Topic:

SMOGMTBEPANS

“SMOG”Air pollution observed in many urban areas is commonly referred to as

\SMOG.

Originally, identified with Smoke from coal fires mixing with low-lying Fogs.

The term Smog is derived from a combination of the SMOKE & FOG.

Types:The smog has usually two types named after the places where they were first observed, London & Los Angeles.

Reducing or Sulfurous Smog (London). Photochemical Smog (Los Angeles).

o London Smog: This type was identified by high concentrations of Sulphur dioxide (SO2) and particulate matter. London smog is therefore composed of air pollutants that are emitted directly by combustion processes and are called “Primary pollutants”. The most severe episodes of London smog occur in urban areas when low winds and a shallow boundary layer of air act to concentrate the pollutants in a relatively small air volume. The meteorological conditions that enhance this type of smog are usually observed in winter months during the early morning hours. This type of smog, which is characterized by high aerosol loadings and high levels of Sulphur Dioxide occurs in many cities that are burning coal today.

Beijing and Shanghai, China, Cairo, Egypt, Belgrade, Yugoslavia and Calcutta, India are current examples of urban centers with London type smog.

o Los Angeles Smog: It is an oxidizing smog formed from the photochemical reactions of Nitrogen oxides and volatile organic hydrocarbons, which are primary pollutants released from the combustion of Fossil Fuels in automobiles, power plants etc. Therefore, the Los Angeles smog is also known as Photochemical Smog. It is identified with high oxidant levels e.g. Ozone (O3) and haze from aerosols formed in the smog chemical reactions. Because these species are created in the atmosphere by photochemical reactions of the primary combustion pollutants, they are called Secondary pollutants. The Los Angeles type smog is therefore dependent on the daytime intensity of solar radiation, which promotes the formation of secondary oxidants and aerosols. In contrast to London smog, Los Angeles smog is formed during summer months and later in the day, after the solar radiation has had time to produce the secondary chemical air pollutants.

The trace gas species formed in photochemical smog include the secondary oxidants Ozone (O3), PANs and inorganic sulfuric and nitric acids. These oxidants and acids play important roles in effects of smog on agriculture and eco-systems, in human health and in materials damage on urban, regional and global scales.

Most major cities in the world today suffer from some form of photochemical smog, with some important examples being Mexico City, Rio de Janeiro and Sao Paolo, Brazil, Houston, Texas, USA, Santiago and Chile.

Smog then consists of aerosols and trace gas species that are concern due to their potential impacts on human health and biota (e.g. agricultural damage etc). Both aerosols and trace gas

species present in smog are also important in determining the radiative balance of the troposphere, a property known as the Green-house effect.

These species can heat the atmosphere by absorbing infrared and solar radiation, trapping it in the troposphere.

Aerosols can also contribute to cooling of atmosphere, both directly by scattering incoming solar radiations back to space and indirectly by enhancing cloud formation.

The net effects of aerosols on the radiative balance of the atmosphere depends on the types of aerosols present, their chemical compositions, and where in the atmosphere they ae formed.

Thus the impacts of smog formation on urban, regional and global scales are a cause for concern with regard to overall ecosystem well-being as well as human health.

Reactions of Smog: Sulfur dioxide can be oxidized to sulfur trioxide, a secondary pollutant:

2SO2 + O2 2SO3

Metallic particulates act as a catalyst for this reaction. In addition, free radicals from NO2 also speed up the reaction:

NO2 + UV light

SO2 + O 3

The formation of secondary pollutants in photochemical smog:1. Formation of NOx:

N2 + O2

2NO(g) + O2 2

2. Photo Dissociation of nitrogen dioxide to produce oxygen atoms:

NO2(g) + uv light NO(g) + O(g)

3. Atomic oxygen forms Ozone:

O(g) + O2(g) 3(g)

4. Formation Of organic free radicals:

3O + HC 3

Or

O3 + HC 3

5. Formation Of photochemical soup containing hundreds of chemicals including PANS:

R-CH=CH-R + O3 + CHO

Hydrocarbon alkanal free radials

R-CH=O + O + UV light R-C=O + OH

Free Radical

Effects of Smog on Human Health:

Because of the effects of ozone on our lungs, smog exposure may lead to several different types of short-term health problems: Coughing and throat/chest irritation: High levels of ozone can irritate our respiratory system.

We all know that outdoor aerobic exercises like running and biking are good for our health. But during the hottest days of summer, it’s not just excess heat we have to worry about, but smog, the concentrated air pollution we can often see hovering over the cityscape. During the hot summer months, smog can become a serious health problem in the Boston area. We are often downwind from the Midwest’s coal-fired power plants as well as the East Coast’s major cities.

Among air pollution’s cast of characters, ground-level ozone gas and the tiniest air pollution particles called PM2.5 play leading roles. While the PM2.5 particles come directly from our car exhaust, factories and distant coal-fired electric plants, irritating ozone gas builds up in the afternoon when sunlight chemically reacts with air pollution on hot days. The recent record-breaking heat waves dramatically increased the levels of ozone, which can cause sunburn-like effects on our delicate lungs.

