung disease.

Six major pollutants of air

1. Carbon Monoxide

Carbon monoxide (CO) is an odorless, colorless, poisonous gas that comes mainly from motor vehicles and other combustion exhaust.

Health effects: Carbon monoxide interferes with the blood's ability to carry oxygen to the brain, heart and other tissues, and it is particularly dangerous for people with existing heart disease, and unborn or newborn children.

2. Ozone

Ozone (O3) is the major harmful ingredient in smog. It is not emitted directly into the air but produced in the atmosphere when gases or vapors of organic chemicals called hydrocarbons combine with nitrogen oxide compounds in the presence of sunlight.

Organic hydrocarbon gases, one of the raw ingredients of ozone, are released from a variety of sources related to human activities. Major sources include refineries, gas stations, motor vehicles, chemical plants, paints and solvents.

Harmful ozone in the lower atmosphere should not be confused with ozone in the upper atmosphere, which protects us from ultraviolet radiation.

Health effects: Ozone reacts with lung tissue. It can inflame and cause harmful changes in breathing passages, decrease the lungs' working ability and cause both coughing and chest pains.

Ozone air pollution, found at unhealthful levels in nearly all of the nation's major urban areas, may particularly affect millions of otherwise healthy Americans who, for currently unknown reasons, are especially sensitive to it.

People who exercise are also more vulnerable to the effects of ozone, suffering symptoms and a reduced ability to breathe at relatively low ozone levels. Ozone pollution, even at low levels, has also been linked to increased hospital admissions and emergency room visits for respiratory problems.

3. Nitrogen Dioxide

Nitrogen dioxide (NO2) and related nitrogen oxides (NOx) are produced when fuel is burned, especially in power plants and motor vehicles. These oxides of nitrogen compounds contribute to ozone formation, and are a health problem themselves. NO2 also changes in the atmosphere to form acidic particles and liquid nitric acid.

Health effects: Both NO2 and NOx may threaten human health. Nitrogen dioxide seems to act on the body like both ozone and sulfur dioxide.

4. Sulfur Dioxide

Sulfur dioxide (SO2) is created when sulfur-containing fuel is burned, primarily in powerplants and diesel engines. Like NO2, sulfur dioxide can also change in the atmosphere into acidic particles and into sulfuric acid.

Health effects: Sulfur dioxide constricts air passages, making it a problem for people with asthma and for young children whose small lungs need to work harder than adult lungs. Even brief exposure to relatively low levels of sulfur dioxide can cause an asthma attack.

5. Particulate Matter

Particulate matter (PM) includes microscopic particles and tiny droplets of liquid. These particles come from the burning of fuels by industry and diesel vehicles and from earth-moving activities such as construction and mining.

Health effects: Larger particles can be stopped in the nose and upper lungs by the body's natural defenses. The smallest particles escape the body's defenses and go deep into the lungs, where they may become trapped.

Exposure to particulate pollution can cause wheezing and other symptoms in people with asthma or sensitive airways. Particulate pollution has been linked to increased hospital admissions and emergency room visits for respiratory problems and to a substantial increase in premature deaths.

6. Lead
Lead (Pb) has been known as a poisonous substance for many years. Due to past major reductions and now the elimination of lead in gasoline, there has been a significant decrease in public exposure to lead in outdoor air.

Remaining air pollution sources include lead smelters, incineration of lead batteries, and burning lead-contaminated waste oil. However, the most common sources of current lead exposure are indoors from old lead-containing paint and soil.

Health effects: Exposure to high levels of lead can damage the blood, brain, nerves, kidneys, reproductive organs and the immune system. Lower levels that are more commonly associated with current exposures can result in impaired mental functioning and development in children and raising blood pressure in middle-aged men.

Lead accumulates in the body, so repeated small doses can be harmful.