Multiple pathways are possible Exposure Routes 1. Inhalation 2.
Ingestion 3. Dermal (skin)
Slide 4
Role of Chemical Engineer Examples: (1) formulation of an
industrial cleaner; (2) formulation of a paint solvent; (3) Choice
of refrigerant for a low-temperature condenser. What information
will a chemical engineer need to make informed pollution prevention
and risk reduction decisions? Impacts on human exposure (dermal,
inhalation and ingestion) Life cycle of a chemical
Slide 5
Formulation of an Industrial Cleaner To lower the aquatic
toxicity of the solvent: 1.High Henrys law constant (substance will
volatize into the air rather than stay in the water); 2.High
biodegradation rate (it will dissipate before exerting adverse
health effects); 3.Low fish toxicity parameter (a high value of the
concentration lethal to a majority of test organisms or LC_50);
4.Low Bioconcentration Factor, BDF (low tendency for chemicals to
partition into the fatty tissue of fish, leading to exposure and
adverse health effects upon consumption by humans)
Slide 6
Formulation of a Paint Solvent A chemical will have low risk
potential in the air if it has 1.Low toxicity properties (a high
Reference Dose [RfD] for inhalation toxicity to humans or a low
cancer potency); 2.Low reactivity for smog formation (ground level
ozone production).
Slide 7
Choice of Refrigerant for a Low- Temperature Condenser 1.High
atmospheric reaction-rate constant; 2.Low global warming potential;
3.Low ozone depletion potential.
Slide 8
Scope of environmental impacts Raw Materials Extraction Energy
Wastes Chemical Processing Wastes Product Manufacturing Wastes Use,
Reuse, Disposal Wastes Materials Energy Materials Energy Materials
Energy Materials Pollution Control Pollution Control Life- Cycle
Stages global warming ozone depletion smog formation acidifi-
cation ecological harm Human health and ecosystem damage Midpoints
Endpoint
Slide 9
Global Environmental Issues Global Energy Issues Global Warming
Ozone Depletion in the Stratosphere
Slide 10
Energy Conversion Efficiency Primary energy source (fossil
fuel) must be converted to another form (heat or electricity).
Examples: automobile (10%) and pump (13%).
Slide 11
World Energy Statistics From 1960 to 1990, world energy
requirements rose from 3.3 to 5.5 gtoe (gigatonnes oil equivalent).
Fossil fuels: 85%; renewable sources (hydroelectric, solar and wind
power): 8%; nuclear power: 6% (US-20% of electricity demand,
Japan-28%, Sweden-50%). Disparity in energy use 65-70% of the
energy is used by about 25% of the worlds population. The average
citizen in North America consumes almost 15 times the energy
consumed by a resident in sub-Saharan Africa. World energy
consumption is expected to grow by 75% in the year 2020 compared to
1995.
Slide 12
U.S. Energy Flows, 1997 Annual Energy Review 1997, U.S. DOE,
Energy Information Administration, Washington, DC,
DOE/EIA-0384(97)
Slide 13
Environmental Effects Associated with Energy Consumption Fossil
fuel combustion releases large quantities of (1) carbon dioxide
into atmosphere (global warming) and (2) oxides of nitrogen and
sulfur oxides (ground-level ozone and acid rain) Hydropower energy
generation requires widespread land inundation, habitat
destruction, alteration in surface and ground water flow, and
decreases the acreage of land available for agricultural use.
Nuclear power has environmental problems linked to uranium mining
and spent nuclear rod disposal. Use of wood has caused widespread
deforestation in localized regions of developing countries. Solar
power panels require energy-intensive use of heavy metals and
creation of metal wastes.
Slide 14
Greenhouse Effect The atmosphere allows solar radiation from
sun to pass through without significant absorption of energy. Some
of the solar radiation reaching the surface of earth is absorbed,
heating land and water. Infrared radiation is emitted from the
earths surface, but certain gases in the atmosphere absorb this
infrared radiation, and redirect a portion back to the surface,
thus warming the planet and making life possible. This process is
often referred to as greenhouse effect.
