INTRODUCTION TO ENVIRONMENTAL SCIENCES

LECTURE NOTES

Outdoor and Indoor Air Pollution

Almost all living organisms rely on the gases found in the earth's atmosphere, even those dwelling in the deepest oceans. Therefore, pollution of the atmosphere has profound and far-reaching global impacts.

I) Atmospheric Structure and Processes

The atmosphere is not a homogeneous mass of air. Rather, it is divided into distinct layers with unique temperature distributions.

A) Troposphere: (0-17 km or 0-11 mi at the equator; 8 km or 5 mi at poles)

Makes up 75% of the Earth's atmosphere. This is the layer where weather occurs and is very turbulent. Comprised of 78% Nitrogen, 21% Oxygen, <1% Argon, 0.036% CO₂, plus traces of other gases, including water vapor. Typically, temperatures decline with altitude down to ≠50 C at the tropopause (top of troposphere).

B) Stratosphere: (17-48 km or 11-30 miles)

This is a layer of low turbulence with little mixing. However, high-speed winds (jet streams) are common. Temperatures rise until the stratopause is reached. It has the same composition as troposphere except 1,000X less water vapor and 1,000 times more ozone (O₃)

Stratospheric ozone is constantly being created by oxygen interacting with lightning and UV rays. It blocks 99% of the incoming UV from the sun. This allows life to exist on the surface and keeps us from constant sunburn, cataracts, skin cancers, and immune system damage. Also helps keeps tropospheric oxygen from being converted to ozone, which is a pollutant in the lower atmosphere.

In summary, tropospheric ozone is bad, stratospheric ozone is good. Unfortunately, we've increased the former and decreased the latter over the last 50 years.

Higher up are the mesosphere (30-50 miles) and thermosphere (50+ miles), both of which have little or no interaction with surface.

C) Human Disruption of Gaseous Nutrient Cycles.

We have increased CO₂ in troposphere by about 30% in last century, mostly by burning fossil fuels and destroying forests. We have decreased stratospheric ozone by 5-15% due to the use of chlorofluorocarbons and other ozone destroying gases.

We are emitting three times as much NO, NO₂, N₂O, and ammonia (NH₃) by burning of fossil fuels and use of fertilizers. These turn into nitric acid and help form acid deposition. The same is true for emission of SO₂.

Also spewing huge amounts (above natural levels) of toxic metals into the troposphere, including, arsenic (2X), cadmium (7X), and lead (17X).

II) Outdoor Air Pollution: Pollutants, Smog, and Acid Deposition

A) Pollutant Types

Primary Pollutants: Additions to the troposphere by natural processes (dust, volcanic emissions) and human activities. If they occur in high enough concentrations to cause harm to plants, animals, or materials they are considered pollutants. Mixed throughout the troposphere by turbulence.

Secondary Pollutants: Primary pollutants react to form new compounds in the atmosphere.

Pollutants sources can either be stationary (i.e. factory) or mobile (i.e. car). Urban areas usually have higher levels of air pollution than rural areas, although winds can spread long-lived pollutants over great distances.

Pollutants come in various forms and can be solids, liquids, or gases.

B) Smog

Two types: photochemical (brown-air) smog and industrial (gray-air) smog.

Photochemical smog forms by pollutants that are produced by reaction with light. It is dominantly secondary pollutants, and is most common in urban areas where sunlight is abundant (i.e. Los Angeles, Denver, Salt Lake, Sydney, Mexico City, and Sao Paulo). Highest levels typically during the afternoon.

Industrial smog forms largely from primary pollutants like SO₂ or SPM. Less of a problem today in the U.S. due to recent pollution control legislation. Still a problem in Eastern Europe, China, and India because of the burning of high-sulfur coal and oil.

Urban basins surrounded by mountains restrict wind flow and promote temperature inversions where dense cool air is trapped beneath a layer of less dense warm air. This keeps surface air stagnant and not capable of mixing with cleaner high-altitude air. Causes smog events that last for days and affect the health of thousands.

