Joe Paniagua's Midterm #2 Essay Answers

26. Explain how lead (Pb++) inhibits the oxygen-carrying capacity of the blood.

Lead (Pb++) is generally absorbed by the body through inhalation or ingestion into the lungs or the gut. It then can enter the bloodstream and attach to red blood cells. Approximately 97% of the lead is taken up by these cells. Once in the cells the lead disrupts the body’s production of hemoglobin (heme biosynthesis) which is responsible for carrying necessary oxygen to all tissues in the body. The lead actually binds to enzymes (ALAS , ALAD and ferrocheltase) in the cell mitochondria altering their ability to catalyze chemical reactions that help produce oxygen through respiration. The heme molecule is the oxygen carrying part found in red blood cells. This process can also result in red blood cells dying sooner than what would be normal and a lessened ability to create new red blood cells. Lead also interferes with the uptake of Iron (Fe++) necessary for the production of more healthy red blood cells by taking the place of iron in the mitochondria. Iron poor blood can lead to anemia, a physical condition marked by fatigue. Anemia, in turn, can lead to more susceptibility to lead poisoning. This condition is usually more serious for children than adults since their smaller bodies can absorb greater amounts of lead through the gut because of higher metabolism and thinner cell walls.

27. Compare the environmental toxicity of substances that result from burning coal as opposed to those from burning petroleum products, such as oil and gas.

Burning coal or petroleum produces many of the same toxic substances that can be harmful to the environment. But they also produce some toxic substances that are more specific to either coal or petroleum. Some of the common substances produced by both types of fuel are sulfur dioxide, nitrogen oxide, ozone gas, carbon dioxide and hydrocarbons. In general, these substances can be considered air pollution because they readily disperse through the atmosphere which can lead to health and environmental problems. In humans, chemicals in polluted air can lead to cancer, birth defects, brain and nerve damage, and long term injury to the lungs causing breathing problems. This effect on the environment is referred to as “acid rain”, whereby toxic chemicals in the air are transported through the atmosphere and then fall back to the earth through rain or snow. Trees, lakes, fish, birds and animals can also suffer in many ways. The release of heavy metals, and the addition of sulfuric and nitric acids that create a pH imbalance in the water and soil because of increased acidity, can damage plants, animals and even buildings. Toxic substances more specifically related to the burning of petroleum are carbon monoxide (a gas) and lead ( a heavy metal that has been mostly phased out as an agent in gasoline). Both of these toxins can be extremely hazardous to human health, even fatal, when they enter the bloodstream and deprive the body of needed oxygen. Burning coal, on the other hand, produces an extraordinary amount of sulfur dioxide and particulate matter; that is, solid, microscopic particles in smoke, ash, dust and vapors that can be breathed into lung tissue causing respiratory diseases like chronic bronchitis and permanent lung damage. The burning of wood or diesel fuels can also contribute to particulate matter pollution, but the amount of coal burned in the world is the greatest contributor to this type of toxic substance.

28. What are the ecological consequences of acid rain? What types of toxicity are associated with acid deposition in terrestrial and aquatic environments?

The primary consequence of acid rain in the environment is an upset in the balance of the native ecosystem. Sulfur and nitrogen acids deposited into the soil and water can lower the pH (increase the acidity) which can have additional consequences on biological organisms. In soils the “buffering capacity”, that is, the ability of chemicals in the soil to maintain a normal pH balance, is overwhelmed by the tremendous increase in acid pollutants. This increased acidity from acid rain can then leach out or dissolve metals such as aluminum or cadmium inherent in the soil that could possibly be taken up by plants and trees causing them damage or death. The soil could also lose essential nutrients for plant life in this leaching process. The leached out metals could then enter water systems like lakes, rivers and streams posing serious harm to aquatic life. Not only will plant life in the water be affected by higher levels of acidity, but the metals leached into the water can be taken up by fish, or even animals causing toxicity. Cadmium can cause kidney damage to mammals, and aluminum can attach to fish gills which can kill them. Indeed, in areas with susceptible or weak buffering soils as in Scandinavia, lakes have become sterile, or devoid of fish or plant life.

29. What are some of the direct consequences of acid rain to biological organisms? How does acid rain affect reproduction and embryonic development?

Acid rain can affect plant life directly through external contact. Leaves exposed to the highly acidic chemical deposits carried by rain and snow can be damaged rendering trees toward poor health. Even dry acid dust can be deposed onto plant life. Seepage into the soil can also cause damage to roots by direct contact, and a change in the chemical nutrients from reactions to high levels of acidity can cause tree die-back or death. The direct contact of acid rain pollutants in water systems can greatly affect the pH levels which will in turn potentially harm fish life. High concentrations of toxic compounds can perhaps kill off a species, which may in turn be replaced by a more tolerant species, thus altering the ecosystem. This could have consequences for all other life in the area. Even low levels of toxins can lead to the decline in fish populations by damaging fish eggs and upsetting their reproductive cycle. The poisoning of the food chain by toxic deposits or chemical alterations can also occur. In this instance, toxins absorbed or ingested can cause bioaccumulation in the fatty tissues of plants and animals, then pass up the food chain to other mammals, including humans. Both lead and mercury can enter water systems through acid rain and can be absorbed by fish, which feed off plants and smaller fish life in their environment. Mammals which then eat the contaminated fish will absorb concentrated amounts of these toxins which can have acute, chronic or teratogenic(affecting the embryo) outcomes.

30. Accurately describe three procedures that were demonstrated to us at the Brelje and Race Environmental labs.

Three tests conducted for water quality at the Brelje and Race Labs involved checking for bacteria, for toxic heavy metals, and for total solid particulate matter: