Pollution
Chemical Pollutants
The air has never been pure. Sometimes it contains substances that are undesirable or even harmful.
These substances might be from natural events such as volcanoes or forest fires or they might be from human activity.
A pollutant is something present in an amount that is undesirable or harmful.
Three basic processes cause pollution:
1. Attrition
a. The wearing of grinding of a substance by friction.
b. This includes sanding, drilling, erosion, and the breaking of a liquid into small droplets.
c. The process produces small particles called particulates.
2. Vaporization
a. The changing of a substance from a liquid to a gas.
b. This process allows us to smell things.
3. Combustion
a. This is a chemical reaction in which a substance combines with oxygen and releases light and heat. Basically, burning.
b. Burning gas in the internal combustion engine is a major source of air pollution.
c. If the combustion of gas is complete, the only waste products are carbon dioxide and water. For this to happen, three conditions must be met:
i. The fuel must be a pure hydrocarbon (gasoline, oil, coal, alcohol, etc.). These fuels usually contain impurities that become pollutants when the fuel is burned.
ii. The fuel must be mixed with the right amount of oxygen.
iii. The fuel must be burned at the correct temperature.
d. Usually, one of these conditions is not met and pollution results.
Nature also causes pollution and volcanos are likely the single greatest source. When they erupt, volcanos release dust, sulfur dioxide, carbon dioxide, and other pollutants.
Urban pollution is most often caused by burning fossil fuels in cars, power plants, and industry.
Chemical pollutants can be organized into several categories:
1. Volatile Organic Compounds
a. Organic means that a chemical contains carbon.
b. Volatile means they vaporize at low temperatures.
c. Sources include
i. refineries
ii. chemical manufacturing plants
iii. dry cleaning
iv. gas combustion in motor vehicles
v. paints and cleaners
vi. basically anytime you use a product and get a “chemical” smell
2. Nitrogen Oxides (NO2, NO3)
a. These are produced when fossil fuels (coal, oil, natural gas, gasoline) are incompletely burned.
b. NO2 is a brownish-red gas that is an ingredient in smog.
i. One of the most important pollutants in smog is ozone.
ii. At ground level, ozone is quite harmful.
c. Sources include:
i. burning fossil fuels at power plants
ii. burning fossil fuels in cars and trucks
iii. natural sources such as lighting, bacteria, and volcanoes
d. Nitrogen oxides in the atmosphere dissolve in rain to produce acid rain.
3. Carbon Oxides (CO and CO2)
a. When fossil fuels are burned carbon monoxide and carbon dioxide are released.
b. Carbon dioxide can be deadly if it is in high concentrations.
c. Carbon monoxide is deadly even in low concentrations.
d. Sources include:
i. burning fossil fuels
ii. forest fires
e. Remember that carbon dioxide is a major contributor to global warming.
4. Suspended particulates
a. These are very small solid particles or liquid droplets that are small enough to stay in the air for long periods of time.
b. They are harmful when we breathe them into our lungs and can cause respiratory illness and lung cancer.
c. Solid and liquid particulates have different sources.
i. Solids (called dust)
(1) sea salt
(2) pollen
(3) volcanic ash
(4) dust from wind, erosion, fires, mining, or construction
(5) burning of fuel releases soot
ii. Liquids (called aerosols)
(1) diesel exhaust
(2) spraying chemicals on farms or elsewhere
(3) industry
5. Sulfur Oxide (SO2)
a. Sulfur (S) is naturally found in coal and oil.
b. When those fuels are burned the sulfur is released to the atmosphere in the form of SO2.
c. Most SO2 comes from the burning of fossil fuels and from industry.
d. When SO2 combines with water in the atmosphere it forms sulfuric acid.
e. This is one of the main causes of acid rain.
6. Sick Building Syndrome
a. Most North Americans spend 90% of their time indoors.
b. In order to conserve energy, many homes are sealed so that they are much more airtight.
c. With little air circulation, pollutants are trapped inside and we breathe them constantly.
d. Symptoms of sick building syndrome include dizziness, nausea, burning eyes, headaches, breathing difficulty, drowsiness.
e. Sources of pollutants include:
i. construction materials
ii. furniture
iii. paint
iv. cleaners
v. cigarette smoke
vi. beauty products
vii. heating with oil, natural gas, or wood
viii. carpets
ix. cooking
Effects of Air Pollutants
It is difficult to study the effects of pollution on humans because there are so many variables involved.
Science has, however, demonstrated a clear link between air pollution and increased death rate from certain diseases.
1. More deaths from respiratory disease are found in areas with higher air pollution.
2. Higher number of people with common colds where air pollution is higher.
3. People have poor respiratory function in areas of high air pollution.
4. When air pollution is high, there are more hospital admissions for allergies, breathing difficulty, and heart disease.