C) Acid Deposition

Caused by sulfur and nitrogen oxides in the troposphere forming acid and acid-forming salts, which are then dispersed great distances by the wind. They fall to earth as liquids (acid rain, snow, sleet, fog) or solids. Tall smokestacks promote this, although they reduce local pollution. What goes up in Illinois comes down in Vermont! Can also cross national boundaries.

Acid deposition lowers the pH of streams, lakes, and groundwater. Normal surface waters have pH of around 5.5 (slightly acidic), whereas waters affected by acid deposition can get as low as 2.5 (1,000 times more acidic).

If the soil is basic it can offset (buffer) the effects of acid deposition. If the soil is thin or acidic it cannot buffer adequately.

Can cause asthma and bronchitis and damages buildings, statues, cars, and metals.

Most profound effects are to aquatic life and trees. Weakens trees so they become susceptible to other types of damage. Most damage occurs in mountainous areas with thin soils. Also increases leaching of soil nutrients making them less fertile.

Fish and other aquatic life cannot survive in waters with a pH of less than 4.5. Many lakes are now devoid of life. Also releases toxic chemicals into the water.

The cost of reducing acid deposition in the U.S. is calculated to about 1/2 the expected economic benefit. Situation is now improving somewhat due to recent air pollution control legislation. However, we can further reduce acid deposition by: 1) reducing energy consumption; 2) switching to low-sulfur fuels; and 3) improving pollution controls. Can also add lime to lakes and soils, although this is a stopgap measure and may do more harm than good.

III) Indoor Air Pollution

It is often more polluted (2-70 times depending on pollutant) and unhealthy than outdoor air. Many buildings (15-20%) have "sick building syndrome" where at least 20% of the occupants have flu-like (and other) symptoms that cease when they go outside. May cause $100+ billion in lost productivity.

Most common pollutants include mineral fibers, cigarette smoke, formaldehyde, radon, and other chemicals. In developing countries, high levels of particulates from open fires are the largest problem.

A) Asbestos

Includes a wide variety of minerals with fibrous or thread-like form. When breathed into the lungs for long periods of time (years) may cause asbestosis, lung cancer, or mesothelioma. May be responsible for 300,000 premature deaths.

Health impacts seen most commonly in asbestos miners and workers who have had chronic, high level exposures. It is not clear whether there is a risk at much lower exposures experienced by most people. Also, there is a greater risk with amphibole asbestos, and a lesser risk with the more common chrysotile form.

Billions have been spent on removing asbestos from buildings, particularly schools, with no clear knowledge that the expenditure is necessary. Removal process may actually increase exposure so encapsulation strategies are often preferred.

Now recommend not removing or disturbing undamaged or intact asbestos. Seal if necessary and remove only as a last resort.

B) Radon

Radon is a natural, gaseous decay product of uranium. Found in all soil gases and well water. Also found at low levels in the atmosphere. Enters the home through cracks and openings in the basement. Can build up to levels many times (10x-1,000x) that found in the atmosphere.

Breathing radon gas or the solid radioactive decay products of radon can bathe your lungs in ionizing radiation. Can cause lung cancer after chronic, high-level exposures.

May be responsible for as many as 15,000 deaths each year in the U.S. Mortalities can reach 50% at very high radon levels (200+ pci/l).

There may be a threshold level below about 20 pci/l where radon exposures are not significantly harmful. Less than 1% of U.S. homes have that level or higher. In some parts of New Jersey almost 10% of the homes have that level.

Need to measure each home individually. Cannot predict which specific homes will have high or low levels. Fortunately, even homes with the highest levels can be remediated for relatively low cost ($1,000-$5,000).

Federal standard is now 4 pci/l. This value is selected because it is a relatively safe level (about 3% mortality from a lifetime exposure) that is cheap and easy to attain.