Slide 15
Global Warming and Related Impacts Chemical Processing
EnergyMaterials Products greenhouse gas emissions CO 2, CH 4, N 2 O
climate change; sea level change human mortality or life
adjustments Cause and Effect Chain Contribution to global Warming;
Phipps, NPPC, http://www.snre.umich.edu/nppc/ Climate Change 1995,
Intergovernmental Panel on Climate Change, WMO and UNEP, Cambridge
University Press, 1996.
Slide 16
Slide 17
Bad Ozone Tropospheric ozone, created by photochemical
reactions involving nitrogen oxides and hydrocarbons at the earths
surface, is an important component of smog. A potent oxidant, ozone
irritates the breathing passages and can lead to serious lung
damage. It is also harmful to crops and trees.
Slide 18
Good Ozone Stratospheric ozone, found in the upper atmosphere,
perform a vital and beneficial function for all life on earth by
absorbing harmful ultraviolet radiation.
Slide 19
Stratospheric Ozone Layer The stratospheric ozone layer is a
region in the atmosphere between 12 and 30 miles (20-50 km) above
ground level in which the ozone concentration is elevated compared
to all other regions of the atmosphere (10 ppm or 1 out of every
100,000 molecules). Ozone is formed at altitudes between 25 and 35
km in the tropical regions near the equator where solar radiation
is consistently strong throughout the year. Because of atmospheric
motion, ozone migrates to the polar regions and its highest
concentration is found there at about 15 km in altitude.
Slide 20
Chlorofluorocarbon (CFC) CFCs are highly stable chemical
structures composed of carbon, chlorine and fluorine, e.g., CCl3F
or CFC-11. CFCs reach the stratosphere due to their chemical
properties: high volatility, low water solubility, and persistence
(non-reactivity) in the lower atmosphere.
Slide 21
Destruction of Ozone by CFCs In the stratosphere, the CFCs are
photo-dissociated to produce chlorine atoms, which then catalyze
the destruction of ozone: Notice that the chlorine is not destroyed
in the reaction and can cause the destruction of up to 10000
molecules of ozone before forming HCl by reacting with
hydrocarbons. The HCl eventually precipitates from the atmosphere.
A similar mechanism also applies to bromine.
Slide 22
Stratospheric Ozone and Related Impacts Chemical Processing
EnergyMaterials Products ozone depleting substances CFCs, HCFCs
ozone layer loss increase in uv human mortality or life adjustments
ecosystem damage Cause and Effect Chain Toxics Release Inventory
Data
Slide 23
Slide 24
Slide 25
Air Quality Issues Air pollution sources includes stationary
(factories and other manufacturing processes), mobile
(transportation and recreational vehicles) and area sources.
Pollutants can be classified as primary, e.g., VOC and NOx, and
secondary, e.g., smog. Air quality problems are closely associated
with combustion processes occurring in the industrial and
transportation sectors of the economy.
Slide 26
Criteria Air Pollutant US Congress in 1970 passed Clean Air Act
which charged EPA with identifying those air pollutants which are
most deleterious to public health and welfare. EPA identified 6
substances as criteria air pollutants and promulgated primary and
secondary standards that make up the National Ambient Air Quality
Standards (NAAQS). Primary standards are intended to protect the
public health with an adequate margin of safety. Secondary
standards are meant to protect public welfare, such as damage to
crops, vegetation, and ecosystems or reduction invisibility.
Slide 27
Slide 28
From NOxs, HCs and VOCs to Ground-Level Ozone Ground-level
ozone is a component of photochemical smog. The precursor
contaminants are NOx and hydrocarbons. NOx along with sunlight
cause ozone formation, but the role of hydrocarbons is to
accelerate and enhance ozone accumulation.
Slide 29
Nitrogen Oxides NOxs are formed in high-temperature industrial
and transportation combustion processes. In 1997, transportation
sources account for 49.2% and non-transportation sources account
for 45.4% of the total NOx emission. Short-term exposure (
