Transcript Chapter 1

Chapter 1
An Introduction to Environmental
Issues
Exposure Routes
1. Inhalation
2. Ingestion
3. Dermal (skin)
Multiple pathways
are possible
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
Formulation of an Industrial
Cleaner
To lower the aquatic toxicity of the solvent:
1.
2.
3.
4.
High Henry’s law constant (substance will volatize into the
air rather than stay in the water);
High biodegradation rate (it will dissipate before exerting
adverse health effects);
Low fish toxicity parameter (a high value of the
concentration lethal to a majority of test organisms or
LC_50);
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)
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).
Choice of Refrigerant for a LowTemperature Condenser
1. High atmospheric reaction-rate constant;
2. Low global warming potential;
3. Low ozone depletion potential.
Scope of environmental impacts
Materials
LifeCycle
Stages
Materials
Energy
Energy
Raw
Materials
Extraction
Wastes
Materials
Energy
Chemical
Processing
Pollution
Control
Materials
Energy
Product
Manufacturing
Wastes
Wastes
Use, Reuse,
Disposal
Pollution
Control
Wastes
Midpoints
global
warming
ozone
depletion
smog
formation
acidification
Human health
and ecosystem
damage
ecological
harm
Endpoint
Global Environmental Issues
• Global Energy Issues
• Global Warming
• Ozone Depletion in the Stratosphere
Energy Conversion Efficiency
• Primary energy source (fossil fuel) must be
converted to another form (heat or electricity).
• Examples: automobile (10%) and pump (13%).
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 world’s 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.
U.S. Energy Flows, 1997
Annual Energy Review 1997, U.S. DOE, Energy Information Administration, Washington, DC, DOE/EIA-0384(97)
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.
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 earth’s 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.
Global Warming and Related
Impacts
Materials Energy
Products
greenhouse
gas emissions
CO2, CH4, N2O
Chemical
Processing
O3
Cause and Effect Chain
climate change;
sea level change
human mortality
or life adjustments
N2 O
CH4
CO2
CFCs
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.
“Bad” Ozone
Tropospheric ozone, created by photochemical
reactions involving nitrogen oxides and
hydrocarbons at the earth’s 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.
“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.
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.
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.
Destruction of Ozone by CFCs
In the stratosphere, the CFCs are photo-dissociated to produce
chlorine atoms, which then catalyze the destruction of ozone:
Cl  O3  ClO  O2
ClO  O  O2  Cl
O3  O  2O2
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.
Stratospheric Ozone and Related
Impacts
Materials
Cause and Effect Chain
Energy
Products
Chemical
Processing
ozone depleting
substances
CFCs, HCFCs
ozone layer loss
increase in uv
Toxics Release Inventory Data
human mortality
or life adjustments
ecosystem damage
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.
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.
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.
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 (<3 hr) to NO2 at high
concentrations causes increases respiratory illness in
children and impaired respiratory function in
individual with pre-existing respiratory problems.
HCs/VOCs
• Major sources are the chemical and oil refining
industries, and motor vehicles.
• In 1997, industrial processes accounted for
51.2% while the transportation sector
contributed 39.9% of the total man-made HC
sources.
• Solvent comprise 66% of the industrial
emissions and 34% of the total VOC emissions.
Adverse Effects of Ground-Level
Ozone
• Ozone is a strong lung irritant, even at low
concentrations.
• Formaldehyde, peroxyacetylnitrate (PAN) and other
smog-related oxygenated organics are eye irritants.
• It affects crops and vegetations by disrupting
photosynthesis.
• It causes materials, such as rubber and latex painted
surfaces, to deteriorate by oxidation reaction.