Here’s how smog affects the human body. A mixture of the small PM2.5 particles get directly into our bloodstream by sneaking through the tiniest air sacs called alveoli. Once in our blood stream, these air pollution particles act like cigarette smoke, triggering inflammation that makes cholesterol stickier. This in turn promotes cholesterol blockages that build up and can cause heart attacks years later. In fact, people living in the most polluted cities in the U.S. were found to have up to a 10 percent higher chance of having a heart attack compared to those living in less polluted cities.

But there are a number of other negative health impacts as well. The Harvard School of Public Health has been gathering data on this for the past 30 years, and researchers are trying to get the word out to the public at large. However, it’s hard to compete with the loud voice and deep pockets of the air polluting industries. So what has research taught us so far? Children, senior citizens, and people with heart and lung conditions are especially vulnerable, but smog can impact even those of us in good health. Symptoms during high air pollution days range from eye and nose irritation that can amplify allergy and respiratory infections, increased cardiac and respiratory deaths.

It’s not surprising that the Harvard scientists found that children living in cities with the most air pollution have more asthma visits to the emergency room. But they were surprised to find higher rates of premature births in pregnant women and more sudden cardiac death from lethal heart arrhythmias in older adults.

To lessen the threat of smog :

While the best medicine is to decrease pollution, like using energy-efficient vehicles and appliances, there are things we can do personally to protect our lungs from higher levels of air pollution.

First — timing is everything. Urban smog is at its lowest early in the morning, so this is the best time for a jog or bike ride.

Try to avoid exercising around traffic or anywhere we can smell car exhaust. If we can smell it, the levels are likely too high to be healthy.

On the most polluted days, try to exercise indoors. Children as well as adults with asthma, active heart disease, or lung diseases, such as

chronic bronchitis or emphysema, should be especially careful. If we are stuck in a traffic jam, try switching our car air to “re-circulate” to avoid breathing in the tailpipe exhaust of the car in front of us.

Avoid close proximity to idling vehicles in parking lots — better yet, encourage others to cut their engines if they are not moving within a minute or two.

“MTBE (Methyl tertiary butyl ether)”“Methyl tertiary-butyl ether (also known as MTBE, tertiary-butyl methyl ether and tBME) is an organic compound with molecular formula (CH3)3COCH3. MTBE is a volatile, flammable, and colorless liquid that is sparingly soluble [1] in water. It has a minty odor vaguely reminiscent of diethyl ether, leading to unpleasant taste and odor in water.

MTBE is a gasoline additive, used as an oxygenated to raise the octane number. Its use is controversial in the US and declining in use in part because of its occurrence in groundwater and legislation favoring ethanol. However, worldwide production of MTBE has been constant at about 18 million tons/y (2005) owing to growth in Asian markets.

A growing number of studies have detected MTBE in ground water throughout the country; in some instances these contaminated waters are sources of drinking water. Low levels of MTBE can make drinking water supplies undrinkable due to its offensive taste and odor.

It causes cancer, hence it is carcinogenic at high doses.

The drinking water advisory document indicates that there is little likelihood that MTBE in drinking water will cause adverse health effects at concentrations between 20 and 40 ppb or below.

Contamination of water with MTBE:

There are opportunities for MTBE to leak into the environment (and potentially get in drinking water sources) wherever gasoline is stored, and there are opportunities for it to be spilled whenever fuel is transported or transferred.

Contamination of drinking water sources can occur from leaking underground and above

ground fuel storage tanks, pipelines, refueling spills, automobile accidents damaging the fuel tank, consumer disposal of "old" gasoline", emissions from older marine engines, and to a lesser degree, storm water runoff, and precipitation mixed with MTBE in the air.

MTBE is generally more resistant to natural biodegradation than other gasoline components. Some monitoring wells have shown little overall reduction in MTBE concentration over several years which suggests that MTBE is relatively persistent in ground water. In contrast, studies of surface water (lakes and reservoirs) have shown that MTBE volatilizes (evaporates) relatively quickly.

Effects on human health:MTBE has acute health effects such as Nausea, Dizziness and headaches.

The human health effects of long term inhalation or oral exposures to MTBE are unknown.

Cleaning of MTBE:MTBE has been banned or restricted as a gasoline additive and mainly replaced by ethanol. Because of its high solubility in water, when it escapes into the environment through gasoline releases, MTBE is capable of traveling much farther from the source of the original spill than other petroleum constituents. Also, because MTBE is poorly broken down in the soil by natural biodegradation, it can persist as a source of groundwater contamination for many years. The EPA has recommended MTBE levels in drinking water should be less than 20 to 40 parts per billion (ppb). Many states have adopted much lower levels.