5. Long term exposure to air pollution is known to damage lung tissue.
6. Cigarette smoke contains several chemicals that are known to cause cancer in lab animals.
Diseases Associated with Air Pollution
It is estimated that air pollution costs $130 B in annual health care costs and 130,000 deaths per year in North America.
The situation is made worse by the amount of time we spend indoors and the chemicals in our environment.
1. Chronic Bronchitis
a. The cells lining the respiratory tract produce mucus to trap bacteria and small particles in the air.
b. Tiny hair-like structures called cilia sweep out the mucus.
c. Pollution can damage the cilia so they can’t sweep mucus out.
d. Also the bronchial tubes produce more and thicker mucus which interferes with gas exchange.
e. Symptoms include shortness of breath and a chronic cough.
2. Bronchial Asthma
a. This is an allergic reaction in the bronchial tubes which causes them to swell and narrow the air passage.
b. In some cases, extra mucus is produced.
c. Sometimes, the tubes go into spasms, causing an asthma attack.
d. The symptoms include shortness of breath and frequent asthma attacks.
3. Emphysema
a. The lungs are filled with tiny air sacs that are needed for gas exchange.
b. After years of irritation, the sacs become stiff and can no longer move air in and out the lungs.
c. The symptoms include shortness of breath and breathing difficulty.
4. Pneumonia and other infections
a. When excess mucus is produced, bacteria become trapped in it and the cilia are unable to move it out of the lungs.
b. This leads to bacterial infections.
5. Lung Cancer
a. Cancer is the disease that results when normal cell division gets out of control.
b. Inhaled smoke and other pollutants cause cells in the lungs and respiratory tract to become cancerous.
c. The cells grow at an unusually fast rate and damage other cells.
d. Some can break away and develop tumors elsewhere in the body.
Pollutants
1. Carcinogens
a. Chemicals or other agents that cause cancer. Examples include asbestos, benzene, arsenic, vinyl chloride, radiation.
b. Some require long term exposure to be cancer causing.
c. Tobacco smoke causes over 1,000 deaths per year in non-smokers in Canada.
2. Respiratory Irritants
a. Small chemicals that irritate the lining of the lungs, including sulfates, nitrates, ozone, cigarette smoke, other smoke, dust.
b. This irritation can cause bronchitis, pneumonia and other infections, and asthma.
3. Particulates
a. These very small airborne particles can get deep into the lung tissue and irritate it.
b. They are small enough to not be trapped by mucus and removed by the cilia.
c. Particulates cause an estimated 16,000 deaths per year in Canada.
4. Carbon monoxide (CO)
a. This gas is created during the combustion of fossil fuels.
b. It is absorbed by the blood and combines with hemoglobin in the red blood cells. This stops hemoglobin from carrying oxygen to all cells of the body.
c. Low concentrations cause fatigue, dizziness, and impaired judgment. Higher concentrations are fatal.
5. Mercury
a. Mercury is absorbed by the body and builds up to concentrations that are toxic.
b. It is present in water ecosystems because of leaching and use by humans. Humans are usually exposed from eating contaminated fish and seafood.
c. It becomes toxic by interfering with the nervous system and kidneys and leads to insanity, nervous disorders, and kidney failure.
6. Lead
a. Lead is another heavy metal that interferes with the nervous system.
b. It is very dangerous for small children and pregnant women because it interferes with normal development.
c. The source used to be leaded gasoline and paint until these were both banned.
d. Lead exposure causes brain damage, mental retardation, and kidney disorders.
7. Arsenic
a. Arsenic and many of its compounds are strong poisons.
b. It prevents cells from producing energy, which leads to their death.
c. There have also been links made between arsenic and cancer.
d. Most arsenic poisoning is from exposure to arsenic trioxide and exposure is usually from groundwater.
e. Symptoms include violent stomach pains, excessive saliva production, vomiting, diarrhea, convulsions and cramps, and death.
pH and Acid Rain
1. Measuring pH
a. The acidity of a substance is measured on th pH scale.
b. Water molecules (H2O) can sometimes break apart into H+ and OH-. Not many are found in water because they usually join back together to make water.
c. An ion is a charged atom or group of atoms. H+ is called a hydrogen ion while OH- is called a hydroxyl ion.
d. Any substance which donates H+ is an acid. Adding H+ makes a solution acidic.
e. Any substance which donates OH- is a base. Adding OH- makes a solution basic.
f. The pH scale for measuring acidity goes from 1 to 14. The middle of the scale is 7; a solution with a pH of 7 is neutral. A pH less than 7 is called acidic and a pH greater than 7 is called basic. 1 is VERY acidic and 14 is VERY basic (the opposite of acidic)
g. Moving from one number to the next on the scale means a 10x difference in acidity. A pH of 5 is 10x more acidic than a pH of 6. A pH of 10 is 100x more basic than a pH of 8. A pH of 2 is 1000x more acidic than a pH of 5.
h. Very few organisms can survive only in a pH between 3 and 8.5. For example, human blood must remain between a pH of 7.35 and 7.45. A blood pH of above 7.8 or below 7.0 is lethal.
