Chapter 1

An Introduction to Environmental Issues

Multiple pathwaysare possibleExposure Routes

1. Inhalation2. Ingestion3. Dermal (skin)

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. High Henry’s 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)

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 Low-Temperature Condenser

1. High atmospheric reaction-rate constant;

2. Low global warming potential;

3. Low ozone depletion potential.

Scope of environmental impacts

Raw MaterialsExtraction

Energy

Wastes

ChemicalProcessing

Wastes

ProductManufacturing

Wastes

Use, Reuse,Disposal

Wastes

Materials

Energy

Materials

Energy

Materials

Energy

Materials

Pollution Control

Pollution Control

Life-CycleStages

global warming

ozone depletion

smog formation

acidifi-cation

ecological harm

Human healthand ecosystem damage

Midpoints

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, 1997Annual 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

ChemicalProcessing

EnergyMaterialsProducts

greenhousegas emissions CO2, CH4, N2O

climate change;sea level change

human mortalityor life adjustments

Cause and Effect Chain

CFCs

CO2

CH4

O3

N2O

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:

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.

3 2

2

3 22

Cl O ClO O

ClO O O Cl

O O O

Stratospheric Ozone and Related Impacts

ChemicalProcessing

EnergyMaterialsProducts

ozone depleting substancesCFCs, HCFCs

ozone layer lossincrease in uv

human mortalityor life adjustmentsecosystem damage

Cause and Effect Chain

0.E+00

2.E+05

4.E+05

6.E+05

8.E+05

1.E+06

1.E+06

1995 1996 1997

Year

Total On- and Off-site Releases

Toxics Release Inventory Data

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

ChemicalProcessing

EnergyMaterialsProducts

NOx and volatileorganic substances

photochemical oxidation reactions

human/ecologicaldamage from O3

and other oxidants

Cause and Effect Chain

NOx VOCs

12 3

4

5

6

7

1

2

34

5

6 7

1 - Chemical & Allied Processing2 - Petroleum & Related Industries

3 - Metals Processing, 4 - Other Industrial Processes5 - Solvent Utilization, 6 - Storage & Transportation7 - Waste Disposal & Recycling

VOCs

NOx 1997

1997

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

Fuel Combustion

Industrial Processes

Transportation

Miscellaneous

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 sulfur-containing 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 acid-containing 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

ChemicalProcessing

EnergyMaterialsProducts

SO2 and NOxemission to air

Acidification rxns.& acid deposition

human/ecologicaldamage from H+

and heavy metals

Cause and Effect Chain

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

SO2

1

23

5 7

4

6

1 - Chemical & Allied Processing2 - Petroleum & Related Industries3 - Metals Processing4 - Other Industrial Processes5 - Solvent Utilization6 - Storage & Transportation7 - Waste Disposal & Recycling

1997

Fuel Combustion

Industrial Processes

Transportation

Miscellaneous

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

ChemicalProcessing

EnergyMaterialsProducts

Toxic releases to air, water, and soil

Transport, fate, exposure pathways& routes

Human health damage; carcino-genic & non...

Petroleum Refining

9%

Chemical / Allied

Products51%

Transport-ation

Equipment7%

All Other Industries

16%

Primary Metals

8%

Electronic Equipment

9%

Chemical and Allied Products

27%

Primary Metals22%

All Other Industries

23%

Paper and Allied

Products5%

Petroleum Refining

3%

Rubber and Miscel-

laneous Plastics

3%

Transport-ation5%

Fabricated Metals

6%

Electronic Equipment

6%

RCRA HazardousWaste

EPCRAToxicWaste

Allen and Rosselot, 1997

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!)

Steps in risk assessment» Hazard assessment» Exposure assessment» Dose/response relationships» Risk characterization

Module 1: Risk assessment: introductory concepts

Risk = F(exposure x hazard)

Modules 1,2 Modules 1,2 Chapters 5,6 Chapters 2,5

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 Effects1. 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

Module 1: Hazard assessment