CHEM 208 Lecture Notes - Lecture 5: Formaldehyde, Plywood, Fiberboard
28 Jun 2018
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The Air We Breathe
Air (which all of us must breathe) composes the atmosphere and is a complex
mixture of gases surrounding the Earth. The atmosphere is a layered structure
divided into layers according to a variety of criteria such as gradually changing:
-altitude
-pressure
-temperature
-electrical nature
-chemical composition and concentration
The Atmosphere:
-troposphere
-stratosphere
-mesosphere
-thermosphere/ ionosphere
The composition of Air
The air we breathe is a mixture of several gases, fine particles and vapors. Dry air
consists of 21% oxygen and 78% nitrogen plus traces of other substances that are
both natural and human-made
Major Components of air:
Nitrogen (N2)
Oxygen (O2)
Water (H2O)
Carbon dioxide (CO2)
Some minor components of air:
Carbon monoxide (CO)
Ozone (O3)
Oxides of Sulfur (SOx)
Oxides of Nitrogen (NOx)
Air Pollutants
Whereas major components are essential for life, the minor components are
pollutants, which under certain conditions may produce adverse environmental and
health effects. These air pollutants are emitted directly into the atmosphere during
combustion and production processes, changing the composition of atmosphere and
causing poor air quality.
The burning of fossil fuels (i.e., petroleum, natural gas and coal) can be used:
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to generate energy (electricity, gas and steam)
in transportation (combustion engines)
in industrial processes that use a great deal of energy sources (i.e., pulp and paper
mills, ore smelters, petroleum refineries, power generating stations and
incinerators)
These elements are mainly responsible for the presence of minor components. That
is, they are the major sources of human-created air pollution.
What is Carbon Monoxide?
-adequate supply of oxygen, there is a complete combustion of fossil fuels thereby
forming the major by products: carbon dioxide and water.
-Most carbon monoxide (CO) produced in this process is immediately oxidized to
carbon dioxide
-insufficient supply of oxygen, incomplete combustion of fossil fuels and carbon
monoxide gas released
-can be produced by other processes like combustion of organic matter during
waste incineration
-natural sources of carbon monoxide:
-forest fires
-volcanoes
-when a person inhales CO, it binds to the oxygen-carrying site on the hemoglobin of
red blood cells, causing a reduction of oxygen transport in the body
-because the hemoglobin can no longer take up oxygen from the air, resulting
in cell and tissue death
Health effects:
-impaired ability to use oxygen
-decreased athletic performance
-cardiac problems
Ground Level Ozone
-Ozone (O3) natural gas forms protective layer in atmosphere in the stratosphere
-protects the earth from ultraviolet radiation from the sun
-produced during photochemical reactions between volatile organic compounds
(VOCs) released in automobile exhaust and oxides of nitrogen (NOx) in sunlight
-generated in industrial processes like arc welding
health effects:
-damaged biological tissues and cells
-reduced lung function
-breathing difficulties and itchy, burning, watery eyes
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Oxides of Sulfur
-(SOx)
-released during processing (smelting) of mineral ores and combustion of fossil
fuels (burning coal/petroleum)
-pulp paper production and petroleum refining also generate oxides of sulfur
-emissions include sulfur dioxide (SO2) an sulfur trioxide (SO3)
-may lead to the formation of sulfuric acid (H2SO4) and sulfate salts (SO42-)
-most common natural source is volcanoes
Health Effects:
-problems breathing
-respiratory illness
Oxides of Nitrogen
-(NOx)
-sources of emission are: fuel combustion for transportation, home, industrial use,
manufacture of nitric acid (welding)
-forms in air because fuel is burnt at high temperatures
-once emitted, NO is oxidized forming nitrogen dioxide NO2
-emitted from natural sources like lightning and microbial activity of soil bacteria
Health Effects:
-lung damage
-shortness of breath
-chest pains
Entry into the Body
-inhaling (getting oxygen into carbon dioxide out of the body)
-opportunity for pollutants to diffuse into the blood stream via gas exchange in the
alveoli
-once pollutants are in body, it can cause health effects
(RISK ASSESSMENTS)
Exposure assessment: estimate concentration using chemical measurements
Effects assessment : relies on toxicity testing (estimates of exposure toxicity) and
computer models to extrapolate data from human population, animal, and bacterial
toxicity studies. Quantitative analysis of epidemiological, toxicological and exposure
data that are based on the accurate scientific evidence estimates exposure toxicity
and risk.
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Document Summary
Air (which all of us must breathe) composes the atmosphere and is a complex mixture of gases surrounding the earth. The atmosphere is a layered structure divided into layers according to a variety of criteria such as gradually changing: The air we breathe is a mixture of several gases, fine particles and vapors. Dry air consists of 21% oxygen and 78% nitrogen plus traces of other substances that are both natural and human-made. Whereas major components are essential for life, the minor components are pollutants, which under certain conditions may produce adverse environmental and health effects. These air pollutants are emitted directly into the atmosphere during combustion and production processes, changing the composition of atmosphere and causing poor air quality. These elements are mainly responsible for the presence of minor components. That is, they are the major sources of human-created air pollution.