2. Acid Rain
a. Even without pollutants, rain would be naturally acidic because carbon dioxide in the atmosphere dissolves to form carbonic acid.
b. Rainfall normally has a pH of 5-5.6 but can be much lower because of air pollutants.
c. SO2, NO2, and NO3 all form strong acids when they dissolve in water vapor, making acid rain.
d. Any source of these chemicals can be a cause of acid rain.
e. Why is acid rain a problem?
i. Low pH kills some organisms.
ii. Fish eggs don’t hatch.
iii. Bacteria are harmed or killed.
iv. Some plants are harmed so the rest of the food chain is affected also.
v. It takes many years for the acid to be removed naturally
vi. Leaching
(1) The acid dissolves minerals and metals in rocks and they get into the water
(2) The metals include copper, lead, zinc, nickel, mercury, and aluminum.
(3) These are often toxic and can harm fish, snails, and aquatic plants.
(4) Humans are affected when we eat contaminated foods.
(5) Acid rain also damages buildings, statues, bridges by eroding stone and corroding metal.
3. Buffers
a. A buffer is chemical that resists a change in pH.
b. Soft rock (like limestone) will dissolve easily to make hard water and the minerals in the hard water help the water resist a change in pH.
c. Areas which contain hard rock (like granite) will not dissolve easily and will make soft water. Soft water does not contain many minerals and is susceptible to changes in pH.
Radiation
1. General information.
a. All matter is made up of atoms.
b. The nucleus (center) of an atom contains protons and neutrons that are held together by a large amount of energy. The nucleus is surrounded by particles called electrons.
c. The nucleus is sometimes not stable and can break apart in a process called radioactive decay.
d. The energy and/or particles released is called radiation
e. This can happen naturally and spontaneously
f. Human applications include nuclear power, X-rays, and nuclear weapons
2. There are three main types of radiation.
a. Alpha radiation
i. This consists of 2 protons and 2 neutrons.
ii. It is very weak radiation that can be stopped by a sheet of paper.
b. Beta radiation
i. Consists of electrons.
ii. Electrons are smaller and move much faster so have more energy.
iii. They require several inches of shielding to stop them.
c. Gamma radiation
i. These are waves of energy that move at the speed of light.
ii. It requires several feet of shielding to block these.
3. Radiation comes from both natural and human-made sources.
a. Natural
i. Some natural elements unstable and so are radioactive.
ii. This radiation is usually at a very low level and is called background radiation.
iii. For example, concrete and brick contain uranium which decays to form radon gas which can accumulate in basements. The radon is itself unstable and gives off radiation.
iv. Coal contains radioactive elements that are released when it is burned.
v. More radiation is released from a coal-fired power plant than from a nuclear plant
vi. Even people are radioactive - everyone contains radioactive elements as part of their body.
b. Human-made
i. Nuclear weapons testing and nuclear power plants.
ii. X-rays and radiation therapy used in medical applications make up the biggest source of exposure for most people.
iii. Airport x-ray systems.
iv. Smoking.
v. TV and luminous watches.
vi. Building materials.
vii. Smoke detectors.
4. Biological effects of radiation.
a. Radiation can enter your body by eating, breathing or simply being exposed to it.
b. The energy of radiation can change the cell so that it does not function properly. It also damages DNA.
c. Cells usually repair themselves but high doses or prolonged low exposure can be dangerous because cells can’t repair all the damage.
d. Exposure is measured in millirem (mrem)
e. The effects of exposure depend on the amount of radiation you are exposed to.
i. 1,000 mrem - no measurable effects.
ii. 10,000 mrem - no evidence that humans are harmed below this level. Birth defects may occur if exposed during pregnancy.
iii. >50,000 mrem is considered carcinogenic.
iv. 100,000 mrem - lower white blood cell count. Increased chance of leukemia and shorter life expectancy.
v. 350,000 mrem - half of people exposed to this amount die within 60 days. Survivors experience nausea, vomiting, diarrhea, reddening of skin, hair loss, blisters, low white blood cell count, bone marrow damage, decreased immune system.
vi. 1,000,000 mrem - immediate nausea, vomiting, and diarrhea. Death follows withing one or two weeks from blistering of the small intestine.
vii. 10,000,000 mrem - person becomes comatose and dies within 1-2 days from damage to central nervous system.