Air Pollution Control Quizes
Define "penetration" as it applies to Air Pollution Control.
penetration = 1 - efficiency a measure of efficiency, penetration measures the amount of pollutant not removed (amount that passes through control device).
List two methods of reducing operating leaks.
-floating roof tanks -vapor conservation value
What human health effects might result from NO2 exposure?
-nose, eye irritation at 10-30 ppm -bronchitis and pneumonia -long term effects (i.e. emphysema)
The maximum level to which a parcel of air will ascend under a given set of conditions is known as what?
The mixing height
What factor in engine design has the most impact on pollutant emissions?
The most significant factor in engine design is the required Air-to-Fuel (A/F) ratio.
Describe (briefly) the main global air circulation patterns. What causes them and what shape do they take.
The patterns are set by the polar/equatorial temperature gradient modified by Coriolis forces. Cell stability breaks these into three bands flowing east or west. Trade winds: from east to west between the equator and 30 degree line Westerlies: from west to east between the 30 and 60 degree lines Easterlies: from east to west between the 60 degree lines and the poles
Define "Air Pollution"
The presence of undesirable material in the atmosphere in quantities large enough to produce/cause harm
Vertical mixing due to buoyancy is increased when atmospheric conditions are;
Unstable
Which criteria pollutant is of least concern when looking at indoor air quality?
VOCs
Define VOCs and explain the main reasons they are regulated.
Volatile Organic Compounds -gases that are emitted into the air from products or processes. Some are harmful by themselves, including some that cause cancer. In addition, some can react with other gases and form other air pollutants after they are in the air. (CO2, SO2, H2S, benzene, ethylene glycol, formaldehyde, methylene chloride, tetrachloroethylene, toluene, xylene, and 1,3-butadiene)
Name the main categories of particulate control devices and give 2 examples of each.
Wall Collection Devices -Gravity Settlers -Cyclone Separators -electrostatic Precipators Dividing Collection Devices -Filters (surface & depth) -Scrubbers
In words and perhaps a general equation, how is the terminal velocity of a particle in a cyclone determined?
the constant speed that a freely falling object eventually reaches when the resistance of the medium through which it is falling prevents further acceleration Equation: *
What does bar length signify on a wind rose?
the percent of time the wind blow FROM that direction
What is the difference between a "statute" (a.k.a. "law") and a "regulation"? With respect to air pollution control, what group is responsible for each?
"Laws" provide the authority and set the scope for air pollution regulation, and are passed by Congress. "Regulations" define the specific requirements that must be met to satisfy the law; these are developed and enforced by the EPA.
What is the formula for determining the efficiency of a pollution control device?
(amount removed) / (amount fed into the system) OR ( IN - OUT ) / ( IN )
How does atmospheric buoyancy relate to atmospheric conditions?
*
VOCs often enter the atmosphere due to "leaks". Some are due to equipment failures and flaws, but many are caused by operating procedures. List three significant types of operations related leaks.
*
The environmental, or prevailing, lapse rate is determined from what conditions?
- Air Temperature - Altitude - Air Pressure The distribution of temperature in the vertical
List four major consequences of nitrogen oxide pollutants in the atmosphere.
- Smog contributor -- nitrogen compounds lead to the brownish color - Acid deposition - Reacts with VOC and sunlight to make photochemical oxidants (i.e. O3) - Plant damage - Human health effects
What two atmospheric factors influence the buoyancy of an air parcel?
- Temperature (Air) - Pressure
What are "acid gases"? Give an example
- any gaseous compound that when dissolved in water will form an acidic solution -CO2 -H2S
When using an emissions factor what three things must you know to calculate the emissions rate?
- emissions amount - Activity Rate - emissions reduction efficiency
Summarize the health effects of exposure to particulate matter.
- eye, nose, throat and lung irritation, coughing, sneezing, runny nose and shortness of breath - affect lung function and worsen medical conditions such as asthma and heart disease
List the primary components of a pollution control system (5)
- gas capture - control device - gas mover - disposal mechanism/system - stack
What are the two main approaches to control of nitrogen oxide emissions?
- modify the combustion process to reduce/prevent formation - treat flue gas to convert NOx to N2
List three main advantages to the use of cyclone separators.
- small footprint - low capital cost - the ability to operate at high temperatures - can handle liquid mists or dry materials - low maintenance requirements
List 3 ways to improve pollutant dispersion.