IV: Air Pollution Effects

A) Human Health Impacts

Biggest impact of pollution on humans is to their respiratory system. Chronic exposures can cause lung cancer, asthma, bronchitis, and emphysema. Elderly, the very young, and pregnant women are the most vulnerable. Caused by a variety of gases (ozone, SO2, NxO) and suspended particulate matter (SPM), 100 microns or smaller in size (soot).

High levels of CO (largely from incomplete combustion) can interfere with blood oxygenation, causing loss of mental function, nausea, drowsiness, and eventual asphyxiation. Can also cause heart and respiratory problems, and affect fetal and infant development.

Volatile organic compounds (VOC; benzene, formaldehyde) and toxic metals and compounds (lead, arsenic, PCBs, dioxin) can cause genetic mutations, reproductive problems, and cancers.

Every year, as many as 50,000-200,000 people may die prematurely in the U.S. from the effects of outdoor air pollution. Another 100,000-150,000 may die prematurely every year from the effects of indoor air pollution. Total world premature deaths may approach 1 million+ per year.

Air pollution may also cause as much as $150 billion in economic losses due to worker illness and lost work time.

B) Plant Damage

Chronic exposure to air pollution destroys the waxy coatings on leaves and allow plants to become susceptible to water loss, pests, diseases, drought, and frost. May also interfere with nutrient uptake.

Trees at high altitude often are more affected because of year-round exposure to pollutants carried by high-level winds. Loss of vegetation may then lead to increased soil erosion, flooding, and mass wasting.

Areas around smelters and coal-burning power and industrial plants often subject to large plant die offs. In Europe, approximately 25% of the trees have been damaged or killed by air pollution, with a total economic loss reaching $30+ billion.

In the U.S. the most susceptible region to air pollution damage is in the northeast Appalachian Mountains. Agricultural losses may be as high as $5 billion per year.

C) Damage to Aquatic Life and Man-Made Materials

Most damage caused by acid deposition, typically after a heavy rain or during the spring snow melt. Leached aluminum ions kill fish and inhibit their reproduction.

Loss of net primary productivity affects animals farther up the food chain. Thousands of lakes in Scandinavia (16,000+), Canada (14,000+), and the U.S. (9,000+) no longer can support meaningful fish populations or are at risk.

Billions of dollars in damage is done each year to all kinds of materials we make. Everything from the erosion of building stone, destruction of car finishes, soiling of clothes, and the degradation of painted surfaces. $5 billion in building damage may be due to acid deposition each year in the U.S. alone.

V. Ways of Reducing and Preventing Air Pollution

A) Clean Air Acts

The biggest reductions in air pollution in the U.S. in the last 40 years are the result of the federal Clean Air Act of 1963, 1970, 1977, and 1990. There are some concerns the Clean Skies Act of 2002 has weakened some of the standards.

Clean Air Act established national ambient air quality standards for seven major outdoor pollutants (SPM, SOx, CO, NxO, ozone, VOC, and Pb).

Has resulted in a 30% reduction in overall air pollution since 1970. Lead has decreased 98%, ozone 50+%, CO 36%, and SO2 37%. Others have decreased less significantly or even increased (NxO and SPM). Economic value of the benefits of the cleaner air estimated to be 6-33 times the cost.

B) Can We Do Better?

Yes!! It is estimated that we could reduce deaths in the U.S. by approximately 6,000 per year just by strictly enforcing already existing standards.

We can do better by preventing rather cleaning up pollution, increasing automotive fuel efficiency standards, imposing stricter standards for fine particulates, stop grandfathering or delaying standards on older power plants, improving standards for municipal trash incinerators, and imposing stricter standards on greenhouse gases.

Also need to evaluate the effect of emissions trading where companies can buy or sell the right to pollute. Some people think this strategy works, others think it keeps emissions unnecessarily high.

There are a number of other specific ways to reduce outdoor air pollution from static and mobile sources, and also reduce indoor air pollution. Some strategies target prevention; others target dilution or cleanup (reduction of already existing pollution).