Environmental Hazards, Pollution, and Climate Change: Key Concepts and Policies

Risk

The possibility of suffering harm from a hazard that can cause injury, disease, economic loss, or environmental damage; expressed in terms of probability.

Risk Analysis

Involves identifying hazards, evaluating risks, ranking risks, determining reduction options, and communicating risks.

Major Types of Hazards

Cultural (poor diet, drugs), Chemical (harmful chemicals), Physical (fire, weather, radiation), and Biological (pathogens, allergens).

Toxic Chemical

A chemical that can cause temporary or permanent harm or death.

Carcinogen

A chemical hazard that promotes the growth of malignant tumors.

Mutagen

A chemical hazard that causes random mutations in DNA.

Bioaccumulation

An increase in the concentration of a chemical (e.g., heavy metals, POPs) in specific organs or tissues of an organism over time.

Biomagnification

An increase in concentration of chemicals in organisms at successively higher trophic levels of a food chain or food web.

Persistent Organic Pollutants (POPs)

Synthetic, carbon-based molecules (like DDT and PCBs) that do not easily break down and are fat-soluble, leading to bioaccumulation and biomagnification.

Median Lethal Dose (LD50)

The amount of a chemical received in one dose that kills exactly 50% of the subjects in a test population.

Poison

A chemical that has an LD50 of 50 mg or less per kilogram of body weight.

Nontransmissible Disease

Diseases that are not caused by living organisms and do not spread from one person to another (e.g., diabetes, bronchitis, mesothelioma).

Transmissible Disease

Diseases caused by living organisms (pathogens) that can be spread from one person to another (e.g., tuberculosis, HIV, malaria).

Epidemiological Transition

As a country industrializes, chronic diseases overtake childhood infectious diseases as the primary cause of mortality.

Mesothelioma

A type of cancer caused mainly by exposure to asbestos.

Atmosphere

The thin layer of gases surrounding the Earth, composed of 78% nitrogen, 21% oxygen, 0.9% argon, and 0.1% trace gases.

Troposphere

The lowest layer of the atmosphere (up to 10 km); contains 75-80% of gases and is where most weather occurs.

Stratosphere

The layer extending from 10 km to about 50 km; contains the ozone layer.

Mesosphere

The layer extending from 50 km to about 80 km; the coldest layer.

Thermosphere

The layer extending from 80 km into outer space; includes the ionosphere.

Air Pollution

The presence of one or more chemicals in the atmosphere in quantities and duration that cause harm to humans, other forms of life, and materials.

Primary Pollutant

Products of natural events and human activities that are released directly into the atmosphere.

Secondary Pollutant

New pollutants formed when primary pollutants react with one another or with the basic components of air.

Major Air Pollutants

Carbon Oxides (CO,CO2), Sulfur Oxides (SO2,SO3), Nitrogen Oxides (NO,N2O), VOCs, Particulates, and Photochemical Oxidants (O3,H2O2).

Photochemical Smog

Formed when NOx and VOCs react with heat and sunlight to produce pollutants, including ozone; common in urban areas.

Industrial Smog

Consists mostly of sulfur dioxide formed from the burning of coal and heavy oil.

Nitrogen Oxides (NOx)

Pollutants released by the combustion of fossil fuels; leads to ozone production, photochemical smog, and acid rain.

Volatile Organic Compounds (VOCs)

Compounds that evaporate or sublimate at room temperature, such as formaldehyde and gasoline; both human-made and natural sources exist.

Ozone (O3) (Tropospheric)

A photochemical oxidant and air pollutant that causes respiratory problems; concentrations peak in the afternoon.

Thermal Inversion

An alteration of the normal temperature gradient where a layer of warm air traps cooler, polluted air near the ground.

Catalytic Converter

An air pollution control device in automobiles that converts CO, NOx, and hydrocarbons into less harmful gases.

Wet & Dry Scrubbers

Air pollution control devices used in smokestacks to remove Sulfur Dioxide (SO2) and/or particulates from industrial exhaust.

Electrostatic Precipitator

An air pollution control device that removes particulates from industrial exhaust using an induced electric charge.

Vapor Recovery Nozzle

An air pollution control device on a gasoline pump that minimizes gas fumes from escaping into the atmosphere.

Acid Deposition

The mixture of acidic rain, snow, fog, and particles; caused by NOx and SOx from motor vehicles and coal plants.

Effects of Acid Deposition

Direct damage to plants, soil acidification, lake acidification, and corrosion of human-made structures.

Sick-Building Syndrome

A condition where buildings have poor air quality due to pollutants like CO, formaldehyde, radon, and fungi.

Radon-222

A colorless, odorless, radioactive gas produced by the decay of uranium-238; seeps into homes and is the second leading cause of lung cancer.

Carbon Monoxide (CO)

An indoor air pollutant classified as an asphyxiant, produced by common combustion sources.

Clean Air Acts (1970, 1977, 1990)

U.S. Congressional acts that established National Ambient Air Quality Standards (NAAQs) and regulated the use of lead in fuels.

Greenhouse Effect

The process in which greenhouse gases trap heat (infrared radiation) in the troposphere, leading to higher temperatures near the Earth.

Greenhouse Gases (GHGs)

Gases that trap heat, including H2O, CO2, N2O, CH4, and CFCs.

Carbon Dioxide (CO2)

Major GHG from fossil fuel burning and deforestation; GWP of 1 (reference point).

Methane (CH4)

GHG from fossil fuels, wetlands, and livestock; 20 times as potent as CO2 over 100 years.

Water Vapor (H2O)

The gas most responsible for the greenhouse effect (60-70%); its concentration creates a positive feedback loop.

Global Warming

The predicted increase in the Earth's average temperature due to the greenhouse effect.

Effects of Global Warming

Stronger storms, more flooding/droughts, poleward shift of farming areas, and a rise in sea level.

Albedo

The ability of the Earth's surface to reflect light.

Kyoto Treaty (1997)

First major international agreement on GHG emissions, aimed to reduce emissions by 5% from 1990 levels by 2012.

Paris Agreement (2015)

International agreement to limit global warming to 1.5°C, requiring a target of net-zero emissions.

Ozone Layer (Stratospheric)

Layer in the stratosphere that absorbs the majority of ultraviolet radiation.

Chlorofluorocarbons (CFCs)

Halocarbons used as refrigerants/propellants that destroy stratospheric ozone; have the highest GWP.

Ozone Thinning (Stratosphere)

Caused by CFCs, creating a thinning (not a hole) in the ozone shield, particularly above the south pole.

Montreal Protocol (1987)

International agreement that successfully phased out CFCs and other ozone-depleting substances.

Ocean Warming

Caused by the increase in greenhouse gases in the atmosphere, affecting marine species through habitat loss, and metabolic/reproductive changes.

Ocean Acidification

The decrease in pH of the ocean caused by the uptake of excess atmospheric CO2 from anthropogenic activities.

Positive Feedback Loop (Ice-Albedo)

The process where melting polar ice (high albedo) exposes darker land/ocean (low albedo), which absorbs more solar energy, causing more warming.