- taller stacks - intermittent controls - plant relocation (ILLEGAL)
How do the adiabatic lapse rate and the environmental lapse rate relate to each other?
- the environmental lapse rate is equal to the dry adiabatic rate - the greater the amount of vapor, the smaller the adiabatic lapse rate
List major variables that effect plume rise
- the gas being released - the temperature of the gas being released - the flow velocity - atmospheric stability - the ambient temperature and pressure
When controlling combustion conditions to reduce NOx formation, what three variables are most significant?
- the peak temperature - the residence time at high temperature, and - the oxygen concentration at the high temperature.
What is an "acid dew point"?
- the temperature where water condenses with acid droplets to from acid
What are the key assumptions underlying Gaussian plume models?
- wind speed is constant - wind direction is constant - emission rates are constant - the terrain is flat - deposition is negligible - the shape of the plume is conical
What is the most common approach for preventing sulfur oxide pollution from refineries and natural gas processing?
-Ore processing and metal smelting produce streams with high concentrations of SO2, containing up to 40%.. -Electric power plants (mostly coal burning) produce large volume streams with relatively low concentrations of sulfur dioxide (less than 4%)
List four key differences between sulfur oxide and nitrogen oxide pollutants.
-Sulfur is a "contaminant" in fuels and can be removed prior to burning. NOx is a consequence of burning any fuel. -Motor vehicles are a major source of nitrogen oxides, but not of sulfur compounds -Sulfur compounds can be fixed in a solid form (i.e. elemental, gypsum), but no equivalent form exists for nitrogen compounds -Nitrogen oxides are much more difficult to absorb in water and convert to acid
Briefly explain atmospheric stability.
-a measure of atmospheric status which determines whether or not air will rise, sink, or be neutral. In general stability refers to air tendency to rise or to resist vertical motion - Stability refers to vertical circulation within the atmosphere. It can be assessed by comparing the actual lapse rate to the adiabatic lapse rate. In an unstable atmosphere, a quantity of air that is displaced will continue to move in the direction of displacement, whereas in a stable atmosphere it will tend to return to its original level. - the atmosphere is said to be absolutely stable if the environmental lapse rate is less than the moist adiabatic lapse rate
List and define the three types of inversions
1. Frontal inversion -- warm air mass overruns cold mass, usually at high altitude 2. Subsidence inversion - sinking cold air traps rising warm air 3. Radiation inversion - created by rapid cooling of ground by radiation
How many HAPs are there? List two.
188+ HAPs - Asbestos - Mercury - Xylene - Styrene - Benzene - Toluene - Chromium - Arsenic - Formaldehyde - Lead
How many "criteria pollutants" are there? List them.
6 Criteria Pollutants - Particulate Lead - Ozone - Carbon Monoxide - Sulfur Dioxide - Nitrogen Oxides - Particulate Matter [2.5 micrometers]
The WHO (World Health Organization) publishes air pollution standards. It is estimated that ______ percent of the world's population lives in areas where these standards are NOT met.
99%
What is a "secondary pollutant"? Give an example.
A "secondary pollutant" is formed in the atmosphere by a reaction involving other compounds. Ozone is an example.
What is a "threshold limit value"?
A TLV is a limit on toxin exposure. Persons exposed to less than the TLV are not expected to experience harmful effects.
What are "fumigations" and "stagnations"?
A plume of pollutant trapped by an inversion with no dilution is called fumigation. A stagnation is an air mass that remains in place for 4 or more days
TDEC (Tennessee Department of Environment and Conservation)
A state level regulatory authority
What is the most common adsorbent for VOC control?
Activated Carbon
What is the difference between adsorption and absorption?
Adsorption compounds cling to the surface of the molecule, whereas absorption substances enter the bulk phase of a liquid or solid. Absorption where a liquid is soaked up into something like a sponge, cloth or filter paper Adsorption Adsorption refers to individual molecules, atoms or ions gathering on surfaces
List the primary advantages and disadvantages of scrubbers used for particulate control.