Smog Formation and Related
Impacts
Materials
Energy
Chemical
Processing
Products
Cause and Effect Chain
NOx and volatile
organic substances
NOx
photochemical
oxidation reactions
VOCs
human/ecological
damage from O3
and other oxidants
1 - Chemical & Allied Processing
2 - Petroleum & Related Industries
6
7
1
5
NOx
Miscellaneous
Transportation
2
4
3
3 - Metals Processing, 4 - Other Industrial Processes
5 - Solvent Utilization, 6 - Storage & Transportation
7 - Waste Disposal & Recycling
7
1
6
2
3
4
Industrial Processes
Fuel Combustion
1997
VOCs
1997
5
National Air Quality and Emissions Trends Report, 1997, U.S. EPA Office of Air Quality Planning and Standards, http://www.epa.gov/oar/aqtrnd97/chapter2.pdf
Carbon Monoxide
• A by-product of incomplete combustion.
• Transportation sources account for the bulk
(76.6%) of total notation CO emissions.
• Areas with high traffic congestion generally
will have high ambient CO concentrations.
• High localized and indoor CO levels can come
from cigarettes, wood-burning fireplaces and
kerosene space heaters.
Lead
• Lead enters the body by inhalation and ingestion of
food, water, soil and airborne dust. It subsequently
deposits in target organs and tissues, especially the
brain.
• Lead in the atmosphere is primarily found in fine
particles (<10 microns). In 1997, industrial processes
accounted for 74.2%, with 13.3% resulting from
transportation, and 12.6% from non-transportation
fuel combustion.
• Lead also enters waterways in urban runoff and
industrial effluents.
Particulate Matter
• PM is the general term for microscopic
solid or liquid-phase particles suspended
in air (from a few Angstroms to several
hundred micrometers).
• Particles are either emitted directly from
primary sources or are formed in the
atmosphere by gas-phase reactions
(secondary aerosols).
“Fine” and “Coarse” Particles
• Since particle size determines how deep into the
lung a particle is inhaled, there are 2 NAAQS –
PM2.5 and PM10.
• Fine particles (<2.5μm) are composed of
inorganic salts (ammonium sulfate and nitrate),
organic species and trace metals. It can deposit
deep in the lung causing chronic bronchitis.
• Coarse particles(<10 μm) tends to deposit in the
upper respiratory tract causing asthma.
Environmental Effects of PM
• Limited visibility
• Nitrogen and sulfur containing particles
deposited on land increase soil acidity and
alter nutrient balance. When deposited in water
bodies, the acidic particles alter its PH and
lead to death of aquatic organisms.
• Soiling and corrosion of cultural monuments
and buildings made of limestone.
From SO2 and NOx to Acids
• SOxs are formed upon combustion of sulfurcontaining solid and liquid fuels in electric
facilities, metal smelting and other industrial
processes.
• NOxs are also produced in the combustion
reactions. Their origin is the oxidation of
nitrogen in the combustion air.
• They are transported over long distances and
transformed in the atmosphere by gas-phase
and aqueous-phase reactions to form sulfuric
and nitric acids.
Acid Deposition
• The acid is deposited to the earth’s surface as
either dry deposition of aerosols without
precipitation or wet deposition of acidcontaining rain.
• Acid rain is defined as having a PH less than
5.0.
Health Effects of SO2
• Irritation and swelling of upper respiratory
system and airway constriction.
• Long-term exposure leads to lung disease
and aggravates cardiovascular disease.
Environmental Effects of SO2
• Acidification of surface water
• Harm fish population by exposure to heavy
metals, e.g. aluminum in soil.
• Decrease plant grow.
Acid Rain / Acid Deposition
Materials
Energy
Chemical
Processing
Products
Cause and Effect Chain
SO2 and NOx
emission to air
Acidification rxns.