Public water systems can use existing technologies such as air stripping, granular activated carbon (GAC), reverse osmosis with activated carbon block as pre-filtrations, and advanced oxidation to remove MTBE contamination. Some home treatment units can also remove MTBE in tap water.

Underground Storage Tanks (USTs) and Other Management Strategies:• EPA is working with states to increase the compliance rate with the spill, overfill, and corrosion portion of the UST regulations continue improving the quality of USTs.

• EPA is working with states on a multi-year effort to improve the compliance rate with the leak detection requirements.

• EPA and states are conducting an evaluation of UST systems performance to verify and validate how effectively leak detection and other UST systems are working; by 2002 EPA will have valuable data to decide whether the UST regulations need to be revised.

• EPA recommended that State UST/LUST officials (PDF) (4 pp, 16K, January 2000) monitor and report MTBE and other ethers in ground water at all leaking UST sites. Where MTBE is detected, states are advised to take immediate and aggressive remedial action.

• EPA and states are developing a UST system operation and maintenance manual, available in late 2000, to help UST owners and operators understand and carry out good UST management practices to better prevent and detect leaks.

“Peroxyacetyl Nitrates (PANs)”Peroxyacetyl nitrate (PAN) is a component of photochemical smog, which is a mixture of air pollutants that includes both gases and particulates, some of which react with sunlight. Acute effects — Low-levels of PAN do not have an effect on either lung capacity or respiratory rate in Humans.

The general equation is:

CxHyO3 + NO2 → CxHyO3NO2

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 derivatives are said to be mutagenic, as they can be a factor causing skin cancer.

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.

The most common peroxyacyl radical is peroxyacetyl, which can be formed from the free radical oxidation of acetaldehyde, various ketones, or the photolysis of dicarbonyl compounds such as methylglyoxal or diacetyl.

Since they dissociate quite slowly in the atmosphere into radicals and NO2, PANs are able to transport these unstable compounds far away from the urban and industrial origin. This is important for tropospheric ozone production as PANs transport NOx to regions where it can more efficiently produce ozone.

Sources:PAN is formed when sunlight energy causes non-methane hydrocarbons and nitrogen oxides to react. Acetaldehyde, methylglyoxal, and various byproducts of the oxidation of aromatic compounds are all precursors to PAN. Sources of hydrocarbons and nitrogen oxides include vehicle emissions, tobacco smoke and the burning of petroleum products, such as coal and natural gas.

peroxyacetyl nitrate, CH3COOONO2:

Hydrocarbons + O2 + NO2 + light → CH3COOONO2

Health effects: Exposure to air pollution is associated with numerous effects on human health,

including pulmonary, Cardiac, vascular and neurological impairments. The health effects vary greatly from person to person. High risk groups such as the

elderly, infants, pregnant women and sufferers from chronic heart and lung disease are more susceptible to air pollution.

Children are at greater risk because they are generally more active outdoors and their lungs are still developing.

Enzymes, phosphoglucomutase and phosphorylase are inhibited by PAN. It can inhibit the mobilization of starch in darkness due to suppression of

phosphorylase reaction. Also inhibits CO2 fixation during photosynthesis. Fatty-acids synthesis is affected by PAN due to oxidation of NADPH. It is mutagenic causes Skin cancer. Eye irritation. Respiratory problems. Toxicity summary: Acute effects — Low-levels of PAN do not have an effect on either lung capacity or

respiratory rate in humans. However, when PAN is inhaled along with ozone, as it often is in normal air, lung capacity decreases and respiratory rate increases. PAN may also cause eye irritation. Toxicity studies in rats and mice have shown that PAN may cause emphysema, impaired breathing, acute pulmonary edema or lung lesions following inhalation exposure.

Chronic effects — No studies were found on the effects of chronic PAN exposure in humans. However, rats exposed to PAN for 13 weeks demonstrated signs of abnormal behavior, increased lung weights, weight loss, depressed growth, respiratory irritation and mortality.

Genotoxicity and mutagenicity — PAN has been determined to be a weak point mutagen and a clastogen. Although positive results have been observed in various bacterial mutagenicity assays both in the presence and absence of metabolic activation negative results have been observed in animal studies.

References:

http://www.conserve-energy-future.com/SmogPollution.php https://www.sciencedaily.com/terms/smog.htm https://en.wikipedia.org/wiki/Peroxyacetyl_nitrate https://en.wikipedia.org/wiki/Methyl_tert-butyl_ether https://www.google.com.pk/search?

q=mtbe&safe=active&rlz=1C1RUCY_enPK692PK692&biw=1366&bih=643&source=lnms&tbm=isch&sa=X&ved=0ahUKEwie-4OMoJ3NAhUMnRQKHei7AjcQ_AUIBigB

http://www.deq.louisiana.gov/portal/PROGRAMS/OzoneActionProgram/ OzoneFactsandExperiments/WhatisSmog.aspx

http://sd.water.usgs.gov/nawqa/vocns/mtbe_hh_summary.html