Advantages - can handle flammable and explosive dusts with little risk - provides gas absorption and dust collection in a single unit - provides cooling of hot gases - compact; can often be retrofitted into existing collection systems - corrosive gases and dusts can be neutralized Disadvantages - high potential for corrosion problems - collected particulate may be contaminated and unrecyclable - protection against freezing required (some streams may require reheating to avoid visible plume) - disposal of waste sludge can be very expensive - requires makeup water to replace purged liquid and disposed sludge
Expand and define AQCR
Air Quality Control Region - area designated as region for regulation and enforcement of ambient air standards
NAAQS (National Ambient Air Quality Standards)
Air quality standards mandated an enforced by the EPA are pollution standards for six priority pollutants set by the Environmental Protection Agency through the Clean Air Act
Air pollution has traditionally been linked solely to respiratory and cardiovascular health issues. Recent research has identified impacts on brain health. List the three main brain consequences.
Alzheimer's Dementia Neurodegeneration from chronic inflammation Impaired cognitive ability
What are the two main categories of pollutant measurements?
Ambient Monitoring (Air Quality) Source Testing (Emissions)
What are the differences between an "air quality standard" and an "emissions standard" as applied to developing air pollution control regulations. Give an example of current federal regulations in each category.
An "air quality standard" is a result driven approach that sets values for quality and requires controls to maintain, as such it reflects the concentration and location of sources and requires action only when ambient falls below the standard. EXAMPLE: NAAQS An "emissions standard" is a source driven strategy that specifies the maximum emission for each source type, and all members of a class must meet the same standard. EXAMPLES: NSPS, NESHAP
What is "enteric fermentation"?
Animal (cow) farts -Enteric fermentation is a digestive process by which carbohydrates are broken down by microorganisms into simple molecules for absorption into the bloodstream of an animal. It is one of the factors in increases methane emissions This digestive process comes from farts by the animals.
Why are automobiles more likely to produce pollutants than stationary sources?
Automobiles produce more CO, HC, and NOx than stationary sources, because: -car engines are more likely to run oxygen deficient -the fuel-air mixture is preheated, unlike most other combustion processes -combustion in an IC engine is unsteady, whereas a furnace tends to have a continuous flame -engine flames often directly contact cold surfaces.
What color is associated with CO exposure?
CO is colorless, odorless, tasteless
What is the primary greenhouse gas emitted as a result of human activity?
CO2 Carbon Dioxide
What four gases (or groups of gases) does the EPA consider to be "greenhouse gases?"
Carbon Dioxide Methane Nitrous Oxide Fluorinated Gases*
List two "causes" and two "sources" of particulates in air pollution.
Causes - Combustion - Gas Conversion in the atmosphere - Materials Handling Sources - Powerplants - Vehicles - Industrial Plants
What are the main causes and sources of sulfur oxide pollutants?
Causes: Combustion of sulfur containing fuel (Sulfur exists as a contaminant in fuels). Sources: Coal & oil fired power plants
What are the two functions that take place within an ESP?
Charging Function & Collecting Function
NSPS (New Source Performance Standards)
Clean Air Act (CAA) section 111(b) and are issued for categories of sources which EPA has listed because they cause, or contribute significantly to, air pollution which may reasonably be anticipated to endanger public health or welfare.
What weather conditions are most likely to produce an unstable atmosphere?
Cloudy Weather (thunderstorms, tornadoes, lightning, hurricanes, etc.)
Combustion produces SO2. Briefly describe what may happen to atmospheric sulfur dioxide.
Combustion (which is a rapid oxidation reaction) of bound sulfurs produces sulfur dioxide SO2. In the atmosphere, the dioxide oxidizes to sulfur trioxide, SO3. This then can combine with atmospheric water to produce sulfuric acid, H2SO4, which may deposit on plants, buildings, etc., or precipitate as acid rain.
Explain the difference between "concentration models" and "dispersion models" for pollution.
Concentration Models - Box Models - Ambient monitoring - Criteria Pollutants - Air Quality Standards - concern RESULTS Dispersion Models - Plume Models - Source Testing - Hazardous Air Pollutants - Emissions Standards - concern SOURCES
List three methods that VOC emissions may be "controlled by recovery".
Condensation Absorption Adsorption
What three groups of actions can be taken to "control" indoor air quality?
Controlling indoor air quality involves: 1. control of indoor sources of pollutants 2. dilution and removal of pollutants through ventilation 3. "cleaning" of air by capture and destruction of pollutants, most commonly in recirculated air
List two differences between "criteria" and "hazardous" pollutants.
Criteria Pollutants - 6 of them (Lead, Ozone, Carbon Monoxide, Sulfur Dioxide, Nitrogen Oxides, Particulate Matter[2.5]) - Ambient Monitoring - Air Quality Standards - NAAQS - Concentration Models - Results Hazardous Pollutants - 180+ - Source Testing - Emission Standards - NESHAP, NSPS - Dispersion Models - Sources
Health effects of air pollution depend on "dosage". How is the dose determined?
