Air pollution with special reference to PANs, MTBE and CFCs.

1. AIR POLLUTION
PAN, CFC’s & MTBE
PRESENTATION TOPIC

3. What is air?
• The invisible gaseous substance surrounding the earth, mainly of
O2 & N2.
• Air is one of the essential factors making life on the Earth
possible.
• Protection of air from pollution is a matter of great importance.
• Oxygen and nitrogen compose ~99 % of inhaled air,
unfortunately we also inhale;Dust
particles
Water
droplets
Small amount
of other gases

4. Air and atmosphere:
Pollutants spread rapidly to far
distances in the atmosphere.
Troposphere contain almost 90% of all air mass.

5. What is air pollution?
Air pollution is a change in the physical, chemical and
biological characteristic of air that causes adverse effects
on humans and other organisms.
The ultimate result is a change in the natural
or ecosystem.

6. Types of air pollution:
1. Indoor air pollution:
• Pollutions from the housing materials and living and working
activities of the house.
• Around 3 billion people cook and heat their homes using solid
fuels (i.e. wood, charcoal, coal, dung, crop wastes) on open fires
or traditional stoves.
• The World Health Organization estimates that 4.6 million
people die each year from causes directly attributable to
air pollution. Many of these mortalities are attributable to indoor
air pollution.

8. Types of air pollution:
2. Outdoor air pollution:
• Pollutions from outdoor services and environmental
mixings, such as: transportation-automobiles,
industries-refineries, atomic energy plant-nuclear, and
community activities-cleaning of streets is referred as
outdoor air pollution.
• Outdoor air pollution is a complex
mixture of several pollutants.

9. What are air pollutants?
• An air pollutant is a substance in the air that can have
adverse effects on humans and the ecosystem.
• The substance can be solid particles, liquid droplets or gases.
• A pollutant can be of natural origin or man-made.
• In 1970, Congress passed the Clean Air Act that
established national air pollutant standards.

10. Types of air pollutants:
1. Primary air pollutants:
• Primary pollutants are usually
come in air directly by natural or
anthropogenic processes, such as
ash from a volcanic eruption.
Examples:
• CO from motor vehicle exhaust
• SO2 released from factories.
2. Secondary air pollutants:
• Secondary pollutants are not
emitted directly. Rather, they form
in the air when primary pollutants
react or interact.
Examples:
• Ground level ozone
• Sulphuric acid

12. Causes of air pollution:
• Emissions from industries and manufacturing activities
• Burning Fossil Fuels
• Agricultural activities
• Mining operations
• Indoor air pollution

13. Effects of air pollution:
• Acidification –acid rain
• Eutrophication
• Effects on wild life
• Respiratory and health problems
• Green house effect
• Global warming

14. PAN (Peroxyacyl nitrate):
• Peroxyacyl nitrates (also known as Acylperoxynitrates, APN or
PANs) are powerful respiratory and eye irritants present in the
photochemical smog.
• They are nitrates produced in the thermal equilibrium between
organic peroxy radicals by the gas-phase oxidation of a variety
of volatile organic compounds (VOCs), or by aldehydes and
other oxygenated VOCs oxidizing in the presence of NO2.

15. Example:
• Peroxyacetyl nitrate CH3COOONO2 (the most abundant
member of this family);
Figure shows structural formula of peroxyacetyl nitrate
Hydrocarbons + O2 + NO2 + light → CH3COOONO2
The general equation is:
CxHyO3 + NO2 → CxHyO3NO2

16. Effects of PANs:
• PANs are both toxic and irritating, as they dissolve more
readily in water than ozone.
• They are lachrymators, causing eye irritation at
concentrations of only a few parts per billion.
• At higher concentrations they cause extensive damage to
vegetation.
• Both PANs and their chlorinated derivates are said to
be mutagenic, as they can be a factor causing skin cancer.

17. Sources of PANs:
PANs are secondary pollutants, which means they are not directly
emitted as exhaust from power plants or internal combustion
engines, but they are formed from other pollutants by chemical
reactions in the atmosphere.Free radical reactions catalyzed by ultraviolet light from the sun
oxidize unburned hydrocarbons to aldehydes, ketones,
and dicarbonyl compounds, whose secondary reactions
create peroxyacyl radicals, which combine with nitrogen dioxide to
form peroxyacyl nitrates.

18. • Photochemical smog is a mixture of pollutants which
includes particulates, nitrogen oxides, ozone, aldehydes,
PAN, untreated hydrocarbons etc.
As constituents of photochemical smog:

20. CFCs (Chlorofluorocarbons):
• Chlorofluorocarbons, commonly known as CFCs, are a group
of man-made compounds containing chlorine, fluorine and
carbon. They are not found anywhere in nature.
• CFCs are also known as Freons, are chemicals with varying
numbers of carbon, chlorine, and fluorine atoms.
• Being nontoxic, noncorrosive and non-flammable, CFCs are
ideal for foams blowing and aerosols, as industrial solvents
and as a cooling medium in refrigerators and air
conditioners.

21. Effects of CFCs:
• Man-made CFCs however, are the main cause of
stratospheric ozone depletion.
• CFCs have a lifetime in the atmosphere of about 20 to 100
years, and consequently one free chlorine atom from a CFC
molecule can do a lot of damage,
destroying ozone molecules for a long time.
• Emissions of CFCs to date have accounted for roughly 80%
of total stratospheric depletion.

22. Effects of CFCs:
• The depletion of ozone layer causes UV rays to enter earth’s
atmosphere which in turn causes skin cancer, cataracts and
other eye damage.
• It is harmful on its own in large enough dosage
Overexposure may cause dizziness, loss of concentration,
Central Nervous System depression and/or cardiac
arrhythmia.
• Direct skin contact with some types of CFCs can cause
frostbite or dry skin.