& acid deposition
human/ecological
damage from H+
and heavy metals
SO2
5
6
7
1997
Miscellaneous
4
1
Transportation
Industrial Processes
1 - Chemical & Allied Processing
2 - Petroleum & Related Industries
3 - Metals Processing
4 - Other Industrial Processes
5 - Solvent Utilization
6 - Storage & Transportation
7 - Waste Disposal & Recycling
Fuel Combustion
3
2
National Air Quality and Emissions Trends Report, 1997, U.S. EPA Office of Air Quality Planning and Standards, http://www.epa.gov/oar/aqtrnd97/chapter2.pdf
Air Toxics
• Hazardous air pollutants (HAPs) are airborne
pollutants that are known to have adverse human
health effects, e.g., cancer.
• There are over 180 chemicals identified on the Clean
Air Act list of HAPs by US EPA (1998), e.g., benzene,
hexane, perchloroethylene, etc.
• A Major Source is defined as a stationary source that
has the potential to emit 10 tons per year of any one
HAP on the list or 25 tons per year of any
combinations of HAPs, e.g., chemical complexes and
oil refineries.
Freshwater
• 70% of the earth’s surface is covered with water. Of
the total 1.36 billion cubic kilometers of water on
earth, 97% is ocean water, 2% is locked in glaciers,
0.31% is stored in deep groundwater reserves, and
0.32% is readily accessible freshwater (4.2 million
cubic kilometers).
• In US, freshwater use divided among several sectors:
agricultural irrigation 42%, electricity generation
38%, public supply 11%, industry 7%, and rural uses
2%. Groundwater resources meet about 20% of the
demand, with the remainder coming from surface
water sources.
Water Contamination Sources
• Point Sources are entities that release
relatively large quantities of wastewater at a
specific location, such as industrial discharge
and sewer outfalls.
• Non-point Sources include all remaining
discharges, such as agricultural and urban
runoff, septic tank leachate, and mine drainage.
Human Health Toxicity
Materials
Energy
Chemical
Processing
Transportation
Equipment
7%
RCRA
Hazardous
Waste
Primary
Metals
8%
Petroleum
Refining
9%
Products
Toxic releases to
air, water, and soil
Transport, fate,
exposure pathways
& routes
All Other
Industries
16%
EPCRA
Toxic
Rubber
Waste and Miscel-
Chemical /
Allied
Products
51%
Electronic
Equipment
9%
Allen and Rosselot, 1997
laneous
Petroleum Plastics
3%
Refining
3%
Human health
damage; carcinogenic & non...
All Other
Industries
23%
Paper and
Allied
Products
5%
Transportation
5%
Chemical
and Allied
Products
27%
Primary
Metals
22%
Fabricated
Metals
6%
Electronic
Equipment
6%
Module 1:
Risk assessment: important questions (Ch 2)
• What are the risks associated with a chemical,
manufacturing process, or use of a product?
• How is risk quantified by professional risk assessors?
• Is risk assessment used by government agencies to
regulate industry? (Yes!)
Module 1:
Risk assessment: introductory concepts
Risk = F(exposure x hazard)
Modules 1,2
Chapters 5,6
Modules 1,2
Chapters 2,5
Steps in risk assessment
»
»
»
»
Hazard assessment
Exposure assessment
Dose/response relationships
Risk characterization
Module 1: Hazard assessment
Indicators of chemical toxicology
Carcinogenic effects - Slope Factor (SF), Weight of Evidence (WOE)
classification
Noncarcinogenic effects - No Observable Adverse Effects Level (NOAEL),
Reference Dose (RfD), Reference Concentration (RfC), Permissible
Exposure Limit (PEL), Threshold Limit Value (TLV)
Sources of Data for Health Effects
1. The Material Safety Data Sheet - MSDS
2. NIOSH Pocket Guide to Chemical Hazards (www.cdc.gov/niosh.npg/gpdstart.html)
3. Integrated Risk Information System (IRIS) (http://www.epa.gov/ngispgm3/iris/index.html)
4. National Library of Medicine (ToxNet) (http://sis.nlm.nih.gov/sis1)
5. Casarett and Doull’s “Toxicology, the Basic Science of Poisons”, Macmillan
6. Patty’s Industrial Hygiene and Toxicology, John Wiley & Sons