Dosage is the integral/sum of concentration and time
What is the typical approach taken to reduce sulfur oxide emissions from power plants?
Electric power plants (mostly coal burning) produce large volume streams with relatively low concentrations of sulfur dioxide (less than 4%)
Expand and define ESP
Electro-Static Precipitator - a device that removes particles from a gas stream by using electrical energy to charge particles either positively or negatively
When using an emissions factor, what three things (beside the factor value) must you know to calculate the emissions rate?
Emissions Activity Rate Overall Emission Reduction Efficiency (%)
Briefly describe how energy conservation practices and indoor air quality are related.
Energy efficiency and indoor air quality are both desirable features in a building. Energy efficiency reduces the operating cost and environmental impact of buildings, while indoor air quality creates a healthier environment for occupants Building designers, contractors, owners and managers have long been challenged with providing quality indoor environments at a reasonable energy cost. Current efforts to improve building energy efficiency, including goals of sustainability and net-zero energy use, are bringing more focus on how to simultaneously achieve energy efficiency and good indoor air quality (IAQ). While energy efficiency and IAQ are sometimes viewed as incompatible, there are many strategies than support both ends. This paper discusses the relationship between IAQ and energy efficiency, with outdoor air ventilation being the primary connection. A number of strategies that are currently being used or proposed to provide both improved IAQ and energy efficiency are highlighted including increased envelope airtightness, heat recovery ventilation, demand controlled ventilation, and improved system maintenance.
The effects of air pollution are mostly acute in nature
False
What is the most common particulate control device? How does it work?
Filters -particles collect on the surface of the filter but allows the liquid or gas to pass through
Cyclones are most effective when used on particles __________ or larger.
Fine
Briefly outline the main sources and natural removal mechanisms for the three sizes of particles.
Fine -> Aerosols - agglomerate over time to from bigger particles Midsize -> secondary formation - captured by rain (washout or rainout) Large ->mechanical processing - settle via gravity
Briefly describe the process for flue gas desulfurization.
Flue gas is first treated to remove fly ash and other solids (particulate). It is then combined with air, crushed limestone, and water in the scrubber. The slurry mixture then enters a recirculation loop (or tank) where most of the conversion reaction occurs.
What is the primary cause of nitrogen oxides in the atmosphere?
Fuel burned with air -- at high temperatures N2 burns to NO and NO2 Organically bound NO will combust
What is the primary component of smog?
Ground level ozone NOx gives it the brown color
HAP (hazardous air pollutants)
Hazardous air pollutants, also known as toxic air pollutants or air toxics, are those pollutants that are known or suspected to cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental effects. EPA is working with state, local, and tribal governments to reduce air emissions of 188 toxic air pollutants to the environment.
Which mobile source pollutants are US regulators primarily concerned with?
In the US, the mobile emissions of primary concern are CO, NOx, and VOCs.
What are the five main groups of indoor air pollutants?
Indoor pollutants may be grouped into five categories: 1. VOCs 2. Inorganics 3. Particulate 4. Radon 5. Biological Materials
How do most non-automotive sources of lead emissions work? How is it best to control these?
Lead is emitted from non-automotive sources due to the boiling of lead or of lead salts. The lead vapors formed enter the atmosphere, and when cooled produce extremely fine particles. Thus to control these sources, the best practice is to cool the exhaust gas enough to condense the lead particles, and then use a good particulate control system to remove them.
Who is the "regulatory authority" for air pollution in Memphis?
Memphis/ Shelby County Air Pollution Control
The adiabatic lapse rate for a given element of air will intersect the environmental lapse rate at the:
Mixing Height
As the air-to-fuel ratio increases, what happens to NOx emissions?
Modern vehicles precisely control the A/F ratio to produce less NOx without making additional CO and VOCs. The shift from carburetors to fuel injectors is associated with this improved control. The compression ratio is also a factor in performance. The higher the CR, the more power produced, but this means higher temperatures and thus more NOx. Generally speaking, diesel engines run at a lower A/F ratio and so are less likely to produce CO and VOCs. However, they also operate at higher pressures and temperatures and so produce comparatively NOx. Additionally, diesel engines have a tendency to produce odors and PM (soot), especially during the acceleration from a sop, as unburned fuel is released. (You've probably seen the smoke.)