23. Effects of CFCs:
• Whilst chlorine is a natural threat to ozone, CFCs which
contain chlorine are a man-made problem.
• Although CFC molecules are several times heavier than air,
winds mix the atmosphere to altitudes far above the top of
the stratosphere much faster than molecules can settle
according to their weight.
• When UV radiation hits a CFC molecule it causes one
chlorine atom to break away.

24. Destruction of ozone by CFCs:
CCl2F2 +UV → Cl' +CClF2
Cl + O3 → ClO + O2
ClO + O → Cl + O2
O3 +UV → O + O2
net 2O3 → 3O2

25. Sources of CFS’s:
• The most common emitter of CFCs are refrigerants,
particularly those used after the 1930s.
• Gasses containing CFCs were used for a long time as
components in aerosol cans and propellant liquids.
• Aviation regulations in some countries still require fire
suppression systems outfitted with Halon, a coolant
containing CFCs.

26. • As refrigerants and aerosol cans containing CFCs become
older and more obsolete, people tend to forget about
them, leaving them eventually to leak and further
contaminate the atmosphere.
• Chlorofluorocarbons are far less abundant than carbon
dioxide in the atmosphere, but they are 10,000 times
more powerful as a greenhouse gas and can remain in the
atmosphere for more than 45 to 100 years.
Sources of CFS’s:

27. Steps taken to stop CFC emission:
• The Montreal Agreement of September 16, 1987, laid down rules for the
phasing out of the production and use of CFCs (chlorofluorocarbons).
Every country in the world agreed and ratified this, the only time this has
happened in history.
• By choosing other products without CFCs.
• Unplug the electronic instruments when they are not in use.
• Replace your old refrigerators and air conditioners as they are the major
contributors of CFC in the atmosphere.
• Prefer buying energy-efficient appliances like fluorescent bulbs.
• Plant trees, as they absorb UV rays greatly and thus protect the
environment.

28. MTBE(methyl tertiary-butyl ether):
• Methyl tert-butyl ether (also known as MTBE and tert-butyl methyl
ether) is an organic compound with a structural formula
(CH3)3COCH3.
• MTBE is a volatile, flammable, and colourless liquid that is sparingly
soluble in water. It has a minty odour vaguely reminiscent of diethyl
ether, leading to unpleasant taste and odour in water.
• MTBE is a gasoline additive, used as an oxygenate to raise the octane
number.
• Its use is controversial because of its contamination
of groundwater and legislation favouring ethanol. However,

29. As an antiknocking agent:
• In the US it has been used in gasoline at low levels since 1979,
replacing tetraethyl lead as an antiknock (octane rating) additive to
prevent engine knocking.
• Oxygenates also help gasoline burn more completely, reducing
tailpipe emissions from pre-1984 motor vehicles; dilute or displace
gasoline components such as aromatics (e.g., benzene) and
sulphur; and optimize oxidation during combustion.
• Before the introduction of other oxygenates and octane enhancers,
most refiners had chosen MTBE primarily for its blending
characteristics and low cost.

30. Air quality benefits:
• MTBE had been used in U.S. gasoline at low levels since 1979 to
replace lead as an octane enhancer (helps prevent the engine from
"knocking"). Between 1992 and 2005, MTBE had been used at higher
concentrations in some gasoline to fulfil the oxygenate requirements
set by Congress in the 1990 Clean Air Act Amendments.
• Oxygen helps gasoline burn more completely, reducing harmful
tailpipe emissions from motor vehicles.
• Most refiners have chosen to use MTBE over other oxygenates
primarily for its blending characteristics and for economic reasons.

31. Effects of MTBE:
• The majority of the human health-related research
conducted to date on MTBE has focused on effects
associated with the inhalation of the chemical. When
research animals inhaled high concentrations of MTBE,
some developed cancers or experienced other non-
cancerous health effects.
• However, researchers have limited data about what the
health effects may be if a person swallows (ingests) MTBE.

32. Effects of MTBE:
• EPA's Office of Water has concluded that available data
are not adequate to estimate potential health risks of
MTBE at low exposure levels in drinking water but that
the data support the conclusion that MTBE is a potential
human carcinogen at high doses.
• Recent work by EPA and other researchers is expected to
help determine more precisely the potential for health
effects from MTBE in drinking water.

33. • In 1997, EPA issued a drinking water advisory of 20 to 40
ppb based on taste and odour. EPA is currently revising its
health risk assessment for MTBE. The status of the MTBE
health risk assessment can be found on the IRIS Chemical
Assessment Tracking.
• Blue ribbon panel
Effects of MTBE:

34. References:
• LaFranchi, B. W.; Wolfe, G. M. (2009). "Closing the peroxy acetyl nitrate budget:
observations of acyl peroxy nitrates (PAN, PPN, and MPAN) during BEARPEX 200".
Copernicus Publications.
• Rossberg, M. et al. (2006) "Chlorinated Hydrocarbons" in Ullmann's Encyclopedia of
Industrial Chemistry, Wiley-VCH, Weinheim.
• Squillace, P.J., J.F. Pankow, N.E. Korte, and J.S. Zogorski. (1997). “Review of the
Environmental Behavior and Fate of Methyl tert-Butyl Ether”. Environmental
Toxicology and Chemistry.
• Blue Ribbon Panel on Oxygenates in Gasoline. (1999). Achieving Clean Air and
Clean Water. Available on the Internet at:
http://www.epa.gov/OMS/consumer/fuels/oxypanel/r99021.pdf