Show the chemical reaction that produces smog.
NO + VOC + O2 + sunlight ===> NO2 + O3
Expand and define NESHAP
National Emission Standards for Hazardous Air Pollutants - an Environmental Protection Agency (EPA) standard that is applicable within the United States to the emissions of hazardous air pollutants produced by corporations, institutions, and agencies at all levels of government. Hazardous air pollutants are those pollutants that are known or suspected to cause cancer, serious health effects, or adverse environmental effects.
Expand and define NAAQS
National Ambient Air Quality Standards - an air quality standard that defines the maximum amount of a pollutant averaged over a specified period of time that can be present in outdoor air without harming public health
Expand and define NSPS
New Source Performance Standard - source thresholds to promote continuous emissions reduction; apply only to new or substantially changed sources
List 3 events that might initiate the EPA rule making process.
New legislation Statutory reviews Accidents Lawsuits
what is sick building syndrome? The high cost of energy for heating, has led to homes and office buildings being made "tighter" with less air exchange to the outside. This tends to trap any air contaminants inside the building and may lead to sick building syndrome.
Often in new or renovated buildings sick building syndrome occurs. This is because new buildings contain many products made with synthetic materials and glues that may not have fully dried out. A significant amount of off-gassing occurs. A buildup of toxic compounds and pollutants in an airtight space; in buildings with good insulation and tight seal against air leaks, sick building syndrome can occur.
What indoor pollutant is often emitted by particle board, glues, carpets, etc?
One of the most concerning VOCs in the indoor environment is formaldehyde (HCHO). It is emitted by particle board, plywood, veneers, glues, carpets, and insulation among other sources. The rate of release increases with temperature. This type of pollutant will be worse in new buildings, as the rate of emission will slow over time. Formaldehyde is an eye irritant at low concentrations (0.01 to 2 ppm) and a respiratory irritant at higher concentrations (5-30 ppm).
What is a "technology forcing" regulation?
One that requires new technologies to be developed in order to meet regulatory standards.
List five factors influencing pollutant emissions from internal combustion engines.
Pollutant emissions from IC engines are effected by: 1. engine design 2. driver operating and maintenance practices 3. fuel composition 4. add-on pollution control technologies 5. environmental conditions
List two main approaches for controlling VOC Emissions.
Prevention (substitution, process modification, leakage control) Recovery (condensation, absorption, adsorption)
The NAAQS sets limits based on "primary standards" and "secondary standards". What is the difference?
Primary Standards - Protect Public Health Secondary Standards - Protect Public Welfare
What is radon?
Radon gas is a carcinogen formed as a radioactive decay product of materials naturally occurring in rocks and soils of many parts of the world, It moves through the soil and enters homes through cracks in foundations, slabs, around pipes, etc. Radon exposure has been linked to lung cancer; some sources suggest that 10-20% of US lung cancer deaths are linked to radon exposure.
How does CO effect human physiology?
Reacts with hemoglobin to block oxygen transfer Ka for absorption is 210 times that of oxygen
What is the key factor in establishing separation within a scrubber?
Separation in the scrubber depends on relative velocity between particles and droplets
What are the four main oxidation states of sulfur, as pertains to air pollution issues?
SO2 SO3 SO4 H2SO4*
What are the key consequences (effects) of sulfur oxides in the atmosphere? (I'm looking for four categories of effect, each of which might have subdivisions).
SO3 forms acid when combined with water -acid deposition -acid mists -corrosion Plant tissue damage -- chlorosis (loss of chlorophyll) SO2 is soluble and may be absorbed in the upper respiratory tract -taste at 0.3 ppm -odor at 0.5 ppm -bronchioconstriction at 1 ppm -eye, ear, nose irritation at 10 ppm Effect may be intensified when combined with other pollutants, especially particulate
What control device would you suggest for removing sulfuric acid droplets from a gas stream before it is discharged? Explain your choice.
Scrubber -suitable for mists -can neutralize corrosive gases/dusts
What is the key to controlling CO emissions?
Since most CO comes from vehicle engines, the most effective means of control is to reduce vehicle emissions. In order to prevent formation of CO, supply ample excess air and insure thorough fuel-air mixing.
List four indoor sources of particulate.
Smoke is visible evidence of incomplete combustion. It will generally include particulate and gases. Tobacco smoke has a large range of chemicals. Smoke from cooking, from candles, wood stoves, and fireplaces also leads to particulate release indoors. Other indoor sources of particulate include animal dander, mold spores, dust mites, cotton fibers, insect parts, human hair and skin cells, etc.
Expand and define SIP
State Implementation Plan - policies, programs, and emissions budgets developed by state regulators to force AAQS
SIPs often require efforts to reduce/manage emissions from mobile sources. List three groups of approaches.
State implementation plans (SIPs) often require steps be taken to achieve/maintain air quality. These might include: - inspection and maintenance programs - transportation control measures - fuel changes
SIP (State Implementation Plan)
State plan that details the procedure that it will adopt in order to attain NAAQS
List and describe the main types of filter.
Surface - particles are retained mostly on the surface of the media, forming a layer of material that increases the efficiency or fineness of particles retained Depth - a thicker media or multiple layers of media, forming a torturous path to retain particles; media ideally retains larger particles at the surface and progressively finer particles through the thickness or layers
TLV (Threshold Limit Value)
The max amount of toxic substance to which a person can be exposed without adverse effect level a worker can be exposed to without adverse health effects, Based on 8 hour day, 40 hour week, 50 weeks a year (NIOSH term)
What are the main factors determining VERTICAL circulation in the atmosphere?
Temperature related density differences.
What is the "lead-crime hypothesis?"
The lead-crime hypothesis postulates that lead exposure damages brain development in children leading to increased aggression and poor impulse control. When these children are grown, they are more likely to commit violent crime. The primary source of the lead exposure of children from the 1940s to the 1970s was motor vehicle emissions. The phase out of TEL reduced the average level of lead in children's blood, and thus contributed to the drop in crime seen in the 1990s. Historical data shows that violent crime rates track blood lead levels, trailing by about 22 years. The harmful effects of lead have been known for centuries. These effects do not depend on how the lead enters the body (ingestion, respiration, etc.)
What are "washout" and "rainout"? Be sure to explain the difference.
Washout - when midsize particulates are captured by raindrops/other precipitation Rainout - when midsize particulates are captured by/in a cloud
What are the three groups of transportation control options?
Transportation control measures generally can be grouped into - transit options - economic incentives and/or penalties - and regulatory steps.
OSHA (Occupational Safety and Health Administration)
With the Occupational Safety and Health Act of 1970, Congress created the Occupational Safety and Health Administration (OSHA) to ensure safe and healthful working conditions for workers by setting and enforcing standards and by providing training, outreach, education and assistance.
What is the main weakness of a box model for air pollution?
You must assume - PERFECT MIXING within the cell -a CONSTANT/STEADY wind
Broadly speaking, how would you define an emissions factor?
a representative value that attempts to relate the quantity of a pollutant released to the atmosphere with an activity associated with the release of that pollutant.
(ADEQ ) Arizona Department of Environmental Quality
a state level regulatory authority
EPA (Environmental Protection Agency)
an independent federal agency established to coordinate programs aimed at reducing pollution and protecting the environment Federal agency created in 1970 to oversee environmental monitoring and cleanup programs
For purposes of defining VOC pollutants, what is the criteria for "volatility"?
an organic compound having an initial boiling point less than or equal to 250° C measured at a standard atmospheric pressure of 101.3 kPa. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a trait known as volatility
NESHAP (National Emission Standards for Hazardous Air Pollutants)
are stationary source standards for hazardous air pollutants.
CFCs (chlorofluorocarbons)
chemicals used in coolants, solvents, and aerosol cans that damage the ozone layer (cfcs: an abbreviation for the gases which have now been removed from aerosols to protect the ozone layer.)
AQI (Air Quality Index)
index for reporting daily air quality that tells you how clean or polluted your air is, and what associated health effects might be a concern for you. used to measure and report air quality in a specific area (color coded & numbers)
Why was lead in gasoline?
octane enhancer in motor fuels During most of the second half of the 20th century, over 85% of the atmospheric lead came from the use of tetraethyl lead (TEL) as an octane enhancer in motor fuels. In the US, phasedown of TEL use cleared the courts and began being enforced in 1976; the ban was complete for all on-road vehicles in 1996. During this time, levels of atmospheric lead dropped by 97%. Some European countries eliminated TEL in the same time-frame, and in 2000 the ban became EU wide.
What are the two larges (US) sources of greenhouse gas emissions?
transportation & electricity generation